Evolution of CMV Antiviral T-cell Immunity Over the Next Six Months Initiation of Treatment With Belatacept.

Inclusion Criteria: * Renal transplant follow-up at Rouen University Hospital * Clinico-biological intolerance to anticalcineurins defined by GFR \< 25 mL/min and/or water and sodium overload justifying the prescription of loop diuretics and/or post-transplant diabetes and/or resistant hypertension (requiring at least 3 treatments antihypertensives including a thiazide diuretic to reach an objective ≤ 140/90 mmHg). * Having performed a graft biopsy \< 3 months old finding lesions of fibrous endarteritis ≥ 2 or arteriolar hyalinosis ≥ 2 * Having undergone collegial validation for the initiation of treatment with belatacept combined with 3-month anti-CMV prophylaxis with oral Valganciclovir. * Absence of contraindication to belatacept * Patient who has never received belatacept * Having a positive CMV serological status Exclusion Criteria: * Patient with symptomatic infection * Pregnant or parturient or breast-feeding woman or lack of proven effective contraception * Person deprived of liberty by an administrative or judicial decision or person placed under legal safeguard / sub-tutorship or curatorship * Patient participating in another therapeutic trial or having participated in another trial within 1 month