الفهرس 
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Abstract
Buffalo is considered as one of the main two sources of good quality meat and milk in Egypt. One of the most economically important viral pathogens of animals is FMD virus, which is highly contagious among cloven hoofed mammals including buffalo. The BoLA-DRB3 functional genes play a significant role in genetic control of immune responses. The present study aimed to investigate the genetic polymorphism of BoLA-DRB3 gene in some Egyptian buffaloes with the assessment of its association with FMD resistance, in addition to investigate the contribution of Foot and Mouth Disease Virus (FMDV) and characterization of the circulating strains between the studied population during 2016. Testing of 40 collected samples of Oropharyngeal, oral epithelial tissue and/or vesicular fluids by real time Reverse transcriptase polymerase chain reaction (rRT-PCR) revealed 33 out of 40 FMDV positive samples. Typing of the highly viral loaded FMDV positive samples by conventional reverse transcriptase polymerase chain reaction (RT-PCR) revealed that all tested samples belonged to serotype O of FMDV. Sequencing and phylogenetic analysis of 5 representative samples clustered the detected viruses with O topotype East Africa-3 (EA-3) viruses. The 302-bp amplified fragments from BoLA-DRB3 exon 2 were digested with HaeIII endonuclease and the results revealed presence of five BoLA-DRB3 genotypes, among them the genotype AA might be associated with FMD-resistance (P<0.05) where its frequency was 88.89% in resistant and 11.1% in susceptible groups. On the other hand, genotype AC could be correlated with susceptibility to FMD in the studied Egyptian buffaloes where it was absent in resistant group. In conclusion, findings of this study suggested that some Egyptian water buffalo might have the ability to relatively resist FMD by mutation which results in changes of the translated amino acids and then the protein structure to perform the regulation of different signaling pathways used by the cell in the long process of choice evolution.