Background: Mannose-binding lectin (MBL) is a protein critical in the activation of the lectin complement pathway. Patients with wild-type and variant mbl2 genotypes have high or low concentrations of MBL protein, which have been associated to increase susceptibility to transplant rejection or infection, respectively.
Objective: Our objective was to determine mbl2 genotype frequencies in a cohort of solid organ transplant recipients and its relationship with clinical outcomes.
Materials and Methods: A retrospective observational study in a single center. DNA samples were obtained at the time of inclusion in the waiting list for solid organ trasplantation as part of an extended immunological analysis to assess the pre-transplant immunocompetence status of the patients (109 heart transplantation, 3 liver transplantation). DNA was extracted from 1.5-mL ethylene diamine tetraacetic acid–treated whole blood samples. Genotyping of MBL2 was done by a polymerase chain reaction (PCR)/sequence-based typing technique. MBL2 encompassing a region from the promoter to the end of exon 1 was obtained by PCR amplification.
Results: Frequencies of the MBL genotype in our patients were similar to those of other Spanish populations used as a reference: Low-expressing genotype 16 (14%), intermediate 30 (27%), high 66 (59%). We have confirmed a correlation of genotype and phenotype as patients with the intermediate and deficient mbl2 genotypes disclosed significantly lower concentrations of MBL protein. Patients with low-intermediate expressing genotypes had a higher prevalence of viral infections (p=0.004).
Conclusion: Low-intermediate expressing genotype is a frequently expressed profile in the population that may predispose solid organ recipients to a greater susceptibility of viral infections. Under immunosuppressive clinical settings these genetic host factors might be associated with distinct clinical outcomes. The potential role of this genetic biomarker warrants further evaluation in prospective multicenter studies.