The Lymphocytosis-Promoting Agent Pertussis Toxin Affects Virus Burden and Lymphocyte Distribution in the SIV-Infected Rhesus Macaque

Pertussis toxin from the gram-negative bacterium Bordetella pertussis is an ADP-ribosylase that modifies G_i proteins in mammalian lymphocytes and inhibits their capacity to traffic from blood into lymphoid tissues. We used this compound to induce lymphocytosis in rhesus macaques and to study its effects on SIV infection. Pertussis toxin injected at 25 μg/kg induced a transient lymphocytosis that peaked 3-8 days after administration and caused a rapid, transient decrease in the frequency of infectious cells in blood as judged by in vitro virus isolation assays. Lymphocyte subsets were altered during the lymphocytosis interval and sustained changes in CD8⁺ T cell levels were noted as long as 53 days after pertussis toxin injection. In situ hybridization studies showed that pertussis toxin altered the distribution of viral RNA in lymph nodes during the interval of lymphocytosis, and caused long-term changes with decreased virus replication in some tissue specimens.