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1.  Extended High Viremics: A Substantial Fraction of Individuals Maintain High Plasma Viral RNA Levels after Acute HIV-1 Subtype C Infection 
AIDS (London, England)  2011;25(12):1515-1522.
This study addressed two questions: (1) What fraction of individuals maintain a sustained high HIV-1 RNA load after the acute HIV-1C infection peak? and (2) How long is a high HIV-1 RNA load maintained after acute HIV-1C infection in this subpopulation?
Plasma HIV-1 RNA dynamics were studied in 77 subjects with primary HIV-1C infection from African cohorts in Gaborone, Botswana, and Durban, South Africa. HIV-infected individuals who maintained mean viral load of ≥ 100,000 (5.0 log10) copies/ml after 100 days post-seroconversion (p/s) were termed Extended High Viremics. Individuals were followed longitudinally for a median (IQR) of 573 (226;986) days p/s.
The proportion of Extended High Viremics was 34% (95% CI: 23%–44%) during the period 100 to 300 days p/s and 19% (95% CI: 9%–29%) over the period of 200 to 400 days p/s. The median (IQR) duration of HIV-1 RNA load ≥ 100,000 copies/ml among Extended High Viremics was 271 (188;340) days p/s. For the subset with average viral load ≥ 100,000 copies/ml during 200–400 days p/s, the median (IQR) duration was 318 (282;459) days. The Extended High Viremics had a significantly shorter time to CD4 decline to 350 cells/μl (median: 88 vs. 691 days p/s for those not designated as Extended High Viremics; p<0.0001, Gehan-Wilcoxon test).
A high proportion of Extended High Viremics – individuals maintaining high plasma HIV-1 RNA load after acute infection – has been identified during primary HIV-1 subtype C infection. These Extended High Viremics likely contribute disproportionately to HIV-1 incidence.
PMCID: PMC3544358  PMID: 21505307
HIV-1 subtype C; primary infection; viral HIV-1 RNA load; Southern Africa; HIV-1 transmission
2.  Limited Immunogenicity of HIV CD8+ T-Cell Epitopes in Acute Clade C Virus Infection 
The Journal of Infectious Diseases  2011;204(5):768-776.
Background. Human immunodeficiency virus type 1 (HIV-1)–specific CD8+ responses contribute to the decline in acute peak viremia following infection. However, data on the relative immunogenicity of CD8+ T-cell epitopes during and after acute viremia are lacking.
Methods. We characterized CD8+ T-cell responses in 20 acutely infected, antiretroviral-naive individuals with HIV-1 subtype C infection using the interferon-γ enzyme-linked immunosorbent spot assay. Eleven of these had not fully seroconverted at the time of analysis. Viruses from plasma were sequenced within defined cytotoxic T-lymphocyte (CTL) cell epitopes for selected subjects.
Results. At approximately 28 days after estimated initial infection, CD8+ T-cell responses were directed against an average of 3 of the 410 peptides tested (range, 0–6); 2 individuals had no detectable responses at this time. At 18 weeks, the average number of peptides targeted had increased to 5 (range 0–11). Of the 56 optimal Gag CTL epitopes sequenced, 31 were wild-type in the infecting viruses, but only 11 of 31 elicited measurable CD8+ T-cell responses.
Conclusions. These data demonstrate that the majority of CD8+ responses are not elicited during acute HIV infection despite the presence of the cognate epitope in the infecting strain. There is a need to define factors that influence lack of induction of effective immune responses and the parameters that dictate immunodominance in acute infection.
PMCID: PMC3156105  PMID: 21844303
3.  Short Communication: CD8+ T Cell Polyfunctionality Profiles in Progressive and Nonprogressive Pediatric HIV Type 1 Infection 
AIDS Research and Human Retroviruses  2011;27(9):1005-1012.
Pediatric HIV-1 infection is characterized by rapid disease progression and without antiretroviral therapy (ART), more than 50% of infected children die by the age of 2 years. However, a small subset of infected children progresses slowly to disease in the absence of ART. This study aimed to identify functional characteristics of HIV-1-specific T cell responses that distinguish children with rapid and slow disease progression. Fifteen perinatally HIV-infected children (eight rapid and seven slow progressors) were longitudinally studied to monitor T cell polyfunctionality. HIV-1-specific interferon (IFN)-γ+ CD8+ T cell responses gradually increased over time but did not differ between slow and rapid progressors. However, polyfunctional HIV-1-specific CD8+ T cell responses, as assessed by the expression of four functions (IFN-γ, CD107a, TNF-α, MIP-1β), were higher in slow compared to rapid progressors (p=0.05) early in infection, and was associated with slower subsequent disease progression. These data suggest that the quality of the HIV-specific CD8+ T cell response is associated with the control of disease in children as has been shown in adult infection.
PMCID: PMC3332389  PMID: 21288139
4.  Influence of Gag-Protease-Mediated Replication Capacity on Disease Progression in Individuals Recently Infected with HIV-1 Subtype C▿ 
Journal of Virology  2011;85(8):3996-4006.
HLA class I-mediated selection of immune escape mutations in functionally important Gag epitopes may partly explain slower disease progression in HIV-1-infected individuals with protective HLA alleles. To investigate the impact of Gag function on disease progression, the replication capacities of viruses encoding Gag-protease from 60 individuals in early HIV-1 subtype C infection were assayed in an HIV-1-inducible green fluorescent protein reporter cell line and were correlated with subsequent disease progression. Replication capacities did not correlate with viral load set points (P = 0.37) but were significantly lower in individuals with below-median viral load set points (P = 0.03), and there was a trend of correlation between lower replication capacities and lower rates of CD4 decline (P = 0.09). Overall, the proportion of host HLA-specific Gag polymorphisms in or adjacent to epitopes was negatively associated with replication capacities (P = 0.04), but host HLA-B-specific polymorphisms were associated with higher viral load set points (P = 0.01). Further, polymorphisms associated with host-specific protective HLA alleles were linked with higher viral load set points (P = 0.03). These data suggest that transmission or early HLA-driven selection of Gag polymorphisms results in reduced early cytotoxic T-lymphocyte (CTL) responses and higher viral load set points. In support of the former, 46% of individuals with nonprotective alleles harbored a Gag polymorphism exclusively associated with a protective HLA allele, indicating a high rate of their transmission in sub-Saharan Africa. Overall, HIV disease progression is likely to be affected by the ability to mount effective Gag CTL responses as well as the replication capacity of the transmitted virus.
PMCID: PMC3126116  PMID: 21289112
5.  A Molecular Assay for Sensitive Detection of Pathogen-Specific T-Cells 
PLoS ONE  2011;6(8):e20606.
Here we describe the development and validation of a highly sensitive assay of antigen-specific IFN-γ production using real time quantitative PCR (qPCR) for two reporters - monokine-induced by IFN-γ (MIG) and the IFN-γ inducible protein-10 (IP10). We developed and validated the assay and applied it to the detection of CMV, HIV and Mycobacterium tuberculosis (MTB) specific responses, in a cohort of HIV co-infected patients. We compared the sensitivity of this assay to that of the ex vivo RD1 (ESAT-6 and CFP-10)-specific IFN-γ Elispot assay. We observed a clear quantitative correlation between the two assays (P<0.001). Our assay proved to be a sensitive assay for the detection of MTB-specific T cells, could be performed on whole blood samples of fingerprick (50 uL) volumes, and was not affected by HIV-mediated immunosuppression. This assay platform is potentially of utility in diagnosis of infection in this and other clinical settings.
PMCID: PMC3154901  PMID: 21853018
6.  Gag-Protease-Mediated Replication Capacity in HIV-1 Subtype C Chronic Infection: Associations with HLA Type and Clinical Parameters▿ †  
Journal of Virology  2010;84(20):10820-10831.
The mechanisms underlying HIV-1 control by protective HLA class I alleles are not fully understood and could involve selection of escape mutations in functionally important Gag epitopes resulting in fitness costs. This study was undertaken to investigate, at the population level, the impact of HLA-mediated immune pressure in Gag on viral fitness and its influence on HIV-1 pathogenesis. Replication capacities of 406 recombinant viruses encoding plasma-derived Gag-protease from patients chronically infected with HIV-1 subtype C were assayed in an HIV-1-inducible green fluorescent protein reporter cell line. Viral replication capacities varied significantly with respect to the specific HLA-B alleles expressed by the patient, and protective HLA-B alleles, most notably HLA-B*81, were associated with lower replication capacities. HLA-associated mutations at low-entropy sites, especially the HLA-B*81-associated 186S mutation in the TL9 epitope, were associated with lower replication capacities. Most mutations linked to alterations in replication capacity in the conserved p24 region decreased replication capacity, while most in the highly variable p17 region increased replication capacity. Replication capacity also correlated positively with baseline viral load and negatively with baseline CD4 count but did not correlate with the subsequent rate of CD4 decline. In conclusion, there is evidence that protective HLA alleles, in particular HLA-B*81, significantly influence Gag-protease function by driving sequence changes in Gag and that conserved regions of Gag should be included in a vaccine aiming to drive HIV-1 toward a less fit state. However, the long-term clinical benefit of immune-driven fitness costs is uncertain given the lack of correlation with longitudinal markers of disease progression.
PMCID: PMC2950592  PMID: 20702636
7.  Immunodominant HIV-1-specific HLA-B- and HLA-C-restricted CD8+ T cells do not differ in polyfunctionality 
Virology  2010;405(2-3):483-491.
HIV-1 specific HLA-B-restricted CD8+ T cell responses differ from HLA-C-restricted responses in antiviral effectiveness. To investigate possible reasons for these differences, we characterized the frequency and polyfunctionality of immmunodominant HLA-B*57/B5801- and HLA-Cw*07-restricted CD8+ T cells occurring concurrently in nine study subjects assessing IFN-γ, TNF-α, IL-2, MIP-1β, and CD107a by flow cytometry and analyzed sequence variation in targeted epitopes. HLA-B*57/5801 and HLA-Cw*07 restricted CD8+ T cells did not differ significantly in polyfunctionality (p = 0.84). Possession of three or more functions correlated positively with CD4+ T cell counts (r = 0.85; p = 0.006) and monofunctional CD8+ T cells inversely correlated with CD4 cell counts (r = −0.79; p = 0.05). There were no differences in polyfunctionality of CD8+ T cells specific to wildtype versus mutated epitopes. These results suggest that loss of polyfunctionality and increase in monofunctional HIV-1-specific CD8+ T cells are associated with disease progression independent of restricting HLA allele. Furthermore, sequence variation does not appear to significantly impact CD8+ T cell polyfunctionality in chronic HIV-1 infection.
PMCID: PMC2954365  PMID: 20638093
HLA-B*57/5801; HLA-C; HIV-1 chronic infection; CD8+ T cells; Polyfunctionality
8.  Impact of select immunologic and virologic biomarkers on CD4 decline in chronic HIV-1 subtype C infection: Results from Sinikithemba longitudinal population-based cohort, Durban, South Africa 
The extent to which immunologic and clinical biomarkers influence HIV outcomes remains incompletely characterized, particularly for non-B subtypes. Based on data supporting in vitro HIV protein-specific CD8 T-lymphocyte responses as correlates of immune control in cross-sectional studies, we assessed the relationship of these responses, along with established HIV biomarkers, with rates of CD4 decline in subtype-C infection.
Bi-variate and multivariate mixed effects models were used to assess the relationship of baseline CD4, plasma viral load (pVL), HLA class I alleles, and HIV protein-specific CD8 responses with rate of CD4 decline in a longitudinal population-based cohort of 300 therapy-naïve, chronically infected adults with baseline CD4>200 cells/mm3 and pVL>500 copies/ml, over a median 25 months follow-up.
In bi-variate analyses, baseline CD4, pVL and possession of a protective HLA allele correlated significantly with rate of CD4 decline. No relationship was observed between HIV protein-specific CD8 responses and CD4 decline. Results from multivariate models, incorporating baseline CD4 (201–350 and >350), pVL (≤100,000 and >100,000), HLA (protective vs. not), yielded the ability to discriminate CD4 declines over a 10-fold range: the highest rate of decline was observed among individuals with CD4>350, pVL>100,000 with no protective HLA alleles (−59 cells/mm3/year), while the slowest decline was observed in individuals with CD4 201–350, pVL≤100,000 and a protective allele (−6 cells/mm3/year).
The combination of plasma viral load and HLA class I type, but not in vitro HIV protein-specific CD8 responses, differentiates rates of CD4 decline in chronic subtype-C infection better than either marker alone.
PMCID: PMC2777678  PMID: 19663693
HIV subtype C; disease progression; CD4 decline; HLA class I; HIV-specific CTL responses

Results 1-8 (8)