Anthony Ogwu

Adaptation of HIV-1 to human leukocyte antigen class I

The rapid and extensive spread of the human immunodeficiency virus (HIV) epidemic provides a rare opportunity to witness host–pathogen co-evolution involving humans. A focal point is the interaction between genes encoding human leukocyte antigen (HLA) and those encoding HIV proteins. HLA molecules present fragments (epitopes) of HIV proteins on the surface of infected cells to enable immune recognition and killing by CD8+ T cells; particular HLA molecules, such as HLA-B*57, HLA-B*27 and HLA-B*51, are more likely to mediate successful control of HIV infection. Mutation within these epitopes can allow viral escape from CD8+ T-cell recognition. Here we analysed viral sequences and HLA alleles from >2,800 subjects, drawn from 9 distinct study cohorts spanning 5 continents. Initial analysis of the HLA-B*51-restricted epitope, TAFTIPSI (reverse transcriptase residues 128–135), showed a strong correlation between the frequency of the escape mutation I135X and HLA-B*51 prevalence in the 9 study cohorts (P = 0.0001). Extending these analyses to incorporate other well-defined CD8+ T-cell epitopes, including those restricted by HLA-B*57 and HLA-B*27, showed that the frequency of these epitope variants (n = 14) was consistently correlated with the prevalence of the restricting HLA allele in the different cohorts (together, P < 0.0001), demonstrating strong evidence of HIV adaptation to HLA at a population level. This process of viral adaptation may dismantle the well-established HLA associations with control of HIV infection that are linked to the availability of key epitopes, and highlights the challenge for a vaccine to keep pace with the changing immunological landscape presented by HIV.

Highly Active Antiretroviral Therapy and Adverse Birth Outcomes Among HIV-Infected Women in Botswana

BACKGROUND It is unknown whether adverse birth outcomes are associated with maternal highly active antiretroviral therapy (HAART) in pregnancy, particularly in resource-limited settings. METHODS We abstracted obstetrical records at 6 sites in Botswana for 24 months. Outcomes included stillbirths (SBs), preterm delivery (PTD), small for gestational age (SGA), and neonatal death (NND). Among human immunodeficiency virus (HIV)-infected women, comparisons were limited to HAART exposure status at conception, and those with similar opportunities for outcomes. Comparisons were adjusted for CD4(+) lymphocyte cell count. RESULTS Of 33,148 women, 32,113 (97%) were tested for HIV, of whom 9504 (30%) were HIV infected. Maternal HIV was significantly associated with SB, PTD, SGA, and NND. Compared with all other HIV-infected women, those continuing HAART from before pregnancy had higher odds of PTD (adjusted odds ratio [AOR], 1.2; 95% confidence interval [CI], 1.1, 1.4), SGA (AOR, 1.8; 95% CI, 1.6, 2.1) and SB (AOR, 1.5; 95% CI, 1.2, 1.8). Among women initiating antiretroviral therapy in pregnancy, HAART use (vs zidovudine) was associated with higher odds of PTD (AOR, 1.4; 95% CI, 1.2, 1.8), SGA (AOR, 1.5; 95% CI, 1.2, 1.9), and SB (AOR, 2.5; 95% CI, 1.6, 3.9). Low CD4(+) was independently associated with SB and SGA, and maternal hypertension during pregnancy with PTD, SGA, and SB. CONCLUSIONS HAART receipt during pregnancy was associated with increased PTD, SGA, and SB.

Increased Risk of Preterm Delivery Among HIV-Infected Women Randomized to Protease Versus Nucleoside Reverse Transcriptase Inhibitor-Based HAART During Pregnancy

BACKGROUND Protease inhibitor (PI)-based highly active antiretroviral therapy (HAART) use in pregnancy has been associated with preterm deliveries in some observational studies. METHODS HIV-infected, HAART-naive pregnant women with CD4+ counts ≥200 cells/mm(3) were randomized between 26 and 34 weeks gestation to lopinavir/ritonavir/zidovudine/lamivudine (PI group) or abacavir/zidovudine/lamivudine (NRTI group) in a clinical trial to prevent mother-to-child HIV transmission. Risk factors for preterm delivery (<37 weeks) and differences by randomization arm were evaluated for live infants by logistic regression. RESULTS Preterm delivery rates were higher among 267 women in the PI group than 263 women in the NRTI group (21.4% vs 11.8%, P = .003). PI-based HAART was the most significant risk factor for preterm delivery [odds ratio = 2.03, 95% confidence interval 1.26-3.27, P = .004]. Mean change in maternal body mass index (BMI) 1 month after HAART initiation was lower in the PI group (P < .001); however, this was not significantly associated with preterm delivery. Neither infant hospitalizations nor mortality through 6 months of life differed by maternal regimen. CONCLUSIONS PI-based HAART was associated with increased preterm delivery but not increased infant hospitalizations or mortality in a clinical trial setting. The association between PI use and lower increase in BMI in late pregnancy warrants further study.

HLA-A*7401-mediated control of HIV viremia is independent of its linkage disequilibrium with HLA-B*5703.

The potential contribution of HLA-A alleles to viremic control in chronic HIV type 1 (HIV-1) infection has been relatively understudied compared with HLA-B. In these studies, we show that HLA-A*7401 is associated with favorable viremic control in extended southern African cohorts of >2100 C-clade–infected subjects. We present evidence that HLA-A*7401 operates an effect that is independent of HLA-B*5703, with which it is in linkage disequilibrium in some populations, to mediate lowered viremia. We describe a novel statistical approach to detecting additive effects between class I alleles in control of HIV-1 disease, highlighting improved viremic control in subjects with HLA-A*7401 combined with HLA-B*57. In common with HLA-B alleles that are associated with effective control of viremia, HLA-A*7401 presents highly targeted epitopes in several proteins, including Gag, Pol, Rev, and Nef, of which the Gag epitopes appear immunodominant. We identify eight novel putative HLA-A*7401–restricted epitopes, of which three have been defined to the optimal epitope. In common with HLA-B alleles linked with slow progression, viremic control through an HLA-A*7401–restricted response appears to be associated with the selection of escape mutants within Gag epitopes that reduce viral replicative capacity. These studies highlight the potentially important contribution of an HLA-A allele to immune control of HIV infection, which may have been concealed by a stronger effect mediated by an HLA-B allele with which it is in linkage disequilibrium. In addition, these studies identify a factor contributing to different HIV disease outcomes in individuals expressing HLA-B*5703.

HIV-1 Subtype C-Infected Individuals Maintaining High Viral Load as Potential Targets for the “Test-and-Treat” Approach to Reduce HIV Transmission

The first aim of the study is to assess the distribution of HIV-1 RNA levels in subtype C infection. Among 4,348 drug-naïve HIV-positive individuals participating in clinical studies in Botswana, the median baseline plasma HIV-1 RNA levels differed between the general population cohorts (4.1–4.2 log10) and cART-initiating cohorts (5.1–5.3 log10) by about one log10. The proportion of individuals with high (≥50,000 (4.7 log10) copies/ml) HIV-1 RNA levels ranged from 24%–28% in the general HIV-positive population cohorts to 65%–83% in cART-initiating cohorts. The second aim is to estimate the proportion of individuals who maintain high HIV-1 RNA levels for an extended time and the duration of this period. For this analysis, we estimate the proportion of individuals who could be identified by repeated 6- vs. 12-month-interval HIV testing, as well as the potential reduction of HIV transmission time that can be achieved by testing and ARV treating. Longitudinal analysis of 42 seroconverters revealed that 33% (95% CI: 20%–50%) of individuals maintain high HIV-1 RNA levels for at least 180 days post seroconversion (p/s) and the median duration of high viral load period was 350 (269; 428) days p/s. We found that it would be possible to identify all HIV-infected individuals with viral load ≥50,000 (4.7 log10) copies/ml using repeated six-month-interval HIV testing. Assuming individuals with high viral load initiate cART after being identified, the period of high transmissibility due to high viral load can potentially be reduced by 77% (95% CI: 71%–82%). Therefore, if HIV-infected individuals maintaining high levels of plasma HIV-1 RNA for extended period of time contribute disproportionally to HIV transmission, a modified “test-and-treat” strategy targeting such individuals by repeated HIV testing (followed by initiation of cART) might be a useful public health strategy for mitigating the HIV epidemic in some communities.

Effects of in utero antiretroviral exposure on longitudinal growth of HIV-exposed uninfected infants in Botswana

Background:The impact of in utero exposure to highly active antiretroviral therapy (HAART) on longitudinal growth of HIV-uninfected infants is unknown. Methods:The Mashi and Mma Bana PMTCT intervention trials enrolled HIV-infected pregnant women at four sites in Botswana. Breast-fed (BF), HIV-uninfected infants born at 37 weeks or greater were included in this analysis. Weight-for-age (WAZ), length-for-age (LAZ), and weight-for-length (WLZ) z-scores were calculated using World Health Organization Child Growth Standards. Mean z-scores were compared between in utero antiretroviral exposure groups using Student t test, response profiles analysis, and general linear mixed effects modeling. Results:Growth of 619 HAART-exposed and 440 zidovudine-exposed, HIV-uninfected infants was evaluated. Mean birth weights were 3.01 kg for HAART and 3.15 kg for zidovudine-exposed infants (P < 0.001) with lower mean birth WAZ, length-for-age (LAZ), and weight-for-length (WLZ) among HAART-exposed infants (all P < 0.001). HAART-exposed infants had greater improvement in WAZ and weight-for-length (WLZ) from birth through 2 months (P = 0.03, P < 0.001, respectively). The WAZ did not differ between groups from 3 through 6 months (P = 0.26). Length-for-age (LAZ) remained lower in HAART-exposed infants but the incidence of wasting or stunting did not differ between exposure groups. Conclusions:Lower weights in HAART-exposed uninfected infants at birth were rapidly corrected during the first 6 months of life.

Increased risk of severe infant anemia after exposure to maternal HAART, Botswana.

Background:Maternal highly-active antiretroviral therapy (HAART) reduces mother-to-child HIV transmission but may increase the risk for infant anemia. Methods:The incidence of first severe anemia (grade 3 or 4, Division of AIDS 2004 Toxicity Table) was assessed among HIV-uninfected infants in the Mashi and Mma Bana mother-to-child HIV transmission prevention trials in Botswana. Severe anemia rates were compared between 3 groups: infants exposed to maternal HAART in utero and during breastfeeding (BF) and 1 month of postnatal zidovudine (ZDV) (HAART-BF); infants exposed to maternal ZDV in utero, 6 months of postnatal ZDV, and BF (ZDV-BF); and infants exposed to maternal ZDV in utero, 1 month of postnatal ZDV, and formula-feeding (ZDV-FF). Results:A total of 1719 infants were analyzed-691 HAART-BF, 503 ZDV-BF, and 525 ZDV-FF. Severe anemia was detected in 118 infants (7.4%). By 6 months, 12.5% of HAART-BF infants experienced severe anemia, compared with 5.3% of ZDV-BF (P < 0.001) and 2.5% of ZDV-FF infants (P < 0.001). In adjusted analysis, HAART-BF infants were at greater risk of severe anemia than ZDV-BF or ZDV-FF infants (adjusted odds ratios 2.6 and 5.8, respectively; P < 0.001). Most anemias were asymptomatic and improved with iron/multivitamin supplementation and cessation of ZDV exposure. However, 11 infants (0.6% of all infants) required transfusion for symptomatic anemia. Microcytosis and hypochromia were common among infants with severe anemia. Conclusions:Exposure to maternal HAART starting in utero was associated with severe infant anemia. Confirmation of this finding and possible strategies to mitigate hematologic toxicity warrant further study.

HIV transmission and 24-month survival in a randomized trial of HAART to prevent MTCT during pregnancy and breastfeeding in Botswana.

Objectives:HAART for prevention of mother-to-child HIV transmission (MTCT) may impact long-term survival of women and children. Design:Randomized clinical trial. Methods:HIV-infected pregnant women with CD4+ cell count at least 200 cells/&mgr;l were randomly assigned to abacavir, zidovudine, lamivudine (arm A) or lopinavir–ritonavir, zidovudine–lamivudine (arm B) from week 26 to 34 gestation through planned weaning by 6 months postpartum. Women with baseline CD4+ cell count less than 200 cells/&mgr;l received nevirapine–zidovudine–lamivudine indefinitely (Obs arm), as did randomized women later qualifying for treatment. Results:Among 560 randomized and 170 observational women enrolled, there were 14 deaths (1.9%) – one antenatally (Obs), three from delivery to 6 months postpartum (1 arm A, 2 Obs), and 10 from 6 to 24 months postpartum (5 arm A, 3 arm B, 2 Obs). Time to death or CD4+ cell count below 200 cells/&mgr;l was shorter in arm A vs. B (P = 0.03). Of the 709 live-born children, 97% breastfed for a median of 5.8 months. Of 37 (5.2%) deaths by 24 months, nine were before breastfeeding initiated (3 arm A, 2 arm B, 4 Obs); six while breastfeeding (1 arm A, 2 arm B, 3 Obs); and 22 after weaning (9 arm A, 11 arm B, 2 Obs). Only eight children (1.1%) were HIV-infected at 24 months (6 arm A, 1 arm B, 1 Obs), all before 6 months. Conclusion:Low MTCT was maintained through extended follow-up in all arms. Disease progression appeared slower after discontinuing protease inhibitor-based HAART, but a concerning number of maternal deaths occurred after stopping either regimen. Strategies to improve maternal and child survival in the postintervention period are required.

Nef-Specific CD8+ T Cell Responses Contribute to HIV-1 Immune Control

Recent studies in the SIV-macaque model of HIV infection suggest that Nef-specific CD8+ T-cell responses may mediate highly effective immune control of viraemia. In HIV infection Nef recognition dominates in acute infection, but in large cohort studies of chronically infected subjects, breadth of T cell responses to Nef has not been correlated with significant viraemic control. Improved disease outcomes have instead been associated with targeting Gag and, in some cases, Pol. However analyses of the breadth of Nef-specific T cell responses have been confounded by the extreme immunogenicity and multiple epitope overlap within the central regions of Nef, making discrimination of distinct responses impossible via IFN-gamma ELISPOT assays. Thus an alternative approach to assess Nef as an immune target is needed. Here, we show in a cohort of >700 individuals with chronic C-clade infection that >50% of HLA-B-selected polymorphisms within Nef are associated with a predicted fitness cost to the virus, and that HLA-B alleles that successfully drive selection within Nef are those linked with lower viral loads. Furthermore, the specific CD8+ T cell epitopes that are restricted by protective HLA Class I alleles correspond substantially to effective SIV-specific epitopes in Nef. Distinguishing such individual HIV-specific responses within Nef requires specific peptide-MHC I tetramers. Overall, these data suggest that CD8+ T cell targeting of certain specific Nef epitopes contributes to HIV suppression. These data suggest that a re-evaluation of the potential use of Nef in HIV T-cell vaccine candidates would be justified.

Antiretroviral treatment initiation among HIV-infected pregnant women with low CD4+ cell counts in Gaborone, Botswana.

Background:Botswana has the most comprehensive public program in Africa for providing antiretroviral therapy to treat HIV and prevent mother-to-child transmission (PMTCT). Botswana guidelines prioritize CD4+ cell count testing during pregnancy and initiation of highly active antiretroviral treatment (HAART) for women who qualify for treatment. We analyzed rates of HIV testing, CD4+ cell count testing, and HAART initiation during pregnancy. Methods:From October 2007 through June 2008, we reviewed obstetric and laboratory records of women at Princess Marina Hospital in Gaborone, Botswana. Results:We recorded information from 3056 women. Of 2675 women eligible for the PMTCT program, 2623 (98%) had a documented HIV status, of whom 793 (30%) were HIV infected. Among women who were treatment naive at pregnancy conception, 397 (59%) had recorded CD4+ cell counts, of whom 62 (16%) had a CD4+ cell count <200 cells per cubic millimeter. Among this subset, 23 (37%) initiated HAART during pregnancy, 26 (42%) received zidovudine prophylaxis, and 13 (21%) received no therapy. Conclusions:We observed low rates of CD4+ cell count testing and HAART initiation during pregnancy. Antenatal clinics should prioritize CD4+ cell count testing and referral of women who qualify for HAART to maximize benefits of maternal treatment and PMTCT.