Human cytomegalovirus glycoprotein B is required for virus entry and cell-to-cell spread but not for virion attachment, assembly, or egress

Overview of Cytomegalovirus Ocular Diseases: Retinitis, Corneal Endotheliitis, and Iridocyclitis

Cytomegalovirus (CMV) infection is a significant clinical concern in newborns, immunocompromised patients with acquired immunodeficiency syndrome (AIDS), and patients undergoing immunosuppressive therapy or chemotherapy. CMV infection affects many organs, such as the lungs, digestive organs, the central nerve system, and eyes. In addition, CMV infection sometimes occurs in immunocompetent individuals. CMV ocular diseases includes retinitis, corneal endotheliitis, and iridocyclitis. CMV retinitis often develops in infected newborns and immunocompromised patients. CMV corneal endotheliitis and iridocyclitis sometimes develop in immunocompetent individuals. Systemic infections and CMV ocular diseases often require systemic treatment in addition to topical treatment.

Evaluation of Bispecific T-Cell Engagers Targeting Murine Cytomegalovirus

Human cytomegalovirus is a ubiquitous herpesvirus that, while latent in most individuals, poses a great risk to immunocompromised patients. In contrast to directly acting traditional antiviral drugs, such as ganciclovir, we aim to emulate a physiological infection control using T cells. For this, we constructed several bispecific T-cell engager (BiTE) constructs targeting different viral glycoproteins of the murine cytomegalovirus and evaluated them in vitro for their efficacy. To isolate the target specific effect without viral immune evasion, we established stable reporter cell lines expressing the viral target glycoprotein B, and the glycoprotein complexes gN-gM and gH-gL, as well as nano-luciferase (nLuc). First, we evaluated binding capacities using flow cytometry and established killing assays, measuring nLuc-release upon cell lysis. All BiTE constructs proved to be functional mediators for T-cell recruitment and will allow a proof of concept for this treatment option. This might pave the way for strikingly safer immunosuppression in vulnerable patient groups.

A Decade-Long Cohort Analysis of Human Cytomegalovirus (HCMV)-Induced Early and Late Renal Rejection in Post-Transplant Patients in the Eastern Indian Population

Background: HCMV causes severe clinical complications in transplant recipients and may lead to graft rejection. Successful renal transplantation heavily relies on the early prevention and diagnosis of CMV infections, followed by prompt prophylactic treatment before transplantation. Despite the majority of renal rejection cases with acute HCMV infections being asymptomatic and occurring one to two years later, the objective of this research was to comprehend the effect of late HCMV infection on renal rejection by examining specific clinical parameters in the Eastern Indian cohort. Method: In this study, 240 patients were studied for five years following transplantation, and their data were collected from the local metropolitan hospital in Eastern India. Both HCMV-positive and -negative post-transplant patients were investigated using the clinical parameters and viral loads for latent infection. Results: Within the studied population, 79 post-transplant patients were found to be HCMV positive. Among them, 13 (16.45%) patients suffered from renal rejection within less than 2 yrs. of transplantation (early rejection) and 22 (27.84%) patients suffered from renal rejection after 2 yrs. from the operation date (late rejection). Assessment of clinical parameters with respect to HCMV infection revealed that in early rejection cases, fever (p-0.035) and urinary tract infection (p-0.017) were prominent, but in late rejection, hematuria (p-0.032), diabetes (p-0.005), and creatinine level changes (p < 0.001) were significant along with urinary tract infection (p-0.047). Conclusions: This study provides valuable insights into monitoring latent CMV infections and highlights the understanding of reducing renal rejection rates and the need for further research in this field.

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).

CHO cells for virus-like particle and subunit vaccine manufacturing

Chinese Hamster Ovary (CHO) cells, employed primarily for manufacturing monoclonal antibodies and other recombinant protein (r-protein) therapeutics, are emerging as a promising host for vaccine antigen production. This is exemplified by the recently approved CHO cell-derived subunit vaccines (SUV) against respiratory syncytial virus (RSV) and varicella-zoster virus (VZV), as well as the enveloped virus-like particle (eVLP) vaccine against hepatitis B virus (HBV). Here, we summarize the design, production, and immunogenicity features of these vaccine and review the most recent progress of other CHO-derived vaccines in pre-clinical and clinical development. We also discuss the challenges associated with vaccine production in CHO cells, with a focus on ensuring viral clearance for eVLP products.

Human induced pluripotent stem cells are resistant to human cytomegalovirus infection primarily at the attachment level due to the reduced expression of cell-surface heparan sulfate

Cytomegalovirus (CMV), a type of herpes virus, is the predominant cause of congenital anomalies due to intrauterine infections in humans. Adverse outcomes related to intrauterine infections with human cytomegalovirus (HCMV) vary widely, depending on factors such as fetal infection timing, infection route, and viral virulence. The precise mechanism underlying HCMV susceptibility remains unclear. In this study, we compared the susceptibility of neonatal human dermal fibroblast cells (NHDFCs) and human induced pluripotent stem cells (hiPSCs) derived from NHDFCs, which are genetically identical to HCMV, using immunostaining, microarray, in situ hybridization, quantitative PCR, and scanning electron microscopy. These cells were previously used to compare CMV susceptibility, but the underlying mechanisms were not fully elucidated. HCMV susceptibility of hiPSCs was significantly lower in the earliest phase. No shared gene ontologies were observed immediately post-infection between the two cell types using microarray analysis. Early-stage expression of HCMV antigens and the HCMV genome was minimal in immunostaining and in in situ hybridization in hiPSCs. This strongly suggests that HCMV does not readily bind to hiPSC surfaces. Scanning electron microscopy performed using the NanoSuit method confirmed the scarcity of HCMV particles on hiPSC surfaces. The zeta potential and charge mapping of the charged surface in NHDFCs and hiPSCs exhibited minimal differences when assessed using zeta potential analyzer and scanning ion conductance microscopy; however, the expression of heparan sulfate (HS) was significantly lower in hiPSCs compared with that in NHDFCs. Thus, HS expression could be a primary determinant of HCMV resistance in hiPSCs at the attachment level.

IMPORTANCE

Numerous factors such as attachment, virus particle entry, transcription, and virus particle egress can affect viral susceptibility. Since 1984, pluripotent cells are known to be CMV resistant; however, the exact mechanism underlying this resistance remains elusive. Some researchers suggest inhibition in the initial phase of HCMV binding, while others have suggested the possibility of a sufficient amount of HCMV entering the cells to establish latency. This study demonstrates that HCMV particles rarely attach to the surfaces of hiPSCs. This is not due to limitations in the electrostatic interactions between the surface of hiPSCs and HCMV particles, but due to HS expression. Therefore, HS expression should be recognized as a key factor in determining the susceptibility of HCMV in congenital infection in vitro and in vivo. In the future, drugs targeting HS may become crucial for the treatment of congenital CMV infections. Thus, further research in this area is warranted.

Human Cytomegalovirus mRNA-1647 Vaccine Candidate Elicits Potent and Broad Neutralization and Higher Antibody-Dependent Cellular Cytotoxicity Responses Than the gB/MF59 Vaccine

BACKGROUND

MF59-adjuvanted gB subunit (gB/MF59) vaccine demonstrated approximately 50% efficacy against human cytomegalovirus (HCMV) acquisition in multiple clinical trials, suggesting that efforts to improve this vaccine design might yield a vaccine suitable for licensure.

METHODS

A messenger RNA (mRNA)-based vaccine candidate encoding HCMV gB and pentameric complex (PC), mRNA-1647, is currently in late-stage efficacy trials. However, its immunogenicity has not been compared to the partially effective gB/MF59 vaccine. We assessed neutralizing and Fc-mediated immunoglobulin G (IgG) effector antibody responses induced by mRNA-1647 in both HCMV-seropositive and -seronegative vaccinees from a first-in-human clinical trial through 1 year following third vaccination using a systems serology approach. Furthermore, we compared peak anti-gB antibody responses in seronegative mRNA-1647 vaccinees to that of seronegative gB/MF59 vaccine recipients.

RESULTS

mRNA-1647 vaccination elicited and boosted HCMV-specific IgG responses in seronegative and seropositive vaccinees, respectively, including neutralizing and Fc-mediated effector antibody responses. gB-specific IgG responses were lower than PC-specific IgG responses. gB-specific IgG and antibody-dependent cellular phagocytosis responses were lower than those elicited by gB/MF59. However, mRNA-1647 elicited higher neutralization and antibody-dependent cellular cytotoxicity (ADCC) responses.

CONCLUSIONS

Overall, mRNA-1647 vaccination induced polyfunctional and durable HCMV-specific antibody responses, with lower gB-specific IgG responses but higher neutralization and ADCC responses compared to the gB/MF59 vaccine.

CLINICAL TRIALS REGISTRATION

NCT03382405 (mRNA-1647) and NCT00133497 (gB/MF59).

Progression of retinal choroidal neovascularization by latent human cytomegalovirus infection and immunological signaling among neonatal patients admitted to tertiary care hospital

Choroidal neovascularization (CNV) is a serious condition that affects the retina, causing partial or complete blindness in people of different ages. While CNV is a common occurrence in various chorioretinopathies, research on its occurrence in neonates is limited. Human cytomegalovirus (HCMV) is a significant health threat to neonates, with a strong association with retinal angiogenesis. However, there has been limited investigation into HCMV-associated CNV progression. In this article, we extensively studied the expression of different inflammatory cytokines and chemokines during latent HCMV-associated retinal neovascularization. Our research found that HCMV-induced CNV progression was significantly prominent in the presence of AT2R-dependent angiogenesis (p < 0.001), whereas in the absence of HCMV, AT1R-dependent CCL-5-mediated angiogenesis was documented. We also observed significant increases in CCL-19, CCL-21 chemokine responses, followed by CCR-7 chemokine receptor activation (p < 0.001) in HCMV-induced CNV patients compared to HCMV non-induced CNV groups. Furthermore, significant changes in predictive chemokine markers of HCMV-induced CNV were positively correlated with HCMV viremia. These immunological alterations ultimately lead to the switching of NFκB canonical and noncanonical pathways, respectively, in HCMV-induced neonatal CNV and HCMV non-induced CNV. This clinical observation presents a novel hypothesis that ocular HCMV latency poses a noteworthy risk factor for the progression of retinal neovascularization through a distinctive immunological signaling pathway. The current study represents the first of its kind to report on this association, which may have significant implications for the clinical management of patients with ocular HCMV.

CAR Immunotherapy for the treatment of infectious diseases: a systematic review

Immunotherapy treatments aim to modulate the host's immune response to either mitigate it in inflammatory/autoimmune disease or enhance it against infection or cancer. Among different immunotherapies reaching clinical application during the last years, chimeric antigen receptor (CAR) immunotherapy has emerged as an effective treatment for cancer where different CAR T cells have already been approved. Yet their use against infectious diseases is an area still relatively poorly explored, albeit with tremendous potential for research and clinical application. Infectious diseases represent a global health challenge, with the escalating threat of antimicrobial resistance underscoring the need for alternative therapeutic approaches. This review aims to systematically evaluate the current applications of CAR immunotherapy in infectious diseases and discuss its potential for future applications. Notably, CAR cell therapies, initially developed for cancer treatment, are gaining recognition as potential remedies for infectious diseases. The review sheds light on significant progress in CAR T cell therapy directed at viral and opportunistic fungal infections.

Human virome profiling identified CMV as the major viral driver of a high accumulation of senescent CD8+ T cells in patients with advanced NSCLC

Circulating senescent CD8+ T (T8sen) cells are characterized by a lack of proliferative capacities but retain cytotoxic activity and have been associated to resistance to immunotherapy in patients with advanced non-small cell lung cancer (aNSCLC). We aimed to better characterize T8sen and to determine which factors were associated with their accumulation in patients with aNSCLC. Circulating T8sen cells were characterized by a higher expression of SA-βgal and the transcription factor T-bet, confirming their senescent status. Using whole virome profiling, cytomegalovirus (CMV) was the only virus associated with T8sen. CMV was necessary but not sufficient to explain high accumulation of T8sen (T8senhigh status). In CMV+ patients, the proportion of T8sen cells increased with cancer progression. Last, CMV-induced T8senhigh phenotype but not CMV seropositivity itself was associated with worse progression-free and overall survival in patients treated with anti-PD-(L)1 therapy but not with chemotherapy. Overall, CMV is the unique viral driver of T8sen-driven resistance to anti-PD-(L)1 antibodies in patients with aNSCLC.

Insights into the Transcriptome of Human Cytomegalovirus: A Comprehensive Review

Human cytomegalovirus (HCMV) is a widespread pathogen that poses significant risks to immunocompromised individuals. Its genome spans over 230 kbp and potentially encodes over 200 open-reading frames. The HCMV transcriptome consists of various types of RNAs, including messenger RNAs (mRNAs), long non-coding RNAs (lncRNAs), circular RNAs (circRNAs), and microRNAs (miRNAs), with emerging insights into their biological functions. HCMV mRNAs are involved in crucial viral processes, such as viral replication, transcription, and translation regulation, as well as immune modulation and other effects on host cells. Additionally, four lncRNAs (RNA1.2, RNA2.7, RNA4.9, and RNA5.0) have been identified in HCMV, which play important roles in lytic replication like bypassing acute antiviral responses, promoting cell movement and viral spread, and maintaining HCMV latency. CircRNAs have gained attention for their important and diverse biological functions, including association with different diseases, acting as microRNA sponges, regulating parental gene expression, and serving as translation templates. Remarkably, HCMV encodes miRNAs which play critical roles in silencing human genes and other functions. This review gives an overview of human cytomegalovirus and current research on the HCMV transcriptome during lytic and latent infection.

A temperature-dependent virus-binding assay reveals the presence of neutralizing antibodies in human cytomegalovirus gB vaccine recipients' sera

Human cytomegalovirus (HCMV) remains an important cause of mortality in immune-compromised transplant patients and following congenital infection. Such is the burden, an effective vaccine strategy is considered to be of the highest priority. The most successful vaccines to date have focused on generating immune responses against glycoprotein B (gB) - a protein essential for HCMV fusion and entry. We have previously reported that an important component of the humoral immune response elicited by gB/MF59 vaccination of patients awaiting transplant is the induction of non-neutralizing antibodies that target cell-associated virus with little evidence of concomitant classical neutralizing antibodies. Here we report that a modified neutralization assay that promotes prolonged binding of HCMV to the cell surface reveals the presence of neutralizing antibodies in sera taken from gB-vaccinated patients that cannot be detected using standard assays. We go on to show that this is not a general feature of gB-neutralizing antibodies, suggesting that specific antibody responses induced by vaccination could be important. Although we can find no evidence that these neutralizing antibody responses are a correlate of protection in vivo in transplant recipients their identification demonstrates the utility of the approach in identifying these responses. We hypothesize that further characterization has the potential to aid the identification of functions within gB that are important during the entry process and could potentially improve future vaccine strategies directed against gB if they prove to be effective against HCMV at higher concentrations.

The cytomegalovirus gB/MF59 vaccine candidate induces antibodies against an antigenic domain controlling cell-to-cell spread

Vaccination against human cytomegalovirus (CMV) infection remains high priority. A recombinant form of a protein essential for CMV entry, glycoprotein B (gB), demonstrated partial protection in a clinical trial (NCT00299260) when delivered with the MF59 adjuvant. Although the antibody titre against gB correlated with protection poor neutralising responses against the 5 known antigenic domains (AD) of gB were evident. Here, we show that vaccination of CMV seronegative patients induces an antibody response against a region of gB we term AD-6. Responses to the polypeptide AD-6 are detected in >70% of vaccine recipients yet in <5% of naturally infected people. An AD-6 antibody binds to gB and to infected cells but not the virion directly. Consistent with this, the AD-6 antibody is non-neutralising but, instead, prevents cell-cell spread of CMV in vitro. The discovery of AD-6 responses has the potential to explain part of the protection mediated by gB vaccines against CMV following transplantation.

Distribution of CMV envelope glycoprotein B, H and N genotypes in infants with congenital cytomegalovirus symptomatic infection

Background

Cytomegalovirus (CMV) is the leading cause of congenital infections worldwide and contributes to long-term sequelae in neonates and children. CMV envelope glycoproteins play a vital role in virus entry and cell fusion. The association between CMV polymorphisms and clinical outcomes remains controversial. The present study aims to demonstrate the distribution of glycoprotein B (gB), H (gH) and N (gN) genotypes in congenitally CMV (cCMV) infected symptomatic infants and attempts to figure out the association between viral glycoprotein genotypes and clinical outcomes.

Methods

Genotyping of gB, gH and gN was performed in 42 cCMV symptomatic infants and 149 infants with postnatal CMV (pCMV) infection in Children's hospital of Fudan university. Nested PCR, gene sequencing and phylogenetic analyses were used to identify the genotypes.

Results

Our study demonstrated that: 1. The CMV gB1, gH1 and gN1 were the predominant genotypes among symptomatic cCMV infected infants, while gB1, gH1 and gN3a were more prevalent in pCMV group. gH1 genotype has a significant association with symptomatic cCMV infection (p = 0.006). 2. No significant correlation was found between CMV genotypes and hearing impairment. However, gH1 was more prevalent among cCMV infected infants with moderate/severe hearing loss although without statistical difference (p = 0.130). 3. gB3 was more prevalent among infants with skin petechiae (p = 0.049) and found to be associated with an increased risk of skin petechiae (OR = 6.563). The gN4a subtype was significantly associated with chorioretinitis due to cCMV infection (p = 0.007). 4. Urine viral loads were not significantly associated with different genotypes or hearing impairment among symptomatic cCMV infected infants.

Conclusions

Our findings demonstrated the overall distribution of gB, gH and gN genotypes in infants with symptomatic cCMV infection in Shanghai for the first time. The findings in our study may suggest a possible association between gH1 genotype and early infancy hearing loss. gB3 genotype was associated with a 6.5-fold increased risk of petechiae while gN4a strongly correlated with chorioretinitis due to cCMV infection. No significant correlation was found between urine viral loads and CMV genotypes or hearing impairment in cCMV infected infants.

The human cytomegalovirus decathlon: Ten critical replication events provide opportunities for restriction

Human cytomegalovirus (HCMV) is a ubiquitous human pathogen that can cause severe disease in immunocompromised individuals, transplant recipients, and to the developing foetus during pregnancy. There is no protective vaccine currently available, and with only a limited number of antiviral drug options, resistant strains are constantly emerging. Successful completion of HCMV replication is an elegant feat from a molecular perspective, with both host and viral processes required at various stages. Remarkably, HCMV and other herpesviruses have protracted replication cycles, large genomes, complex virion structure and complicated nuclear and cytoplasmic replication events. In this review, we outline the 10 essential stages the virus must navigate to successfully complete replication. As each individual event along the replication continuum poses as a potential barrier for restriction, these essential checkpoints represent potential targets for antiviral development.

Identification and characterization of human cytomegalovirus-encoded circular RNAs

Circular RNA (circRNA) exists extensively and plays essential roles in serving as microRNA (miRNA) or protein sponges and protein scaffolding in many organisms. However, the profiles and potential functions of the virus-encoded circRNA, including human cytomegalovirus (HCMV)-encoded circular RNAs, remain unclear. In the present study, HCMV-encoded circRNAs profile in human embryonic lung fibroblasts (HELF) with lytic infection was investigated using RNA deep sequencing and bioinformatics analysis. In total, 629 HCMV-encoded circRNAs were identified with various expression patterns in our results. The full sequences and alternative splicings of circUS12, circUL55, and circUL89 were verified by reverse transcriptase-PCR (RT-PCR) with divergent primers followed and Sanger sequencing. Transcription of circUL89 was validated by Northern blot. The HCMV-encoded circRNA-miRNA network analyses revealed the potential function of HCMV-encoded circRNAs during HCMV infection in HELFs. Collectively, HCMV infection deduced abundant HCMV-associated circRNAs during infection, and the HCMV-encoded circRNAs might play important roles in benefiting HCMV infection.

Induction of Filopodia During Cytomegalovirus Entry Into Human Iris Stromal Cells

Many viruses exploit thin projections of filopodia for cell entry and cell-to-cell spread. Using primary cultures of human iris stromal (HIS) cells derived from human eye donors, we report a significant increase in filopodia formation during human cytomegalovirus (HCMV) infection. Using confocal microscopy, we observed a large number of virions being frequently associated along the filopodia prior to cell infection. Depolymerization of actin filaments resulted in a significant inhibition of HCMV entry into HIS cell. Our results further revealed that the transient expression of HCMV envelope glycoprotein B (gB) triggers the induction of the filopodial system. Since gB is known to bind the diverse chains of heparan sulfate (HS), a comparative study was performed to evaluate the gB-mediated filopodial induction in cells expressing either wild-type HS and/or 3-O sulfated HS (3-OS HS). We found that cells co-expressing HCMV gB together with the 3-O sulfotranseferase-3 (3-OST-3) enzyme had a much higher and robust filopodia induction compared to cells co-expressing gB with wild-type HS. The above results were further verified by pre-treating HIS cells with anti-3-OS HS (G2) peptide and/or heparinase-I before challenging with HCMV infection, which resulted in a significant loss in the filopodial counts as well as decreased viral infectivity. Taken together, our findings highlight that HCMV entry into HIS cells actively modulates the actin cytoskeleton via coordinated actions possibly between gB and the 3-OS HS receptor to influence viral infectivity.

Structural basis for HCMV Pentamer recognition by neuropilin 2 and neutralizing antibodies

Human cytomegalovirus (HCMV) encodes multiple surface glycoprotein complexes to infect a variety of cell types. The HCMV Pentamer, composed of gH, gL, UL128, UL130, and UL131A, enhances entry into epithelial, endothelial, and myeloid cells by interacting with the cell surface receptor neuropilin 2 (NRP2). Despite the critical nature of this interaction, the molecular determinants that govern NRP2 recognition remain unclear. Here, we describe the cryo-EM structure of NRP2 bound to Pentamer. The high-affinity interaction between these proteins is calcium dependent and differs from the canonical carboxyl-terminal arginine (CendR) binding that NRP2 typically uses. We also determine the structures of four neutralizing human antibodies bound to the HCMV Pentamer to define susceptible epitopes. Two of these antibodies compete with NRP2 binding, but the two most potent antibodies recognize a previously unidentified epitope that does not overlap the NRP2-binding site. Collectively, these findings provide a structural basis for HCMV tropism and antibody-mediated neutralization.

Virus-host protein interactions as footprints of human cytomegalovirus replication

Human cytomegalovirus (HCMV) is a pervasive β-herpesvirus that causes lifelong infection. The lytic replication cycle of HCMV is characterized by global organelle remodeling and dynamic virus-host interactions, both of which are necessary for productive HCMV replication. With the advent of new technologies for investigating protein-protein and protein-nucleic acid interactions, numerous critical interfaces between HCMV and host cells have been identified. Here, we review temporal and spatial virus-host interactions that support different stages of the HCMV replication cycle. Understanding how HCMV interacts with host cells during entry, replication, and assembly, as well as how it interfaces with host cell metabolism and immune responses promises to illuminate processes that underlie the biology of infection and the resulting pathologies.

Pharmacokinetics, Safety, and Tolerability of NPC-21, an Anti-Cytomegalovirus Monoclonal Antibody, in Healthy Japanese and White Adult Men: A Randomized, Placebo-Controlled, First-in-Human Phase 1 Study

NPC-21 (EV2038) is a fully human monoclonal antibody that targets the antigenic domain 1 of glycoprotein B on the human cytomegalovirus (hCMV) envelope. NPC-21 has been shown to have broadly neutralizing activity and to inhibit cell-to-cell transmission of hCMV in preclinical studies. It is currently in development for the prophylactic or preemptive treatment of hCMV in patients receiving a solid-organ transplant or hematopoietic stem cell transplant. A first-in-human phase 1 study was conducted to assess the pharmacokinetics, safety, and tolerability of NPC-21 in healthy adult men. Forty participants (Japanese, n = 32; White, n = 8) were randomly assigned to receive a single intravenous dose of NPC-21 1, 3, 10, or 20 mg/kg or placebo. Six Japanese participants were included in each dose group and six White participants received a 10-mg/kg dose. The placebo group included 8 Japanese participants and 2 White participants. All 40 participants completed the study. Serum concentration, maximum serum concentration, area under the plasma concentration-time curve from time 0 to the last measurable concentration, and area under the plasma concentration-time curve from time 0 to infinity increased dose dependently; dose proportionality was linear. NPC-21 demonstrated a biphasic elimination pattern, with an estimated half-life between 612 and 790 hours. NPC-21 was safe and well tolerated up to 20 mg/kg. All adverse events were mild, and none led to treatment discontinuation or were considered related to the study drug. There were no differences in pharmacokinetics or safety between Japanese and White participants. These results support further investigation of NPC-21.

Envelope Glycoprotein based multi-epitope vaccine against a co-infection of Human Herpesvirus 5 and Human Herpesvirus 6 using in silico strategies

The Human Betaherpesviruses HHV-5 and HHV-6 are quite inimical in immunocompromised hosts individually. A co-infection of both has been surmised to be far more disastrous. This can be attributed to a synergetic effect of their combined pathologies. While there have been attempts to develop a vaccine against each virus, no efforts were made to contrive an effective prophylaxis for the highly detrimental co-infection. In this study, an ensemble of viral envelope glycoproteins from both the viruses was utilized to design a multi-epitope vaccine using immunoinformatics tools. A collection of bacterial protein toll-like receptor agonists (BPTAs) was screened to identify a highly immunogenic adjuvant for the vaccine construct. The constructed vaccine was analysed using an array of methodologies ranging from World population coverage analysis to Immune simulation, whose results indicate high vaccine efficacy and stability. Furthermore, codon optimization and in silico cloning analysis were performed to check for efficient expression in a bacterial system. Collectively, these findings demonstrate the potential of the constructed vaccine to elicit an immune response against HHV-5 and HHV-6, thus supporting the viability of in vitro and in vivo studies.

Cell Fusion and Syncytium Formation in Betaherpesvirus Infection

Cell–cell fusion is a fundamental and complex process that occurs during reproduction, organ and tissue growth, cancer metastasis, immune response, and infection. All enveloped viruses express one or more proteins that drive the fusion of the viral envelope with cellular membranes. The same proteins can mediate the fusion of the plasma membranes of adjacent cells, leading to the formation of multinucleated syncytia. While cell–cell fusion triggered by alpha- and gammaherpesviruses is well-studied, much less is known about the fusogenic potential of betaherpesviruses such as human cytomegalovirus (HCMV) and human herpesviruses 6 and 7 (HHV-6 and HHV-7). These are slow-growing viruses that are highly prevalent in the human population and associated with several diseases, particularly in individuals with an immature or impaired immune system such as fetuses and transplant recipients. While HHV-6 and HHV-7 are strictly lymphotropic, HCMV infects a very broad range of cell types including epithelial, endothelial, mesenchymal, and myeloid cells. Syncytia have been observed occasionally for all three betaherpesviruses, both during in vitro and in vivo infection. Since cell–cell fusion may allow efficient spread to neighboring cells without exposure to neutralizing antibodies and other host immune factors, viral-induced syncytia may be important for viral dissemination, long-term persistence, and pathogenicity. In this review, we provide an overview of the viral and cellular factors and mechanisms identified so far in the process of cell–cell fusion induced by betaherpesviruses and discuss the possible consequences for cellular dysfunction and pathogenesis.

The Molecular Tweezer CLR01 Inhibits Antibody-Resistant Cell-to-Cell Spread of Human Cytomegalovirus

Human cytomegalovirus (HCMV) uses two major ways for virus dissemination: infection by cell-free virus and direct cell-to-cell spread. Neutralizing antibodies can efficiently inhibit infection by cell-free virus but mostly fail to prevent cell-to-cell transmission. Here, we show that the ‘molecular tweezer’ CLR01, a broad-spectrum antiviral agent, is not only highly active against infection with cell-free virus but most remarkably inhibits antibody-resistant direct cell-to-cell spread of HCMV. The inhibition of cell-to-cell spread by CLR01 was not limited to HCMV but was also shown for the alphaherpesviruses herpes simplex viruses 1 and 2 (HSV-1, -2). CLR01 is a rapid acting small molecule that inhibits HCMV entry at the attachment and penetration steps. Electron microscopy of extracellular virus particles indicated damage of the viral envelope by CLR01, which likely impairs the infectivity of virus particles. The rapid inactivation of viral particles by CLR01, the viral envelope as the main target, and the inhibition of virus entry at different stages are presumably the key to inhibition of cell-free virus infection and cell-to-cell spread by CLR01. Importance: While cell-free spread enables the human cytomegalovirus (HCMV) and other herpesviruses to transmit between hosts, direct cell-to-cell spread is thought to be more relevant for in vivo dissemination within infected tissues. Cell-to-cell spread is resistant to neutralizing antibodies, thus contributing to the maintenance of virus infection and virus dissemination in the presence of an intact immune system. Therefore, it would be therapeutically interesting to target this mode of spread in order to treat severe HCMV infections and to prevent dissemination of virus within the infected host. The molecular tweezer CLR01 exhibits broad-spectrum antiviral activity against a number of enveloped viruses and efficiently blocks antibody-resistant cell-to-cell spread of HCMV, thus representing a novel class of small molecules with promising antiviral activity.

Mutagenesis of Human Cytomegalovirus Glycoprotein L Disproportionately Disrupts gH/gL/gO over gH/gL/pUL128-131

Cell-free and cell-to-cell spread of herpesviruses involves a core fusion apparatus comprised of the fusion protein glycoprotein B (gB) and the regulatory factor gH/gL. The human cytomegalovirus (HCMV) gH/gL/gO and gH/gL/pUL128-131 facilitate spread in different cell types. The gO and pUL128-131 components bind distinct receptors, but how the gH/gL portions of the complexes functionally compare is not understood. We previously characterized a panel of gL mutants by transient expression and showed that many were impaired for gH/gL-gB-dependent cell-cell fusion but were still able to form gH/gL/pUL128-131 and induce receptor interference. Here, the gL mutants were engineered into the HCMV BAC clones TB40/e-BAC4 (TB), TR, and Merlin (ME), which differ in their utilization of the two complexes for entry and spread. Several of the gL mutations disproportionately impacted gH/gL/gO-dependent entry and spread over gH/gL/pUL128-131 processes. The effects of some mutants could be explained by impaired gH/gL/gO assembly, but other mutants impacted gH/gL/gO function. Soluble gH/gL/gO containing the L201 mutant failed to block HCMV infection despite unimpaired binding to PDGFRα, indicating the existence of other important gH/gL/gO receptors. Another mutant (L139) enhanced the gH/gL/gO-dependent cell-free spread of TR, suggesting a "hyperactive" gH/gL/gO. Recently published crystallography and cryo-electron microscopy studies suggest structural conservation of the gH/gL underlying gH/gL/gO and gH/gL/pUL128-131. However, our data suggest important differences in the gH/gL of the two complexes and support a model in which gH/gL/gO can provide an activation signal for gB. IMPORTANCE The endemic betaherpesvirus HCMV circulates in human populations as a complex mixture of genetically distinct variants, establishes lifelong persistent infections, and causes significant disease in neonates and immunocompromised adults. This study capitalizes on our recent characterizations of three genetically distinct HCMV BAC clones to discern the functions of the envelope glycoprotein complexes gH/gL/gO and gH/gL/pUL128-13, which are promising vaccine targets that share the herpesvirus core fusion apparatus component, gH/gL. Mutations in the shared gL subunit disproportionally affected gH/gL/gO, demonstrating mechanistic differences between the two complexes, and may provide a basis for more refined evaluations of neutralizing antibodies.

Human cytomegalovirus UL42 protein inhibits the degradation of glycoprotein B through inhibition of Nedd4 family ubiquitin E3 ligases

Human cytomegalovirus (HCMV) is a globally ubiquitous pathogen and causes congenital infection as well as opportunistic infection in immunocompromised patients. The HCMV UL42 gene encodes a membrane protein that regulates the function of Nedd4 family ubiquitin E3 ligases through its PPxY motif. As HCMV envelope glycoprotein B (gB) also has a PPxY motif at its C-terminal cytoplasmic domain, we examined whether there was any relationship between UL42 protein with gB. Among the Nedd4 family proteins, Nedd4, Nedd4L, and Itch induced the degradation of gB in transiently expressing cells. The degradation of gB by Nedd4 was inhibited by proteasome inhibitor MG132, lysosome inhibitor chloroquine, and the co-expression of UL42 proteins. Among those Nedd4 family proteins, Itch was re-localized by the co-expression of gB to the perinuclear region of the cytoplasm. A co-immunoprecipitation assay demonstrated an interaction between gB and Itch through its PPxY motif. The 150 kDa gB precursor was aberrantly ubiquitinated, and the total amount of gB was quickly decreased in the absence of UL42. Our results indicate that UL42 prevent the degradation of gB by the inhibition of Nedd4 family proteins. This article is protected by copyright. All rights reserved.

Targeting Conserved Sequences Circumvents the Evolution of Resistance in a Viral Gene Drive against Human Cytomegalovirus

Gene drives are genetic systems designed to efficiently spread a modification through a population. They have been designed almost exclusively in eukaryotic species, especially in insects. We recently developed a CRISPR-based gene drive system in herpesviruses that relies on similar mechanisms and could efficiently spread into a population of wild-type viruses. A common consequence of gene drives in insects is the appearance and selection of drive-resistant sequences that are no longer recognized by CRISPR-Cas9. In this study, we analyzed in cell culture experiments the evolution of resistance in a viral gene drive against human cytomegalovirus. We report that after an initial invasion of the wild-type population, a drive-resistant population is positively selected over time and outcompetes gene drive viruses. However, we show that targeting evolutionarily conserved sequences ensures that drive-resistant viruses acquire long-lasting mutations and are durably attenuated. As a consequence, and even though engineered viruses do not stably persist in the viral population, remaining viruses have a replication defect, leading to a long-term reduction of viral levels. This marks an important step toward developing effective gene drives in herpesviruses, especially for therapeutic applications. IMPORTANCE The use of defective viruses that interfere with the replication of their infectious parent after coinfecting the same cells-a therapeutic strategy known as viral interference-has recently generated a lot of interest. The CRISPR-based system that we recently reported for herpesviruses represents a novel interfering strategy that causes the conversion of wild-type viruses into new recombinant viruses and drives the native viral population to extinction. In this study, we analyzed how targeted viruses evolved resistance against the technology. Through numerical simulations and cell culture experiments with human cytomegalovirus, we showed that after the initial propagation, a resistant viral population is positively selected and outcompetes engineered viruses over time. We show, however, that targeting evolutionarily conserved sequences ensures that resistant viruses are mutated and attenuated, which leads to a long-term reduction of viral levels. This marks an important step toward the development of novel therapeutic strategies against herpesviruses.

Antibody binding to native cytomegalovirus glycoprotein B predicts efficacy of the gB/MF59 vaccine in humans

Human cytomegalovirus (CMV) is the most common infectious cause of infant brain damage and posttransplant complications worldwide. Despite the high global burden of disease, vaccine development to prevent infection remains hampered by challenges in generating protective immunity. The most efficacious CMV vaccine candidate tested to date is a soluble glycoprotein B (gB) subunit vaccine with MF59 adjuvant (gB/MF59), which achieved 50% protection in multiple historical phase 2 clinical trials. The vaccine-elicited immune responses that conferred this protection have remained unclear. We investigated the humoral immune correlates of protection from CMV acquisition in populations of CMV-seronegative adolescent and postpartum women who received the gB/MF59 vaccine. We found that gB/MF59 immunization elicited distinct CMV-specific immunoglobulin G (IgG)-binding profiles and IgG-mediated functional responses in adolescent and postpartum vaccinees, with heterologous CMV strain neutralization observed primarily in adolescent vaccinees. Using penalized multiple logistic regression analysis, we determined that protection against primary CMV infection in both cohorts was associated with serum IgG binding to gB present on a cell surface but not binding to the soluble vaccine antigen, suggesting that IgG binding to cell-associated gB is an immune correlate of vaccine efficacy. Supporting this, we identified gB-specific monoclonal antibodies that differentially recognized soluble or cell-associated gB, revealing that there are structural differences in cell-associated and soluble gB are relevant to the generation of protective immunity. Our results highlight the importance of the native, cell-associated gB conformation in future CMV vaccine design.

Paenibacillus infection with frequent viral coinfection contributes to postinfectious hydrocephalus in Ugandan infants

Postinfectious hydrocephalus (PIH), which often follows neonatal sepsis, is the most common cause of pediatric hydrocephalus worldwide, yet the microbial pathogens underlying this disease remain to be elucidated. Characterization of the microbial agents causing PIH would enable a shift from surgical palliation of cerebrospinal fluid (CSF) accumulation to prevention of the disease. Here, we examined blood and CSF samples collected from 100 consecutive infant cases of PIH and control cases comprising infants with non-postinfectious hydrocephalus in Uganda. Genomic sequencing of samples was undertaken to test for bacterial, fungal, and parasitic DNA; DNA and RNA sequencing was used to identify viruses; and bacterial culture recovery was used to identify potential causative organisms. We found that infection with the bacterium Paenibacillus, together with frequent cytomegalovirus (CMV) coinfection, was associated with PIH in our infant cohort. Assembly of the genome of a facultative anaerobic bacterial isolate recovered from cultures of CSF samples from PIH cases identified a strain of Paenibacillus thiaminolyticus This strain, designated Mbale, was lethal when injected into mice in contrast to the benign reference Paenibacillus strain. These findings show that an unbiased pan-microbial approach enabled characterization of Paenibacillus in CSF samples from PIH cases, and point toward a pathway of more optimal treatment and prevention for PIH and other proximate neonatal infections.

Common Polymorphisms in the Glycoproteins of Human Cytomegalovirus and Associated Strain-Specific Immunity

Human cytomegalovirus (HCMV), one of the most prevalent viruses across the globe, is a common cause of morbidity and mortality for immunocompromised individuals. Recent clinical observations have demonstrated that mixed strain infections are common and may lead to more severe disease progression. This clinical observation illustrates the complexity of the HCMV genome and emphasizes the importance of taking a population-level view of genotypic evolution. Here we review frequently sampled polymorphisms in the glycoproteins of HCMV, comparing the variable regions, and summarizing their corresponding geographic distributions observed to date. The related strain-specific immunity, including neutralization activity and antigen-specific cellular immunity, is also discussed. Given that these glycoproteins are common targets for vaccine design and anti-viral therapies, this observed genetic variation represents an important resource for future efforts to combat HCMV infections.

Human Cytomegalovirus Host Interactions: EGFR and Host Cell Signaling Is a Point of Convergence Between Viral Infection and Functional Changes in Infected Cells

Viruses have evolved diverse strategies to manipulate cellular signaling pathways in order to promote infection and/or persistence. Human cytomegalovirus (HCMV) possesses a number of unique properties that allow the virus to alter cellular events required for infection of a diverse array of host cell types and long-term persistence. Of specific importance is infection of bone marrow derived and myeloid lineage cells, such as peripheral blood monocytes and CD34⁺ hematopoietic progenitor cells (HPCs) because of their essential role in dissemination of the virus and for the establishment of latency. Viral induced signaling through the Epidermal Growth Factor Receptor (EGFR) and other receptors such as integrins are key control points for viral-induced cellular changes and productive and latent infection in host organ systems. This review will explore the current understanding of HCMV strategies utilized to hijack cellular signaling pathways, such as EGFR, to promote the wide-spread dissemination and the classic life-long herpesvirus persistence.

Diazadispiroalkane Derivatives Are New Viral Entry Inhibitors

Herpesviruses are widespread and can cause serious illness. Many currently available antiviral drugs have limited effects, result in rapid development of resistance, and often exhibit dose-dependent toxicity. Especially for human cytomegalovirus (HCMV), new well-tolerated compounds with novel mechanisms of action are urgently needed. In this study, we characterized the antiviral activity of two new diazadispiroalkane derivatives, 11826091 and 11826236. These two small molecules exhibited strong activity against low-passage-number HCMV. Pretreatment of cell-free virus with these compounds greatly reduced infection. Time-of-addition assays where 11826091 or 11826236 was added to cells before infection, before and during infection, or during or after infection demonstrated an inhibitory effect on early steps of infection. Interestingly, 11826236 had an effect by addition to cells after infection. Results from entry assays showed the major effect to be on attachment. Only 11826236 had a minimal effect on penetration comparable to heparin. Further, no effect on virus infection was found for cell lines with a defect in heparan sulfate expression or lacking all surface glycosaminoglycans, indicating that these small molecules bind to heparan sulfate on the cell surface. To test this further, we extended our analyses to pseudorabies virus (PrV), a member of the Alphaherpesvirinae, which is known to use cell surface heparan sulfate for initial attachment via nonessential glycoprotein C (gC). While infection with PrV wild type was strongly impaired by 11826091 or 11826236, as with heparin, a mutant lacking gC was unaffected by either treatment, demonstrating that primary attachment to heparan sulfate via gC is targeted by these small molecules.

Receptors in host pathogen interactions between human cytomegalovirus and the placenta during congenital infection

Cellular receptors in human cytomegalovirus (HCMV) mother to child transmission play an important role in congenital infection. Placental trophoblast cells are a significant cell type in placental development, placental functional processes, and in HCMV transmission. Different cells within the placental floating and chorionic villi present alternate receptors for HCMV cell entry. Syncytiotrophoblasts present neonatal Fc receptors that bind and transport circulating maternal immunoglobulin G across the placental interface which can also be bound to HCMV virions, facilitating viral entry into the placenta and foetal circulation. Cytotrophoblast express HCMV receptors including integrin-α1β1, integrin-αVβ3, epidermal growth factor receptor and platelet-derived growth factor receptor alpha. The latter interacts with HCMV glycoprotein-H, glycoprotein-L and glycoprotein-O (gH/gL/gO) trimers (predominantly in placental fibroblasts) and the gH/gL/pUL128, UL130-UL131A pentameric complex in other placental cell types. The pentameric complex allows viral tropism of placental trophoblasts, endothelial cells, epithelial cells, leukocytes and monocytes. This review outlines HCMV ligands and target receptor proteins in congenital HCMV infection.

Potent Bispecific Neutralizing Antibody Targeting Glycoprotein B and the gH/gL/pUL128/130/131 Complex of Human Cytomegalovirus

Human cytomegalovirus (HCMV) is a ubiquitous pathogen that can cause developmental disorders following congenital infection and life-threatening complications among transplant patients. Potent neutralizing monoclonal antibodies (MAbs) are promising drug candidates against HCMV infection. HCMV can infect a broad range of cell types. Therefore, single neutralizing antibodies targeting one HCMV glycoprotein often lack either potency or broad cell-type coverage. We previously characterized two human-derived HCMV neutralizing MAbs. One was the broadly neutralizing MAb 3-25, which targets the antigenic domain 2 of glycoprotein B (gB). The other was the highly potent MAb 2-18, which specifically recognizes the gH/gL/pUL128/130/131 complex (pentamer). To combine the strengths of gB- and pentamer-targeting MAbs, we developed an IgG-single-chain variable fragment (scFv) bispecific antibody by fusing the 2-18 scFv to the heavy-chain C terminus of MAb 3-25. The resulting bispecific antibody showed high-affinity binding to both gB and pentamer. Functionally, the bispecific antibody demonstrated a combined neutralization breadth and potency of the parental MAbs in multiple cell lines and inhibited postinfection viral spreading. Furthermore, the bispecific antibody was easily produced in CHO cells at a yield above 1 g/liter and showed a single-dose pharmacokinetic profile comparable to that of parental MAb 3-25 in rhesus macaques. Importantly, the bispecific antibody retained broadly and potent neutralizing activity after 21 days in circulation. Taken together, our research provides a proof-of-concept study for developing bispecific neutralizing antibody therapies against HCMV infection.

Human Cytomegalovirus (HCMV)-Specific Antibody Response and Development of Antibody-Dependent Cellular Cytotoxicity Against HCMV After Lung Transplantation

BACKGROUND

Human cytomegalovirus (HCMV) may cause severe infections in lung transplant recipients (LTRs). The impact of the host antibody (AB)-dependent cytotoxicity (ADCC) on HCMV is still unclear. Therefore, we analyzed the AB-response against HCMV glycoprotein B (gB) and the pentameric complex (PC) and the ADCC response in HCMV-seropositive (R+) LTRs and in seronegative recipients of positive organs (D+/R-).

METHODS

Plasma samples were collected from 35 R+ and 28 D+/R- LTRs for 1 (R+) or 2 (D+/R-) years posttransplantation and from 114 healthy control persons. The PC- and gB-specific ABs were assessed by enzyme-linked immunosorbent assay. The ADCC was analyzed by focal expansion assay and CD107 cytotoxicity assay.

RESULTS

In R+ LTRs, significantly higher gB-specific AB levels developed within 1 year posttransplantation than in controls (immunoglobulin [Ig]G1, P < .001; IgG3, P < .001). In addition, higher levels of ADCC were observed by FEA and CD107 assay in R+ patients compared with controls (P < .001). In 23 D+R- patients, HCMV-specific ABs developed. Antibody-dependent cytotoxicity became detectable 3 months posttransplantation in these, with higher ADCC observed in viremic patients. Depletion of gB- and PC-specific ABs revealed that, in particular, gB-specific Abs were associated with the ADCC response.

CONCLUSIONS

We show that a strong ADCC is elicited after transplantation and is especially based on gB-specific ABs.

Analysis of Cytomegalovirus Glycoprotein and Cellular Receptor Interactions

Human cytomegalovirus (HCMV) entry into host cells is a complex process involving interactions between an array of viral glycoproteins with multiple host cell surface receptors. A significant amount of research has been devoted toward identifying these glycoprotein and cellular receptor interactions as the broad cellular tropism of HCMV suggests a highly regulated yet adaptable process that controls viral binding and penetration. However, deciphering the initial binding and cellular receptor activation events by viral glycoproteins remains challenging. The relatively low abundance of receptors and/or interactions with glycoproteins during viral entry, the hydrophobicity of membrane receptors, and the rapid degradation and recycling of activated receptors have complicated the analysis of HCMV entry and the cellular signaling pathways initiated by HCMV engagement to the host membrane. Here, we describe the different methodologies used in our laboratory and others to analyze the interactions between HCMV glycoproteins and host cellular receptors during the entry stage of the viral life cycle.

Vaccine Formulation and Optimization for Human Herpes Virus-5 through an Immunoinformatics Framework

In the current situation, the importance of vaccines for viral diseases has become the need of the hour. The scientific community in the field of virology has taken it upon themselves to develop vaccines for viral infections before an epidemic or pandemic situation arises. Human herpes virus-5 is an emerging situation that has alarming cases with major health concerns, including congenital impairments and infections leading to cancer states. Vaccination is the route most likely to succeed in the battleground with viral infections and consequences. Hence in the present manuscript, we have formulated the multiepitope subunit vaccine and optimized it with the advanced computational immunological framework. As a result, we report the subunit vaccine for HHV-5, comprised of promiscuous cytotoxic T-lymphocytes epitopes, helper T-lymphocytes, and B-cell epitopes engineered with putative adjuvants to ensure the strong immune response. The formulated subunit vaccine depicted high antigenicity and immunogenicity along with sustainable physicochemical characteristics. Molecular dynamics simulation analyses revealed the strong binding of the vaccine with MHC receptors (MHC-1 and MHC-2) and the virus progression specific membrane receptor TLR2 for a 100 ns MD simulation run. The interacting trajectory analysis of the vaccine showed stable binding with minimal deviations through RMSD, RMSF, and secondary structure confinement plot analyses for a long span of 100 ns. Interestingly, the vaccine showed robust immune response statistics for a prolonged time with evoking T-cell and B-cell populations with other vital players of the immune system, through the machine learning-based immune simulation approach. This study paved the way to a multiepitope vaccine for HHV-5 employing the immunoinformatics networks.

Human Cytomegalovirus Envelope Protein gpUL132 Regulates Infectious Virus Production through Formation of the Viral Assembly Compartment

Following infection of permissive cells, human cytomegalovirus (HCMV) induces the reorganization of intracellular membranes resulting in the formation of a distinctive membranous compartment in the cytoplasm of infected cells. This compartment has been designated the viral assembly compartment (AC) and is thought to be a site for cytoplasmic virion assembly and envelopment. In this study, we have demonstrated that a single virion envelope glycoprotein is essential for AC formation in infected cells, and in its absence, there is a significant decrease in the production of infectious virions. These findings are consistent with those from other studies that have demonstrated the importance of host cell proteins in the formation of the AC and demonstrate a critical role of a single virion protein in AC formation and the efficient assembly of infectious virus.

The human cytomegalovirus (HCMV) UL132 open reading frame encodes a 270-amino-acid type I envelope glycoprotein, gpUL132. The deletion of UL132 (ΔUL132) from the HCMV genome results in a pronounced deficit in virus yield, with an approximately 2-log decrease in the production of infectious virus compared to the wild-type (WT) virus. Characterization of the ΔUL132 mutant virus indicated that it was less infectious with a high particle-to-infectious unit ratio and an altered composition of virion proteins compared to the WT virus. In addition, the viral assembly compartment (AC) failed to form in cells infected with the ΔUL132 mutant virus. The expression of gpUL132 in trans rescued the defects in the morphogenesis of the AC in cells infected with the ΔUL132 mutant virus and in infectious virus production. Furthermore, using cell lines expressing chimeric proteins, we demonstrated that the cytosolic domain of gpUL132 was sufficient to rescue AC formation and WT levels of virus production. Progeny virions from ΔUL132-infected cells expressing the cytosolic domain of gpUL132 exhibited particle-to-infectious unit ratios similar to those of the WT virus. Together, our findings argue that gpUL132 is essential for HCMV AC formation and the efficient production of infectious particles, thus highlighting the importance of this envelope protein for the virus-induced reorganization of intracellular membranes and AC formation in the assembly of infectious virus.

High bio-recognizing aptamer designing and optimization against human herpes virus-5

While the world is tackling one of the direst health emergencies, it has come to light that in the fight against viruses, preparedness is everything. A disease with the initial symptoms of the common flu has the capacity to disrupt the life of 7.8 billion people and thus no infection and especially no virus can be ignored. Hence, we have designed the high bio-recognizing DNA aptamer for diagnosis and therapeutics role against glycoprotein-B (gB) of Human Herpes Virus-5 (HHV-5). HHV-5 is linked with epidemiological and asymptomatic diseases leading to high mortality. Herein, we report potent aptamer (5'CTCGCTTACCCCTGGGTGTGCGGG3') which has high specificity to gB with energy score -523.28 kJ/mol, more than reference aptamer L19 (-363.50 kJ/mol). The stable binding of aptamer with gB was confirmed with atomic fluctuations 0.1 to 1.8 Å through anisotropic network analysis. Aptamer formed stem-loop conformation (-1.0 kcal/mol) by stochastic simulation and found stable with physicochemical properties. Importantly, aptamer was found biologically significant with consisting of putative transcription factors in its vicinity (SP1, GATA1, AP2, NF1) and also possesses homology with exonic sequence of SGSH gene which indicated regulatory role in blockade of viruses. Inaddition, we also proposed plausible mechanism of action of aptamer as antiviral therapeutics.

Recognition of a highly conserved glycoprotein B epitope by a bivalent antibody neutralizing HCMV at a post-attachment step

Human cytomegalovirus (HCMV) is one of the main causative agents of congenital viral infection in neonates. HCMV infection also causes serious morbidity and mortality among organ transplant patients. Glycoprotein B (gB) is a major target for HCMV neutralizing antibodies, yet the underlying neutralization mechanisms remain largely unknown. Here we report that 3–25, a gB-specific monoclonal antibody previously isolated from a healthy HCMV-positive donor, efficiently neutralized 14 HCMV strains in both ARPE-19 cells and MRC-5 cells. The core epitope of 3–25 was mapped to a highly conserved linear epitope on antigenic domain 2 (AD-2) of gB. A 1.8 Å crystal structure of 3–25 Fab in complex with the peptide epitope revealed the molecular determinants of 3–25 binding to gB at atomic resolution. Negative-staining electron microscopy (EM) 3D reconstruction of 3–25 Fab in complex with de-glycosylated postfusion gB showed that 3–25 Fab fully occupied the gB trimer at the N-terminus with flexible binding angles. Functionally, 3–25 efficiently inhibited HCMV infection at a post-attachment step by interfering with viral membrane fusion, and restricted post-infection viral spreading in ARPE-19 cells. Interestingly, bivalency was required for HCMV neutralization by AD-2 specific antibody 3–25 but not the AD-4 specific antibody LJP538. In contrast, bivalency was not required for HCMV binding by both antibodies. Taken together, our results reveal the structural basis of gB recognition by 3–25 and demonstrate that inhibition of viral membrane fusion and a requirement of bivalency may be common for gB AD-2 specific neutralizing antibody.

HCMV infection is usually asymptomatic in healthy individuals. However, life-threatening diseases frequently accompany HCMV infection in individuals with under-developed or compromised immune systems. Glycoprotein B antigenic domain 2 (AD-2) is a major target for HCMV-neutralizing antibodies that potentially provide immune protection. We report the structure-based study of gB recognition by a potent neutralizing antibody named 3–25 that binds a highly conserved epitope on AD-2. Functionally, 3–25 efficiently inhibited HCMV infection at a post-attachment step by interfering with viral membrane fusion, and restricted post-infection viral spreading. Furthermore, bivalency of 3–25 is required for viral neutralization but not for binding. Our findings advance understanding of gB antibody-mediated HCMV neutralization and facilitate development of gB-targeted vaccines and antibody drugs against HCMV infection.

Human Cytomegalovirus Glycoprotein-Initiated Signaling Mediates the Aberrant Activation of Akt

Human cytomegalovirus (HCMV) is a major cause of morbidity and mortality among immunocompromised and immunonaive individuals. HCMV-induced signaling initiated during viral entry stimulates a rapid noncanonical activation of Akt to drive the differentiation of short-lived monocytes into long-lived macrophages, which is essential for viral dissemination and persistence. We found that HCMV glycoproteins gB and gH directly bind and activate cellular epidermal growth factor receptor (EGFR) and integrin β1, respectively, to reshape canonical Akt signaling within monocytes. The remodeling of the Akt signaling network was due to the recruitment of nontraditional Akt activators to either the gB- or gH-generated receptor signaling complexes. Phosphoinositide 3-kinase (PI3K) comprised of the p110β catalytic subunit was recruited to the gB/EGFR complex despite p110δ being the primary PI3K isoform found within monocytes. Concomitantly, SH2 domain-containing inositol 5-phosphatase 1 (SHIP1) was recruited to the gH/integrin β1 complex, which is critical to aberrant Akt activation, as SHIP1 diverts PI3K signaling toward a noncanonical pathway. Although integrin β1 was required for SHIP1 recruitment, gB-activated EGFR mediated SHIP1 activation, underscoring the importance of the interplay between gB- and gH-mediated signaling to the unique activation of Akt during HCMV infection. Indeed, SHIP1 activation mediated the increased expression of Mcl-1 and HSP27, two Akt-dependent antiapoptotic proteins specifically upregulated during HCMV infection but not during growth factor treatment. Overall, our data indicate that HCMV glycoproteins gB and gH work in concert to initiate an HCMV-specific signalosome responsible for the atypical activation of Akt required for infected monocyte survival and ultimately viral persistence.IMPORTANCE Human cytomegalovirus (HCMV) infection is endemic throughout the world regardless of socioeconomic conditions and geographic locations with a seroprevalence reaching up to 100% in some developing countries. Although asymptomatic in healthy individuals, HCMV can cause severe multiorgan disease in immunocompromised or immunonaive patients. HCMV disease is a direct consequence of monocyte-mediated systematic spread of the virus following infection. Because monocytes are short-lived cells, HCMV must subvert the natural short life-span of these blood cells by inducing a distinct activation of Akt, a serine/theonine protein kinase. In this work, we demonstrate that HCMV glycoproteins gB and gH work in tandem to reroute classical host cellular receptor signaling to aberrantly activate Akt and drive survival of infected monocytes. Deciphering how HCMV modulates the cellular pathway to induce monocyte survival is important to develop a new class of anti-HCMV drugs that could target and prevent spread of the virus by eliminating infected monocytes.

NK Cell Memory to Cytomegalovirus: Implications for Vaccine Development

Natural killer (NK) cells are innate lymphoid cells that recognize and eliminate virally-infected and cancerous cells. Members of the innate immune system are not usually considered to mediate immune memory, but over the past decade evidence has emerged that NK cells can do this in several contexts. Of these, the best understood and most widely accepted is the response to cytomegaloviruses, with strong evidence for memory to murine cytomegalovirus (MCMV) and several lines of evidence suggesting that the same is likely to be true of human cytomegalovirus (HCMV). The importance of NK cells in the context of HCMV infection is underscored by the armory of NK immune evasion genes encoded by HCMV aimed at subverting the NK cell immune response. As such, ongoing studies that have utilized HCMV to investigate NK cell diversity and function have proven instructive. Here, we discuss our current understanding of NK cell memory to viral infection with a focus on the response to cytomegaloviruses. We will then discuss the implications that this will have for the development of a vaccine against HCMV with particular emphasis on how a strategy that can harness the innate immune system and NK cells could be crucial for the development of a vaccine against this high-priority pathogen.

Human Cytomegalovirus Primary Infection and Reactivation: Insights From Virion-Carried Molecules

Human cytomegalovirus (HCMV), a ubiquitous beta-herpesvirus, is able to establish lifelong latency after initial infection. Periodical reactivation occurs after immunosuppression, remaining a major cause of death in immunocompromised patients. HCMV has to reach a structural and functional balance with the host at its earliest entry. Virion-carried mediators are considered to play pivotal roles in viral adaptation into a new cellular environment upon entry. Additionally, one clear difference between primary infection and reactivation is the idea that virion-packaged factors are already formed such that those molecules can be used swiftly by the virus. In contrast, virion-carried mediators have to be transcribed and translated; thus, they are not readily available during reactivation. Hence, understanding virion-carried molecules helps to elucidate HCMV reactivation. In this article, the impact of virion-packaged molecules on viral structure, biological behavior, and viral life cycle will be reviewed.

A3- and A2B-fluorocorroles: synthesis, X-ray characterization and antiviral activity evaluation against human cytomegalovirus infection

Twenty-nine fluorinated corroles were prepared, spectroscopically characterized, and studied for their antiviral activity against human cytomegalovirus infection. Six corroles were also fully characterized by X-ray crystallography giving insights on their geometrical features. The halogenated corroles reported herein exhibit significantly improved antiviral activity over their non-halogenated counterparts and over nitro-corrole analogs previously reported. Full activity of thirteen A₃-corroles is achieved with four fluorine atoms present on the meso-phenyl ring reaching a selectivity index above 300. The maximum activity is achieved for A₂B-corroles with selectivity indexes above 400. We thus demonstrate that the fluorocorrole is a highly potent platform to synthesize a new generation of anti hCMV molecules.

Guinea pig cytomegalovirus trimer complex gH/gL/gO uses PDGFRA as universal receptor for cell fusion and entry

Species-specific guinea pig cytomegalovirus (GPCMV) causes congenital CMV and the virus encodes homolog glycoprotein complexes to human CMV, including gH-based trimer (gH/gL/gO) and pentamer-complex (PC). Platelet-derived growth factor receptor alpha (gpPDGFRA), only present on fibroblast cells, was identified via CRISPR as the putative receptor for PC-independent GPCMV infection. Immunoprecipitation assays demonstrated direct interaction of gH/gL/gO with gpPDGFRA but not in absence of gO. Expression of viral gB also resulted in precipitation of gB/gH/gL/gO/gpPDGFRA complex. Cell-cell fusion assays determined that expression of gpPDGFRA and gH/gL/gO in adjacent cells enabled cell fusion, which was not enhanced by gB. N-linked gpPDGFRA glycosylation inhibition had limited effect and blocking tyrosine kinase (TK) transduction had no impact on infection. Ectopically expressed gpPDGFRA or TK-domain mutant in trophoblast or epithelial cells previously non-susceptible to GPCMV(PC-) enabled viral infection. In contrast, transient human PDGFRA expression did not complement GPCMV(PC-) infection, a potential basis for viral species specificity.

A Randomized Dose-Escalating Phase I Trial of a Replication-Deficient Lymphocytic Choriomeningitis Virus Vector-Based Vaccine Against Human Cytomegalovirus

BACKGROUND

A vaccine (HB-101) consisting of 2 nonreplicating lymphocytic choriomeningitis virus (LCMV) vectors expressing the human cytomegalovirus antigens glycoprotein B (gB) and the 65-kD phosphoprotein (pp65), respectively, is in development to prevent cytomegalovirus infection.

METHODS

HB-101 was tested in cytomegalovirus-naive, healthy adults in a randomized, double-blind, placebo-controlled, dose-escalation Phase I trial. Fifty-four subjects received low, medium, or high dose of HB-101 or placebo by intramuscular administration at Month 0, 1, and 3. Safety and immunogenicity were the respective primary and secondary endpoints. Subjects were followed for 12 months after the initial immunization.

RESULTS

Vaccination was associated with transient mild to moderate adverse events. HB-101 administration induced dose-dependent gB- and pp65-specific cellular responses, dominated by pp65-specific CD8 T cells, a high fraction of which were polyfunctional. Two administrations were sufficient to elicit dose-dependent gB-binding and cytomegalovirus-neutralizing antibodies (Abs). Cytomegalovirus-specific immune responses were boosted after each administration. Only 1 of 42 vaccine recipients mounted a transient LCMV vector-neutralizing Ab response.

CONCLUSIONS

HB-101 was well tolerated and induced cytomegalovirus-specific polyfunctional CD8 T-cell and neutralizing Ab responses in the majority of subjects. Lack of vector-neutralizing Ab responses should facilitate booster vaccinations. These results justify further clinical evaluation of this vaccine candidate.

Immune Correlates of Protection Against Human Cytomegalovirus Acquisition, Replication, and Disease

Human cytomegalovirus (HCMV) is the most common infectious cause of infant birth defects and an etiology of significant morbidity and mortality in solid organ and hematopoietic stem cell transplant recipients. There is tremendous interest in developing a vaccine or immunotherapeutic to reduce the burden of HCMV-associated disease, yet after nearly a half-century of research and development in this field we remain without such an intervention. Defining immune correlates of protection is a process that enables targeted vaccine/immunotherapeutic discovery and informed evaluation of clinical performance. Outcomes in the HCMV field have previously been measured against a variety of clinical end points, including virus acquisition, systemic replication, and progression to disease. Herein we review immune correlates of protection against each of these end points in turn, showing that control of HCMV likely depends on a combination of innate immune factors, antibodies, and T-cell responses. Furthermore, protective immune responses are heterogeneous, with no single immune parameter predicting protection against all clinical outcomes and stages of HCMV infection. A detailed understanding of protective immune responses for a given clinical end point will inform immunogen selection and guide preclinical and clinical evaluation of vaccines or immunotherapeutics to prevent HCMV-mediated congenital and transplant disease.

Inhibition of Human Cytomegalovirus Entry into Host Cells Through a Pleiotropic Small Molecule

Human cytomegalovirus (HCMV) infections are wide-spread among the general population with manifestations ranging from asymptomatic to severe developmental disabilities in newborns and life-threatening illnesses in individuals with a compromised immune system. Nearly all current drugs suffer from one or more limitations, which emphasizes the critical need to develop new approaches and new molecules. We reasoned that a ‘poly-pharmacy’ approach relying on simultaneous binding to multiple receptors involved in HCMV entry into host cells could pave the way to a more effective therapeutic outcome. This work presents the study of a synthetic, small molecule displaying pleiotropicity of interactions as a competitive antagonist of viral or cell surface receptors including heparan sulfate proteoglycans and heparan sulfate-binding proteins, which play important roles in HCMV entry and spread. Sulfated pentagalloylglucoside (SPGG), a functional mimetic of heparan sulfate, inhibits HCMV entry into human foreskin fibroblasts and neuroepithelioma cells with high potency. At the same time, SPGG exhibits no toxicity at levels as high as 50-fold more than its inhibition potency. Interestingly, cell-ELISA assays showed downregulation in HCMV immediate-early gene 1 and 2 (IE 1&2) expression in presence of SPGG further supporting inhibition of viral entry. Finally, HCMV foci were observed to decrease significantly in the presence of SPGG suggesting impact on viral spread too. Overall, this work offers the first evidence that pleiotropicity, such as demonstrated by SPGG, may offer a new poly-therapeutic approach toward effective inhibition of HCMV.

Distribution of the CMV glycoprotein gH/gL/gO and gH/gL/pUL128/pUL130/pUL131A complex variants and associated clinical manifestations in infants infected congenitally or postnatally

Human cytomegalovirus (CMV) is a major cause of morbidity in fetuses following intrauterine infection. The glycoprotein (g) envelope trimeric gH/gL/gO and pentameric gH/gL/pUL128/pUL130/pUL131A complexes are required for CMV entry into fibroblasts and endothelial/epithelial cells, respectively, and both are targets for neutralizing antibodies. The role of sequence variability among viral strains in the outcome of congenital CMV infection is controversial. Variation in the CMV UL75 gene encoding glycoprotein H (gH), the UL115 (gL), the UL74 (gO), and the UL128 locus (UL128L) encoding three structural proteins (pUL128, pUL130, and pUL131A) was determined in 82 newborns with congenital CMV infection and 113 infants with postnatal or unproven congenital CMV infection. Genotyping was performed by sequencing analysis of PCR-amplified fragments and the PCR-restriction fragment length polymorphism (RFLP) method, and the viral load was measured by quantitative real-time PCR. The obtained results demonstrated that (1) different CMV variants and mixed CMV infections can be detected in newborns infected congenitally; (2) the gH1 genotype, UL130 variant 6, and UL131A variant 1 were associated with some signs/symptoms within cohort of pediatric patients, mainly consisting of infants with symptomatic CMV infection. The results revealed that pUL130, pUL131A, and gH polymorphisms seemed to be associated with the outcome of CMV infection in infants.

Fatal Elephant Endotheliotropic Herpesvirus Infection of Two Young Asian Elephants

Elephant endotheliotropic herpesvirus (EEHV) can cause a devastating haemorrhagic disease in young Asian elephants worldwide. Here, we report the death of two young Asian elephants after suffering from acute haemorrhagic disease due to EEHV-1A infection. We detected widespread distribution of EEHV-1A in various organs and tissues of the infected elephants. Enveloped viral particles accumulated within and around cytoplasmic electron-dense bodies in hepatic endothelial cells were detected. Attempts to isolate the virus on different cell cultures showed limited virus replication; however, late viral protein expression was detected in infected cells. We further showed that glycoprotein B (gB) of EEHV-1A possesses a conserved cleavage site Arg-X-Lys/Arg-Arg that is targeted by the cellular protease furin, similar to other members of the Herpesviridae. We have determined the complete 180 kb genome sequence of EEHV-1A isolated from the liver by next-generation sequencing and de novo assembly. As virus isolation in vitro has been unsuccessful and limited information is available regarding the function of viral proteins, we have attempted to take the initial steps in the development of suitable cell culture system and virus characterization. In addition, the complete genome sequence of an EEHV-1A in Europe will facilitate future studies on the epidemiology and diagnosis of EEHV infection in elephants.