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

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 inf