ABSTRACTThe obligate intracellular parasiteToxoplasma gondiicritically relies on host cell invasion during infection. Proteins secreted from the apical micronemes are central components for host cell recognition, invasion, egress, and virulence. Although previous work established that the sporozoite protein with an altered thrombospondin repeat (SPATR) is a micronemal protein conserved in other apicomplexan parasites, includingPlasmodium,Neospora, andEimeria, no genetic evidence of its contribution to invasion has been reported. SPATR contains a predicted epidermal growth factor domain and two thrombospondin type 1 repeats, implying a role in host cell recognition. In this study, we assess the contribution ofT. gondiiSPATR (TgSPATR) toT. gondiiinvasion by genetically ablating it and restoring its expression by genetic complementation. Δspatrparasites were ∼50% reduced in invasion compared to parental strains, a defect that was reversed in the complemented strain. In mouse virulence assays, Δspatrparasites were significantly attenuated, with ∼20% of mice surviving infection. Given the conservation of this protein among the Apicomplexa, we assessed whether thePlasmodium falciparumSPATR ortholog (PfSPATR) could complement the absence of the TgSPATR. Although PfSPATR showed correct micronemal localization, it did not reverse the invasion deficiency of Δspatrparasites, because of an apparent failure in secretion. Overall, the results suggest that TgSPATR contributes to invasion and virulence, findings that have implications for the many genera and life stages of apicomplexans that express SPATR.
Sialic acids acquired byPseudomonas aeruginosaare involved in reduced complement deposition and siglec mediated host-cell recognition