VIPR1 and infection: HVR1 is a target for neutralizing antibodies in natural infections (Weiner et al., 1992; Zibert et al., 1995) and many anti-HVR1 antibodies are able to neutralize HCV infections in vitro and in vivo, as demonstrated in the HCVpp and chimpanzee models (Bartosch et al., 2003a; Farci et al., 1996; Hsu et al., 2003).