Genetic resistance of eight native Egyptian chicken breeds having chicken B-cell marker 6 gene post-challenge with field strain of Marek's disease-induced tumor virus

摘要

Aim: The aim of this work was to detect chicken B-cell marker 6 (iChB6/i) gene in some native breeds in Egypt and find the relationship between founded genes in these different breeds to determine the resistance of native Egyptian breeds of chicken to Marek's disease (MD). Materials and Methods: A total of 14 different chicken breeds (30 each) including ten native breeds in addition to SPF Lohmann, High Line, Bovans, and Roodiland were used. Blood samples were collected for the detection of (iChB6,/i) by polymerase chain reaction (PCR) assay and sequenced to determine the presence or absence of iChB6/i gene. Experimental infection was done using local field isolated MD virus (MDV) of 11 (1 day old) unvaccinated chick breeds having no maternal antibodies against MDV. Ten breeds of them carry iChB6/i gene, eight breeds were native, and the rest two breeds were SPF Lohmann and High Line in addition to a group of iChB6/i gene-lacking breed (Bovans) were infected. Spleen samples were collected from all infected breeds at 20th, 25th, 30th, 35th, and 40th weeks post-infection and tested by PCR assay for the detection of MDV. Furthermore, at 40th week post-infection, tumorized spleen sample of Bovans breed was collected and prepared for examination by transmission electron microscope (TEM) to confirm the presence of MDV. Results: Our results revealed the positivity of 10 out of 14 breeds (Gimmizah , Sinai, Dandarawi, Fayoumi, Golden Montazah, Matrouh, Beheri, Dokki, SPF Lohmann, and High Line) to the presence of iChB6/i gene and resistance to MDV infection, while the Bovans, Mandarah , Inshas and Roodiland breeds lack the iChB6/i gene and are susceptible to MDV infection. The collected spleen samples revealed negative for the presence of challenged MDV by PCR in 10 breeds (Gimmizah, Sinai, Dandarawi, Fayoumi, Golden Montazah, Matrouh, Beheri, Dokki, SPF Lohmann, and High Line) and positive for Bovans breed. TEM is used to confirm MDV infection in Bovans group which demonstrated tumors. Conclusion: The study confirms the relationship between the presence of iChB6/i gene in our native breeds and the absence of tumors.