Passive protection of rabbits infected with toxic shock syndrome-associated strains of Staphylococcus aureus by monoclonal antibody to toxic shock syndrome toxin 1.

The effectiveness of passive immunization was assessed in an infection model of toxic shock syndrome (TSS) in which monoclonal antibody to TSS toxin 1 (TSST-1) was administered intravenously to rabbits. Previously implanted infection chambers were inoculated with Staphylococcus aureus strains RN4710 and D4508. The former strain carries the TSST-1 gene on plasmid pRN6201; the latter is a TSST-1-negative clinical isolate obtained from a patient with nonmenstrual TSS. Purified monoclonal antibody, MAb 8-5-7 (IgG), was administered in two doses of approximately 1.25 mg each 24 hours before and 24 hours after infection. MAb 8-5-7 provided complete protection against both the TSS-like syndrome and the mortality that occurred in unprotected rabbits infected with strain RN4710 but did not provide complete protection in rabbits infected with strain D4508; three of the five rabbits either displayed signs of illness or died despite treatment. Western-blot analyses of the extracellular proteins produced by strains RN4710 and D4508 that used MAb 8-5-7 as a probe revealed that only TSST-1 produced by RN4710 reacted with the antibody. Thus, if MAb 8-5-7 partially protected animals against infections with strain D4508, the protection appears to have been nonspecific.