| The Major Histocompatibility Complex of sheep, also called Ovine Lymphocyte Antigen (OLA), is part of chromosomal region consisting of a group of closely linked and highly polymorphic loci, in MHC-â…¡molecules, the MHC antigen encoded by DRB and DQB genes in plays an important role in the immune system, which is closely related to many animal disease resistance, susceptibility, immune response and production performance. In this research, polymorphism of DRB1/DQB1 exon 2 and its resistance to Cystic Echinococcosis (C.E) were analyzed in Dolang sheep and Chinese Merino (Xinjiang Army Wasteland Reclamation) sheep, on the base of polymorphic analysis, to explore the immune response of different haplotypes in Chinese Merino sheep during the process of Echinococcus granulosus infection, which would provide an important basis and theoretical support for resist-breeding of sheep in the future..1. In this experiment, PCR-SSCP method was used to analyze the genetic polymorphism of MHC-DRB1/DQB1 gene exon 2 in Dolang sheep. The results showed that exon 2 of DRB1 and DQB1 gene had a high degree of polymorphism. While a total of 50 genotypes were identified in DRB1 gene, which were controlled by 22 alleles; 42 genotypes were identified in DQB] which were controlled by 17 alleles.2. The frequency of allele and genotype of DRB1 in C.E-negative and-positive Dolang sheep were analyzed by T-test, to assess the relationship between different genotypes and C.E significance. Firstly, the allele frequencies of DRB1 were ananlyzed. Results were sumerized as follows:i) Sigficantly higher allele frequencies interms of B (P< 0.01), A and C (P< 0.05) occured in the negative sheep when compared with the positive sheep, implying that B, A and C ralated to hydatidosis resistance, ii) Sigficantly higher allele frequencies interms of G (P< 0.01), M and R (P< 0.05) occured in the positive sheep when compared with the negative sheep, implying that G, M and R ralated to hydatidosis susceptibility. In addition, the genotypes frequencies of DRB1 were also tested. Results were sumerized as follows:i) Genotype BB (P< 0.05) occured more often in the negative sheep when compared with the positive sheep, implying that genotype BB was related to hydatidosis resistance, ii) Genotypes GG (P< 0.01) and MM (P < 0.05) occured more often in the positive sheep when compared with the negative sheep, implying that genotypes GG and MM were related to hydatidosis susceptibility.3. The allele frequemcy of DQB1 were analyzed which occurred in positive and negative echinococcosis of Dolang sheep, results showed that the allele frequency of H (P< 0.05) and L (P< 0.01) in the negative sheep were significantly higher than the positive sheep, to consider that the H and L is the resistance allele of hydatids disease, while the frequency of J and M (P< 0.01) in the positive sheep was significantly higher than negative sheep, that J and M are the susceptible to hydatid disease. To further analyze the genotype frequency of negative and positive hydatid disease of sheep, the results showed that the genotype frequency of LL and DF (P< 0.05) in the negative sheep were significantly higher than the positive sheep, that LL and DF genotype are associated echinococcosis resistance. The genotype frequency of MM(P< 0.01)in the positive sheep was significantly higher than negative sheep, that MM is hydatid disease susceptibility genotype.4. In order to select the resistant genic mark, the relationship between different haplotypes and resistance or susceptibility to C.E in Dolang Sheep was analyzed.The results showed that individuals with the genic haplotype DRB1-BB/DQB1-DF (P< 0.01) and DRB1-JJ/DQB1-DH (P < 0.05) were relatively resistant to Echinococcus granulosus (E.g), while individuals with the haplotypes DRB1-GGIDQB1-MM (P<0.01) and DRB1-MM/DQB1-JJ (P<0.05) were more susceptible to E.g.5. The polymorphism of MHC-DRB1/IDQB1 gene exon 2 in Chinese Merino sheep were analyzed by PCR-SSCP method, the results showed that polymorphisms in exon 2 of DRB1/IDQB1 gene are abundant there, emergence 53 genotypes in DRB1 gene, which controlled by 22 alleles; 47 genotypes in DQB1 gene, which controlled by 17 alleles.6. The allele and genotype frequency of DRB1 gene exon 2 in C.E positive and negative in Chinese Merino sheep was analyzed by T-test, the results showed that the allele K (P< 0.05),Q and T (P< 0.01) are related with resistance of C.E, while A and L (P< 0.01) are related with susceptivity of C.E. We further to analyze the genotype frequency found that KK and TT (P< 0.05) are the resistant to C.E, the genotype AA and LL (P< 0.01). AL (P< 0.05) are the susceptible to C.E.7. The alleles of DQB1 were ananlyzed which occurred in positive and negative C.E in Chinese Merino sheep, results showed that the allele frequency of D and E (P< 0.01) in the negative sheep were significantly higher than the positive sheep, to consider that the D and E are the resistance allele to C.E, while the frequency of C and K (P< 0.01) in the positive sheep were significantly higher than negative sheep, that C and K are the susceptible to C.E. To further analyze the genotype frequency of negative and positive C.E of sheep, the results showed that the genotype frequency of DD and EG (P< 0.01) in the negative sheep were significantly higher than the positive sheep, that DD and EG genotype are associated with C.E resistance. The genotype frequency of CC and KK,CK (P< 0.01) in the positive sheep were significantly higher than negative sheep, that CC, KK and CK are associated with susceptivity to C.E.8. In order to efficiently analyze the the polymorphism of DRB1/DQB1 gene and C.E, the relationship between different haplotypes and resistance or susceptibility to C.E was researched in Chinese Merino Sheep. The result found that individuals with the genie haplotype DRB1-TT/DQB1-EE (P< 0.05) are resist to C.E, while DRB1-LL/DQB1-CK and DRB1-AA/DQB1-CC (P<0.01) are susceptible to C.E. 9. Based on the polymorphism analysis of DRB1 and DQB1 gene exon 2 in Chinese Merino sheep and Dolang sheep,16 Chinese Merino sheep with different haplotypes were artificially infected with Echinococcus granulosus (E.g) at the identical raising condition,8 sheep with resistant haplotype were selected as the test group, while 8 individuals with nonresistant haplotype were selected as the control group. The CD4+T, CD8+T, B lymphocyte subpopulations of peripheral blood were analyzed by flow cytometry at day (-7),0,7,21,30 and 60 after the artificial infection, meanwhile, the content of IgG, lgM, IgE, IFN-y of the blood serum and granulocyte quantity in the blood were also tested. The results showed that the incidence of Cystic Echinococcosis in the test group was significantly lower than that of the control group (P< 0.05), there was no significant difference of CD4+T cells percentage between the two groups (P>0.05). CD8+T cells of the test group were significantly higher than that of the control group (P< 0.05) at 7th day after infection., IgG level of the two groups at 7th day after infection were significantly higher than that at the (-7)th day (P<0.05). IgM and IFN-y of the test group were significantly higher than that of the control group (P< 0.05) at 30th day after infection. Leukocytes and lymphocytes of the test group were significantly more than that of the control group (P< 0.05) at 7th,21st day after infection. Neutrophils and albumin of the test group were obviously lower than the control group (P<0.01) at 21st day. (Conclusion) Significantly higher resistance to Echinococcus granulosus occurred in the resistant haplotype sheep, when compared with the nonresistant haplotype individuals. CD8+T cells, IgM, IFN-y, leukocytes and lymphocytes in the resistant haplotype sheep were significantly higher than those of nonresistant haplotype individuals during the different period after infection.10. DRB1 gene expression of the test group at 60 d after infection was significantly higher than at the 0 d (P< 0.05) and 30 d (P< 0.05); the expression of the control group at 21 d was significantly higher than at the 0 d (P< 0.01) and 7d (P< 0.05), and the expression at 30 d significantly lower at 21 d (P< 0.01).To analyze the DQB1 expression, the result showed that the expression of the resistant sheep at 21 d (P< 0.01) and 60 d (P< 0.05) were significantly higher than at the 0 d, the expression at the 30 d was significantly lower than at the 21 d (P< 0.05). The change tendency of DQB1 expression in the control group was similar to the test group, the expression at 21 d was significantly higher than at the 0 d (P< 0.05), and the expression at the 30 d was significantly lower than at the 21 d (P< 0.05). (Conclusion) The expression of DRB1 and DQB1 gene between the resistant and nonresistant sheep was no significant deviation.
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