PEPTIDES FROM MAJOR VIRUS-NEUTRALIZING AN D CD4-BINDING DOMAIN - SIMILAR IMMUNOREACTIVE PROPERTIES AND STRUCTURAL MOTIVE

The human immunodeficiency virus (HIV) proteins gp120 and gp41 are the principal immune target in HIV infection. One of the most important t rends in the study of AIDS is linked to the mapping of sites involving in the binding to the cell receptor CD4 and in the induction of virus -neutralizing antibodies (VNA). Recent studies have revealed that gp12 0 as the major domain contains inducing type-specific BNA (PND) and a binding region with CD4 (CD4-BR). PND is located in the hypervariable loop of gp120 (residues 301-336 for a BRU strain), and CD4-BR is in th e conservation area (residues 410-450). By using the synthetic fragmen ts from these areas (BRU and MN strains) and HIV-infected persons ' se ra, the authors established that the immune response to PND and CD4-BR is somewhat interrelated: there is a synchronized response of HIV ant ibodies to petides from the two regions in ELISA (r=0.82). For analysi s of this phenomenon, experiments with cross-linked immunoreactivity o f rabbit antisera to peptides from PND and CD4-BR with homological and heterological peptides were performed by applying three control pepti des from HIV and hepatitis B virus. It has been found that there is a cross reactivity between rabbit anti-PND (MN, BRU) and anti-CD4-BR abs . Peptide homological analysis revealed common structural elements for PND and CD4-BR despite significant differences in their proposed func tions. There is a large amount of positively charged aa within both PN D and CD4-BR which may be involved in gp120-CD4 interaction. Acetylati on of Lys residues resulted in complete loss of peptide reactivity.