Association of T Gamma Delta-CD16+ Cells and Anti-CMV Immunoglobulins in the Prevention of CMV Infection

Overview

CMV infection in transplantation remains the most frequent infectious complication causing increased morbidity and mortality. International recommendations advocate prevention of this infection by instituting direct antiviral treatment or monitoring viral replication by PCR with the start of curative antiviral treatment when the DNAemia is positive. The risk of CMV infection varies according to the serostatus of the donor (D) and recipient (R) at the time of transplantation. In the absence of prophylaxis, CMV infection occurs in 60-80% of D+R-, 50-60% of D+R+ and 25-50% of D-R+. The humoral anti-CMV response is represented by the production of antibodies to envelope proteins (gB and gH) and to molecules involved in viral attachment and entry into target cells. However, the majority of CMV-specific antibodies do not have antiviral neutralising activity. The investigators have identified a new player in the specific anti-CMV response expressing the Fc RIIIa receptor (CD16), that interacts with anti-CMV immunoglobulins (Ig): the Tgamma-delta V delta 2-negative lymphocyte (LTgdVd2neg). This lymphocyte subpopulation shows persistent expansion in the peripheral blood of kidney transplant patients with CMV infection. These cells express an effector-memory phenotype (CD45RA+/CD27-). This expansion is associated with resolution of infection in patients. The investigators have shown that CD16 is specifically and constitutively expressed on the surface of CMV-induced LTgdVd2neg in healthy volunteers and kidney transplant patients. The investigators have observed that one of the antiviral activities of anti-CMV IgG lies in its binding to the Fc RIIIa receptor (CD16) on the surface of LTgdVd2neg. The anti-CMV IgGs capturing virions thus activate CD16+ LTgdVd2neg with production of IFN interferon which in turn is responsible for inhibition of CMV viral multiplication. Anti-CMV IgG is a recommended therapeutic option, with a marketing authorisation for the prevention of CMV infection in kidney transplantation in Europe and a Temporary Authorisation for Use in France. Thus, R+ patients expressing a significant level of LTgdVd2neg CD16+ at D0 of transplantation could be protected against CMV, in the absence of direct antiviral treatment by the addition of anti-CMV Ig.

SYNTAGME is a single-centre prospective phase II pilot study. Transplant candidates from our centre who meet the inclusion criteria without exclusion criteria will be offered this study. Anti-CMV Ig infusions will be performed the day of transplantation at 100 units per kilo of body weight and then every 15 days for a total of 6 infusions. Systematic and frequent monitoring for the occurrence of CMV DNAemia will be performed throughout this study. Real-time quantitative CMV PCR on whole blood (WHO standard provided by the National Institute for Biological Standards and Control) will be performed every week until M3, then every fortnight until 4 months and then at months 5, 6, 9 and 12. CMV infection will be defined by the presence of a positive CMV PCR in whole blood. Universal prophylaxis with VALGANCICLOVIR will be prohibited. Pre-emptive antiviral treatment will be initiated in case of CMV infection, if the DNAemia reaches the threshold chosen by the centre, which is 5000 IU/ml. The choice of treatment will be left to the discretion of the clinician: IV ganciclovir (5mg/Kg/12H) or valganciclovir (900mg/12H) until viral replication is negated. Doses will be adjusted for kidney function using the Cockcroft-Gault formula, in accordance with laboratory recommendations.