H ANTIGEN OFSALMONELLA TYPHOSA

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Abstract
Nonmotile variants of W form Salmonella typhosa have been recovered from the brains of mice following intracerebral inoculation with motile W form typhoid bacilli. Sero-logical studies on these variants showed them to be deficient in, or devoid of, the H antigen component. No Vi antigen could be detected. Results of intracerebral virulence tests with these organisms have shown that the loss of H antigen was not associated with loss of virulence but, on the contrary, the virulence of organisms deficient in this component was either unaffected or slightly increased. Active and passive mouse protection tests employing various acetone-killed and dried cell vaccines and antisera to these vaccines demonstrated that neither H antigen nor H antibody were effective in protecting against V or W form challenges. Only a Vi-containing vaccine or a Vi antiserum afforded protection against the V challenge. It was not possible to distinguish between V and W form typhoid bacilli vaccines, either actively or passively, with a W form challenge.