Necroptosis does not drive disease pathogenesis in a mouse infective model of SARS-CoV-2 in vivo.

Necroptosis, a type of lytic cell death executed by the pseudokinase Mixed Lineage Kinase Domain-Like (MLKL) has been implicated in the detrimental inflammation caused by SARS-CoV-2 infection. We minimally and extensively passaged a single clinical SARS-CoV-2 isolate to create models of mild and severe disease in mice allowing us to dissect the role of necroptosis in SARS-CoV-2 disease pathogenesis. We infected wild-type and MLKL-deficient mice and found no significant differences in viral loads or lung pathology. In our model of severe COVID-19, MLKL-deficiency did not alter the host response, ameliorate weight loss, diminish systemic pro-inflammatory cytokines levels, or prevent lethality in aged animals. Our in vivo models indicate that necroptosis is dispensable in the pathogenesis of mild and severe COVID-19.

Conservation, abundance, glycosylation profile, and localization of the TSP protein family in Cryptosporidium parvum.

Cryptosporidium parvum is a zoonotic apicomplexan parasite and a common cause of diarrheal disease worldwide. The development of vaccines to prevent or limit infection remains an important goal for tackling cryptosporidiosis. At present, the only approved vaccine against any apicomplexan parasite targets a conserved adhesin possessing a thrombospondin repeat domain. C. parvum possesses 12 orthologous thrombospondin repeat domain-containing proteins known as CpTSP1-12, though little is known about these potentially important antigens. Here, we explore the architecture and conservation of the CpTSP protein family, as well as their abundance at the protein level within the sporozoite stage of the life cycle. We examine the glycosylation states of these proteins using a combination of glycopeptide enrichment techniques to demonstrate that these proteins are modified with C-, O-, and N-linked glycans. Using expansion microscopy, and an antibody against the C-linked mannose that is unique to the CpTSP protein family within C. parvum, we show that these proteins are found both on the cell surface and in structures that resemble the secretory pathway of C. parvum sporozoites. Finally, we generated a polyclonal antibody against CpTSP1 to show that it is found at the cell surface and within micronemes, in a pattern reminiscent of other apicomplexan motility-associated adhesins, and is present both in sporozoites and meronts. This work sheds new light on an understudied family of C. parvum proteins that are likely to be important to both parasite biology and the development of vaccines against cryptosporidiosis.