Utilisation of Chimeric Lyssaviruses to Assess Vaccine Protection against Highly Divergent Lyssaviruses

Abstract

Lyssaviruses constitute a diverse range of viruses with the ability to cause fatal encephalitis known as rabies. Existing human rabies vaccines and post exposure prophylaxes (PEP) are based on inactivated preparations of, and neutralising antibody preparations directed against, classical rabies viruses, respectively. Whilst these prophylaxes are highly efficient at neutralising and preventing a productive infection with rabies virus, their ability to neutralise other lyssaviruses is thought to be limited. The remaining 15 virus species within the lyssavirus genus have been divided into at least three phylogroups that generally predict vaccine protection. Existing rabies vaccines afford protection against phylogroup I viruses but offer little to no protection against phylogroup II and III viruses. As such, work involving sharps with phylogroup II and III must be considered of high risk as no PEP is thought to have any effect on the prevention of a productive infection with these lyssaviruses. Whilst rabies virus itself has been characterised in a number of different animal models, data on the remaining lyssaviruses are scarce. As the lyssavirus glycoprotein is considered to be the sole target of neutralising antibodies we generated a vaccine strain of rabies using reverse genetics expressing highly divergent glycoproteins of West Caucasian Bat lyssavirus and Ikoma lyssavirus. Using these recombinants, we propose that recombinant vaccine strain derived lyssaviruses containing heterologous glycoproteins may be a suitable surrogate for wildtype viruses when assessing vaccine protection for the lyssaviruses.

Assessing Rabies Vaccine Protection against a Novel Lyssavirus, Kotalahti Bat Lyssavirus

“…Growth kinetic assessment of this virus revealed that despite a successful virus rescue, endpoint titres achieved were significantly different with cSN-KBLV reaching a lower final titre compared to the parent cSN virus (Figure 1). However, the titre achieved was still higher than titres achieved in previous studies whereby more divergent glycoproteins were introduced into the same cSN backbone [31]. Decreased viral fitness of cSN-KBLV may be a result of cSN being more adapted to cell culture or a result of the parent virus (KBLV) being less able to replicate in cell culture models than the recombinant virus.…”

“…Harvested virus was titrated in which the cSN-KBLV grew to a peak titre of 2.5 × 10 4 ffu/mL whilst the parent cSN strain grew to a peak titre of 1.6 × 10 6 ffu/mL. Both values, however, are comparable to similar studies using EBLV-1, EBLV-2 G, IKOV G, and WCBV G within a cSN vector [30,31].…”

“…Virus rescue for cSN-KBLV was undertaken as described previously [30,31]. Briefly, BSR-T7/5 cells were seeded at 3 × 10 4 cells per well in a 96-well plate (Corning, High Wycombe, UK) 18 h before transfection and 200 ng of the full-length genome plasmid and 40 ng of each of three helper plasmids, encoding the RABV N, P, and L proteins, were transfected into cells using the FuGENE ® 6 Transfection Reagent (Promega, Southampton, UK).…”

“…The lyssavirus glycoprotein (G) is the only viral surface protein and is the sole target for neutralising antibodies [28]. Previous studies have utilised reverse genetics (RG) techniques to exchange G proteins derived from other lyssavirus species into a RABV vaccine RG backbone to enable assessment of vaccine protection against recombinant viruses [29][30][31].…”

Lyssavirus Vaccine with a Chimeric Glycoprotein Protects across Phylogroups

“…There are a variety of ways to broaden a vaccine’s protective breadth, some of which have been attempted for lyssaviruses. A straightforward approach is to create multiple vaccine constructs, each expressing a separate lyssavirus G ( Evans et al., 2018b ), but this strategy would multiply the cost of a vaccine already deemed too expensive for the regions that need it most ( van de Burgwal et al., 2017 ). Furthermore, one lyssavirus G might be immunodominant over others.…”