Published online Feb 14, 2018. doi: 10.3748/wjg.v24.i6.657
Peer-review started: December 21, 2017
First decision: December 27, 2017
Revised: January 3, 2018
Accepted: January 18, 2018
Article in press: January 18, 2018
Published online: February 14, 2018
Single nucleotide polymorphism (SNPs) and environmental triggers have been associated with a variety inflammatory autoimmune disorders including Crohn’s disease (CD). Specifically, SNPs in the negative regulatory immune genes Protein Tyrosine Phosphatase Non-receptor type 2 and 22 (PTPN2/22) have been associated with CD along with mycobacterial infections. Although both elements have been examined separately, correlation analysis have not been done to determine if SNPs in PTPN2/22 along with a Mycobacterium avium subspecies paratuberculosis (MAP) infections do cause a dysregulation in the immune system that could lead to CD symptoms.
Due to the flaws of current diagnosis and treatments of CD, new and better methods need to be determined. Investigating the pathogenesis of CD via SNPs analysis and MAP presence could lead to the possibility of individualized diagnosis/treatment for CD patients via genetic testing and antibiotic treatments. Our research could potentially propose newer routes of CD treatment for clinicians in the near future.
In this study, we examined the allele distribution in nine SNPs found in PTPN2/22 along with MAP presence in CD and healthy control subjects. Along with this, we determined gene expression of PTPN2/22 and correlated with both SNPs and MAP presence. Lastly, we examined T-cell proliferation of the subjects and correlated that with both SNPs and MAP presence as well. This study overall examined the effects of both SNPs in PTPN2/22 and MAP presence in CD subjects.
We obtained K2-EDTA coded blood tubes from both CD and healthy control subjects. Each subjects’ blood was examined for PTPN2/22 genotyping by TaqMan™ SNP genotyping, PTPN2/22 and IFN-γ gene expression by real-time PCR (RT-PCR), MAP presence by MAP IS900 nested PCR (nPCR), and T-cell proliferation by BrdU treatment.
We found in this study that the PTPN2:rs478582 SNP and the haplotype combination of PTPN2:rs478582 and PTPN22:rs2476601 SNPs were found significant in CD subjects compared to healthy control subjects. Gene expression of PTPN2/22 was also found to be decreased significantly in CD subjects as well. IFN-γ gene expression was found to be significantly higher in subjects with either PTPN2:rs478582 or PTPN22:rs2476601. MAP presence was found significantly in CD subjects compared to the healthy control subjects, were CD subjects with either PTPN2:rs478582 or PTPN22:rs2476601 had higher MAP presence than subjects without SNPs. Overall T-cell proliferation was higher in CD subjects with either SNPs and induced with MAP antigens than subjects who didn’t. These findings should provide more background to the pathogenesis of CD. Further studies into the gene expression of pro-inflammatory cytokines produced by T-cells with SNPs in PTPN2/22 after proliferation needs to be investigated.
This study was done in order to provide answers on the pathogenesis of CD. We have demonstrated that SNPs found in PTPN2/22 are found significantly in CD subjects and the SNPs have the following effects on the immune system: increases T-cell proliferation due to loss of negative regulation, increases pro-inflammatory cytokines such as IFN-γ, and increases susceptibility to mycobacterial infections. This is further evidence that both a genetic predisposition and an environmental trigger are needed to cause disease in inflammatory autoimmune disorders such as CD.
This study has provided us with new, possible targets that could be used in diagnosis methods and treatment for CD. With the data found in this study, the possibility of personalized treatment for CD could be possible with genetic testing for SNPs and antibiotic treatments for MAP. Further testing for other immune gene SNPs are needed in order to fully understand the genetic profile of CD patients. Additional research in MAP’s relationship with CD pathogenesis is also needed to fully understand the effect of MAP in CD patients.