Meeting Abstract

48.5  Thursday, Jan. 6  Why does a strong immune response does not protect against parasite infection? KRISTAN, D.M.; California State University San Marcos dkristan@csusm.edu

We have recently completed several studies on the effects of long-term calorie restriction on susceptibility to an intestinal nematode parasite (Heligmosomoides bakeri) infection in laboratory mice (Mus musculus). The design of these studies reduces calorie intake by 40% for at least 6 months, but always keeps similar protein intake levels between calorie restricted (CR) and ad libitum fed (AL) mice, because protein availability is known to affect immune function. We found that long-term calorie restriction either enhanced the immune system (e.g., mice produced more CD4+ splenic T cells) or maintained immune responses (e.g., circulating total and parasite specific IgG1) during both primary and repeated infections. Despite their strong immune response, CR mice harbored more worms and the worms from CR mice were in better condition (i.e., worms grew longer and females produced more eggs). Current experiments are underway to test possible roles of chronic levels of reactive oxygen species and antioxidants to help explain this disconnect between some traditional measures of immune response and susceptibility to intact parasites. In addition, we are also testing if other parasite taxa (cestode, trematode, protozoan) show similar results as H. bakeri. Overall, host calorie intake may have important effects on susceptibility to pathogens and also on life-history of their parasites.