Host transcriptional responses to high- and low-virulent avian malaria parasites

AbstractThe transcriptional response of hosts to genetically similar pathogens can vary substantially, with important implications for disease severity and host fitness. A low pathogen load can theoretically elicit both high and low host responses, as the outcome depends on both the effectiveness of the host at suppressing the pathogen and the ability of the pathogen to evade the immune system. Here, we investigate the transcriptional response of Eurasian siskins (Spinus spinus) to two closely related lineages of the malaria parasite Plasmodium relictum. Birds were infected with either the high-virulent lineage P. relictum SGS1, the low-virulent sister lineage P. relictum GRW4, or sham-injected (controls). Blood samples for RNA sequencing were collected at four time points during the course of infection, totaling 76 transcriptomes from 19 birds. Hosts infected with SGS1 experienced up to 87% parasitemia and major transcriptome shifts throughout the infection, and multiple genes showed strong correlation w...