Evaluation of Bioinformatically Designed, Historical Glycoproteins to Aid Pan-Lyssavirus Vaccine Development

Purpose: Without pre- or post-exposure prophylaxis, lyssaviruses cause rabies, an invariably fatal disease responsible for over 59,000 human deaths per year. Rabies virus (RABV) is a lyssavirus, a genus comprising of 17 viral species all capable of causing rabies disease. The lyssavirus genus has been proposed to split into three phylogroups based on genetic and antigenic properties. Studies have demonstrated that current RABV vaccines only confer protection against phylogroup I lyssaviruses indicating a novel vaccine antigen would be required to achieve coverage against all lyssavirus species.The genetic sequence of historic viruses from before the genus split into multiple phylogroups can be predicted from genetic group relationships. Predictions of related or conserved sequences of immune eliciting proteins, such as glycoproteins (G), may be useful for designing vaccines that stimulate broader immunity than those employing contemporary G from single isolates. Whilst this approach has proven successful for other, closely related, viral species, it's unknown how beneficial it would be for a genus as broad as the lyssaviruses. Methods & Materials: We analysed publically available lyssavirus G genes to generate a panel of 15 conserved lyssavirus G sequences. These G were combined with a HIV pseudotyping system and the resulting pseudotyped viruses (PV) assessed in infection assays to determine conserved protein functionality. Neutralisation profiles of historic G PV and PV bearing G from current vaccine and wildtype isolates were determined with lyssavirus sera representative of the proposed phylogroups. Results: Two thirds of the historical G were functional and generated sufficiently high PV titres for further assessment. Neutralisation assays using the panel of lyssavirus sera revealed different patterns of inhibition for the conserved G. Conclusion: These results show the potential for using conserved G as a pan-lyssavirus vaccine candidate.