1587. Clinical Utility of a Cytomegalovirus (CMV)-specific T Cell Assay in Assessing the Risk of Post-Prophylaxis CMV Infection and Post-Treatment Relapse

Abstract Background Cytomegalovirus (CMV) causes significant morbidity in solid organ transplant recipients (SOTR). As a lack of immunity predisposes to infection, a laboratory test that measures CMV-specific cell-mediated immunity (CMV CMI) may help guide antiviral prophylaxis, predict relapses and correlate with outcomes. We assessed CMV CMI in CMV D+/R- patients during valganciclovir primary prophylaxis and in CMV viremic SOTRs during antiviral treatment, and correlated the results with post-prophylaxis CMV infection and post-treatment relapse, respectively. Methods CMV CMI was assessed in two groups of SOTRs using the QuantiFERON© CMV interferon-gamma release assay (IGRA), with level >0.2 IU/mL suggestive of immunity. The first group included CMV D+/R- SOTRs who underwent monthly CMV CMI testing during 6 months of valganciclovir prophylaxis. These patients were prospectively followed for CMV episodes for 1 year post transplant. The second group included SOTRs with CMV viremia or disease, who underwent CMV CMI testing at time of CMV diagnosis and at various time points during antiviral treatment. These patients were prospectively followed for CMV relapse for 1 year post-primary CMV episode. Standard definitions were used to define CMV infection and disease. Results In the primary prophylaxis cohort, 24 CMV mismatched (D+/R-) SOTRs were enrolled. Only 1 patient (4.2%) demonstrated a CMV CMI >0.2 IU/mL by the end of prophylaxis; this patient did not develop CMV disease. Four (16.6%) patients developed post-prophylaxis CMV infection, none of which had CMV CMI >0.2 IU/ml. In the post-treatment cohort, 20 CMV viremic SOTRs were enrolled, including 12 D+/R- (60%). Eighteen (90%) had CMV CMI levels >0.2 IU/mL by end of treatment and none developed CMV relapse. In contrast, the single patient who relapsed after treatment had a CMV CMI response < 0.2 IU/ml (p=0.05). Conclusion CMV D+/R- SOTRs are unlikely to develop CMV CMI during valganciclovir prophylaxis. Thus, the utility of CMV CMI for risk stratification of post-prophylaxis CMV infection in CMV D+/R- SOTRs is questionable. Conversely, CMV CMI testing may potentially be a useful marker of CMV relapse risk after treatment and guide the role of secondary antiviral prophylaxis. Disclosures Elitza Theel, PhD, D(ABMM), Euroimmun US: Advisor/Consultant|Oxford Immunotech: Advisor/Consultant|Roche Diagnostics: Advisor/Consultant|Serimmune Inc: Advisor/Consultant Raymund R. Razonable, MD, American Society of Transplantation: Board Member|gilead: Grant/Research Support|novartis: DSMB|regeneron: Grant/Research Support|Roche: Grant/Research Support.