Chicken major histocompatibility complex polymorphism and its association with production traits.

Major histocompatibility complex (MHC) is the best characterized genetic region controlling disease resistance and immune responses in chicken. MHC genes are also involved in various non-immune functions such as productive traits and reproductive success. The genetic diversity of MHC in an Iranian indigenous chicken (Khorasan) was studied, and association of the MHC alleles with production traits was determined. The MHC polymorphism was ascertained by genotyping the LEI0258 microsatellite locus by PCR-based fragment analysis. LEI0258 microsatellite marker is a genetic indicator for MHC, which is located on microchromosome 16 and strongly associated with serologically defined MHC haplotypes. A total of 25 different LEI0258 alleles (185-493 bp) and 76 genotypes were identified in 313 chickens. An allele of 361 bp had the highest frequency (26.44%), and alleles of 207 and 262 bp had the lowest (0.16%). High level of heterozygosity (87%) and good genotype frequency fit to the Hardy-Weinberg equilibrium was observed in this population (P = 0.238). The association study also revealed a significant influence of MHC alleles on body weight, egg weight, egg laying intensity, and weight of sexual maturity in Khorasan population (P < 0.05). The information obtained from this study indicates a high MHC genetic diversity and the association of MHC alleles with important production traits in Khorasan chicken. These data would be applicable in designing breeding and genetic resource conservation for indigenous chicken populations.

The influence of genetic background versus commercial breeding programs on chicken immunocompetence.

Immunocompetence of livestock plays an important role in farm profitability because it directly affects health maintenance. Genetics significantly influences the immune system, and the genotypic structure of modern fast-growing chickens has been changed, particularly after decades of breeding for higher production. Therefore, this study was designed to help determine if intensive breeding programs have adversely affected immunocompetence or whether the immune response profiles are controlled to greater extent by genetic background. Thus, 3 indigenous chicken populations from different genetic backgrounds and 2 globally available modern broiler strains, Ross 308 and Cobb 500, were evaluated for various aspects of immune response. These included antibody responses against sheep red blood cells and Brucella abortus antigen, as well as some aspects of cell-mediated immunocompetence by toe web swelling test and in vitro blood mononuclear cell proliferation. Significant differences (P < 0.05) in antibody responses to both antigens and cellular proliferation were observed among populations but not consistently between modern commercial strains versus the indigenous populations. In fact, the immune response profiles of Cobb 500 were similar to the indigenous populations, but varied compared with the other commercial strain. In addition, considerable variation was recorded between indigenous populations for all responses measured in this study. The results of this study suggest that the variation observed in immune responses between these strains of chickens is most likely due to differences in the genetic background between each strain of chicken rather than by commercial selection programs for high production.

Whole egg and alevin changes of cortisol and interrenal tissue differences in rainbow trout Oncorhynchus mykiss exposed to different stocking densities during early development.

Cortisol level changes in response to stocking density in the early stages of rainbow trout were measured. Eggs were exposed to low, normal, and high (2.55, 5.10 and 7.65 eggs cm(-2)) densities during the incubation period. Cortisol of maternal origin was found in pre-fertilized eggs (5.09 ± 0.12 ng g(-1)) of rainbow trout. In newly fertilized eggs, resting Cortisol levels (3.68 ± 0.14 ng g(-1)) decreased to 0.58 ± 0.08, 0.60 ± 0.12, and 0.57 ± 0.16 ng g(-1) at low, normal and high densities by day 10 (organo-genesis), respectively. Resting Cortisol levels remained constant until the eyed stage (day 18). Then, Cortisol showed an increase at hatching to 1.16 ± 0.11, 1.20 ± 0.12, and 1.21 ± 0.14 ng g(-1) at low, normal, and high densities, respectively. The pattern of change in Cortisol level was similar in all three densities. Interrenal cells were observed in 1-day old alevins at all three densities. Hematopoietic tissue, renal tubules and nucleated red blood cells were clarified through the head part of kidney. Higher numbers and larger interrenal cells were observed at high-density groups. Chronic density stress test conducted on embryonic stages of rainbow trout revealed no differences in Cortisol levels, but had an effect on the abundance and size of the interrenal cells. Densities were equaled after hatching (200 alevins per replicate) to investigate the different densities of eggs on stress indices in rainbow trout alevins. An acute stress (air exposure of eggs for five minutes) was applied in three treatments two weeks after hatching, and samples were taken at 0, 1, 3, 6, and 24 hps (hours post stress). Cortisol content increased under low density in 1 hps and reached from 5.21 ± 0.13 ng g(-1) to 6.01 ± 0.18 ng g(-1) (P < 0.05). Cortisol levels increased under normal density in 1 hps from 6.03 ± 0.28 ng g(-1) to 10.84 ± 0.18 ng g(-1) (P < 0.05). In high density also Cortisol increased from 6.83 ± 0.23 ng g(-1) to 8.86 ± 0.26 ng g(-1) (P < 0.05). At 3 hps;, Cortisol level was returned to basal level under low (P > 0.05) and normal (P > 0.05) densities, but significantly decreased (P < 0.05) under high density. Results revealed that the Cortisol biosynthesis was observed in rainbow trout between eyeing to the hatching stage. An increase in the density of eggs until 7.65 egg cm(-2) impaired Cortisol secretion and feedback system in alevins. However, more studies are needed to identify the exact time for Cortisol synthesis ability from eyeing to hatching in this species.

LEI0258 microsatellite variability in Khorasan, Marandi, and Arian chickens.

Microsatellite LEI0258 is a genetic marker for chicken MHC haplotypes and can be used as an indicator of the influence of population genetics on immune responses. LEI0258 microsatellite variability in three Iranian indigenous chicken populations (Khorasan, Marandi, and Arian) was investigated. In total, 142 Khorasan, 42 Marandi, and 58 Arian chickens were examined. Collectively, 25 different alleles and 79 genotypes could be found. The observed levels of heterozygosity were 81% in Khorasan and Marandi and 34% in Arian chickens. Our results indicate that LEI0258 diversity in Marandi chickens is higher than in the other populations. Allelic diversity in Iranian chickens is relatively higher than in the local chicken breeds reported for Brazil and Vietnam.

Prion protein coding gene (PRNP) variability in sheep from Turkey and Iran.

This study was designed to analyze variation of ovine prion protein in sheep breeds in Iran and Turkey. A competitive approach was used to analyze the open reading frame (ORF) of the ovine PRNP gene using a total of 186 samples from five indigenous sheep breeds. The ARQ allele was found to be the predominant allele in five breeds. The ARR allele was not observed in homozygous combination among the 11 genotypes found in the study. In addition, six other polymorphisms were indicated. These findings have great significance for estimating genetic variability in the PRNP gene with regard to Iranian and Turkish sheep. Since no information on the susceptibility of some genotypes identified in this study has been reported, no grouping was made on the basis of susceptibility.

Association between DLA-DRB1.2 allelic diversity and development of mammary gland tumors in dogs.

BACKGROUND: The major histocompatibility complex (MHC) is the best-characterized genetic region related to resistance/susceptibility to a wide range of infectious and immune-mediated diseases. Evidences suggest that MHC class II genes may play an important role in developing different types of tumors including breast cancer. Canine mammary gland tumors (CMTs) are the most common neoplasms in female dogs. In the current study, the association of canine MHC class II DLA-DRB1.2 genotypes with development of mammary gland tumor profiles in dogs was investigated. DLA-DRB1.2 allelic diversity was determined in 40 dogs (18 CMT cases and 22 controls) using HRM technique and DNA sequencing. Association of the DLA-DRB1.2 genotypes with CMT profiles was expressed as odds ratio (OR). RESULTS: Based on the histopathological typing of tumors, CMT cases were categorized into 4 groups: simple carcinoma, complex carcinoma, carcinoma arising in a benign tumor and special types of carcinoma. A total of eight HRM profiles (A to H) were identified in dogs sampled. The association study revealed a significant correlation between DLA-DRB1.2 genotypes with different CMT profiles. The E genotype was significantly associated with increased risk of carcinoma arising in a benign tumor, and the B genotype represented a positive correlation with complex carcinoma. Significant association was also observed between the heterozygosity of DLA-DRB1.2 genotypes and decreased risk of developing tumor in dogs. CONCLUSIONS: These results provide additional support for the association between DLA-DRB1 genes and development of mammary gland tumors in dogs and could potentially be used for early diagnosis of neoplasia and identifying susceptible dogs.

Immune responses to oral and IM administration of M2e-Hsp70 construct.

The eukaryotic expression plasmid of M2e-Hsp70 is a candidate M2e-based DNA vaccine. In order to evaluate the immunization potential of this construct, Specific Pathogen Free chickens were immunized either intramuscularly or orally. Mutant Salmonella typhimurium was used as carrier for oral delivery of the M2e-Hsp70 construct. M2e-specific humoral and cellular responses were tested by ELISA and Lymphocyte Proliferation Assay, respectively. Our results indicate that both humoral and cellular immune responses are conferred against M2e-Hsp70 plasmid in either of the intramuscular or oral routes of administration; however, these responses are significantly higher in intramuscular injection in contrast to oral administration. When it comes to mass vaccination of commercial chicken flocks oral administration is preferred due to the ease of application as well as its capability of eliciting mucosal, humoral and cellular immune responses; so measurements should be taken to improve the immunization potency of our orally delivered DNA vaccine.

Allelic polymorphism in the second exon of Ovar-DRB1 in fat-tailed sheep.

Ovar-DRB1 is one of the most important response genes in the major histocompatibility complex (MHC) class II region of sheep. Gene polymorphism in the second exon of Ovar-DRB1 in three different Iranian fat-tailed sheep breeds (Lori-Bakhtiari, Shaul and Zandi) was analyzed by either restriction fragment length polymorphisms (RFLP) or direct sequencing. A total of 92 Lori-Bakhtiari, 40 Shaul, and 47 Zandi sheep were examined. PCR-RFLP identified 17 genotypes in Lori-Bakhtiari sheep, 12 in Shaul sheep and 11 in Zandi sheep. Collectively, 24 different genotypes could be found for Iranian fat-tailed sheep. Using direct sequencing, seven new sequences in exon 2 of the Ovar-DRB1 gene were identified. Generalized linear modeling with a multinomial error structure showed that the sheep populations had significantly different allele frequencies.

Clonal diversity of Salmonella enterica serotype Typhi isolated from patients with typhoid fever in Tehran.

In this study, antimicrobial susceptibility test and genetic typing were used to characterize 15 Salmonella enterica serotype Typhi (S. Typhi) isolates recovered from sporadic cases of typhoid fever in Tehran, Iran during 2004. Antimicrobial susceptibility test showed that all isolates were susceptible to 20 antimicrobials examined in this study. Analysis of insertion elements showed that 2 IS200 types with 10 and 11 copies were present. 11 of the 15 isolates were found to possess 10 IS200 elements residing on fragments from 23 to 2.3 kb. Comparison of the RiboPrinter (automated ribotyping) patterns of S. Typhi showed that 60% (9/15) of the isolates belonged to a single ribotype. PCR based random amplified polymorphic DNA analysis (RAPD) and enterobacterial repetitive intergenic consensus (ERIC) and pulsed-field gel electrophresis (PFGE) were also performed. ERIC and RAPD-PCR method showed 2 and 3 genotyping patterns amongst the isolates, respectively. The PFGE typing was carried out by using XbaI restriction enzyme, and 7 restriction patterns were observed. Overall, the molecular typing methods applied in this study showed that the isolated S. Typhi populations were highly polyclonal as shown by PFGE.