Improving our mechanistic understanding of the indirect effects of CMV infection in transplant recipients

Cytomegalovirus (CMV) is an immunomodulatory virus that indirectly increases the risk for bacterial, fungal, and viral infections. However, the pathogenesis of this phenomenon is poorly understood. We determined whether inflammatory responses to different Toll‐like receptor (TLR) ligands are blunted during CMV infection in solid‐organ transplant (SOT) patients. Peripheral blood mononuclear cells from 38 SOT patients with and without CMV were incubated in the presence of various viral, fungal, and bacterial TLR ligands. Cytokines were measured in the supernatant by multiplex enzyme‐linked immunosorbent assay. Patients had blunted cytokine responses to bacterial, fungal, and viral ligands during CMV infection when compared to the absence of CMV infection. This was independent of viral load, clinical presentation of CMV infection or immunosuppression, supporting the clinical observation in SOT recipients that CMV infection increases susceptibility to bacterial, fungal, and other viral infections. Moreover, in the absence of CMV infection, patients with subsequent CMV infection had lower cytokines in response to TLR ligands compared to those without subsequent CMV infection, suggesting that inherent differences in patients not directly related to CMV also contribute to this increased susceptibility. In summary, these data provide novel ex vivo evidence to support indirect effects of CMV.     

Long-term shedding of viable SARS-CoV-2 in kidney transplant recipients with COVID-19

The exact duration of viable SARS-CoV-2 shedding in kidney transplant recipients (KTRs) remains unclear. Here, we retrospectively investigated this issue using cell cultures of SARS-CoV-2 RT-PCR-positive nasopharyngeal samples (n = 40) obtained from 16 KTRs with symptomatic COVID-19 up to 39 days from symptom onset. A length of viable SARS-CoV-2 shedding >3 weeks from the onset of symptoms was identified in four KTRs (25%). These results suggest that a significant proportion of KTRs can shed viable SARS-CoV-2 for at least 3 weeks, which may favor the emergence of new variants. Based on these data, we recommend prolonging the isolation of KTRs with COVID-19 until negative SARS-CoV-2 RT-PCR testing.     

Increased incidence and unusual presentations of CMV disease in kidney transplant recipients after conversion to belatacept

Belatacept may increase cytomegalovirus (CMV) disease risk after conversion from CNI-based therapy. We analyzed CMV disease characteristics after belatacept conversion. Propensity score matching was used to compare CMV disease incidence in belatacept- and CNI-treated kidney transplant recipients (KTRs). CMV disease characteristics and risk factors under belatacept were analyzed. In total, 223 KTRs (median age [IQR] 59.2 years [45.4–68.5]) were converted to belatacept (median of 11.5 months [2.5–37.0] post-transplantation); 40/223 (17.9%) developed CMV disease. Independent risk factors included increased age (p = .0164), D+/R− CMV serostatus (p = .0220), and low eGFR at conversion (p = .0355). Among 181 belatacept-treated patients matched to 181 controls, 32/181 (17.7%) experienced CMV disease (vs. 5/181 controls [2.8%]). CMV disease cumulative incidences were 6.33 and 0.91/100 person-years (p-y) in belatacept and control groups, respectively. CMV disease risk was particularly high in elderly patients (converted >70 years) and those with eGFR <30 ml/min; cumulative incidences were 18.4 and 5.2/100 p-y, respectively. CMV diseases under belatacept were atypical, with late-onset disease (24/40 patients [60%]), high CMV seropositivity (27/40, 67%), increased severe and tissue-invasive disease rates (gastrointestinal involvement in 32/40 [80%]) and life-threatening diseases (4/40 [10%]). These findings should stimulate further research to secure the use of belatacept as a valuable rescue therapy in KTRs.     

Cytomegalovirus‐Responsive CD8+ T Cells Expand After Solid Organ Transplantation in the Absence of CMV Disease

Cytomegalovirus (CMV) is a major cause of morbidity and mortality in solid organ transplant recipients. Approximately 60% of adults are CMV seropositive, indicating previous exposure. Following resolution of the primary infection, CMV remains in a latent state. Reactivation is controlled by memory T cells in healthy individuals; transplant recipients have reduced memory T cell function due to chronic immunosuppressive therapies. In this study, CD8⁺ T cell responses to CMV polypeptides immediate‐early‐1 and pp65 were analyzed in 16 CMV‐seropositive kidney and heart transplant recipients longitudinally pretransplantation and posttransplantation. All patients received standard of care maintenance immunosuppression, antiviral prophylaxis, and CMV viral load monitoring, with approximately half receiving T cell–depleting induction therapy. The frequency of CMV‐responsive CD8⁺ T cells, defined by the production of effector molecules in response to CMV peptides, increased during the course of 1 year posttransplantation. The increase commenced after the completion of antiviral prophylaxis, and these T cells tended to be terminally differentiated effector cells. Based on this small cohort, these data suggest that even in the absence of disease, antigenic exposure may continually shape the CMV‐responsive T cell population posttransplantation.     

Natural killer cell function predicts severe infection in kidney transplant recipients

The aim of this study was to determine if natural killer cell number (CD3^?/CD16^±/CD56^±) and cytotoxic killing function predicts severity and frequency of infection in kidney transplant recipients. A cohort of 168 kidney transplant recipients with stable graft function underwent assessment of natural killer cell number and functional killing capacity immediately prior to entry into this prospective study. Participants were followed for 2 years for development of severe infection, defined as hospitalization for infection. Area under receiver operating characteristic (AUROC) curves were used to evaluate the accuracy of natural killer cell number and function for predicting severe infection. Adjusted odds ratios were determined by logistic regression. Fifty‐nine kidney transplant recipients (35%) developed severe infection and 7 (4%) died. Natural killer cell function was a better predictor of severe infection than natural killer cell number: AUROC 0.84 and 0.75, respectively (P = .018). Logistic regression demonstrated that after adjustment for age, transplant function, transplant duration, mycophenolate use, and increasing natural killer function (odds ratio [OR] 0.82, 95% confidence interval [CI] 0.74‐0.90; P < .0001) but not natural killer number (OR 0.96, 95% CI 0.93‐1.00; P = .051) remained significantly associated with a reduced likelihood of severe infection. Natural killer cell function predicts severe infection in kidney transplant recipients.     

A prospective multicenter observational study of cell‐mediated immunity as a predictor for cytomegalovirus infection in kidney transplant recipients

T cell immunity is essential for the control of cytomegalovirus (CMV) infection after transplantation. We evaluated a CMV‐specific peptide‐based enzyme‐linked immunosorbent spot (ELISPOT) assay to determine whether assay results could predict subsequent CMV events. Adult kidney transplant recipients at 43 centers underwent ELISPOT testing to enumerate interferon gamma (IFN‐γ) binding spot‐forming units (sfu) after stimulation of cells with an overlapping peptide pool of CMV phosphoprotein 65 (pp65) and immediate early‐1 (IE‐1) protein at the end of antiviral prophylaxis (EOP) and various time points thereafter. The primary outcome was a CMV event in the first posttransplant year. In 583 kidney transplant recipients (260 seropositive donor [D+]/seronegative recipient [R?] and 277 R+), CMV events occurred in 44 of 368 eligible patients (11.8%) at a median of 227 days (range 92‐360) posttransplant. A cutoff value of >40 sfu/2.5 × 10⁵ cells for either IE‐1 or pp65 was derived as a threshold for positivity, with a negative predictive value of >97% for CMV events. CMV events were significantly lower in assay positive vs assay negative patients (3.0% vs 19.5%, P < .0001 for pp65). Time to CMV event post‐EOP was significantly greater in those with sfu >40 at EOP (P < .0001). In this large, multicenter trial of kidney transplant recipients, we show that an assessment of CMV‐specific immunity using a novel ELISPOT assay is able to predict protection from CMV infection.     

CMV‐infected kidney grafts drive the expansion of blood‐borne CMV‐specific T cells restricted by shared class I HLA molecules via presentation on donor cells

We aimed to determine the role of cytomegalovirus (CMV)‐infected donor cells in the development of a CMV‐specific immune response in kidney transplant recipients. We assessed the CMV pp65‐specific immune response by using interferon‐? ELISPOT and dextramers in peripheral blood mononuclear cells from 115 recipients (D+R? 31, D+R + 44, D?R + 40) late after transplantation (mean 59 ± 42 months). Receiving a kidney from a D+ donor resulted in a higher number of IFN‐?‐producing anti‐CMV T cells (P = .004). This effect disappeared with the absence of shared HLA class I specificities between donors and recipients (P = .430). To confirm the role of donor cells in stimulating the expansion of newly developed CMV‐specific CD8⁺ T cells after transplantation, we compared the number of HLA‐A2–restricted CMV‐specific CD8⁺ T cells in primo‐infected recipients who received an HLA‐A2 or non–HLA‐A2 graft. The median of anti‐CMV pp65 T cells restricted by HLA‐A2 was very low for patients who received a non–HLA‐A2 graft vs an HLA‐A2 graft (300 [0‐14638] vs. 17972 [222‐85594] anti‐CMV pp65 CD8⁺ T cells/million CD8⁺ T cells, P = .001). This adds new evidence that CMV‐infected kidney donor cells present CMV peptides and drive an inflation of memory CMV‐specific CD8⁺ T cells, likely because of frequent CMV replications within the graft.     

Quantifying infection risks in incompatible living donor kidney transplant recipients

Desensitization has enabled incompatible living donor kidney transplantation (ILDKT) across HLA/ABO barriers, but added immunomodulation might put patients at increased risk of infections. We studied 475 recipients from our center from 2010 to 2015, categorized by desensitization intensity: none/compatible (n = 260), low (0-4 plasmaphereses, n = 47), moderate (5-9, n = 74), and high (≥10, n = 94). The 1-year cumulative incidence of infection was 50.1%, 49.8%, 66.0%, and 73.5% for recipients who received none, low, moderate, and high-intensity desensitization (P < .001). The most common infections were UTI (33.5% of ILDKT vs. 21.5% compatible), opportunistic (21.9% vs. 10.8%), and bloodstream (19.1% vs. 5.4%) (P < .001). In weighted models, a trend toward increased risk was seen in low (wIRR = _0.771.40_2.56,P = .3) and moderately (wIRR = _0.881.35_2.06,P = .2) desensitized recipients, with a statistically significant 2.22-fold (wIRR = _1.332.22_3.72,P = .002) increased risk in highly desensitized recipients. Recipients with ≥4 infections were at higher risk of prolonged hospitalization (wIRR = _2.623.57_4.88, P < .001) and death-censored graft loss (wHR = _1.154.01_13.95,P = .03). Post–KT infections are more common in desensitized ILDKT recipients. A subset of highly desensitized patients is at ultra-high risk for infections. Strategies should be designed to protect patients from the morbidity of recurrent infections, and to extend the survival benefit of ILDKT across the spectrum of recipients.     

COVID-19 severity in kidney transplant recipients is similar to nontransplant patients with similar comorbidities

Higher rates of severe COVID-19 have been reported in kidney transplant recipients (KTRs) compared to nontransplant patients. We aimed to determine if poorer outcomes were specifically related to chronic immunosuppression or underlying comorbidities. We used a 1:1 propensity score-matching method to compare survival and severe disease-free survival (defined as death and/or need for intensive care unit [ICU]) incidence in hospitalized KTRs and nontransplant control patients between February 26 and May 22, 2020. Patients were matched for risk factors of severe COVID-19: age, sex, body mass index, diabetes mellitus, preexisting cardiopathy, chronic lung disease, and basal renal function. We included 100 KTRs (median age [interquartile range (IQR)]) 64.7 years (55.3–73.1) in three French transplant centers. After a median follow-up of 13 days (7–30), transfer to ICU was required for 34 patients (34%) and death occurred in 26 patients (26%). Overall, 43 patients (43%) developed a severe disease during a median follow-up of 8.5 days (2–14). Propensity score matching to a large French cohort of 2017 patients hospitalized in 24 centers, revealed that survival was similar between KTRs and matched nontransplant patients with respective 30-day survival of 62.9% and 71% (p = .38) and severe disease-free 30-day survival of 50.6% and 47.5% (p = .91). These findings suggest that severity of COVID-19 in KTRs is related to their associated comorbidities and not to chronic immunosuppression.     

A systematic review and meta-analysis of COVID-19 in kidney transplant recipients: Lessons to be learned

Kidney transplant recipients (KTR) may be at increased risk of adverse COVID-19 outcomes, due to prevalent comorbidities and immunosuppressed status. Given the global differences in COVID-19 policies and treatments, a robust assessment of all evidence is necessary to evaluate the clinical course of COVID-19 in KTR. Studies on mortality and acute kidney injury (AKI) in KTR in the World Health Organization COVID-19 database were systematically reviewed. We selected studies published between March 2020 and January 18th 2021, including at least five KTR with COVID-19. Random-effects meta-analyses were performed to calculate overall proportions, including 95% confidence intervals (95% CI). Subgroup analyses were performed on time of submission, geographical region, sex, age, time after transplantation, comorbidities, and treatments. We included 74 studies with 5559 KTR with COVID-19 (64.0% males, mean age 58.2 years, mean 73 months after transplantation) in total. The risk of mortality, 23% (95% CI: 21%–27%), and AKI, 50% (95% CI: 44%–56%), is high among KTR with COVID-19, regardless of sex, age and comorbidities, underlining the call to accelerate vaccination programs for KTR. Given the suboptimal reporting across the identified studies, we urge researchers to consistently report anthropometrics, kidney function at baseline and discharge, (changes in) immunosuppressive therapy, AKI, and renal outcome among KTR.     

COVID‐19 in kidney transplant recipients

There is minimal information on coronavirus disease 2019 (COVID‐19) in immunocompromised individuals. We have studied 10 patients treated at 12 adult care hospitals. Ten kidney transplant recipients tested positive for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) by polymerase chain reaction, and 9 were admitted. The median age was 57 (interquartile range [IQR] 47‐67), 60% were male, 40% Caucasian, and 30% Black/African American. Median time from transplant to COVID‐19 testing was 2822 days (IQR 1272‐4592). The most common symptom was fever, followed by cough, myalgia, chills, and fatigue. The most common chest X‐ray and computed tomography abnormality was multifocal patchy opacities. Three patients had no abnormal findings. Leukopenia was seen in 20% of patients, and allograft function was stable in 50% of patients. Nine patients were on tacrolimus and a mycophenolic antimetabolite, and 70% were on prednisone. Hospitalized patients had their antimetabolite agent stopped. All hospitalized patients received hydroxychloroquine and azithromycin. Three patients died (30%), and 5 (50%) developed acute kidney injury. Kidney transplant recipients infected with COVID‐19 should be monitored closely in the setting of lowered immunosuppression. Most individuals required hospitalization and presenting symptoms were similar to those of nontransplant individuals.     

Cellular and humoral response after MRNA-1273 SARS-CoV-2 vaccine in kidney transplant recipients

According to preliminary data, seroconversion after mRNA SARS-CoV-2 vaccination might be unsatisfactory in Kidney Transplant Recipients (KTRs). However, it is unknown if seronegative patients develop at least a cellular response that could offer a certain grade of protection against SARS-CoV-2. To answer this question, we prospectively studied 148 recipients of either kidney (133) or kidney-pancreas (15) grafts with assessment of IgM/IgG spike (S) antibodies and ELISpot against the nucleocapside (N) and the S protein at baseline and 2 weeks after receiving the second dose of the mRNA-1273 (Moderna) vaccine. At baseline, 31 patients (20.9%) had either IgM/IgG or ELISpot positivity and were considered to be SARS-CoV-2-pre-immunized, while 117 (79.1%) patients had no signs of either cellular or humoral response and were considered SARS-CoV-2-naïve. After vaccination, naïve patients who developed either humoral or cellular response were finally 65.0%, of which 29.9% developed either IgG or IgM and 35.0% S-ELISpot positivity. Factors associated with vaccine unresponsiveness were diabetes and treatment with antithymocytes globulins during the last year. Side effects were consistent with that of the pivotal trial and no DSAs developed after vaccination. In conclusion, mRNA-1273 SARS-CoV-2 vaccine elicits either cellular or humoral response in almost two thirds of KTRs.     

Letermovir in lung transplant recipients with cytomegalovirus infection: A retrospective observational study

Letermovir is a new antiviral drug approved for the prophylaxis of CMV infection in allogeneic stem cell transplants. The aim of the study was to assess the therapeutic efficacy of letermovir in difficult to treat CMV infections in lung transplant recipients. All lung transplant recipients between March 2018 and August 2020, who have been treated with letermovir for ganciclovir-resistant or refractory CMV infection were included in the study and analysed retrospectively. In total, 28 patients were identified. CMV disease was present in 15 patients (53.6%). In 23 patients (82.1%), rapid response was noticed, and CMV-viral load could be significantly decreased (>1 log₁₀) after a median of 17 [14–27] days and cleared subsequently in all of these patients. Five patients (17.9%) were classified as non-responder. Thereof, development of a mutation of the CMV UL56 terminase (UL-56-Gen: C325Y) conferring letermovir resistance could be observed in three patients (60%). Common side effects were mild and mostly of gastrointestinal nature. Mild adjustments of the immunosuppressive drugs were mandatory upon treatment initiation with letermovir. In addition to other interventions, letermovir was effective in difficult to treat CMV infections in lung transplant recipients. However, in patients with treatment failure mutation conferring letermovir, resistance should be taken into account.     

T cell and antibody responses to SARS-CoV-2: Experience from a French transplantation and hemodialysis center during the COVID-19 pandemic

Immunosuppressed organ-transplanted patients are considered at risk for severe forms of COVID-19. Moreover, exaggerated innate and adaptive immune responses might be involved in severe progression of the disease. However, no data on the immune response to SARS-CoV-2 in transplanted patients are currently available. Here, we report the first assessment of antibody and T cell responses to SARS-CoV-2 in 11 kidney-transplanted patients recovered from RT-PCR–confirmed (n = 5) or initially suspected (n = 6) COVID-19. After reduction of immunosuppressive therapy, RT-PCR–confirmed COVID-19 transplant patients were able to mount vigorous antiviral T cell and antibody responses, as efficiently as two nontherapeutically immunosuppressed COVID-19 patients on hemodialysis. By contrast, six RT-PCR–negative patients displayed no antibody response. Among them, three showed very low numbers of SARS-CoV-2–reactive T cells, whereas no T cell response was detected in the other three, potentially ruling out COVID-19 diagnosis. Low levels of T cell reactivity to SARS-CoV-2 were also detected in seronegative healthy controls without known exposure to the virus. These results suggest that during COVID-19, monitoring both T cell and serological immunity might be helpful for the differential diagnosis of COVID-19 but are also needed to evaluate a potential role of antiviral T cells in the development of severe forms of the disease.     

Detection of Recently Discovered Human Polyomaviruses in a Longitudinal Kidney Transplant Cohort

A large number of human polyomaviruses have been discovered in the last 7 years. However, little is known about the clinical impact on vulnerable immunosuppressed patient populations. Blood, urine, and respiratory swabs collected from a prospective, longitudinal adult kidney transplant cohort (n = 167) generally pre‐operatively, at day 4, months 1, 3, and 6 posttransplant, and at BK viremic episodes within the first year were screened for 12 human polyomaviruses using real‐time polymerase chain reaction. Newly discovered polyomaviruses were most commonly detected in the respiratory tract, with persistent shedding seen for up to 6 months posttransplant. Merkel cell polyomavirus was the most common detection, but was not associated with clinical symptoms or subsequent development of skin cancer or other skin abnormalities. In contrast, KI polyomavirus was associated with respiratory disease in a subset of patients. Human polyomavirus 9, Malawi polyomavirus, and human polyomavirus 12 were not detected in any patient samples.     

Easier Control of Late‐Onset Cytomegalovirus Disease Following Universal Prophylaxis Through an Early Antiviral Immune Response in Donor‐Positive,Recipient‐Negative Kidney Transplants

Universal prophylaxis for cytomegalovirus (CMV) prevention is viable but, compared with a preemptive strategy, leads to higher incidence of late‐onset disease (LOD) associated with poor patient and graft survival. The purpose of this study was to compare LOD with early onset disease (EOD), with a focus on the highest risk kidney transplant recipients (KTRs): CMV seronegative recipients transplanted from seropositive donors (D+R?). Since CMV control depends on both antiviral treatment and specific immune response, we also compared Vδ2‐negative (Vδ2^neg) γδ T cell expansion involved in CMV infection resolution. EOD was defined as occurring <3 mo and LOD as occurring >3 mo after transplantation. Depending on the period, universal prophylaxis or preemptive treatment was used. Overall, 168 D+R? KTRs were included between 2003 and 2011. LOD was associated with a lower peak DNAemia (p = 0.04), fewer recurrences (odds ratio 0.16; 95% confidence interval 0.05–0.55; p = 0.01) and shorter anti‐CMV curative treatment (40 vs. 60 days, p < 0.0001). As a corollary, we found that Vδ2^neg γδ T cell expansion was faster in LOD than in EOD (31 vs. 168 days after the beginning of CMV disease, p < 0.0001). In D+R? KTRs, universal prophylaxis is associated with more LOD, which had better infection management and a faster immune response. These results support the use of universal prophylaxis over a preemptive strategy and reappraise outcomes of LOD.