Carolyn Williamson

University of KwaZulu-Natal, Port Natal, KwaZulu-Natal, South Africa

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Publications (119)630.19 Total impact

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    ABSTRACT: Neutralizing antibodies (nAbs) are a high priority for vaccines that aim to prevent the acquisition of HIV-1 infection. Vaccine effectiveness will depend on the extent to which induced antibodies neutralize the global diversity of circulating HIV-1 variants. Using large panels of genetically and geographically diverse HIV-1 Env-pseudotyped viruses and chronic infection plasma samples, we unambiguously show that cross-clade nAb responses are commonly induced in response to infection by any virus clade. Nonetheless, neutralization was significantly greater when the plasma clade matched the clade of the virus being tested. This within-clade advantage was diminished in older, more diverse epidemics in southern Africa, the US and Europe compared to more recent epidemics in Asia. It was most pronounced for circulating recombinant form (CRF) 07_BC, which is common in China and is the least divergent lineage studied; this was followed by the slightly more diverse Asian CRF01_AE. We found no evidence that transmitted/founder viruses are generally more susceptible to neutralization and are therefore easier targets for vaccination than chronic viruses. Features of the gp120 V1V2 loop, in particular length, net charge and number of N-linked glycans, were associated with Env susceptibility and plasma neutralization potency in a manner consistent with neutralization-escape being a force that drives viral diversification and plasma neutralization breadth. The overall susceptibility of Envs and potencies of plasmas were highly predictive of the neutralization outcome of any single virus/plasma combination. These findings highlight important considerations for the design and testing of candidate HIV-1 vaccines that aim to elicit effective nAbs.
    Journal of virology. 08/2014;
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    ABSTRACT: Sexually transmitted infections (STI) and bacterial vaginosis (BV) cause female genital tract inflammation. This inflammation, which is often present in the absence of symptoms, is associated with increased susceptibility to HIV infection. We aimed to evaluate genital cytokine profiles and the degree of inflammation associated with common STIs and BV.
    Sexually transmitted infections. 08/2014;
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    ABSTRACT: In South Africa, adolescents constitute a key population at high risk of HIV acquisition. However, little is known about HIV transmission among students within schools. This study was undertaken to assess the risk factors for HIV infection and the extent of transmission among rural high school students. Between February and May 2012, consenting students from five randomly selected public sector high schools in rural KwaZulu-Natal participated in an anonymized cross-sectional survey. Dried blood spot samples were collected and tested for HIV. βHCG levels were measured in females for pregnancy. Family circumstances, socio-demographic and behavioral factors were assessed as potential risk factors. A subset (106/148, 72%) of HIV positive samples underwent gag p17p24 sequencing for phylogenetic analysis. A total of 3242 students (81.7% of enrolled students) participated. HIV prevalence was 6.8% [95% Confidence Interval (CI) 3.9-9.8%] in girls and 2.7% (CI 1.6-3.8%) in boys (aOR=3.0, CI 2.4-3.8; p<0.001). HIV prevalence increased from 4.6% (95% CI 1.9-7.3) in the 12-15 year old girls to 23.1% (95% CI 7.7-38.5) in girls over 20 years, whilst in boys HIV prevalence increased from 2.7% (95% CI 0.6-4.9) in the 12-15 year olds to 11.1% (95% CI 2.7-19.4) in those over 20 years. Sequencing of samples obtained from students revealed only 2 clusters suggesting within-school transmission and 3 inter-school clusters, while the remainder was most likely acquired from sources other than those currently attending the school concerned. HIV prevalence in both girls (aOR=3.6, CI 2.9-4.5; p<0.001) and boys (aOR=2.8, CI 1.2-6.2; p=0.01) was higher in those without a living biological mother. The high burden of HIV infection among students was not associated with intra-school transmission in this rural setting. Lack of a living parent is an important factor defining high risk in this group of adolescents.
    AIDS research and human retroviruses. 07/2014;
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    ABSTRACT: Background: While HIV subtype-B infected individuals generally progress to AIDS within 8-10 years, limited data exist for other clades, especially from Africa. We investigated rates of HIV disease progression of clade C-infected South African women. METHODS: Prospective sero-incidence cohorts in KwaZulu-Natal were assessed for acute HIV infection monthly (n=245) or 3-monthly (n=594) for up to four years. Rapid disease progression was defined as CD4 decline to <350 cells/µl by two years post-infection. Serial clinical and laboratory assessments were compared using survival analysis and logistic regression models. RESULTS: Sixty-two women were identified at median 42 days post-infection (IQR 34-59), contributing 282 person-years of follow-up. Mean CD4 count dropped by 39.6% at 3 months and 46.7% at 6 months post-infection in women with pre-infection measurements. CD4 decline to <350 cells/µl occurred in 31%, 44%, and 55% at 1, 2, and 3 years post-infection, respectively, and to <500 cells/µl in 69%, 79% and 81% at equivalent time-points. Predictors of rapid progression were CD4 count at 3 months post-infection [hazard ratio (HR) 2.07, 95% confidence interval 1.31-3.28, p=0.002], set-point viral load [HR 3.82 (1.51-9.67), p=0.012] and hepatitis B co-infection [HR 4.54 (1.31-15.69), p=0.017]. Conversely, presence of any of HLAB*1302, B*27, B*57, B*5801 or B*8101 alleles predicted non-rapid progression [HR 0.19 (0.05-0.74), p=0.016]. CONCLUSION: Nearly half of subtype C infected women progressed to CD4<350 cells/µl within two years of infection. Implementing 2013 WHO treatment guidelines (CD4<500) would require most individuals to start antiretroviral therapy within one year of HIV infection.
    Clinical infectious diseases : an official publication of the Infectious Diseases Society of America. 07/2014;
  • Journal of Virology 06/2014; · 5.08 Impact Factor
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    ABSTRACT: Early studies in Cape Town identified independent HIV-1 epidemics, with distinct viral subtypes, among men who have sex with men (MSM) and the heterosexual population. However, few recent HIV-1 subtype data are available for MSM in South Africa. We examined HIV-1 subtypes among MSM in Cape Town. Cross-sectional survey. Self-identified MSM were recruited from geographically and racially disparate communities across Cape Town. Participants completed behavioral questionnaires and underwent HIV testing. Virus isolated from infected participants underwent complete env gp160 sequencing, and HIV-1 subtypes were assigned through phylogenetic analysis. In total, 194 HIV-infected MSM were enrolled: 67% black African, 24% colored, and 9% white men. More black African men identified as bisexual or heterosexual compared with other races. Overall, 31%-66% of men reported a recent partner of another race. HIV-1 subtypes were confirmed for 143 participants: 81% were subtype C, 14% B, 1% A1, 1% F2, and 3 recombinant viruses. Subtype C virus was associated with black African race (P = 0.003 compared with colored; P < 0.001 compared with white), men who identified as bisexual/heterosexual (P = 0.01), and reported a female sexual partner in the last year (P = 0.02). Compared with previous studies, an increasing prevalence of subtype C virus was noted among white MSM. This molecular epidemiology study provides novel evidence of sexual network links between the heterosexual and MSM epidemics and between historically racially disparate communities. These findings provide insights into the drivers of HIV epidemics in different population groups and may have implications for prevention strategies.
    JAIDS Journal of Acquired Immune Deficiency Syndromes 04/2014; 65(4):473-80. · 4.65 Impact Factor
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    ABSTRACT: Antibodies capable of neutralizing HIV-1 often target variable regions 1 and 2 (V1V2) of the HIV-1 envelope, but the mechanism of their elicitation has been unclear. Here we define the developmental pathway by which such antibodies are generated and acquire the requisite molecular characteristics for neutralization. Twelve somatically related neutralizing antibodies (CAP256-VRC26.01-12) were isolated from donor CAP256 (from the Centre for the AIDS Programme of Research in South Africa (CAPRISA)); each antibody contained the protruding tyrosine-sulphated, anionic antigen-binding loop (complementarity-determining region (CDR) H3) characteristic of this category of antibodies. Their unmutated ancestor emerged between weeks 30-38 post-infection with a 35-residue CDR H3, and neutralized the virus that superinfected this individual 15 weeks after initial infection. Improved neutralization breadth and potency occurred by week 59 with modest affinity maturation, and was preceded by extensive diversification of the virus population. HIV-1 V1V2-directed neutralizing antibodies can thus develop relatively rapidly through initial selection of B cells with a long CDR H3, and limited subsequent somatic hypermutation. These data provide important insights relevant to HIV-1 vaccine development.
    Nature 03/2014; · 38.60 Impact Factor
  • Melissa-R Abrahams, Daniel Sheward, Carolyn Williamson
    AIDS (London, England) 01/2014; 28(1):142-4. · 4.91 Impact Factor
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    ABSTRACT: Nef plays a major role in HIV-1 pathogenicity. We studied HIV-1 subtype C infected individuals in acute/early (n=120) or chronic (n=207) infection to investigate the relationship between Nef-mediated CD4/HLA-I down-regulation activities and disease progression, and the influence of immune-driven sequence variation on these Nef functions. A single Nef sequence per individual was cloned into an expression plasmid, followed by transfection of a T cell line and measurement of CD4 and HLA-I expression. In early infection, a trend of higher CD4 down-regulation ability correlating with higher viral load set point was observed (r=0.19, p=0.05), and higher HLA-I down-regulation activity was significantly associated with faster rate of CD4 decline (p=0.02). HLA-I down-regulation function correlated inversely with the number HLA-associated polymorphisms previously associated with reversion in the absence of the selecting HLA allele (r=−0.21, p=0.0002). These data support consideration of certain Nef regions in HIV-1 vaccine strategies designed to attenuate the infection course.
    Virology. 01/2014; s 468–470:214–225.
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    ABSTRACT: Understanding the impact of HIV diversity on immunological responses to candidate immunogens is critical for HIV vaccine development. We investigated the reactivity and immunodominance patterns of HIV-1 consensus group M Gag and Nef in (i) Cameroon, where individuals infected with the predominant CRF02_AG clade were compared with those infected with diverse non-CRF02_AG clades; and (ii) in a multiclade epidemic, namely Cameroon, compared with a monoclade C epidemic, South Africa. We analyzed 57 HIV-infected individuals from Cameroon and 44 HIV-infected individuals from South Africa for differences in detecting HIV-1 consensus M Gag and Nef T cell responses using the IFN-γ ELISpot assay. We found no difference in the predicted epitope coverage between CRF02_AG and non-CRF02_AG viruses for either Gag or Nef. There were no differences in the magnitude and breadth of responses for CRF02_AG and non-CRF02_AG-infected individuals. In contrast, the specificity of epitope targeting was markedly different between the two groups, with fewer than one third (11/28) of peptides commonly recognized. Furthermore, only one peptide was commonly recognized by at least three individuals from both AG and non-AG groups, indicating poor immunodominance. For Nef, more than half of all targeted peptides (14/27) were recognized by both groups, and four peptides were commonly targeted by at least three individuals. Three times more peptides were exclusively targeted in the diverse non-CRF02_AG group compared to the CRF02_AG group (10 vs. 3). Of note, similar results were obtained when South Africa, a monoclade C epidemic, and Cameroon, a multiclade epidemic, were compared. The central nature of HIV-1 consensus M sequences resulted in their broad recognition, but failed to identify highly immunodominant peptides between homogeneous and diverse HIV epidemics.
    Vaccine 01/2014; · 3.77 Impact Factor
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    ABSTRACT: HIV-1 superinfection occurs when an infected individual acquires a distinct new viral strain. The rate of superinfection may be reflective of the underlying HIV risk in the population. The CAPRISA 004 clinical trial demonstrated that women who used a tenofovir containing microbicide gel had lower rates of HIV infection than women using a placebo gel. Women who contracted HIV-1 during the trial were screened for the occurrence of superinfection by next-generation sequencing of the viral gag and env genes. There were two cases (one in each trial arm) of subtype C superinfection identified from the 76 women with primary infection screened at two timepoints (rate of superinfection=1.5/100 person-years). Both women experienced a greater than 0.5 log increase in viral load during the window when superinfection occurred. The rate of superinfection was significantly lower than the overall primary HIV incidence in the microbicide trial (IRR=0.20; p=0.003). The women who seroconverted during the trial reported a significant increase in sexual contact with their stable partner four months after seroconversion (p<0.001), which may have lowered the risk of superinfection in this population. The lower frequency of SI compared to primary incidence is in contrast to a report from a general heterosexual African population, but agrees with a study of high-risk women in Kenya. A better understanding of the rate of HIV superinfection could have important implications for ongoing HIV vaccine research.
    Journal of clinical microbiology 12/2013; · 4.16 Impact Factor
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    ABSTRACT: Identification of the epitopes targeted by antibodies that can neutralize diverse HIV-1 strains can provide important clues for the design of a preventative vaccine. We have developed a computational approach that can identify key amino acids within the HIV-1 envelope glycoprotein that influence sensitivity to broadly cross-neutralizing antibodies. Given a sequence alignment and neutralization titers for a panel of viruses, the method works by fitting a phylogenetic model that allows the amino acid frequencies at each site to depend on neutralization sensitivities. Sites at which viral evolution influences neutralization sensitivity were identified using Bayes factors (BFs) to compare the fit of this model to that of a null model in which sequences evolved independently of antibody sensitivity. Conformational epitopes were identified with a Metropolis algorithm that searched for a cluster of sites with large Bayes factors on the tertiary structure of the viral envelope. We applied our method to ID50 neutralization data generated from seven HIV-1 subtype C serum samples with neutralization breadth that had been tested against a multi-clade panel of 225 pseudoviruses for which envelope sequences were also available. For each sample, between two and four sites were identified that were strongly associated with neutralization sensitivity (2ln(BF) > 6), a subset of which were experimentally confirmed using site-directed mutagenesis. Our results provide strong support for the use of evolutionary models applied to cross-sectional viral neutralization data to identify the epitopes of serum antibodies that confer neutralization breadth.
    Virology Journal 12/2013; 10(1):347. · 2.09 Impact Factor
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    ABSTRACT: Defining the characteristics of HIV-specific CD8+ T cell responses that lead to viral control is crucial for vaccine development. We evaluated the differential impact of magnitude, polyfunctional capacity and specificity of the CD8+ response at approximately 6 months post infection on viral set point at 12 months in a cohort of HIV-infected individuals. High frequencies of Gag and Nef responses endowed with four functions were the best predictors of a low viral set point.
    Journal of Virology 11/2013; · 5.08 Impact Factor
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    ABSTRACT: Identifying the targets of broadly neutralizing antibodies to HIV-1 and understanding how these antibodies develop remain important goals in the quest to rationally develop an HIV-1 vaccine. We previously identified a participant in the CAPRISA Acute Infection Cohort (CAP257) whose plasma neutralized 84% of heterologous viruses. In this study we showed that breadth in CAP257 was largely due to the sequential, transient appearance of three distinct broadly neutralizing antibody specificities spanning the first 4.5 years of infection. The first specificity targeted an epitope in the V2 region of gp120 that was also recognized by strain-specific antibodies 7 weeks earlier. Specificity for the autologous virus was determined largely by a rare N167 antigenic variant of V2, with viral escape to the more common D167 immunotype coinciding with the development of the first wave of broadly neutralizing antibodies. Escape from these broadly neutralizing V2 antibodies through deletion of the glycan at N160 was associated with exposure of an epitope in the CD4 binding site that became the target for a second wave of broadly neutralizing antibodies. Neutralization by these CD4 binding site antibodies was almost entirely dependent on the glycan at position N276. Early viral escape mutations in the CD4 binding site drove an increase in wave two neutralization breadth, as this second wave of heterologous neutralization matured to recognize multiple immunotypes within this site. The third wave targeted a quaternary epitope that did not overlap any of the four known sites of vulnerability on the HIV-1 envelope and remains undefined. Altogether this study showed that the human immune system is capable of generating multiple broadly neutralizing antibodies in response to a constantly evolving viral population that exposes new targets as a consequence of escape from earlier neutralizing antibodies.
    PLoS Pathogens 10/2013; 9(10):e1003738. · 8.14 Impact Factor
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    ABSTRACT: Use of antiretroviral-based microbicides for HIV-1 prophylaxis could introduce a transmission barrier that inadvertently facilitates the selection of fitter viral variants among incident infections. To investigate this, we assessed the in vitro function of gag-protease and nef sequences from participants who acquired HIV-1 during the CAPRISA 004 1% tenofovir microbicide gel trial. We isolated the earliest available gag-protease and nef gene sequences from 83 individuals and examined their in vitro function using recombinant viral replication capacity assays and surface protein downregulation assays, respectively. No major phylogenetic clustering and no significant differences in gag-protease or nef function were observed in participants who received tenofovir gel versus placebo gel prophylaxis. Results indicate that the partial protective effects of 1% tenofovir gel use in the CAPRISA 004 trial were not offset by selection of transmitted/early HIV-1 variants with enhanced Gag-Protease or Nef fitness.
    PLoS ONE 08/2013; 8(8):71758-. · 3.73 Impact Factor
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    ABSTRACT: Understanding human immunodeficiency virus type 1 (HIV-1) transmission is central to developing effective prevention strategies, including a vaccine. We compared phenotypic and genetic variation in HIV-1 env genes from subjects in acute/early infection and subjects with chronic infections in the context of subtype C heterosexual transmission. We found that the transmitted viruses all used CCR5 and required high levels of CD4 to infect target cells, suggesting selection for replication in T cells and not macrophages after transmission. In addition, the transmitted viruses were more likely to use a maraviroc-sensitive conformation of CCR5, perhaps identifying a feature of the target T cell. We confirmed an earlier observation that the transmitted viruses were, on average, modestly underglycosylated relative to the viruses from chronically infected subjects. This difference was most pronounced in comparing the viruses in acutely infected men to those in chronically infected women. These features of the transmitted virus point to selective pressures during the transmission event. We did not observe a consistent difference either in heterologous neutralization sensitivity or in sensitivity to soluble CD4 between the two groups, suggesting similar conformations between viruses from acute and chronic infection. However, the presence or absence of glycosylation sites had differential effects on neutralization sensitivity for different antibodies. We suggest that the occasional absence of glycosylation sites encoded in the conserved regions of env, further reduced in transmitted viruses, could expose specific surface structures on the protein as antibody targets.
    Journal of Virology 04/2013; 87(13):7218-33. · 5.08 Impact Factor
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    ABSTRACT: OBJECTIVE(S):: There is limited information on full-length genome sequences and the early evolution of transmitted HIV-1 subtype C viruses, which constitute the majority of viruses spread in Africa. The purpose of this study was to characterize the earliest changes across the genome of subtype C viruses following transmission, to better understand early control of viremia. DESIGN:: We derived the near full-length genome sequence responsible for clinical infection from five HIV subtype C-infected individuals with different disease progression profiles and tracked adaptation to immune responses in the first 6 months of infection. METHODS:: Near full-length genomes were generated by single genome amplification and direct sequencing. Sequences were analyzed for amino acid mutations associated with cytotoxic T lymphocyte (CTL) or antibody-mediated immune pressure, and for reversion. RESULTS:: Fifty-five sequence changes associated with adaptation to the new host were identified, with 38% attributed to CTL pressure, 35% to antibody pressure, 16% to reversions and the remainder were unclassified. Mutations in CTL epitopes were most frequent in the first 5 weeks of infection, with the frequency declining over time with the decline in viral load. CTL escape predominantly occurred in nef, followed by pol and env. Shuffling/toggling of mutations was identified in 81% of CTL epitopes, with only 7% reaching fixation within the 6-month period. CONCLUSION:: There was rapid virus adaptation following transmission, predominantly driven by CTL pressure, with most changes occurring during high viremia. Rapid escape and complex escape pathways provide further challenges for vaccine protection.
    AIDS (London, England) 02/2013; 27(4):507-518. · 4.91 Impact Factor
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    ABSTRACT: Broadly cross-neutralizing (BCN) antibodies are likely to be critical for an effective HIV vaccine. However the ontogeny of such antibodies, and their relationship with autologous viral evolution is unclear. Here we characterized viral evolution in CAP256, a subtype C infected individual who developed potent BCN antibodies targeting R166 and K169 in the V2 region. CAP256 was superinfected at 3 months post-infection with a virus that was highly sensitive to BCN V2-dependent monoclonal antibodies. The autologous neutralizing response in CAP256 was directed at V1V2, reaching extremely high titers (>1:40,000) against the superinfecting virus, at 42 weeks, just 11 weeks prior to the development of the BCN response targeting the same region. Recombination between the primary and superinfecting viruses, especially in V2 and gp41, resulted in two distinct lineages by 4 years post-infection. Although neutralization of some CAP256 clones by plasma from as much as 2 years earlier suggested incomplete viral escape, nonetheless titers against later clones were reduced at least 40-fold to less than 1:1,000. Escape mutations were identified in each lineage, either at R166 or at K169, suggesting that strain-specific and BCN antibodies targeted overlapping epitopes. Furthermore, the early dependence of CAP256 neutralizing antibodies on the N160 glycan decreased with the onset of neutralization breadth, indicating a change in specificity. These data suggest rapid maturation, within 11 weeks, of CAP256 strain-specific antibodies to acquire breadth, with implications for the vaccine elicitation of BCN V2-dependent antibodies. Overall these studies demonstrate ongoing viral escape is possible, even from BCN antibodies.
    Journal of Virology 02/2013; · 5.08 Impact Factor
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    ABSTRACT: BACKGROUND: Cameroon, in west central Africa, has an extraordinary degree of HIV diversity, presenting a major challenge for the development of an effective HIV vaccine. Given the continuing need to closely monitor the emergence of new HIV variants in the country, we analyzed HIV-1 genetic diversity in 59 plasma samples from HIV-infected Cameroonian blood donors. Full length HIV gag and nef sequences were generated and phylogenetic analyses were performed. FINDINGS: All gag and nef sequences clustered within HIV-1M. Circulating recombinant form CRF02_AG predominated, accounting for 50% of the studied infections, followed by clade G (11%), clade D and CRF37_cpx (4% each), and clades A, F, CRF01_AE and CRF36_cpx (2% each). In addition, 22% of the studied viruses apparently had nef and gag genes from viruses belonging to different clades, with the majority (8/10) having either a nef or gag gene derived from CRF02_AG. Interestingly, five gag sequences (10%) and three (5%) nef sequences were neither obviously recombinant nor easily classifiable into any of the known HIV-1M clades. CONCLUSION: This suggests the widespread existence of highly divergent HIV lineages in Cameroon. While the genetic complexity of the Cameroonian HIV-1 epidemic has potentially serious implications for the design of biomedical interventions, detailed analyses of divergent Cameroonian HIV-1M lineages could be crucial for dissecting the earliest evolutionary steps in the emergence of HIV-1M.
    Virology Journal 01/2013; 10(1):29. · 2.09 Impact Factor
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    ABSTRACT: Prompt diagnosis of acute HIV infection (AHI) benefits the individual and provides opportunities for public health intervention. The aim of this study was to describe most common signs and symptoms of AHI, correlate these with early disease progression and develop a clinical algorithm to identify acute HIV cases in resource limited setting. 245 South African women at high-risk of HIV-1 were assessed for AHI and received monthly HIV-1 antibody and RNA testing. Signs and symptoms at first HIV-positive visit were compared to HIV-negative visits. Logistic regression identified clinical predictors of AHI. A model-based score was assigned to each predictor to create a risk score for every woman. Twenty-eight women seroconverted after a total of 390 person-years of follow-up with an HIV incidence of 7.2/100 person-years (95%CI 4.5-9.8). Fifty-seven percent reported ≥1 sign or symptom at the AHI visit. Factors predictive of AHI included age <25 years (OR = 3.2; 1.4-7.1), rash (OR = 6.1; 2.4-15.4), sore throat (OR = 2.7; 1.0-7.6), weight loss (OR = 4.4; 1.5-13.4), genital ulcers (OR = 8.0; 1.6-39.5) and vaginal discharge (OR = 5.4; 1.6-18.4). A risk score of 2 correctly predicted AHI in 50.0% of cases. The number of signs and symptoms correlated with higher HIV-1 RNA at diagnosis (r = 0.63; p<0.001). Accurate recognition of signs and symptoms of AHI is critical for early diagnosis of HIV infection. Our algorithm may assist in risk-stratifying individuals for AHI, especially in resource-limited settings where there is no routine testing for AHI. Independent validation of the algorithm on another cohort is needed to assess its utility further. Point-of-care antigen or viral load technology is required, however, to detect asymptomatic, antibody negative cases enabling early interventions and prevention of transmission.
    PLoS ONE 01/2013; 8(4):e62928. · 3.73 Impact Factor

Publication Stats

3k Citations
630.19 Total Impact Points


  • 2002–2014
    • University of KwaZulu-Natal
      • Centre for the AIDS Programme of Research in South Africa (CAPRISA)
      Port Natal, KwaZulu-Natal, South Africa
    • South African Medical Research Council
      Kaapstad, Western Cape, South Africa
    • Chris Hani Baragwanath Hospital
      Johannesburg, Gauteng, South Africa
  • 1995–2014
    • University of Cape Town
      • • Division of Medical Virology
      • • Institute of Infectious Disease & Molecular Medicine (IIDMM)
      • • Division of Cell Biology
      • • Faculty of Health Sciences
      • • Division of Medical Microbiology
      Kaapstad, Western Cape, South Africa
  • 2012
    • University of Adelaide
      Tarndarnya, South Australia, Australia
  • 2006–2012
    • University of the Witwatersrand
      • Perinatal HIV Research Unit
      Johannesburg, Gauteng, South Africa
  • 2002–2012
    • National Institute for Communicable Diseases
      Johannesburg, Gauteng, South Africa
  • 2011
    • Rutgers New Jersey Medical School
      • Public Health Research Institute
      Newark, New Jersey, United States
  • 2010
    • Ministry of Health & Social Welfare, Tanzania
      Dār es Salām, Dar es Salaam, Tanzania
    • Ludwig-Maximilian-University of Munich
      • Department of Infectious Diseases and Tropical Medicine
      München, Bavaria, Germany
  • 2009
    • University of North Carolina at Chapel Hill
      North Carolina, United States
  • 2007
    • Tulane University
      • Department of Pediatrics
      New Orleans, Louisiana, United States
    • Universität des Saarlandes
      • Institut für Virologie
      Saarbrücken, Saarland, Germany
    • National Institute of Allergy and Infectious Diseases
      Maryland, United States
  • 2002–2007
    • Duke University Medical Center
      • Department of Surgery
      Durham, NC, United States
  • 2001
    • University of the Free State
      Bloemfontein, Free State, South Africa
  • 1998–2001
    • Institute of Human Virology
      Maryland City, Maryland, United States