Browsing by Author "Salazar, MG"

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    High Multiplicity Infection by HIV-1 in Men Who Have Sex with Men.
    (PLoS pathogens, 2010) Li, H; Bar, KJ; Wang, S; Decker, JM; Chen, Y; Sun, C; Salazar Gonzalez, JF; Salazar, MG; Learn, GH; Morgan, CJ; Schumacher, JE; Hraber, P; Giorgi, EE; Bhattacharya, T; Korber, BT; Perelson, AS; Eron, JJ; Cohen, MS; Hicks, CB; Haynes, BF; Markowitz, M; Keele, BF; Hahn, BH; Shaw, GM
    Elucidating virus-host interactions responsible for HIV-1 transmission is important for advancing HIV-1 prevention strategies. To this end, single genome amplification (SGA) and sequencing of HIV-1 within the context of a model of random virus evolution has made possible for the first time an unambiguous identification of transmitted/founder viruses and a precise estimation of their numbers. Here, we applied this approach to HIV-1 env analyses in a cohort of acutely infected men who have sex with men (MSM) and found that a high proportion (10 of 28; 36%) had been productively infected by more than one virus. In subjects with multivariant transmission, the minimum number of transmitted viruses ranged from 2 to 10 with viral recombination leading to rapid and extensive genetic shuffling among virus lineages. A combined analysis of these results, together with recently published findings based on identical SGA methods in largely heterosexual (HSX) cohorts, revealed a significantly higher frequency of multivariant transmission in MSM than in HSX [19 of 50 subjects (38%) versus 34 of 175 subjects (19%); Fisher's exact p = 0.008]. To further evaluate the SGA strategy for identifying transmitted/founder viruses, we analyzed 239 overlapping 5' and 3' half genome or env-only sequences from plasma viral RNA (vRNA) and blood mononuclear cell DNA in an MSM subject who had a particularly well-documented virus exposure history 3-6 days before symptom onset and 14-17 days before peak plasma viremia (47,600,000 vRNA molecules/ml). All 239 sequences coalesced to a single transmitted/founder virus genome in a time frame consistent with the clinical history, and a molecular clone of this genome encoded replication competent virus in accord with model predictions. Higher multiplicity of HIV-1 infection in MSM compared with HSX is consistent with the demonstrably higher epidemiological risk of virus acquisition in MSM and could indicate a greater challenge for HIV-1 vaccines than previously recognized.
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    HIV-specific functional antibody responses in breast milk mirror those in plasma and are primarily mediated by IgG antibodies.
    (J Virol, 2011-09) Fouda, GG; Yates, NL; Pollara, J; Shen, X; Overman, GR; Mahlokozera, T; Wilks, AB; Kang, HH; Salazar-Gonzalez, JF; Salazar, MG; Kalilani, L; Meshnick, SR; Hahn, BH; Shaw, GM; Lovingood, RV; Denny, TN; Haynes, B; Letvin, NL; Ferrari, G; Montefiori, DC; Tomaras, GD; Permar, SR; Immunology, the Center for HIVAIDS Vaccine
    Despite months of mucosal virus exposure, the majority of breastfed infants born to HIV-infected mothers do not become infected, raising the possibility that immune factors in milk inhibit mucosal transmission of HIV. HIV Envelope (Env)-specific antibodies are present in the milk of HIV-infected mothers, but little is known about their virus-specific functions. In this study, HIV Env-specific antibody binding, autologous and heterologous virus neutralization, and antibody-dependent cell cytotoxicity (ADCC) responses were measured in the milk and plasma of 41 HIV-infected lactating women. Although IgA is the predominant antibody isotype in milk, HIV Env-specific IgG responses were higher in magnitude than HIV Env-specific IgA responses in milk. The concentrations of anti-HIV gp120 IgG in milk and plasma were directly correlated (r = 0.75; P < 0.0001), yet the response in milk was 2 logarithm units lower than in plasma. Similarly, heterologous virus neutralization (r = 0.39; P = 0.010) and ADCC activity (r = 0.64; P < 0.0001) in milk were directly correlated with that in the systemic compartment but were 2 log units lower in magnitude. Autologous neutralization was rarely detected in milk. Milk heterologous virus neutralization titers correlated with HIV gp120 Env-binding IgG responses but not with IgA responses (r = 0.71 and P < 0.0001, and r = 0.17 and P = 0.30). Moreover, IgGs purified from milk and plasma had equal neutralizing potencies against a tier 1 virus (r = 0.65; P < 0.0001), whereas only 1 out of 35 tested non-IgG milk fractions had detectable neutralization. These results suggest that plasma-derived IgG antibodies mediate the majority of the low-level HIV neutralization and ADCC activity in breast milk.
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    Origin and evolution of HIV-1 in breast milk determined by single-genome amplification and sequencing.
    (J Virol, 2011-03) Salazar-Gonzalez, JF; Salazar, MG; Learn, GH; Fouda, GG; Kang, HH; Mahlokozera, T; Wilks, AB; Lovingood, RV; Stacey, A; Kalilani, L; Meshnick, SR; Borrow, P; Montefiori, DC; Denny, TN; Letvin, NL; Shaw, GM; Hahn, BH; Permar, SR; A0167854, Center for HIV AIDS Vaccine Immunology
    HIV transmission via breastfeeding accounts for a considerable proportion of infant HIV acquisition. However, the origin and evolution of the virus population in breast milk, the likely reservoir of transmitted virus variants, are not well characterized. In this study, HIV envelope (env) genes were sequenced from virus variants amplified by single-genome amplification from plasmas and milk of 12 chronically HIV-infected, lactating Malawian women. Maximum likelihood trees and statistical tests of compartmentalization revealed interspersion of plasma and milk HIV env sequences in the majority of subjects, indicating limited or no compartmentalization of milk virus variants. However, phylogenetic tree analysis further revealed monotypic virus variants that were significantly more frequent in milk (median proportion of identical viruses, 29.5%; range, 0 to 61%) than in plasma (median proportion of identical viruses, 0%; range, 0 to 26%) (P = 0.002), suggesting local virus replication in the breast milk compartment. Moreover, clonally amplified virus env genes in milk produced functional virus Envs that were all CCR5 tropic. Milk and plasma virus Envs had similar predicted phenotypes and neutralization sensitivities to broadly neutralizing antibodies in both transmitting and nontransmitting mothers. Finally, phylogenetic comparison of longitudinal milk and plasma virus env sequences revealed synchronous virus evolution and new clonal amplification of evolved virus env genes in milk. The limited compartmentalization and the clonal amplification of evolving, functional viruses in milk indicate continual seeding of the mammary gland by blood virus variants, followed by transient local replication of these variants in the breast milk compartment.