Novel vaccine design for preventing Streptococcus suis in swine

Streptococcus suis, a bacterium covered by a “sugar coat” (e.g. capsular polysaccharide), kills young pigs, resulting in significant economic problems for the global swine industry. Contaminated animals or pork can transmit disease to humans. In Thailand, S. suis is the second most important cause of adult meningitis and high numbers (6.4/100,000 persons) of cases (fatal and non-fatal) are continuously reported. Preventing pig diseases not only has a positive economic impact, it also improves animal welfare and reduces human cases. However, there are no effective commercial vaccines against S. suis available.

The objective of this project is to design the first chemically-synthesized S. suis capsular polysaccharide-based vaccine and provide proof-of-concept of its protective capacity. Capsular polysaccharide antigen fragments (epitopes) will be selected, chemically synthesized, and linked to a carrier protein generating "glycoconjugates". By lowering production costs, novel chemical synthesis overcomes the limitations of conventional glycoconjugate vaccines. The immunogenic and protective capacities of different glycoconjugate prototypes and adjuvant formulations will be sequentially characterized in well-controlled animal-challenge models under laboratory conditions and, finally, under field-like conditions using an experimental farm system in Thailand.

The potential impact is the development of an innovative vaccine solution to control S. suis infections and reduce antimicrobial use in livestock production in Thailand. This strategy can be applied to other low and middle-income countries where S. suis is a major problem.