Increased HIV-1 vaccine efficacy against viruses with genetic signatures in Env V2.

The RV144 trial demonstrated 31% vaccine efficacy at preventing human immunodeficiency virus (HIV)-1 infection. Antibodies against the HIV-1 envelope variable loops 1 and 2 (Env V1 and V2) correlated inversely with infection risk. We proposed that vaccine-induced immune responses against V1/V2 would have a selective effect against, or sieve, HIV-1 breakthrough viruses. A total of 936 HIV-1 genome sequences from 44 vaccine and 66 placebo recipients were examined. We show that vaccine-induced immune responses were associated with two signatures in V2 at amino acid positions 169 and 181. Vaccine efficacy against viruses matching the vaccine at position 169 was 48% (confidence interval 18% to 66%; P = 0.0036), whereas vaccine efficacy against viruses mismatching the vaccine at position 181 was 78% (confidence interval 35% to 93%; P = 0.0028). Residue 169 is in a cationic glycosylated region recognized by broadly neutralizing and RV144-derived antibodies. The predicted distance between the two signature sites (21 ± 7 Å) and their match/mismatch dichotomy indicate that multiple factors may be involved in the protection observed in RV144. Genetic signatures of RV144 vaccination in V2 complement the finding of an association between high V1/V2-binding antibodies and reduced risk of HIV-1 acquisition, and provide evidence that vaccine-induced V2 responses plausibly had a role in the partial protection conferred by the RV144 regimen.

Analysis of HLA A*02 association with vaccine efficacy in the RV144 HIV-1 vaccine trial.

UNLABELLED: The RV144 HIV-1 vaccine trial demonstrated partial efficacy of 31% against HIV-1 infection. Studies into possible correlates of protection found that antibodies specific to the V1 and V2 (V1/V2) region of envelope correlated inversely with infection risk and that viruses isolated from trial participants contained genetic signatures of vaccine-induced pressure in the V1/V2 region. We explored the hypothesis that the genetic signatures in V1 and V2 could be partly attributed to selection by vaccine-primed T cells. We performed a T-cell-based sieve analysis of breakthrough viruses in the RV144 trial and found evidence of predicted HLA binding escape that was greater in vaccine versus placebo recipients. The predicted escape depended on class I HLA A*02- and A*11-restricted epitopes in the MN strain rgp120 vaccine immunogen. Though we hypothesized that this was indicative of postacquisition selection pressure, we also found that vaccine efficacy (VE) was greater in A*02-positive (A*02(+)) participants than in A*02(-) participants (VE = 54% versus 3%, P = 0.05). Vaccine efficacy against viruses with a lysine residue at site 169, important to antibody binding and implicated in vaccine-induced immune pressure, was also greater in A*02(+) participants (VE = 74% versus 15%, P = 0.02). Additionally, a reanalysis of vaccine-induced immune responses that focused on those that were shown to correlate with infection risk suggested that the humoral responses may have differed in A*02(+) participants. These exploratory and hypothesis-generating analyses indicate there may be an association between a class I HLA allele and vaccine efficacy, highlighting the importance of considering HLA alleles and host immune genetics in HIV vaccine trials. IMPORTANCE: The RV144 trial was the first to show efficacy against HIV-1 infection. Subsequently, much effort has been directed toward understanding the mechanisms of protection. Here, we conducted a T-cell-based sieve analysis, which compared the genetic sequences of viruses isolated from infected vaccine and placebo recipients. Though we hypothesized that the observed sieve effect indicated postacquisition T-cell selection, we also found that vaccine efficacy was greater for participants who expressed HLA A*02, an allele implicated in the sieve analysis. Though HLA alleles have been associated with disease progression and viral load in HIV-1 infection, these data are the first to suggest the association of a class I HLA allele and vaccine efficacy. While these statistical analyses do not provide mechanistic evidence of protection in RV144, they generate testable hypotheses for the HIV vaccine community and they highlight the importance of assessing the impact of host immune genetics in vaccine-induced immunity and protection. (This study has been registered at ClinicalTrials.gov under registration no. NCT00223080.).

Use of dried blood spots for HIV-1 genotyping in Southeast Asia: Thailand experience.

The multi-region hybridization assay (MHAbce) for genotyping HIV-1 subtypes B, C and circulating recombinant form (CRF01_AE) was evaluated on paired plasma and dried blood spots (DBS) collected from 68 HIV-1 infected individuals in Thailand. CRF01_AE was the predominant subtype identified using plasma samples (51/62) and DBS (24/27). There was no discordance in subtype designations between plasma and DBS.

Pattern and Frequency of Seroreactivity to Routinely Used Serologic Tests in Early-Treated Infants With HIV.

BACKGROUND: Previous studies have shown low frequencies of seroreactivity to HIV diagnostic assays for infected infants treated with antiretroviral therapy (ART) early in infection. METHODS: Fifty-eight HIV-infected infants treated with ART at a median age of 1.9 months (range: 0.2-5.4) for up to 4 years of life were assessed for seroreactivity to 4 routinely used HIV clinical immunoassays (IA): Second-generation (2ndG) IA and 2 rapid diagnostic tests (RDT), based on third-generation principles, measuring antibody only and a fourth-generation (4thG) antigen/antibody IA. HIV Western blot assay was also performed to assess HIV-specific antibodies. RESULTS: The 2ndG IA demonstrated the highest frequency of seroreactivity in children (69%) followed by the 4thG IA (40%) and the RDT (26%) after one year of ART. Infants initiating ART during ages 3-6 months (N = 15) showed a greater frequency (range: 53%-93%) and breadth (median and range: 3 [1-4]) of reactivity across the assays compared with those treated within 3 months (N = 43):16%-61% and breadth (1 [0-4]). The 4thG IA showed significantly reduced reactivity relative to the 2ndG IA at one (P = 0.016) and 3 (P = 0.004) years of ART. Western blot profiles following 3 years of ART showed the highest frequency of reactivity to HIV Gag p24 (76%) and lowest reactivity to Env gp120 and gp41, with only 24% of children confirmed positive by the assay. CONCLUSIONS: These results suggest that the use of 4thG IA and RDT test combination algorithms with limited HIV antigen breadth may not be adequate for diagnosis of HIV-infected children following early treatment.

A novel EGFP-CEM-NKr flow cytometric method for measuring antibody dependent cell mediated-cytotoxicity (ADCC) activity in HIV-1 infected individuals.

Enhanced green fluorescent protein (EGFP) was stably expressed in CEM-NKr cell, a natural killer (NK) resistant human T-lymphoblastoid cell line, as EGFP-CEM-NKr cells. The cells pulsed with HIV-1 gp120 were then used as target cells for the measurement of antibody dependent cell mediated-cytotoxicity (ADCC) by flow cytometry. Compromised EGFP-CEM-NKr target cells stained with propidium iodide (PI) showed dual (green-red) fluorescent. Kinetic studies demonstrated that the sum of ADCC activity measured at 1-h and again at 2-h incubations by this flow cytometric method was comparable to the activity at 6 h by the standard chromium (51Cr) release assay (CRA). ADCC activity of HIV-1 seropositive sera measured by this new technique correlated strongly with that of CRA (Pearson's correlation coefficient of 0.832; p-value < 0.001 and intraclass correlation coefficient of 0.903; p-value < 0.001). The EGFP-CEM-NKr stable cell line provides a novel method to measure ADCC activity to HIV-1 gp120 by flow cytometry without pre-staining or pre-labeling target cells.

Two unique recombinant forms identified in incident HIV type 1 infections in Thai blood donors.

HIV-1 genetic diversity of recently seroconverting (<12 months) Thai repeated blood donors attending the National Blood Centre, Thai Red Cross Society (NBC, TRCS) from September 2007 until March 2008 was assessed. Ten HIV-1 recent seroconvertors (10/239,134 donations) were identified during the study period. The estimated median time to seroconversion was 67.3 days (range: 45.5-102.0 days), and viral load ranged from 307 to 341,805 copies HIV-1 RNA/ml. MHAbce, a real-time-based PCR genotyping assay, identified six CRF01_AE, two CRF01_AE/B recombinants, one subtype B, and one CRF01_AE/B dual infection. Nine samples were further characterized by full genome sequencing, identifying CRF01_AE (N=6), unique CRF01_AE/B recombinants (N=2), and subtype B (N=1). One recombinant contained 13 breakpoints located in gag, pol, vif, vpr, env, and nef while the other recombinant contained 10 breakpoints located in pol, vif, env, and nef. This study found two unique CRF01B recombinants circulating in 10 recent HIV-1-positive subjects from a blood donor population in Thailand.

HIV type 1 molecular epidemiology among high-risk clients attending the Thai Red Cross Anonymous Clinic in Bangkok, Thailand.

Several studies have reported an increasing number of non-CRF01_AE infections in high-risk groups in Thailand suggesting a more complex HIV-1 epidemic. This study assessed the complexity of the HIV epidemic among high-risk clients tested for HIV-1 at the Thai Red Cross Anonymous Clinic (TRCAC) between July 1, 2006 and February 28, 2007. HIV-1 genotypes were determined from plasma of infected subjects (n = 401) by the multiregion hybridization assay (MHAbce, v.2). Univariate and multivariate logistic regression analyses were used to determine risk factors associated with HIV prevalence and non-CRF01_AE infection. The estimated overall HIV prevalence was 14.1%: 25.3% among men who have sex with men (MSM), 18.4% among heterosexual women, and 9.6% among heterosexual men. Among the risk factors found to be associated with HIV prevalence were age (25-29 years), risk behavior (MSM), marital status (not single), education (less than high school), and inconsistent condom use. Overall, non-CRF01_AE strains accounted for 18.9% of the infections: 25.3% among MSM and 14.8% and 20.4% among heterosexual women and men, respectively. Our results indicate a concentrated and genetically complex HIV epidemic among Thai MSM. These findings advocate for targeted intervention and prevention measures among high-risk populations in Thailand.