HTLV-III neutralizing antibody development in transfusion-dependent seropositive patients with beta-thalassemia

Sera collected in New York in 1984 from 77 patients with homozygous beta-thalassemia were assayed for antibodies to HTLV-III by ELISA and Western blot techniques. Eight (12%) of the 66 hypertransfused thalassemics were seropositive. Retrospective sera of these eight individuals were examined by radioimmune precipitation (RIP), and assays for neutralization of virus infectivity were performed. With seroconversion, antibodies to viral envelope proteins appeared first and were correlated with development of neutralizing antibody. Affinity purified gp120, the major envelope glycoprotein of HTLV-III, blocked viral infectivity and absorbed neutralizing antibody activity from a positive serum. Neutralizing antibody titers mirrored antibody titers to gp120 by RIP. Antibody to gp120 sometimes occurred in the absence of neutralizing antibody, although the reverse was not true. One thalassemia patient who exhibited antibody to gp120 for 3 yr post-seroconversion failed to develop neutralizing antibody, acquired the acquired immunodeficiency syndrome with central nervous system involvement and lymphoma, and subsequently died. In contrast, all other seropositive thalassemics possessed neutralizing antibodies, and were asymptomatic or exhibited only lymphadenopathy. These results indicate that gp120 elicits neutralizing antibodies in the course of natural infection with HTLV-III. The relationship seen here between neutralizing antibody and better clinical outcome needs to be verified by additional studies.