Schistosoma mansoni Infection Impairs Antimalaria Treatment and Immune Responses of Rhesus Macaques Infected with Mosquito-Borne Plasmodium coatneyi

Abstract

ABSTRACTMalaria and schistosomiasis are the world's two most important parasitic infections in terms of distribution, morbidity, and mortality. In areas wherePlasmodiumandSchistosomaspecies are both endemic, coinfections are commonplace. Mouse models demonstrate that schistosomiasis worsens a malaria infection; however, just as mice and humans differ greatly, the murine-infectingPlasmodiumspecies differ as much from those that infect humans. Research into human coinfections (Schistosoma haematobium-Plasmodium falciparumversusSchistosoma mansoni-P. falciparum) has produced conflicting results. The rhesus macaque model provides a helpful tool for understanding the role ofS. mansonion malaria parasitemia and antimalarial immune responses usingPlasmodium coatneyi, a malaria species that closely resemblesP. falciparuminfection in humans. Eight rhesus macaques were exposed toS. mansonicercariae. Eight weeks later, these animals plus 8 additional macaques were exposed to malaria either through bites of infected mosquitos or intravenous inoculation. When malaria infection was initiated from mosquito bites, coinfected animals displayed increased malaria parasitemia, decreased hematocrit levels, and suppressed malaria-specific antibody responses compared to those of malaria infection alone. However, macaques infected by intravenous inoculation with erythrocytic-stage parasites did not display these same differences in parasitemia, hematocrit, or antibody responses between the two groups. Use of the macaque model provides information that begins to unravel differences in pathological and immunological outcomes observed between humans withP. falciparumthat are coinfected withS. mansoniorS. haematobium. Our results suggest that migration of malaria parasites through livers harboring schistosome eggs may alter host immune responses and infection outcomes.