Rabies human diploid cell vaccine elicits cross-neutralising and cross-protecting immune responses against European and Australian bat lyssaviruses

The ability of antibodies elicited against the rabies human diploid cell vaccine (HDCV) to neutralise European bat Lyssaviruses (EBLV types-1 and -2), Australian bat Lyssavirus and classical rabies virus (RABV) has been evaluated using modified fluorescent antibody virus neutralisation (mFAVN) assays. Ninety-six percent (48 of 50) of the human post-vaccinated sera tested cross-neutralised these viruses (≥0.5 IU/ml). Cross-protection experiments using inbred mice (RIII, k/k haplotype) were also assessed. Mice were given HDCV (twice by the intra-peritoneal route) and challenged (intra-cranially or peripherally) with a lethal dose (25 MLD50) of the individual viruses. The vaccine conferred statistically significant protection in 80–100% of animals challenged via the peripheral route. Levels of protection were lower following intra-cranial (i.c.) challenge. Our data provides strong evidence for broad spectrum cross-neutralisation and cross-protection of phylogroup I lyssaviruses using rabies HDCV.