Comparison of muramyl dipeptide, trehalose dimycolate, and dimethyl dioctadecyl ammonium bromide as adjuvants in Brucella abortus 45/20 vaccines.

The capacity of trehalose dimycolate (TDM), muramyl dipeptide (MDP), and dimethyl dioctadecyl ammonium bromide (DDA)--alone or in combination--to potentiate the immunogenicity of killed Brucella abortus 45/20 bacteria was studied in guinea pigs. Bacterins that contained TDM in oil droplet emulsion were as effective in the prevention of brucellosis as those emulsified in Freund complete adjuvant, wereas bacterins that contained a combination of TDM and MDP were most effective. Vaccinal emulsions of bacteria and MDP were ineffective in the prevention of splenic infections. Likewise, DDA was unable to potentiate acquired resistance to Brucella. Addition of DDA to 1% oil emulsions of bacteria, TDM, and MDP eliminated protection. Adjuvants without bacteria were not able to nonspecifically protect animals from infection, although TDM was able to significantly reduce the numbers of splenic Brucella. A positive correlation (P < 0.0001) between splenic infection and splenic weight was found.