en Host-pathogen interactions and susceptibility factors Host-pathogen interactions and susceptibility factors Original article Original article <strong>Introduction: </strong>Chronic Hepatitis B virus infection is a multifactorial disease with a variety of clinical outcomes. Since interferon-gamma (IFN-&gamma;) is a significant immune factor in antiviral defense, this case-control study aimed to investigate the potential relationship between single nucleotide polymorphism of rs2430561 and hepatitis B infection outcome in a population of Birjand city, eastern Iran. <strong>Methods: </strong>Blood samples were collected from 60 chronically HBV- infected patients and 60 healthy subjects with the history of HBV infection. Genomic DNA was extracted from whole blood by the salting-out method. The first intron of IFN-&gamma; with a length of 264 bp was amplified by Amplification Refractory Mutation System Polymerase Chain Reaction (ARMS-PCR) followed by sequencing. <strong>Results: </strong>Our results exhibited a statistically significant difference between patients and control individuals (<em>p</em>-value<0.001). The frequency of the allele A was 73.3% in HBV- infected patients, whereas in controls (individuals with a history of HBV infection) it was 46.7%. <strong>Conclusion:</strong> A statistically significant relationship was found between the IFN-&gamma; (+874T/A, rs2430561) single nucleotide polymorphism (SNP) and chronic HBV infec&shy;tion in the studied population. The obtained results showed that HBV infected individuals with T allele have less risk of progressing to chronic HBV infection. It also suggests that the homozygous carriers of the A allele are more vulnerable to chronic HBV infection. Chronic Hepatitis B, Single Nucleotide Polymorphism, Interferon-γ (+874T/A), Iran 43 47 http://jommid.pasteur.ac.ir/browse.php?a_code=A-10-156-1&slc_lang=en&sid=1 Mohammad Sadegh Naghizadeh msnaghizadeh92@gmail.com 0000-0002-7187-3736 No Student Research Committee, Birjand University of Medical Sciences, Birjand, Iran Mohsen Naseri naseri_m2003@yahoo.com 0000-0003-3100-6344 No Cellular and Molecular Research Center, Birjand University of Medical Sciences, Birjand, Iran Mohammad Fereyduni dr.m.fereidouni@gmail.com 0000-0002-2576-9452 No Cellular and Molecular Research Center, Birjand University of Medical Sciences, Birjand, Iran Masoud Ziaee dr.m.ziaee@gmail.com 0000-0003-0218-6833 No 3Infectious Diseases Research Center, Birjand University of Medical Sciences, Birjand, Iran Abdolghader Tane ghadertane94@gmail.com 0000-0003-0719-0591 No Student Research Committee, Birjand University of Medical Sciences, Birjand, Iran Hamidreza Safari hamidrezasafari941@gmail.com 0000-0002-0840-5833 No Student Research Committee, Birjand University of Medical Sciences, Birjand, Iran Neda Mahavar neda.mahavar91@gmail.com 0000-0001-6646-9512 No Student Research Committee, Birjand University of Medical Sciences, Birjand, Iran Roya Mahdavi royamahdavi1986@gmail.com 0000-0002-0666-070X No 4Department of Immunology, Birjand University of Medical Sciences, Birjand, Iran Gholamreza Anani Sarab ghansa@yahoo.com 0000-0003-3844-3643 Yes Cellular and Molecular Research Center, Birjand University of Medical Sciences, Birjand, Iran