CD40LG and Salmonella Infections: However, despite the plausible defects that occur in the absence of FruR, the ΔfruR mutant strain, as a prophylactic vaccine, was able to stimulate IgG and IgM production more promptly and strongly than were the WT and ΔssrAB mutant strains, and afforded the best protection capacity among the tested strains against lethal Salmonella infection.