Expression and characterization of HIV type 1 envelope protein associated with a broadly reactive neutralizing antibody response

We have studied envelope protein from a donor with nonprogressive HIV-1 inf ection whose serum contains broadly cross-reactive, primary virus NA. DNA w as extracted from lymphocytes, which had been collected approximately 6 and 12 months prior to the time of collection of the cross-reactive serum, and env genes were synthesized, cloned, expressed on pseudoviruses, and phenot yped in NA assays. Two clones from each time point had identical V3 region nucleotide sequences, utilized CCR5 but not CXCR4 for cell entry, and had s imilar reactivities with reference sera. Analysis of the full nucleotide se quence of one clone (R2) demonstrated it to be subtype B and have normal pr edicted glycosylation, R2 pseudovirus was compared with others expressing e nv genes of various clades for neutralization by sera from U.S. donors (pre sumed or known subtype B infections), and from individuals infected with su btypes A, C, D, E, and F viruses. Neutralization by the U.S. sera of R2 and other clade B pseudoviruses was low to moderate, although R2 was uniquely neutralized by all. R2 was neutralized by 3/3, 3/3, 2/5, 5/8, and 3/4 clade A, C, D, E, and F sera, respectively. R2 and a clade E pseudovirus were ne utralized by largely complementary groups of sera, potentially defining two antigenic subgroups of HIV-1, The results suggest that the epitope(s) that induced the cross-clade reactive NA in donor 2 may be expressed on the R2 envelope.