Risk Analysis Of CCR5 In The Development Of AGVHD And Study On The Mechanism Of CCR5 Antagonist In Preventing AGVHD

Allogeneic hematopoietic stem cell transplantation(allo-HSCT)is the hope to cure hematological malignancies.However,the complications after transplantation restrict the success of transplantation and lead to non-recurrent death.Acute graft-versus-host disease(aGVHD)is a specific complication associated with allo-HSCT.It can develop in about 40%-60% transplantation patients,and cause 10% patients' death.AGVHD is a kind of immune disease and is caused by donor T cells recognizing the recipients' antigen and attack their normal tissue.The first-line treatment of aGVHD is corticosteroids,however,as many as 60% of the patients in the clinic are unable to response or are resistant to the treatment.Therefore,prediction and prevention of aGVHD becomes one of the most important issues of allo-HSCT.The occurrence of aGVHD must have three requirements: the recipients are immunosuppressed and unable to launch an effective rejection of allograft;the presence of immune-competent donor cells in the graft;the donor and recipient have differences in histocompatibility antigen.Donor and recipient HLA mismatching is the most important risk factor of aGVHD.However,in recent years,it is reported that aGVHD can be regarded as a kind of polygenic disease.In addition to the HLA gene,the other immune related genes can also play a role in the occurrence of aGVHD.The target organs of a GVHD are skin,liver and gut.Due to the existence of specific target organs,more and more researchers begin to pay attention to the role of chemokines and their receptors in the development of aGVHD.CCR5,a member of chemokine receptor family,belongs to the 7 trans-membrane G protein coupled receptors,is widely expressed on membrane of T cells,NK cells,macrophages,dendritic cells and other immune cells.After binding the ligands,CCR5 mediates chemotaxis and migration of CCR5+ cells.CCR5?32 is the most common mutation in the human CCR5 gene caused by the deletion of 32 bp bases in the coding region,which leads to frameshift mutation.CCR5?32 encodes a truncated protein with four-trans-membrane structure,which makes the CCR5 receptor lose its function.CCR5?32 homozygotes do not have CCR5 expression on their cell surfaces and do not respond to ligands;CCR5?32 heterozygotes have low expression of CCR5 on their cell surfaces,and have decreased response to ligands.General health and immune status of CCR5?32 homozygotes are not affected.However,this mutation brings some benefits to their carriers.The homozygotes are naturally resistant to the HIV-1 virus;in solid organ transplantation,if the patient is a CCR5?32 mutation carrier,the graft of liver,kidney or heart transplantation can survive longer.CCR5 also plays an important role in the occurrence of aGVHD.In clinical observation,CCR5+ cells were spotted in the lesions of patients with aGVHD,and some studies have shown that increased CCR5 expression can be detected in the peripheral blood of patients a few days before the clinical aGVHD diagnosis.In order to investigate the role of CCR5 genotype in the pathogenesis of aGVHD,we analyzed the relationship between CCR5?32 mutation and the risk of grade 3-4 aGVHD with a meta-analysis.We searched extensively for relevant studies and make the inclusion and exclusion criteria according to the PICOS statement.The quality of included literatures was assessed according to the NOS scale,and finally,three retrospective studies were included in this meta-analysis.In the three studies,two were from Poland,and the other from the United States,all of the three studies focused on the relationship between CCR5 genotype and the development of GVHD after allo-HSCT.According to the results of heterogeneity tests,there was no significant heterogeneity between the studies,then a fixed effect model was used to analyze the pooled odd ratios(OR).Significant tests showed that if donors carried CCR5?32 then the pooled OR for the grade 3-4 aGVHD was 0.71,95% CI= [0.40-1.26],P= 0.24;the pooled OR for the patients carry the CCR5?32 was 0.79,with the 95% CI= [0.35-1.81],P= 0.58.According to the results of this study,there was no significant difference in the incidence of severe aGVHD if the donor or patient has CCR5?32 allele.Although the meta-analysis indicated a negative result,the efficacy of CCR5 in the development of aGVHD cannot be ignored.Many clinical studies showed that CCR5 specific antagonist maraviroc could prevent the occurrence of aGVHD and reduce its severity.When combined with the CCR5 receptor,maraviroc cause a conformational change of CCR5 receptor and inhibit the signal transduction mediated by its ligand.In 2012,Reshef et al reported for the first time that maraviroc could reduce the incidence and severity of a GVHD in the patients receiving a RIC allo-HSCT.The mechanism was reported as maraviroc block the CCR5 of donor T cells,thereby inhibiting the migration of donor CCR5+ T cells to the target organs of aGVHD.The pathogenesis of aGVHD can be divided into 3 stages,the conditioning cause tissue injury and then activation of antigen-presenting cells(APCs);APCs present host antigen to the donor cells and activate the donor cells;finally,effect cells and molecules attack the host tissue and cause damage.The most critical cell in the start-up phase is APC.Dendritic cells(DCs)are the most potent APCs in vivo,which play an important role in the initiation of aGVHD.Therefore,we suppose that whether maraviroc could affect the function of DCs by blocking the CCR5 receptor on the cell surface of DCs?In the second part of the study,we induced the monocyte to differentiate into DC cells and stimulated them to maturation with LPS.Before stimulated by LPS,the experimental group was gave different concentrations of maraviroc.The results showed that the expression of CD83 in maraviroc pretreated group was increased,suggesting that maraviroc could promote the maturation of DC cells.Besides,the secretion of IL-6 and TNF by mature DCs was inhibited by maraviroc.In the mixed lymphocyte reaction experiment,maraviroc pretreated DC cells were co-cultured with allogenic T cells,and the results showed that the experimental group DCs could promote the proliferation of allogenic T cells.Furthermore,we detected the secretion of cytokines in the supernatant of co-cultured cells.We found that the secretion of IL-10 increased in the experimental group.The results suggest that maraviroc pretreated DCs may induce the differentiation of CD4+T cells to cells which can secrete IL-10.Therefore,our results suggest that in vitro experiments,maraviroc could promote the maturation of monocyte derived DC cells,and inhibit the secretion of IL-6 and TNF by mature DCs.Moreover,maraviroc pretreated DCs could promote the proliferation of allogenic T cells and induce CD4+T cells differentiate to cells which can secrete IL-10.