Measuring of BKV specific immune response by ELISPOT method in renal transplant patients

MEASURING OF BKV SPECIFIC IMMUNE RESPONSE BY ELISPOT METHOD IN RENAL TRANSPLANT PATIENTS BKV is one of the most frequent viral agents causing irreversible allograft failure in kidney translant patients. The seroprevalence of BKV reaches up to 90% in healthy population. After primary infection which is asymptomatic and occurs generally in early childhood, BKV remains latent in renal and urothelial cells. In 10-40% of immunocompetent individuals, reactivation and asymptomatic viruria can be seen. In renal transplant patients, BKV can cause self limited BKV reactivation or BK virus nephritis. After renal transplantation, BKV nephritis occurs in 1-10% of patients and leads to graft loss in 50-90% of them. In our study, after blood samples from 31 cases who had renal transplantation in Prof. Dr. Tuncer Karpuzoğlu Organ Nakli Enstitüsü were collected before transplantation and +1, +3, +6 months following transplantation, peripheral blood mononuclear cells (PBMC) were isolated and cryopreserved. In PBMC, BKV specific T cell frequency was analyzed bu using ELISPOT method. Plazma or urine viral loads of patients were measured by real time PCR. A patient who developed reactivation 7 months after transplantation was included in the study and BKV specific T cell responses were measured 4 times in total after reactivation. All the samples from patients included in the study had detectable levels of BKV specific T cell response. Mean spot numbers obtained from the patients prior to transplantation were not significantly different from the mean spot numbers of the control group. When BKV specific immune responses of patiens were compared, it was found that immune response was lowest in the first month in which immune suppression was highest. No difference was observed in the pretransplantation spot numbers between the the patients who developed reactivation and who did not have reactivation during the monitorization. Eight patients developed reactivation during the monitorization. In the two patients who had reactivation, with 2 and 3 BKV DNA results each, it was observed that BKV specific T cell immunity decreased during reactivation and increase in the immune response was correlated with the decrease or clearance of BKV viral load. In conclusion, it is thought that monitorization of BKV specific immune response by using ELISPOT method with plasma or urine BKV DNA viral loads in renal transplant patients can give us predictive information about prognosis of BKV reactivation, hence leading to prevention of BKVN development and evaluation of changes in immune responses during therapy. Key words: BKV, Renal Transplantation, Cellular Immunity, ELISPOT.