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Dengue fever is a viral mosquito-borne disease, a significant global health concern, with more than one third of the world population at risk of acquiring the disease. Caused by 4 antigenically distinct but related virus serotypes, named DENV-1, DENV-2, DENV-3, and DENV-4, infection by one serotype confers lifelong immunity to that serotype and a short period of temporary cross immunity to other related serotypes. Severe dengue is epidemiologically associated with a secondary infection caused by a heterologous serotype via the so-called antibody-dependent enhancement (ADE), an immunological process enhancing a new infection. Within-host dengue modeling is restricted to a small number of studies so far. With many open questions, the understanding of immunopathogenesis of severe disease during recurrent infections is important to evaluate the impact of newly licensed vaccines. In this paper, we revisit the modeling framework proposed by Sebayang et al. and perform a detailed sensitivity analysis of the well-known biological parameters and its possible combinations to understand the existing data sets. Using numerical simulations, we investigate features of viral replication, antibody production, and infection clearance over time for three possible scenarios: primary infection, secondary infection caused by homologous serotype, and secondary infection caused by heterologous serotype. Besides, describing well the infection dynamics as reported in the immunology literature, our results provide information on parameter combinations to best describe the differences on the immunological dynamics of secondary infections with homologous and heterologous viruses. The results presented here will be used as baseline to investigate a more complex within-host dengue model. [ABSTRACT FROM AUTHOR]

It has previously been shown that rats do not expel a primary infection of Nippostronglus brasiliensis during lactation. In the present paper, three aspects of the immune response of the lactating rat to the parasite were examined and compared with the response of non-lactating rats. Protective and reaginic antibodies were present in the circulation of rats first infected during lactation, in titres as high or higher than those in non-lactating controls. The intestinal mast cell response was similar both in timing and magnitude and lactating rats became susceptible to shock with the i.v. injection of antigen. Attention was drawn to the similarity between the response of the lactating rat and that of the neonate to this infection. [ABSTRACT FROM AUTHOR]

For rapid screening and quantification of an antisera antibody, a nanometer bithiophene-based conductive biolinker can enhanced signal performance and can be used to verify the interaction of an anti-IFN-γ antibody with an IFN-γ protein. The experimental measurements take a generic approach which takes advantage of the functionality of thiophene-based linkers for biosensors. Effects associated with using bithiophene as a biolinker for surface plasmon resonance (SPR) spectroscopy are examined in this paper. By using an atomic force microscope (AFM), it was observed that the morphology of the bithiophene modified gold sensor surface became smoother than the original gold surface. We compared the response and concentration of the anti-IFN-γ antibody on a bithiophene-coated and dextran-coated biochip as well as on different thickness-modified surfaces under SPR relevant conditions. The results indicate that a response to IFN-γ molecules immobilized on a sensor using a bithiophene biolinker improved more than 8-fold when compared to that of a sensor using a dextran biolinker. Furthermore, the regeneration ability of the sensor surface shows good repeatability as only less than a 1% decrease was found after repeating the experimental work over 6 cycles. The characteristics provided us with a good platform for rapid screening, real-time monitoring and quantitative concentration of the autoimmune antibody activities. [ABSTRACT FROM AUTHOR]

Many approaches have been designed to extract brain effective connectivity from functional magnetic resonance imaging (fMRI) data. However, few of them can effectively identify the connectivity network structure due to different defects. In this paper, a new algorithm is developed to infer the effective connectivity between different brain regions by combining artificial immune algorithm (AIA) with the Bayes net method, named as AIAEC. In the proposed algorithm, a brain effective connectivity network is mapped onto an antibody, and four immune operators are employed to perform the optimization process of antibodies, including clonal selection operator, crossover operator, mutation operator and suppression operator, and finally gets an antibody with the highest K2 score as the solution. AIAEC is then tested on Smith’s simulated datasets, and the effect of the different factors on AIAEC is evaluated, including the node number, session length, as well as the other potential confounding factors of the blood oxygen level dependent (BOLD) signal. It was revealed that, as contrast to other existing methods, AIAEC got the best performance on the majority of the datasets. It was also found that AIAEC could attain a relative better solution under the influence of many factors, although AIAEC was differently affected by the aforementioned factors. AIAEC is thus demonstrated to be an effective method for detecting the brain effective connectivity. [ABSTRACT FROM AUTHOR]

Enhancement or inhibition of cytokine signaling and corresponding immune cells responses are critical factors in various disease treatments. Cytokine signaling may be inhibited by cytokine-neutralizing antibodies (CNAs), which prevents further activation of cytokine receptors. However, CNAs may result in enhanced—instead of inhibitory—cytokine signaling (an “agonistic effect”) in various in vitro and in vivo experiments. This may lead to lack of efficacy or adverse events for cytokine-inhibiting based medicines. Alternatively, cytokine-antibody complexes may produce stronger signaling vs. cytokine alone, thereby increasing the efficacy of stimulating cytokine-based drugs, at equal or lower cytokine doses. In this paper, the effect of cytokine signaling enhancement by a CNA was studied in a generic mathematical model of interleukin-4 (IL-4) driven T-cell proliferation. The occurrence of the agonistic effect depends upon the antibody-to-cytokine binding affinity and initial concentrations of antibody and cytokine. Model predictions were in agreement with experimental studies. When the cytokine receptor consists of multiple subunits with substantially differing affinities (e.g., IL-4 case), the choice of the receptor chain to be blocked by the antibody is critical, for the agonistic effect to appear. We propose a generic mechanism for the effect: initially, binding of the CNA to the cytokine reduces free cytokine concentration; yet, cytokine molecules bound within the cytokine-CNA complex—and released later and over time—are “rescued” from earlier clearance via cellular internalization. Hence, although free cytokine-dependent signalling may be less potent initially, it will also be more sustained over time; and given non-linear dynamics, it will lead ultimately to larger cellular effector responses, vs. the same amount of free cytokine in the absence of CNA. We suggest that the proposed mechanism is a generic property of {cytokine, CNA, receptor} triads, both in vitro and in vivo, and can occur in a predictable fashion for a variety of cytokines of the immune system. [ABSTRACT FROM AUTHOR]

There is increasing interest in multi-allele vaccines to overcome strain-specificity against polymorphic vaccine targets such as Apical Membrane Antigen 1 (AMA1). These have been shown to induce broad inhibitory antibodies in vitro and formed the basis for the design of three Diversity-Covering (DiCo) proteins with similar immunological effects. The antibodies produced are to epitopes that are shared between vaccine alleles and theoretically, increasing the number of component AMA1 alleles is expected to broaden the antibody response. A plateau effect could however impose a limit on the number of alleles needed to achieve the broadest specificity. Moreover, production cost and the vaccine formulation process would limit the number of component alleles. In this paper, we compare rabbit antibody responses elicited with multi-allele vaccines incorporating seven (three DiCos and four natural AMA1 alleles) and three (DiCo mix) antigens for gains in broadened specificity. We also investigate the effect of three adjuvant platforms on antigen specificity and antibody functionality. Our data confirms a broadened response after immunisation with DiCo mix in all three adjuvants. Higher antibody titres were elicited with either CoVaccine HTTM or Montanide ISA 51, resulting in similar in vitro inhibition (65-82%) of five out of six culture-adapted P. falciparum strains. The antigen binding specificities of elicited antibodies were also similar and independent of the adjuvant used or the number of vaccine component alleles. Thus neither the four extra antigens nor adjuvant had any observable benefits with respect to specificity broadening, although adjuvant choice influenced the absolute antibody levels and thus the extent of parasite inhibition. Our data confirms the feasibility and potential of multi-allele PfAMA1 formulations, and highlights the need for adjuvants with improved antibody potentiation properties for AMA1-based vaccines. [ABSTRACT FROM AUTHOR]

As perhaps the staunchest advocates of repertoire purging as the central mechanism of immunological tolerance, we note with satisfaction a spate of recent, elegant papers which suggest an intrathymic clonal abortion model as the explanation for at least some examples of T-cell tolerance. This view agrees with the classical formulation of the Billingham-Brent-Medawar school of tolerance as a specific, central failure of immune responsiveness. Repertoire purging within the B-lymphocyte compartment remains much more controversial. There is no doubt that experimental models exist where the B cell is the reversible target of tolerance induction. The question is, in view of the ease of inducing autoantibody formation both in vivo and in vitro, just how relevant are such clonal anergy mechanisms to authentic self-tolerance? Arguments are presented that there must be two windows of tolerance susceptibility in the ontogeny of the B cell; one while it is maturing in the bone marrow, to prevent autoreactivity of high affinity to important accessible self-antigens; and a second soon after activation of pre-memory cells by exogenous antigen, to prevent fortuitous mutations towards high-affinity anti-self-reactivity establishing a forbidden clone. [ABSTRACT FROM AUTHOR]

The experiments described in this paper were designed to determine the degradation of soluble IgG aggregates (AIgG) bearing C3b by guinea-pig peritoneal macrophages with different numbers of functional C3b receptors. The number of functional Fc receptors for AIgG containing 40 molecules of IgG per aggregate (AIgG40) were kept constant during these experiments. By increasing the concentration of trypsin for the treatment of normal peritoneal macrophages a dose-dependent inactivation of C3b receptors was achieved as determined by the binding of tetrameric [125I]-C3b([125I]-AC3b). Normal peritoneal macrophages bound 148,500 AIgG40 and 60,300 AC3b per cell. Treatment of the macrophages for 15 rain at 37° with incremental amounts of trypsin from 60 to 1000 µg/ml did not affect the binding of AIgG40 to macrophages but caused a dose-related loss of up to 95% of AC3b binding, indicating functional inactivation of C3b receptors. Degradation of trichloroacetic acid non-precipitable protein of [125I]-AIgG40 by 106 macrophages was 38±6% in medium alone and 60 ±8% in the presence of 10% fresh guinea-pig serum (NGPS) after 60 rain at 37°. The inactivation of 25%, 50%, 72% and 94% of C3b receptors by trypsin did not affect the degradation of AIgG40 in medium alone, but decreased degradation from 69% to 58%, 47%, 32% and 13% of AIgG40 respectively, in the presence of 10% GPS. Macrophages (106) in medium alone degraded 40%, 47%, 65% and 68% of AIgG40 beating 0, 5, 10, 16 and 20 C3b molecules per aggregate, indicating a dose-dependent enhancement of degradation by bound C3b; conversely, inactivation of 95% of C3 receptor on the macrophages resulted in 39%, 30%, 12%, 5% and 6% degradation of these AIgG40-C3b, indicating a dose-related inhibition by aggregate-bound C3b in the absence of cellular C3 receptor. These experiments stress the importance of Fc and C3b receptor co-operation and immune complex bound C3b. [ABSTRACT FROM AUTHOR]

Plaque-forming cell responses and antibody titres to sheep red cells (SRC) were elevated in normally-fed irradiated adult mice reconstituted with spleen cells from young mice which had received a 4% albumin diet, compared with those given cells from normally-fed littermates. This was independent of the dose of cells transferred (5 × 106-4 × 107), the day of assay (3–10) and the duration of protein-deficiency (1 or 3 weeks). It suggests that the depressed responses produced by protein-deficient (donor) mice reported in earlier papers resulted from an impairment of reticuloendothelial function or a shortage of protein reserves, not directly associated with the spleen. As protein-deficiency (of the donor) accelerated the initiation of the adoptive response and increased the cell yields of the recipients it is considered likely that an enhancement of cell proliferation during the first 3-5 days after transfer was responsible for the elevated responses. [ABSTRACT FROM AUTHOR]

This paper describes the induction of immunosuppression by multiple injections of carrageenan-lambda (cgn) in BALB/c mice. While cgn alone induced non-specific suppression that persisted for up to 25 days, priming with sheep red blood cells (SRBC) of mice within l0 days of cgn treatment prolonged the suppressive state. Also, antigen (SRBC)-specific suppression was observed when these mice were siren a secondary challenge 25–30 days after priming. Thus multiple cgn treatment along with priming SRBC generated non-specific and specific suppressive states which were transferable by Thy-l+ Lyt-2+ splenocytes. [ABSTRACT FROM AUTHOR]

Red cells sensitized with naturally occurring or 'immune' fowl antibody were lysed by fresh fowl serum. This fowl complement could not be replaced by that of human, rabbit or guinea pig. Both naturally occurring and 'immune' antibodies to red cells in the mammalian species tested did not lyse with fowl complement. Lysis by fresh fowl serum of sheep red cells sensitized with mammalian antibody is due to the presence of naturally occurrent antibody to these cells in the fowl serum; the enhancement of this lysis by the mammalian antibody will be described more fully in the next paper. Naturally occurring antibody to sheep red cells present in turkey serum and 'immune' antibody to fowl red cells were not lytic with fresh turkey serum, with fowl complement, with guinea-pig complement or with any combination of these. Some properties of fowl complement are given. [ABSTRACT FROM AUTHOR]

The development of donor‐specific antibodies (DSAs) is a major complication in transplantation, which is associated with inferior graft survival, impaired quality of life, and increased healthcare costs. DSA develop upon recognition of nonself HLA by the recipient's immune system. HLA molecules contain epitopes, which are the surface regions of HLA molecules recognized by antibodies. HLAMatchmaker is an algorithm for assessing donor:recipient HLA compatibility at the level of structurally defined HLA targets called eplets. The consideration of eplets, rather than the whole HLA molecule, could offer some advantages when classifying the immune risk associated with particular donor:recipient pairs. Assessing compatibility at the level of HLA eplets could decrease misclassification of post‐transplant immune risk by improving specificity, when antibodies are confirmed to be directed against donor eplets missing from the recipient's repertoire of eplets. Consideration of eplets may also increase the sensitivity of immune risk assessment, when identifying mismatched eplets that could give rise to new, not previously detected, donor‐specific antibodies post‐transplant. Eplet matching can serve as a rational strategy for immune risk mitigation. Herein, we review the evolution of HLA (in) compatibility assessment for organ allocation. We outline challenges in the implementation of eplet‐based donor:recipient matching, including unavailability of allele‐level donor genotypes for 11 HLA loci at the time of organ allocation and difficulty in assessing the hierarchy of immune risk associated with particular HLA eplet mismatches. Opportunities to address some of the current shortcomings of donor genotyping and HLAMatchmaker are also discussed. While there is a demonstrated benefit in the application of HLAMatchmaker for donor: recipient HLA (in)compatibility assessment, evolving long‐read genotyping methods, compilation of large data sets with allele‐level genotypes, and standardization of methods to verify eplets as determinants of immune‐mediated injuries are required before HLA eplet matching is implemented in organ allocation to improve upon transplant outcomes. [ABSTRACT FROM AUTHOR]

HLA donor‐specific antibodies developed de novo after transplant remain a major cause of chronic allograft dysfunction. Our study main purpose was to determine whether HLA MM, assessed traditionally and by HLA total and AbVer eplet mismatch load (EptMM and EpvMM) assessed with HLAMatchMaker, had impact on dnDSA development after living donor kidney transplantation (LDKT). We retrospectively analysed a cohort of 96 LDKT between 2008 and 2017 performed in Hospital Santo António. Seven patients developed dnDSA‐II and EpvMM and EptMM were greater in dnDSA‐II group compared to the no dnDSA‐II (18.0 ± 8.7 versus 9.9 ± 7.9, p =.041 and 41.3 ± 18.9 versus 23.1 ± 16.7, p =.018), which is not observed for AgMM (2.29 versus 1.56; p =.09). In a multivariate analysis, we found that preformed DSA (HR = 7.983; p =.023), living unrelated donors (HR = 8.052; p =.024) and retransplantation (HR = 14.393; p =.009) were predictors for dnDSA‐II (AUC = 0.801; 0.622–0.981). HLA‐II EpvMM (HR = 1.105; p =.028; AUC = 0.856) showed to be a superior predictor of dnDSA‐II, when compared to AgMM (HR = 1.740; p =.113; AUC = 0.783), when adjusted for these clinical variables. Graft survival was significantly lower within dnDSA‐II patient group (36% versus 88%, p <.001). HLA molecular mismatch analysis is extremely important to minimize risk for HLA‐II dnDSA development improving outcome and increasing chance of retransplant lowering allosensitization. [ABSTRACT FROM AUTHOR]

A theoretical framework is presented which explores two models of suppressor cell-target cell interactions in T-dependent antibody responses. The first is the full-dominance model, in which a single or limited number of suppressor cells can entirely suppress an immune response irrespective of the multiplicity of other effector cells present. The second is the ratio-dominance model, in which a suppressor cell is capable of inactivating only a certain number of target cells. Thus, the multiplicity of target cells in a given microculture well influences the degree of suppression. Both models are evaluated using limiting dilution analysis and two systems are explored, in the first model, suppressor cells alone are titrated into microculture wells containing all other cells required for an immune response. In the second, suppressor cells are added from populations containing a mixture of helper T cells as well as suppressor cells. This latter type of analysis is similar to that in which populations of T cells primed to alloantigens in mixed lymphocyte cultures are analysed for positive (help) and negative (suppression) allogeneic effects. The analysis allows us to conclude that such suppressor cells operate via a mechanism best described by a ratio-dominance model. [ABSTRACT FROM AUTHOR]

Two methods are described for linking chlorambucil to antibodies. At low pH an association is formed which is not stable under physiological conditions and the cytotoxicity is the result of the independent action of chlorambucil and antibody. At pH 8 a more stable linkage is formed and this complex shows specific toxicity for cells carrying the appropriate antigen. Uncombined chlorambucil and antibody are more cytotoxic than chlorambucil alone, especially if the cells are exposed first to the chlorambucil. [ABSTRACT FROM AUTHOR]

Rabbits made immunologically unresponsive by neonatal administration of HSA, HGG or BSA were given a course of intravenous injections of the respective antigens, adsorbed on alum, after a lapse of 13-27 months since the last administration of antigen. 8/12 responded to HSA, 4/5 to HGG, 9/10 to BSA, as judged by immune elimination of antigen, but this was delayed in onset and slow compared with that in previously untreated rabbits. The antibody formed was small in quantity and usually failed to precipitate with antigen. The sedimentation coefficients of 131I-labelled antigens, in the presence of excess antibody, were measured by ultracentrifugation through a sucrose density gradient. These showed that only small complexes were formed in some of the non-precipitating antisera. In one instance the diffusion coefficient of the complex was also measured, by a technique based on diffusion through agar gel. The calculated molecular weight of the complex, 330,000 indicated the presence of only two combining sites on the antigen. Combination of the anti-HSA sera with an HSA fragment was also measured. Whereas the amount of the fragment bound by ordinary hyperimmune anti-HSA sera was about one-fifth the HSA bound, the amounts bound by the test sera were relatively much less. Some non-precipitating sera failed to bind the fragment, although they bound HSA. These findings indicate that following neonatally induced immunological unresponsiveness the capacity to respond to antigen returns piecemeal in respect of different parts of the antigenic mosaic, and that it may be severely restricted. The theoretical implications are discussed. [ABSTRACT FROM AUTHOR]

The immunological responses of rabbits to HSA, HGG or BSA were tested at various times later in animals which had received the corresponding antigens before or shortly after birth. As judged by the criterion of failure to show immune elimination of antigen, a high proportion of the rabbits remained unresponsive at times when it was calculated that all the originally administered antigen would have been eliminated from the circulation. Furthermore, removal of antigen by passively administered antibody failed to restore the capacity to respond. It is concluded that, in respect of the antigens used, their persistence in the extracellular body fluids is not a prerequisite for maintenance of immunological unresponsiveness.
Further administration of the same antigen to rabbits which had escaped from a state of specific immunological unresponsiveness generally produced a very weak response, and in a few instances resulted in a return to the unresponsive state.
When the cross-reacting antigens HSA and BSA were administered adsorbed on alum to rabbits made unresponsive by neonatal contact with BSA and HSA respectively, and at the same time a further dose of the original antigen was given, antibodies were formed which were specific for the second antigen and did not cross-react with the first. In only 1/9 animals was responsiveness to the first antigen restored. The significance of these results is discussed. [ABSTRACT FROM AUTHOR]

Cold agglutinins were separated from the sera of eleven patients suffering from the cold-antibody type of acquired haemolytic anaemia by the dissociation of the specific antigen-antibody complexes. The electrophoretic mobility of the cold antibody was found to correspond to that of γl globulin in each case. Ultracentrifugal studies carried out on eluted cold antibodies prepared from the sera of seven patients demonstrated that the antibodies were macromolecules (S20,w∼18.1). In one instance the sedimentation coefficient of the cold antibody was demonstrated to be similar to that of electrophoretically separated ‘γ1 globulin’ prepared from the same serum, indicating their identical physical state. The results of treating the sera of nineteen patients with the cold-antibody type of acquired haemolytic anaemia with mercapto-ethanol further confirmed that the cold antibodies were all macromolecules, whether derived from idiopathic cases or cases secondary to some other known disorder. [ABSTRACT FROM AUTHOR]

Cold antibodies were separated from the sera of six patients suffering from the cold-haemagglutinin syndrome and from one patient with acquired haemolytic anaemia secondayr to lymphosarcoma by dissociation of the specific antigen-antibody complexes. The eluted antibodies were studied (a) by immuno-electrophoresis along with the parent sera against horse anti-human serum and (b) by double diffusion in agar gel along with electrophoretically separated ‘γ1 globulin’† against anti-19S ‘γ-globulin’ rabbit sera. The protein forming the cold antibody was localized in the β2-M position on immuno-electrophoresis in each instance. It was found by double diffusion in agar gel to be immunologically identical with the protein forming the abnormal ‘γl-globulin’ electrophoretic peak in the parent serum. The results of these experiments indicate that the cold antibodies derived from patients with the cold-antibody type of acquired haemolytic anaemia are macro-molecular globulins. [ABSTRACT FROM AUTHOR]

A critical review is given of Goldberg's (1952, 1953) theory of Antigen-Antibody reactions in vitro. Goldberg's assumptions and the mathematical development of his theory are described in detail. Comparisons of Goldberg's predictions with experimental results are given in graphical form. Some criticisms are made of Goldberg's use of equations in regions in which the derivations given by him are not valid. [ABSTRACT FROM AUTHOR]

The immunological response of the primitive mammal Tachyglossus aculeatus has been studied. We have shown that this animal responds to flagella from Salmonella adelaide with production of mercaptoethanol-resistant antibodies during both primary and secondary responses. Although an anamnestic secondary response could be demonstrated, it was of much smaller magnitude than that of phylogenetically higher placental mammals. Serological investigations demon- strated the presence of a mercaptoethanol-sensitive antibody of high molecular weight and an antibody of lower molecular weight which was mercaptoethanol resistant. These two antibodies seem to be analogous to IgM and IgG antibodies of higher mammals. [ABSTRACT FROM AUTHOR]

Human cytomegalovirus (HCMV) causes substantial disease in transplant patients and harms the development of the nervous system in babies infected in utero. Thus, there is a major focus on developing safe and effective HCMV vaccines. Evidence has been presented that a major target of neutralizing antibodies (NAbs) is the HCMV pentamer glycoprotein gH/gL/UL128-131. In some studies, most of the NAbs in animal or human sera were found to recognize the pentamer, which mediates HCMV entry into endothelial and epithelial cells. It was also reported that pentamer-specific antibodies correlate with protection against transmission from mothers to babies. One problem with the studies on pentamer-specific NAbs to date has been that the studies did not compare the pentamer to the other major form of gH/gL, the gH/gL/gO trimer, which is essential for entry into all cell types. Here, we demonstrate that both trimer and pentamer NAbs are frequently found in human transplant patients' and pregnant mothers' sera. Depletion of human sera with trimer caused reductions in NAbs similar to that observed following depletion with the pentamer. The trimer- and pentamer-specific antibodies acted in a synergistic fashion to neutralize HCMV and also to prevent virus cell-to-cell spread. Importantly, there was no correlation between the titers of trimer- and pentamer-specific NAbs and transmission of HCMV from mothers to babies. Therefore, both the trimer and pentamer are important targets of NAbs. Nevertheless, these antibodies do not protect against transmission of HCMV from mothers to babies. [ABSTRACT FROM AUTHOR]

Summary: Meningococcal polysaccharide (Men‐Ps) vaccine immunogenicity following either primary immunization or revaccination in adults was evaluated. The study population consisted of subjects who have received tetravalent Men‐Ps vaccine once (group 1) or at least twice, with a 2–6 dose range (group 2). Human leucocyte antigen (HLA)‐typing was performed by polymerase chain reaction and specific immunoglobulin (Ig)G was measured by enzyme‐linked immunosorbent assay. Nine months post‐immunization, the percentages of individuals with levels of anti‐Men‐Ps IgG ≥ 2 µg/ml were comparable in both groups, with the exception of anti‐Men‐PsW135 IgG, which were significantly higher in group 2. The percentage of subjects doubling IgG levels at 9 months was significantly higher in group 1. The high baseline anti‐Men‐Ps antibody levels negatively influenced the response to revaccination, suggesting a feedback control of specific IgG. The calculated durability of anti‐Men‐Ps IgG was 2·5–4·5 years, depending on the Men‐Ps, following a single vaccine dose. No interference by other vaccinations nor HLA alleles association with immune response were observed. This study confirms that Men‐Ps vaccine in adults is immunogenic, even when administered repeatedly, and underlines the vaccine suitability for large‐scale adult immunization programmes that the higher costs of conjugate vaccines may limit in developing countries. Meningococcal polysaccharide (Men‐Ps) vaccine immunogenicity following either primary immunization or revaccination was evaluated in adult subjects who have received tetravalent Men‐Ps vaccine once (group 1) or at least twice, with a 2–6 dose range (group 2). Nine months post‐immunization, the percentages of individuals with levels of anti‐Men‐Ps immunoglobulin (Ig)G ≥ 2 µg/ml were comparable in both groups, with the exception of anti‐Men‐PsW135 IgG, which were significantly higher in individuals receiving booster doses. This study confirms that Men‐Ps vaccine in adults is immunogenic, even when repeatedly administered, and underlines the vaccine suitability for large‐scale adult immunization programmes that the higher costs of conjugate vaccines may limit in developing countries. [ABSTRACT FROM AUTHOR]

Objective: In some Pacific Island countries, such as Solomon Islands and Fiji, active trachoma is common, but ocular Chlamydia trachomatis (Ct) infection and trachomatous trichiasis (TT) are rare. On Tarawa, the most populous Kiribati island, both the active trachoma sign “trachomatous inflammation—follicular” (TF) and TT are present at prevalences warranting intervention. We sought to estimate prevalences of TF, TT, ocular Ct infection, and anti-Ct antibodies on Kiritimati Island, Kiribati, to assess local relationships between these parameters, and to help determine the need for interventions against trachoma on Kiribati islands other than Tarawa. Methods: As part of the Global Trachoma Mapping Project (GTMP), on Kiritimati, we examined 406 children aged 1–9 years for active trachoma. We collected conjunctival swabs (for droplet digital PCR against Ct plasmid targets) from 1–9-year-olds with active trachoma, and a systematic selection of 1–9-year-olds without active trachoma. We collected dried blood spots (for anti-Pgp3 ELISA) from all 1–9-year-old children. We also examined 416 adults aged ≥15 years for TT. Prevalence of TF and TT was adjusted for age (TF) or age and gender (TT) in five-year age bands. Results: The age-adjusted prevalence of TF in 1–9-year-olds was 28% (95% confidence interval [CI]: 24–35). The age- and gender-adjusted prevalence of TT in those aged ≥15 years was 0.2% (95% CI: 0.1–0.3%). Twenty-six (13.5%) of 193 swabs from children without active trachoma, and 58 (49.2%) of 118 swabs from children with active trachoma were positive for Ct DNA. Two hundred and ten (53%) of 397 children had anti-Pgp3 antibodies. Both infection (p<0.0001) and seropositivity (p<0.0001) were strongly associated with active trachoma. In 1–9-year-olds, the prevalence of anti-Pgp3 antibodies rose steeply with age. Conclusion: Trachoma presents a public health problem on Kiritimati, where the high prevalence of ocular Ct infection and rapid increase in seropositivity with age suggest intense Ct transmission amongst young children. Interventions are required here to prevent future blindness. [ABSTRACT FROM AUTHOR]

Objective: To analyse the relationship between rheumatoid factor (RF) titre, smoking and HLA-DRB1 alleles coding a “shared epitope” (SE) in relation to anti-citrullinated protein antibody (ACPA) positivity in rheumatoid arthritis (RA). Methods: RA patients (n = 658) attending rheumatology clinics in Cornwall, UK (cohort 1) were stratified according to RF and ACPA titre, and smoking pack years at diagnosis. A further 409 RA patients from North Staffordshire, UK (cohort 2) were studied to confirm the relationship between RF levels, smoking and ACPA positivity in relation to SE status. Results: In cohort 1 there was a trend (p<0.01) of increasing ACPA positivity rates with increasing levels of RF without statistically significant differences between patients who had never smoked and smokers (never smoked: 15/71 (21%) RF -ve, vs. 43/64 (67%) RF weak +ve, vs 88/100 (88%) RF strong +ve, ever smoked: 18/70 (26%) RF -ve vs. 66/83 (80%) RF weak +ve vs. 196/210 (93%) RF strong +ve). No significant gender difference was observed. No significant difference between smoking and ACPA positivity was seen in RF negative patients. Smoking >20 pack years conferred an increased risk of anti-CCP positive RA (158/200 (79%)), compared to having never smoked (146/235 (62%), p = <0.01), but this increased risk correlated with smokers’ RF positivity as the principal determinant on subsequent regression analysis of cohort 2. In cohort 2, ACPA positivity rates significantly increased with RF positivity and carriage of 1 or 2 SE alleles (p<0.01). Little or no relationship was observed in patients lacking SE. Conclusions: ACPA positivity in RA strongly associates with increasing RF titre independent of smoking. This relationship is dependent on carriage of SE alleles. There is no relationship between ACPA and smoking in RF negative patients. [ABSTRACT FROM AUTHOR]

Many biopharmaceuticals (BPs) are known to be immunogenic in the clinic, which can result in modified pharmacokinetics, reduced efficacy, allergic reactions and anaphylaxis. During recent years, several technologies to predict immunogenicity have been introduced, but the predictive value is still considered low. Thus, there is an unmet medical need for optimization of such technologies. The generation of T cell dependent high affinity anti-drug antibodies plays a key role in clinical immunogenicity. This study aimed at developing and evaluating a novel in vitro T cell:PBMC assay for prediction of the immunogenicity potential of BPs. To this end, we assessed the ability of infliximab (anti-TNF-α), rituximab (anti-CD20), adalimumab (anti-TNF-α) and natalizumab (anti-α4-integrin), all showing immunogenicity in the clinic, to induce a CD4+ T cells response. Keyhole limpet hemocyanin (KLH) and cytomegalovirus pp65 protein (CMV) were included as neo-antigen and recall antigen positive controls, respectively. By analyzing 26 healthy donors having HLA-DRB1 alleles matching the European population, we calculated the frequency of responding donors, the magnitude of the response, and the frequency of BP-specific T cells, as measured by 3[H]-thymidine incorporation and ELISpot IL-2 secretion. KLH and CMV demonstrated a strong T cell response in all the donors analyzed. The frequency of responding donors to the BPs was 4% for infliximab, 8% for adalimumab, 19% for rituximab and 27% for natalizumab, which is compared to and discussed with their respective observed clinical immunogenicity. This study further complements predictive immunogenicity testing by quantifying the in vitro CD4+ T cell responses to different BPs. Even though the data generated using this modified method does not directly translate to the clinical situation, a high sensitivity and immunogenic potential of most BPs is demonstrated. [ABSTRACT FROM AUTHOR]

Characterizing the immune response to pneumococcal proteins is critical in understanding this bacterium's epidemiology and vaccinology. Probing a custom-designed proteome microarray with sera from 35 healthy US adults revealed a continuous distribution of IgG affinities for 2,190 potential antigens from the species-wide pangenome. Reproducibly elevated IgG binding was elicited by 208 "antibody binding targets" (ABTs), which included 109 variants of the diverse pneumococcal surface proteins A and C (PspA and PspC) and zinc metalloprotease A and B (ZmpA and ZmpB) proteins. Functional analysis found ABTs were enriched inmotifs for secretion and cell surface association, with extensive representation of cell wall synthesis machinery, adhesins, transporter solute-binding proteins, and degradative enzymes. ABTs were associated with stronger evidence for evolving under positive selection, although this varied between functional categories, as did rates of diversification through recombination. Particularly rapid variation was observed at some immunogenic accessory loci, including a phage protein and a phase-variable glycosyltransferase ubiquitous among the diverse set of genomic islands encoding the serine-rich PsrP glycoprotein. Nevertheless, many antigens were conserved in the core genome, and strains' antigenic profiles were generally stable. No strong evidence was found for any epistasis between antigens driving population dynamics, or redundancy between functionally similar accessory ABTs, or age stratification of antigen profiles. These results highlight the paradox of why substantial variation is observed in only a subset of epitopes. This result may indicate only some interactions between immunoglobulins and ABTs clear pneumococcal colonization or that acquired immunity to pneumococci is an accumulation of individually weak responses to ABTs evolving under different levels of functional constraint. [ABSTRACT FROM AUTHOR]

Computational neutralization fingerprinting, NFP, is an efficient and accurate method for predicting the epitope specificities of polyclonal antibody responses to HIV-1 infection. Here, we present next-generation NFP algorithms that substantially improve prediction accuracy for individual donors and enable serologic analysis for entire cohorts. Specifically, we developed algorithms for: (a) selection of optimized virus neutralization panels for NFP analysis, (b) estimation of NFP prediction confidence for each serum sample, and (c) identification of sera with potentially novel epitope specificities. At the individual donor level, the next-generation NFP algorithms particularly improved the ability to detect multiple epitope specificities in a sample, as confirmed both for computationally simulated polyclonal sera and for samples from HIV-infected donors. Specifically, the next-generation NFP algorithms detected multiple specificities in twice as many samples of simulated sera. Further, unlike the first-generation NFP, the new algorithms were able to detect both of the previously confirmed antibody specificities, VRC01-like and PG9-like, in donor CHAVI 0219. At the cohort level, analysis of ~150 broadly neutralizing HIV-infected donor samples suggested a potential connection between clade of infection and types of elicited epitope specificities. Most notably, while 10E8-like antibodies were observed in infections from different clades, an enrichment of such antibodies was predicted for clade B samples. Ultimately, such large-scale analyses of antibody responses to HIV-1 infection can help guide the design of epitope-specific vaccines that are tailored to take into account the prevalence of infecting clades within a specific geographic region. Overall, the next-generation NFP technology will be an important tool for the analysis of broadly neutralizing polyclonal antibody responses against HIV-1. [ABSTRACT FROM AUTHOR]

Background: The human malaria parasite Plasmodium vivax infects red blood cells through a key pathway that requires interaction between Duffy binding protein II (DBPII) and its receptor on reticulocytes, the Duffy antigen/receptor for chemokines (DARC). A high proportion of P. vivax-exposed individuals fail to develop antibodies that inhibit DBPII-DARC interaction, and genetic factors that modulate this humoral immune response are poorly characterized. Here, we investigate if DBPII responsiveness could be HLA class II-linked. Methodology/Principal Findings: A community-based open cohort study was carried out in an agricultural settlement of the Brazilian Amazon, in which 336 unrelated volunteers were genotyped for HLA class II (DRB1, DQA1 and DQB1 loci), and their DBPII immune responses were monitored over time (baseline, 6 and 12 months) by conventional serology (DBPII IgG ELISA-detected) and functional assays (inhibition of DBPII–erythrocyte binding). The results demonstrated an increased susceptibility of the DRB1*13:01 carriers to develop and sustain an anti-DBPII IgG response, while individuals with the haplotype DRB1*14:02-DQA1*05:03-DQB1*03:01 were persistent non-responders. HLA class II gene polymorphisms also influenced the functional properties of DBPII antibodies (BIAbs, binding inhibitory antibodies), with three alleles (DRB1*07:01, DQA1*02:01 and DQB1*02:02) comprising a single haplotype linked with the presence and persistence of the BIAbs response. Modelling the structural effects of the HLA-DRB1 variants revealed a number of differences in the peptide-binding groove, which is likely to lead to altered antigen binding and presentation profiles, and hence may explain the differences in subject responses. Conclusions/Significance: The current study confirms the heritability of the DBPII antibody response, with genetic variation in HLA class II genes influencing both the development and persistence of IgG antibody responses. Cellular studies to increase knowledge of the binding affinities of DBPII peptides for class II molecules linked with good or poor antibody responses might lead to the development of strategies for controlling the type of helper T cells activated in response to DBPII. [ABSTRACT FROM AUTHOR]

P. vivax infection during pregnancy has been associated with poor outcomes such as anemia, low birth weight and congenital malaria, thus representing an important global health problem. However, no vaccine is currently available for its prevention. Vir genes were the first putative virulent factors associated with P. vivax infections, yet very few studies have examined their potential role as targets of immunity. We investigated the immunogenic properties of five VIR proteins and two long synthetic peptides containing conserved VIR sequences (PvLP1 and PvLP2) in the context of the PregVax cohort study including women from five malaria endemic countries: Brazil, Colombia, Guatemala, India and Papua New Guinea (PNG) at different timepoints during and after pregnancy. Antibody responses against all antigens were detected in all populations, with PNG women presenting the highest levels overall. P. vivax infection at sample collection time was positively associated with antibody levels against PvLP1 (fold-increase: 1.60 at recruitment -first antenatal visit-) and PvLP2 (fold-increase: 1.63 at delivery), and P. falciparum co-infection was found to increase those responses (for PvLP1 at recruitment, fold-increase: 2.25). Levels of IgG against two VIR proteins at delivery were associated with higher birth weight (27 g increase per duplicating antibody levels, p<0.05). Peripheral blood mononuclear cells from PNG uninfected pregnant women had significantly higher antigen-specific IFN-γ TH1 responses (p=0.006) and secreted less pro-inflammatory cytokines TNF and IL-6 after PvLP2 stimulation than P. vivax-infected women (p<0.05). These data demonstrate that VIR antigens induce the natural acquisition of antibody and T cell memory responses that might be important in immunity to P. vivax during pregnancy in very diverse geographical settings. [ABSTRACT FROM AUTHOR]

Coxsackievirus A16 (CA16) is one of the major causative agents of hand, foot, and mouth disease worldwide. The non-neutralizing antibody response that targets CA16 VP1 remains poorly elucidated. In the present study, antibody responses against CA16 VP1 in Shanghai blood donors and Shanxi individuals were analyzed by ELISA and inhibitory ELISA using five CA16 VP1 antigens: VP11-297, VP141-297, VP11-60, VP145-58 and VP161-297. The correlation coefficients for most of the reactions against each of the five antigens and the inhibition of the anti-CA16 VP1 antibody response produced by the various antigens were higher in Shanghai blood donors compared to those in Shanxi individuals. VP11-297 and VP141-297 strongly inhibited the anti-CA16 VP1 response in serum samples from both populations, while VP145-58 and VP161-297 intermediately and weakly inhibited the anti-CA16 VP1 response, respectively, in only Shanghai group. A specific type of inhibition (anti-CA16 VP1 was completely inhibited by both VP11-60 and VP141-297) characterized by high neutralizing antibody titers was identified and accounted for 71.4% of the strongly reactive samples from the Shanghai group. These results indicate that the Shanghai blood donors exhibited a consistent and specific antibody response, while the Shanxi individuals showed an inconsistent and non-specific antibody response. These findings may improve the understanding of host humoral immunity against CA16 and help to identify an effective approach for seroepidemiological surveillance and specific diagnosis of CA16 infection based on normal and competitive ELISA. [ABSTRACT FROM AUTHOR]

In the absence of effective vaccine(s), control of African swine fever caused by African swine fever virus (ASFV) must be based on early, efficient, cost-effective detection and strict control and elimination strategies. For this purpose, we developed an indirect ELISA capable of detecting ASFV antibodies in either serum or oral fluid specimens. The recombinant protein used in the ELISA was selected by comparing the early serum antibody response of ASFV-infected pigs (NHV-p68 isolate) to three major recombinant polypeptides (p30, p54, p72) using a multiplex fluorescent microbead-based immunoassay (FMIA). Non-hazardous (non-infectious) antibody-positive serum for use as plate positive controls and for the calculation of sample-to-positive (S:P) ratios was produced by inoculating pigs with a replicon particle (RP) vaccine expressing the ASFV p30 gene. The optimized ELISA detected anti-p30 antibodies in serum and/or oral fluid samples from pigs inoculated with ASFV under experimental conditions beginning 8 to 12 days post inoculation. Tests on serum (n = 200) and oral fluid (n = 200) field samples from an ASFV-free population demonstrated that the assay was highly diagnostically specific. The convenience and diagnostic utility of oral fluid sampling combined with the flexibility to test either serum or oral fluid on the same platform suggests that this assay will be highly useful under the conditions for which OIE recommends ASFV antibody surveillance, i.e., in ASFV-endemic areas and for the detection of infections with ASFV isolates of low virulence. [ABSTRACT FROM AUTHOR]

Post-vaccine monitoring programs for human papillomavirus (HPV) have been introduced in many countries, but HPV serology is still an underutilized tool, partly owing to the weak antibody response to HPV infection. Changes in antibody levels among non-vaccinated individuals could be employed to monitor herd effects of immunization against HPV vaccine types 16 and 18, but inference requires an appropriate statistical model. The authors developed a four-component bivariate mixture model for jointly estimating vaccine-type seroprevalence from correlated antibody responses against HPV16 and -18 infections. This model takes account of the correlation between HPV16 and -18 antibody concentrations within subjects, caused e.g. by heterogeneity in exposure level and immune response. The model was fitted to HPV16 and -18 antibody concentrations as measured by a multiplex immunoassay in a large serological survey (3,875 females) carried out in the Netherlands in 2006/2007, before the introduction of mass immunization. Parameters were estimated by Bayesian analysis. We used the deviance information criterion for model selection; performance of the preferred model was assessed through simulation. Our analysis uncovered elevated antibody concentrations in doubly as compared to singly seropositive individuals, and a strong clustering of HPV16 and -18 seropositivity, particularly around the age of sexual debut. The bivariate model resulted in a more reliable classification of singly and doubly seropositive individuals than achieved by a combination of two univariate models, and suggested a higher pre-vaccine HPV16 seroprevalence than previously estimated. The bivariate mixture model provides valuable baseline estimates of vaccine-type seroprevalence and may prove useful in seroepidemiologic assessment of the herd effects of HPV vaccination. [ABSTRACT FROM AUTHOR]

Ischemia-reperfusion (IR)-induced acute lung injury (ALI) is implicated in several clinical conditions like lung transplantation, acute pulmonary embolism after thrombolytic therapy, re-expansion of collapsed lung from pneumothorax or pleural effusion, cardiopulmonary bypass and etc. Because mortality remains high despite advanced medical care, prevention and treatment are important clinical issues for IR-induced ALI. Vascular endothelial growth factor (VEGF) has a controversial role in ALI. We therefore conducted this study to determine the effects of anti-VEGF antibody in IR-induced ALI. In the current study, the IR-induced ALI was conducted in a rat model of isolated-perfused lung in situ in the chest. The animals were divided into the control, control + preconditioning anti-VEGF antibody (bevacizumab, 5mg/kg), IR, IR + preconditioning anti-VEGF antibody (1mg/kg), IR+ preconditioning anti-VEGF antibody (5mg/kg) and IR+ post-IR anti-VEGF antibody (5mg/kg) group. There were eight adult male Sprague-Dawley rats in each group. The IR caused significant pulmonary micro-vascular hyper-permeability, pulmonary edema, neutrophilic infiltration in lung tissues, increased tumor necrosis factor-α, and total protein concentrations in bronchoalveolar lavage fluid. VEGF and extracellular signal-regulated kinase (ERK) were increased in IR-induced ALI. Administration of preconditioning anti-VEGF antibody significantly suppressed the VEGF and ERK expressions and attenuated the IR-induced lung injury. This study demonstrates the important role of VEGF in early IR-induced ALI. The beneficial effects of preconditioning anti-VEGF antibody in IR-induced ALI include the attenuation of lung injury, pro-inflammatory cytokines, and neutrophilic infiltration into the lung tissues. [ABSTRACT FROM AUTHOR]

An In Vitro Comparative Immunogenicity Assessment (IVCIA) assay was evaluated as a tool for predicting the potential relative immunogenicity of biotherapeutic attributes. Peripheral blood mononuclear cells from up to 50 healthy naïve human donors were monitored up to 8 days for T-cell proliferation, the number of IL-2 or IFN-γ secreting cells, and the concentration of a panel of secreted cytokines. The response in the assay to 10 monoclonal antibodies was found to be in agreement with the clinical immunogenicity, suggesting that the assay might be applied to immunogenicity risk assessment of antibody biotherapeutic attributes. However, the response in the assay is a measure of T-cell functional activity and the alignment with clinical immunogenicity depends on several other factors. The assay was sensitive to sequence variants and could differentiate single point mutations of the same biotherapeutic. Nine mAbs that were highly aggregated by stirring induced a higher response in the assay than the original mAbs before stirring stress, in a manner that did not match the relative T-cell response of the original mAbs. In contrast, mAbs that were glycated by different sugars (galactose, glucose, and mannose) showed little to no increase in response in the assay above the response to the original mAbs before glycation treatment. The assay was also used successfully to assess similarity between multiple lots of the same mAb, both from the same manufacturer and from different manufacturers (biosimilars). A strategy for using the IVCIA assay for immunogenicity risk assessment during the entire lifespan development of biopharmaceuticals is proposed. [ABSTRACT FROM AUTHOR]

The effect of humoral immunity on the composition of the oral microbiota is less intensively investigated than hygiene and diet, in part due to a lack of simple and robust systems for investigating interactions between salivary immunoglobulins and oral bacteria. Here we report the application of an ex situ method to investigate the specificity of salivary immunoglobulins for salivary bacteria. Saliva collected from six volunteers was separated into immunoglobulin and microbial fractions, and the microbial fractions were then directly exposed to salivary immunoglobulins of “self” and “non-self” origin. Antibody-selected bacteria were separated from their congeners using a magnetic bead system, selective for IgA or IgG isotypes. The positively selected fractions were then characterized using gel-based eubacterial-specific DNA profiling. The eubacterial profiles of positively selected fractions diverged significantly from profiles of whole salivary consortia based on volunteer (P≤ 0.001%) and immunoglobulin origin (P≤ 0.001%), but not immunoglobulin isotype (P = 0.2). DNA profiles of separated microbial fractions were significantly (p≤ 0.05) less diverse than whole salivary consortia and included oral and environmental bacteria. Consortia selected using self immunoglobulins were generally less diverse than those selected with immunoglobulins of non-self origin. Magnetic bead separation facilitated the testing of interactions between salivary antibodies and oral bacteria, showing that these interactions are specific and may reflect differences in recognition by self and non-self immunoglobulins. Further development of this system could improve understanding of the relationship between the oral microbiota and the host immune system and of mechanisms underlying the compositional stability of the oral microbiota. [ABSTRACT FROM AUTHOR]

The development of next-generation influenza vaccines that elicit strain-transcendent immunity against both seasonal and pandemic viruses is a key public health goal. Targeting the evolutionarily conserved epitopes on the stem of influenza’s major surface molecule, hemagglutinin, is an appealing prospect, and novel vaccine formulations show promising results in animal model systems. However, studies in humans indicate that natural infection and vaccination result in limited boosting of antibodies to the stem of HA, and the level of stem-specific antibody elicited is insufficient to provide broad strain-transcendent immunity. Here, we use mathematical models of the humoral immune response to explore how pre-existing immunity affects the ability of vaccines to boost antibodies to the head and stem of HA in humans, and, in particular, how it leads to the apparent lack of boosting of broadly cross-reactive antibodies to the stem epitopes. We consider hypotheses where binding of antibody to an epitope: (i) results in more rapid clearance of the antigen; (ii) leads to the formation of antigen-antibody complexes which inhibit B cell activation through Fcγ receptor-mediated mechanism; and (iii) masks the epitope and prevents the stimulation and proliferation of specific B cells. We find that only epitope masking but not the former two mechanisms to be key in recapitulating patterns in data. We discuss the ramifications of our findings for the development of vaccines against both seasonal and pandemic influenza. [ABSTRACT FROM AUTHOR]

In order for a virus to persist, there must be a balance between viral replication and immune clearance. It is commonly believed that adaptive immunity drives clearance of viral infections and, thus, dysfunction or viral evasion of adaptive immunity is required for a virus to persist. Type I interferons (IFNs) play pleiotropic roles in the antiviral response, including through innate control of viral replication. Murine norovirus (MNoV) replicates in dendritic cells (DCs) and type I IFN signaling in DCs is important for early control of MNoV replication. We show here that the non-persistent MNoV strain CW3 persists systemically when CD11c positive DCs are unable to respond to type I IFN. Persistence in this setting is associated with increased early viral titers, maintenance of DC numbers, increased expression of DC activation markers and an increase in CD8 T cell and antibody responses. Furthermore, CD8 T cell function is maintained during the persistent phase of infection and adaptive immune cells from persistently infected mice are functional when transferred to Rag1-/- recipients. Finally, increased early replication and persistence are also observed in mixed bone marrow chimeras where only half of the CD11c positive DCs are unable to respond to type I IFN. These findings demonstrate that increased early viral replication due to a cell-intrinsic innate immune deficiency is sufficient for persistence and a functional adaptive immune response is not sufficient for viral clearance. [ABSTRACT FROM AUTHOR]

Spores of Bacillus anthracis, the causative agent of anthrax, are known to persist in the host lungs for prolonged periods of time, however the underlying mechanism is poorly understood. In this study, we demonstrated that BclA, a major surface protein of B. anthracis spores, mediated direct binding of complement factor H (CFH) to spores. The surface bound CFH retained its regulatory cofactor activity resulting in C3 degradation and inhibition of downstream complement activation. By comparing results from wild type C57BL/6 mice and complement deficient mice, we further showed that BclA significantly contributed to spore persistence in the mouse lungs and dampened antibody responses to spores in a complement C3-dependent manner. In addition, prior exposure to BclA deletion spores (ΔbclA) provided significant protection against lethal challenges by B. anthracis, whereas the isogenic parent spores did not, indicating that BclA may also impair protective immunity. These results describe for the first time an immune inhibition mechanism of B. anthracis mediated by BclA and CFH that promotes spore persistence in vivo. The findings also suggested an important role of complement in persistent infections and thus have broad implications. [ABSTRACT FROM AUTHOR]

The C-terminal region of the M-protein of Streptococcus pyogenes is a major target for vaccine development. The major feature is the C-repeat region, consisting of 35–42 amino acid repeat units that display high but not perfect identity. SV1 is a S. pyogenes vaccine candidate that incorporates five 14mer amino acid sequences (called J14i variants) from differing C-repeat units in a single recombinant construct. Here we show that the J14i variants chosen for inclusion in SV1 are the most common variants in a dataset of 176 unique M-proteins. Murine antibodies raised against SV1 were shown to bind to each of the J14i variants present in SV1, as well as variants not present in the vaccine. Antibodies raised to the individual J14i variants were also shown to bind to multiple but different combinations of J14i variants, supporting the underlying rationale for the design of SV1. A Lewis Rat Model of valvulitis was then used to assess the capacity of SV1 to induce deleterious immune response associated with rheumatic heart disease. In this model, both SV1 and the M5 positive control protein were immunogenic. Neither of these antibodies were cross-reactive with cardiac myosin or collagen. Splenic T cells from SV1/CFA and SV1/alum immunized rats did not proliferate in response to cardiac myosin or collagen. Subsequent histological examination of heart tissue showed that 4 of 5 mice from the M5/CFA group had valvulitis and inflammatory cell infiltration into valvular tissue, whereas mice immunised with SV1/CFA, SV1/alum showed no sign of valvulitis. These results suggest that SV1 is a safe vaccine candidate that will elicit antibodies that recognise the vast majority of circulating GAS M-types. [ABSTRACT FROM AUTHOR]

Antigen-antibody complexes are central players in an effective immune response. However, finding those interactions relevant to a particular disease state can be arduous. Nonetheless many paths to discovery have been explored since deciphering these interactions can greatly facilitate the development of new diagnostics, therapeutics, and vaccines. In silico B cell epitope mapping approaches have been widely pursued, though success has not been consistent. Antibody mixtures in immune sera have been used as handles for biologically relevant antigens, but these and other experimental approaches have proven resource intensive and time consuming. In addition, these methods are often tailored to individual diseases or a specific proteome, rather than providing a universal platform. Most of these methods are not able to identify the specific antibody’s epitopes from unknown antigens, such as un-annotated neo antigens in cancer. Alternatively, a peptide library comprised of sequences unrestricted by naturally-found protein space provides for a universal search for mimotopes of an antibody’s epitope. Here we present the utility of such a non-natural random sequence library of 10,000 peptides physically addressed on a microarray for mimotope discovery without sequence information of the specific antigen. The peptide arrays were probed with serum from an antigen-immunized rabbit, or alternatively probed with serum pre-absorbed with the same immunizing antigen. With this positive and negative screening scheme, we identified the library-peptides as the mimotopes of the antigen. The unique library peptides were successfully used to isolate antigen-specific antibodies from complete immune serum. Sequence analysis of these peptides revealed the epitopes in the immunized antigen. We present this method as an inexpensive, efficient method for identifying mimotopes of any antibody’s targets. These mimotopes should be useful in defining both components of the antigen-antibody complex. [ABSTRACT FROM AUTHOR]

Maternally-derived antibodies (MDAs) can protect offspring against influenza virus infection but may also inhibit active immune responses. To overcome MDA- mediated inhibition, active immunization of offspring with an inactivated H5N1 whole-virion vaccine under the influence of MDAs was explored in mice. Female mice were vaccinated twice via the intraperitoneal (IP) or intranasal (IN) route with the vaccine prior to mating. One week after birth, the offspring were immunized twice via the IP or IN route with the same vaccine and then challenged with a lethal dose of a highly homologous virus strain. The results showed that, no matter which immunization route (IP or IN) was used for mothers, the presence of MDAs severely interfered with the active immune response of the offspring when the offspring were immunized via the IP route. Only via the IN immunization route did the offspring overcome the MDA interference. These results suggest that intranasal immunization could be a suitable inoculation route for offspring to overcome MDA interference in the defense against highly pathogenic H5N1 virus infection. This study may provide references for human and animal vaccination to overcome MDA-induced inhibition. [ABSTRACT FROM AUTHOR]

Our study tested the hypothesis that immunoglobulins differ in their ability to activate the nuclear factor-κB pathway mediated cellular responses. These responses are modulated by several properties of the immune complex, including the ratio of antibody isotypes binding to antigen. Immunoassays allow the measurement of antigen specific antibodies belonging to distinct immunoglobulin classes and subclasses but not the net biological effect of the combination of these antibodies. We set out to develop a biosensor that is suitable for the detection and characterization of antigen specific serum antibodies. We genetically modified the monocytoid U937 cell line carrying Fc receptors with a plasmid encoding NF-κB promoter-driven GFP. This clone, U937-NF-κB, was characterized with respect to FcR expression and response to solid-phase immunoglobulins. Human IgG3, IgG4 and IgG1 induced GFP production in a time- and dose-dependent manner, in this order of efficacy, while IgG2 triggered no activation at the concentrations tested. IgA elicited no response alone but showed significant synergism with IgG3 and IgG4. We confirmed the importance of activation via FcγRI by direct stimulation with monoclonal antibody and by competition assays. We used citrullinated peptides and serum from rheumatoid arthritis patients to generate immune complexes and to study the activation of U937-NF-κB, observing again a synergistic effect between IgG and IgA. Our results show that immunoglobulins have distinct pro-inflammatory potential, and that U937-NF-κB is suitable for the estimation of biological effects of immune-complexes, offering insight into monocyte activation and pathogenesis of antibody mediated diseases. [ABSTRACT FROM AUTHOR]

Dengue is an infection of increasing global importance, yet uncertainty remains regarding critical aspects of its virology, immunology and epidemiology. One unanswered question is how infection is controlled and cleared during a dengue infection. Antibody is thought to play a role, but little past work has examined the kinetics of both virus and antibody during natural infections. We present data on multiple virus and antibody titres measurements recorded sequentially during infection from 53 Vietnamese dengue patients. We fit mechanistic mathematical models of the dynamics of viral replication and the host immune response to these data. These models fit the data well. The model with antibody removing virus fits the data best, but with a role suggested for ADCC or other infected cell clearance mechanisms. Our analysis therefore shows that the observed viral and antibody kinetics are consistent with antibody playing a key role in controlling viral replication. This work gives quantitative insight into the relationship between antibody levels and the efficiency of viral clearance. It will inform the future development of mechanistic models of how vaccines and antivirals might modify the course of natural dengue infection. [ABSTRACT FROM AUTHOR]

Dengue virus (DENV) is a major public health threat worldwide. A key element in protection from dengue fever is the neutralising antibody response. Anti-dengue IgG purified from DENV-2 infected human sera showed reactivity against several peptides when evaluated by ELISA and epitope extraction techniques. A multi-step computational approach predicted six antigenic regions within the E protein of DENV-2 that concur with the 6 epitopes identified by the combined ELISA and epitope extraction approach. The selected peptides representing B-cell epitopes were attached to a known dengue T-helper epitope and evaluated for their vaccine potency. Immunization of mice revealed two novel synthetic vaccine constructs that elicited good humoral immune responses and produced cross-reactive neutralising antibodies against DENV-1, 2 and 3. The findings indicate new directions for epitope mapping and contribute towards the future development of multi-epitope based synthetic peptide vaccine. [ABSTRACT FROM AUTHOR]

Parvoviruses have a predilection for rapidly dividing cells such as occurs during embryonic development. Potentially, in utero exposure could lead to immune tolerance in progeny mice. To determine if MPV infection in utero results in immune tolerance, pregnant mice were inoculated by oral gavage with 50 ID50 MPV1e or sham inoculated with phosphate buffered saline at day 5 and 12 gestation. Offspring were fostered to MPV-negative recipient dams prior to development of a milk spot. After confirming the offspring were seronegative for MPV by serology and not shedding by fecal PCR, they were challenged with 50 ID50 MPV1e by oral gavage at weaning or sham inoculated. At 4 weeks post inoculation, all weanlings exposed in utero developed antibodies to MPV, and MPV was detected by fecal PCR. Similarly, all weanlings from sham-inoculated dams challenged with MPV developed antibodies and MPV was detected by fecal PCR. None of the sham inoculated weanling mice from MPV infected dams or sham infected dams developed antibodies to MPV nor was MPV detected by fecal PCR. These results demonstrate that in utero exposure to MPV1e via oral gavage was insufficient to induce immune tolerance and provides greater confidence that rederivation techniques may successfully eliminate colonies of MPV. Furthermore, our findings do not provide evidence that MPV tolerance may contribute to hidden infections in mouse colonies. [ABSTRACT FROM AUTHOR]