Cryptic Determinant of [albha]4 beta 7 Binding in the V2 Loop of HIV-1

Background: The peptide segment spanning positions 166-181 of the V2 loop of HIV-1 has been found to harbor two functionally important sites. The first, spanning positions 179-181, binds the human alpha 4 beta 7 integrin receptor that plays a role in dissemination of infecting HIV-1 virions to gut-associated lymphoid tissue (GALT). The second, at positions 166-178, is the target of anti-V2 antibodies elicited by the vaccines used in the RV144 clinical trial. Here, we present evidence that this second site affects the functionality of the first site.