Multivalent vaccines….why not protect against multiple diseases in a single vaccine.
How a single vectored vaccine can protect against multiple diseases
The paper in Nature Communications is here: https://go.nature.com/2IIONip
In late 2015, news of Zika virus and the havoc this one virus was causing first started emerging. The headlines were sensational accompanied by graphic images of babies with microcephaly. As more and more news surfaced about explosive numbers of cases involved, rapid spread of the virus and unusual clinical presentations in the form of sexual transmission and viral persistence, it was evident that a concerted global effort was underway to combat Zika virus. Or more simply put, everyone wanted to jump on the Zika train.
So what business does a group of Australian scientists have to contribute to development of Zika virus vaccines? We don’t have an emergency response funding mechanism in Australia, so how will we fund the development of a Zika virus vaccine and how would we be competitive? Team Sementis is essentially Nemo in a vast ocean of bigger fish. And at the time, I was just starting an Industry-linked fellowship focused on fast-tracking a Chikungunya virus vaccine through to clinical trials? A mosquito-transmitted virus also causing global health issues. So, do we change our focus to Zika virus vaccine development now or can I do both? “Ok well let’s just add Zika to the existing Chikungunya virus vaccine”, Paul Howley, CSO and CEO of Sementis suggests.
And the quest for a single vectored, multi-disease vaccine begins. And why not?
Chikungunya and Zika viruses co-circulate together and are transmitted by the same mosquito vectors. There is also recent evidence to suggest that while Zika virus has been associated with a wide range of neurological conditions, chikungunya virus may have an equally important association with neurological disease, as many patients are infected with both viruses (Mehta et al., 2018). Therefore, it would make logical sense that humans at risk of Zika virus would also be at risk of the Chikungunya virus. So off we set as a team to produce a vaccine candidate using the SCV platform technology previously published in Molecular Therapy (Eldi et al., 2017). We evaluated whether the vaccine could induce protective immunity in adult mice, in pregnancy and interrupt testis destruction. But perhaps more importantly, we also ensured that the viral antigens leading to protective immunity for Zika did not negative affect immunity induced by Chikungunya and vice versa. In other words, there was no antigenic interference affecting vaccine efficacy.
So why aren’t there any single-vectored, multi disease vaccines on the market? Many infectious diseases or viral infections co-circulate together. The Sementis single-vectored Zika and Chikungunya virus vaccine candidate was the first proof-of-principle product that a single-vectored approach could work for multiple diseases.
Stay tuned to see how many viral antigens we can engineer into the SCV platform and attempt to revolutionize vaccinology as we know it.