Shigella and E.Coli are the two main causes of bacterial diarrhoea – accounting for one billion cases and 600,000 deaths per year. So far, a broad-based vaccine that protects against the various bacterial species that cause diarrhoea has eluded scientists. However, UK-based company, Prokarium, has developed an oral vaccine platform, Vaxonella, which includes several antigens against different bacteria in the same formulation, including Shigella and E.Coli – making it possible to produce a bacterial diarrhoea vaccine against several pathogens at low cost.
Diarrhoea is a problem often faced by rural communities and although there are many oral vaccines based on live attenuated organisms on the market, modern subunit vaccines are not amenable to oral delivery, and must be refrigerated and injected. This results in significant logistical and cost concerns – especially for warm or remote locations. Prokarium have managed to circumvent the cold chain problem by using engineered Salmonella bacteria. “Our vaccines are produced by engineered bacteria only once they are inside the body’s own immune cells. This means we don’t have to stabilize the protein vaccines, but rather ‘only’ have to stabilize the engineered bacteria,” says Prokarium CEO, Ted Fjällman. “By programming the bacteria to produce vaccine once they are engulfed by the immune cells, we trigger strong and broad immunity, with little or no side effects.” Prokarium have recently announced a collaboration with Mexican vaccine manufacturer, Probiomed, to scale up the production of the diarrhoea vaccine. The collaboration came about when Fjällman was visiting Mexico as part of a UK trade delegation in 2015. “We chose Probiomed because of their commitment to biopharma development, their manufacturing expertise, and their commercial reach in Mexico and Latin America, which could be key markets for the vaccine,” he says. In terms of scale up, Fjällman says the bacterial vector can be grown at large scale and packaged into capsules for consumption (as is done with a licensed typhoid vaccine, Vivotif). “The main challenge is to be able to perform the process with all the new excipients needed to stabilize the vaccine at high temperatures – and to do this consistently from batch to batch,” says Fjällman. “We also need to perfect the fill-finish process to minimize the number of capsules that a person would have to swallow in order to get the appropriate dose.”
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