3.3. Flagellin-specific antibodies were induced in mice
immunized with the recombinant B. longum
We next assessed if the recombinant B. longum could elicit
the humoral immune responses in mice. Since the local humoral
immune response at mucosa is mediated predominantly by secretory
IgA antibody, we examined the production of anti-flagellin
specific IgA in the feces. Systemic immune response was also analyzed
via measuring IgA, IgG, and IgM in the sera. Mice were orally
administered with recombinant B. longum (group 1). Parental B.
longum (group 2), or PBS (group 3) and the level of anti-flagellin
antibody were measured by ELISA. Recombinant B. longum, administered
every other day for 4 weeks, induced significantly higher
levels of anti-flagellin IgA antibody in feces at days 11, 14, and 28
as compared with the parental B. longum or PBS groups (Fig. 5).
Also, significant levels of anti-flagellin serum-antibodies IgA, IgG,
and IgM were observed in group 1 at days 14 and 28 as compared
with the other groups (Fig. 6a, b, c).