Human cytomegalovirus reinfection is associated with intrauterine transmission in a highly cytomegalovirus-immune maternal population

Congenital Cytomegalovirus Infection

Background: Congenital cytomegalovirus (cCMV) is the leading cause of nongenetic congenital hearing loss in much of the world and a leading cause of neurodevelopmental disabilities. Infected babies can be born to women who are seropositive and seronegative prior to pregnancy, and the incidence is approximately 0.6%-0.7% in the United States. Symptoms vary from mild to severe, and hearing loss can be delayed in onset and progressive. Methods: We reviewed the literature to summarize the epidemiology, clinical manifestations, diagnosis, treatment, and future directions of cCMV. Results: The best way to diagnose the infection is with polymerase chain reaction of urine or saliva within 3 weeks after birth, followed by a repeat confirmatory test if positive. Moderately to severely symptomatic neonates should be treated for 6 months with valganciclovir, and some practitioners also choose to treat infants who have isolated hearing loss only. Treatment is not recommended for asymptomatic infants. All infected infants should be screened for hearing loss and neurodevelopmental sequelae. Universal and targeted screening may be cost effective. Currently, no vaccine is commercially available, although multiple candidates are under study. Conclusion: Congenitally acquired cytomegalovirus is found in all communities around the world with a disease burden that is greater than many other well-known diseases. Advances are being made in prevention and treatment; however, improved awareness of the disease among clinicians and patients is needed.

Subversion of Immune Response by Human Cytomegalovirus

Human cytomegalovirus (HCMV) is the most common cause of congenital infections and is an important pathogen in immunocompromised individuals. Despite a robust host immune system, HCMV able to replicate, evade host defenses, establish latency for life. A significant portion of HCMV genome dedicated to encode gene products for modulation of host immune response. Growing number of HCMV gene products are being recognized to play role in immune evasion. Information on viral immune evasion mechanisms by which HCMV persists in host will be useful in devising antiviral intervention strategies and development of new vaccines. This minireview provides a brief overview of immune evasion strategy adapted by HCMV by utilizing its gene products in modulation of host immune response.

HCMV trimer- and pentamer-specific antibodies synergize for virus neutralization but do not correlate with congenital transmission

Human cytomegalovirus (HCMV) causes severe morbidity and mortality in immunocompromised patients and is the most commonly transmitted virus that causes developmental defects in the fetus. Currently, there is no licensed HCMV vaccine available, and prior efforts using attenuated viruses and subunit vaccines were not successful. Recently, there has been intense interest in the HCMV pentamer glycoprotein as a component of vaccines. Here, we show that transplant patients’ and pregnant mothers’ sera contain neutralizing antibodies specific for the pentamer and also for a second HCMV glycoprotein, the trimer, which is essential for HCMV entry into cells. Trimer- and pentamer-specific antibodies acted synergistically to neutralize virus and block cell–cell spread. These observations will have major implications for the future of HCMV vaccine development.

Human cytomegalovirus (HCMV) causes substantial disease in transplant patients and harms the development of the nervous system in babies infected in utero. Thus, there is a major focus on developing safe and effective HCMV vaccines. Evidence has been presented that a major target of neutralizing antibodies (NAbs) is the HCMV pentamer glycoprotein gH/gL/UL128-131. In some studies, most of the NAbs in animal or human sera were found to recognize the pentamer, which mediates HCMV entry into endothelial and epithelial cells. It was also reported that pentamer-specific antibodies correlate with protection against transmission from mothers to babies. One problem with the studies on pentamer-specific NAbs to date has been that the studies did not compare the pentamer to the other major form of gH/gL, the gH/gL/gO trimer, which is essential for entry into all cell types. Here, we demonstrate that both trimer and pentamer NAbs are frequently found in human transplant patients’ and pregnant mothers’ sera. Depletion of human sera with trimer caused reductions in NAbs similar to that observed following depletion with the pentamer. The trimer- and pentamer-specific antibodies acted in a synergistic fashion to neutralize HCMV and also to prevent virus cell-to-cell spread. Importantly, there was no correlation between the titers of trimer- and pentamer-specific NAbs and transmission of HCMV from mothers to babies. Therefore, both the trimer and pentamer are important targets of NAbs. Nevertheless, these antibodies do not protect against transmission of HCMV from mothers to babies.

Cytomegalovirus immunoglobulin G titers do not predict reactivation risk in immunocompetent hosts

Cytomegalovirus (CMV) reactivation occurs in roughly one-third of immunocompetent patients during critical illness, and is associated with worse outcomes. These outcomes have prompted consideration of early antiviral prophylaxis, but two-third of patients would receive unnecessary treatment. Tissue viral load has been associated with risk of reactivation in murine models, and recent work has suggested a relationship between immune responses to CMV and underlying viral load. We, therefore, sought to confirm the hypothesis that serum CMV-specific immunoglobulin G (IgG) correlates with tissue viral load, and might be used to predict the risk of reactivation during critical illness. We confirm that there is a good correlation between tissue viral load and serum CMV-specific IgG after laboratory infection of inbred mice. Further, we show that naturally infected outbred hosts have variable tissue viral DNA loads that do not correlate well with serum IgG. Perhaps as a consequence, CMV-specific IgG was not predictive of reactivation events in immunocompetent humans. When reactivation did occur, those with the lowest IgG levels had longer durations of reactivation, but IgG quartiles were not associated with differing peak DNAemia. Together our data suggest that CMV-specific IgG titers diverge from tissue viral loads in outbred immunocompetent hosts, and their importance for the control of reactivation events remains unclear.

The seroprevalence of cytomegalovirus infection in Belgium anno 2002 and 2006: a comparative analysis with hepatitis A virus seroprevalence

Cytomegalovirus (CMV) infection is endemic worldwide but its seroprevalence varies widely. The goal of this study was to estimate the age-specific seroprevalence of CMV infection in Belgium based on two cross-sectional serological datasets from 2002 and 2006. The seroprevalence was estimated relying on diagnostic test results based on cut-off values pre-specified by the manufacturers of the tests as well as relying on mixture models applied to continuous pathogen-specific immunoglobulin G antibody titre concentrations. The age-specific seroprevalence of hepatitis A virus (HAV), based on three Belgian cross-sectional serological datasets from 1993, 2002 and 2006, was used as a comparator since individuals acquire lifelong immunity upon recovery, implying an increasing seroprevalence with age. The age group weighted overall CMV seroprevalence derived from the mixture model was 32% (95% confidence interval (CI) 31-34%) in 2002 and 31% (95% CI 30-32%) in 2006. We demonstrated that CMV epidemiology differs from the immunizing infection HAV. This was the first large-scale study of CMV and HAV serial datasets in Belgium, estimating seroprevalence specified by age and birth cohort.

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.

New therapies for human cytomegalovirus infections

The recent approval of letermovir marks a new era of therapy for human cytomegalovirus (HCMV) infections, particularly for the prevention of HCMV disease in hematopoietic stem cell transplant recipients. For almost 30 years ganciclovir has been the therapy of choice for these infections and by today's standards this drug exhibits only modest antiviral activity that is often insufficient to completely suppress viral replication, and drives the selection of drug-resistant variants that continue to replicate and contribute to disease. While ganciclovir remains the therapy of choice, additional drugs that inhibit novel molecular targets, such as letermovir, will be required as highly effective combination therapies are developed not only for the treatment of immunocompromised hosts, but also for congenitally infected infants. Sustained efforts, largely in the biotech industry and academia, have identified additional highly active lead compounds that have progressed into clinical studies with varying levels of success and at least two have the potential to be approved in the near future. Some of the new drugs in the pipeline inhibit new molecular targets, remain effective against isolates that have developed resistance to existing therapies, and promise to augment existing therapeutic regimens. Here, we will describe some of the unique features of HCMV biology and discuss their effect on therapeutic needs. Existing drugs will also be discussed and some of the more promising candidates will be reviewed with an emphasis on those progressing through clinical studies. The in vitro and in vivo antiviral activity, spectrum of antiviral activity, and mechanism of action of new compounds will be reviewed to provide an update on potential new therapies for HCMV infections that have progressed significantly in recent years.

Zika virus infection of first-trimester human placentas: utility of an explant model of replication to evaluate correlates of immune protection ex vivo

The emergence of congenital Zika virus (ZIKV) disease, with its devastating effects on the fetus, has prompted development of vaccines and examination of how ZIKV breaches the maternal-fetal barrier. Infection of placental and decidual tissue explants has demonstrated cell types at the uterine-placental interface susceptible to infection and suggests routes for transmission across the placenta and amniochorionic membrane. ZIKV replicates in proliferating Hofbauer cells within chorionic villi in placentas from severe congenital infection. Explants of anchoring villi recapitulate placental architecture and early-stage development and suggest infected Hofbauer cells disseminate virus to fetal blood vessels. ZIKV infection of explants represents a surrogate human model for evaluating protection against transmission by antibodies in vaccine recipients and passive immune formulations and novel therapeutics.

Cytomegalovirus Shedding in Seropositive Pregnant Women From a High-Seroprevalence Population: The Brazilian Cytomegalovirus Hearing and Maternal Secondary Infection Study

Background

Most congenital cytomegalovirus (CMV) infections in highly seropositive populations occur in infants born to women with preexisting CMV seroimmunity. Although essential for developing prevention strategies, CMV shedding patterns in pregnant women with nonprimary infections have not been characterized. We investigated correlates of CMV shedding in a cohort of seropositive pregnant women.

Methods

In a prospective study, saliva, urine, vaginal swabs, and blood were collected from 120 CMV-seropositive women in the first, second, and third trimesters and 1 month postpartum. Specimens were tested for CMV DNA by polymerase chain reaction. We analyzed the contribution of the specific maternal characteristics to viral shedding.

Results

CMV shedding was detected at least once in 42 (35%) women. Mothers living with or providing daily care to young children (3-6 years) were twice as likely to shed CMV at least once compared to women with less exposure to young children (58% vs 26%; adjusted relative risk [aRR], 2.21; 95% confidence interval [CI], 1.37-3.56). Living in crowded households (≥2 people per room) was associated with viral shedding (64% vs 31%; aRR, 1.99; 95% CI, 1.26-3.13). Sexual activity as indicated by the number of sexual partners per year or condom use was not found to be a correlate of viral shedding.

Conclusions

CMV shedding is relatively frequent in seropositive pregnant women. The association between virus shedding and caring for young children as well as crowded living conditions may provide opportunities for increased exposures that could lead to CMV reinfections in seropositive women.

Maternal Immunity and the Natural History of Congenital Human Cytomegalovirus Infection

Congenital human cytomegalovirus (HCMV) is the most common viral infection of the developing fetus, and a significant cause of neurodevelopmental abnormalities in infants and children. Congenital HCMV infections account for an estimated 25% of all cases of hearing loss in the US. It has long been argued that maternal adaptive immune responses to HCMV can modify both the likelihood of intrauterine transmission of HCMV, and the severity of fetal infection and risk of long term sequelae in infected infants. Over the last two decades, multiple studies have challenged this paradigm, including findings that have demonstrated that the vast majority of infants with congenital HCMV infections in most populations are born to women with established immunity prior to conception. Furthermore, the incidence of clinically apparent congenital HCMV infection in infants born to immune and non-immune pregnant women appears to be similar. These findings from natural history studies have important implications for the design, development, and testing of prophylactic vaccines and biologics for this perinatal infection. This brief overview will provide a discussion of existing data from human natural history studies and animal models of congenital HCMV infections that have described the role of maternal immunity in the natural history of this perinatal infection.

Congenital Viral Infection: Traversing the Uterine-Placental Interface

Why certain viruses cross the physical barrier of the human placenta but others do not is incompletely understood. Over the past 20 years, we have gained deeper knowledge of intrauterine infection and routes of viral transmission. This review focuses on human viruses that replicate in the placenta, infect the fetus, and cause birth defects, including rubella virus, varicella-zoster virus, parvovirus B19, human cytomegalovirus (CMV), Zika virus (ZIKV), and hepatitis E virus type 1. Detailed discussions include ( a) the architecture of the uterine-placental interface, ( b) studies of placental explants ex vivo that provide insights into the infection and spread of CMV and ZIKV to the fetal compartment and how these viruses undermine early development, and ( c) novel treatments and vaccines that limit viral replication and have the potential to reduce dissemination, vertical transmission and the occurrence of congenital disease.

Nonprimary Maternal Cytomegalovirus Infection After Viral Shedding in Infants

BACKGROUND

Most infants with congenital Cytomegalovirus (CMV) infection are born to seropositive women as a result of maternal CMV nonprimary infection (reinfection or reactivation). Although infected children are known to transmit CMV to their seronegative mothers, the frequency and magnitude of nonprimary maternal CMV infection after exposure to viral shedding by children in their household have not been characterized.

METHODS

A cohort of Ugandan newborns and their mothers were tested weekly for CMV by quantitative polymerase chain reaction of oral swabs. Infant primary infection and maternal nonprimary infection were defined by the onset of persistent high-level oral CMV shedding. Strain-specific antibody testing was used to assess maternal reinfection. Cox regression models with time-dependent covariates were used to evaluate risk factors for nonprimary maternal infection.

RESULTS

Nonprimary CMV infection occurred in 15 of 30 mothers, all after primary infection of their infants by a median of 6 weeks (range: 1-10) in contrast to none of the mothers of uninfected infants. The median duration of maternal oral shedding lasted 18 weeks (range: 4-42) reaching a median maximum viral load of 4.69 log copies/mL (range: 3.22-5.64). Previous-week infant CMV oral quantities strongly predicted maternal nonprimary infection (hazard ratio: 2.32 per log10 DNA copies/swab increase; 95% confidence interval: 1.63-3.31). Maternal nonprimary infections were not associated with changes in strain-specific antibody responses.

CONCLUSIONS

Nonprimary CMV infection was common in mothers after primary infection in their infants, consistent with infant-to-mother transmission. Because infants frequently acquire CMV from their mothers, for example, through breast milk, this suggests the possibility of "ping-pong" infections. Additional research is needed to characterize the antigenic and genotypic strains transmitted among children and their mothers.

Use of Cytomegalovirus-Specific Hyperimmunoglobulins in Pregnancy: A Retrospective Cohort

OBJECTIVE

There is no consensus on the use of cytomegalovirus (CMV)-specific hyperimmunoglobulins (CSHIGs) for suspected congenital CMV infections during pregnancy, but this therapy is currently used in some countries. The objectives of this study were to describe tolerability and pregnancy outcome following treatment with monthly intravenous CSHIG and compare rates of positive PCR and postnatal symptoms according to whether CSHIGs were given or not.

METHODS

This retrospective cohort study included all pregnant women who were diagnosed with primary CMV infection or congenital CMV infection at the Centre Hospitalier Universitaire Sainte-Justine (Montreal, QC) between 2005 and 2016. CSHIG was discussed with pregnant women who received positive CMV PCR results from amniotic fluid or if ultrasound anomalies suggested congenital infection and there was serologic evidence of maternal primary infection (therapeutic group). CSHIG was also offered as prophylaxis in pregnant women without fetal ultrasound anomalies but with evidence of maternal primary infection, when amniocentesis either had negative results or was not performed (prophylactic group). A matched analysis was performed to control for timing of maternal infection, amniocentesis, and type and timing of ultrasound anomaly.

RESULTS

Sixteen women received CSHIG, and 55 had no CMV-specific treatment. CSHIG treatment was well-tolerated. In bivariate analyses, the risk of congenital CMV infection and postnatal symptoms did not significantly decrease with CSHIG treatment, in both the therapeutic and the prophylactic groups. After matching, there was still no difference in outcomes between CSHIG-treated and untreated women.

CONCLUSION

The effectiveness of CSHIG in preventing congenital CMV infection and its clinical manifestations could not be demonstrated.

Congenital cytomegalovirus infection

Each year, thousands of children are born with or develop permanent disabilities such as hearing loss, vision loss, motor and cognitive deficits from congenital CMV infection (cCMV). However, awareness of cCMV and its associated sequelae is very low in pregnant women and healthcare providers. Both targeted and universal approaches to screen newborns for CMV infection are now achievable due to recent scientific advances including the development of a rapid, high-throughput method for detecting CMV in saliva, the efficacy of antiviral treatment in symptomatic infants, and the demonstration of cost effectiveness of CMV screening. Future studies are needed to address gaps in our understanding on the role of non-primary maternal CMV infections, the evaluation of antiviral treatment in asymptomatic infants, and the implementation of prevention strategies for cCMV.

Advancing Our Understanding of Protective Maternal Immunity as a Guide for Development of Vaccines To Reduce Congenital Cytomegalovirus Infections

Human cytomegalovirus (HCMV) is the most common congenitally transmitted pathogen worldwide, impacting an estimated 1 million newborns annually. Congenital HCMV (cCMV) infection is a major global contributor to long-term neurologic deficits, including deafness, microcephaly, and neurodevelopmental delay, as well as to fetal loss and occasional infant mortality. Accordingly, design of a maternal vaccine to prevent cCMV continues to be a top public health priority. Nevertheless, we remain without a licensed vaccine. Maternal immunity provides partial protection, as the risk of vertical HCMV transmission from chronically infected mothers is reduced compared to settings in which the mother is newly infected during pregnancy. Therefore, an understanding of the maternal immune correlates of protection against cCMV is critical to informing design of an efficacious maternal vaccine. Although vaccine development is being assiduously pursued by a large number of pharmaceutical manufacturers, biotechnology organizations, and academic researchers, some pessimism has been expressed regarding the issue of whether a vaccine to protect against cCMV is possible. This pessimism is based on observations that natural immunity is not completely protective against maternal reinfection and congenital transmission. However, we assert that optimism regarding vaccine development is indeed justified, on the basis of accruing evidence of immune correlates of protection-readily achievable by vaccination-that are associated with reduced transmission of HCMV to the fetus in seronegative women. In light of the substantial burden on society conferred by cCMV infection, even a modest reduction in the occurrence of this fetal disease is an important public health goal and justifies aggressive clinical evaluation of vaccines currently in the pipeline.

The convergent epidemiology of tuberculosis and human cytomegalovirus infection

Although several factors are known to increase the risk of tuberculosis, the occurrence of tuberculosis disease in an infected individual is difficult to predict. We hypothesize that active human cytomegalovirus infection due to recent infection, reinfection or reactivation plays an epidemiologically relevant role in the aetiology of tuberculosis by precipitating the progression from latent tuberculosis infection to disease. The most compelling support for this hypothesis comes from the striking similarity in age-sex distribution between the two infections, important because the age-sex pattern of tuberculosis disease progression has not been convincingly explained. Cytomegalovirus infection and tuberculosis have other overlapping risk factors, including poor socio-economic status, solid organ transplantation and, possibly, sexual contact and whole blood transfusion. Although each of these overlaps could be explained by shared underlying risk factors, none of the epidemiological observations refute the hypothesis. If this interaction would play an epidemiologically important role, important opportunities would arise for novel approaches to controlling tuberculosis.

The convergent epidemiology of tuberculosis and human cytomegalovirus infection

Although several factors are known to increase the risk of tuberculosis, the occurrence of tuberculosis disease in an infected individual is difficult to predict. We hypothesize that active human cytomegalovirus infection due to recent infection, reinfection or reactivation plays an epidemiologically relevant role in the aetiology of tuberculosis by precipitating the progression from latent tuberculosis infection to disease. The most compelling support for this hypothesis comes from the striking similarity in age-sex distribution between the two infections, important because the age-sex pattern of tuberculosis disease progression has not been convincingly explained. Cytomegalovirus infection and tuberculosis have other overlapping risk factors, including poor socio-economic status, sexual contact, whole blood transfusion and solid organ transplantation. Although each of these overlaps could be explained by shared underlying risk factors, none of the epidemiological observations refute the hypothesis. If this interaction would play an epidemiologically important role, important opportunities would arise for novel approaches to controlling tuberculosis.

Maternal and fetal cytomegalovirus infection: diagnosis, management, and prevention

Congenital cytomegalovirus infection is a major cause of central nervous system and sensory impairments that affect cognition, motor function, hearing, language development, vestibular function, and vision. Although the importance of congenital cytomegalovirus infection is readily evident, the vast majority of maternal and fetal infections are not identified, even in developed countries. Multiple studies of prenatal cytomegalovirus infections have produced a body of knowledge that can inform the clinical approach to suspected or proven maternal and fetal infection. Reliable diagnosis of cytomegalovirus infection during pregnancy and accurate diagnosis of fetal infection are a reality. Approaches to preventing the transmission of cytomegalovirus from mother to fetus and to the treatment of fetal infection are being studied. There is evidence that public health approaches based on hygiene can dramatically reduce the rate of primary maternal cytomegalovirus infections during pregnancy. This review will consider the epidemiology of congenital cytomegalovirus infection, the diagnosis and management of primary infection during pregnancy, and approaches to preventing maternal infection.

Congenital cytomegalovirus - who, when, what-with and why to treat?

Congenital cytomegalovirus (CMV) is the commonest cause of congenital infection worldwide and the leading non-genetic cause of sensorineural hearing loss in children. Appropriate investigations and timely decision on treatment is required as studies have shown that treatment with antiviral therapy leads to improved hearing and neurodevelopmental outcomes in the long term when started in the first month of life. This paper outlines the epidemiology, investigations in the diagnosis of congenital CMV infection and current evidence surrounding treatment.

Immune responses to congenital cytomegalovirus infection

Human cytomegalovirus (HCMV) is the most common cause of viral infection acquired in utero. Even though the infection has been studied for several decades, immune determinants important for virus control and mechanisms of long-term sequelae caused by infection are still insufficiently characterized. Animal models of congenital HCMV infection provide unique opportunity to study various aspects of human disease. In this review, we summarize current knowledge on the role of immune system in congenital CMV infection, with emphasis on lessons learned from mouse model of congenital CMV infection.

High Seroprevalence of CMV Among Women of Childbearing Age Implicates High Burden of Congenital Cytomegalovirus Infection in Poland

Cytomegaloviruses are common worldwide, with variable frequency of infections. The infection in pregnancy may lead to pregnancy loss or serious sequelae for the child. To understand the risk posed by CMV in Poland we conducted cross-sectional study on women aged 15-49 basing on existing serum bank. Age dependent incidence, the rates of congenital infection and sequelae were modelled from sero-prevalence, literature and demographic data. The overall anti-CMV IgG prevalence was 81.9% increasing from 74.3% in <30 years old to 94.3% in subjects 45+ years old. The lowest incidence was estimated at the age of 15 and the highest at the age 34 (3.8 and 8.95 respectively/100 women/year). The estimated rate of cCMV varies from 22.4 to 37.2 per 1000 live birth depending on the assumptions made. The proportion of cases due to secondary infection ranged from 34.8% to 49.9% accordingly.

Congenital Human Cytomegalovirus Infection and the Enigma of Maternal Immunity

Human cytomegalovirus (HCMV) is the most common viral infection acquired by the developing human fetus and can result in damage to the developing central nervous system. Although vaccine development to modify this congenital infection is ongoing, the unique epidemiology of maternal HCMV infections appears discordant with strategies for vaccine development. Several characteristics of congenital HCMV infections suggest that the efficacy of vaccines designed to induce responses similar to those that follow natural infection will be limited.

Congenital cytomegalovirus infection in Central Germany: an underestimated risk

PURPOSE

This is the first study to determine the cytomegalovirus (CMV) seronegativity rate for women of childbearing age in Saxony-Anhalt and to determine the prevalence of clinically relevant congenital CMV (cCMV) infection in Central Germany, because there are no valid data available.

METHODS

The retrospective study was undertaken between January 2005 and December 2015. For the first time in Germany, the following seven data sources were used to analyze the prevalence of clinically relevant cCMV infection and the rate of CMV seronegative women of childbearing age: CMV Screening in maternity unit, University Women's Hospital, Social Paediatrics Centre (SPC), Malformation Monitoring Centre (MMC), Newborn Hearing Screening (NHS), Neonatal Intensive Care Unit (NICU), and In-house Doctor Department. Key parameters were anti-CMV IgG and IgM, CMV PCR of urine, and clinically relevant symptoms caused by CMV.

RESULTS

Between 46 and 52% of women of childbearing age were CMV seronegative. The prevalence of clinically relevant cCMV infection was between 0.008 and 0.04%.

CONCLUSIONS

The CMV seronegativity rate of women of childbearing age was confirmed to be in the middle range of estimated data from other sources in Germany. Data from the NICU, SPC, NHS, and MMC show the prevalence of clinically relevant cCMV infection. The risk of all cCMV infections is underestimated. Thus, the true prevalence of clinically relevant and subclinical cCMV infections is >0.04%.

Cytomegalovirus infection in pregnancy

Cytomegalovirus (CMV) is a DNA herpesvirus that is common worldwide. The two known main sources of primary CMV infection during pregnancy are through sexual activity and contact with young children. Primary infection occurs in approximately 1 to 4% of pregnancies, and is mostly asymptomatic in immunocompetent adults. However, primary infection may manifest as a mild mononucleosis or flu-like syndrome with persistent fever and fatigue. CMV can be transmitted from mother-to-child in utero, intrapartum, or during breastfeeding. Intrauterine transmission can lead to congenital CMV infection, a leading cause of permanent hearing and vision loss and neurological disability among children. Congenital CMV transmission rates are as high as 50% in women who acquire primary CMV infection during pregnancy, and less than 2% in women with nonprimary infection. There is no licensed CMV vaccine. Good hygiene practices and avoiding intimate contact with young children (e.g., kissing on the mouth and sharing utensils) have been suggested as an approach to prevent maternal primary CMV infection during pregnancy, but remains an unproven method of reducing the risk of congenital CMV infection. Approximately 1 in 10 infants who acquire CMV in utero will have clinical signs at birth, and an additional 10 to 15% will go on to develop late-onset sequelae. Antiviral treatment prenatally and postnatally has not proven effective at preventing congenital or postnatal CMV infection, and is not recommended for routine clinical care. However, antiviral treatment when initiated in the first month of life for symptomatic congenital CMV infection is recommended for improved neurodevelopmental and audiologic outcomes. Birth Defects Research 109:336-346, 2017. © 2017 Wiley Periodicals, Inc.

Neutralization of Diverse Human Cytomegalovirus Strains Conferred by Antibodies Targeting Viral gH/gL/pUL128-131 Pentameric Complex

Human cytomegalovirus (HCMV) is the leading cause of congenital viral infection, and developing a prophylactic vaccine is of high priority to public health. We recently reported a replication-defective human cytomegalovirus with restored pentameric complex glycoprotein H (gH)/gL/pUL128-131 for prevention of congenital HCMV infection. While the quantity of vaccine-induced antibody responses can be measured in a viral neutralization assay, assessing the quality of such responses, including the ability of vaccine-induced antibodies to cross-neutralize the field strains of HCMV, remains a challenge. In this study, with a panel of neutralizing antibodies from three healthy human donors with natural HCMV infection or a vaccinated animal, we mapped eight sites on the dominant virus-neutralizing antigen—the pentameric complex of glycoprotein H (gH), gL, and pUL128, pUL130, and pUL131. By evaluating the site-specific antibodies in vaccine immune sera, we demonstrated that vaccination elicited functional antiviral antibodies to multiple neutralizing sites in rhesus macaques, with quality attributes comparable to those of CMV hyperimmune globulin. Furthermore, these immune sera showed antiviral activities against a panel of genetically distinct HCMV clinical isolates. These results highlighted the importance of understanding the quality of vaccine-induced antibody responses, which includes not only the neutralizing potency in key cell types but also the ability to protect against the genetically diverse field strains.

IMPORTANCE HCMV is the leading cause of congenital viral infection, and development of a preventive vaccine is a high public health priority. To understand the strain coverage of vaccine-induced immune responses in comparison with natural immunity, we used a panel of broadly neutralizing antibodies to identify the immunogenic sites of a dominant viral antigen—the pentameric complex. We further demonstrated that following vaccination of a replication-defective virus with the restored pentameric complex, rhesus macaques can develop broadly neutralizing antibodies targeting multiple immunogenic sites of the pentameric complex. Such analyses of site-specific antibody responses are imperative to our assessment of the quality of vaccine-induced immunity in clinical studies.

Congenital cytomegalovirus infection in pregnancy and the neonate: consensus recommendations for prevention, diagnosis, and therapy

Congenital cytomegalovirus is the most frequent, yet under-recognised, infectious cause of newborn malformation in developed countries. Despite its clinical and public health importance, questions remain regarding the best diagnostic methods for identifying maternal and neonatal infection, and regarding optimal prevention and therapeutic strategies for infected mothers and neonates. The absence of guidelines impairs global efforts to decrease the effect of congenital cytomegalovirus. Data in the literature suggest that congenital cytomegalovirus infection remains a research priority, but data are yet to be translated into clinical practice. An informal International Congenital Cytomegalovirus Recommendations Group was convened in 2015 to address these questions and to provide recommendations for prevention, diagnosis, and treatment. On the basis of consensus discussions and a review of the literature, we do not support universal screening of mothers and the routine use of cytomegalovirus immunoglobulin for prophylaxis or treatment of infected mothers. However, treatment guidelines for infected neonates were recommended. Consideration must be given to universal neonatal screening for cytomegalovirus to facilitate early detection and intervention for sensorineural hearing loss and developmental delay, where appropriate. The group agreed that education and prevention strategies for mothers were beneficial, and that recommendations will need continual updating as further data become available.

Polymorphisms and features of cytomegalovirus UL144 and UL146 in congenitally infected neonates with hepatic involvement

Human cytomegalovirus is a significant agent of hepatic involvement in neonates. In this study, we investigated the polymorphisms and features of the viral genes UL144 and UL146 as well as their significance to congenital hepatic involvement. In 79 neonates with congenital cytomegalovirus infection and hepatic involvement, full length UL144 and UL146 were successfully amplified in 73.42% and 60.76% of cases, respectively. Sequencing indicated that both genes were hypervariable. Notably, UL144 genotype B was highly associated with aspartate aminotransferase (P = 0.028) and lactate dehydrogenase (P = 0.046). Similarly, UL146 genotype G1 and G13 were significantly associated with CMV IgM (P = 0.026), CMV IgG (P = 0.034), alanine aminotransferase (P = 0.019), and aspartate aminotransferase (P = 0.032). In conclusion, dominant UL144 (genotype B) and UL146 (genotype G1 and G13) genotypes are associated with elevated levels of enzymes and CMV IgM and IgG of cytomegalovirus infection.

Cytomegalovirus vaccines under clinical development

Congenital cytomegalovirus (CMV) infection is the most common infectious cause of disability in newborn infants. CMV also causes serious disease in solid organ (SOT) and haematopoietic stem cell transplant (HSCT) recipients. In otherwise healthy children and adults, primary CMV infection rarely causes illness. However, even asymptomatic CMV infections may predispose an individual towards an increased risk of atherosclerosis, cancer and immune senescence over the life course, although such associations remain controversial. Thus, although a vaccine against congenital CMV infection would have the greatest public health impact and cost-effectiveness, arguably all populations could benefit from an effective immunisation against this virus. Currently there are no licensed CMV vaccines, but there is increased interest in developing and testing potential candidates, driven by the demonstration that a recombinant CMV glycoprotein B (gB) vaccine has some efficacy in prevention of infection in young women and adolescents, and in CMV-seronegative SOT recipients. In this review, the recent and current status of candidate CMV vaccines is discussed. Evolving concepts about proposed correlates of protective immunity in different target populations for CMV vaccination, and how these differences impact current clinical trials, are also reviewed.

Dynamics of Persistent Oral Cytomegalovirus Shedding During Primary Infection in Ugandan Infants

Cytomegalovirus (CMV) infection occurs frequently in young children, who, when infected, are then a major source of transmission. Oral CMV shedding by 14 infants with primary infection was comprehensively characterized using quantitative polymerase chain reaction weekly for ≥9 months. Three phases of oral shedding were identified: expansion, transition, and clearance. Viral expansion occurred over a median of 7 weeks, with a median doubling time of 3 days. During the transition phase, expansion slowed over a median of 6 weeks before peak viral load was reached. Clearance was slow (22-day median half-life), and shedding did not resolve during observation for any infant. Mathematical modeling demonstrated that prolonged oral CMV expansion is explained by a low within-host reproduction number (median, 1.63) and a delayed immune response that only decreases the infected cell half-life by 44%. Thus, the prolonged oral CMV shedding observed during primary infection can be explained by slow viral expansion and inefficient immunologic control.

Prospects of a vaccine for the prevention of congenital cytomegalovirus disease

Congenital human cytomegalovirus (HCMV) infection is one leading cause of childhood disabilities. Prevention of congenital HCMV disease by vaccination has consequently been identified as a priority public healthcare goal. Several vaccine candidates have been introduced in the past that aimed at the prevention of primary HCMV infection in pregnancy. None of these has provided complete protection, and no licensed vaccine is thus far available. An additional level of complexity has been reached by recent studies indicating that the burden of HCMV transmission and disease following non-primary infections in pregnancy may be higher than previously anticipated. Substantial progress in our understanding of the immunobiology of HCMV infection in pregnancy has fostered studies to test revised or novel vaccine strategies. Preventing HCMV transmission has been identified a surrogate endpoint, rendering the conduction of vaccine studies feasible with reasonable effort. Identification of the glycoprotein complex gH/gL/UL128-131 as a mediator of HCMV host cell tropism and evaluation of that complex as a major target of the neutralizing antibody response made manufacturers consider vaccine candidates that include these proteins. Detailed structural analyses of the neutralizing determinants on HCMV glycoprotein B (gB) have revived interest in using this protein in its pre-fusion conformation for vaccine purposes. Studies in pregnant women and in animal models have provided evidence that addressing the T lymphocyte response by vaccination may be crucial to prevent HCMV transmission to the offspring. CD4 T lymphocytes may be of particular importance in this respect. A simultaneous targeting of both the humoral and cellular immune response against HCMV by vaccination thus appears warranted in order to prevent congenital HCMV infection. There is, however, still need for further research to be able to define an immunological correlate of protection against HCMV transmission during pregnancy. This brief review will highlight recent developments in our understanding of the natural history and immunobiology of HCMV infection in pregnancy and their possible impact on the strategies for the development of an HCMV vaccine.

Emerging Role of Zika Virus in Adverse Fetal and Neonatal Outcomes

The rapid spread of the Zika virus (ZIKV) in the Americas and its potential association with thousands of suspected cases of microcephaly in Brazil and higher rates of Guillain-Barré syndrome meet the conditions for a Public Health Emergency of International Concern, as stated by the World Health Organization in February 2016. Two months later, the Centers for Disease Control and Prevention (CDC) announced that the current available evidence supports the existence of a causal relationship between prenatal Zika virus infection and microcephaly and other serious brain anomalies. Microcephaly can be caused by several factors, and its clinical course and prognosis are difficult to predict. Other pathogens with proven teratogenicity have been identified long before the current ZIKV epidemic. Despite the growing number of cases with maternal signs of infection and/or presence of ZIKV in tissues of affected newborns or fetuses, it is currently difficult to assess the magnitude of increase of microcephaly prevalence in Brazil, as well as the role of other factors in the development of congenital neurological conditions. Meanwhile, health agencies and medical organizations have issued cautious guidelines advising health care practitioners and expectant couples traveling to, returning from, or living in affected areas. Analogous to dengue virus (DENV) epidemics, ZIKV has the potential to become endemic in all countries infested by Aedes mosquitoes, while new mutations could impact viral replication in humans, leading to increased virulence and consequently heightened chances of viral transmission to additional naive mosquito vectors. Studies are urgently needed to answer the questions surrounding ZIKV and its role in congenital neurological conditions.

Human cytomegalovirus (CMV) in Africa: a neglected but important pathogen

In Africa, human cytomegalovirus (CMV) is an important pathogen in a diverse range of patient groups. Congenital CMV infection is common, and most children undergo primary infection during the first year of life. Preliminary studies suggest that these early primary CMV infections could have population-wide effects on growth and development. In most studies of adults, CMV seroprevalence is close to 100%, but some studies have found that significant minorities of adults are seronegative. CMV is a common cause of pneumonia and meningitis in hospitalised immunosuppressed patient groups, and CMV DNAemia may be an important marker of rapid progression and poor outcomes of HIV infection, despite roll-out of antiretroviral therapy (ART). Diagnosis and treatment of CMV-related disease is broadly neglected in Africa, and no randomised clinical trials of anti-CMV drugs have been conducted to date. Autopsy is rarely performed in Africa, but identifies CMV as a frequent pathogen when it is carried out. Here we review the available literature on CMV in Africa, primarily in adult patients, and discuss this in the context of contemporary understanding of CMV as a human pathogen.

Influence of parity and sexual history on cytomegalovirus seroprevalence among women aged 20-49 years in the USA

OBJECTIVE

To assess the influence of parity, as a proxy for exposure to children, and sexual history on cytomegalovirus (CMV) seroprevalence.

METHODS

Data were retrospectively analyzed from women aged 20-49 years who were tested for CMV immunoglobulin G antibodies in the 1999-2004 National Health and Nutrition Examination Survey, a nationally representative survey of the US population. Logistic regression was used to determine independent variables associated with CMV seroprevalence.

RESULTS

Among 3710 women, the age-adjusted CMV seroprevalence was 61.3% (95% CI 58.9%-63.6%). In age-adjusted univariate analysis, women who had given birth at least once had higher overall CMV seroprevalence (66.0%, 95% CI 63.1%-68.9%) than did those who had not given birth (49.0%, 95% CI 44.4%-53.7%; P<0.001). In multivariate logistic analysis, higher CMV seroprevalence was independently associated with number of live births (each additional birth: adjusted odds ratio [aOR] 1.2, 95% CI 1.1-1.3), age at first sexual intercourse (<18 vs ≥18years: aOR 1.3, 95% CI 1.1-1.6), lifetime sexual partners (≥10 vs <10: aOR 1.4, 95% CI 1.1-1.9), and herpes type 2 seropositivity (aOR 1.9, 95% CI 1.5-2.6) after controlling for age, race/Hispanic origin, place of birth, poverty index, and education.

CONCLUSION

Among US women of reproductive age, parity and sexual exposures were independently associated with increased CMV seroprevalence.

Cytomegalovirus non-primary infection during pregnancy. Can serology help with diagnosis?

Diagnosis of cytomegalovirus (CMV) primary infection is reliable, but diagnosis of CMV non-primary infection (NPI) is questionable. Our aim is to highlight the difficulties met in diagnosis of CMV NPI. We illustrate that in proven cases of CMV NPI, very different serologic and molecular patterns may be observed and that routine serologic testing may fail to help with diagnosis. These results point out that many data available in literature concerning the prevalence of NPI, materno-fetal transmission rates and consequences of NPI may be wrong. We need to know how frequently they occur, are transmitted and cause fetal damages. Diagnosis of NPI must be improved, along with our understanding of the mechanisms leading to intrauterine CMV transmission and congenital infection in babies born to women with preexisting immunity.

Low Interferon Relative-Response to Cytomegalovirus Is Associated with Low Likelihood of Intrauterine Transmission of the Virus

Background

Congenital Cytomegalovirus (CMV) is a very common intrauterine infection which can cause severe mental and hearing impairments. Notably, only 40% of primarily infected women transmit CMV to the fetus. CMV-specific T-cell response has a role in CMV disease but individual immune heterogeneity precludes reliable correlation between measurable T-cells response and intrauterine transmission.

Study Aim

To establish a correlation between maternal T-cells response and fetal CMV transmission using an individual normalized immune response.

Methods

We analyzed IFN-γ secretion upon whole blood stimulation from primary CMV-infected pregnant women, with either CMV-peptides or PHA-mitogen.

Results

We established a new normalization method of individual IFN-γ response to CMV by defining the ratio between specific-CMV response and non-specific mitogen response (defined as IFN-γ relative response, RR), aiming to overcome high person-to-person immune variability. We found a unique subpopulation of women with low IFN-γ RR strongly correlated with absence of transmission. IFN-γ RR lower than 1.8% (threshold determined by ROC analysis) reduces the pre-test probability of transmission from 40% to 8%, revealing an unexpected link between low IFN-γ RR and non-transmission.

Conclusion

In pregnant women with primary CMV infection, low IFN-γ RR is associated with low risk of transmission.

Preventing Congenital Cytomegalovirus Infection: Protection to a 'T'

A lack of knowledge about the correlates of maternal immunity required for protection of the placenta and fetus against congenital cytomegalovirus (CMV) transmission has complicated vaccine development. New work from Bialas and colleagues demonstrates a critical role for maternal CD4(+) T cells in controlling viremia and preventing CMV-associated fetal disease.

Molecular Detection of Human Cytomegalovirus (HCMV) Among Infants with Congenital Anomalies in Khartoum State, Sudan

Human Cytomegalovirus (HCMV) infection still represents the most common potentially serious viral complication in humans and is a major cause of congenital anomalies in infants. This study is aimed to detect HCMV in infants with congenital anomalies.

Study subjects consisted of infants born with neural tube defect, hydrocephalus and microcephaly.

Fifty serum specimens (20 males, 30 females) were collected from different hospitals in Khartoum State. The sera were investigated for cytomegalovirus specific immunoglobin M (IgM) antibodies using enzyme-linked immunosorbent assay (ELISA), and for Cytomegalovirus DNA using polymerase chain reaction (PCR).

Out of the 50 sera tested, one patient’s (2%) sample showed HCMV IgM, but with no detectable DNA, other 4(8.2 %) sera were positive for HCMV DNA but with no detectable IgM.

Various diagnostic techniques should be considered to evaluate HCMV disease and routine screening for HCMV should be introduced for pregnant women in this setting. It is vital to initiate further research work with many samples from different area to assess prevalence and characterize HCMV and evaluate its maternal health implications.

Awareness of Cytomegalovirus Infection among Pregnant Women in Geneva, Switzerland: A Cross-sectional Study

BACKGROUND

Cytomegalovirus (CMV) is the most frequent cause of congenital infection and commonly associated with sensorineural deficit. At present, there is neither prophylaxis nor treatment during pregnancy. The objective of this study was to evaluate the level of awareness regarding CMV infection and its consequences in women delivering at the University of Geneva Hospitals (Geneva, Switzerland).

METHODS

The study consisted of a validated questionnaire completed by women in the immediate postpartum period.

RESULTS

The questionnaire was completed by 59% (314/528) of delivering women. Only 39% (123/314) knew about CMV and 19.7% (62/314) had received information about preventive measures. Women were more aware about other congenital diseases, such as toxoplasmosis (87%); human immunodeficiency virus (99%); syphilis (85.5%); rubella (92.3%); and group B Streptococcus (63%). Factors associated with CMV awareness were Swiss nationality, high education level, employment in health care or with children, and being followed by an obstetrician. Regarding quality of information, few were aware of the main CMV complications (deafness, 25.2%; mental retardation, 34.5%). Among those informed about CMV, most (74.6%) knew about preventive measures. Among these, 82.5% thought that these were easily applicable.

CONCLUSIONS

Most women were unaware of CMV infection and its potential risks during pregnancy. It is crucial to improve CMV information given to pregnant women to prevent the risks for the fetus/newborn.

Congenital cytomegalovirus infection in pregnancy: a review of prevalence, clinical features, diagnosis and prevention

Human cytomegalovirus (CMV) is under-recognised, despite being the leading infectious cause of congenital malformation, affecting ~0.3% of Australian live births. Approximately 11% of infants born with congenital CMV infection are symptomatic, resulting in clinical manifestations, including jaundice, hepatosplenomegaly, petechiae, microcephaly, intrauterine growth restriction and death. Congenital CMV infection may cause severe long-term sequelae, including progressive sensorineural hearing loss and developmental delay in 40-58% of symptomatic neonates, and ~14% of initially asymptomatic infected neonates. Up to 50% of maternal CMV infections have nonspecific clinical manifestations, and most remain undetected unless specific serological testing is undertaken. The combination of serology tests for CMV-specific IgM, IgG and IgG avidity provide improved distinction between primary and secondary maternal infections. In pregnancies with confirmed primary maternal CMV infection, amniocentesis with CMV-PCR performed on amniotic fluid, undertaken after 21-22 weeks gestation, may determine whether maternofetal virus transmission has occurred. Ultrasound and, to a lesser extent, magnetic resonance imaging are valuable tools to assess fetal structural and growth abnormalities, although the absence of fetal abnormalities does not exclude fetal damage. Diagnosis of congenital CMV infection at birth or in the first 3 weeks of an infant's life is crucial, as this should prompt interventions for prevention of delayed-onset hearing loss and neurodevelopmental delay in affected infants. Prevention strategies should also target mothers because increased awareness and hygiene measures may reduce maternal infection. Recognition of the importance of CMV in pregnancy and in neonates is increasingly needed, particularly as therapeutic and preventive interventions expand for this serious problem.

Incidence of CMV co-infection in HIV-positive women and their neonates in a tertiary referral centre: a cohort study

Co-infection with CMV in HIV-positive pregnant women is associated with perinatal mother-to-child transmission (MTCT) of both viruses. This retrospective study reports on the incidence of maternal and neonatal CMV (presence of anti-CMV IgG and IgM, CMV DNA PCR and/or CMV virus isolation) in high-risk pregnancies due to maternal HIV infection, MTCT of HIV and/or CMV. One hundred and eleven maternal samples and 75 matched neonatal samples were available for HIV and subsequent CMV testing. In this cohort of HIV-positive pregnant women, 96 (86.5 %) serum samples were anti-CMV IgG positive. In nine (9.4 %) of these, anti-CMV IgM was detected, and in none of them a maternal primary CMV infection was suspected. Fifty-seven (51.8 %) maternal serum samples were tested retrospectively by CMV DNA PCR; one sample was positive (0.9 %). All matched neonates were tested for HIV by PCR in the first month of life; HIV transmission was detected in one case. In 74 (67.2 %) of neonates, CMV testing was performed. Sixty-six of these serum samples were tested retrospectively by CMV DNA PCR. Two newborns (2.7 %) showed laboratory markers for CMV infection (one by detection of CMV DNA in plasma, and one by isolation of CMV from a urine sample). In the follow-up, neither of these two showed clinical signs for active CMV disease. We discussed these findings in the light of the national official guidelines. All CMV transmissions occurred due to maternal reinfection or endogenous reactivation. This suggests the success of highly active antiretroviral therapy in preventing MTCT of HIV and CMV disease and highlights the importance of adequate care and follow-up.

Exploiting viral natural history for vaccine development

The partial successes of the Phase 2 gB-based vaccine trials for HCMV highlight the very real likelihood that vaccine-mediated induction of antibodies that neutralize the fusion pathway of fibroblast infection is not sufficient as a singular strategy to confer protective efficacy against primary HCMV infection. Alternative strategies that serve as adjuncts to gB-based vaccines are likely required to target different aspects of the complex lifecycle of HCMV infection. There has been considerable recent interest in targeting the gH/gL/UL128/UL130/UL131 pentamer complex (gH/gL-PC) to neutralize the endocytic pathway of HCMV infection of epithelial and endothelial cells. Since both cell types are critical during primary mucosal infection, intrahost spread, and shedding of HCMV in an infected host, the gH/gL-PC represents a high-value target for vaccination to interrupt the HCMV lifecycle. The natural history of HCMV is exceedingly complex and incompletely resolved, and the protective efficacy generated by gH/gL-PC remains to be validated in clinical trials. Yet, there are salient aspects of its lifecycle that offer clues about how other novel vaccine strategies can be targeted to especially susceptible parts of the viral proteome to significantly disrupt HCMV's ability to infect susceptible hosts. In particular, the protracted evolution of Herpesvirales has endowed HCMV with two remarkable properties of its natural history: (1) lifelong persistence within immune hosts that develop extraordinarily large antiviral immune responses and (2) the ability to reinfect those with prior immunity. The latter phenotype strongly implies that, if HCMV can overcome prior immunity to initiate a new infection, it is likely irrelevant whether prior immunity derives from prior infection or prior vaccination. Both phenotypes are unified by the extensive devotion of the HCMV coding repertoire (~50%) to viral proteins that modulate host cell signaling, trafficking, activation, antigen presentation, and resistance to apoptosis. Collectively, these viral proteins are the likely reason for the high barrier to success for the 4-decade effort to design an HCMV vaccine, and they represent the viral proteins that make HCMV be the virus that it is. James Hanshaw wrote in 1971 that, based on a 15-year retrospective of congenital HCMV cases, "… any thoughtful program designed at prevention or treatment deserves consideration". Drawing upon natural history data from the nonhuman primate model of HCMV persistence and pathogenesis, a "thoughtful program" is put forth that HCMV immune-modulating proteins should be considered as vaccine candidates.