Carolyn Williamson

University of Cape Town, Kaapstad, Western Cape, South Africa

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Publications (150)753.98 Total impact

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    ABSTRACT: The integrin α4β7 mediates the trafficking of immune cells to the gut associated lymphoid tissue (GALT) and is an attachment factor for the HIV gp120 envelope glycoprotein. We developed a viral replication inhibition assay to more clearly evaluate the role of α4β7 in HIV infection and the contribution of viral and host factors. Replication of 60 HIV-1 subtype C viruses collected over time from 11 individuals in the CAPRISA cohort were partially inhibited by antibodies targeting α4β7. However, dependence on α4β7 for replication varied substantially among viral isolates from different individuals as well as over time in some individuals. Among 8 transmitted/founder (T/F) viruses, α4β7 reactivity was highest for viruses having P/SDI/V tri-peptide binding motifs. Mutation of T/F viruses that had LDI/L motifs to P/SDI/V resulted in greater α4β7 reactivity, whereas mutating P/SDI/V to LDI/L motifs was associated with reduced α4β7 binding. P/SDI/V motifs were more common among South African HIV subtype C viruses (35%) compared to subtype C viruses from other regions of Africa (<8%) and to other subtypes, due in part to a founder effect. In addition, individuals with bacterial vaginosis (BV) and who had higher concentrations of IL-7, IL-8 and IL-1α in the genital tract had T/F viruses with higher α4β7 dependence for replication, suggesting that viruses with P/SDI/V motifs may be preferentially transmitted in the presence of BV in this population. Collectively, these data suggest a role for α4β7 in HIV infection that is influenced by both viral and host factors including the sequence of the α4β7 binding motif, the cytokine milieu and BV in the genital tract. The higher frequency of P/SDI/V sequences among South African HIV-1 subtype C viruses may have particular significance for the role of α4β7 in this geographical region.
    Retrovirology 06/2015; 12(1):54. DOI:10.1186/s12977-015-0183-3 · 4.19 Impact Factor
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    ABSTRACT: Mutations in functionally constrained sites of the HIV Envelope (Env) can affect entry efficiency and are potential targets for vaccine and drug design. We investigated Du151, a dual-infected individual with rapid disease progression. At her death 19 months post infection (mpi), she was infected with a recombinant variant, which outgrew both parental viruses. We aimed to determine whether the recombinant virus had enhanced Env entry efficiency compared to the parental viruses and to identify the functional determinant. We generated 15 env clones at 1, 2, 8 and 19 mpi. Pseudovirus carrying a recombinant Env clone (PSV clone), C18 (19 mpi), had significantly higher entry efficiency compared to the parents, suggesting that the recombinant virus had enhanced fitness. To identify the functional determinant, we compared two recombinant PSV clones (C18 and C63) - differing in entry efficiency (two-fold) and by four and three amino acids in gp120 and gp41, respectively. The increased entry efficiency of a C18-gp41 PSV chimera indicated that the three amino acids in C18 gp41 region was involved (K658, G671 and F717). Site-directed mutagenesis of the three amino acids of C63 showed that a single amino acid mutation, R658K, increased pseudovirion entry efficiency. The introduction of R658 into two PSV clones (C1 and C18) decreased their entry efficiency, suggesting that R658 carries a fitness cost. Thus, our data suggest that a recombinant virus emerged at 19 mpi with enhanced Env entry efficiency. Therefore, K658 in gp41 could in part, be a contributing factor to the increased viral load and rapid disease progression of Du151.
    AIDS research and human retroviruses 04/2015; DOI:10.1089/AID.2014.0100 · 2.33 Impact Factor
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    ABSTRACT: Background: Women in Africa, especially young women, have very high human immunodeficiency virus (HIV) incidence rates that cannot be fully explained by behavioral risks. We investigated whether genital inflammation influenced HIV acquisition in this group. Methods: Twelve selected cytokines, including 9 inflammatory cytokines and chemokines (interleukin [IL]-1α, IL-1β, IL-6, tumor necrosis factor-α, IL-8, interferon-γ inducible protein-10 [IP-10], monocyte chemoattractant protein-1, macrophage inflammatory protein [MIP]-1α, MIP-1β), hematopoietic IL-7, and granulocyte macrophage colony-stimulating factor, and regulatory IL-10 were measured prior to HIV infection in cervicovaginal lavages from 58 HIV seroconverters and 58 matched uninfected controls and in plasma from a subset of 107 of these women from the Centre for the AIDS Programme of Research in South Africa 004 tenofovir gel trial. Results: HIV seroconversion was associated with raised genital inflammatory cytokines (including chemokines MIP-1α, MIP-1β, and IP-10). The risk of HIV acquisition was significantly higher in women with evidence of genital inflammation, defined by at least 5 of 9 inflammatory cytokines being raised (odds ratio, 3.2; 95% confidence interval, 1.3-7.9; P = .014). Genital cytokine concentrations were persistently raised (for about 1 year before infection), with no readily identifiable cause despite extensive investigation of several potential factors, including sexually transmitted infections and systemic cytokines. Conclusions: Elevated genital concentrations of HIV target cell-recruiting chemokines and a genital inflammatory profile contributes to the high risk of HIV acquisition in these African women.
    Clinical Infectious Diseases 04/2015; 61(2). DOI:10.1093/cid/civ298 · 8.89 Impact Factor
  • Carolyn Williamson · Ronald Swanstrom
    Proceedings of the National Academy of Sciences 03/2015; 112(12). DOI:10.1073/pnas.1502208112 · 9.67 Impact Factor
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    ABSTRACT: The relevance of superinfection as a model to identify correlates of protection against HIV depends on whether the superinfecting transmission resembles primary infection, which has not been established. Here, we characterize the genetic bottleneck in superinfected individuals for the first time. In all three cases, superinfection produced a spike in viral load and could be traced to a single, CCR5-tropic founder virus with shorter, less glycosylated variable regions than matched chronic viruses. These features are consistent with primary HIV transmission and provide support for the use of superinfection as a model to address correlates of protection against HIV. © The Author 2015. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail:
    The Journal of Infectious Diseases 03/2015; 212(6). DOI:10.1093/infdis/jiv136 · 6.00 Impact Factor
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    Penny L Moore · Carolyn Williamson · Lynn Morris
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    ABSTRACT: The development of a preventative HIV-1 vaccine remains a global public health priority. This will likely require the elicitation of broadly neutralizing antibodies (bNAbs) able to block infection by diverse viral strains from across the world. Understanding the pathway to neutralization breadth in HIV-1 infected humans will provide insights into how bNAb lineages arise, a process that probably involves a combination of host and viral factors. Here, we focus on the role of viral characteristics and evolution in shaping bNAbs during HIV-1 infection, and describe how these findings may be translated into novel vaccine strategies. Copyright © 2015. Published by Elsevier Ltd.
    Trends in Microbiology 01/2015; 23(4). DOI:10.1016/j.tim.2014.12.007 · 9.19 Impact Factor
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    ABSTRACT: The sequence diversity of human immunodeficiency virus type 1 (HIV-1) presents a formidable challenge to the generation of an HIV-1 vaccine. One strategy to address such sequence diversity and to improve the magnitude of neutralizing antibodies (NAbs) is to utilize multivalent mixtures of HIV-1 envelope (Env) immunogens. Here we report the generation and characterization of three novel, acute clade C HIV-1 Env gp140 trimers (459C, 405C and 939C), each with unique antigenic properties. Among the single trimers tested, 459C elicited the most potent NAb responses in vaccinated guinea pigs. We evaluated the immunogenicity of various mixtures of clade C Env trimers and found that a quadrivalent cocktail of clade C trimers elicited a greater magnitude of NAbs against a panel of Tier 1A and 1B viruses than any single clade C trimer alone, demonstrating that the mixture had an advantage over all individual components of the cocktail. These data suggest that vaccination with a mixture of clade C Env trimers represents a promising strategy to augment vaccine-elicited NAb responses. It is currently not known how to potent generate neutralizing antibodies (NAbs) to the diversity of circulating HIV-1 envelopes (Env) by vaccination. One strategy to address this diversity is to utilize mixtures of different soluble HIV-1 envelope proteins. In this study, we generated and characterized three distinct, novel acute clade C soluble trimers. We vaccinated guinea pigs with single trimers as well as mixtures of trimers, and we found that a mixture of four trimers elicited a greater magnitude of NAbs than any single trimer within the mixture. The results of this study suggest that further development of Env trimer cocktails is warranted. Copyright © 2014, American Society for Microbiology. All Rights Reserved.
    Journal of Virology 12/2014; 89(5). DOI:10.1128/JVI.03331-14 · 4.44 Impact Factor
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    ABSTRACT: The development of a panel of mucosally transmissible simian-human immunodeficiency virus (SHIV) challenge stocks from multiple virus clades would facilitate preclinical evaluation of candidate HIV-1 vaccines and therapeutics. The majority of SHIV stocks that have been generated to date have been derived from clade B HIV-1 env sequences from viruses isolated during chronic infection and typically required serial animal-to-animal adaption for establishing mucosal transmissibility and pathogenicity. To capture essential features of mucosal transmission of clade C viruses, we produced a series of SHIVs with early clade C HIV-1 env sequences from acutely HIV-1-infected individuals from South Africa. SHIV-327c and SHIV-327cRM expressed env sequences that were 99.7-100% identical to the original HIV-1 isolate and did not require in vivo passaging for mucosal infectivity. These challenge stocks infected rhesus monkeys efficiently by both intrarectal and intravaginal routes, replicated to high levels during acute infection, and established chronic setpoint viremia in 13 of 17 (76%) infected animals. The SHIV-327cRM challenge stock was also titrated for both single, high-dose intrarectal challenges and repetitive, low-dose intrarectal challenges in rhesus monkeys. These SHIV challenge stocks should facilitate the preclinical evaluation of vaccines and other interventions aimed at preventing clade C HIV-1 infection. We describe the development of two related clade C SHIV challenge stocks. These challenge stocks should prove useful for preclinical testing of vaccines and other interventions aimed at preventing clade C HIV-1 infection. Copyright © 2014, American Society for Microbiology. All Rights Reserved.
    Journal of Virology 12/2014; 89(4). DOI:10.1128/JVI.03279-14 · 4.44 Impact Factor
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    ABSTRACT: To investigate whether distinct populations have differing human immunodeficiency virus type 1 (HIV) neutralizing antibody responses, we compared 20 women from Tanzania's HIV Superinfection Study (HISIS) cohort, who were infected multiple HIV subtypes, and 22 women from the Centre for the AIDS Programme of Research in South Africa (CAPRISA) cohort, who were infected exclusively with HIV subtype C. By 2 years after infection, 35% of HISIS subjects developed neutralization breadth, compared with 9% of CAPRISA subjects (P = .0131). Cumulative viral loads between 3 and 12 months were higher in the HISIS group (P = .046) and strongly associated with breadth (P < .0001). While viral load was the strongest predictor, other factors may play a role, as the odds of developing breadth remained higher in HISIS even after correction for viral load.
    The Journal of Infectious Diseases 11/2014; 211(9). DOI:10.1093/infdis/jiu633 · 6.00 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 11/2014; s 468–470:214–225. DOI:10.1016/j.virol.2014.08.009 · 3.32 Impact Factor
  • AIDS Research and Human Retroviruses 10/2014; 30 Suppl 1(S1):A34. DOI:10.1089/aid.2014.5053.abstract · 2.33 Impact Factor
  • AIDS research and human retroviruses; 10/2014
  • AIDS Research and Human Retroviruses 10/2014; 30 Suppl 1(S1):A226. DOI:10.1089/aid.2014.5496.abstract · 2.33 Impact Factor
  • AIDS research and human retroviruses; 10/2014
  • AIDS Research and Human Retroviruses 10/2014; 30 Suppl 1(S1):A56. DOI:10.1089/aid.2014.5099.abstract · 2.33 Impact Factor
  • AIDS research and human retroviruses; 10/2014
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    ABSTRACT: BACKGROUND: While antiretroviral pre-exposure prophylaxis (PrEP) prevents HIV acquisition, it is not known if it alters HIV disease progression. This study assesses whether tenofovir gel impacted on disease progression among CAPRISA 004 microbicide trial seroconvertors. METHODS: Eighty-three seroconvertors from the tenofovir and placebo gel arms of the CAPRISA 004 trial were monitored prospectively for a minimum two years by CD4 count and viral load (VL). Linear mixed models were fitted to HIV VL, and log rank test was used to compare time to reach CD4<350. RESULTS: Median 2-week post-infection VL was 4.74 and 4.45 log copies/ml in women assigned to tenofovir gel (n=32) and placebo gel (n=51) (p=0.189). Corresponding 12-month post-infection VLs were 4.24 and 3.70 log copies/ml (p=0.016). After adjusting for clinical and behavioral characteristics and protective HLA alleles, mean VLs within the first two years were 4.51 and 4.02 log copies/ml in women from the tenofovir and placebo arms (p=0.013). Among women with vaginal tenofovir measurements, mean VL were 4.53 and 4.60 log copies/ml in those with detectable versus undetectable levels (p=0.840). Overall mean CD4 counts were 463 and 514 cells/µl in women assigned to tenofovir and placebo (p=0.290). Thirty-two (38.6%) women reached CD4<350 at median 9.4 months post-infection, 13 (40.6%) from the tenofovir and 19 (37.3%) from the placebo arms (p=0.786). CONCLUSIONS: Tenofovir gel had no impact on post-infection CD4 counts or the rate of CD4 decline. While seroconvertors from the tenofovir arm experienced higher VLs, this did not result in a need for earlier antiretroviral therapy.
    JAIDS Journal of Acquired Immune Deficiency Syndromes 09/2014; 68(1). DOI:10.1097/QAI.0000000000000367 · 4.56 Impact Factor
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    ABSTRACT: Unlabelled: 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 United States, 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 plasma samples 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. Importance: An effective HIV-1 vaccine will need to overcome the extraordinary variability of the virus, which is most pronounced in the envelope glycoproteins (Env), which are the sole targets for neutralizing antibodies (nAbs). Distinct genetic lineages, or clades, of HIV-1 occur in different locales that may require special consideration when designing and testing vaccines candidates. We show that nAb responses to HIV-1 infection are generally active across clades but are most potent within clades. Because effective vaccine-induced nAbs are likely to share these properties, optimal coverage of a particular clade or combination of clades may require clade-matched immunogens. Optimal within-clade coverage might be easier to achieve in regions such as China and Thailand, where the epidemic is more recent and the virus less diverse than in southern Africa, the United States, and Europe. Finally, features of the first and second hypervariable regions of gp120 (V1V2) may be critical for optimal vaccine design.
    Journal of Virology 08/2014; 88(21). DOI:10.1128/JVI.01705-14 · 4.44 Impact Factor
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    ABSTRACT: Objectives 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. Methods HIV-uninfected women (n=227) were screened for BV, Chlamydia trachomatis, Neisseria gonorrhoeae, Herpes simplex virus type 2 (HSV-2), and Trichomonas vaginalis. Concentrations of 42 cytokines in cervicovaginal lavages and 13 cytokines in plasma were measured using Luminex. Changes in cytokine profiles were evaluated using Mann–Whitney U test, logistic regression and factor analysis. p Values were adjusted for multiple comparisons using a false discovery rate step-down procedure. Results Women with chlamydia or gonorrhoea had the highest genital cytokine concentrations, with 17/42 and 14/42 cytokines upregulated compared with women with no infection, respectively. BV was associated with elevated proinflammatory cytokine concentrations, but lower chemokine and haematopoietic cytokine concentrations. HSV-2 reactivation was associated with lower levels of inflammation, while trichomoniasis did not cause significant differences in genital cytokine concentrations. Genital infections did not influence plasma cytokine concentrations. Although certain STIs, in particular chlamydia and gonorrhoea, were associated with high genital cytokine concentrations, only 19% of women with an STI/BV had clinical signs. Conclusions Chlamydia was associated with the highest genital cytokine levels, followed by gonorrhoea, HSV-2, trichomoniasis, and BV. In regions where HIV is prevalent and STIs are managed syndromically, better STI/BV screening is urgently needed, as certain infections were found to be highly inflammatory.
    Sexually Transmitted Infections 08/2014; 90(8). DOI:10.1136/sextrans-2014-051601 · 3.40 Impact Factor
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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; 30(10). DOI:10.1089/AID.2014.0110 · 2.33 Impact Factor

Publication Stats

5k Citations
753.98 Total Impact Points


  • 1995–2015
    • University of Cape Town
      • • Institute of Infectious Disease & Molecular Medicine (IIDMM)
      • • Division of Medical Virology
      • • Faculty of Health Sciences
      • • Department of Clinical Laboratory Sciences
      • • Division of Medical Microbiology
      • • Department of Medicine
      Kaapstad, Western Cape, South Africa
  • 2012–2014
    • University of KwaZulu-Natal
      • Centre for the AIDS Programme of Research in South Africa (CAPRISA)
      Port Natal, KwaZulu-Natal, South Africa
    • Columbia University
      • Department of Epidemiology
      New York, New York, United States
  • 2009
    • University of North Carolina at Chapel Hill
      North Carolina, United States
  • 2007
    • Tulane University
      • Department of Pediatrics
      New Orleans, Louisiana, United States
  • 2006
    • University of the Witwatersrand
      • Perinatal HIV Research Unit
      Johannesburg, Gauteng, South Africa
  • 2002
    • Duke University Medical Center
      • Department of Surgery
      Durham, North Carolina, United States
    • National Institute for Communicable Diseases
      • Centre for HIV & Sexually Transmitted Infections
      Johannesburg, Gauteng, South Africa
  • 2001
    • University of the Free State
      Bloemfontein, Free State, South Africa
    • Institute of Human Virology
      Maryland City, Maryland, United States