Glycoprotein B vaccine is capable of boosting both antibody and CD4 T-cell responses to cytomegalovirus in chronically infected women

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.

Cost-effectiveness of cytomegalovirus vaccination for females in China: A decision-analytical Markov study

BACKGROUND

The global burden of disease caused by congenital cytomegalovirus (CMV) infection is high. Previous modeling studies have suggested that CMV vaccination may be cost-effective in developed countries. Congenital CMV infection is more likely driven by maternal non-primary infection in China. We aimed to measure the effectiveness and cost-effectiveness of population-level CMV vaccination in Chinese females.

METHODS

A decision tree Markov model was developed to simulate potential CMV vaccination strategies in a multi-cohort setting, with a population size of 1,000,000 each for the infant, adolescent (10-year-old) and young adult (20-year-old) cohorts. The hypothetical vaccines were assumed to have 50% efficacy, 20 years of protection, 70% coverage, at a price of US$120/dose for base-case analysis. Costs and disability-adjusted life years (DALYs) were discounted by 3% per year and the vaccination would be considered cost-effective if an incremental cost-effectiveness ratio (ICER) was lower than 2021 Chinese per capita GDP (US$12,500).

FINDINGS

For the pre-infection (PRI) vaccine efficacy type, the adolescent strategy was the most cost-effective, with an ICER of US$12,213 (12,134 to 12,291) pre DALY averted, compared with the next best strategy (young adult strategy). For pre- and post-infection (P&PI) efficacy type, the young adult strategy was the most cost-effective as it was cost-saving. In one-way analysis varying the PRI vaccine price, the infant strategy, adolescent strategy and the young adult strategy would be a dominant strategy over others if the vaccine cost ≤US$60, US$61-121 and US$122-251 per dose respectively. In contrast, the young adult strategy continued to be the preferred strategy until the P&PI vaccine price exceeded US$226/dose. Our main results were robust under a wide variety of sensitivity analyses and scenario analyses.

INTERPRETATION

CMV vaccination for females would be cost-effective and even cost-saving in China. Our findings had public health implications for control of CMV diseases.

Congenital Cytomegalovirus and Hearing Loss: The State of the Art

In developed countries, congenital cytomegalovirus (cCMV) infection is the most common congenital viral infection, representing the leading non-genetic cause of sensorineural hearing loss (HL). Diagnosis of cCMV infection can be performed by detection of CMV DNA in urine or saliva within 2-3 weeks after birth, or later in dried blood samples on the Guthrie card. Currently, there are many controversies regarding the preventive, diagnostic, and therapeutic approaches to cCMV infection. HL secondary to cCMV is highly variable in onset, side, degree, audiometric configuration, and threshold changes over time. Therefore, it is of paramount importance to perform a long and thorough audiological follow-up in children with cCMV infection to ensure early identification and prompt treatment of progressive and/or late-onset HL. Early cochlear implantation appears to be a valid solution not only for children with bilateral profound HL, but also for those with single-sided deafness, improving localization ability and understanding speech in noisy environments. Moreover, the decision to apply a unilateral cochlear implant in children with cCMV is strengthened by the non-negligible possibility of hearing deterioration of the contralateral ear over time.

Management of neonatal central nervous system viral infections: Knowledge gaps and research priorities

Congenital CMV, enteroviruses, human parechovirus and herpes simplex virus are all common causes of severe central nervous system (CNS) infection in neonates. The introduction of screening (i.e. newborn hearing screening programme), integration of molecular syndromic testing (i.e. multiplex polymerase chain reaction assays) and increase in sexually transmitted infections (i.e. anogenital herpes) have contributed to increases in each of these infections over the last decade. However, therapeutic options are highly limited in part due to the lack of epidemiological data informing trials. This review will describe our current understanding of the clinical burden and epidemiology of these severe neonatal CNS infections, outline the novel antiviral and vaccines in the pipeline and suggest future research studies which could help develop new therapeutics.

A bivalent CMV vaccine formulated with human compatible TLR9 agonist CpG1018 elicits potent cellular and humoral immunity in HLA expressing mice

There is now convincing evidence that the successful development of an effective CMV vaccine will require improved formulation and adjuvant selection that is capable of inducing both humoral and cellular immune responses. Here, we have designed a novel bivalent subunit vaccine formulation based on CMV-encoded oligomeric glycoprotein B (gB) and polyepitope protein in combination with human compatible TLR9 agonist CpG1018. The polyepitope protein includes multiple minimal HLA class I-restricted CD8⁺ T cell epitopes from different antigens of CMV. This subunit vaccine generated durable anti-viral antibodies, CMV-specific CD4⁺ and CD8⁺ T cell responses in multiple HLA expressing mice. Antibody responses included broad T_H1 isotypes (IgG2a, IgG2b and IgG3) and potently neutralized CMV infection in fibroblasts and epithelial cells. Furthermore, polyfunctional antigen-specific T cell immunity and antiviral antibody responses showed long-term memory maintenance. These observations argue that this novel vaccine strategy, if applied to humans, could facilitate the generation of robust humoral and cellular immune responses which may be more effective in preventing CMV-associated complications in various clinical settings.

Human Cytomegalovirus (CMV) is a significant human pathogen. Generally, in healthy people CMV causes mild symptomatic disease, but during pregnancy CMV can transmit from mother to foetus (1 out of every 200 live births worldwide) and lead to sensorineural hearing loss, vision impairment and central nervous system damage. In transplant patients, CMV can cause serious complications leading to organ rejection and even death. Currently, there is no licensed vaccine available to prevent CMV-associated complications in pregnant women and transplant patients. Here, we have developed a novel bivalent CMV vaccine formulation consisting of recombinant CMVpoly and gB proteins in combination with human compatible adjuvant CpG1018. Preclinical immunogenicity evaluation in multiple HLA expressing mice demonstrated that bivalent CMV vaccine formulation consistently generated robust CMV-specific neutralising antibodies, CD4⁺ and CD8⁺ T cell responses. More importantly, long-term follow-up analysis showed that the CMV vaccine can induce durable CMV-specific humoral and cellular immune responses. Our results support further development of this bivalent subunit CMV vaccine to test safety, immunogenicity and efficacy in humans.

Dominant Antiviral CD8+ T Cell Responses Empower Prophylactic Antibody-Eliciting Vaccines Against Cytomegalovirus

Human cytomegalovirus (HCMV) is an ubiquitous herpesvirus that can cause serious morbidity and mortality in immunocompromised or immune-immature individuals. A vaccine that induces immunity to CMV in these target populations is therefore highly needed. Previous attempts to generate efficacious CMV vaccines primarily focused on the induction of humoral immunity by eliciting neutralizing antibodies. Current insights encourage that a protective immune response to HCMV might benefit from the induction of virus-specific T cells. Whether addition of antiviral T cell responses enhances the protection by antibody-eliciting vaccines is however unclear. Here, we assessed this query in mouse CMV (MCMV) infection models by developing synthetic vaccines with humoral immunity potential, and deliberately adding antiviral CD8⁺ T cells. To induce antibodies against MCMV, we developed a DNA vaccine encoding either full-length, membrane bound glycoprotein B (gB) or a secreted variant lacking the transmembrane and intracellular domain (secreted (s)gB). Intradermal immunization with an increasing dose schedule of sgB and booster immunization provided robust viral-specific IgG responses and viral control. Combined vaccination of the sgB DNA vaccine with synthetic long peptides (SLP)-vaccines encoding MHC class I-restricted CMV epitopes, which elicit exclusively CD8⁺ T cell responses, significantly enhanced antiviral immunity. Thus, the combination of antibody and CD8⁺ T cell-eliciting vaccines provides a collaborative improvement of humoral and cellular immunity enabling enhanced protection against CMV.

Cytomegalovirus Infections in Children with Primary and Secondary Immune Deficiencies

Cytomegalovirus (CMV) is a human herpes virus that causes significant morbidity and mortality in immunosuppressed children. CMV primary infection causes a clinically mild disease in healthy children, usually in early childhood; the virus then utilises several mechanisms to establish host latency, which allows for periodic reactivation, particularly when the host is immunocompromised. It is this reactivation that is responsible for the significant morbidity and mortality in immunocompromised children. We review CMV infection in the primary immunodeficient host, including early identification of these infants by newborn screening to allow for CMV infection prevention strategies. Furthermore, clinical CMV is discussed in the context of children treated with secondary immunodeficiency, particularly paediatric cancer patients and children undergoing haematopoietic stem cell transplant (HSCT). Treatments for CMV are highlighted and include CMV immunotherapy.

Congenital Human Cytomegalovirus Infection: A Narrative Review of Maternal Immune Response and Diagnosis in View of the Development of a Vaccine and Prevention of Primary and Non-Primary Infections in Pregnancy

Congenital cytomegalovirus infection (cCMV) may affect about 1% of all newborns all over the world as a result of either a primary or recurrent human cytomegalovirus (HCMV) infection. While about 90% of infants affected by cCMV are asymptomatic at birth, the remaining 10% are symptomatic often with neurodevelopmental impairment and sensorineural hearing loss. In view of identifying the best approach to vaccine prevention of cCMV, this review will examine the most important steps made in the study of the immune response to, and diagnosis of, HCMV infection. The maternal immune response and immune correlates of protection are being partially identified with a partial contribution given by our laboratory. The diagnosis of primary infection is often difficult to achieve in the first three months of pregnancy, which is the time primarily involved in virus transmission to the fetus in association with the most severe symptoms and sequelae. Prevention of cCMV is anticipated by prevention of primary infection in early pregnancy by means of different measures, such as (i) behavioral-educational measures, (ii) immunoglobulin administration, (iii) antiviral treatment with valaciclovir. However, the most promising approach to cCMV prevention appears to be the development of a non-living vaccine, including at least three viral antigens: gB, pentamer complex gHgLpUL128L, and pp65, which have been shown to be able to stimulate both the humoral and the cellular arms of the maternal immune response. Primary HCMV infection may be managed in pregnancy by counseling of the couples involved by a team of specialists that includes virologists, obstetricians, infectivologists and neonatologists.

Immune Prophylaxis and Therapy for Human Cytomegalovirus Infection

Human Cytomegalovirus (HCMV) infection is widespread and can result in severe sequelae in susceptible populations. Primary HCMV infection of naïve individuals results in life-long latency characterized by frequent and sporadic reactivations. HCMV infection elicits a robust antibody response, including neutralizing antibodies that can block the infection of susceptible cells in vitro and in vivo. Thus, antibody products and vaccines hold great promise for the prevention and treatment of HCMV, but to date, most attempts to demonstrate their safety and efficacy in clinical trials have been unsuccessful. In this review we summarize publicly available data on these products and highlight new developments and approaches that could assist in successful translation of HCMV immunotherapies.

Development of a Vaccine against Human Cytomegalovirus: Advances, Barriers, and Implications for the Clinical Practice

Human cytomegalovirus (hCMV) is one of the most common causes of congenital infection in the post-rubella era, representing a major public health concern. Although most cases are asymptomatic in the neonatal period, congenital CMV (cCMV) disease can result in permanent impairment of cognitive development and represents the leading cause of non-genetic sensorineural hearing loss. Moreover, even if hCMV mostly causes asymptomatic or pauci-symptomatic infections in immunocompetent hosts, it may lead to severe and life-threatening disease in immunocompromised patients. Since immunity reduces the severity of disease, in the last years, the development of an effective and safe hCMV vaccine has been of great interest to pharmacologic researchers. Both hCMV live vaccines-e.g., live-attenuated, chimeric, viral-based-and non-living ones-subunit, RNA-based, virus-like particles, plasmid-based DNA-have been investigated. Encouraging data are emerging from clinical trials, but a hCMV vaccine has not been licensed yet. Major difficulties in the development of a satisfactory vaccine include hCMV's capacity to evade the immune response, unclear immune correlates for protection, low number of available animal models, and insufficient general awareness. Moreover, there is a need to determine which may be the best target populations for vaccine administration. The aim of the present paper is to examine the status of hCMV vaccines undergoing clinical trials and understand barriers limiting their development.

Prevention of Congenital Cytomegalovirus Infection with Vaccines: State of the Art

Cytomegalovirus (CMV) is the most common cause of congenital infection and non-genetic sensorineural hearing loss in childhood. Up to 2% of neonates, with the highest percentages found in developing countries, are congenitally infected with CMV. At birth, most of these infants are asymptomatic. However, approximately 10% have signs and symptoms of the disease, and 40–60% of symptomatic neonates will later develop permanent neurologic sequelae. To reduce congenital CMV (cCMV) infection, a vaccine able to prevent primary infection is essential. In this narrative review, actual ongoing research about the development of a CMV vaccine is discussed. The progressive increase in knowledge on the ways in which the host’s immune system and CMV relate has made it possible to clarify that the development of a vaccine that is certainly capable of reducing the risk of cCMV infection, and preventing both primary and nonprimary infections is extremely difficult. Many of the ways in which the virus evades the immune system and causes cCMV infection are not yet fully understood, especially in cases of nonprimary infection. Moreover, the schedule that should be recommended and that subjects must be vaccinated to obtain the greatest effect have not been precisely defined. Further studies are needed before the problem of cCMV infection and its related challenges can be totally solved.

IgA binds to the AD-2 epitope of glycoprotein B and neutralizes human cytomegalovirus

Human cytomegalovirus (HCMV) is a ubiquitous pathogen that is potentially pathogenic in immunosuppressed individuals and pregnant females during primary infection. The HCMV envelope glycoprotein B (gB) facilitates viral entry into all cell types and induces a potent immune response. AD-2 epitope is a highly conserved linear neutralizing epitope of gB and a critical target for antibodies; however, only 50% of sero-positive individuals make IgG antibodies to this site and IgA responses have not been fully investigated. This study aimed to compare IgG and IgA responses against gB and the AD-2 epitope in naturally exposed individuals and those receiving a recombinant gB/MF59 adjuvant vaccine. Thus, vaccination of sero-positive individuals improved pre-existing gB-specific IgA and IgG levels and induced de novo gB-specific IgA and IgG responses in sero-negative recipients. Pre-existing AD-2 IgG and IgA responses were boosted with vaccination, but de novo AD-2 responses were not detected. Naturally exposed individuals had dominant IgG responses towards gB and AD-2 compared with weaker and variable IgA responses, although a significant IgA binding response to AD-2 was observed within human breastmilk samples. All antibodies binding AD-2 contained kappa light chains, whereas balanced kappa/lambda light chain usage was found for those binding to gB. V region-matched AD-2-specific recombinant IgG and IgA bound both to gB and to AD-2 and neutralized HCMV infection in vitro. Overall, these results indicate that although human IgG responses dominate, IgA class antibodies against AD-2 are a significant component of human milk, which may function to protect neonates from HCMV.

The Status of Vaccine Development Against the Human Cytomegalovirus

Numerous candidate vaccines against cytomegalovirus (CMV) infection and disease are in development. Whereas the previous article [1] provides background and opinions about the issues relating to vaccination, this article provides specifics about the vaccines in active development, as reported at a National Institutes of Health-sponsored meeting in Bethesda on September 4-6, 2018. Here, vaccine developers provide synopses of their candidate vaccines to immunize women to protect against congenital CMV disease and to prevent the consequences of CMV disease in recipients of transplanted organs or hematopoietic stem calls. The projects are presented here roughly in the descending order of their stage of development in the opinion of the first author.

Review of Mathematical Models of Vaccination for Preventing Congenital Cytomegalovirus Infection

BACKGROUND

Several cytomegalovirus (CMV) vaccine candidates are under development. To reduce the burden of congenital CMV infection, potential strategies under consideration include vaccination of adult women, adolescent girls, and/or young children (both sexes).

METHODS

We reviewed 5 studies that used infectious disease modeling to assess the potential impact of vaccination for preventing congenital CMV infection. All models assumed CMV vaccination would prevent primary infection and 2 models also assumed prevention of reinfections and reactivations.

RESULTS

Despite differences in structure, assumptions, and population data, infant vaccination (both sexes) was the optimal strategy in all models, but in 1 model vaccinating seronegative women at 19-21 years of age was also optimal (for duration of vaccine protection ≥8 years). In 3 models, infant vaccination increased average age at primary infection as a result of decreased secondary transmission (herd immunity) combined with waning vaccine-induced immunity. This effect could increase the risk of congenital CMV infections in populations where primary CMV infection occurs early in childhood but could be minimized by administering a second dose of vaccine during adolescence.

CONCLUSIONS

Understanding vaccine efficacy and duration of immunity, and how these might vary depending on CMV serostatus and age at vaccination, will be key to defining CMV vaccination strategies.

Preventing Infection by Human Cytomegalovirus

The way to a successful vaccine against human cytomegalovirus is hampered by the peculiar biology of this infection. However, some candidate vaccines have been shown to protect seronegative women and transplant recipients, and we should know soon whether they can prevent congenital infection.

Recent Approaches and Strategies in the Generation of Anti-human Cytomegalovirus Vaccines

Human cytomegalovirus is the largest human herpesvirus and shares many core features of other herpesviruses such as tightly regulated gene expression during genome replication and latency as well as the establishment of lifelong persistence following infection. In contrast to stereotypic clinical syndromes associated with alpha-herpesvirus infections, almost all primary HCMV infections are asymptomatic and acquired early in life in most populations in the world. Although asymptomatic in most individuals, HCMV is a major cause of disease in hosts with deficits in adaptive and innate immunity such as infants who are infected in utero and allograft recipients following transplantation. Congenital HCMV is a commonly acquired infection in the developing fetus that can result in a number of neurodevelopmental abnormalities. Similarly, HCMV is a major cause of disease in allograft recipients in the immediate and late posttransplant period and is thought to be a major contributor to chronic allograft rejection. Even though HCMV induces robust innate and adaptive immune responses, it also encodes a vast array of immune evasion functions that are thought aid in its persistence. Immune correlates of protective immunity that prevent or modify intrauterine HCMV infection remain incompletely defined but are thought to consist primarily of adaptive responses in the pregnant mother, thus making congenital HCMV a potentially vaccine modifiable disease. Similarly, HCMV infection in allograft recipients is often more severe in recipients without preexisting adaptive immunity to HCMV. Thus, there has been a considerable effort to modify HCMV specific immunity in transplant recipient either through active immunization or passive transfer of adaptive effector functions. Although efforts to develop an efficacious vaccine and/or passive immunotherapy to limit HCMV disease have been underway for nearly six decades, most have met with limited success at best. In contrast to previous efforts, current HCMV vaccine development has relied on observations of unique properties of HCMV in hopes of reproducing immune responses that at a minimum will be similar to that following natural infection. However, more recent findings have suggested that immunity following naturally acquired HCMV infection may have limited protective activity and almost certainly, is not sterilizing. Such observations suggest that either the induction of natural immunity must be specifically tailored to generate protective activity or alternatively, that providing targeted passive immunity to susceptible populations could be prove to be more efficacious.

Vaccines for Perinatal and Congenital Infections-How Close Are We?

Congenital and perinatal infections are transmitted from mother to infant during pregnancy across the placenta or during delivery. These infections not only cause pregnancy complications and still birth, but also result in an array of pediatric morbidities caused by physical deformities, neurodevelopmental delays, and impaired vision, mobility and hearing. Due to the burden of these conditions, congenital and perinatal infections may result in lifelong disability and profoundly impact an individual's ability to live to their fullest capacity. While there are vaccines to prevent congenital and perinatal rubella, varicella, and hepatitis B infections, many more are currently in development at various stages of progress. The spectrum of our efforts to understand and address these infections includes observational studies of natural history of disease, epidemiological evaluation of risk factors, immunogen design, preclinical research of protective immunity in animal models, and evaluation of promising candidates in vaccine trials. In this review we summarize this progress in vaccine development research for Cytomegalovirus, Group B Streptococcus, Herpes simplex virus, Human Immunodeficiency Virus, Toxoplasma, Syphilis, and Zika virus congenital and perinatal infections. We then synthesize this evidence to examine how close we are to developing a vaccine for these infections, and highlight areas where research is still needed.

Current perspective and scope of fetal therapy: part 2

Fetal therapy has been defined as any therapeutic intervention either invasive or noninvasive for correcting or treating any fetal malformation or condition. Invasive fetal therapy have its own set of maternal and fetal complications and invasive approach is not feasible in many of fetal conditions that are candidate for fetal therapy. Many such fetal conditions have been treated successfully by medical or noninvasive management. In medical fetal therapy, mothers are treated with medications which are transferred to fetus through placenta and exert positive effect on the fetus, thus avoiding complications that are seen secondary to invasive fetal therapy. The fetal conditions that have been managed with medical therapy includes fetal and neonatal alloimmune thrombocytopenia, neural tube defect, congenital adrenal hyperplasia, perinatal infections, respiratory distress syndrome, inborn error of metabolism, and congenital cystic adenomatoid malformation. This review will cover the medical or noninvasive aspect of fetal therapy and will highlight the progress made in the management of these fetal conditions.

Congenital Cytomegalovirus Infection: Update on Diagnosis and Treatment

Congenital cytomegalovirus (cCMV) infection is the most common congenital viral infection and is the leading non-genetic cause of sensorineural hearing loss (SNLH) and an important cause of neurodevelopmental disabilities. The risk of intrauterine transmission is highest when primary infection occurs during pregnancy, with a higher rate of vertical transmission in mothers with older gestational age at infection, while the risk of adverse fetal effects significantly increases if fetal infection occurs during the first half of pregnancy. Despite its prevalence and morbidity among the neonatal population, there is not yet a standardized diagnostic test and therapeutic approach for cCMV infection. This narrative review aims to explore the latest developments in the diagnosis and treatment of cCMV infection. Literature analysis shows that preventive interventions other than behavioral measures during pregnancy are still lacking, although many clinical trials are currently ongoing to formulate a vaccination for women before pregnancy. Currently, we recommend using a PCR assay in blood, urine, and saliva in neonates with suspected cCMV infection. At present, there is no evidence of the benefit of antiviral therapy in asymptomatic infants. In the case of symptomatic cCMV, we actually recommend treatment with oral valganciclovir for a duration of 12 months. The effectiveness and tolerability of this therapy option have proven effective for hearing and neurodevelopmental long-term outcomes. Valganciclovir is reserved for congenitally-infected neonates with the symptomatic disease at birth, such as microcephaly, intracranial calcifications, abnormal cerebrospinal fluid index, chorioretinitis, or sensorineural hearing loss. Treatment with antiviral drugs is not routinely recommended for neonates with the mildly symptomatic disease at birth, for neonates under 32 weeks of gestational age, or for infants more than 30 days old because of insufficient evidence from studies. However, since these populations represent the vast majority of neonates and infants with cCMV infection and they are at risk of developing late-onset sequelae, a biomarker able to predict long-term sequelae should also be found to justify starting treatment and reducing the burden of CMV-related complications.

The tetraspanin CD151 marks a unique population of activated human T cells

Tetraspanins are a family of proteins with an array of functions that are well studied in cancer biology, but their importance in immunology is underappreciated. Here we establish the tetraspanin CD151 as a unique marker of T-cell activation and, in extension, an indicator of elevated, systemic T-cell activity. Baseline CD151 expression found on a subset of T-cells was indicative of increased activation of the MAPK pathway. Following TCR/CD3 activation, CD151 expression was upregulated on the overall T-cell population, a quintessential feature of an activation marker. CD151+ T-cell frequencies in the spleen, an organ with increased immune activity, were twice as high as in paired peripheral blood samples. This CD151+ T-cell frequency increase was not paralleled by an increase of CD25 or CD38, demonstrating that CD151 expression is regulated independently of other T-cell activation markers. CD151+ T-cells were also more likely to express preformed granzyme B, suggesting that CD151+ T cells are pro-inflammatory. To this end, HIV-1 patients on antiretroviral therapy who are reported to exhibit chronically elevated levels of immune activity, had significantly higher CD4+CD151+ T-cell frequencies than healthy controls, raising the possibility that proinflammatory CD151+ T cells could contribute to the premature immunological aging phenotype observed in these patients.

The CD4+ T Cell Response to Human Cytomegalovirus in Healthy and Immunocompromised People

While CD8+ T cells specific for human cytomegalovirus (HCMV) have been extensively studied in both healthy HCMV seropositive carriers and patients undergoing immunosuppression, studies on the CD4+ T cell response to HCMV had lagged behind. However, over the last few years there has been a significant advance in our understanding of the importance and contribution that CMV-specific CD4+ T cells make, not only to anti-viral immunity but also in the potential maintenance of latently infected cells. During primary infection with HCMV in adults, CD4+ T cells are important for the resolution of symptomatic disease, while persistent shedding of HCMV into urine and saliva is associated with a lack of HCMV specific CD4+ T cell response in young children. In immunosuppressed solid organ transplant recipients, a delayed appearance of HCMV-specific CD4+ T cells is associated with prolonged viremia and more severe clinical disease, while in haematopoietic stem cell transplant recipients, it has been suggested that HCMV-specific CD4+ T cells are required for HCMV-specific CD8+ T cells to exert their anti-viral effects. In addition, adoptive T-cell immunotherapy in transplant patients has shown that the presence of HCMV-specific CD4+ T cells is required for the maintenance of HCMV-specific CD8+ T cells. HCMV is a paradigm for immune evasion. The presence of viral genes that down-regulate MHC class II molecules and the expression of viral IL-10 both limit antigen presentation to CD4+ T cells, underlining the important role that this T cell subset has in antiviral immunity. This review will discuss the antigen specificity, effector function, phenotype and direct anti-viral properties of HCMV specific CD4+ T cells, as well as reviewing our understanding of the importance of this T cell subset in primary infection and long-term carriage in healthy individuals. In addition, their role and importance in congenital HCMV infection and during immunosuppression in both solid organ and haemopoietic stem cell transplantation is considered.

Human Cytomegalovirus Congenital (cCMV) Infection Following Primary and Nonprimary Maternal Infection: Perspectives of Prevention through Vaccine Development

Congenital cytomegalovirus (cCMV) might occur as a result of the human cytomegalovirus (HCMV) primary (PI) or nonprimary infection (NPI) in pregnant women. Immune correlates of protection against cCMV have been partly identified only for PI. Following either PI or NPI, HCMV strains undergo latency. From a diagnostic standpoint, while the serological criteria for the diagnosis of PI are well-established, those for the diagnosis of NPI are still incomplete. Thus far, a recombinant gB subunit vaccine has provided the best results in terms of partial protection. This partial efficacy was hypothetically attributed to the post-fusion instead of the pre-fusion conformation of the gB present in the vaccine. Future efforts should be addressed to verify whether a new recombinant gB pre-fusion vaccine would provide better results in terms of prevention of both PI and NPI. It is still a matter of debate whether human hyperimmune globulin are able to protect from HCMV vertical transmission. In conclusion, the development of an HCMV vaccine that would prevent a significant portion of PI would be a major step forward in the development of a vaccine for both PI and NPI.

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.

Immunization with Human Cytomegalovirus Core Fusion Machinery and Accessory Envelope Proteins Elicit Strong Synergistic Neutralizing Activities

Human cytomegalovirus (HCMV) core fusion machinery proteins gB and gH/gL, and accessory proteins UL128/UL130/UL131A, are the key envelope proteins that mediate HCMV entry into and infection of host cells. To determine whether these HCMV envelope proteins could elicit neutralizing activities synergistically, we immunized rabbits with individual or various combinations of these proteins adsorbed to aluminum hydroxide mixed with CpG-ODN. We then analyzed serum neutralizing activities with multiple HCMV laboratory strains and clinical isolates. HCMV trimeric gB and gH/gL elicited high and moderate titers of HCMV neutralizing activity, respectively. HCMV gB in combination with gH/gL elicited up to 17-fold higher HCMV neutralizing activities compared to the sum of neutralizing activity elicited by the individual proteins analyzed with both fibroblasts and epithelial cells. HCMV gB+gH/gL+UL128/UL130/UL131A in combination increased the neutralizing activity up to 32-fold compared to the sum of neutralizing activities elicited by the individual proteins analyzed with epithelial cells. Adding UL128/UL130/UL131A to gB and gH/gL combination did not increase further the HCMV neutralizing activity analyzed with fibroblasts. These data suggest that the combination of HCMV core fusion machinery envelope proteins gB+gH/gL or the combination of gB and pentameric complex could be ideal vaccine candidates that would induce optimal immune responses against HCMV infection.

Computational assembly of a human Cytomegalovirus vaccine upon experimental epitope legacy

Background

Human Cytomegalovirus (HCMV) is a ubiquitous herpesvirus affecting approximately 90% of the world population. HCMV causes disease in immunologically naive and immunosuppressed patients. The prevention, diagnosis and therapy of HCMV infection are thus crucial to public health. The availability of effective prophylactic and therapeutic treatments remain a significant challenge and no vaccine is currently available. Here, we sought to define an epitope-based vaccine against HCMV, eliciting B and T cell responses, from experimentally defined HCMV-specific epitopes.

Results

We selected 398 and 790 experimentally validated HCMV-specific B and T cell epitopes, respectively, from available epitope resources and apply a knowledge-based approach in combination with immunoinformatic predictions to ensemble a universal vaccine against HCMV. The T cell component consists of 6 CD8 and 6 CD4 T cell epitopes that are conserved among HCMV strains. All CD8 T cell epitopes were reported to induce cytotoxic activity, are derived from early expressed genes and are predicted to provide population protection coverage over 97%. The CD4 T cell epitopes are derived from HCMV structural proteins and provide a population protection coverage over 92%. The B cell component consists of just 3 B cell epitopes from the ectodomain of glycoproteins L and H that are highly flexible and exposed to the solvent.

Conclusions

We have defined a multiantigenic epitope vaccine ensemble against the HCMV that should elicit T and B cell responses in the entire population. Importantly, although we arrived to this epitope ensemble with the help of computational predictions, the actual epitopes are not predicted but are known to be immunogenic.

MVA-Vectored Pentameric Complex (PC) and gB Vaccines Improve Pregnancy Outcome after Guinea Pig CMV Challenge, but Only gB Vaccine Reduces Vertical Transmission

(1) Background: A congenital cytomegalovirus (cCMV) vaccine is a major research priority, but the essential glycoprotein target(s) remain unclear. We compared CMV gB (gpgB), gH/gL (gp75/gL), and pentameric complex (gpPC, composed of gH/gL/GP129/GP131/GP133) vaccines in a guinea pig CMV (GPCMV) congenital infection model. (2) Methods: Modified vaccinia virus Ankara (MVA) vaccines expressing GPCMV glycoproteins were used to immunize GPCMV-seronegative, female Hartley guinea pigs (three-dose series, 3 × 10⁷ pfu/dose). After pregnancy was established, the dams underwent an early third-trimester challenge with salivary gland (SG)-adapted GPCMV. (3) Results: All vaccines elicited GPCMV-specific binding and neutralizing antibodies. Preconception immunization resulted in 19.5-, 4.9-, and 698-fold reductions in maternal DNAemia in MVA-gp75/gL, MVA-gpPC and MVA-gpgB groups, respectively, at day 14, post-SG challenge. Vaccination improved pups’ birth weight and reduced mortality and congenital CMV transmission. In controls, cCMV infection was observed in 100% of pups (mean viral load in all visceral organs, 2.4 × 10⁴ genomes/mg), versus 50% in the gB group (visceral viral load, 9.4 × 10² genomes/mg; p < 0.05). No significant reductions in congenital transmission were noted in the MVA-gp75/gL and MVA-gpPC groups. (4) Conclusions: MVA-vectored gB, gH/gL, and PC vaccines were immunogenic, and protected against maternal DNAemia and pup mortality. These results support the inclusion of multiple glycoprotein complexes in a cCMV vaccine.

Advances in the treatment of cytomegalovirus

BACKGROUND

Human cytomegalovirus (HCMV) is a threat to immunologically weak patients. HCMV cannot yet be eliminated with a vaccine, despite recent advances.

SOURCES OF DATA

Sources of data are recently published research papers and reviews about HCMV treatments.

AREAS OF AGREEMENT

Current antivirals target the UL54 DNA polymerase and are limited by nephrotoxicity and viral resistance. Promisingly, letermovir targets the HCMV terminase complex and has been recently approved by the FDA and EMA.

AREAS OF CONTROVERSY

Should we screen newborns for HCMV, and use antivirals to treat sensorineural hearing loss after congenital HCMV infection?

GROWING POINTS

Growing points are developing drugs against latently infected cells. In addition to small molecule inhibitors, a chemokine-based fusion toxin protein, F49A-FTP, has shown promise in killing both lytically and latently infected cells.

AREAS TIMELY FOR DEVELOPING RESEARCH

We need to understand what immune responses are required to control HCMV, and how best to raise these immune responses with a vaccine.

Epitope-Specific Humoral Responses to Human Cytomegalovirus Glycoprotein-B Vaccine With MF59: Anti-AD2 Levels Correlate With Protection From Viremia

The human cytomegalovirus (HCMV) virion envelope protein glycoprotein B (gB) is essential for viral entry and represents a major target for humoral responses following infection. Previously, a phase 2 placebo-controlled clinical trial conducted in solid organ transplant candidates demonstrated that vaccination with gB plus MF59 adjuvant significantly increased gB enzyme-linked immunosorbent assay (ELISA) antibody levels whose titer correlated directly with protection against posttransplant viremia. The aim of the current study was to investigate in more detail this protective humoral response in vaccinated seropositive transplant recipients. We focused on 4 key antigenic domains (AD) of gB (AD1, AD2, AD4, and AD5), measuring antibody levels in patient sera and correlating these with posttransplant HCMV viremia. Vaccination of seropositive patients significantly boosted preexisting antibody levels against the immunodominant region AD1 as well as against AD2, AD4, and AD5. A decreased incidence of viremia correlated with higher antibody levels against AD2 but not with antibody levels against the other 3 ADs. Overall, these data support the hypothesis that antibodies against AD2 are a major component of the immune protection of seropositives seen following vaccination with gB/MF59 vaccine and identify a correlate of protective immunity in allograft patients.

Immunization of Rabbits with Recombinant Human Cytomegalovirus Trimeric versus Monomeric gH/gL Protein Elicits Markedly Higher Titers of Antibody and Neutralization Activity

Congenital human cytomegalovirus (HCMV) infection and HCMV infection of immunosuppressed patients cause significant morbidity and mortality, and vaccine development against HCMV is a major public health priority. HCMV envelope glycoproteins gB, gH, and gL, which constitute the core fusion machinery, play critical roles in HCMV fusion and entry into host cells. HCMV gB and gH/gL have been reported to elicit potent neutralizing antibodies. Recently, the gB/gH/gL complex was identified in the envelope of HCMV virions, and 16–50% of the total gH/gL bound to gB, forming the gB/gH/gL complex. These findings make the gB/gH/gL a unique HCMV vaccine candidate. We previously reported the production of HCMV trimeric gB and gH/gL heterodimers, and immunization with a combination of trimeric gB and gH/gL heterodimers elicited strong synergistic HCMV-neutralizing activity. To further improve the immunogenicity of gH/gL, we produced trimeric gH/gL. Rabbits immunized with HCMV trimeric gH/gL induced up to 38-fold higher serum titers of gH/gL-specific IgG relative to HCMV monomeric gH/gL, and elicited ~10-fold higher titers of complement-dependent and complement-independent HCMV-neutralizing activity for both epithelial cells and fibroblasts. HCMV trimeric gH/gL in combination with HCMV trimeric gB would be a novel promising HCMV vaccine candidate that could induce highly potent neutralizing activities.

Development of novel vaccines against human cytomegalovirus

Congenital human cytomegalovirus (HCMV) infection and HCMV infection of the immunosuppressed patients cause significant morbidity and mortality, and vaccine development against HCMV is a major public health priority. Efforts to develop HCMV vaccines have been ongoing for 50 y, though no HCMV vaccine has been licensed; encouraging and promising results have obtained from both preclinical and clinical trials. HCMV infection induces a wide range of humoral and T cell-mediated immune responses, and both branches of immunity are correlated with protection. In recent years, there have been novel approaches toward the development of HCMV vaccines and demonstrated that vaccine candidates could potentially provide superior protection over natural immunity acquired following HCMV infection. Further, rationally designed HCMV protein antigens that express native conformational epitopes could elicit optimal immune response. HCMV vaccine candidates, using a multi-antigen approach, to maximize the elicited protective immunity will most likely be successful in development of HCMV vaccine.

Estimation of the worldwide seroprevalence of cytomegalovirus: A systematic review and meta-analysis

Cytomegalovirus (CMV) infection does not usually produce symptoms when it causes primary infection, reinfection, or reactivation because these three types of infection are all controlled by the normal immune system. However, CMV becomes an important pathogen in individuals whose immune system is immature or compromised, such as the unborn child. Several vaccines against CMV are currently in clinical trials that aim to induce immunity in seronegative individuals and/or to boost the immunity of those with prior natural infection (seropositives). To facilitate estimation of the burden of disease and the need for vaccines that induce de novo immune responses or that boost pre-existing immunity to CMV, we conducted a systematic survey of the published literature to describe the global seroprevalence of CMV IgG antibodies. We estimated a global CMV seroprevalence of 83% (95%UI: 78-88) in the general population, 86% (95%UI: 83-89) in women of childbearing age, and 86% (95%UI: 82-89) in donors of blood or organs. For each of these three groups, the highest seroprevalence was seen in the World Health Organisation (WHO) Eastern Mediterranean region 90% (95%UI: 85-94) and the lowest in WHO European region 66% (95%UI: 56-74). These estimates of the worldwide CMV distribution will help develop national and regional burden of disease models and inform future vaccine development efforts.

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.

A new era in cytomegalovirus vaccinology: considerations for rational design of next-generation vaccines to prevent congenital cytomegalovirus infection

Human cytomegalovirus (HCMV), a member of the beta-herpesvirus family, is the most common cause of congenital infection worldwide as well as an important cause of morbidity in transplant recipients and immunosuppressed individuals. An estimated 1 in 150 infants are infected with HCMV at birth, which can result in lifelong, debilitating neurologic sequelae including microcephaly, sensorineural hearing loss, and cognitive impairment. Natural maternal immunity to HCMV decreases the frequency of reinfection and reduces risk of congenital transmission but does not completely protect against neonatal disease. Thus, a vaccine to reduce the incidence and severity of infant infection is a public health priority. A variety of candidate HCMV vaccine approaches have been tried previously, including live-attenuated viruses, glycoprotein subunit formulations, viral vectors, and single/bivalent DNA plasmids, but all have failed to reach target endpoints in clinical trials. Nevertheless, there is a great deal to be learned from the successes and failures of the HCMV vaccine field (both congenital and transplant-associated), as well as from vaccine development efforts for other herpesvirus pathogens including herpes simplex virus 1 and 2, varicella zoster virus, and Epstein-Barr virus. Here, we review those successes and failures, evaluating recent cutting-edge discoveries that have shaped the HCMV vaccine field and identifying topics of critical importance for future investigation. These considerations will inform rational design and evaluation of next-generation vaccines to prevent HCMV-associated congenital infection and disease.

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.

HCMV glycoprotein B subunit vaccine efficacy mediated by nonneutralizing antibody effector functions

Human cytomegalovirus (HCMV) is the most common congenital infection worldwide, frequently causing hearing loss and brain damage in afflicted infants. A vaccine to prevent maternal acquisition of HCMV during pregnancy is necessary to reduce the incidence of infant disease. The glycoprotein B (gB) + MF59 adjuvant subunit vaccine platform is the most successful HCMV vaccine tested to date, demonstrating ∼50% efficacy in preventing HCMV acquisition in multiple phase 2 trials. However, the mechanism of vaccine protection remains unknown. Plasma from 33 postpartum women gB/MF59 vaccinees at peak immunogenicity was tested for gB epitope specificity as well as neutralizing and nonneutralizing anti-HCMV effector functions and compared with an HCMV-seropositive cohort. gB/MF59 vaccination elicited IgG responses with gB-binding magnitude and avidity comparable to natural infection. Additionally, IgG subclass distribution was similar with predominant IgG1 and IgG3 responses induced by gB vaccination and HCMV infection. However, vaccine-elicited antibodies exhibited limited neutralization of the autologous virus, negligible neutralization of multiple heterologous strains, and limited binding responses against gB structural motifs targeted by neutralizing antibodies including AD-1, AD-2, and domain I. Vaccinees had high-magnitude IgG responses against AD-3 linear epitopes, demonstrating immunodominance against this nonneutralizing, cytosolic region. Finally, vaccine-elicited IgG robustly bound membrane-associated gB on the surface of transfected or HCMV-infected cells and mediated virion phagocytosis, although were poor mediators of NK cell activation. Altogether, these data suggest that nonneutralizing antibody functions, including virion phagocytosis, likely played a role in the observed 50% vaccine-mediated protection against HCMV acquisition.

Breast Milk Human Cytomegalovirus (CMV) Viral Load and the Establishment of Breast Milk CMV-pp65-Specific CD8 T Cells in Human CMV Infected Mothers

The role of human cytomegalovirus (HCMV)-specific T-cell responses in breast milk of HCMV-seropositive mothers is not well defined. In these studies, we demonstrate that the frequency of cytomegalovirus (CMV)-pp65-specific T-cell responses in peripheral blood mononuclear cells (PBMCs) and breast milk cells (BMCs) is increased for CD8+ T cells in both sample sources when compared with CD4+ T cells. The frequency of pp55-specific CD8 T cells producing interferon γ (IFN-γ) alone or dual IFN-γ/granzyme rB producers is increased in breast milk compared with PBMCs. Lastly, we observed a positive correlation between breast milk viral load and the CD8 pp65-specific response, suggesting that local virus replication drives antigen-specific CD8 T cells into the breast.

Progress toward Development of a Vaccine against Congenital Cytomegalovirus Infection

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

Human cytomegalovirus vaccine development: Immune responses to look into vaccine strategy

Human cytomegalovirus (HCMV) causes considerable morbidity and disability in high risk, immunocompromised populations including recipients of solid organ transplants, and fetuses whose immune systems are not yet mature. Vaccines aimed at ameliorating the severity of disease and preventing HCMV infection can be categorized into two main approaches of vaccine design, with one focusing on virus modification and the other on individual antigens. However, no candidates in either class have been successful in achieving durable and protective immunity. Recent studies on the natural immune response provide new insight into HCMV vaccine strategy. In particular, studies have demonstrated that the incorporation of a pentameric complex is necessary for a vaccine to generate the potent neutralizing antibodies often seen in seropositive individuals. This review summarizes recent findings in the development of HCMV vaccines and key considerations that should be taken into vaccine design based on improved understanding of natural HCMV immunity.

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

BACKGROUND

In clinical trials of cytomegalovirus (CMV) glycoprotein B (gB) vaccines, CMV infection is detected by first depleting serum of anti-gB antibodies and then measuring anti-CMV antibodies with a commercially available enzyme-linked immunosorbent assay (ELISA) kit, with confirmation of positive findings by immunoblot.

OBJECTIVES

Identification of CMV immunoantigens for the development of an ELISA that detects specifically CMV infection in clinical samples from individuals immunized with gB vaccines.

STUDY DESIGN

Sensitivity and specificity of ELISAs using antigenic regions of CMV proteins UL83/pp65, UL99/pp28, UL44/pp52, UL80a/pp38, UL57, and UL32/pp150 were measured.

RESULTS

An IgG ELISA using a UL32/pp150 [862-1048] capture peptide was the most specific (93.7%) and sensitive (96.4%) for detecting CMV-specific antibodies in sera. The ELISA successfully detected CMV-specific antibodies in 22 of 22 sera of subjects who had been vaccinated with a gB vaccine but who had later been infected with CMV. The ELISA was linear over a wide range of CMV concentrations (57-16,814 ELISA units/mL) and was reproducible as indicated by a 5% intra-day and 7% inter-day coefficients of variation. The signal was specifically competed by UL32/pp150 [862-1048] peptide but not by CMV-gB or herpes simplex virus 2 glycoprotein D. Lipid and hemoglobin matrix did not interfere with the assay.

CONCLUSION

The UL32/pp150 [862-1048] IgG ELISA can be used for the sensitive and specific detection of CMV infection in gB-vaccinated individuals.

Infectious reactivation of cytomegalovirus explaining age- and sex-specific patterns of seroprevalence

Human cytomegalovirus (CMV) is a herpes virus with poorly understood transmission dynamics. Person-to-person transmission is thought to occur primarily through transfer of saliva or urine, but no quantitative estimates are available for the contribution of different infection routes. Using data from a large population-based serological study (n = 5,179), we provide quantitative estimates of key epidemiological parameters, including the transmissibility of primary infection, reactivation, and re-infection. Mixture models are fitted to age- and sex-specific antibody response data from the Netherlands, showing that the data can be described by a model with three distributions of antibody measurements, i.e. uninfected, infected, and infected with increased antibody concentration. Estimates of seroprevalence increase gradually with age, such that at 80 years 73% (95%CrI: 64%-78%) of females and 62% (95%CrI: 55%-68%) of males are infected, while 57% (95%CrI: 47%-67%) of females and 37% (95%CrI: 28%-46%) of males have increased antibody concentration. Merging the statistical analyses with transmission models, we find that models with infectious reactivation (i.e. reactivation that can lead to the virus being transmitted to a novel host) fit the data significantly better than models without infectious reactivation. Estimated reactivation rates increase from low values in children to 2%-4% per year in women older than 50 years. The results advance a hypothesis in which transmission from adults after infectious reactivation is a key driver of transmission. We discuss the implications for control strategies aimed at reducing CMV infection in vulnerable groups.

Human cytomegalovirus (CMV) is a herpes virus causing lifelong infection. In high-income countries, the probability of infection increases gradually with age such that at old age up to 100% of the population is infected. CMV is thought to be transmitted mainly by transfer of saliva or urine, but little quantitative evidence is available about the transmission dynamics. We analyze serological data to estimate age- and sex-specific rates of infection, re-infection, and reactivation. The analyses show that infectious reactivation (i.e. reactivation of the virus in an infected person that is sufficient for it to be transmitted to another person) is essential to explain the data. We propose that infectious reactivation in adults is an important driver of transmission of CMV.

Congenital Cytomegalovirus infection: advances and challenges in diagnosis, prevention and treatment

Cytomegalovirus (CMV) is the most frequent cause of congenital infection worldwide, with an estimated incidence in developing countries of 0.6-0.7% of all live births. The burden of disease related to congenital CMV in substantial, as it is the leading non-genetic cause of sensorineural hearing loss and an important cause of neurodevelopmental disabilities in children. Despite its clinical significance, congenital CMV infection often goes undetected because the majority of infected infants are asymptomatic at birth and screening programs have not been substantially implemented. Other than behavioral measures, effective interventions aimed at the prevention of maternal infection and of mother-to-child transmission are lacking. Due to a convergence of recent advances in both diagnostic and therapeutic strategies in infants with congenital CMV, though, the field likely will be changing rapidly over just the next few years. Specifically, a highly-sensitive screening test with high throughput potential has been developed, and treatment of infants symptomatically infected with congenital CMV has proven to be well-tolerated and effective in improving long-term hearing and neurodevelopmental outcomes.This review highlights the clinical importance of congenital CMV infection, the developments in laboratory diagnostics, and the benefits of antiviral therapy. It also identifies the global efforts still required in the prevention of maternal infection and in the optimization of antiviral therapy to further reduce the burden of congenital CMV disease.

Cytomegalovirus, Epstein-Barr virus and varicella zoster virus infection in the first two years of life: a cohort study in Bradford, UK

Background

Cytomegalovirus (CMV), Epstein Barr virus (EBV) and varicella-zoster virus (VZV) are common herpesviruses frequently acquired in childhood, which establish persistent, latent infection and are likely to impact the developing immune system. Little is known about the epidemiology of CMV and EBV infections in contemporary UK paediatric populations, particularly whether age at infection differs by ethnic group.

Methods

Children enrolled in the Born in Bradford Allergy and Infection Study had a blood sample taken and a questionnaire completed at 12 and 24 months of age. Ordered logistic regression quantified associations between ethnicity and other risk factors and age at CMV/EBV/VZV infection (<12 months, 12–24 months, uninfected at 24 months).

Results

Pakistani children (n = 472) were more likely to be infected with CMV and EBV at a younger age than White British children (n = 391) (CMV: adjusted odds ratio (OR) 2.53, 95% confidence interval (CI) 1.47–4.33; EBV: adjusted OR 2.16, 95% CI 1.43–3.26). Conversely, Pakistani children had lower odds of being VZV infected in the second year than White British children (adjusted OR 0.57, 95% CI 0.33–0.97). There was a strong association between increasing birth order and later CMV infection in Pakistani children.

Conclusions

We report large differences in CMV and EBV incidence in the first 2 years between Pakistani and White British children born in Bradford, which cannot be explained by differences in risk factors for infection. Our data will inform the optimum schedule for future CMV and EBV vaccination programmes.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-017-2319-7) contains supplementary material, which is available to authorized users.

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.

Cytomegalovirus Vaccines: Current Status and Future Prospects

Congenital human cytomegalovirus (HCMV) infection can result in severe and permanent neurological injury in newborns, and vaccine development is accordingly a major public health priority. HCMV can also cause disease in solid organ transplant (SOT) and hematopoietic stem-cell transplant (HSCT) recipients, and a vaccine would be valuable in prevention of viremia and end-organ disease in these populations. Currently there is no licensed HCMV vaccine, but progress toward this goal has been made in recent clinical trials. A recombinant HCMV glycoprotein B (gB) vaccine has been shown to have some efficacy in prevention of infection in young women and adolescents, and has provided benefit to HCMV-seronegative SOT recipients. Similarly, DNA vaccines based on gB and the immunodominant T-cell target, pp65 (ppUL83), have been shown to reduce viremia in HSCT patients. This review provides an overview of HCMV vaccine candidates in various stages of development, as well as an update on the current status of ongoing clinical trials. Protective correlates of vaccine-induced immunity may be different for pregnant woman and transplant patients. As more knowledge emerges about correlates of protection, the ultimate licensure of HCMV vaccines may reflect the uniqueness of the target populations being immunized.

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.

Brief Report: Enhanced Allogeneic Cellular Responses to Mismatched HLA-B Antigens Results in More Efficient Killing of HIV Infected Cells

Epidemiologic studies have demonstrated that HIV-1 discordant couples who share HLA-B alleles were more likely to transmit HIV-1. These data lead us to hypothesize that individuals who match at both HLA-B alleles should have a reduced allogeneic response than those who are not matched. We observed diminished killing of CD4 target cells only when HLA-B alleles were matched. We propose that for cell-associated HIV-1 transmission, the ability of the recipient to eliminate infected cells from a donor partner may be enhanced when HLA-B alleles are different between partners. These findings suggest a novel mechanism for protection against HIV infection.

Xenotransplantation and porcine cytomegalovirus

Porcine microorganisms may be transmitted to the human recipient when xenotransplantation with pig cells, tissues, and organs will be performed. Most of such microorganisms can be eliminated from the donor pig by specified or designated pathogen-free production of the animals. As human cytomegalovirus causes severe transplant rejection in allotransplantation, considerable concern is warranted on the potential pathogenicity of porcine cytomegalovirus (PCMV) in the setting of xenotransplantation. On the other hand, despite having a similar name, PCMV is different from HCMV. The impact of PCMV infection on pigs is known; however, the influence of PCMV on the human transplant recipient is unclear. However, first transplantations of pig organs infected with PCMV into non-human primates were associated with a significant reduction of the survival time of the transplants. Sensitive detection methods and strategies for elimination of PCMV from donor herds are required.