Characterization of Immune Escape Viruses from a Macaque Immunized with Live-Virus Vaccine and Challenged with Pathogenic SHIV KU-1

We characterized two immune escape viruses (SHIV_KU-1/105w52 and SHIV_KU-1/105w98) from a macaque immunized with ΔvpuΔnef SHIV-4 and challenged with pathogenic SHIV_KU-1. This macaque developed neutralizing antibodies as well as virus-specific CTLs against the challenge virus. However, the two new viruses could not be neutralized by anti-SHIV_KU-1-specific neutralizing antibodies and were poorly recognized by challenge virus-specific CTLs. Sequence analysis of the gene encoding gp120 revealed several mutations in the protein that might have contributed to the development of the immune-escape viruses.