Inhibitory effect of monoclonal antibodies on the growth of Babesia caballi

Monoclonal antibodies (mAbs) were produced against Babesia caballi (USDA st rain) to define a species-specific antigen for use in diagnosis and vaccine development. Eight positive clones of B. caballi mAbs determined by indire ct immunofluorescent antibody test were selected for purification and furth er characterisation. Confocal laser microscopy showed that the antigens rec ognised by the mAbs were located on the surface/cytoplasm, central part, an d/or anterior end of B. caballi parasites, with five different reactive pat terns. These mAbs seemed to be species-specific, since they did not cross-r eact with Babesia equi-infected erythrocytes or uninfected erythrocytes. In Western blotting analysis, 18, 20, 34, 36, 48, and 155 kDa proteins of B. caballi merozoites were recognised by six different mAbs. When added to in vitro cultures, four of the mAbs significantly inhibited the in vitro growt h of B. caballi parasites. These results provide a rationale for evaluating antigens for the development of diagnostic methods or vaccines. (C) 1999 A ustralian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved.