EFFECT OF VACCINATION OF PONIES WITH A4 ANTIIDIOTYPIC ANTIBODY ON SERUM IDIOTYPE (1C9) AND ANTILIPID-A CONCENTRATION

Objective-To evaluate the humoral response of horses to vaccination, u sing a murine monoclonal anti-idiotypic antibody (A4) that shares an e pitope with lipid A. Design-Serum concentrations of antilipid A antibo dy and 1C9 (epitope on murine monoclonal antilipid A antibody) were me asured serially during the period of vaccination with A4. Animals-6 cl inically normal adult ponies. Procedure-Ponies were inoculated IM 3 ti mes at monthly intervals with A4. Two weeks after each inoculation, se rum was obtained and was assayed by ELISA for antilipid A and 1C9 conc entrations. Additional vaccinations were given to 2 of the ponies afte r a several-month rest period. Results-There was significant increase in 1C9 concentration (P < 0.0001) during the period of vaccination and a trend toward increased antilipid A concentration. The latter effect was not significant (P = 0.055). Additional vaccinations produced fur ther increase in serum 1C9 concentration; antilipid A concentration in creased in one of these ponies but not the other. Maximal antilipid A concentration recorded in these ponies was approximately 6 times preim mune concentration and was comparable to that found in a commercial an tiendotoxin antiserum. 1C9 also was detected in the commercial antiser um. Conclusions-A4 anti-idiotype vaccination of horses is safe and may be effective in eliciting an antibody response against endotoxin. The finding of 1C9 in a commercial antiendotoxin antiserum indicates that this idiotype may be part of the normal polyclonal antibody response of horses to endotoxin. Clinical Relevance-it may be possible to use a ntiidiotypic antibody vaccination in horses to induce protection again st the effects of endotoxoin.