Fig. 4: SPy_2191 immunization reduced organ load post-challenge with different GAS serotypes.

Two weeks after the final booster immunization with SPy_2191, C57BL/6 mice were challenged intraperitoneally with different GAS serotypes. Four days post-challenge, three mice from both SPy_2191-immunized and placebo groups were sacrificed, and the bacterial load (represented as Log₁₀ CFU) was enumerated in the liver, lungs, spleen and skin. a–d and e represents data of different organ load after challenge with M49/IND, M1/IND, M3.1/IL, M1/USA, and M1/UK serotypes, respectively. Red bar represents CFUs obtained from PBS control mice and blue bar represents CFUs obtained from SPy_2191-immunized mice. In case of all the organs, across all the infected serotypes, SPy_2191 effectively reduced the bacterial load compared to the placebo group (minimum significance p < 0.01). f The nasopharyngeal streptococcal load in SPy_2191 and PBS-immunized mice (n = 6), 5 days post-intranasal challenge with GAS M9/UK (**P < 0.01). Data are presented as mean values ± SEM. The level of significance was checked by using two-tailed unpaired t-test.