Association of interferon gamma gene polymorphism and susceptibility to hepatitis C virus infection in Egyptian patients: A multicenter, family-based study

Abstract

Background and aim: Polymorphisms in some genes may influence the persistence of hepatitis C virus (HCV) infection, clinical outcome, HCV replication, and liver damage. This study was conducted to investigate the role of the interferon gamma (IFN-γ) gene at (+874 T/A, -764 G/C, -179 C/A) single-nucleotide polymorphisms (SNPs) and its receptor (IFN-γR2) at (rs 2786067 A/C) SNP in the susceptibility of Egyptian families to HCV infection with high-resolution techniques.

Methods: In total, 517 Egyptian families, with 2246 subjects, were recruited to this study from the Upper and Lower Egypt governorates and were classified into three groups: 1034 patients with chronic hepatitis C virus, 108 subjects with spontaneous virus clearance (SVC), and 1104 subjects as a healthy control group. All subjects were genotyped for (+874 T/A, rs2430561, -764 G/C, rs2069707, -179 C/A, rs2069709, and rs 27860067, A/C) SNPs of the IFN-γ gene using the allelic discrimination real-time polymerase chain reaction technique and were confirmed using sequence-based typing.

Results: The carriage of T allele of (+874) IFN-γ is a risky allele and was significantly higher in chronic hepatitis C more than other two groups (odds ratio [OR]: 2.6646, P < 0.0002). On the other hand, the C allele of (-764, rs2069707) is a protective allele and was higher in SVC than the other two groups (OR: 0.2709, P < 0.0001). However, both (-179 C/A, rs 2069709) and (rs 27860067, A/C) SNPs are not polymorphic enough to be studied in the Egyptian population.

Conclusions: HCV infection is associated with the T allele of (+874 rs2430561), while SVC of HCV is associated with the C allele of (-764, rs2069707) of the IFN-γ gene.

Keywords: gene polymorphism; hepatitis C virus susceptibility; interferon gamma; intrafamilial; viral clearance.

Figure 1

+874 IFN‐γ amplification‐refractory mutation system‐polymerase chain reaction (ARMS‐PCR) gel. Part I: Ethidium bromide‐stained 2% agarose gel for single‐nucleotide polymorphism (SNP) IFN‐γ (+874 A/T). PCR‐ARMS product: (A) First well is a DNA marker of 100 bp. (B) Second and third wells are blank samples for forward 01 and forward 02 that has deionized water instead of the sample template. (C) Sample (1) has only two DNA bands for one well, one of them at 426 bp of human growth hormone (HGH) internal control and the other band at 261 bp of +874 A allele; however, the well of the T allele did not work, so these samples are negatives for the +874 T allele. (D) Sample (2) has one DNA band of each well at 426 bp of (HGH) internal control and only one band at 261 bp of +874 A allele, with the absence of T allele band, so these samples are negatives for the +874 T allele. (E) Samples (3,7,8) have two bands for each well, one of which is of 261 bp, indicating the presence of the +874 A allele or +874 T allele, so these samples are positives for A and T alleles. The second band is the internal control (HGH), which is of 426 bp. (F) Samples (4,5,6) have one DNA band of each well at 426 bp of (HGH) internal control and only one band at 261 bp of +874 T allele with the absence of A allele band, so these samples are negatives for the +874 A allele. Part II: IFN‐γ (+874 A/T) SNP using sequence‐based typing technique. Lane (a): Representative sequence chromatographs of IFN‐γ (+874T) intron 1 of homozygote sample TT. Lane (b): Representative sequence chromatographs of IFN‐γ (+874A) intron 1 of homozygote sample AA. Lane (c): Representative sequence chromatographs of IFN‐γ (+874T/A) intron 1 of heterozygote sample TA. IFN‐γ, interferon gamma.

Figure 2

Real‐time polymerase chain reaction charts for different genotypes of (−764 G/C) single nucleotide polymorphism of the interferon gamma gene. VIC, ROX and FAM are immunochemisry dyes. (a) Homozygote (GG): , FAM; , ROX; , VIC. (b) Homozygote (CC): , FAM; , ROX; , VIC. (c) Heterozygote (GC): , FAM; , ROX; , VIC.