Synthetically derived bat influenza A-like viruses reveal a cell type- but not species-specific tropism

Abstract

<p id="d6499814e317">Since the discovery of bat influenza A-like genomic sequences (provisionally designated HL17NL10 and HL18NL11), it was uncertain whether these sequences encode infectious viruses and, if so, which cells might support propagation of these viruses. Using chimeric vesicular stomatitis virus (VSV) encoding HL18 or HL17, a particular cell line of canine origin was found to be highly susceptible to infection. Taking advantage of this cell line, we succeeded to generate recombinant HL17NL10 and HL18NL11. These viruses revealed marked differences to conventional influenza A viruses because they do not use the same receptor, in addition to initiating infection from the basolateral site of polarized epithelial cells. The established reverse genetic system will undoubtedly help characterizing these hitherto uncultivable viruses. </p><p class="first" id="d6499814e320">Two novel influenza A-like viral genome sequences have recently been identified in Central and South American fruit bats and provisionally designated “HL17NL10” and “HL18NL11.” All efforts to isolate infectious virus from bats or to generate these viruses by reverse genetics have failed to date. Recombinant vesicular stomatitis virus (VSV) encoding the hemagglutinin-like envelope glycoproteins HL17 or HL18 in place of the VSV glycoprotein were generated to identify cell lines that are susceptible to bat influenza A-like virus entry. More than 30 cell lines derived from various species were screened but only a few cell lines were found to be susceptible, including Madin–Darby canine kidney type II (MDCK II) cells. The identification of cell lines susceptible to VSV chimeras allowed us to recover recombinant HL17NL10 and HL18NL11 viruses from synthetic DNA. Both influenza A-like viruses established a productive infection in MDCK II cells; however, HL18NL11 replicated more efficiently than HL17NL10 in this cell line. Unlike conventional influenza A viruses, bat influenza A-like viruses started the infection preferentially at the basolateral membrane of polarized MDCK II cells; however, similar to conventional influenza A viruses, bat influenza A-like viruses were released primarily from the apical site. The ability of HL18NL11 or HL17NL10 viruses to infect canine and human cells might reflect a zoonotic potential of these recently identified bat viruses. </p>