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Background: Glaesserella parasuis, the causative agent of Glӓsser's disease, is widespread in swine globally resulting in significant economic losses to the swine industry. Prevention of Glӓsser's disease in pigs has been plagued with an inability to design broadly protective vaccines, as many bacterin based platforms generate serovar or strain specific immunity. Subunit vaccines are of interest to provide protective immunity to multiple strains of G. parasuis. Selected proteins for subunit vaccination should be widespread, highly conserved, and surface exposed. Results: Two candidate proteins for subunit vaccination (RlpB and VacJ) against G. parasuis were identified using random mutagenesis and an in vitro organ culture system. Pigs were vaccinated with recombinant RlpB and VacJ, outer membrane proteins with important contributions to cellular function and viability. Though high antibody titers to the recombinant proteins and increased interferon-γ producing cells were found in subunit vaccinated animals, the pigs were not protected from developing systemic disease. Conclusions: It appears there may be insufficient RlpB and VacJ exposed on the bacterial surface for antibody to bind, preventing high RlpB and VacJ specific antibody titers from protecting animals from G. parasuis. Additionally, this work confirms the importance of utilizing the natural host species when assessing the efficacy of vaccine candidates. [ABSTRACT FROM AUTHOR]

Adjuvant formulations capable of inducing high titer and high affinity antibody responses would provide a major advance in the development of vaccines to viral infections such as HIV-1. Although oil-in-water emulsions, such as Freund's adjuvant (FCA/FIA), are known to be potent, their toxicity and reactogenicity make them unacceptable for human use. Here, we explored different adjuvants and compared their ability to elicit antibody responses to FCA/FIA. Recombinant soluble trimeric HIV-1 gp140 antigen was formulated in different adjuvants, including FCA/FIA, Carbopol-971P, Carbopol-974P and the licensed adjuvant MF59, or combinations of MF59 and Carbopol. The antigen-adjuvant formulation was administered in a prime-boost regimen into rabbits, and elicitation of antigen binding and neutralizing antibodies (nAbs) was evaluated. When used individually, only FCA/FIA elicited significantly higher titer of nAbs than the control group (gp140 in PBS (p<0.05)). Sequential prime-boost immunizations with different adjuvants did not offer improvements over the use of FCA/ FIA or MF59. Remarkably however, the concurrent use of the combination of Carbopol-971P and MF59 induced potent adjuvant activity with significantly higher titer nAbs than FCA/FIA (p<0.05). This combination was not associated with any obvious local or systemic adverse effects. Antibody competition indicated that the majority of the neutralizing activities were directed to the CD4 binding site (CD4bs). Increased antibody titers to the gp41 membrane proximal external region (MPER) and gp120 V3 were detected when the more potent adjuvants were used. These data reveal that the combination of Carbopol-971P and MF59 is unusually potent for eliciting nAbs to a variety of HIV-1 nAb epitopes. [ABSTRACT FROM AUTHOR]

Abstract: “Streptococcal inhibitor of complement” (SIC) and “distantly related to SIC” (DRS) are related virulence factors secreted by M1 and M12 strains of GAS, respectively. The human mucosal innate immune system, important components of which are β-defensins, secretory leukocyte proteinase inhibitor (SLPI) and lysozyme, provides the first line of defence against microorganisms. We report the interaction between DRS and these proteins; further investigations into the interaction of SIC with the β-defensins; and compare the sensitivity of M12 and M1 GAS to SLPI. We show that SLPI, which kills M1 GAS and is inhibited by SIC, cannot kill M12 GAS. DRS cannot inhibit SLPI killing of M1 GAS, although ELISA shows binding of DRS to SLPI. We suggest that the target for SLPI on M1 GAS resembles SIC, and soluble SIC inhibits by acting as a decoy for SLPI. M12 GAS may not have this target and cannot interact with SLPI. DRS inhibits the antibacterial action of hBD-2 and hBD-3. Binding of both SIC and DRS to hBD-2, and DRS to hBD-3, shows small positive enthalpy, suggesting that binding is largely hydrophobic. The data for SIC and hBD-3 indicate that this is not a homogeneous bimolecular interaction. We conclude that DRS shares several of the properties of SIC, and therefore can be considered an important virulence factor of M12 GAS and an aid to colonization of the host mucosae. [Copyright &y& Elsevier]

A sensitive assay for the functional activity of complement Factor I is described. This is based on its third proteolytic clip whereby Factor I cleaves cell-bound iC3b to cell-bound C3dg and soluble C3c, thereby abolishing conglutination of the cells. Factor H is required as a co-factor for Factor I activity. Because of the low affinity of iC3b for Factor H, the assay needs to be performed at low ionic strength. This assay is easier to perform than those based on the conversion of C3b to iC3b (the first two Factor I clips), there being no need for the unstable intermediate EAC142 or for purified C3. [ABSTRACT FROM AUTHOR]

Some strains of Streptococcus pyogenes secrete a virulence factor called the streptococcal inhibitor of complement (SIC) function. SIC is a polyfunctional protein that interacts with a number of host proteins and peptides, especially with those that are involved in host defense systems. In addition to inhibiting the complement-mediated lysis of cells, SIC inhibits lysozyme, secretory leukocyte proteinase inhibitor, and β-defensins. SIC also binds to proteins associated with the cytoskeleton and thereby may cause cytoskeletal derangement. The SIC molecule has three distinct structural domains constituting the N-proximal short repeat region (SRR), the central long repeat region (LRR), and the C-proximal proline-rich region (PRR). To map various functions to the structural domains, we have analyzed recombinant subclones expressing various parts of SIC and elastase-generated discrete fragments of SIC for binding to various ligands and for determining their biological properties. The results demonstrate the following. (a) SRR alone was sufficient to confer inhibition of complement function. (b) Anti-defensin and anti-lysozyme activities were mapped to the SRR plus LRR. (c) The LRR plus PRR harbored ezrin binding activity. [ABSTRACT FROM AUTHOR]

Hyaluronate lyase, which catalyses the degradation of hyaluronic acid (HA), has been described from several pathogenic streptococcal species. We describe, for the first time, identification and purification of hyaluronate lyase from the zoonotic pig pathogen Streptococcus suis. We have cloned the hyaluronate lyase gene from S. suis and used it to generate an allelic replacement knock-out mutant of S. suis serotype 7 that can no longer biosynthesise the enzyme. Interestingly, a limited strain survey indicates that hyaluronate lyase activity is not present in all disease isolates of S. suis. Polyclonal anti-hyaluronate lyase anti-serum raised against our recombinant hyaluronate lyase has been used in Western blots, showing that hyaluronate lyase activity is always associated with the presence of protein of the expected size, whereas lack of hyaluronate lyase activity is due to truncation or absence of the enzyme. We show that hyaluronate lyase activity is required for S. suis to use HA polymer as a carbon source and that supplying exogenous recombinant hyaluronate lyase to all S. suis strains tested allowed fermentation of the resultant HA breakdown products. [Copyright &y& Elsevier]

The membrane-proximal external region (MPER) of the human immunodeficiency virus, type 1 (HIV-1) envelope glycoprotein subunit gp41 is targeted by potent broadly neutralizing antibodies 2F5, 4E10, and 10E8. These antibodies recognize linear epitopes and have been suggested to target the fusion intermediate conformation of gp41 that bridges viral and cellular membranes. Anti-MPER antibodies exert different degrees of membrane interaction, which is considered to be the limiting factor for the generation of such antibodies by immunization. Here we characterize a fusion intermediate conformation of gp41 (gp41int-Cys) and show that it folds into an elongated~12- nm-long extended structure based on small angle x-ray scattering data. Gp41int-Cys was covalently linked to liposomes via its C-terminal cysteine and used as immunogen. The gp41int-Cys proteoliposomes were administered alone or in prime-boost regimen with trimeric envelope gp140CA018 in guinea pigs and elicited high anti-gp41 IgG titers. The sera interacted with a peptide spanning the MPER region, demonstrated competition with broadly neutralizing antibodies 2F5 and 4E10, and exerted modest lipid binding, indicating the presence of MPER-specific antibodies. Although the neutralization potency generated solely by gp140CA018 was higher than that induced by gp41int- Cys, the majority of animals immunized with gp41int-Cys proteoliposomes induced modest breadth and potency in neutralizing tier 1 pseudoviruses and replication-competent simian/ human immunodeficiency viruses in the TZM-bl assay as well as responses against tier 2 HIV-1 in the A3R5 neutralization assay. Our data thus demonstrate that liposomal gp41 MPER formulation can induce neutralization activity, and the strategy serves to improve breadth and potency of such antibodies by improved vaccination protocols. [ABSTRACT FROM AUTHOR]

RNA flow between organisms has been documented within and among different kingdoms of life. Recently, we demonstrated horizontal RNA transfer between honeybees involving secretion and ingestion of worker and royal jellies. However, how the jelly facilitates transfer of RNA is still unknown. Here, we show that worker and royal jellies harbor robust RNA-binding activity. We report that a highly abundant jelly component, major royal jelly protein 3 (MRJP-3), acts as an extracellular non-sequence-specific RNA-aggregating factor. Multivalent RNA binding stimulates higher-order assembly of MRJP-3 into extracellular ribonucleoprotein granules that protect RNA from degradation and enhance RNA bioavailability. These findings reveal that honeybees have evolved a secreted dietary RNA-binding factor to concentrate, stabilize, and share RNA among individuals. Our work identifies high-order ribonucleoprotein assemblies with functions outside cells and organisms. • Worker and royal jellies harbor robust RNA-binding activity • Major royal jelly protein 3 (MRJP-3) is the dietary RNA-binding factor • RNA stimulates higher-order assembly of MRJP-3 into extracellular RNP granules • MRJP-3 granules concentrate, stabilize, and enhance environmental RNA bioavailability Honeybees share RNA between individuals through secretion and ingestion of worker and royal jellies. Maori et al. identify a jelly factor, MRJP-3, that forms extracellular ribonucleoprotein granules that concentrate, protect, and enhance RNA uptake. They propose that MRJP-3 facilitates RNA transfer that drives social immunity and signaling among bees. [ABSTRACT FROM AUTHOR]