Hs. Lillehoj et Ep. Lillehoj, Avian coccidiosis. A review of acquired intestinal immunity and vaccination strategies, AVIAN DIS, 44(2), 2000, pp. 408-425
The gut-associated lymphoid tissues contain B and T lymphocytes responsible
for acquired immunity to avian coccidiosis. Intestinal B cells begin produ
cing parasite-specific antibodies shortly after infection although their ro
le in protecting against coccidiosis is debated. T-cell-mediated immunity,
predominantly by intestinal intraepithelial lymphocytes and lamina propria
lymphocytes, confers the main component of protective immunity to Eimeria.
Many of these cells display the CD8 and gamma delta T-cell receptor surface
antigens, phenotypic markers of cytotoxic T cells. Although their role in
eliminating Eimeria infection remains to be completely elucidated, T cells
have been implicated in parasite transport, and their activity is augmented
by interferon-gamma and interleukin-2. Because of the importance of cell-m
ediated immunity, coccidiosis vaccines must be capable of stimulating intes
tinal T cells. Orally delivered, live parasite vaccines, either unattenuate
d or attenuated, are powerful stimulators of intestinal cell-mediated immun
ity, but antigenic variability between Eimeria species present in the vacci
ne and in the field may restrict their commercial application. The newer ge
nerations of recombinant DNA and subunit protein vaccines, particularly whe
n used in conjunction with interferon-gamma and interleukin-2, have shown p
reliminary promise in controlling experimental infections but have yet to b
e commercially developed.