Respiratory mucosal delivery of next-generation COVID-19 vaccine provides robust protection against both ancestral and variant strains of SARS-CoV-2.

The emerging SARS-CoV-2 variants of concern (VOCs) threaten the effectiveness of current COVID-19 vaccines administered intramuscularly and designed to only target the spike protein. There is a pressing need to develop next-generation vaccine strategies for broader and long-lasting protection. Using adenoviral vectors (Ad) of human and chimpanzee origin, we evaluated Ad-vectored trivalent COVID-19 vaccines expressing spike-1, nucleocapsid, and RdRp antigens in murine models. We show that single-dose intranasal immunization, particularly with chimpanzee Ad-vectored vaccine, is superior to intramuscular immunization in induction of the tripartite protective immunity consisting of local and systemic antibody responses, mucosal tissue-resident memory T cells and mucosal trained innate immunity. We further show that intranasal immunization provides protection against both the ancestral SARS-CoV-2 and two VOC, B.1.1.7 and B.1.351. Our findings indicate that respiratory mucosal delivery of Ad-vectored multivalent vaccine represents an effective next-generation COVID-19 vaccine strategy to induce all-around mucosal immunity against current and future VOC.

SARS-CoV-2 breakthrough infection induces rapid memory and de novo T cell responses.

Although the protective role of neutralizing antibodies against COVID-19 is well established, questions remain about the relative importance of cellular immunity. Using 6 pMHC multimers in a cohort with early and frequent sampling, we define the phenotype and kinetics of recalled and primary T cell responses following Delta or Omicron breakthrough infection in previously vaccinated individuals. Recall of spike-specific CD4+ T cells was rapid, with cellular proliferation and extensive activation evident as early as 1 day post symptom onset. Similarly, spike-specific CD8+ T cells were rapidly activated but showed variable degrees of expansion. The frequency of activated SARS-CoV-2-specific CD8+ T cells at baseline and peak inversely correlated with peak SARS-CoV-2 RNA levels in nasal swabs and accelerated viral clearance. Our study demonstrates that a rapid and extensive recall of memory T cell populations occurs early after breakthrough infection and suggests that CD8+ T cells contribute to the control of viral replication in breakthrough SARS-CoV-2 infections.

The magnitude and timing of recalled immunity after breakthrough infection is shaped by SARS-CoV-2 variants.

Vaccination against SARS-CoV-2 protects from infection and improves clinical outcomes in breakthrough infections, likely reflecting residual vaccine-elicited immunity and recall of immunological memory. Here, we define the early kinetics of spike-specific humoral and cellular immunity after vaccination of seropositive individuals and after Delta or Omicron breakthrough infection in vaccinated individuals. Early longitudinal sampling revealed the timing and magnitude of recall, with the phenotypic activation of B cells preceding an increase in neutralizing antibody titers. While vaccination of seropositive individuals resulted in robust recall of humoral and T cell immunity, recall of vaccine-elicited responses was delayed and variable in magnitude during breakthrough infections and depended on the infecting variant of concern. While the delayed kinetics of immune recall provides a potential mechanism for the lack of early control of viral replication, the recall of antibodies coincided with viral clearance and likely underpins the protective effects of vaccination against severe COVID-19.

COVID-19 immune signatures reveal stable antiviral T cell function despite declining humoral responses.

Cellular and humoral immunity to SARS-CoV-2 is critical to control primary infection and correlates with severity of disease. The role of SARS-CoV-2-specific T cell immunity, its relationship to antibodies, and pre-existing immunity against endemic coronaviruses (huCoV), which has been hypothesized to be protective, were investigated in 82 healthy donors (HDs), 204 recovered (RCs), and 92 active COVID-19 patients (ACs). ACs had high amounts of anti-SARS-CoV-2 nucleocapsid and spike IgG but lymphopenia and overall reduced antiviral T cell responses due to the inflammatory milieu, expression of inhibitory molecules (PD-1, Tim-3) as well as effector caspase-3, -7, and -8 activity in T cells. SARS-CoV-2-specific T cell immunity conferred by polyfunctional, mainly interferon-γ-secreting CD4+ T cells remained stable throughout convalescence, whereas humoral responses declined. Immune responses toward huCoV in RCs with mild disease and strong cellular SARS-CoV-2 T cell reactivity imply a protective role of pre-existing immunity against huCoV.

Memory CD8+ T cell-mediated protection against liver-stage malaria.

Nearly half of the world's population is at risk of malaria, a disease caused by the protozoan parasite Plasmodium, which is estimated to cause more than 240,000,000 infections and kill more than 600,000 people annually. The emergence of Plasmodia resistant to chemoprophylactic treatment highlights the urgency to develop more effective vaccines. In this regard, whole sporozoite vaccination approaches in murine models and human challenge studies have provided substantial insight into the immune correlates of protection from malaria. From these studies, CD8+ T cells have come to the forefront, being identified as critical for vaccine-mediated liver-stage immunity that can prevent the establishment of the symptomatic blood stages and subsequent transmission of infection. However, the unique biological characteristics required for CD8+ T cell protection from liver-stage malaria dictate that more work must be done to design effective vaccines. In this review, we will highlight a subset of studies that reveal basic aspects of memory CD8+ T cell-mediated protection from liver-stage malaria infection.

Identification of a unique subset of tissue-resident memory CD4+ T cells in Crohn's disease.

T cells differentiate into highly diverse subsets and display plasticity depending on the environment. Although lymphocytes are key mediators of inflammation, functional specialization of T cells in inflammatory bowel disease (IBD) has not been effectively described. Here, we performed deep profiling of T cells in the intestinal mucosa of IBD and identified a CD4+ tissue-resident memory T cell (Trm) subset that is increased in Crohn's disease (CD) showing unique inflammatory properties. Functionally and transcriptionally distinct CD4+ Trm subsets are observed in the inflamed gut mucosa, among which a CD-specific CD4+ Trm subset, expressing CD161 and CCR5 along with CD103, displays previously unrecognized pleiotropic signatures of innate and effector activities. These inflammatory features are further enhanced by their spatial proximity to gut epithelial cells. Furthermore, the CD-specific CD4+ Trm subset is the most predominant producer of type 1 inflammatory cytokines upon various stimulations among all CD4+ T cells, suggesting that the accumulation of this T cell subset is a pathological hallmark of CD. Our results provide comprehensive insights into the pathogenesis of IBD, paving the way for decoding of the molecular mechanisms underlying this disease.

Impact of antiretroviral therapy during primary HIV infection on T-cell immunity after treatment interruption.

This study aims to understand the impact of early antiretroviral therapy (ART) on HIV-specific T-cell responses measured after treatment interruption may inform strategies to deliver ART-free immune-mediated viral suppression. HIV-specific T-cell immunity was analysed using gamma interferon enzyme-linked immunospot assays in two studies. SPARTAC included individuals with primary HIV infection randomised to 48 weeks of ART (n = 24) or no immediate therapy (n = 37). The PITCH (n = 7) cohort started antiretroviral therapy in primary infection for at least one year, followed by TI. In SPARTAC, participants treated in PHI for 48 weeks followed by TI for 12 weeks, and those who remained untreated for 60 weeks made similar HIV Gag-directed responses (both magnitude and breadth) at week 60. However, the treated group made a greater proportion of novel HIV Gag-directed responses by Week 60, suggestive of a greater reserve to produce new potentially protective responses. In the more intensively followed PITCH study, 6/7 participants showed dominant Gag and/or Pol-specific responses post-TI compared with pre-TI. Although early ART in PHI was not associated with major differences in HIV-specific immunity following TI compared with untreated participants, the potential to make more new Gag-directed responses warrants further investigation as this may inform strategies to achieve ART-free control.

Suppression of AGRN enhances CD8+ T cell recruitment and inhibits breast cancer progression.

Breast cancer (BC) stands as a prominent contributor to global cancer-related mortality, with an increasing incidence annually. This study aims to investigate AGRN gene expression in BC, as well as explore its influence on the tumor immune microenvironment. AGRN displayed a pronounced upregulation in BC tissues relative to paracancerous tissues. Single-cell RNA analysis highlighted AGRN-specific elevation within cancer cell clusters and also showed expression expressed in stromal as well as immune cell clusters. AGRN upregulation was positively correlated with clinicopathological stage and negatively correlated with BC prognosis. As revealed by the in vitro experiment, AGRN knockdown effectively hinders BC cells in terms of proliferation, invasion as well as migration. AGRN protein, which may interact with EXT1, LRP4, RAPSN, etc., was primarily distributed in the cell cytoplasm. Notably, immune factors might interact with AGRN in BC, evidenced by its discernible associations with immunofactors like IL10, CD274, and PVRL2. Mass spectrometry and immunohistochemistry revealed that the reduction of AGRN led to an increase in CD8+ T cells with triple-negative breast cancer (TNBC). Mechanistically, the connection between TRIM7 and PD-L1 is improved by AGRN, acting as a scaffold, thereby facilitating the accelerated degradation of PD-L1 by TRIM7. Downregulation of AGRN inhibits BC progression and increases CD8+ T cell recruitment. Targeting AGRN may contribute to BC treatment. The biomarker AGRN, serving as a therapeutic target for BC, emerges as a prospective avenue for enhancing both diagnosis and prognosis in BC cases.

Intranasal vaccination with engineered BCG expressing CCL2 induces a stronger immune barrier against Mycobacterium tuberculosis than BCG.

Intradermal Mycobacterium bovis Bacillus Calmette-Guérin (BCG) vaccination is currently the only licensed strategy for preventing tuberculosis (TB). It provides limited protection against pulmonary TB. To enhance the efficacy of BCG, we developed a recombinant BCG expressing exogenous monocyte chemoattractant CC chemokine ligand 2 (CCL2) called rBCG-CCL2. Co-culturing macrophages with rBCG-CCL2 enhances their abilities in migration, phagocytosis, and effector molecule expression. In the mouse model, intranasal vaccination with rBCG-CCL2 induced greater immune cell infiltration and a more extensive innate immune response in lung compared to vaccination with parental BCG, as determined by multiparameter flow cytometry, transcriptomic analysis, and pathological assessments. Moreover, rBCG-CCL2 induced a high frequency of activated macrophages and antigen-specific T helper 1 (Th1) and Th17 T cells in lungs. The enhanced immune microenvironment responded more effectively to intravenous challenge with Mycobacterium tuberculosis (Mtb) H37Ra, leading to significant reductions in H37Ra burden and pathological damage to the lungs and spleen. Intranasal rBCG-CCL2-vaccinated mice rapidly initiated pro-inflammatory Th1 cytokine release and reduced pathological damage to the lungs and spleen during the early stage of H37Ra challenge. The finding that co-expression of CCL2 synergistically enhances the immune barrier induced by BCG provides a model for defining immune correlates and mechanisms of vaccine-elicited protection against TB.

Cell-intrinsic and -extrinsic roles of miRNAs in regulating T cell immunity.

T cells are crucial to generate an effective response against numerous invading microbial pathogens and play a pivotal role in tumor surveillance and elimination. However, unwanted T cell activation can also lead to deleterious immune-mediated inflammation and tissue damage. To ensure that an optimal T cell response can be established, each step, beginning from T cell development in the thymus to their activation and function in the periphery, is tightly regulated by many transcription factors and epigenetic regulators including microRNAs (miRNAs). Here, we first summarize recent progress in identifying major immune regulatory miRNAs in controlling the differentiation and function of distinct T cell subsets. Moreover, as emerging evidence has demonstrated that miRNAs can impact T cell immunity through targeting both immune- and non-immune cell populations that T cells closely interact with, the T cell-extrinsic role of miRNAs in regulating different aspects of T cell biology is also addressed. Finally, we discuss the complex nature of miRNA-mediated control of T cell immunity and highlight important questions that remain to be further investigated.

Kinetics and Durability of Antibody and T-Cell Responses to SARS-CoV-2 in Children.

BACKGROUND: The kinetics and durability of T-cell responses to SARS-CoV-2 in children are not well characterized. We studied a cohort of children aged 6 months to 20 years with COVID-19 in whom peripheral blood mononuclear cells and sera were archived at approximately 1, 6, and 12 months after symptom onset. METHODS: We compared antibody responses (n = 85) and T-cell responses (n = 30) to nucleocapsid (N) and spike (S) glycoprotein over time across 4 age strata: 6 months to 5 years and 5-9, 10-14, and 15-20 years. RESULTS: N-specific antibody responses declined over time, becoming undetectable in 26 (81%) of 32 children by approximately 1 year postinfection. Functional breadth of anti-N CD4+ T-cell responses also declined over time and were positively correlated with N-antibody responses (Pearson r = .31, P = .008). CD4+ T-cell responses to S displayed greater functional breadth than N in unvaccinated children and, with neutralization titers, were stable over time and similar across age strata. Functional profiles of CD4+ T-cell responses against S were not significantly modulated by vaccination. CONCLUSIONS: Our data reveal durable age-independent T-cell immunity to SARS-CoV-2 structural proteins in children over time following COVID-19 infection as well as S-antibody responses in comparison with declining antibody responses to N.

Exposure to HIV is associated with altered composition of maternal microchimeric T cells in infants.

HIV exposed but uninfected infants (iHEU) display altered immunity and are at increased risk of infection. We previously reported that iHEU have decreased maternal microchimerism (MMc)-maternal cells transferred to the offspring in utero/during breastfeeding. We quantified MMc in T cell subpopulations in iHEU and unexposed infants (iHU) to determine whether a selective deficiency in MMc contributes to altered cellular immunity. Across all infants, MMc levels were highest in CD8+ T cells; however, the level of CD8+ T cell MMc was lower in iHEU versus iHU. In limited functional studies, we did not identify CMV-specific MMc during infant primary infection.

Reconstitution of norovirus-specific T cell responses following hematopoietic stem cell transplantation in patients with inborn errors of immunity and chronic norovirus infection.

BACKGROUND: Chronic norovirus infection (CNI) causes significant morbidity in immunocompromised patients. No effective prevention or treatment currently exists. METHODS: Two patients with inborn errors of immunity, X- linked severe combined immunodeficiency (X-SCID) and DOCK8 deficiency, were followed longitudinally for clinical course, immune reconstitution, norovirus-specific T cell (NST) response, B cell reconstitution, and norovirus-specific antibody production. Samples were obtained in the peri-hematopoietic stem cell transplant setting (HSCT) before and after CNI clearance. The norovirus strain causing CNI was followed longitudinally for norovirus stool viral loads and sequencing. RESULTS: The noroviruses were identified as GII.4 Sydney[P4 New Orleans] in one patient and GII.17[P17] in the other. An exacerbation of diarrhea post-HSCT in the patient with X-SCID was consistent with norovirus infection but not with graft-vs-host-disease on pathologic samples. Both patients recovered polyfunctional NSTs in the CD4 and CD8 T cell compartments which recognized multiple norovirus structural and non-structural viral antigens. T cell responses were minimal during active CNI but detectable after resolution. Mapping of norovirus-specific T cell responses between the patient with DOCK8 and his matched sibling donor were nearly identical. B cell reconstitution or new endogenous antibody production for IgA or IgG were not observed. CONCLUSION: This report is the first to demonstrate reconstitution of norovirus-specific T cell immunity after HSCT closely temporally aligned with clearance of CNI suggesting that cellular immunity is sufficient for norovirus clearance.

Prevention and treatment of HPV-related cancer through a mRNA vaccine expressing APC-targeting antigen.

Persistent human papillomavirus (HPV) infection is associated with multiple malignancies. Developing therapeutic vaccines to eliminate HPV-infected and malignant cells holds significant value. In this study, we introduced a lipid nanoparticle encapsulated mRNA vaccine expressing tHA-mE7-mE6. Mutations were introduced into E6 and E7 of HPV to eliminate their tumourigenicity. A truncated influenza haemagglutinin protein (tHA), which binds to the CD209 receptor on the surface of dendritic cells (DCs), was fused with mE7-mE6 in order to allow efficient uptake of antigen by antigen presenting cells. The tHA-mE7-mE6 (mRNA) showed higher therapeutic efficacy than mE7-mE6 (mRNA) in an E6 and E7+ tumour model. The treatment resulted in complete tumour regression and prevented tumour formation. Strong CD8+ T-cell immune response was induced, contributing to preventing and curing of E6 and E7+ tumour. Antigen-specific CD8+ T were found in spleens, peripheral blood and in tumours. In addition, the tumour infiltration of DC and NK cells were increased post therapy. In conclusion, this study described a therapeutic mRNA vaccine inducing strong anti-tumour immunity in peripheral and in tumour microenvironment, holding promising potential to treat HPV-induced cancer and to prevent cancer recurrence.

Lack of shared neoantigens in prevalent mutations in cancer.

Tumors are mostly characterized by genetic instability, as result of mutations in surveillance mechanisms, such as DNA damage checkpoint, DNA repair machinery and mitotic checkpoint. Defect in one or more of these mechanisms causes additive accumulation of mutations. Some of these mutations are drivers of transformation and are positively selected during the evolution of the cancer, giving a growth advantage on the cancer cells. If such mutations would result in mutated neoantigens, these could be actionable targets for cancer vaccines and/or adoptive cell therapies. However, the results of the present analysis show, for the first time, that the most prevalent mutations identified in human cancers do not express mutated neoantigens. The hypothesis is that this is the result of the selection operated by the immune system in the very early stages of tumor development. At that stage, the tumor cells characterized by mutations giving rise to highly antigenic non-self-mutated neoantigens would be efficiently targeted and eliminated. Consequently, the outgrowing tumor cells cannot be controlled by the immune system, with an ultimate growth advantage to form large tumors embedded in an immunosuppressive tumor microenvironment (TME). The outcome of such a negative selection operated by the immune system is that the development of off-the-shelf vaccines, based on shared mutated neoantigens, does not seem to be at hand. This finding represents the first demonstration of the key role of the immune system on shaping the tumor antigen presentation and the implication in the development of antitumor immunological strategies.

Characterization of Th17 tissue-resident memory cells in non-inflamed intestinal tissue of Crohn's disease patients.

Crohn's disease (CD) is a chronic inflammatory disorder affecting the bowel wall. Tissue-resident memory T (Trm) cells are implicated in CD, yet their characteristics remain unclear. We aimed to investigate the transcriptional profiles and functional characteristics of Trm cells in the small bowel of CD and their interactions with immune cells. Seven patients with CD and four with ulcerative colitis as controls were included. Single-cell RNA sequencing and paired T cell receptor sequencing assessed T cell subsets and transcriptional signatures in lamina propria (LP) and submucosa/muscularis propria-enriched fractions (SM/MP) from small bowel tissue samples. We detected 58,123 T cells grouped into 16 populations, including the CD4+ Trm cells with a Th17 signature and CD8+ Trm clusters. In CD, CD4+ Trm cells with a Th17 signature, termed Th17 Trm, showed significantly increased proportions within both the LP and SM/MP areas. The Th17 Trm cluster demonstrated heightened expression of tissue-residency marker genes (ITGAE, ITGA1, and CXCR6) along with elevated levels of IL17A, IL22, CCR6, and CCL20. The clonal expansion of Th17 Trm cells in CD was accompanied by enhanced transmural dynamic potential, as indicated by significantly higher migration scores. CD-prominent Th17 Trm cells displayed an increased interferon gamma (IFNγ)-related signature possibly linked with STAT1 activation, inducing chemokines (i.e., CXCL10, CXCL8, and CXCL9) in myeloid cells. Our findings underscored the elevated Th17 Trm cells throughout the small bowel in CD, contributing to disease pathogenesis through IFNγ induction and subsequent chemokine production in myeloid cells.

SARS-CoV-2-Spike T-cell response after receiving one or two Wuhan-Hu-1-based mRNA COVID-19 vaccine booster doses in elderly nursing home residents.

The effect of COVID-19 booster vaccination on SARS-CoV-2 T-cell mediated immune responses in elderly nursing home residents has not been explored in depth. Thirty-nine elderly nursing home residents (median age, 91 years) were included, all fully vaccinated with mRNA vaccines. The frequency of and the integrated mean fluorescence (iMFI) for peripheral blood SARS-CoV-2-Spike reactive IFN-γ-producing CD4+ or CD8+ T cells before and after the first (Pre-3D and Post-3D) and second (Pre-4D and Post-4D) vaccine booster doses was determined using flow cytometry for an intracellular staining method. 3D increased significantly (p = 0.01) the percentage of participants displaying detectable SARS-CoV-2-T-cell responses compared with pre-3D (97% vs. 74%). The magnitude of the increase was statistically significant for CD8+ T cells (p = 0.007) but not for CD4+ T cells (p = 0.77). A trend towards higher frequencies of peripheral blood SARS-CoV-2-CD8+ T cells was observed post-3D compared with pre-3D (p = 0.06). The percentage of participants with detectable SARS-S-CoV-2 CD4+ T-cell responses decreased post-4D (p = 0.035). Following 4D, a nonsignificant decrease in the frequencies of both T cell subsets was noticed (p = 0.94 for CD8+ T cells and p = 0.06 for CD4+ T cells). iMFI data mirrored that of T-cell frequencies. The kinetics of SARS-CoV-2 CD8+ and CD4+ T cells following receipt of 3D and 4D were comparable across SARS-CoV-2-experienced and -naïve participants and between individuals receiving a homologous or heterologous vaccine booster. 3D increased the percentage of elderly nursing home residents displaying detectable SARS-CoV-2 T-cell responses but had a marginal effect on T-cell frequencies. The impact of 4D on SARS-CoV-2 T-cell responses was negligible; whether this was due to suboptimal priming or rapid waning could not be ascertained.

Comparative analysis of T-cell immunity between Streptococcus agalactiae susceptible and resistant tilapia (Oreochromis niloticus).

Nile tilapia (Oreochromis niloticus) is one of the important economic fish species cultured worldwide. However, Streptococcus agalactiae has emerged as a significant bacterial threat, severely impacting the economy of tilapia industry. The immune response underlying the resistance of tilapia to S. agalactiae are not well understood, hindering the reasonable evaluation of breeding and the formulation of effective strategies. In this study, we investigated the differences in T-cell immunity between S. agalactiae-resistant and -susceptible tilapia. Compared with susceptible tilapia, resistant tilapia exhibited a higher percentage of T cells and BrdU+ T cells during infection, indicating a superior proliferative capacity. Whether infected or not, T cells from resistant fish demonstrated a greater ability to resist apoptosis. Additionally, T cell effector genes, including interleukin (IL)-2, interferon (IFN)-γ, perforin A, and granzyme B were expressed at higher levels in resistant tilapia after infection. Along with these T-cell immune responses, resistant fish showed more effective clearance of infection. Our study elucidates the T-cell immune responses in resistant tilapia, which may contribute to the high resistance of tilapia to S. agalactiae, and provide valuable theoretical references for the selection and evaluation of disease-resistant fish strains in the future.

Dynamics of cytomegalovirus-specific T-cell recovery in allogeneic hematopoietic cell transplant recipients using a commercially available flow cytometry assay: A pilot study.

BACKGROUND: Cytomegalovirus-specific T-cell-mediated immunity (CMV-CMI) protects from CMV infection in allogeneic hematopoietic cell transplantation (allo-HCT), but to date, there is no validated measure of CMV immunity for this population. METHODS: In this prospective, observational, pilot study, CMV T-cell responses were evaluated monthly and at onset of graft-versus-host disease (GVHD) or CMV infection in CMV-seropositive allo-HCT recipients using a commercial flow cytometry assay, the CMV inSIGHT T-Cell Immunity Panel (CMV-TCIP). The primary endpoint was the time to first positive CMV-TCIP, defined as percentage of interferon-γ-producing CD4+ or CD8+ CMV-specific T cells >0.2%. Letermovir was prescribed from day +10 to ≥100. RESULTS: Twenty-eight allo-HCT recipients were enrolled. The median time to first positive CMV-TCIP result was earlier for CD4+ (60 days [interquartile range, IQR 33‒148]) than for CD8+ T cells (96 days [IQR 33‒155]) and longer for haploidentical and mismatched transplant recipients (77 and 96 days, respectively) than for matched donors (45 and 33 days, respectively). CD4+ and CD8+ CMV-CMI recovery was sustained in 10/10 (100%) and 10/11 (91%) patients, respectively, without GVHD, whereas CD4+ and/or CD8+ CMV-CMI was lost in 4/6 and 2/6 patients, respectively, with GVHD requiring steroids. As a predictor of clinically significant CMV infection in patients with low-level CMV reactivation, the sensitivity and negative predictive value of CMV-TCIP were 90% and 87.5%, respectively, for CD4+ CMV-TCIP and 66.7% and 62.5%, respectively, for CD8+ CMV-TCIP. CONCLUSIONS: There was significant variability in time to CMV-CMI recovery post-HCT, with slower recovery after haploidentical and mismatched HCT. CD4+ CMV-CMI may protect against CS-CMVi, but immunity may be lost with GVHD diagnosis and treatment.

Tailoring cytomegalovirus prophylaxis based on T cell immunity panel assessment in kidney transplant patients at high risk of cytomegalovirus.

BACKGROUND: Valganciclovir prophylaxis against cytomegalovirus (CMV) is recommended for solid organ transplant recipients, but is associated with drawbacks, including expense and leukopenia. Our center adopted a strategy of serial assessment with a CMV-specific T cell immunity panel (CMV-TCIP) and cessation of valganciclovir prophylaxis upon demonstration of adequate CD4+ responses in kidney transplant patients at high risk of CMV disease. METHODS: We retrospectively reviewed adult recipients of a kidney or pancreas transplant between August 2019 and July 2021 undergoing serial CMV-TCIP monitoring. Included patients were considered high risk for CMV, defined by donor positive (D+)/recipient negative (R-) CMV IgG serostatus, or recipient positive (R+) patients who received induction with a lymphocyte-depleting agent. Prophylaxis was discontinued after a patient's first CMV-specific CD4+ T cell value of ≥0.20%. Risk of clinically significant CMV infection (csCMVi) in those who underwent early discontinuation of CMV prophylaxis and predictors of CMV T cell immunity were analyzed. RESULTS: Of 54 included patients, 22 stopped prophylaxis early due to CMV-specific CD4+ T cell immunity at a median of 4.7 (IQR: 3.8-5.4) months after transplant. No instances of csCMVi were observed in the 22 patients who had prophylaxis discontinued early, of whom 19/22 were CMV R+ and 3/22 were CMV D+/R-. Donor/recipient CMV serostatus was predictive of immunity (p <.001). CONCLUSION: Early discontinuation of valganciclovir prophylaxis in patients with CMV CD4+ T cellular immunity appears safe and potentially beneficial in this preliminary series, especially in R+ patients. Further study is warranted, given that truncated prophylaxis may yield patient-level benefits.