Antibody response specific to the capsular polysaccharide is impaired in Streptococcus suis serotype 2-infected animals.
Streptococcus suis serotype 2 is an extracellular encapsulated bacterium that causes severe septicemia and meningitis in swine and humans. Albeit crucial in the fight against encapsulated bacteria, the nature of the capsular polysaccharide (CPS)-specific antibody (Ab) response during S. suis type 2 infection is unknown. We compared for the first time the features of CPS-specific versus protein-specific Ab responses during experimental infections with live virulent S. suis type 2 in mice. The primary protein-specific Ab response was dominated by both type 1 and 2 IgG subclasses, whereas IgM titers were more modest. The secondary protein-specific Ab response showed all of the features of a memory response with faster kinetics and boosted the titers of all Ig isotypes. In contrast, the primary CPS-specific Ab response was either inexistent or had titers only slightly higher than those in noninfected animals and was essentially composed of IgM. A poor CPS-specific memory response was observed, with only a moderate boost in IgM titers and no IgG. Both protein- and CPS-specific Ab responses were Toll-like receptor 2 independent. By using S. suis type 2 strains of European or North American origin, the poor CPS-specific Ab response was demonstrated to be independent of the genotypic/phenotypic diversity of the strain within serotype 2. Finally, the CPS-specific Ab response was also impaired and lacked isotype switching in S. suis-infected pigs, the natural host of the bacterium. The better resistance of preinfected animals to reinfection with the same strain of S. suis type 2 might thus more likely be related to the development of a protein rather than CPS Ab response.
Laboratory of Immunology, Faculty of Veterinary Medicine, University of Montreal, Saint-Hyacinthe, Quebec, Canada.
Cynthia
C
Calzas
Laboratory of Immunology, Faculty of Veterinary Medicine, University of Montreal, Saint-Hyacinthe, Quebec, Canada.
Paul
P
Lemire
Laboratory of Immunology, Faculty of Veterinary Medicine, University of Montreal, Saint-Hyacinthe, Quebec, Canada.
Gael
G
Auray
Vaccine and Infectious Disease Organization (VIDO) and Department of Veterinary Microbiology, Western College of Veterinary Medicine, University of Saskatchewan, Saskatchewan, Canada.
Volker
V
Gerdts
Laboratory of Immunology, Faculty of Veterinary Medicine, University of Montreal, Saint-Hyacinthe, Quebec, Canada.
Marcelo
M
Gottschalk
Laboratory of Immunology, Faculty of Veterinary Medicine, University of Montreal, Saint-Hyacinthe, Quebec, Canada mariela.segura@umontreal.ca.
Mariela
M
Segura
D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood*; D000917:Antibody Formation; D001426:Bacterial Proteins / Q000276:immunology; D004195:Disease Models, Animal; D005260:Female; D007075:Immunoglobulin M / Q000097:blood; D007156:Immunologic Memory; D008810:Mice, Inbred C57BL; D011135:Polysaccharides, Bacterial / Q000276:immunology*; D065288:Serogroup; D013290:Streptococcal Infections / Q000276:immunology* / Q000382:microbiology*; D017011:Streptococcus suis / Q000145:classification / Q000276:immunology*; D013552:Swine
D000907:Antibodies, Bacterial; D001426:Bacterial Proteins; D007075:Immunoglobulin M; D011135:Polysaccharides, Bacterial