Major histocompatibility complex class II (MHC-II) molecules of multiple species function as cell-entry receptors for the haemagglutinin-like H18 protein of the bat H18N11 influenza A virus, enabling tropism of the viruses in a potentially broad range of vertebrates. However, the function of the neuraminidase-like N11 protein is unknown because it is dispensable for viral infection or the release of H18-pseudotyped viruses. Here, we show that infection of mammalian cells with wild-type H18N11 leads to the emergence of mutant viruses that lack the N11 ectodomain and acquired mutations in H18. An infectious clone of one such mutant virus, designated rP11, appeared to be genetically stable in mice and replicated to higher titres in mice and cell culture compared with wild-type H18N11. In ferrets, rP11 antigen and RNA were detected at low levels in various tissues, including the tonsils, whereas the wild-type virus was not. In Neotropical Jamaican fruit bats, wild-type H18N11 was found in intestinal Peyer’s patches and was shed to high concentrations in rectal samples, resulting in viral transmission to naive contact bats. Notably, rP11 also replicated efficiently in bats; however, only restored full-length N11 viruses were transmissible. Our findings suggest that wild-type H18N11 replicates poorly in mice and ferrets and that N11 is a determinant for viral transmission in bats.
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The data supporting the findings of this study are available within the paper and its Supplementary Information. Any further relevant data are available from the corresponding authors on reasonable request.
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We thank S. Schuparis and G. Czerwinski for histotechnological support and S. Giese and H. Bolte for reading the manuscript. This work was supported by grants from the DFG to M.S. (SCHW 632/17-2) and M.B. (BE 5187/4-2); the CRIP and the Saint Jude CEIRS, two NIAID-funded CEIRS to A.G.-S. (HHSN272201400008C) and W.M. (HHSN272201400006C), respectively; NIH NIAID grants to G.D.E. (AI067380), R.A.M. (AI134108), W.M. and T.S. (1R01AI134768); the CSU Vice President for Research, College of Veterinary Medicine and Biomedical Sciences, and Department of Microbiology, Immunology and Pathology to T.S.; and the China Scholarships Council (201506170046) to W.R. The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.
The authors declare no competing interests.
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