A novel approach to hematopoietic stem cell transplantation: The effect of CMV infection and HLA genotypes on chimerism status in Egyptian patients

Several studies have investigated the association between HLA alleles and cytomegalovirus (CMV) infection following hematopoietic stem cell transplantation (HSCT). It was found that many HLA alleles were associated with increased rate of CMV infection, while others had a protective effect against infection. However, to our knowledge no studies have investigated the effect of this relation on chimerism status post transplantation. Previous results concluded that CMV reactivation or infection increases conversion from mixed chimerism toward complete chimerism (CC) as a consequence of concomitant activation of immune system. Our aim is to study the association of CMV and certain HLA alleles and their effect on chimerism status post transplantation and identify other factors affecting chimerism status. 165 patients who underwent allogeneic HSCT for different hematological indications were studied. Both recipients (R) and donors (D) underwent serological testing for CMV-specific IgG and IgM, HLA typing, and chimerism analysis. CMV infection or reactivation was assessed in recipients through weekly monitoring of CMV DNA. Patients were followed up for 100 days where chimerism analysis was performed at 28, 60, 90, and 100 days post-transplantation. Eighty-five patients were positive for CMV by PCR post transplantation while eighty patients were CMV negative. Acute graft versus host disease (aGvHD) was significantly increased in CMV positive patients. Multivariate analysis (MVA) has indicated that HLA-A*2, HLA-B*14, HLA-B*41, HLA-DRB1*04 and HLA-DRB1*13, as well as a diagnosis of myelodysplastic syndrome and bone marrow aplasia, significantly increased the risk for CMV positivity post transplantation. HLA-DRB1*11 positivity was associated with a higher rate of aGvHD. CMV infection/reactivation as indicated by positive CMV PCR post-transplant was associated with a faster rate of conversion toward CC, and this effect was independent of the implemented conditioning regimen or the presence of aGvHD. Additionally, D+/R- transplant setting was significantly associated with early CC. On MVA, CMV reactivation was associated with acceleration of conversion toward CC, while HLA-A*33, HLA-DRB1*13, HLA-DRB1*15 and D−/R+ transplant setting were factors associated with delayed CC. In conclusion, CMV infection/reactivation and D+/R- transplant setting were associated with earlier conversion toward CC. Chronic GvHD and early chimerism were associated with better overall survival (OS), while advanced recipient age and HLA-DRB1*01 were associated with lower OS.