Characterization of humoral and cellular immunologic responses to an mRNA-based human cytomegalovirus vaccine from a phase 1 trial of healthy adults.

mRNA-1647 is an investigational mRNA-based vaccine against cytomegalovirus (CMV) that contains sequences encoding the CMV proteins glycoprotein B and pentamer. Humoral and cellular immune responses were evaluated in blood samples collected from healthy CMV-seropositive and CMV-seronegative adults who participated in a phase 1 trial of a three-dose series of mRNA-1647 (NCT03382405). Neutralizing antibody (nAb) titers against fibroblast and epithelial cell infection in sera from CMV-seronegative mRNA-1647 recipients were higher than those in sera from control CMV-seropositive samples and remained elevated up to 12 months after dose 3. nAb responses elicited by mRNA-1647 were comparable across 14 human CMV (HCMV) strains. Frequencies of antigen-specific memory B cells increased in CMV-seropositive and CMV-seronegative participants after each mRNA-1647 dose and remained elevated for up to 6 months after dose 3. mRNA-1647 elicited robust increases in frequencies and polyfunctionality of CD4+ T helper type 1 and effector CD8+ T cells in samples from CMV-seronegative and CMV-seropositive participants after stimulation with HCMV-specific peptides. The administration of three doses of mRNA-1647 to healthy adults elicited high nAb titers with wide-breadth, long-lasting memory B cells, and strong polyfunctional T-cell responses. These findings support further clinical development of the mRNA-1647 vaccine against CMV.IMPORTANCECytomegalovirus (CMV), a common virus that can infect people of all ages, may lead to serious health problems in unborn babies and those with a weakened immune system. Currently, there is no approved vaccine available to prevent CMV infection; however, the investigational messenger RNA (mRNA)-based CMV vaccine, mRNA-1647, is undergoing evaluation in clinical trials. The current analysis examined samples from a phase 1 trial of mRNA-1647 in healthy adults to better understand how the immune system reacts to vaccination. Three doses of mRNA-1647 produced a long-lasting immune response, thus supporting further investigation of the vaccine in the prevention of CMV infection.CLINICAL TRIALSRegistered at ClinicalTrials.gov (NCT03382405).

Common T-Cell-Receptor Motifs and Features in Patients with Cytomegalovirus (CMV)-Seronegative End-Stage Renal Disease Receiving a Peptide Vaccination against CMV.

After solid-organ transplantation, reactivation of the cytomegalovirus (CMV) is often observed in seronegative patients and associated with a high risk of disease and mortality. CMV-specific T cells can prevent CMV reactivation. In a phase 1 trial, CMV-seronegative patients with end-stage renal disease listed for kidney transplantation were subjected to CMV phosphoprotein 65 (CMVpp65) peptide vaccination and further investigated for T-cell responses. To this end, CMV-specific CD8+ T cells were characterized by bulk T-cell-receptor (TCR) repertoire sequencing and combined single-cell RNA and TCR sequencing. In patients mounting an immune response to the vaccine, a common SYE(N)E TCR motif known to bind CMVpp65 was detected. CMV-peptide-vaccination-responder patients had TCR features distinct from those of non-responders. In a non-responder patient, a monoclonal inflammatory T-cell response was detected upon CMV reactivation. The identification of vaccine-induced CMV-reactive TCRs motifs might facilitate the development of cellular therapies for patients wait-listed for kidney transplantation.

Therapeutic Vaccination of Hematopoietic Cell Transplantation Recipients Improves Protective CD8 T-Cell Immunotherapy of Cytomegalovirus Infection.

Reactivation of latent cytomegalovirus (CMV) endangers the therapeutic success of hematopoietic cell transplantation (HCT) in tumor patients due to cytopathogenic virus spread that leads to organ manifestations of CMV disease, to interstitial pneumonia in particular. In cases of virus variants that are refractory to standard antiviral pharmacotherapy, immunotherapy by adoptive cell transfer (ACT) of virus-specific CD8+ T cells is the last resort to bridge the "protection gap" between hematoablative conditioning for HCT and endogenous reconstitution of antiviral immunity. We have used the well-established mouse model of CD8+ T-cell immunotherapy by ACT in a setting of experimental HCT and murine CMV (mCMV) infection to pursue the concept of improving the efficacy of ACT by therapeutic vaccination (TherVac) post-HCT. TherVac aims at restimulation and expansion of limited numbers of transferred antiviral CD8+ T cells within the recipient. Syngeneic HCT was performed with C57BL/6 mice as donors and recipients. Recipients were infected with recombinant mCMV (mCMV-SIINFEKL) that expresses antigenic peptide SIINFEKL presented to CD8+ T cells by the MHC class-I molecule Kb. ACT was performed with transgenic OT-I CD8+ T cells expressing a T-cell receptor specific for SIINFEKL-Kb. Recombinant human CMV dense bodies (DB-SIINFEKL), engineered to contain SIINFEKL within tegument protein pUL83/pp65, served for vaccination. DBs were chosen as they represent non-infectious, enveloped, and thus fusion-competent subviral particles capable of activating dendritic cells and delivering antigens directly into the cytosol for processing and presentation in the MHC class-I pathway. One set of our experiments documents the power of vaccination with DBs in protecting the immunocompetent host against a challenge infection. A further set of experiments revealed a significant improvement of antiviral control in HCT recipients by combining ACT with TherVac. In both settings, the benefit from vaccination with DBs proved to be strictly epitope-specific. The capacity to protect was lost when DBs included the peptide sequence SIINFEKA lacking immunogenicity and antigenicity due to C-terminal residue point mutation L8A, which prevents efficient proteasomal peptide processing and binding to Kb. Our preclinical research data thus provide an argument for using pre-emptive TherVac to enhance antiviral protection by ACT in HCT recipients with diagnosed CMV reactivation.

Development of CMV-CD19 bi-specific CAR T cells with post-infusion in vivo boost using an anti-CMV vaccine.

Adoptive transfer of in vitro expanded, chimeric antigen receptor (CAR)-redirected CD19-specific T cells can induce dramatic disease regression in patients with leukemia and lymphomas. However, the full potential of this emerging modality is hampered in some cancer settings by a significant rate of therapeutic failure arising from the attenuated engraftment and persistence of CAR-redirected T cells, and tumor relapse following adoptive transfer. Here, we discuss an advanced strategy that facilitates post-infusion in vivo boosting of CAR T cells via CMV vaccination, to mediate durable remission of B cell malignancies by engrafting a CAR molecule onto a CMV-specific T cell. We also discuss a feasible and unique platform for the generation of the CMV-CD19CAR T cells for clinical application. This new approach would overcome multiple challenges in current CAR T cell technology including: short T cell persistence, limited duration of response, and inability to re-stimulate T cells after relapse or persistent disease.

A Live Olfactory Mouse Cytomegalovirus Vaccine, Attenuated for Systemic Spread, Protects against Superinfection.

Vaccination against the betaherpesvirus, human cytomegalovirus (HCMV) is a public health goal. However, HCMV has proved difficult to vaccinate against. Vaccination against single HCMV determinants has not worked, suggesting that immunity to a wider antigenic profile may be required. Live attenuated vaccines provide the best prospects for protection, but the question remains as to how to balance vaccine virulence with safety. Animal models of HCMV infection provide insights into identifying targets for virus attenuation and understanding how host immunity blocks natural, mucosal infection. Here, we evaluated the vaccine potential of a mouse cytomegalovirus (MCMV) vaccine deleted of a viral G protein-coupled receptor (GPCR), designated M33, that renders it attenuated for systemic spread. A single noninvasive olfactory ΔM33 MCMV vaccine replicated locally, but as a result of the loss of the M33 GPCR, it failed to spread systemically and was attenuated for latent infection. Vaccination did not prevent host entry of a superinfecting MCMV but spread from the mucosa was blocked. This approach to vaccine design may provide a viable alternative for a safe and effective betaherpesvirus vaccine. IMPORTANCE Human cytomegalovirus (HCMV) is the most common cause of congenital infection for which a vaccine is not yet available. Subunit vaccine candidates have failed to achieve licensure. A live HCMV vaccine may prove more efficacious, but it faces safety hurdles which include its propensity to persist and to establish latency. Understanding how pathogens infect guide rational vaccine design. However, HCMV infections are asymptomatic and thus difficult to capture. Animal models of experimental infection provide insight. Here, we investigated the vaccine potential of a mouse cytomegalovirus (MCMV) attenuated for systemic spread and latency. We used olfactory vaccination and virus challenge to mimic its natural acquisition. We provide proof of concept that a single olfactory MCMV that is deficient in systemic spread can protect against wild-type MCMV superinfection and dissemination. This approach of deleting functional counterpart genes in HCMV may provide safe and effective vaccination against congenital HCMV disease.

Dynamic Changes in Natural Killer Cell Subset Frequencies in the Absence of Cytomegalovirus Infection.

Individuals lacking functional natural killer (NK) cells suffer severe, recurrent infections with cytomegalovirus (CMV), highlighting the critical role of NK cells in antiviral defense. Therefore, ongoing attempts to develop an efficacious vaccine to prevent CMV infection should potentially aim to elicit NK-cell antiviral responses as an accessory to conventional T- and B-cell based approaches. In this regard, CMV infection provokes marked phenotypic and functional differentiation of the NK-cell compartment, including development of adaptive NK cells that exhibit enhanced antiviral activity. We examined longitudinal blood samples collected from 40 CMV-seronegative adolescents to ascertain whether a CMV glycoprotein B (gB) vaccine in the absence of CMV infection can stimulate differentiation or expansion of CMV-associated subsets of NK cells. Study participants uniformly lacked the CMV-dependent NKG2C+ subset of NK cells, suggesting that an adjuvanted CMV gB vaccine alone is an inadequate stimulus for sustained expansion of these cells. In contrast, we observed unexpected dynamic fluctuations in the frequency of NK cells lacking FcRγ, EAT-2, and SYK, which were independent of vaccination or CMV infection. Whereas, FcRγneg NK cells in CMV infection are reported to express increased levels of the maturation marker CD57, the FcRγneg NK cells observed in our CMV-negative vaccine cohort express less CD57 than their FcRγ+ counterparts. The FcRγneg NK cells in CMV-negative individuals were also functionally distinct from this subset in CMV infection, exhibiting comparable IFN-γ production and degranulation as FcRγ+ NK cells in response to cytokine or antibody-dependent stimuli. These results suggest that frequencies of some NK cell subsets may increase in response to unknown environmental or inflammatory cues distinct from that which occurs after CMV infection. Greater understanding of the nature of the signals driving CMV-independent accumulation of these subsets should permit development of mechanisms to facilitate vaccine-driven expansion of CMV-reactive NK cells.

Cytomegalovirus Infections after Hematopoietic Stem Cell Transplantation: Current Status and Future Immunotherapy.

Cytomegalovirus (CMV) infection after hematopoietic stem cell transplantation (HSCT) is one of the critical infectious complications related to host immune recovery. The spectrum of CMV infection is quite extensive, from asymptomatic CMV reactivation presenting mainly as CMV DNAemia to fatal CMV diseases involving gut, liver, lungs, or brain. In addition to organ involvement, CMV reactivation can exert indirect effects such as immunosuppression or graft failure that may result in the development of concurrent infectious complications. Currently, preemptive therapy, which is based on PCR-based monitoring of CMV from blood, is a mainstay enabling improvement in CMV-related outcomes. During the past decades, new antiviral drugs, clinical trials for prophylaxis in high-risk groups, and vaccines for preventing CMV infection have been introduced. In addition, data for immunologic monitoring and adoptive immunotherapy have also been accumulated. Here, we review the current status and recent updates in this field, with future perspectives including immunotherapy in HSCT recipients.

New vaccines and antiviral drugs for cytomegalovirus.

The natural history of cytomegalovirus (CMV) infection in transplant patients has been well established. This virus may originate from the recipient, the donor or both. When pre-transplant IgG antibodies in the recipient are taken into account, three types of infection are possible: primary, reactivation or reinfection. The risks of high viral load and end-organ disease are highest after primary infection and lowest after reactivation. Serial monitoring of patients by quantitative polymerase chain reaction for CMV DNA allows antiviral drugs to be deployed for pre-emptive therapy or an antiviral drug may be given prophylactically. Both of these strategies are effective, but pre-emptive therapy has the advantage that randomised allocation of a new drug or placebo given prophylactically may show a reduced need for pre-emptive valganciclovir. In this review, I will consider what has been learned from use of ganciclovir and valganciclovir and apply this information to clinical trials that have evaluated maribavir, brincidofovir and letermovir. In addition, pre-emptive therapy has the advantage of facilitating the discovery of vaccines against CMV using a pharmacodynamic approach. Briefly, patients awaiting transplantation are given vaccine or placebo pre-transplant. When they proceed to transplantation, various parameters of viral load can be compared to determine if the vaccine has an effect against CMV when compared to patients randomised to receive placebo. If there is evidence of control of CMV, this can be related to immune responses induced by the vaccine to define a correlate of protection. This review will summarise the published evidence available.

Vaccination against the human cytomegalovirus.

The human cytomegalovirus (HCMV) is the most important infectious cause of congenital abnormalities and also of infectious complications of transplantation. The biology of the infection is complex and acquired immunity does not always prevent reinfection. Nevertheless, vaccine development is far advanced, with numerous candidate vaccines being tested, both live and inactivated. This article summarizes the status of the candidate vaccines.

A neonatal mouse model of central nervous system infections caused by Coxsackievirus B5.

As one of the key members of the coxsackievirus B group, coxsackievirus B5 (CV-B5) can cause many central nervous system diseases, such as viral encephalitis, aseptic meningitis, and acute flaccid paralysis. Notably, epidemiological data indicate that outbreaks of CV-B5-associated central nervous system (CNS) diseases have been reported worldwide throughout history. In this study, which was conducted to promote CV-B5 vaccine and anti-virus drug research, a 3-day-old BALB/c mouse model was established using a CV-B5 clinical isolate (CV-B5/JS417) as the challenge strain. Mice challenged with CV-B5/JS417 exhibited a series of neural clinical symptoms and death with necrosis of neuronal cells in the cerebral cortex and the entire spinal cord, hindlimb muscles, and cardiomyocytes. The viral load of each tissue at various post-challenge time points suggested that CV-B5 replicated in the small intestine and was subsequently transmitted to various organs via viremia; the virus potentially entered the brain through the spinal axons, causing neuronal cell necrosis. In addition, this mouse model was used to evaluate the protective effect of a CV-B5 vaccine. The results indicated that both the inactivated CV-B5 vaccine and anti-CVB5 serum significantly protected mice from a lethal infection of CV-B5/JS417 by producing neutralizing antibodies. In summary, the first CV-B5 neonatal mouse model has been established and can sustain CNS infections in a manner similar to that observed in humans. This model will be a useful tool for studies on pathogenesis, vaccines, and anti-viral drug evaluations.

A fifty-year odyssey: prospects for a cytomegalovirus vaccine in transplant and congenital infection.

INTRODUCTION: It has been almost fifty years since the Towne strain was used by Plotkin and collaborators as the first vaccine candidate for cytomegalovirus (CMV). While that approach showed partial efficacy, there have been a multitude of challenges to improve on the promise of a CMV vaccine. Efforts have been dichotomized into a therapeutic vaccine for patients with CMV-infected allografts, either stem cells or solid organ, and a prophylactic vaccine for congenital infection. AREAS COVERED: This review will evaluate research prospects for a therapeutic vaccine for transplant recipients that recognizes CMV utilizing primarily T cell responses. Similarly, we will provide an extensive discussion on attempts to develop a vaccine to prevent the manifestations of congenital infection, based on eliciting a humoral anti-CMV protective response. The review will also describe newer developments that have upended the efforts toward such a vaccine through the discovery of a second pathway of CMV infection that utilizes an alternative receptor for entry using a series of antigens that have been determined to be important for prevention of infection. EXPERT COMMENTARY: There is a concerted effort to unify separate therapeutic and prophylactic vaccine strategies into a single delivery agent that would be effective for both transplant-related and congenital infection.

Multiantigenic Modified Vaccinia Virus Ankara Vaccine Vectors To Elicit Potent Humoral and Cellular Immune Reponses against Human Cytomegalovirus in Mice.

As human cytomegalovirus (HCMV) is a common cause of disease in newborns and transplant recipients, developing an HCMV vaccine is considered a major public health priority. Yet an HCMV vaccine candidate remains elusive. Although the precise HCMV immune correlates of protection are unclear, both humoral and cellular immune responses have been implicated in protection against HCMV infection and disease. Here we describe a vaccine approach based on the well-characterized modified vaccinia virus Ankara (MVA) vector to stimulate robust HCMV humoral and cellular immune responses by an antigen combination composed of the envelope pentamer complex (PC), glycoprotein B (gB), and phosphoprotein 65 (pp65). We show that in mice, multiantigenic MVA vaccine vectors simultaneously expressing all five PC subunits, gB, and pp65 elicit potent complement-independent and complement-dependent HCMV neutralizing antibodies as well as mouse and human MHC-restricted, polyfunctional T cell responses by the individual antigens. In addition, we demonstrate that the PC/gB antigen combination of these multiantigenic MVA vectors can enhance the stimulation of humoral immune responses that mediate in vitro neutralization of different HCMV strains and antibody-dependent cellular cytotoxicity. These results support the use of MVA to develop a multiantigenic vaccine candidate for controlling HCMV infection and disease in different target populations, such as pregnant women and transplant recipients.IMPORTANCE The development of a human cytomegalovirus (HCMV) vaccine to prevent congenital disease and transplantation-related complications is an unmet medical need. While many HCMV vaccine candidates have been developed, partial success in preventing or controlling HCMV infection in women of childbearing age and transplant recipients has been observed with an approach based on envelope glycoprotein B (gB). We introduce a novel vaccine strategy based on the clinically deployable modified vaccinia virus Ankara (MVA) vaccine vector to elicit potent humoral and cellular immune responses by multiple immunodominant HCMV antigens, including gB, phosphoprotein 65, and all five subunits of the pentamer complex. These findings could contribute to development of a multiantigenic vaccine strategy that may afford more protection against HCMV infection and disease than a vaccine approach employing solely gB.

Vaccine Development for Cytomegalovirus.

The development of a cytomegalovirus (CMV) vaccine has become a top priority due to its potential cost-effectiveness and associated public health benefits. However, there are a number of challenges facing vaccine development including the following: (1) CMV has many mechanisms for evading immune responses , and natural immunity is not perfect, (2) the immune correlates for protection are unclear, (3) a narrow range of CMV hosts limits the value of animal models, and (4) the placenta is a specialized organ formed transiently and its immunological status changes with time. In spite of these limitations, several types of CMV vaccine candidate, including live-attenuated, DISC , subunit, DNA, vectored, and peptide vaccines, have been developed or are currently under development. The recognition of the pentameric complex as the major neutralization target and identification of various strategies to block viral immune response evasion mechanisms have opened new avenues to CMV vaccine development. Here, we discuss the immune correlates for protection, the characteristics of the various vaccine candidates and their clinical trials, and the relevant animal models.

Exploiting 2A peptides to elicit potent neutralizing antibodies by a multi-subunit herpesvirus glycoprotein complex.

Neutralizing antibodies (NAb) interfering with glycoprotein complex-mediated virus entry into host cells are thought to contribute to the protection against herpesvirus infection. However, using herpesvirus glycoprotein complexes as vaccine antigens can be complicated by the necessity of expressing multiple subunits simultaneously to allow efficient complex assembly and formation of conformational NAb epitopes. By using a novel bacterial artificial chromosome (BAC) clone of the clinically deployable Modified Vaccinia Ankara (MVA) vector and exploiting ribosomal skipping mediated by 2A peptides, MVA vectors were generated that expressed self-processing subunits of the human cytomegalovirus (HCMV) pentamer complex (PC) composed of gH, gL, UL128, UL130, and UL131A. These MVA vectors expressed 2A-linked HCMV PC subunits that were efficiently cleaved and transported to the cell surface as protein complexes forming conformational neutralizing epitopes. In addition, vaccination of mice by only two immunizations with these MVA vectors resulted in potent HCMV NAb responses that remained stable over a period of at least six months. This method of eliciting NAb by 2A-linked, self-processing HCMV PC subunits could contribute to develop a HCMV vaccine candidate and may serve as a template to facilitate the development of subunit vaccine strategies against other herpesviruses.

Progress toward Development of a Vaccine against Congenital Cytomegalovirus Infection.

A vaccine against congenital human cytomegalovirus (CMV) infection is a major public health priority. Congenital CMV causes substantial long-term morbidity, particularly sensorineural hearing loss (SNHL), in newborns, and the public health impact of this infection on maternal and child health is underrecognized. Although progress toward development of a vaccine has been limited by an incomplete understanding of the correlates of protective immunity for the fetus, knowledge about some of the key components of the maternal immune response necessary for preventing transplacental transmission is accumulating. Moreover, although there have been concerns raised about observations indicating that maternal seropositivity does not fully prevent recurrent maternal CMV infections during pregnancy, it is becoming increasing clear that preconception immunity does confer some measure of protection against both CMV transmission and CMV disease (if transmission occurs) in the newborn infant. Although the immunity to CMV conferred by both infection and vaccination is imperfect, there are encouraging data emerging from clinical trials demonstrating the immunogenicity and potential efficacy of candidate CMV vaccines. In the face of the knowledge that between 20,000 and 30,000 infants are born with congenital CMV in the United States every year, there is an urgent and compelling need to accelerate the pace of vaccine trials. In this minireview, we summarize the status of CMV vaccines in clinical trials and provide a perspective on what would be required for a CMV immunization program to become incorporated into clinical practice.

Optimized enzyme-linked immunosorbent assay for detecting cytomegalovirus infections during clinical trials of recombinant vaccines.

BACKGROUND: In clinical trials of cytomegalovirus (CMV) glycoprotein B (gB) vaccines, CMV infection is detected by first depleting serum of anti-gB antibodies and then measuring anti-CMV antibodies with a commercially available enzyme-linked immunosorbent assay (ELISA) kit, with confirmation of positive findings by immunoblot. OBJECTIVES: Identification of CMV immunoantigens for the development of an ELISA that detects specifically CMV infection in clinical samples from individuals immunized with gB vaccines. STUDY DESIGN: Sensitivity and specificity of ELISAs using antigenic regions of CMV proteins UL83/pp65, UL99/pp28, UL44/pp52, UL80a/pp38, UL57, and UL32/pp150 were measured. RESULTS: An IgG ELISA using a UL32/pp150 [862-1048] capture peptide was the most specific (93.7%) and sensitive (96.4%) for detecting CMV-specific antibodies in sera. The ELISA successfully detected CMV-specific antibodies in 22 of 22 sera of subjects who had been vaccinated with a gB vaccine but who had later been infected with CMV. The ELISA was linear over a wide range of CMV concentrations (57-16,814 ELISA units/mL) and was reproducible as indicated by a 5% intra-day and 7% inter-day coefficients of variation. The signal was specifically competed by UL32/pp150 [862-1048] peptide but not by CMV-gB or herpes simplex virus 2 glycoprotein D. Lipid and hemoglobin matrix did not interfere with the assay. CONCLUSION: The UL32/pp150 [862-1048] IgG ELISA can be used for the sensitive and specific detection of CMV infection in gB-vaccinated individuals.

Intratumoral infection by CMV may change the tumor environment by directly interacting with tumor-associated macrophages to promote cancer immunity.

Cytomegalovirus (CMV) is a herpesvirus that induces an extremely robust and sustained immune response. For this reason, CMV has been proposed as a vaccine vector to promote immunity to both pathogens and cancer. However, exploration of CMV as a vaccine vector is at an early stage and there are many questions. Using a mouse melanoma model, we recently found that a CMV-based vaccine induced large populations of melanoma-specific T cells, but was not effective at slowing tumor growth unless it was injected directly into the tumor. These surprising results have led us to hypothesize that CMV may be adept at modulating the tumor micro-environment through its infection of macrophages. Importantly, injection of CMV into the growing tumor synergized with blockade of the PD-1 checkpoint to clear well-established tumors. Here, we discuss our results in the context of CMV-based vaccines for pathogens and cancer.

How does cytomegalovirus factor into diseases of aging and vaccine responses, and by what mechanisms?

Cytomegalovirus (CMV) is an important pathogen for both clinical and population settings. There is a growing body of research implicating CMV in multiple health outcomes across the life course. At the same time, there is mounting evidence that individuals living in poverty are more likely to be exposed to CMV and more likely to experience many of the chronic conditions for which CMV has been implicated. Further research on the causal role of CMV for health and well-being is needed. However, the strong evidence implicating CMV in type 2 diabetes, autoimmunity, cancer, cardiovascular disease, vaccination, and age-related alterations in immune function warrants clinical and public health action. This imperative is even higher among individuals living in socioeconomically disadvantaged settings and those exposed to high levels of chronic psychosocial stress.