Could IgM be more important than previously thought against S. suis?
In a mouse model of S. suis, T-cell-dependent IgM played a major role in bacterial clearance, a mechanism that still requires translation to pigs.
In a mouse model of S. suis, T-cell-dependent IgM played a major role in bacterial clearance, a mechanism that still requires translation to pigs.
Problem: The humoral mechanisms responsible for clearing S. suis remain incompletely understood, limiting rational vaccine design.
Methods: Researchers used a mouse model of S. suis serotype-2 infection, repeated infections, several genetically deficient mouse lines, and opsonophagocytosis assays to dissect the contributions of B cells, T cells, IgM, and IgG.
1. Germinal centers peaked approximately 13 to 21 days after infection, and antibodies directed against capsular polysaccharide were predominantly IgM.
2. Removing IgG from serum did not impair bacterial killing, whereas T-cell- or B-cell-deficient mice were much less able to control bacteremia.
3. The results identify a major role for T-cell-dependent IgM, but this mechanism was demonstrated in mice and is not direct evidence of vaccine efficacy in pigs.
Original publication
Dolbec D, Lehoux M, et al. Unmutated but T cell dependent IgM antibodies targeting Streptococcus suis play an essential role in bacterial clearance. PLOS Pathogens. 2024;20(1):e1011957.