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

The aim of this work was to detect chicken B-cell marker 6 ( ) 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). 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 ( ) by polymerase chain reaction (PCR) assay and sequenced to determine the presence or absence of 6 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 gene, eight breeds were native, and the rest two breeds were SPF Lohmann and High Line in addition to a group of gene-lacking breed (Bovans) were infected. Spleen samples were collected from all infected breeds at 20 , 25 , 30 , 35 , and 40 weeks post-infection and tested by PCR assay for the detection of MDV. Furthermore, at 40 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. 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 gene and resistance to MDV infection, while the Bovans, Mandarah, Inshas and Roodiland breeds lack the 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. The study confirms the relationship between the presence of gene in our native breeds and the absence of tumors.