Viruses
HIV-1Bal, HIV-1Lai, HIV-193TH64, HIV-192TH51, HIV-192TH53, HIV-198CH01, and HIV-198IN22 were obtained from The Centralized Facility for AIDS Reagents, National Institute for Biological Standard and Control (NIBSC), United Kingdom. HIV-1KR25 was isolated in our laboratory as described before [33].