RT Journal Article SR Electronic T1 An intestinally secreted host factor promotes microsporidia invasion of C. elegans JF bioRxiv FD Cold Spring Harbor Laboratory SP 2021.07.12.452088 DO 10.1101/2021.07.12.452088 A1 Hala Tamim El Jarkass A1 Calvin Mok A1 Michael R. Schertzberg A1 Andrew G. Fraser A1 Emily R. Troemel A1 Aaron W. Reinke YR 2021 UL http://biorxiv.org/content/early/2021/12/13/2021.07.12.452088.abstract AB Microsporidia are ubiquitous obligate intracellular pathogens of animals. These parasites often infect hosts through an oral route, but little is known about the function of host intestinal proteins that facilitate microsporidia invasion. To identify such factors necessary for infection by Nematocida parisii, a natural microsporidian pathogen of Caenorhabditis elegans, we performed a forward genetic screen to identify mutant animals that have a Fitness Advantage with Nematocida (Fawn). We isolated four fawn mutants that are resistant to Nematocida infection and contain mutations in T14E8.4, which we renamed aaim-1 (Antibacterial and Aids invasion by Microsporidia). Expression of AAIM-1 in the intestine of aaim-1 animals restores N. parisii infectivity and this rescue of infectivity is dependent upon AAIM-1 secretion. N. parisii spores in aaim-1 animals are improperly oriented in the intestinal lumen, leading to reduced levels of parasite invasion. Conversely, aaim-1 mutants display both increased colonization and susceptibility to the bacterial pathogen Pseudomonas aeruginosa and overexpression of AAIM-1 reduces P. aeruginosa colonization. Competitive fitness assays show that aaim-1 mutants are favoured in the presence of N. parisii but disadvantaged on P. aeruginosa compared to wild type animals. Together, this work demonstrates how microsporidia exploits a secreted protein to promote host invasion. Our results also suggest evolutionary trade-offs may exist to optimizing host defense against multiple classes of pathogens.Competing Interest StatementThe authors have declared no competing interest.