Membrane-Associated Ring-CH (MARCH) family proteins were recently reported to inhibit viral replication through multiple modes of action. Previous work proved that human MARCH8 blocked Ebola virus (EBOV) glycoprotein (GP) maturation. Our study here demonstrates that human MARCH1 and MARCH2 share a similar pattern to MARCH8 in restricting EBOV GP-mediated viral replication. Human MARCH1 and MARCH2 retain EBOV GP in the trans-Golgi network (TGN), reduce its surface display, and impair EBOV GP-pseudotyped virions infectivity. Furthermore, we uncover that the host proprotein convertase (PC) furin could interact with human MARCH1/2 and EBOV GP intracellularly. Importantly, the furin P domain is confirmed to be recognized by MARCH1/2/8, which is critical for their blocking activities. Besides, bovine MARCH2 and murine MARCH1 also impair EBOV GP proteolytic processing. Altogether, our findings confirm that MARCH1/2 proteins of different species showed a relatively conserved feature in blocking EBOV GP proteolytic processing, which could provide a reference for subsequent antiviral studies and may facilitate the development of novel strategies to antagonize enveloped virus infection.

Background: Norovirus (NoV) is a leading cause of epidemic non-bacterial acute gastroenteritis in young children and adults globally. Snow Mountain Virus (SMV), the prototype of genogroup II and genotype II NoV, has been used in three human challenge studies to examine the infectivity, pathogenicity, and immune response to NoV. Methods: This is a secondary data analysis. Clinical and laboratory data from two previously completed SMV human challenge trials using two different inocula (Inoculum 1 and Inoculum 2) were analyzed to compare infectivity, illness (including modified Vesikari severity scores of gastroenteritis in those subjects with clinical symptoms), viral shedding, and serum IgG conversion. SMV Inoculum 2 is a second-generation inoculum prepared from a stool sample collected from a study subject who was infected with SMV Inoculum 1. Results: Of 15 subjects orally challenged with SMV Inoculum 1 between 2000 and 2002, nine were infected, and seven presented with acute gastroenteritis. Of 33 subjects orally challenged with SMV Inoculum 2 between 2016 and 2018, 25 were infected, and nine presented with acute gastroenteritis. There were no statistically significant differences in overall infection and illness rates between subjects challenged with Inoculum 1 vs. Inoculum 2. However, subjects infected with Inoculum 1 experienced more severe clinical symptoms of acute gastroenteritis and had higher severity scores (6.00 vs. 2.94, P = 0.003) compared with those infected with Inoculum 2. We also observed that infection with Inoculum 2 resulted in longer viral shedding compared with Inoculum 1. This analysis also indicated that secretor-positive subjects had more severe gastroenteritis than secretor-negative subjects. Among ill subjects, no association was observed between challenge dose and severity of acute gastroenteritis. Conclusions: Understanding the differences between these two SMV inocula is critical for NoV vaccine evaluation because illness and viral shedding are two important outcomes in NoV challenge studies to determine vaccine efficacy. Using a less pathogenic inoculum for a vaccine trial will require more participants to meet the target reduction in illness when evaluating the efficacy of candidate vaccines.