Surveillance of γδ T Cells Predicts Cytomegalovirus Infection Resolution in Kidney Transplants

Abstract

Cytomegalovirus (CMV) infection in solid-organ transplantation is associated with increased morbidity and mortality, particularly if a CMV mutant strain with antiviral resistance emerges. Monitoring CMV-specific T cell response could provide relevant information for patient care. We and others have shown the involvement of Vδ2(neg) γδ T cells in controlling CMV infection. Here, we assessed if Vδ2(neg) γδ T cell kinetics in peripheral blood predict CMV infection resolution and emergence of a mutant strain in high-risk recipients of kidney transplants, including 168 seronegative recipients receiving organs from seropositive donors (D+R-) and 104 seropositive recipients receiving antithymocyte globulins (R+/ATG). Vδ2(neg) γδ T cell percentages were serially determined in patients grafted between 2003 and 2011. The growing phase of Vδ2(neg) γδ T cells was monitored in each infected patient, and the expansion rate during this phase was estimated individually by a linear mixed model. A Vδ2(neg) γδ T cell expansion rate of ˃0.06% per day predicted the growing phase. The time after infection at which an expansion rate of 0.06% per day occurred was correlated with the resolution of CMV DNAemia (r=0.91; P<0.001). At 49 days of antiviral treatment, Vδ2(neg) γδ T cell expansion onset was associated with recovery, whereas absence of expansion was associated with recurrent disease and DNAemia. The appearance of antiviral-resistant mutant CMV strains was associated with delayed Vδ2(neg) γδ T cell expansion (P<0.001). In conclusion, longitudinal surveillance of Vδ2(neg) γδ T cells in recipients of kidney transplants may predict CMV infection resolution and antiviral drug resistance.

Keywords: cytomegalovirus; immunology; immunosuppression; kidney transplantation.

Figure 1.

Kinetics of Vδ2^neg γδ T cells in (A) D+R− and (B) R+/ATG patients from day 0 of CMV infection. In infected patients (red lines), Vδ2^neg γδ T cells percentage (median; 1st and 3rd quartiles) interpolated data are represented from day 0 of CMV infection. In uninfected patients (blue line), all Vδ2^neg γδ T cells percentage values during the follow-up period are pooled and represented (median [solid line]; 1st and 3rd quartiles [dashed lines]). P values were obtained using Mann–Whitney tests. *P<0.05 in D+R− infected patients (comparison of Vδ2^neg γδ T cells percentages before and after Vδ2^neg γδ T cell expansion); **P<0.05 (comparison of Vδ2^neg γδ T cells percentage baselines between R+ infected and uninfected patients); ***P<0.05 in R+/ATG infected patients (comparison of Vδ2^neg γδ T cells percentages before and after Vδ2^neg γδ T cell expansion).

Figure 2.

Estimation of Vδ2^neg γδ T cell expansion rate using a linear mixed model in D+R− infected patients (A) and in R+/ATG infected patients (B). Each infected patient had a growing phase of Vδ2^neg γδ T cells identified by careful individual examination of the whole kinetics of Vδ2^neg γδ T cells. The rate of expansion (R) was determined, patient by patient, during this growing phase. (A) Represents the estimation of expansion rate in D+R− infected patient. (B) Represents the estimation of expansion rate in R+/ATG infected patients.

Figure 3.

Estimation of the threshold of Vδ2^neg γδ T cell expansion rate. A represents a histogram of maximal Vδ2^neg γδ T cell increase (in percentage of Vδ2^neg γδ T cells per day) between two determinations before the growing phase of Vδ2^neg γδ T cells kinetics. B represents a histogram of estimated Vδ2^neg γδ T cell expansion rates (in percentages of Vδ2^neg γδ T cells per day) with the linear mixed model during the growing phase of Vδ2^neg γδ T cells kinetics. A rate of expansion of 0.06% per day was the best threshold to maximize the validity of the definition of the growing phase of Vδ2^neg γδ T cells kinetics. (C) Receiver operating characteristics curve of estimated Vδ2^neg γδ T cell expansion rates during the growing phase of Vδ2^neg γδ T cells kinetics versus maximal Vδ2^neg γδ T cell increases between two determinations before this growing phase. Thus, for a given infected patient, an increase of Vδ2^neg γδ T cells >0.06% per day between two successive determinations predicted the growing phase, with Se of 77%, Spe of 90%, PPV of 88%, and NPV of 75% (AUC=0.91).

Figure 4.

Time of Vδ2^neg γδ T cell expansion is correlated with the CMV DNAemia resolution. In (A) D+R− infected and (B) R+/ATG infected patients, linear regressions are represented between the CMV DNAemia resolution (days) and the time of Vδ2^neg γδ T cell expansion (days). Scales are different between A and B with regards to the longer CMV DNAemia duration and the Vδ2^neg γδ T cell expansion in D+R− compared with R+/ATG patients. P values were obtained using the Fisher test.

Figure 5.

Absence of Vδ2^neg γδ T cell expansion at the end of the antiviral treatment predicts recurrent CMV DNAemia/disease. At the end of antiviral treatment (49 days), data about recovery, recurrent CMV DNAemia, and recurrent disease were collected as well as the occurrence of Vδ2^neg γδ T cell expansion; 94.7% (94.67% and 94.73%) of patients with recovery had a Vδ2^neg γδ T cell expansion onset, and 86.1% (86% and 86.2%) of patients with recurrent CMV DNAemia and 92.6% (92.51% and 92.69%) of patients with recurrent disease were associated with the absence of Vδ2^neg γδ T cell expansion.

Figure 6.

Vδ2^neg γδ T cell kinetics in D+R− infected patients with versus without antiviral drug resistance. Prolonged positive CMV DNAemia after Vδ2^neg γδ T cell expansion in the case of AVR. A represents box plots comparing time (days) between Vδ2^neg γδ T cell expansion (days) and the CMV DNAemia negativation in D+R− infected patients with versus without the emergence of a mutant strain. P value was obtained with a Mann–Whitney test. B) represents box plots comparing the time of Vδ2^neg γδ T cell expansion (days) in D+R− infected patients with versus without the emergence of a mutant strain. A time of Vδ2^neg γδ T cell expansion above 76 days was predictive of the emergence of a mutant strain (Se of 100%, Spe of 60%, PPV of 47%, and NPV of 100%). P value was obtained using Mann–Whitney test.

Figure 7.

Distribution of the patients. 168 D+R2 patients with either anti–IL-2 receptor antibody (n=114) or ATG (n=54) and 104 R+/ATG patients were included between January 1, 2003 and December 31, 2011, who experienced or not experienced CMV infection. Peripheral blood immunophenotyping determinations were longitudinally determined for each patient.