Zembe L.,University of Cape Town |
Burgers W.A.,University of Cape Town |
Jaspan H.B.,University of Cape Town |
Jaspan H.B.,The Desmond Tutu Center |
And 11 more authors.
PLoS ONE | Year: 2011
The genetic diversity of HIV-1 across the globe is a major challenge for developing an HIV vaccine. To facilitate immunogen design, it is important to characterize clusters of commonly targeted T-cell epitopes across different HIV clades. To address this, we examined 39 HIV-1 clade C infected individuals for IFN-γ Gag-specific T-cell responses using five sets of overlapping peptides, two sets matching clade C vaccine candidates derived from strains from South Africa and China, and three peptide sets corresponding to consensus clades A, B, and D sequences. The magnitude and breadth of T-cell responses against the two clade C peptide sets did not differ, however clade C peptides were preferentially recognized compared to the other peptide sets. A total of 84 peptides were recognized, of which 19 were exclusively from clade C, 8 exclusively from clade B, one peptide each from A and D and 17 were commonly recognized by clade A, B, C and D. The entropy of the exclusively recognized peptides was significantly higher than that of commonly recognized peptides (p = 0.0128) and the median peptide processing scores were significantly higher for the peptide variants recognized versus those not recognized (p = 0.0001). Consistent with these results, the predicted Major Histocompatibility Complex Class I IC 50 values were significantly lower for the recognized peptide variants compared to those not recognized in the ELISPOT assay (p<0.0001), suggesting that peptide variation between clades, resulting in lack of cross-clade recognition, has been shaped by host immune selection pressure. Overall, our study shows that clade C infected individuals recognize clade C peptides with greater frequency and higher magnitude than other clades, and that a selection of highly conserved epitope regions within Gag are commonly recognized and give rise to cross-clade reactivities. © 2011 Zembe et al. Source
Tongo M.,University of Cape Town |
Tongo M.,Institute of Medical Research and Study of Medicinal Plants |
Zembe L.,University of Cape Town |
Ebong E.,Institute of Medical Research and Study of Medicinal Plants |
And 6 more authors.
Vaccine | Year: 2014
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 (11/38) of peptides commonly recognized in Gag. 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. © 2014 Elsevier Ltd. Source
Amico K.R.,University of Michigan |
Wallace M.,The Desmond Tutu Center |
Roux S.,The Desmond Tutu Center |
Atujuna M.,The Desmond Tutu Center |
And 4 more authors.
AIDS and Behavior | Year: 2016
Placebo-controlled trials of pre-exposure prophylaxis (PrEP) have reported challenges with study-product uptake and use, with the greatest challenges reported in studies with young women in sub-Saharan Africa. We conducted a qualitative sub-study to explore experiences with open-label PrEP among young women in Cape Town, South Africa participating in HTPN 067/Alternative Dosing to Augment Pre-Exposure Prophylaxis Pill Taking (ADAPT). HPTN 067/ADAPT provided open label oral FTC/TDF PrEP to young women in Cape Town, South Africa who were randomized to daily and non-daily PrEP regimens. Following completion of study participation, women were invited into a qualitative sub-study including focus groups and in-depth interviews. Interviews and groups followed a semi-structured guide, were recorded, transcribed, and translated to English from isiXhosa, and coded using framework analysis. Sixty of the 179 women enrolled in HPTN 067/ADAPT participated in either a focus group (six groups for a total of 42 participants) or an in-depth interview (n = 18). This sample of mostly young, unmarried women identified facilitators of and barriers to PrEP use, as well as factors influencing study participation. Cross-cutting themes characterizing discourse suggested that women placed high value on contributing to the well-being of one’s community (Ubuntu), experienced a degree of skepticism towards PrEP and the study more generally, and reported a wide range of approaches towards PrEP (ranging from active avoidance to high levels of persistence and adherence). A Mutuality Framework is proposed that identifies four dynamics (distrust, uncertainty, alignment, and mutuality) that represent distinct interactions between self, community and study and serve to contextualize women’s experiences. Implications for better understanding PrEP use, and non-use, and intervention opportunities are discussed. In this sample of women, PrEP use in the context of an open-label research trial was heavily influenced by underlying beliefs about safety, reciprocity of contributions to community, and trust in transparency and integrity of the research. Greater attention to factors positioning women in the different dynamics of the proposed Mutuality Framework could direct intervention approaches in clinical trials, as well as open-label PrEP scale-up. © 2016 The Author(s) Source