IN-VITRO EFFECTS OF ANTI-HIV IMMUNOTOXINS DIRECTED AGAINST MULTIPLE EPITOPES ON HIV TYPE-1 ENVELOPE GLYCOPROTEIN-160

We have used a panel of anti-gp160 MAbs to construct anti-HIV immunoto xins by coupling antibodies to ricin A chain (RAG), The ability of the immunotoxins to kill HIV-1-infected cells and halt the spread of infe ction was tested in tissue culture on persistently and acutely infecte d cell lines and primary lymphocyte cultures stimulated with phytohema gglutinin (PHA blasts), Laboratory strains and clinical isolates of HI V both were tested, The constitution and antigen-binding capacity of t he immunotoxins mere confirmed by ELISA and indirect immunofluorescenc e. Immunotoxins that bind epitopes exposed on the cell surface effecti vely killed persistently infected cells, although killing was not dire ctly proportional to binding of immunotoxin to cell. The activity of a nti-gp41, but not anti-gp120, immunotoxins was markedly enhanced in th e presence of soluble CD4 or peptides corresponding to the CDR3 region of CD4, CD4-mediated enhancement of anti-gp41 immunotoxin activity wa s observed for laboratory strains neutralized by sCD4 and for clinical isolates that were resistant to neutralization by sCD4, Immunotoxin a ction was potentiated by brefeldin A, bafilomycin A1, cortisone, and a n amphipathic fusion peptide, but not by cytochalasin D, nocodazol, mo nodansyl cadaverine, or trans-retinoic acid. Anti-HIV immunotoxins are useful tools with which to study the functional expression of gp120/g p41 antigens on the surface of HIV-infected cells, as well as potentia l AIDS therapeutics, Because these studies relate to the accessibility of viral antigens to antibody-mediated attack, these studies also hav e relevance for vaccine development.