MECHANISMS OF RESISTANCE OF HIV-1 PRIMARY ISOLATES TO COMPLEMENT-MEDIATED LYSIS

Previous studies suggested that HIV-1 primary isolates (PI) were resis tant to complement-mediated lysis (CML), while virus produced in certa in T cell lines and virus taken directly from the plasma of HIV+ perso ns were both susceptible to CML. The purpose of this study was to inve stigate the mechanism(s) of PI resistance. PI were resistant to CML us ing pooled seropositive serum as an antibody source. Additionally, PI obtained from two patients at several times over 2 years were resistan t to CML using autologous antibody. PI were also resistant to CML indu ced by monoclonal antibodies which neutralize a broad range of PI. Res istance to CML was associated with low binding of antibody to PI but w as not due to low gp120 levels. Cell-line-derived virus and PI were eq ually sensitive to CML induced by antibody to host-cell proteins, sugg esting that PBMC do not contribute properties to virions which make th em more physically resistant to CML in general but that PI resistance is restricted to CML induced by antiviral antibody. These studies show that PI are resistant to CML mediated by various antiviral antibodies and indicate that low binding of antibody to virus is an important fa ctor contributing to resistance. (C) 1998 Academic Press.