Immunogenicity of whole cell and outer envelope leptospiral vaccines in hamsters

The immunogenicity of leptospiral whole cell (WC) and outer envelope (OE) vaccines from virulent and avirulent strains was compared in hamsters. The 50% protective dose against death (PD(50D)) and kidney infection (PD(50K)) was evaluated for serotypes icterohaemorrhagiae, canicola, pomona, and grippotyphosa. The OE and WC of virulent strains possessed greater immunogenicity than the OE and WC of avirulent strains. More vaccine (<0.1 to 11.0 mug [dry weight] per hamster) was required for the PD(50K) than for the PD(50D) (<0.1 to 1.7 mug [dry weight] per hamster). The OE from virulent strains of these four serotypes plus hardjo were combined to form a pentavalent OE vaccine which proved to be satisfactory in immunogenic potency. Duration of immunity was not evaluated.