Human antibodies to major histocompatibility complex alloantigens mediate lysis and neutralization of HIV-1 primary isolate virions in the presence of complement

Cellular proteins, including major histocompatibility complex (MHC) class I and class II antigens, are incorporated into the membrane of HIV-1 when vi rions bud from infected cells. Experiments were performed to determine whet her human sera that contained MHC class I and/or class II antibodies would lyse or neutralize a primary isolate of HIV. These results demonstrate that in the presence of complement, sera from some alloimmunized persons mediat ed significant anti-viral activity against an HIV primary isolate. Both lys is and neutralization of virus were observed. The antiviral effects were co mplement dependent because heat inactivation eliminated most anti-viral eff ects. Antiviral activity mediated by sera containing MHC alloantibodies in the presence of complement was greater than or equal to activity due to ser a from HIV-infected persons as reported in this and a previous study. High levels of antibodies to both MHC class I and class II were present in sera that mediated the highest levels of anti-viral activity. Absorption of seru m with platelets (which express class I but not class II antigens) substant ially reduced their lyric activity. These studies suggest that MHC antibodi es mediate potent anti-viral effects on primary isolates of HIV and support the possibility that deliberately alloimmunizing humans might protect agai nst HIV infection.