Donor CTLA-4 Genotype Modulates the Immune Response to Minor Histocompatibility Antigen Mismatches

LMP7 polymorphism may modify the presentation and clinical impact of minor histocompatibility antigens in matched related hematopoietic stem cell transplantation

Differential expression of minor histocompatibility antigens between the recipient and donor determines their disparity and can be modified by immunoproteasomes that regulate their processing and presentation. We examined the impact of HA-1 and HA-8 disparity, and immunoproteasome LMP7 polymorphism in 130 pairs. In multivariate analysis, HA-1 disparity showed a statistically significant association with an increased incidence of acute graft-versus-host disease (aGVHD) II-IV (p = 0.043, HR: 3.71, 95%CI = 1.04-13.26), while LMP7-Q/Q showed a trend toward increased incidence of aGVHD compared to LMP7-Q/K and K/K genotypes (p = 0.087, HR: 2.36, 95%CI = 0.88-6.31). All HA-1 and HA-8 disparate patients who developed aGVHD had the LMP7-Q/Q genotype. No significant association could be detected between HA-1, HA-8, or LMP7 and chronic GVHD, relapse-free survival (RFS), overall survival (OS), or transplant-related mortality (TRM). In conclusion, we suggested an association between the HA-1 disparity and the risk of developing aGVHD with a possible modifying effect of LMP7.

Rapid Multiplex Genotyping of 20 HLA-A*02:01 Restricted Minor Histocompatibility Antigens

A subset of MHC-associated self-peptides presented by the recipient's cells and immunologically foreign to the donor can induce an allogeneic immune response after hematopoietic stem cell transplantation (HSCT). These immunogenic peptides originate from the genomic polymorphisms and are known as minor histocompatibility antigens (MiHA). MiHA mismatches trigger the post-transplant immune response, which could manifest in both the deleterious “graft-vs.-host” disease and the beneficial “graft-vs.-leukemia” effect. Importantly, some MiHAs are considered to be promising targets for posttransplant T-cell immunotherapy of hematopoietic malignancies. This creates a demand for a robust and fast approach to genotyping MiHA-encoding polymorphisms. We report a multiplex real-time PCR method for the genotyping of 20 polymorphisms that are encoding HLA-A^*02:01-restricted MiHAs. This method uses allele-specific primers and gene-specific hydrolysis probes. In 1 h it allows for the detection of MiHA mismatches in a donor-recipient pair without the need for electrophoresis, sequencing, or other time-consuming techniques. We validated the method with Sanger and NGS sequencing and demonstrated good performance over a wide range of DNA concentrations. We propose our protocol as a fast and accurate method of identifying mismatched MiHAs. The information on the MiHA mismatches is useful for studying the allogeneic immune response following HSCT and for selecting the targets for post-transplant T-cell therapy.

Effect of CTLA4 gene polymorphism on relapse probability among patients with acute leukemias after allogenic hematopoietic stem cells transplantation

Background.Allogeneic hematopoietic stem cell transplantation (allo-HSCT) is being widely applied as a therapy for hematological malignancies. The long-term outcome of allo-HSCT depends directly on the ability of cytotoxic T-lymphocytes to recognize and eliminate the residual tumor. CTLA-4 is one of the regulatory proteins that provide control over the development of the immune response. Polymorphisms in the CTLA4 gene can affect its function and the efficiency of the antitumor response.The objective:to study the effect of non-synonymous single nucleotide polymorphism (nsSNP) c.49A>G in the donor CTLA4 gene on tumor control in the recipient of allogeneic hematopoietic stem cells (HSC).Materials and methods.Donors of HSC were genotyped for nsSNP c.49A>G in the CTLA4 gene by the real-time polymerase chain reaction using the allele-specific primers. Genotyping data was validated by Sanger’s sequencing of 22 randomly selected samples. The overall survival, the event-free survival and relapse probability were calculated using the Kaplan–Mayer method. A log-rank test was used to assess the statistical significance of group disparities. A p-value of 0.05 was considered as significant.Results.The frequencies of the CTLA4 gene c.49A>G polymorphism alleles in the observed population (102 healthy donors of HSC) correspond to the frequencies obtained by the “1000 genomes” project for the European population. The effect of the donor CTLA4 polymorphism on the tumor control was evaluated on the cohort of patients with acute leukemia after human leukocyte antigen (HLA) matched HSCT from an unrelated donor. It was shown, the three-year relapse-free survival was significantly lower for those patients who received grafts from a donor with the homozygous A/A state of nsSNP c.49A>G (p = 0.01), it was 12.7 % versus 62,8 % in group with c.49A>G G/G and A/G donor genotypes. The incidence of relapse was also significantly different for the group with A/A genotype and for the group with G/G or A/G genotypes of the nsSNP and equaled to 83.7 and 29.3 % respectively (p = 0.03).Conclusion.Patients with acute leukemia, who underwent allo-HSCT from unrelated completely HLA-matched donors with c.49A>G G/G or A/G genotypes have the significantly lower risk of relapse than patients whose donors had the A/A genotype. These results suggest practicability of the nsSNP genotyping for the optimal donor selection.

CTLA4 tagging polymorphisms and risk of colorectal cancer: a case-control study involving 2,306 subjects

Background

CTLA4 is a candidate gene which has been implicated in the development of colorectal cancer (CRC).

Patients and Methods

To determine the important role of CTLA-4 polymorphisms on risk of CRC, we genotyped four CTLA-4 tagging polymorphisms and calculated crude/adjusted ORs with their 95% CIs. We recruited 1,003 sporadic CRC cases and 1,303 controls.

Results

The findings suggested that CTLA-4 rs231775 G>A polymorphism increased the risk of CRC (homozygote model: adjusted OR=1.40, 95% CI=1.05-1.87, P=0.022; dominant model: adjusted OR=1.19, 95% CI=1.00-1.41, P=0.047; and recessive model: adjusted OR=1.38, 95% CI=1.05-1.82, P=0.021). In a stratified analysis by site of tumor, this association was also found in colon cancer. We also found that CTLA-4 rs231775 GA/AA genotypes might be associated with an increased risk of CRC in Zhenjiang cohort. In addition, we found the CTLA-4 rs16840252 C>T polymorphism was associated with the risk of colon cancer. Haplotype comparison analysis showed that CTLA-4 G_rs3087243C_rs16840252C_rs733618 A_rs231775, G_rs3087243C_rs16840252T_rs733618A_rs231775, and other haplotypes increased the risk of CRC (P<0.001, <0.001, and 0.002, respectively).

Conclusion

This study evidences an association of CTLA-4 tagging polymorphisms and haplotypes with CRC risk. Additional well-designed studies with large sample sizes are required to confirm our findings.