Vaccination against Boophilus microplus: localization of antigens on tick gut cells and their interaction with the host immune system.

Cattle have been vaccinated against Boophilus microplus with antigens derived from partially fed female ticks. The immune response of the host lyses the gut cells of adult ticks, causing a reduction in the number, weight and reproductive capacity of engorging ticks. This response is different from the immunity that cattle acquire after repeated tick infestation. Evidence is presented that the antigens used in vaccination are located on the plasma membrane of the gut cells and it is unlikely that these antigens are secreted into the host during feeding. Vaccination using such 'concealed' antigens may not encounter the mechanisms of immune evasion that parasites usually demonstrate. In-vitro assays suggest that vaccination immunity is not dependent on the need to stimulate cell-mediated responses. Immunoglobulin G alone, or with the aid of complement, is enough to damage tick gut. The normal function of the one protein antigen isolated so far is unknown but we speculate that it serves some vital function on the cell plasma membrane.