For these studies HIV-1 gp41 monoclonal antibody (2F5), cat# 1475 was used. The following reagent was obtained through the NIH AIDS Research and Reference Reagent Program, Division of AIDS, NIAID, NIH: HIV-1 gp41 Monoclonal Antibody (2F5) was generated by Dr. Hermann Katinger. The human monoclonal antibody to HIV-1 gp41 is specific for ELDKWA epitope [23] [24] [25] . Goat anti-human horse radish peroxidase (HRP) antibody was purchased from Southern Biotech. (Birmingham, AL).