Studies of the protective effect of different fractions of sera from pigs immune to Streptococcus suis type 2 infection

Abstract

Inoculation of mice with high doses of Streptococcus suis type 2 caused depression, anorexia, lethargy and sometimes death. This was prevented by prior inoculation of whole immune pig serum, the IgM and IgG fractions of immune pig serum and serum enriched with antibody to surface antigens. Clinical signs were not prevented by prior inoculation of pre-immune serum or serum depleted of antibody to surface antigens. Serum fractions that were protective in vivo were also opsonic in vitro. Western blot analysis identified two antigens of 44 and 78 kd that were recognized strongly by protective sera and a further four of 86, 94, 130 and 136 kd that were recognized less intensely.