The Vaccine Group is expanding its repertoire of vaccine candidates as it seeks to maximise the potential of its platform herpesvirus gene delivery system. Following the move into important diseases of commercial livestock in recent years TVG has now begun to explore the opportunities presented by the companion animal sector. The common element to each of these new diseases areas to TVG is that previously developed vaccines are viewed in the market as inadequate in ways that our technology can specifically address, whether that is lack of efficacy, safety, production capability or duration of immunity. In each approach TVG has worked with key opinion leaders in their specific disease areas to identify key target antigens before the creation of novel candidate vaccine constructs.
In the companion animal area TVG has initiated in vitro work to demonstrate the ability of its vector and constructs to replicate and stably express the inserted genes of interest. The targets for improved vaccines in this space are for canine leishmaniasis, which is a specific problem around the Mediterranean rim countries of southern Europe and north Africa, and equine influenza and feline immunodeficiency virus, both of which are global disease entities that routinely develop strain variants.
In the livestock field TVG has added a porcine cysticercosis (PC) vaccine project to its growing pig vaccine range to complement established projects on porcine reproductive and respiratory syndrome, porcine circovirus-2 and African swine fever vaccines. PC is a specific problem in Low- and Middle-Income Countries in extensive pig rearing situations, where carcass quality and therefore value is affected by infection with the pork tapeworm cysts.
Bovine respiratory syncytial virus is the leading cause of respiratory disease in young calves and is associated with milk drop in dairy herds. Use of existing vaccines in young calves is complicated by maternally-derived immunity compromising efficacy in very early life, and the duration of immunity and risk of shedding of attenuated vaccine strains are seen as detrimental characteristics of commercial vaccines.
Lumpy skin disease has become a widespread concern in cattle from Europe to China in the last ten years, having been confined to Africa largely for the previous fifty years. Eradication from previously disease and infection-free countries is now sought after and therefore a negatively-marked vaccine (DIVA compatible) like the candidate that TVG is developing will be very helpful. None of the available vaccines offer this possibility.
TVG’s chlamydia abortus vaccine candidate allows production in standard tissue culture rather than embryonated eggs, and is expected to have a strong safety profile as it does not rely upon attenuation to modify its pathogenicity, as is the case with the commercial live, attenuated vaccine.
Successful demonstration of proof-of-principle with this new wave of vaccine candidates will demonstrate the tuneable nature of the herpesvirus vaccine vector platform that TVG employs, whilst expanding TVG’s target species range significantly.