Browsing by Author "Ngandu, Nobubelo K."

Now showing 1 - 8 of 8

Brief report: selection of HIV-1 variants with higher transmission potential by 1% tenofovir gel microbicide.
(Wolters Kluwer Health., 2017) Ngandu, Nobubelo K.; Carlson, Jonathan M.; Chopera, Denis Rutendo.; Ndabambi, Nonkululeko.; Abdool Karim, Quarraisha.; Abdool Karim, Salim Safurdeen.; Williamson, Carolyn.
Abstract available in pdf.
Comparison of viral env proteins from acute and chronic infections with subtype C human immunodeficiency virus type 1 identifies differences in glycosylation and CCR5 utilization and suggests a new strategy for immunogen design.
(American Society for Microbiology., 2013) Ping, Li-Hua.; Joseph, Sarah B.; Anderson, Jeffrey A.; Abrahams, Melissa-Rose.; Salazar-Gonzalez, Jesus F.; Kincer, Laura P.; Treurnicht, Florette K.; Arney, Leslie.; Ojeda, Suany.; Zhang, Ming.; Keys, Jessica.; Potter, E. Lake.; Chu, Haitao.; Moore, Penelope L.; Salazar-Gonzalez, Maria.; Iyer, Shilpa.; Jabara, Cassandra.; Kirchherr, Jennifer.; Mapanje, Clement.; Ngandu, Nobubelo K.; Seoighe, Cathal.; Hoffman, Irving F.; Gao, Feng.; Tang, Yuyang.; Labranche, Celia.; Lee, Benhur.; Saville, Andrew.; Vermeulen, Marion.; Fiscus, Susan A.; Morris, Lynn.; Abdool Karim, Salim Safurdeen.; Haynes, Barton F.; Shaw, George M.; Korber, Bette T. M.; Hahn, Beatrice H.; Cohen, Myron S.; Montefiori, David Charles.; Williamson, Carolyn.; Swanstrom, Ronald.
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 under-glycosylated 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.
Evolution of an HIV glycan–dependent broadly neutralizing antibody epitope through immune escape.
(Nature Publishing Group., 2012) Moore, Penelope L.; Gray, Elin Solomonovna.; Wibmer, Constantinos Kurt.; Bhiman, Jinal N.; Nonyane, Molati.; Hermanus, Tandile.; Sheward, Daniel J.; Bajimaya, Shringkhala.; Abrahams, Melissa-Rose.; Tumba, Nancy Lola.; Ping, Li-Hua.; Ngandu, Nobubelo K.; Abdool Karim, Quarraisha.; Abdool Karim, Salim Safurdeen.; Swanstrom, Ronald.; Seaman, Michael S.; Williamson, Carolyn.; Morris, Lynn.;
Neutralizing antibodies are likely to play a crucial part in a preventative HIV-1 vaccine. Although efforts to elicit broadly cross-neutralizing (BCN) antibodies by vaccination have been unsuccessful, a minority of individuals naturally develop these antibodies after many years of infection. How such antibodies arise, and the role of viral evolution in shaping these responses, is unknown. Here we show, in two HIV-1–infected individuals who developed BCN antibodies targeting the glycan at Asn332 on the gp120 envelope, that this glycan was absent on the initial infecting virus. However, this BCN epitope evolved within 6 months, through immune escape from earlier strain-specific antibodies that resulted in a shift of a glycan to position 332. Both viruses that lacked the glycan at amino acid 332 were resistant to the Asn332-dependent BCN monoclonal antibody PGT128 (ref. 8), whereas escaped variants that acquired this glycan were sensitive. Analysis of large sequence and neutralization data sets showed the 332 glycan to be significantly under-represented in transmitted subtype C viruses compared to chronic viruses, with the absence of this glycan corresponding with resistance to PGT128. These findings highlight the dynamic interplay between early antibodies and viral escape in driving the evolution of conserved BCN antibody epitopes.
Human immunodeficiency virus-specific gamma interferon enzyme-linked immunospot assay responses targeting specific regions of the proteome during primary subtype C infection are poor predictors of the course of viremia and set point.
(American Society for Microbiology., 2008) Gray, Clive M.; Mlotshwa, Mandla.; Riou, Catherine.; Mathebula, Tiyani.; Mashishi, Tumelo.; Seoighe, Cathal.; Ngandu, Nobubelo K.; de Assis Rosa, Debra.; van Loggerenberg, Francois.; Morris, Lynn.; Mlisana, Koleka Patience.; Williamson, Carolyn.; Abdool Karim, Salim Safurdeen.
It is unknown whether patterns of human immunodeficiency virus (HIV)-specific T-cell responses during acute infection may influence the viral set point and the course of disease. We wished to establish whether the magnitude and breadth of HIV type 1 (HIV-1)-specific T-cell responses at 3 months postinfection were correlated with the viral-load set point at 12 months and hypothesized that the magnitude and breadth of HIV-specific T-cell responses during primary infection would predict the set point. Gamma interferon (IFN-γ) enzyme-linked immunospot (ELISPOT) assay responses across the complete proteome were measured in 47 subtype C HIV-1-infected participants at a median of 12 weeks postinfection. When corrected for amino acid length and individuals responding to each region, the order of recognition was as follows: Nef > Gag > Pol > Rev > Vpr > Env > Vpu > Vif > Tat. Nef responses were significantly (P < 0.05) dominant, targeted six epitopic regions, and were unrelated to the course of viremia. There was no significant difference in the magnitude and breadth of responses for each protein region with disease progression, although there was a trend of increased breadth (mean, four to seven pools) in rapid progressors. Correlation of the magnitude and breadth of IFN-γ responses with the viral set point at 12 months revealed almost zero association for each protein region. Taken together, these data demonstrate that the magnitude and breadth of IFN-γ ELISPOT assay responses at 3 months postinfection are unrelated to the course of disease in the first year of infection and are not associated with, and have low predictive power for, the viral set point at 12 months.
Identification of broadly neutralizing antibody epitopes in 1 the HIV-1 envelope glycoprotein using evolutionary models.
(Virology Journal, 2013) Lacerda, Miguel.; Moore, Penelope L.; Ngandu, Nobubelo K.; Seaman, Michael.; Gray, Elin Solomonovna.; Murrell, Ben.; Krishnamoorthy, Mohan.; Nonyane, Molati.; Madiga, Maphuti C.; Wibmer, Constantinos Kurt.; Sheward, Daniel J.; Bailer, Robert T.; Gao, Hongmei.; Greene, Kelli M.; Abdool Karim, Salim Safurdeen.; Mascola, John R.; Korber, Bette T. M.; Montefiori, David Charles.; Morris, Lynn.; Williamson, Carolyn.; Seoighe, Cathal.
Background: 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. Methods: 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. Results: 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. Conclusions: 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.
Intersubtype differences in the effect of a rare p24 Gag mutation on HIV-1 replicative fitness.
(American Society for Microbiology., 2012) Chopera, Denis Rutendo.; Cotton, Laura A.; Zawaira, Alexander.; Mann, Jaclyn Kelly.; Ngandu, Nobubelo K.; Ntale, Roman.; Carlson, Jonathan M.; Mlisana, Koleka Patience.; Woodman, Zenda.; de Assis Rosa, Debra.; Martin, Eric.; Miura, Toshiyuki.; Pereyra, Florencia.; Walker, Bruce D.; Gray, Clive M.; Martin, Darren Patrick.; Ndung'u, Peter Thumbi.; Brockman, Mark A.; Abdool Karim, Salim Safurdeen.; Brumme, Zabrina L.; Williamson, Carolyn.
Certain immune-driven mutations in HIV-1, such as those arising in p24Gag, decrease viral replicative capacity. However, the intersubtype differences in the replicative consequences of such mutations have not been explored. In HIV-1 subtype B, the p24Gag M250I mutation is a rare variant (0.6%) that is enriched among elite controllers (7.2%) (P 0.0005) and appears to be a rare escape variant selected by HLA-B58 supertype alleles (P<0.01). In contrast, in subtype C, it is a relatively common minor polymorphic variant (10 to 15%) whose appearance is not associated with a particular HLA allele. Using site-directed mutant viruses, we demonstrate that M250I reduces in vitro viral replicative capacity in both subtype B and subtype C sequences. However, whereas in subtype C downstream compensatory mutations at p24Gag codons 252 and 260 reduce the adverse effects of M250I, fitness costs in subtype B appear difficult to restore. Indeed, patient-derived subtype B sequences harboring M250I exhibited in vitro replicative defects, while those from subtype C did not. The structural implications of M250I were predicted by protein modeling to be greater in subtype B versus C, providing a potential explanation for its lower frequency and enhanced replicative defects in subtype B. In addition to accounting for genetic differences between HIV-1 subtypes, the design of cytotoxic-T-lymphocyte-based vaccines may need to account for differential effects of host-driven viral evolution on viral fitness.
Rapid, complex adaption of transmitted HIV-1 full-length genomes in subtype C-infected individuals with differing disease progression.
(Wolters Kluwer Health., 2013) Abrahams, Melissa-Rose.; Treurnicht, Florette K.; Ngandu, Nobubelo K.; Goodier, Sarah A.; Marais, Jinny C.; Bredell, Helba.; Thebus, Ruwayhida.; de Assis Rosa, Debra.; Seoighe, Cathal.; Abdool Karim, Salim Safurdeen.; Gray, Clive M.; Williamson, Carolyn.; Mlisana, Koleka Patience.
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.
Temporal association of HLA-B*81:01- and HLA-B*39:10-mediated HIV-1 p24 sequence evolution with disease progression.
(American Society for Microbiology., 2012) Ntale, Roman.; Chopera, Denis Rutendo.; Ngandu, Nobubelo K.; de Assis Rosa, Debra.; Zembe, Lycias.; Gamieldien, Hoyam.; Mlotshwa, Mandla.; Werner, Lise.; Woodman, Zenda.; Mlisana, Koleka Patience.; Abdool Karim, Salim Safurdeen.; Gray, Clive M.; Williamson, Carolyn.
HLA-B*81:01 and HLA-B*39:10 alleles have been associated with viremic control in HIV-1 subtype C infection. Both alleles restrict the TL9 epitope in p24 Gag, and cytotoxic-T-lymphocyte (CTL)-mediated escape mutations in this epitope have been associated with an in vitro fitness cost to the virus. We investigated the timing and impact of mutations in the TL9 epitope on disease progression in five B*81:01- and two B*39:10-positive subtype C-infected individuals. Whereas both B*39:10 participants sampled at 2 months postinfection had viruses with mutations in the TL9 epitope, in three of the five (3/5) B*81:01 participants, TL9 escape mutations were only detected 10 months after infection, taking an additional 10 to 15 months to reach fixation. In the two remaining B*81:01 individuals, one carried a TL9 escape variant at 2 weeks postinfection, whereas no escape mutations were detected in the virus from the other participant for up to 33 months postinfection, despite CTL targeting of the epitope. In all participants, escape mutations in TL9 were linked to coevolving residues in the region of Gag known to be associated with host tropism. Late escape in TL9, together with coevolution of putative compensatory mutations, coincided with a spontaneous increase in viral loads in two individuals who were otherwise controlling the infection. These results provide in vivo evidence of the detrimental impact of B*81:01-mediated viral evolution, in a single Gag p24 epitope, on the control of viremia.