Identification And Antigenic Comparison Of Different Immunogenic Strains Of Eimeria Maxima

Eimeria maxima is one of the most common species of coccidian occurring in flocks all over the world, and it is the most immunogenic of the seven species of Eimeria that infected the domestic chicken, and has also been demonstrated to be partial immunity to other species. As a result, E. maxima is almost included in all type of vaccines. Paradoxically, immunological differences within the strains of E. maxima are common, which led to a failed immunization. So the design and application of vaccine depend on the studies of strains isolated from the different regions, especially the analysis of antigenic patterns and its molecular background.Using single oocyst infected techniques, eleven pure species were isolated. According to the size, shape and color of oocyst, size and shape of sporocyst, shape index, specific site in the intestine, character of lesion, minimum sporulatic time, minimum prepatent period and isoenzymic profiles of LDH,GPI and G6PD, all eleven pure species are Eimeria maxima. With each strain, a single dose of 100 oocysts was sufficient not only to protect against the pathogeic and weight-loss effects of a heavy challenge (100 000 oocysts) but also to limit the oocyst production to a very low levels when challenged at a relatively light dose (10 000 oocysts). All eleven strains of E. maxima demonstrated a highly immunogenic. Every strain demonstrated a more or less extent of immunological cross-reactivity to heterologous strains among 11 strains of Eimeria maxima, A single infection with USA strain afforded 20.09 %~82.44 % protection against challenges with the ten Chinese strains, the reductions of oocyst output were over 75 % against the three strains and have a lowest protection against SH strain. A single infection with Chinese strain afforded 27.43 %~95.26 % protection against challenges with USA strain, the 75 % or more reductions of oocyst output was produced by the five strains, respectively and SH strain showed a lowest protectionagainst USA strain. The cross-protection among YZ, NT, FY, LY, GZ and SH strain was 1.72 %~96.67 %, SH strain demonstrated a most distinct immunogenicity from the other five strains.and the cross-protection of SH against YZ was even near to be zero.No detectable differences were observed in the profiles of SDS-PAGE and Westem-immunoblotting among two stage-antigens of YZ strain,SH strain and USA strain which their immunogenicity were apparently different from each other. There were at least 18 proteins in sporulated oocyst, including 7 predominant proteins with 100.2 KD,77.0 KD,63.2 KD,48.3 KD.41.2 KD,36.3 KD and 30.0 KD, but the major antigens recognized by Western-immunoblotting were 103.7 KD,.64.2 KD,.43.4 KD and 37.1 KD. There were at least 8 proteins in unsporulated oocyst, including 2 predominant proteins with 42.0 KD,.39.0 KD and 3 major proteins with 36.0 KD, 26.0 KD and 22.9 KD, the antigens recognized by Western-immunoblotting were 41.1 KD and 61.0 KD.