Cytomegalovirus (CMV) infection remains a major source of morbidity and mortality in solid organ transplant recipients. Killer immunoglobulin-like receptors (KIR) are genetically polymorphic natural killer (NK) cell receptors important in antiviral responses. A retrospective, single-center cohort study was performed to study the interaction of KIR genotype and primary control of CMV infection after transplantation. Time to first CMV viremia was determined for a cohort of 531 CMV serology donor positive/recipient negative solid organ transplant recipients. Of the KIR genes, KIR2DL3 and KIR2DS2 were most strongly associated with time to CMV viremia in random survival forest analysis. As KIR2DL3 and KIR2DS2 both interact with HLA-C1, these interactions were evaluated. Seventysix recipients were found to be positive for both KIR2DL3 and KIR2DS2 and expressed only HLA-C1 antigens in both recipient and donor. These patients had a substantially reduced hazard of CMV viremia in the first year after solid organ transplantation (hazard ratio 0.44, 95% CI 0.27-0.72, p ¼ 0.0012). In KIR2DL3þ/ KIR2DS2þ/HLA-C1/1 recipients who received an organ from a non-C1/1 donor, this protective effect was not observed. These results improve our understanding of human NK cell function in primary CMV infection after transplant.

Major histocompatibility complex (MHC) class I-related chain A gene (MICA) sequence-based genotyping (SBT) was attempted on a peripheral blood sample collected from a patient evaluated for hematopoietic stem cell retransplant. The electropherogram pattern of MICA SBT indicated the possibility of carrying more than two MICA alleles. Subsequent cloning and sequencing of the polymerase chain reaction products revealed the presence of three distinct MICA alleles: MICA*008:01/:04 (A5.1), MICA*007:01(A4), and MICA*002:01 (A9) in the genotype of this patient. The origin of the third extra MICA allele could not be determined and would require MICA genotyping information from other family members, which is unavailable.

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