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Background Patients who develop serious illness due to COVID-19 are more likely to have bacterial coinfections, for which WHO recommends treatment with antibiotics. As a result, many countries are observing a change in antimicrobial stewardship (AMS), in addition to changes in infection prevention and control (IPC) practices such as the use of personal protective equipment, on COVID-19 wards. Few data on COVID-19 and its impact on nosocomial infections and antimicrobial resistance (AMR) are available from low and middle-income countries (LMICs). As these countries often have high rates of AMR, it is vital to report the effects of COVID-19 on AMS so as to inform clinical practice and IPC guidelines. This study aims to compare prevalence of AMR in COVID-19 wards with general non-COVID-19 hospital wards. Methods This pilot hospital-based study is being conducted in two sites in both Sudan and Zambia. IPC and AMS guidelines for COVID-19 and non-COVID-19 wards were identified for each institution. This study is comparing bacterial isolates and AMR patterns of nosocomial associated infections acquired on COVID-19 and non-COVID-19 wards were compared, using microbiological and sequencing methods. A total of 200 patients have been recruited: 100 per country, 50 COVID-19 patients and 50 non-COVID-19 patients. AMR transmission patterns are being identified using Oxford Nanopore Technologies sequencing for phylogenetic analysis. Results The study began recruiting in May 2021 and completed recruitment of patients in October 2021. The majority of microbiological laboratory work will be completed within Q3 2021, with analysis of the results and sequencing completed in Q4 2021. A half-way point summary analysis of the data suggests differences in patient profiles, both between COVID-19 and non-COVID-19 wards at both sites, as well as differences between the two countries. Preliminary analysis also suggests a significant difference between the prevalence of MDR infections in Gram-negatives seen between COVID-19 (53% in Sudan and 83% in Zambia) and non-COVID-19 (14% Sudan, 33% Zambia) (t-test, P=0.0032 Sudan, P=0.0455 Zambia) ward patients in both countries (see Figure 1). Conclusions The study is providing evidence to inform policy on IPC and AMS measures to be implemented on COVID-19 wards. In addition, the outcomes of the study will be used to create a pragmatic sequencing pipeline for potential AMR outbreaks suitable for use in LMICs clinical settings.

The turnaround times for phenotypic tests used to monitor the bacterial load ofWe report the adaptation of our robust, culture-free assay utilising 16S ribosomal RNA, developed for sputum, to enumerate the number of bacteria present in animal tissues as a tool to improve the read-outs in preclinical drug efficacy studies.Initial assay adaptation was performed using naïve mouse lungs spiked with known quantities ofWhen tested on lung tissues derived from infected mice, the MBL assay produced comparable results to the bacterial counts in solid culture (colony forming units: CFU). Notably, under specific drug treatments, the MBL assay was able to detect a significantly higher number ofThe MBL assay can enumerate the bacterial load in animal tissues in real time without the need to wait for extended periods for cultures to grow. The readout correlates well with CFUs. Importantly, we have shown that the MBL is able to measure specific populations of bacteria not cultured on solid agar. The adaptation of this assay for preclinical studies has the potential to decrease the readout time of data acquisition from animal experiments and could represent a valuable tool for tuberculosis drug discovery and development.

Tuberculosis (TB) remains a major global threat and diagnosis of active TB ((ATB) both extra-pulmonary (EPTB), pulmonary (PTB)) and latent TB (LTBI) infection remains challenging, particularly in high-burden countries which still rely heavily on conventional methods. Although molecular diagnostic methods are available, e.g., Cepheid GeneXpert, they are not universally available in all high TB burden countries. There is intense focus on immune biomarkers for use in TB diagnosis, which could provide alternative low-cost, rapid diagnostic solutions. In our previous gene expression studies, we identified peripheral blood leukocyte (PBL) mRNA biomarkers in a non-human primate TB aerosol-challenge model. Here, we describe a study to further validate select mRNA biomarkers from this prior study in new cohorts of patients and controls, as a prerequisite for further development. Whole blood mRNA was purified from ATB patients recruited in the UK and India, LTBI and two groups of controls from the UK (i) a low TB incidence region (CNTRLA) and (ii) individuals variably-domiciled in the UK and Asia ((CNTRLB), the latter TB high incidence regions). Seventy-two mRNA biomarker gene targets were analyzed by qPCR using the Roche Lightcycler 480 qPCR platform and data analyzed using GeneSpring™ 14.9 bioinformatics software. Differential expression of fifty-three biomarkers was confirmed between MTB infected, LTBI groups and controls, seventeen of which were significant using analysis of variance (ANOVA): CALCOCO2, CD52, GBP1, GBP2, GBP5, HLA-B, IFIT3, IFITM3, IRF1, LOC400759 (GBP1P1), NCF1C, PF4V1, SAMD9L, S100A11, TAF10, TAPBP, and TRIM25. These were analyzed using receiver operating characteristic (ROC) curve analysis. Single biomarkers and biomarker combinations were further assessed using simple arithmetic algorithms. Minimal combination biomarker panels were delineated for primary diagnosis of ATB (both PTB and EPTB), LTBI and identifying LTBI individuals at high risk of progression which showed good performance characteristics. These were assessed for suitability for progression against the standards for new TB diagnostic tests delineated in the published World Health Organization (WHO) technology product profiles (TPPs).

Contains fulltext : 220733.pdf (Publisher’s version ) (Open Access) In this comparative biomarker study, we analysed 1768 serial sputum samples from 178 patients at 4 sites in Southeast Africa. We show that tuberculosis Molecular Bacterial Load Assay (TB-MBLA) reduces time-to-TB-bacillary-load-result from days/weeks by culture to hours and detects early patient treatment response. By day 14 of treatment, 5% of patients had cleared bacillary load to zero, rising to 58% by 12th week of treatment. Fall in bacillary load correlated with mycobacterial growth indicator tube culture time-to-positivity (Spearmans r=-0.51, 95% CI (-0.56 to -0.46), p

ObjectivesBetter outcomes in tuberculosis require new diagnostic and treatment monitoring tools. In this paper we evaluated the utility of a marker ofM. tuberculosisviable count, the Molecular Bacterial Load assay (MBLA) for diagnosis and treatment monitoring of tuberculosis in a high burden setting.MethodsPatients with smear positive pulmonary tuberculosis from two sites in Tanzania and one each in Malawi and Mozambique. Sputum samples were taken weekly for the first 12 weeks of treatment and evaluated by MBLA and mycobacterial growth indicator tube method (MGIT).ResultsThe results of high and low positive control samples confirmed inter site reproducibility. Over the 12 weeks of treatment there was a steady decline in the viable bacterial load as measured by the MBLA that corresponds to rise in time to a positive result (TTP) in the Mycobacterial Growth Indicator Tube. Both MBLA and MGIT provided similar time to test negativity. Importantly, as treatment progressed samples in MGIT were increasingly likely to be contaminated, which compromised the acquisition of results but did not affect MBLA samples.ConclusionsMBLA produces a reproducible measure ofMtbviable count comparable to that of MGIT that is not compromised by contamination in a real-world setting. As a molecular test, the results can be available in as little as four hours and could allow health care professionals to identify rapidly patients who are failing therapy.

Nucleic acid-based tests for infectious diseases currently used in the clinical laboratory and in point-of-care devices are diverse. Measurement challenges associated with standardization of quantitative viral load testing are discussed in relation to human cytomegalovirus, BK virus, and Epstein-Barr virus, while the importance of defining the performance of qualitative methods is illustrated with Mycobacterium tuberculosis and influenza virus. The development of certified reference materials whose values are traceable to higher-order standards and reference measurement procedures, using, for instance, digital PCR, will further contribute to the understanding of analytical performance characteristics and promote clinical data comparability.

Background: Tuberculosis is an infection that requires at least 6 months of chemotherapy in order to clear the bacteria from the patient's lungs. Usually, therapeutic monitoring is dependent on smear microscopy where a decline in acid-fast bacilli is observed. However, this might not be indicative of the actual decline of bacterial load and thus other tools such as culture and molecular assays are required for patient management.Case presentation: Here, we report the case of a 12-year-old Black African boy co-infected with tuberculosis and human immunodeficiency virus who remained smear culture positive and liquid culture negative for a prolonged period of time following chemotherapy. In order to determine whether there was any live bacteria present in his specimens, we applied the newly developed molecular bacterial load assay that detects the presence of 16S ribosomal ribonucleic acid derived from the bacteria. Using this methodology, we were able to quantify his bacterial load and inform the management of his treatment in order to reduce the disease burden. Following this intervention he went on to make a complete recovery.Conclusions: This case report highlights the value of improved biomarkers for monitoring the treatment of tuberculosis and the role of molecular assays such as the molecular bacterial load assay applied here. The molecular bacterial load assay detects bacterial ribonucleic acid which corresponds closely with the number of live bacilli as compared with polymerase chain reaction that detects deoxyribonucleic acid and may include dead bacteria.

Background Real-time PCR (qPCR) based methods, such as the Xpert MTB/RIF, are increasingly being used to diagnose tuberculosis (TB). While qualitative methods are adequate for diagnosis, the therapeutic monitoring of TB patients requires quantitative methods currently performed using smear microscopy. The potential use of quantitative molecular measurements for therapeutic monitoring has been investigated but findings have been variable and inconclusive. The lack of an adequate reference method and reference materials is a barrier to understanding the source of such disagreement. Digital PCR (dPCR) offers the potential for an accurate method for quantification of specific DNA sequences in reference materials which can be used to evaluate quantitative molecular methods for TB treatment monitoring. Methods To assess a novel approach for the development of quality assurance materials we used dPCR to quantify specific DNA sequences in a range of prototype reference materials and evaluated accuracy between different laboratories and instruments. The materials were then also used to evaluate the quantitative performance of qPCR and Xpert MTB/RIF in eight clinical testing laboratories. Results dPCR was found to provide results in good agreement with the other methods tested and to be highly reproducible between laboratories without calibration even when using different instruments. When the reference materials were analysed with qPCR and Xpert MTB/RIF by clinical laboratories, all laboratories were able to correctly rank the reference materials according to concentration, however there was a marked difference in the measured magnitude. Conclusions TB is a disease where the quantification of the pathogen could lead to better patient management and qPCR methods offer the potential to rapidly perform such analysis. However, our findings suggest that when precisely characterised materials are used to evaluate qPCR methods, the measurement result variation is too high to determine whether molecular quantification of Mycobacterium tuberculosis would provide a clinically useful readout. The methods described in this study provide a means by which the technical performance of quantitative molecular methods can be evaluated independently of clinical variability to improve accuracy of measurement results. These will assist in ultimately increasing the likelihood that such approaches could be used to improve patient management of TB. Electronic supplementary material The online version of this article (doi:10.1186/s12879-016-1696-7) contains supplementary material, which is available to authorized users.

Much uncertainty still exists over what T-cell responses need to be induced by an effective human immunodeficiency virus (HIV) vaccine. Previous studies have hypothesized that the effective CD8 + T-cell responses are those driving the selection of escape mutations that reduce viral fitness and therefore revert posttransmission. In this study, we adopted a novel approach to define better the role of reverting escape mutations in immune control of HIV infection. This analysis of sequences from 710 study subjects with chronic C-clade HIV type 1 infection demonstrates the importance of mutations that impose a fitness cost in the control of viremia. Consistent with previous studies, the viral set points associated with each HLA-B allele are strongly correlated with the number of Gag-specific polymorphisms associated with the relevant HLA-B allele ( r = −0.56, P = 0.0034). The viral set points associated with each HLA-C allele were also strongly correlated with the number of Pol-specific polymorphisms associated with the relevant HLA-C allele ( r = −0.67, P = 0.0047). However, critically, both these correlations were dependent solely on the polymorphisms identified as reverting. Therefore, despite the inevitable evolution of viral escape, viremia can be controlled through the selection of mutations that are detrimental to viral fitness. The significance of these results is in highlighting the rationale for an HIV vaccine that can induce these broad responses.

The extreme polymorphism in the human leukocyte antigen (HLA) class I region of the human genome is suggested to provide an advantage in pathogen defence mediated by CD8+ T cells. HLA class I molecules present pathogen-derived peptides on the surface of infected cells for recognition by CD8+ T cells. However, the relative contributions of HLA-A and -B alleles have not been evaluated. We performed a comprehensive analysis of the class I restricted CD8+ T-cell responses against human immunodeficiency virus (HIV-1), immune control of which is dependent upon virus-specific CD8+ T-cell activity. In 375 HIV-1-infected study subjects from southern Africa, a significantly greater number of CD8+ T-cell responses are HLA-B-restricted, compared to HLA-A (2.5-fold; P = 0.0033). Here we show that variation in viral set-point, in absolute CD4 count and, by inference, in rate of disease progression in the cohort, is strongly associated with particular HLA-B but not HLA-A allele expression (P < 0.0001 and P = 0.91, respectively). Moreover, substantially greater selection pressure is imposed on HIV-1 by HLA-B alleles than by HLA-A (4.4-fold, P = 0.0003). These data indicate that the principal focus of HIV-specific activity is at the HLA-B locus. Furthermore, HLA-B gene frequencies in the population are those likely to be most influenced by HIV disease, consistent with the observation that B alleles evolve more rapidly than A alleles. The dominant involvement of HLA-B in influencing HIV disease outcome is of specific relevance to the direction of HIV research and to vaccine design.

SJW, PDB, SGH and TMcH are part of the PreDiCT-TB consortium (http://​www.​predict-tb.​eu) which is funded from the Innovative Medicines Initiative Joint Undertaking (http://​www.​imi.​europa.​eu) under grant agreement No 115337, resources of which are composed of financial contribution from the European Union’s Seventh Framework Programme (FP7/2007-2013) and EFPIA companies’ in kind contribution. We would like to thank Kate Gould in the Bacterial Microarray Group at St. George’s for assistance with the microarray work. PDB acknowledges funding from the Wellcome Trust for the Bacterial Microarray Group at St. George’s (grant numbers 062511, 080039, and 086547) for access to M.tb microarrays. IH, TMcH and SGH acknowledge funding from the Medical Research Council (G0601466) and the European Metrology Research Programme (EMRP) INFECT-MET (HLT-08); the EMRP is jointly funded by the EMRP participating countries within EURAMET and the European Union. Background. New treatment options are needed to maintain and improve therapy for tuberculosis, which caused the death of 1.5 million people in 2013 despite potential for an 86 % treatment success rate. A greater understanding of Mycobacterium tuberculosis (M.tb) bacilli that persist through drug therapy will aid drug development programs. Predictive biomarkers for treatment efficacy are also a research priority. Methods and Results. Genome-wide transcriptional profiling was used to map the mRNA signatures of M.tb from the sputa of 15 patients before and 3, 7 and 14 days after the start of standard regimen drug treatment. The mRNA profiles of bacilli through the first 2 weeks of therapy reflected drug activity at 3 days with transcriptional signatures at days 7 and 14 consistent with reduced M.tb metabolic activity similar to the profile of pre-chemotherapy bacilli. These results suggest that a pre-existing drug-tolerant M.tb population dominates sputum before and after early drug treatment, and that the mRNA signature at day 3 marks the killing of a drug-sensitive sub-population of bacilli. Modelling patient indices of disease severity with bacterial gene expression patterns demonstrated that both microbiological and clinical parameters were reflected in the divergent M.tb responses and provided evidence that factors such as bacterial load and disease pathology influence the host-pathogen interplay and the phenotypic state of bacilli. Transcriptional signatures were also defined that predicted measures of early treatment success (rate of decline in bacterial load over 3 days, TB test positivity at 2 months, and bacterial load at 2 months). Conclusions. This study defines the transcriptional signature of M.tb bacilli that have been expectorated in sputum after two weeks of drug therapy, characterizing the phenotypic state of bacilli that persist through treatment. We demonstrate that variability in clinical manifestations of disease are detectable in bacterial sputa signatures, and that the changing M.tb mRNA profiles 0–2 weeks into chemotherapy predict the efficacy of treatment 6 weeks later. These observations advocate assaying dynamic bacterial phenotypes through drug therapy as biomarkers for treatment success. Publisher PDF

Protocol for gDNA extraction and dPCR quantification of materials. (PDF 394 kb)

Method for restriction digestion of the TB Control Plasmid, dPCR analysis using the QuantStudio 3D platform, dPCR primers and thermal cycling conditions information, dPCR partition volume and partition number and mean λ values. Results from stability testing of the materials and analysis of BCG/ASM and Total MTB Control materials by Xpert MTB/RIF end-user laboratories including instrument and assay information, extraction and qPCR methods used by qPCR end user laboratories and their reported Cq values. (DOCX 114 kb)

Airway bacterial colonisation and respiratory symptoms are common in ambulatory HIV-positive UK adults http://ow.ly/Nug5A

Digital PCR (dPCR) offers absolute quantification through the limiting dilution of template nucleic acid molecules and has the potential to offer high reproducibility. However, the robustness of dPCR has yet to be evaluated using complex genomes to compare different dPCR methods and platforms. We used DNA templates from the pathogen Mycobacterium tuberculosis to evaluate the impact of template type, master mixes, primer pairs and, crucially, extraction methods on dPCR performance. Performance was compared between the chip (BioMark) and droplet (QX100) formats. In the absence of any external calibration, dPCR measurements were generally consistent within ∼2-fold between different master mixes and primers. Template DNA integrity could influence dPCR performance: high molecular weight gDNA resulted in underperformance of one master mix, while restriction digestion of a low molecular weight sample also caused underestimation. Good concordance (≤1.5-fold difference) was observed between chip and droplet formats. Platform precision was in agreement with predicted Poisson error based on partition number, but this was a minor component (10%) of the total variance when extraction was included. dPCR offers a robust reproducible method for DNA measurement; however, as a predominant source of error, the process of DNA extraction will need to be controlled with suitable calibrators to maximize agreement between laboratories.

Selection of T-cell vaccine antigens for chronic persistent viral infections has been largely empirical. To define the relationship, at the population level, between the specificity of the cellular immune response and viral control for a relevant human pathogen, we performed a comprehensive analysis of the 160 dominant CD8(+) T-cell responses in 578 untreated HIV-infected individuals from KwaZulu-Natal, South Africa. Of the HIV proteins targeted, only Gag-specific responses were associated with lowering viremia. Env-specific and Accessory/Regulatory protein-specific responses were associated with higher viremia. Increasing breadth of Gag-specific responses was associated with decreasing viremia and increasing Env breadth with increasing viremia. Association of the specific CD8(+) T-cell response with low viremia was independent of HLA type and unrelated to epitope sequence conservation. These population-based data, suggesting the existence of both effective immune responses and responses lacking demonstrable biological impact in chronic HIV infection, are of relevance to HIV vaccine design and evaluation.

HIV-specific CTL play a central role in immune control of HIV. The basis for understanding the success or failure of this immune response requires identification of the specific epitopes targeted by CTL. However, in populations most severely affected by the global epidemic, this fundamental knowledge is hindered by the lack of characterization of many of the HLA class I alleles highly prevalent in such populations. Overall, the peptide-binding motif has been determined for a small minority (9%) of HLA class I alleles, with a strong bias toward those alleles prevalent in Caucasoid populations. These studies therefore set out to define, in a South African Zulu/Xhosa population at the epicenter of the epidemic, the epitopes presented by alleles highly prevalent, but for which the peptide-binding motif had not been characterized. Using a method of motif inference, epitopes presented by four such alleles prevalent in the Zulu/Xhosa population of Durban, South Africa, namely, B*3910, B*4201, B*8101, and Cw*1801, are described. Importantly, this approach may additionally facilitate optimization of epitopes in certain instances where conflicting reports in the literature exist regarding the peptide-binding motif, such as for HLA-A*2902, also highly prevalent in southern African populations. These data indicate that the previously anomalous position of HLA-A*2902 among HLA-A alleles, outside any recognized HLA-A supertype, is artifactual, and the true position of the A*2902 motif overlaps those of the A1 and A24 supertypes.

Small RNA (smRNA) is a diverse family of translation regulation molecules, which includes microRNA (miRNA). Changes in miRNA have been reported in association with respiratory disease [1] and in mycobacterial infection [2]. Studies have measured concentrations of miRNA pooled from multiple subjects with active tuberculosis (TB) disease compared with latently infected individuals and healthy controls [3]. However, this approach cannot assess variation between individuals, nor does it describe changes that might occur with treatment, both of which may be helpful in characterising and predicting patient outcome. Plasma small RNA concentration declines in response to anti-tuberculosis therapy and is independent of HIV-status We would like to thank S. Bokhari and S. Christou (Centre for Clinical Microbiology, Dept of Infection, University College London, London, UK) for assistance with sample processing and C. Smith (Research Dept of Infection and Population Health, University College London, London, UK) for statistical support.

A molecular assay to quantify Mycobacterium tuberculosis is described. In vitro , 98% ( n = 96) of sputum samples with a known number of bacilli (10 7 to 10 2 bacilli) could be enumerated within 0.5 log 10 . In comparison to culture, the molecular bacterial load (MBL) assay is unaffected by other microorganisms present in the sample, results are obtained more quickly (within 24 h) and are seldom inhibited (0.7% samples), and the MBL assay critically shows the same biphasic decline as observed longitudinally during treatment. As a biomarker of treatment response, the MBL assay responds rapidly, with a mean decline in bacterial load for 111 subjects of 0.99 log 10 (95% confidence interval [95% CI], 0.81 to 1.17) after 3 days of chemotherapy. There was a significant association between the rate of bacterial decline during the same 3 days and bacilli ml −1 sputum at day 0 (linear regression, P = 0.0003) and a 3.62 increased odds ratio of relapse for every 1 log 10 increase in pretreatment bacterial load (95% CI, 1.53 to 8.59).

The potential importance of HLA-C-restricted CD8 + cytotoxic T lymphocytes (CTL) in HIV infection remains undetermined. We studied the dominant HLA-Cw*03-restricted CTL response to YVDRFFKTL 296-304 (YL9), within the conserved major homology region (MHR) of the Gag protein, in 80 HLA-Cw*03-positive individuals with chronic HIV infection to better define the efficacy of the YL9 HLA-C-restricted response. The HLA-Cw*03 allele is strongly associated with HIV sequence changes from Thr-303 to Val, Ile, or Ala at position 8 within the YL9 epitope ( P = 1.62 × 10 −10 ). In vitro studies revealed that introduction of the changes T303I and T303A into the YL9 epitope both significantly reduced CTL recognition and substantially reduced the viral replicative capacity. However, subsequent selection of the Val-303 variant, via intracodon variation from Ile-303 (I303V) or Ala-303 (A303V), restored both viral fitness and CTL recognition, as supported by our in vivo data. These results illustrate that HLA-C-restricted CTL responses are capable of driving viral immune escape within Gag, but in contrast to what was previously described for HLA-B-restricted Gag escape mutants, the common Cw*03-Gag-303V variant selected resulted in no detectable benefit to the host.

The observed association between HLA-B*13 and control of human immunodeficiency virus type 1 (HIV-1) infection has been linked to the number of Gag-specific HLA-B*13-restricted cytotoxic T-cell (CTL) responses identified. To date, the Gag escape mutations described that result in an in vitro fitness cost to the virus have been located within structural protein p24 only. Here we investigated the hypothesis that CTL escape mutations within other regions of HIV Gag may also reduce viral fitness and contribute to immune control. We analyzed an HLA-B*13-restricted CTL response toward an epitope in p1 Gag, RQANFLGKI 429-437 (RI9), where amino acid variation at Gag residues 436 and 437 is associated with HLA-B*13 expression. In this work, we assessed the impact of amino acid substitutions at these positions on CTL recognition and on HIV-1 fitness. We demonstrated that substitutions I437L and I437M largely abrogate CTL recognition and reduce viral fitness while variants K436R and I437V have only a marginal effect on recognition and fitness. Examination of the patterns of protein synthesis indicated that the loss of fitness in the I437L and I437M mutants is associated with the accumulation of unprocessed Gag precursors. A significant reduction in ribosomal frameshifting efficiency was observed with I437M, suggesting that this mechanism contributes to the observed reduced fitness of this virus. These studies illustrate the apparent trade-off available to the virus between evasion of CTL recognition in p1 Gag and the functional consequences for viral fitness.

HLA-B*5703 is associated with effective immune control in human immunodeficiency virus type 1 (HIV-1) infection. Here we describe an escape mutation within the immunodominant HLA-B*5703-restricted epitope in chronic HIV-1 infection, KAFSPEVIPMF (Gag 162-172), and demonstrate that this mutation reduces viral replicative capacity. Reversion of this mutation following transmission to HLA-B*5703-negative recipients was delayed by the compensatory mutation S165N within the same epitope. These data may help explain the observed association between HLA-B*5703 and long-term control of viremia.

In HIV-infected persons, certain HLA class I alleles are associated with effective control of viremia, while others are associated with rapid disease progression. Among the most divergent clinical outcomes are the relatively good prognosis in HLA-B*5801 expressing persons and poor prognosis with HLA-B*5802. These two alleles differ by only three amino acids in regions involved in HLA-peptide recognition. This study evaluated a cohort of over 1000 persons with chronic HIV clade C virus infection to determine whether clinical outcome differences associated with B*5801 (n = 93) and B*5802 ( n = 259) expression are associated with differences in HIV-1-specific CD8 (+) T cell responses. The overall breadth and magnitude of HIV-1-specific CD8(+) T cell responses were lower in persons expressing B*5802, and epitope presentation by B*5802 contributed significantly less to the overall response as compared to B*5801-restricted CD8 (+) T cells. Moreover, viral load in B*5802-positive persons was higher and CD4 cell counts lower when this allele contributed to the overall CD8 (+) T cell response, which was detected exclusively through a single epitope in Env. In addition, persons heterozygous for B*5802 compared to persons homozygous for other HLA-B alleles had significantly higher viral loads. Viral sequencing revealed strong selection pressure mediated through B*5801-restricted responses but not through B*5802. These data indicate that minor differences in HLA sequence can have a major impact on epitope recognition, and that selective targeting of Env through HLA-B*5802 is at least ineffectual if not actively adverse in the containment of viremia. These results provide experimental evidence that not all epitope-specific responses contribute to immune containment, a better understanding of which is essential to shed light on mechanisms involved in HIV disease progression.

The relationship between the function of human immunodeficiency virus (HIV)-specific CD8 T-cell responses and viral load has not been defined. In this study, we used a panel of major histocompatibility complex class I tetramers to examine responses to frequently targeted CD8 T-cell epitopes in a large cohort of antiretroviral-therapy-naïve HIV type 1 clade C virus-infected persons in KwaZulu Natal, South Africa. In terms of effector functions of proliferation, cytokine production, and degranulation, only proliferation showed a significant correlation with viral load. This robust inverse relationship provides an important functional correlate of viral control relevant to both vaccine design and evaluation.

Background. The relative immunogenicity of human immunodeficiency virus type 1 (HIV-1) proteins for CD8 + and CD4 + cell responses has not been defined. Methods. HIV-1-specific T cell responses were evaluated in 65 chronically HIV-1-infected untreated subjects by interferon-γ flow cytometry with peptides spanning the clade C consensus sequence. Results. The magnitude of HIV-1-specific CD8 + T cell responses correlated significantly with CD4' cell responses, but the percentage of CD8 + T cells directed against HIV-1 (median, 2.76%) was always greater than that of CD4 + cells (median, 0.24%). Although CD8 + T cell responses were equally distributed among Gag, Pol, and the regulatory and accessory proteins, Gag was the dominant target for CD4 + cell responses. There was no consistent relationship between virus-specific CD8 + or CD4' cell response and viral load. However, the median viral load in subjects in whom Gag was the dominant CD8 + T cell target was significantly lower than that in subjects in whom non-Gag proteins were the main target (P =.007). Conclusions. Gag-specific responses dominate the CD4 + T cell response to HIV, whereas CD8 + T cell responses are broadly distributed, which indicates differential immunogenicity of these cells against HIV-1. The preferential targeting of Gag by CD8 + T cells is associated with enhanced control of viral load.

Human immunodeficiency virus (HIV)-1 amino acid sequence polymorphisms associated with expression of specific human histocompatibility leukocyte antigen (HLA) class I alleles suggest sites of cytotoxic T lymphocyte (CTL)-mediated selection pressure and immune escape. The associations most frequently observed are between expression of an HLA class I molecule and variation from the consensus sequence. However, a substantial number of sites have been identified in which particular HLA class I allele expression is associated with preservation of the consensus sequence. The mechanism behind this is so far unexplained. The current studies, focusing on two examples of “negatively associated” or apparently preserved epitopes, suggest an explanation for this phenomenon: negative associations can arise as a result of positive selection of an escape mutation, which is stable on transmission and therefore accumulates in the population to the point at which it defines the consensus sequence. Such negative associations may only be in evidence transiently, because the statistical power to detect them diminishes as the mutations accumulate. If an escape variant reaches fixation in the population, the epitope will be lost as a potential target to the immune system. These data help to explain how HIV is evolving at a population level. Understanding the direction of HIV evolution has important implications for vaccine development.

Non-coding RNA molecules, particularly miRNA, regulate translation of mRNA and have been found to target expression of genes important in immune response, such as IFN-γ. Differences in blood transcriptome signatures and differential miRNA expression have been reported to discriminate between uninfected, active and latent tuberculosis. We analysed the ability of small RNA molecules (0–150 nucleotides) in blood plasma to act as biomarkers of tuberculosis treatment response. Total blood plasma small RNA (0–150 nucleotides) concentration was significantly higher (p -1 plasma, range 93–1603pg μL -1 ) than at the end of therapy at week 24 (median 86pg μL -1 plasma, range 16–1098pg μL -1 ). Expression analysis of small RNA genes revealed that, in 5 tuberculosis-infected HIV-1 negative individuals, 36 of 90 genes (> 2-fold, p 2 fold in active tuberculosis. Co-infection with HIV-1 was not found to change the expression of these six tested biomarkers.

Figure S1. An illustration of the computation process to test associations between transcriptional signatures and patient variables. Figure S2. Venn diagrams describing the overlapping transcriptional signatures of bacilli in sputum relative to aerobic log phase growth. Figure S3. Box and whisker plots mapping the differential expression of gene families. Figure S4. Hierarchical clustering of the mean M.tb transcriptional profiles derived from sputa. Figure S5. Venn diagram highlighting genes significantly induced 3 days after the start of drug therapy. Figure S6. Contrasting patient trajectories as defined by principle component analysis plotting day 0 and day 3 timepoints only. (PDF 526 kb)

Figure S1. An illustration of the computation process to test associations between transcriptional signatures and patient variables. Figure S2. Venn diagrams describing the overlapping transcriptional signatures of bacilli in sputum relative to aerobic log phase growth. Figure S3. Box and whisker plots mapping the differential expression of gene families. Figure S4. Hierarchical clustering of the mean M.tb transcriptional profiles derived from sputa. Figure S5. Venn diagram highlighting genes significantly induced 3 days after the start of drug therapy. Figure S6. Contrasting patient trajectories as defined by principle component analysis plotting day 0 and day 3 timepoints only. (PDF 526 kb)