Search for Epitope-Specific Antibody Responses to the Human Immunodeficiency Virus (HIV-1) Envelope Glycoproteins Signifying Resistance to Disease Development

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Abstract
It is essential for the development of strategies for prevention and therapy of human immunodeficiency virus (HIV-1) infections to define host factors playing a dominant role in determining the clinical outcome of infection. Antibodies directed against restricted regions of the HIV-1 glycoproteins gp120 and gp41 are likely to represent important factors involved in host defense against HIV-1. Definition of qualitative and quantitative differences in the spectrum of anti-gp120 and anti-gp41 antibodies between two vastly different groups of HIV-1-infected individuals, long-term asymptomatic carriers, and individuals with acquired immunodeficiency syndrome (AIDS) who died, might reveal the epitope specificity of antibodies contributing to prevention of clinical disease. To accomplish this goal, sera from both groups were assayed for antibodies recognizing synthetic peptides from gp120/gp41 which were shown in earlier experiments to mimic epitopes on the two HIV-1 glycoproteins. None of the sera recognized all of the distinct 27 peptides from gp120 and gp41. The spectrum of antibodies was distinct for each of the sera from both groups of HIV-1-infected individuals. Nevertheless, antibody responses distinguishing the two groups from each other were discerned. In particular, it was possible to predict the unfavorable outcome of disease by comparative measurements of levels of antibodies to a peptide (303-338), corresponding to the entire V3 hypervariable loop of gp120 and/or by providing evidence for declining levels of these antibodies during the course of infection. Antibodies recognizing additional peptides [(219-245), (280-306), (425-452), (658-682), (729-758), (808-845), and (845-862)] were significantly less prevalent in AIDS patients than in asymptomatic carriers. It appears possible that maintenance of high levels of the respective antibodies would contribute to preventing AIDS in HIV-1-infected individuals. Active immunization with antigens containing epitopes defined by the respective peptides and/or administration of the corresponding antibodies may be considered as a modality for therapy of HIV-1 infections.