Direct visualization and quantitation of cytomegalovirus-specific CD8+cytotoxic T-lymphocytes in liver transplant patients

Background, CMV infection remains a significant clinical problem in the con text of LT, Changes in the magnitude of the CM-specific CTL response after LT have not previously been assessed but may be important in determining th e outcome of CMV infection, Method. We used a fluorescent HLA-B*0702-CMV peptide tetrameric complex to directly visualize and quantitate CMV-specific CD8+ CTL both in immunosuppr essed patients after LT and in immunocompetent controls. Results. CMV-specific CD8+ CTL, at a frequency ranging from 0.1 to 5.8% of CD8+, were detected in the peripheral blood of 22 of 25 B*0702, CMV immunog lobulin G seropositive individuals, with no difference observed between imm unocompetent controls and patients >3 years after LT, In CMV seropositive L T recipients who did not have symptomatic CMV infection during the first 3 months after LT, CMV-specific CD8+ CTL magnitude initially decreased, then increased up to 5 times higher than pre-LT levels within 3 months, Two CMV seronegative recipients of seropositive donors had symptomatic CMV infectio n in association with high viral load. In both patients, no CD8+ CTL respon se was detected before the onset of symptoms, and a I eduction in viral loa d was observed during antiviral therapy. However, polymerase chain reaction negativity was achieved only when a demonstrable CMV-specific CD8+ CTL res ponse was generated. Responses were never observed in asymptomatic CMV sero negative patients. Conclusions. We suggest that the generation of CMV-specific CD8+ CTL may be driven by, and seems to coincide with the suppression of, viral reactivati on, Direct monitoring of CMV-specific CD8+ CTL using an HLA-peptide tetrame r may prove to be of value in the management of patients after LT.