Gamma Irradiation or CD4⁺-T-Cell Depletion Causes Reactivation of Latent<i>Salmonella enterica</i>Serovar Typhimurium Infection in C3H/HeN Mice

Abstract

ABSTRACT Upon infection with Salmonella , a host develops an immune response to limit bacterial growth and kill and eliminate the pathogen. Salmonella has evolved mechanisms to remain dormant within the body, only to reappear (reactivate) at a later time when the immune system is abated. We have developed an in vivo model for studying reactivation of Salmonella enterica serovar Typhim urium infection in mice. Upon subcutaneous infection, C3H/HeN (Ity r ) mice showed an increase in bacterial numbers in livers and spleens, which reached a peak on day 19. After full recovery from the infection, these mice were irradiated or depleted of CD4 + T cells. The mice displayed a secondary infection peak in livers and spleens with a course similar to that of the primary infection. We concluded that CD4 + T cells are involved in active suppression of S. enterica serovar Typhimurium during latency. The role of CD4 + T cells during primary infection with S. enterica serovar Typhimurium is well established. This is the first study to describe a role of CD4 + T cells during the latent phase of S. enterica serovar Typhimurium infection.