Stimulation of antibacterial vaccination in mice by polyadenylic acid: polyuridylic acid complex.

The effect of polyadenylic acid:polyuridylic acid complex (poly A:U) on immunization was investigated in mice vaccinated by killed Brucella melitensis cells suspended in incomplete adjuvant or in saline. Addition of 300 mug of poly A:U to vaccines rendered 3 x 10(8)B. melitensis cells in saline as immunogenic as 3 x 10(11) cells in oil adjuvant against a severe B. abortus challenge. In the mouse and Brucella system, poly A:U exerts an adjuvant effect on immunity but does not stimulate production of circulating antibodies that could be demonstrated at the time of autopsy.