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Summary: Vibrio cholerae is an aquatic bacterium that causes severe and potentially deadly diarrheal disease. Despite the impact on global health, our understanding of host mucosal responses to Vibrio remains limited, highlighting a knowledge gap critical for the development of effective prevention and treatment strategies. Using a natural infection model, we combine physiological and single-cell transcriptomic studies to characterize conventionally reared adult zebrafish guts and guts challenged with Vibrio. We demonstrate that Vibrio causes a mild mucosal immune response characterized by T cell activation and enhanced antigen capture; Vibrio suppresses host interferon signaling; and ectopic activation of interferon alters the course of infection. We show that the adult zebrafish gut shares similarities with mammalian counterparts, including the presence of Best4+ cells, tuft cells, and a population of basal cycling cells. These findings provide important insights into host-pathogen interactions and emphasize the utility of zebrafish as a natural model of Vibrio infection.

ABSTRACT The type 1 interferon-regulated E3 ubiquitin ligase MARCH1 reduces surface expression of HIV-1 envelope glycoproteins (Env) and their packaging into nascent virions, a condition that restricts viral infectivity. However, how HIV-1 counters this restriction, notably during infection of macrophages, remains unclear. Here, we show that the HIV-1 accessory protein Vpu increases the levels of microRNAs-25 and -93 to target MARCH1 mRNA. By recruiting β-TRCP, a component of the SCFβ-TRCP E3 ligase complex that targets phosphorylated β-catenin for degradation, Vpu increases β-catenin levels, which, in concert with TCF4/LEF, drives transcription of the MARCH1-targeting microRNAs. This potentiates HIV-1 infectivity as a result of increased Env incorporation into nascent virions. Pharmacological targeting of the β-catenin pathway inhibits Vpu-mediated upregulation of microRNAs-25 and -93 and restores MARCH1 restriction on HIV-1 infectivity. Overall, our findings highlight a novel mechanism by which HIV-1 counteracts MARCH1 by downregulating its expression via Vpu-mediated induction of microRNAs-25 and -93. IMPORTANCE In order to efficiently produce infectious viral particles, HIV must counter several restrictions exerted by host cell antiviral proteins. MARCH1 is a member of the MARCH protein family that restricts HIV infection by limiting the incorporation of viral envelope glycoproteins into nascent virions. Here, we identified two regulatory RNAs, microRNAs-25 and -93, induced by the HIV-1 accessory protein Vpu, that downregulate MARCH1 mRNA. We also show that Vpu induces these cellular microRNAs in macrophages by hijacking the cellular β-catenin pathway. The notion that HIV-1 has evolved a mechanism to counteract MARCH1 restriction on viral infectivity underlines the importance of MARCH1 in the host antiviral response.