## Doctoral Dissertations

Spring 1988

Dissertation

#### Program or Major

Animal and Nutritional Sciences

#### Degree Name

Doctor of Philosophy

Richard G Strout

#### Abstract

Specific inbred lines of chickens expressing different major histocompatibility (B) complex haplotypes were studied for their immunogenetic response to the avian coccidium Eimeria tenella and genetically-engineered antigens cloned from this parasite species. The relative influence of the B-F vs. B-G chromosomal regions on innnate resistance and immunity to E. tenella was studied among six B-F/B-G recombinant hosts. F$\sb1$ chicks of similar genotypes, $B\sp{\rm R3}$ and $B\sp{\rm R4} (B\sp{\rm F2-G23}B\sp{17}$), gained significantly more weight than those with $B\sp{\rm R1}(B\sp{\rm F24-G23}B\sp{17})$ and $B\sp{\rm R5} (B\sp{\rm F21-G19}B\sp{17})$ following exposure to a single high dose of 25,000 oocysts, although no differences in cecal lesion scores were detected. Following exposure to a single low dose of 2500 oocysts, F$\sb1$ chicks $B\sp{\rm R3}$ and $B\sp{\rm R4}$ again gained significantly more weight and had significantly lower lesion scores compared to $B\sp{\rm R1}$ or $B\sp{\rm R5}$ F$\sb1$ chicks. Acquired immunity in F$\sb2$ homozygous recombinant chicks was studied using five consecutive daily exposures of 500 oocysts followed 21 days later by challenge with 10,000 oocysts. $B\sp{\rm R5}(B\sp{\rm F21-G19})$ and $B\sp{\rm R6}(B\sp{\rm F21-G23})$ homozygous chicks, both carrying the B-$F\sp{21}$ allele, showed significant protection in terms of reduced lesion scores.

The immunogenicity of recombinant E. tenella coccidial antigens 5401 and 3264 was studied in 6$\sb1\cdot B$ congenic chickens derived from $B\sp2B\sp2$ and $B\sp5B\sp5$ parents segregating for haplotypes $B\sp2$ and $B\sp5$. In separate experiments, antigens 5401 and 3264, both inoculated subcutaneously in Freund's complete adjuvant, elicited a protective response only in $B\sp5B\sp5$ chickens. $B\sp2B\sp2$ and $B\sp5B\sp5$ chickens also responded differently in serum IgG titer and in the magnitude of lymphocyte proliferation. Western blot analysis showed differential labeling of low molecular weight proteins. Antibodies raised against antigen 3264 strongly labeled only the anterior portion of the sporozoite stage of E. tenella. In contrast, these same antibodies strongly labeled only the posterior portion of second generation merozoites, while first generation merozoites were only slightly labeled, if at all. In addition, a single heavily labeled nodule, possibly an immune complex, was observed on the posterior surface of second generation merozoites.

Considered together, these findings demonstrate further that genetic responsiveness is linked to the major histocompatibility complex and has a profound influence on the host response to the parasite as well as the efficacy of recombinant protozoan vaccines.

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