Significance Statement: It has been reported that mTOR inhibitors (mTORis) are associated with a reduction in the incidence of cytomegalovirus (CMV) infection in organ transplant patients who are CMV seropositive (R+), but a mechanistic explanation has been lacking to date. This work showed that a dysfunctional T-cell phenotype (CD85j+ PD-1+) was associated with a higher risk of uncontrolled CMV infection after transplantation in patients who were R+, and that mTORis reduced CMV incidence and severity by reinvigorating αβ and γδ T-cell function. Dysfunctional T-cell phenotype could represent a new biomarker to predict post-transplantation infection in patients who are R+ and to stratify patients who should benefit from treatment with mTORis. Background: The reported association of mTOR-inhibitor (mTORi) treatment with a lower incidence of cytomegalovirus (CMV) infection in kidney transplant recipients (KTR) who are CMV seropositive (R+) remains unexplained. Methods: The incidence of CMV infection and T-cell profile was compared between KTRs treated with mTORis and mycophenolic acid (MPA), and in vitro mTORi effects on T-cell phenotype and functions were analyzed. Results: In KTRs who were R+ and treated with MPA, both αβ and γδ T cells displayed a more dysfunctional phenotype (PD-1+, CD85j+) at day 0 of transplantation in the 16 KTRs with severe CMV infection, as compared with the 17 KTRs without or with spontaneously resolving CMV infection. In patients treated with mTORis (n=27), the proportion of PD-1+ and CD85j+ αβ and γδ T cells decreased, when compared with patients treated with MPA (n=44), as did the frequency and severity of CMV infections. mTORi treatment also led to higher proportions of late-differentiated and cytotoxic γδ T cells and IFNγ-producing and cytotoxic αβ T cells. In vitro, mTORis increased proliferation, viability, and CMV-induced IFNγ production of T cells and decreased PD-1 and CD85j expression in T cells, which shifted the T cells to a more efficient EOMES^low Hobit^high profile. In γδ T cells, the mTORi effect was related to increased TCR signaling. Conclusion: Severe CMV replication is associated with a dysfunctional T-cell profile and mTORis improve T-cell fitness along with better control of CMV. A dysfunctional T-cell phenotype could serve as a new biomarker to predict post-transplantation infection and to stratify patients who should benefit from mTORi treatment. Clinical Trial registry name and registration number: Proportion of CMV Seropositive Kidney Transplant Recipients Who Will Develop a CMV Infection When Treated With an Immunosuppressive Regimen Including Everolimus and Reduced Dose of Cyclosporine Versus an Immunosuppressive Regimen With Mycophenolic Acid and Standard Dose of Cyclosporine A (EVERCMV), NCT02328963

Cytomegalovirus is a major infectious cause of mortality and morbidity following transplantation. We have previously demonstrated that the tissue-associated adaptive Vδ2^neg γδ T-cells are key effectors responding to CMV and associated to recovery, contrasting with their innate-like circulating counterparts, the Vγ9^posVδ2^pos T-cells that respond to phosphoantigens but not to CMV. A third additional Vγ9^negVδ2^pos subgroup with adaptive functions has been recently described in adults. Here, we demonstrate that these Vγ9^negVδ2^pos T-cells are also components of the CMV immune response while presenting with distinct characteristics from Vδ2^neg γδT-cells. In a cohort of kidney transplant recipients, CMV seropositivity was the unique clinical parameter associated with Vγ9^negVδ2^posT-cell expansion and differentiation. Extensive phenotyping demonstrated their substantial cytotoxic potential and activation during acute CMV primary infection or reinfection. In vitro, Vγ9^negVδ2^pos T-cells responded specifically to CMV-infected cells in a T-Cell Receptor-dependent manner and through strong IFNγ production. Finally, Vγ9^negVδ2^pos T-cells were the only γδT-cell subset which expansion tightly correlated with the severity of CMV disease. To conclude, our results identify a new player in the immune response against CMV and open interesting clinical perspectives for using Vγ9^negVδ2^pos T-cells as an immune marker for CMV disease severity in immunocompromised patients.

Cytomegalovirus (CMV) persists as the the most frequent opportunistic infection among solid organ transplant recipients. This multicentre trial aimed to test whether treatment with everolimus (EVR) could decrease the incidence of CMV DNAemia and disease. We randomized 186 CMV seropositive kidney transplant recipients in a 1:1 ratio to receive EVR or mycophenolic acid (MPA) in association with basiliximab, cyclosporin, and steroids and 87 in each group were analyzed. No universal prophylaxis was administered to either group. The composite primary endpoint was presence of CMV DNAemia, CMV treatment, graft loss, death, and discontinuation of the study at 6 months post-transplantation. In the modified intent-to-treat analysis, 42 (48.3%) and 70 (80.5%) patients in the EVR and MPA groups reached the primary endpoint (OR=0.21, CI95: 0.11-0.43, p<0.0001). Fewer patients of the EVR group received treatment for CMV (21.8% versus 47.1%, p=0.0007). EVR was discontinued in 31 (35.6%) patients. Among the 56 patients with ongoing EVR treatment, only 7.4% received treatment for CMV. In conclusion, EVR prevents CMV DNAemia requiring treatment in seropositive recipients as long as it is tolerated and maintained.

In this essay, we show that 3 distinct approaches to immunological exhaustion coexist and that they only partially overlap, generating potential misunderstandings. Exploring cases ranging from viral infections to cancer, we propose that it is crucial, for experimental and therapeutic purposes, to clarify these approaches and their interconnections so as to make the concept of exhaustion genuinely operational.

Cryptococcosis is the third most common cause of invasive fungal infection in solid organ transplant recipients and cryptococcal meningitis (CM) its main clinical presentation. CM outcomes, as well as its clinical features and radiological characteristics, have not yet been considered on a large scale in the context of kidney transplantation (KT). We performed a nationwide retrospective study of adult patients diagnosed with cryptococcosis after KT between 2002 and 2020 across 30 clinical centers in France. We sought to describe overall and graft survival based on whether KT patients with cryptococcosis developed CM or not. Clinical indicators of CNS involvement and brain radiological characteristics were assessed. Eighty-eight cases of cryptococcosis were diagnosed during the study period, with 61 (69.3%) cases of CM. Mortality was high (32.8%) at 12 months (M12) but not significantly different whether or not patients presented with CM. Baseline hyponatremia and at least one neurological symptom were independently associated with CM (p < 0.001). Positive serum cryptococcal antigen at diagnosis was also significantly associated with CM (p < 0.001). On magnetic resonance imaging (MRI), three patterns of brain injury were identified: parenchymal, meningeal, and vascular lesions. Although CM does not affect graft function directly, it entails a grim prognosis.