EPAS1 and infection: Thus, we conclude (1) that a functional V-ATPase is indispensable for FV infection and (2) that the insertion of loxP sites flanking exon 2 of the Hif-2a gene in Hif-2afl and Hif-1afl×Hif-2afl mice results in reduced expression and function of V-ATPase preventing the infection with FV.