The One Health concept describes the relationship between human health, animal health and the environment, and recognizes how the interplay in this triad have led to the emergence and re-emergence of many diseases. Since 75% of known diseases are of animal origin and 60% of these affect humans, it is vital to combat animal pathogens to prevent zoonoses and sustain both animal and human health. It is for this reason that Afrigen serves both human- and veterinary vaccine developers. For veterinary vaccines, our core focus is on livestock zoonotic diseases and livestock diseases with high morbidity and mortality rates.
Inactivated- and live-attenuated vaccines are self-adjuvanted, whereas recombinant- and subunit vaccines require adjuvants to elicit potent immune responses due to the absence of pathogen-associated molecular patterns to which immune cells’ pathogen recognition receptors bind. Since the early 1920s, aluminium salts (i.e. aluminium oxyhydroxide and -phosphate) have been the adjuvant of choice for human vaccines due to its favourable safety profiles. Several next generation adjuvants are licensed (e.g. virosomes, MF59, R837/R848, AS04 and AS03) or in clinical trials (e.g. poly IC:LC, MDP, MPL, CpG ODN AS01, flagellin and AS02) for human vaccines. The use of next generation adjuvant formulations with TLR agonists are now more frequently used in human vaccine development. Next generation adjuvants in licensed human vaccines include MF59 (Fluad®), AS03 (Pandemrix®) and virosomes (Epaxal®, Inflexal® V) for influenza; AS04 (MPL+alum; CervarixTM) for human papilloma virus; and imidazoquinolines (e.g. imiquimod and resiguimod; AldaraTM) for topical applications. Next generation adjuvants in clinical trials for human vaccines include AS01 and AS02 (MPL+QS21) and saponin (QS21) for malaria, and GLA-SE (lipid A analogue) for TB. TLR agonists are formulated in emulsions and liposomes.
In veterinary vaccine development, there is a trade-off between immunogenicity,safety and affordability. Veterinary vaccine developers are now increasingly using the same recombinant technologies used in human vaccine development and also therefore require more potent adjuvants. The benefits of next-generation adjuvants have extensively been demonstrated commercialised human vaccines and there has been an increase in the use of these adjuvant technologies in veterinary vaccine research. The most attractive benefits of using next-generation adjuvants to veterinary vaccine developers are the antigen-sparing effects, and that some of these adjuvants are capable of inducing cellular immune responses that can clear intracellular pathogens.
There is no clear universal adjuvant system for animal diseases, and they must be adapted according to the target host species. Each case needs to be investigated individually, as several factors need to be considered to decide which adjuvant formulation to use. For this purpose, different formulations and/or emulsions have been developed.
Afrigen has partnered with Afrivet to develop vaccines against some of Africa’s most serious livestock diseases. We are also working with other collaborators on a range of projects that aim to improve either existing or newly developed veterinary vaccines in multiple hosts, including sheep, cattle, chicken and horses. We are working on vaccines against viral, bacterial and parasitic infections
Next-generation adjuvants may also be used as a stand-alone product, for stimulation of the immune system in a non-specific manner. This may be used at times of perceived stressful events or when animals are at risk of infection. This is sometimes referred to as host-directed therapy and has been shown to reduce the symptoms associated with certain livestock diseases and decreased the need for antibiotics. Afrigen is currently developing immunomodulators to boost the host’s immune response in companion animals.