Browsing by Author "James Swetnam"

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    Cryptic determinant of a4b7 binding in the v2 loop of hiv-1 gp120
    (2014-09-29) Boonrat Tassaneetrithep; Doreen Tivon; James Swetnam; Nicos Karasavvas; Nelson L. Michael; Jerome H. Kim; Mary Marovich; Timothy Cardozo; Mahidol University; Walter Reed Army Institute of Research; NYU School of Medicine; Armed Forces Research Institute of Medical Sciences, Thailand; Google LLC
    The peptide segment of the second variable loop of HIV-1 spanning positions 166-181 harbors two functionally important sites. The first, spanning positions 179-181, engages the human α4b7 integrin receptor which is involved in T-cell guthoming and may play a role in human immunodeficiency virus (HIV)-host cell interactions. The second, at positions 166-178, is a major target of anti-V2 antibodies elicited by the ALVAC/AIDSVAX vaccine used in the RV144 clinical trial. Notably, these two sites are directly adjacent, but do not overlap. Here, we report the identity of a second determinant of α4b7 binding located at positions 170-172 of the V2 loop. This segment - tripeptide QRV170-172- is located within the second site, yet functionally affects the first site. The absence of this segment abrogates α4b7 binding in peptides bearing the same sequence from position 173-185 as the V2 loops of the RV144 vaccines. However, peptides exhibiting V2 loop sequences from heterologous HIV-1 strains that include this QRV170-172 motif bind the α4b7 receptor on cells. Therefore, the peptide segment at positions 166-178 of the V2 loop of HIV-1 viruses appears to harbor a cryptic determinant of α4b7 binding. Prior studies show that the anti-V2 antibody response elicited by the RV144 vaccine, along with immune pressure inferred from a sieve analysis, is directed to this same region of the V2 loop. Accordingly, the anti-V2 antibodies that apparently reduced the risk of infection in the RV144 trial may have functioned by blocking α4b7-mediated HIV-host cell interactions via this cryptic determinant.