Cytomegalovirus in Wild Peromyscus: The Effects of Intestinal Parasite Interaction and Immunosenescence

Abstract

Cytomegalovirus (CMV) is one of the most common viral infections impacting humans across the world. As of now, there is no proven vaccine to prevent CMV and those infected are so for life. A murine model has been used for years to study how factors such as coinfection and immunosenescence can affect host response to CMV infection. One focus of this study was to investigate the effects that age can have on CMV. A healthy immune system is able to suppress CMV infection into a latent stage that does not lead to severe disease. However, a weakened immune system can result in CMV resurfacing which can progress to disease and possibly death. I hypothesize that a weakened immune system due to age will cause a greater prevalence of CMV infection in older mice. In this study, the blood sera from a wild Peromyscus population were tested for pCMV antibodies and revealed that CMV prevalence increases with age due to possible immunosenescence and thymic atrophy. Humans, as well as all mammals, harbor multiple parasitic infections at any given time. Concomitant infection is essential to consider when researching a host’s immune response to CMV in hopes of developing new treatments and possible vaccines. Wild Peromyscus mice treated with Ivermectin to experimentally remove intestinal nematodes were examined in this study. Previous studies on Peromyscus in the same study location have noted a decrease 4 in nematode prevalence as well as an increase in coccidian parasites in the gastrointestinal tract of hosts treated with Ivermectin. This study investigated how intestinal parasitic changes could alter a host’s ability to properly suppress CMV infection. I hypothesize that Ivermectin treated mice will experience decrease in nematode parasites, thus lowering helminth Th2 response and provoking a stronger viral Th1 response than is operating in the control mice (Vandegrift, 2008). The decrease in helminth Th2 response and increase in viral Th1 response will benefit the host’s ability to suppress CMV. Results indicate otherwise, showing that untreated Peromyscus were more successful in suppressing CMV disease than Ivermectin treated mice. These outcomes suggest that deworming may be detrimental to the host in some cases, contrary to popular belief. The findings of this study suggest that age and intestinal parasite populations need to be evaluated when treating an individual for CMV.