Immune response to Babesia bigemina infection in pregnant cows.

The objective of this study was to characterize the immune response of Babesia bigemina-infected cows during the second trimester of pregnancy. Twelve animals were divided into four groups (I, II, III, IV); groups I and II were pregnant cows, groups III and IV were non-pregnant cows. Groups I and III were infected with a virulent strain of Babesia bigemina, the doses utilized was 1 x 10(7) infected red blood cells IM. Groups II and IV were noninfected control groups. All the infected animals were severely affected; at days 5-7 post-inoculation (DPI) they showed clinical signs: fever (40-41.5 degrees C), packed cell volume reduction, and parasitemia, and specific treatment was required. The immune response was monitored daily from 0-11 DPI. As shown by flow cytometry analysis, in infected animals the distribution in peripheral blood of the T-cells subpopulations (CD4+, CD8+, gammadelta T-cells) was not affected when compared to the control groups. By ELISA, IFN-gamma production showed a trend to increase in plasma between 6-10 DPI; noninfected cows showed the lowest optical density values. By RT-PCR, a Th1 predominant response was observed, TNFalpha, INF-gamma and iNOs were detected. In contrast IL-4 and IL-10 were weak or undetected. The results of this trial will be discussed.