Cytomegalovirus strain diversity in seropositive women

Protective effect of pre-existing natural immunity in a nonhuman primate reinfection model of congenital cytomegalovirus infection

Congenital cytomegalovirus (cCMV) is the leading infectious cause of neurologic defects in newborns with particularly severe sequelae in the setting of primary CMV infection in the first trimester of pregnancy. The majority of cCMV cases worldwide occur after non-primary infection in CMV-seropositive women; yet the extent to which pre-existing natural CMV-specific immunity protects against CMV reinfection or reactivation during pregnancy remains ill-defined. We previously reported on a novel nonhuman primate model of cCMV in rhesus macaques where 100% placental transmission and 83% fetal loss were seen in CD4+ T lymphocyte-depleted rhesus CMV (RhCMV)-seronegative dams after primary RhCMV infection. To investigate the protective effect of preconception maternal immunity, we performed reinfection studies in CD4+ T lymphocyte-depleted RhCMV-seropositive dams inoculated in late first / early second trimester gestation with RhCMV strains 180.92 (n = 2), or RhCMV UCD52 and FL-RhCMVΔRh13.1/SIVgag, a wild-type-like RhCMV clone with SIVgag inserted as an immunological marker, administered separately (n = 3). An early transient increase in circulating monocytes followed by boosting of the pre-existing RhCMV-specific CD8+ T lymphocyte and antibody response was observed in the reinfected dams but not in control CD4+ T lymphocyte-depleted dams. Emergence of SIV Gag-specific CD8+ T lymphocyte responses in macaques inoculated with the FL-RhCMVΔRh13.1/SIVgag virus confirmed reinfection. Placental transmission was detected in only one of five reinfected dams and there were no adverse fetal sequelae. Viral whole genome, short-read, deep sequencing analysis confirmed transmission of both reinfection RhCMV strains across the placenta with ~30% corresponding to FL-RhCMVΔRh13.1/SIVgag and ~70% to RhCMV UCD52, consistent with the mixed human CMV infections reported in infants with cCMV. Our data showing reduced placental transmission and absence of fetal loss after non-primary as opposed to primary infection in CD4+ T lymphocyte-depleted dams indicates that preconception maternal CMV-specific CD8+ T lymphocyte and/or humoral immunity can protect against cCMV infection.

Seroepidemiological Survey of Cytomegalovirus Infection among Pregnant Women in Sudan

Human Cytomegalovirus (HCMV) is a leading healthcare problem associated with stillbirth and congenital abnormalities. Determining the seroprevalence and the possible risk factors related to HCMV infections may be a cornerstone in preventing its complications. This cross-sectional study was conducted in Kassala and River Nile States to determine the seroprevalence and risk factors associated with HCMV infection in pregnant women. One hundred eighty-four (n = 184) blood specimens were collected from pregnant women from February 2018 to January 2020. Enzyme-linked immunosorbent assay (ELISA) was used to detect HCMV-specific IgG and IgM antibodies. Socio-demographical characteristics of the women were collected using structured questionnaires. The results showed that HCMV IgG was detected in 170 (92.4%) of the blood specimens, and IgM was detected in 29/93 (31.2%). There was a significant relationship between the history of miscarriage and the presence of IgG and IgM with a p-value = 0.001 and between HCMV IgM and gestational stage (p-value = 0.028). The study found a strikingly high seroprevalence of HCMV infections among pregnant women in the investigated States. This high percentage of illiterate housewives living in rural areas makes it possible to reduce the incidence of HCMV infection in pregnant women by improving their knowledge, attitude, and practice regarding the route of viral transmission, which may reflect in lowering the rate of congenital diseases in their infants.

Protective effect of pre-existing natural immunity in a nonhuman primate reinfection model of congenital cytomegalovirus infection

Congenital cytomegalovirus (cCMV) is the leading infectious cause of neurologic defects in newborns with particularly severe sequelae in the setting of primary CMV infection in the first trimester of pregnancy. The majority of cCMV cases worldwide occur after non-primary infection in CMV-seropositive women; yet the extent to which pre-existing natural CMV-specific immunity protects against CMV reinfection or reactivation during pregnancy remains ill-defined. We previously reported on a novel nonhuman primate model of cCMV in rhesus macaques where 100% placental transmission and 83% fetal loss were seen in CD4 + T lymphocyte-depleted rhesus CMV (RhCMV)-seronegative dams after primary RhCMV infection. To investigate the protective effect of preconception maternal immunity, we performed reinfection studies in CD4+ T lymphocyte-depleted RhCMV-seropositive dams inoculated in late first / early second trimester gestation with RhCMV strains 180.92 ( n =2), or RhCMV UCD52 and FL-RhCMVΔRh13.1/SIV gag , a wild-type-like RhCMV clone with SIV gag inserted as an immunological marker ( n =3). An early transient increase in circulating monocytes followed by boosting of the pre-existing RhCMV-specific CD8+ T lymphocyte and antibody response was observed in the reinfected dams but not in control CD4+ T lymphocyte-depleted dams. Emergence of SIV Gag-specific CD8+ T lymphocyte responses in macaques inoculated with the FL-RhCMVΔRh13.1/SIV gag virus confirmed reinfection. Placental transmission was detected in only one of five reinfected dams and there were no adverse fetal sequelae. Viral whole genome, short-read, deep sequencing analysis confirmed transmission of both reinfection RhCMV strains across the placenta with ∼30% corresponding to FL-RhCMVΔRh13.1/SIV gag and ∼70% to RhCMV UCD52, consistent with the mixed human CMV infections reported in infants with cCMV. Our data showing reduced placental transmission and absence of fetal loss after non-primary as opposed to primary infection in CD4+ T lymphocyte-depleted dams indicates that preconception maternal CMV-specific CD8+ T lymphocyte and/or humoral immunity can protect against cCMV infection.

Author Summary

Globally, pregnancies in CMV-seropositive women account for the majority of cases of congenital CMV infection but the immune responses needed for protection against placental transmission in mothers with non-primary infection remains unknown. Recently, we developed a nonhuman primate model of primary rhesus CMV (RhCMV) infection in which placental transmission and fetal loss occurred in RhCMV-seronegative CD4+ T lymphocyte-depleted macaques. By conducting similar studies in RhCMV-seropositive dams, we demonstrated the protective effect of pre-existing natural CMV-specific CD8+ T lymphocytes and humoral immunity against congenital CMV after reinfection. A 5-fold reduction in congenital transmission and complete protection against fetal loss was observed in dams with pre-existing immunity compared to primary CMV in this model. Our study is the first formal demonstration in a relevant model of human congenital CMV that natural pre-existing CMV-specific maternal immunity can limit congenital CMV transmission and its sequelae. The nonhuman primate model of non-primary congenital CMV will be especially relevant to studying immune requirements of a maternal vaccine for women in high CMV seroprevalence areas at risk of repeated CMV reinfections during pregnancy.

Cytomegalovirus infection in malignant pleural mesothelioma

Human cytomegalovirus (HCMV) is a highly prevalent herpes virus which persists as a latent infection and has been detected in several different tumor types. HCMV disease is rare but may occur in high-risk settings, often manifesting as a pulmonary infection. To date HCMV has not been investigated in malignant pleural mesothelioma (MPM). In a consecutive case series of 144 MPM patients we evaluated two biomarkers of HCMV: IgG serostatus (defined as positive and negative) and DNAemia (>100 copies/mL of cell free HCMV DNA in serum). Approximately half of the MPM patient population was HCMV IgG seropositive (51%). HCMV DNAemia was highly prevalent (79%) in MPM and independent of IgG serostatus. DNAemia levels consistent with high level current infection (>1000 copies/mL serum) were present in 41% of patients. Neither IgG serostatus nor DNAemia were associated with patient survival. In tissues, we observed that HCMV DNA was present in 48% of tumors (n = 40) and only 29% of normal pleural tissue obtained from individuals without malignancy (n = 21). Our results suggest nearly half of MPM patients have a high level current HCMV infection at the time of treatment and that pleural tissue may be a reservoir for latent HCMV infection. These findings warrant further investigation to determine the full spectrum of pulmonary infections in MPM patients, and whether treatment for high level current HCMV infection may improve patient outcomes.

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.

Donor Cytomegalovirus Transmission Patterns in Solid Organ Transplant Recipients With Primary Infection

BACKGROUND

The epidemiology of single versus multiple cytomegalovirus (CMV) strain transmission from donor (D+) to seronegative solid organ transplant (SOT) recipients (R-) is uncertain, as is whether "relapsing" recipient infection represents changing strain predominance when multiple strains are transmitted. Here we characterized CMV strain transmission patterns in D+/R- SOT recipients.

METHODS

We studied pairs or groups of D+/R- SOT recipients who received organs from a common donor (group A) and recipients who experienced ≥2 waves of CMV DNAemia (group B). CMV in plasma was characterized by genotype-specific real-time PCR for genes gB and gH.

RESULTS

Single concordant genotypes were identified in 12 of 18 recipient pairs/group sharing a common donor (group A); at least 6 of 18 (33%) donors transmitted > 1 strain. A single CMV strain was detected in 14 of 15 recipients in group B; only 1 recipient had coinfection. A shift in CMV strain predominance occurred after the first posttransplant year in at least 4 recipients with coinfection.

CONCLUSIONS

Using a common donor approach, we confirmed that multiple CMV strain transmission from donors to R- SOT recipients is not uncommon. D+/R- SOT recipients with CMV coinfection can undergo changes in strain predominance in late waves of CMV DNAemia.

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

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

Cytomegalovirus Genetic Diversity Following Primary Infection

BACKGROUND

Infection with multiple cytomegalovirus (CMV) strains (mixed infection) was reported in a variety of hosts. As the virus genetic diversity in primary CMV infection and the changes over time remain incompletely defined, we examined CMV diversity and changes in diversity over time in healthy adolescent females who participated in a phase 2 CMV gB/MF59 vaccine trial.

METHODS

CMV genetic diversity was determined by genotyping of 5 genes-gB (UL55), gH (UL75), gN (UL73), US28, and UL144-in urine, saliva, and plasma samples from 15 study subjects.

RESULTS

At the time of primary infection, 5 of 12 (42%) urine samples had multiple virus strains, and 50% of vaccine recipients were infected with gB1 genotype (vaccine strain). Mixed infection was documented in all 15 subjects within 3 months after primary infection, and the majority had different CMV genotypes in different compartments. Changes in genotypes over time were observed in all subjects.

CONCLUSIONS

Infection with multiple CMV genotypes was common during primary infection and further diversification occurred over time. Infection with gB1 genotype in vaccine recipients suggests a lack of strain-specific protection from the vaccine. As only 5 polymorphic genes were assessed, this study likely underestimated the true genetic diversity in primary CMV infection.

Viral shedding, and distribution of cytomegalovirus glycoprotein H (UL75), glycoprotein B (UL55), and glycoprotein N (UL73) genotypes in congenital cytomegalovirus infection

BACKGROUND

Children with congenital CMV infection (cCMV) shed virus in urine and saliva for prolonged periods of time. Outcome of cCMV varies from asymptomatic infection with no sequelae in most cases, to severe longterm morbidity. The factors associated with asymptomatic cCMV are not well defined. We evaluated the viral shedding in a cohort of infants with cCMV identified on newborn screening. In addition, we describe the distribution of viral genotypes in our cohort of asymptomatic infants and previous cohorts of cCMV children in the literature.

METHODS

Study population consisted of 40 children with cCMV identified in screening of 19,868 infants, a prevalence of 2/1000. The viral shedding was evaluated at 3 and 18 months of age by real-time CMV-PCR of saliva and plasma, and CMV culture of urine. CMV positive saliva samples were analyzed for genotypes for CMV envelope glycoproteins gB (UL55), and gH (UL75) by genotype specific real-time PCR, and gN (UL73) by cloning and sequencing RESULTS: At 3 months age 40/40 saliva and urine samples, and 19/40 plasma samples were positive for CMV. At 18 months age all urine samples tested (33/33), 9/37 of saliva samples, and 2/34 plasma samples were positive for CMV. The genotype distribution did not differ from the published data CONCLUSIONS: The urinary virus shedding is more persistent than salivary shedding in children with cCMV. The genotype distribution was similar to previous literature and does not explain the low disease burden of cCMV in our population.

Prevalence of cytomegalovirus DNAemia and genotypic distribution among childbearing mothers and neonates in Taiwan

BACKGROUND

Congenital cytomegalovirus (CMV) infection is the leading cause of neurologic disabilities and sensorineural hearing loss in children. However, in Taiwan, there is limited information on the genotypic diversity and prevalence of perinatal CMV infection in both mothers and neonates. The aim of this study was to screen samples from both mothers and umbilical cord blood for CMV at the time of delivery and to determine the CMV genotypic distribution.

METHODS

Between June 2012 and July 2015, residual maternal and umbilical cord blood samples were collected from consenting participants admitted to the Chang Bing Show Chwan Memorial Hospital in central Taiwan. The blood samples were screened for CMV DNA using real-time PCR assay, and the genotypic classification of the CMV UL55, UL144, and US28 genes was determined by sequencing and phylogenetic analysis.

RESULTS

A total of 1282 mother-neonate paired samples were enrolled in the study, 95.3% of whom were Taiwanese. CMV DNA was detectable in 6.2% of the maternal blood samples, with a significantly higher rate noted in non-Taiwanese mothers (11.7%,p=0.027). For the 1,282 umbilical cord blood samples, CMV DNA was detectable in 5.3% of the samples. The presence of CMV DNA in maternal blood was positively associated with the presence of CMV DNA in umbilical cord blood (p=0.01). In addition, the UL55, UL144, and US28 genotypic distribution was similar between mothers and neonates.

CONCLUSION

The prevalence of CMV DNAemia in childbearing mothers and neonates is similar and their genotypic distribution implies potential CMV infection during pregnancy.

Observational study of cytomegalovirus from breast milk and necrotising enterocolitis

OBJECTIVE

To evaluate the relationship between cytomegalovirus (CMV) exposure from breast milk and risk of necrotising enterocolitis (NEC).

DESIGN

Secondary analysis of a multicentre, observational cohort study. Maternal breast milk and infant serum or urine were serially evaluated by nucleic acid testing at scheduled intervals for CMV. Infants with evidence of congenital infection were excluded. Competing-risks Cox models, with adjustment for confounders, were used to evaluate the relationship between breast milk CMV exposure or postnatal CMV infection and NEC.

SETTING

Three neonatal intensive care units in Atlanta, Georgia.

PATIENTS

Infants with a birth weight≤1500 grams.

EXPOSURES

Maximal CMV viral load in breast milk in the first 14 days after birth or postnatal CMV infection. Two different approaches were used to assess the timing of onset of CMV infection (midpoint or early).

MAIN OUTCOME MEASURES

NEC, defined as Bell stage II or greater.

RESULTS

Among 596 enrolled infants, 457 (77%) were born to CMV seropositive mothers and 33 developed postnatal CMV infection (cumulative incidence 7.3%, 95% CI 5.0% to 10.1%). The incidence of NEC was 18% (6/33) among infants with CMV infection, compared with 7% (37/563) among infants without infection (adjusted cause-specific HR (CSHR): 2.81; 95% CI 0.73 to 10.9 (midpoint); 6.02; 95% CI 1.28 to 28.4 (early)). Exposure to higher breast milk CMV viral load was associated with a higher risk of NEC (adjusted CSHR per twofold increase 1.28; 95% CI 1.06 to 1.54).

CONCLUSIONS

CMV exposure from breast milk may be associated with the development of NEC in very low birth weight infants.

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.

Prevalence, Magnitude, and Genotype Distribution of Urinary Cytomegalovirus (CMV) Shedding Among CMV-Seropositive Children and Adolescents in the United States

Background

There are limited nationally representative data on correlates of cytomegalovirus (CMV) shedding among children and adolescents. In addition, the genotype distribution of CMV infections has not been well characterized among general populations in the United States.

Methods

This study characterized urinary CMV shedding among CMV immunoglobulin G-positive 6- to 19-year-olds in the US household population using data from the 1999-2004 National Health and Nutrition Examination Survey (NHANES). Multivariable Poisson regression was used to estimate adjusted prevalence ratios (aPR) and corresponding 95% confidence intervals (CIs). Analyses were weighted and multiple imputation was performed to handle missing data (with the exception of CMV genotypes).

Results

Prevalence of urinary CMV shedding was significantly lower among 9- to 11-year-olds (20.6%; aPR = 0.61; 95% CI, 0.44-0.83) and 12- to 19-year-olds (7.0%; aPR = 0.21; 95% CI, 0.14-0.30) compared with 6- to 8-year-olds (34.4%). Among CMV shedders, the youngest age group also had the highest urinary CMV viral loads. The prevalence of urinary CMV shedding among obese individuals was significantly lower compared with lean individuals (aPR = 0.68; 95% CI, 0.47-0.99). Among CMV shedders, glycoprotein B (gB)1 (51%) was the most prevalent gB variant, followed by gB2 (29%), gB3 (21%), and gB4 (13%); glycoprotein H (gH)2 (60%) was more prevalent than gH1 (48%). Multiple (≥2) gB (14%) and multiple gH (7%) infections were detected among CMV shedders.

Conclusions

This study underscores the importance of young children even above the age of 5 years as a potential source of CMV transmission. The detection of multiple CMV strains among CMV shedders may have implications for the transmission of viral diversity as well as vaccine development.

Genotyping of Cytomegalovirus from Symptomatic Infected Neonates in Iraq

Among all other viruses, human cytomegalovirus (HCMV) is the most frequent cause of congenital infection worldwide. Strain variation in HCMV may predict severity or outcome of congenital HCMV disease. Previous studies have associated a particular genotype with specific sequelae or more severe illness, but the results were contradictory. There are no previous studies addressing the genotype of HCMV in Iraq. Therefore, the present study is aimed at molecular detection and genotyping of HCMV isolated from symptomatic congenitally/perinatally infected neonates. This prospective study comprised 24 serum samples from symptomatic neonates with congenital/perinatal infection. Viral DNA was extracted from these serum samples; nested polymerase chain reaction was used to amplify the HCMV gB (UL55) gene. Polymerase chain reaction products of the second round of amplification were subjected to direct Sanger sequencing. Bioedit and MEGA5 software (EMBL-EBI, Hinxton, Cambridgeshire, UK) were used for alignment and construction of a phylogenetic tree. Human cytomegalovirus DNA was detected in 23 of 24 samples (95.8%). According to the phylogenetic analysis, three genotypes of the virus were identified; gB1, gB2, and gB3 genotypes. However, the gB4 genotype was not detected. Human cytomegalovirus gB3 was the most frequent genotype: 14 of 24 (58.33%) among symptomatic infected infants, followed by gB1 (6/24; 25%) and gB2 (4/24; 16.67%). A mixed HCMV infection with gB3/gB1 was detected in only one case. Human cytomegalovirus gB3 was the most predominant genotype among symptomatic congenitally/perinatally HCMV-infected neonates. No association was found between B3 genotype and specific clinical presentation. Jaundice was the most common clinical feature among symptomatically infected neonates, followed by hepatosplenomegaly.

Intrahost Dynamics of Human Cytomegalovirus Variants Acquired by Seronegative Glycoprotein B Vaccinees

Human cytomegalovirus (HCMV) is the most common congenital infection worldwide and a frequent cause of hearing loss and debilitating neurologic disease in newborn infants. Thus, a vaccine to prevent HCMV-associated congenital disease is a public health priority. One potential strategy is vaccination of women of child bearing age to prevent maternal HCMV acquisition during pregnancy. The glycoprotein B (gB) plus MF59 adjuvant subunit vaccine is the most efficacious tested clinically to date, demonstrating 50% protection against primary HCMV infection in a phase 2 clinical trial. Yet, the impact of gB/MF59-elicited immune responses on the population of viruses acquired by trial participants has not been assessed. In this analysis, we employed quantitative PCR as well as multiple sequencing methodologies to interrogate the magnitude and genetic composition of HCMV populations infecting gB/MF59 vaccinees and placebo recipients. We identified several differences between the viral dynamics in acutely infected vaccinees and placebo recipients. First, viral load was reduced in the saliva of gB vaccinees, though not in whole blood, vaginal fluid, or urine. Additionally, we observed possible anatomic compartmentalization of gB variants in the majority of vaccinees compared to only a single placebo recipient. Finally, we observed reduced acquisition of genetically related gB1, gB2, and gB4 genotype "supergroup" HCMV variants among vaccine recipients, suggesting that the gB1 genotype vaccine construct may have elicited partial protection against HCMV viruses with antigenically similar gB sequences. These findings suggest that gB immunization had a measurable impact on viral intrahost population dynamics and support future analysis of a larger cohort.IMPORTANCE Though not a household name like Zika virus, human cytomegalovirus (HCMV) causes permanent neurologic disability in one newborn child every hour in the United States, which is more than that for Down syndrome, fetal alcohol syndrome, and neural tube defects combined. There are currently no established effective measures to prevent viral transmission to the infant following HCMV infection of a pregnant mother. However, the glycoprotein B (gB)/MF59 vaccine, which aims to prevent pregnant women from acquiring HCMV, is the most successful HCMV vaccine tested clinically to date. Here, we used viral DNA isolated from patients enrolled in a gB vaccine trial who acquired HCMV and identified several impacts that this vaccine had on the size, distribution, and composition of the in vivo viral population. These results have increased our understanding of why the gB/MF59 vaccine was partially efficacious, and such investigations will inform future rational design of a vaccine to prevent congenital HCMV.

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.

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.

Cytomegaloviruses in a Community of Wild Nonhuman Primates in Taï National Park, Côte D'Ivoire

Cytomegaloviruses (CMVs) are known to infect many mammals, including a number of nonhuman primates (NHPs). However, most data available arose from studies led on captive individuals and little is known about CMV diversity in wild NHPs. Here, we analyzed a community of wild nonhuman primates (seven species) in Taï National Park (TNP), Côte d’Ivoire, with two PCR systems targeting betaherpesviruses. CMV DNA was detected in 17/87 primates (4/7 species). Six novel CMVs were identified in sooty mangabeys, Campbell’s monkeys and Diana monkeys, respectively. In 3/17 positive individuals (from three NHP species), different CMVs were co-detected. A major part of the glycoprotein B coding sequences of the novel viruses was amplified and sequenced, and phylogenetic analyses were performed that included three previously discovered CMVs of western red colobus from TNP and published CMVs from other NHP species and geographic locations. We find that, despite this locally intensified sampling, NHP CMVs from TNP are completely host-specific, pinpointing the absence or rarity of cross-species transmission. We also show that on longer timescales the evolution of CMVs is characterized by frequent co-divergence with their hosts, although other processes, including lineage duplication and host switching, also have to be invoked to fully explain their evolutionary relationships.

The impact of pathogen burden on leukocyte telomere length in the Multi-Ethnic Study of Atherosclerosis

Several infections have been linked to telomere shortening and in some cases these associations have varied by sex. We assessed the association between seropositivity to four persistent pathogens (cytomegalovirus (CMV), herpes simplex virus-1, Helicobacter pylori, Chlamydia pneumoniae), and total pathogen burden on leukocyte telomere length in a diverse US sample. Data came from the Multi-Ethnic Study of Atherosclerosis, a population-based cohort study. We utilized cross-sectional survey data, and biological samples from participants tested for pathogens and telomere length (N = 163). Linear regression was used to examine the association between seropositivity for individual pathogens as well as total pathogen burden and telomere length, adjusting for various confounders. CMV seropositivity and increased total pathogen burden level were significantly associated with shorter telomere length among females (β = -0·1204 (standard error (s.e.) 0·06), P = 0·044) and (β = -0·1057 (s.e. = 0·05), P = 0·033), respectively. There was no statistically significant association among males. Our findings suggest that prevention or treatment of persistent pathogens, in particular CMV, may play an important role in reducing telomere shortening over the life course among women. Future research is needed to confirm these novel findings in larger longitudinal samples.

Self-disseminating vaccines for emerging infectious diseases

Modern human activity fueled by economic development is profoundly altering our relationship with microorganisms. This altered interaction with microbes is believed to be the major driving force behind the increased rate of emerging infectious diseases from animals. The spate of recent infectious disease outbreaks, including Ebola virus disease and Middle East respiratory syndrome, emphasize the need for development of new innovative tools to manage these emerging diseases. Disseminating vaccines are one such novel approach to potentially interrupt animal to human (zoonotic) transmission of these pathogens.

Genetic identification of cytomegaloviruses in a rural population of Côte d'Ivoire

Background

Cytomegaloviruses (CMVs) are herpesviruses that infect many mammalian species, including humans. Infection generally passes undetected, but the virus can cause serious disease in individuals with impaired immune function. Human CMV (HCMV) is circulating with high seroprevalence (60–100 %) on all continents. However, little information is available on HCMV genoprevalence and genetic diversity in subsaharan Africa, especially in rural areas of West Africa that are at high risk of human-to-human HCMV transmission. In addition, there is a potential for zoonotic spillover of pathogens through bushmeat hunting and handling in these areas as shown for various retroviruses. Although HCMV and nonhuman CMVs are regarded as species-specific, potential human infection with CMVs of non-human primate (NHP) origin, shown to circulate in the local NHP population, has not been studied.

Findings

Analysis of 657 human oral swabs and fecal samples collected from 518 individuals living in 8 villages of Côte d’Ivoire with generic PCR for identification of human and NHP CMVs revealed shedding of HCMV in 2.5 % of the individuals. Determination of glycoprotein B sequences showed identity with strains Towne, AD169 and Toledo, respectively. NHP CMV sequences were not detected.

Conclusions

HCMV is actively circulating in a proportion of the rural Côte d’Ivoire human population with circulating strains being closely related to those previously identified in non-African countries. The lack of NHP CMVs in human populations in an environment conducive to cross-species infection supports zoonotic transmission of CMVs to humans being at most a rare event.

Detection of Cytomegalovirus Antibodies Using a Biosensor Based on Imaging Ellipsometry

Background

Cytomegalovirus (CMV) is the most common infectious cause of mental disability in newborns in developed countries. There is an urgent need to establish an early detection and high-throughput screening method for CMV infection using portable detection devices.

Methods

An antibody analysis method is reported for the detection and identification of CMV antibodies in serum using a biosensor based on high spatial resolution imaging ellipsometry (BIE). CMV antigen (CMV-3A) was immobilized on silicon wafers and used to capture CMV antibodies in serum. An antibody against human immunoglobulin G (anti-IgG) was used to confirm the IgG antibody against CMV captured by the CMV-3A.

Results

Our results show that this assay is rapid and specific for the identification of IgG antibody against CMV. Further, patient serum was quantitatively assessed using the standard curve method, and the quantitative results were in agreement with the enzyme-linked immunosorbent assay. The CMV antibody detection sensitivity of BIE reached 0.01 IU/mL.

Conclusions

This novel biosensor may be a valuable diagnostic tool for analysis of IgG antibody against CMV during CMV infection screening.

Strain Variation and Disease Severity in Congenital Cytomegalovirus Infection: In Search of a Viral Marker

The wide spectrum of congenital cytomegalovirus (CMV) disease and known differences in the biology and in vitro growth of CMV strains continue to drive studies in search for specific viral genetic determinants that may predict severity of congenital CMV disease. Several CMV genes have been studied in detail in congenitally infected children, but the complexity of the viral genome and differences in the definition of symptomatic disease versus asymptomatic CMV infection continue to raise questions related to what constitutes a pathogenic CMV strain.

Examining the species-specificity of rhesus macaque cytomegalovirus (RhCMV) in cynomolgus macaques

Cytomegalovirus (CMV) is a highly species-specific virus that has co-evolved with its host over millions of years and thus restricting cross-species infection. To examine the extent to which host restriction may prevent cross-species research between closely related non-human primates, we evaluated experimental infection of cynomolgus macaques with a recombinant rhesus macaque-derived CMV (RhCMV-eGFP). Twelve cynomolgus macaques were randomly allocated to three groups: one experimental group (RhCMV-eGFP) and two control groups (UV-inactivated RhCMV-eGFP or media alone). The animals were given two subcutaneous inoculations at week 0 and week 8, and a subset of animals received an intravenous inoculation at week 23. No overt clinical or haematological changes were observed and PBMCs isolated from RhCMV-eGFP inoculated animals had comparable eGFP- and IE-1-specific cellular responses to the control animals. Following inoculation with RhCMV-eGFP, we were unable to detect evidence of infection in any blood or tissue samples up to 4 years post-inoculation, using sensitive viral co-culture, qPCR, and Western blot assays. Co-culture of urine and saliva samples demonstrated the presence of endogenous cynomolgus CMV (CyCMV) cytopathic effect, however no concomitant eGFP expression was observed. The absence of detectable RhCMV-eGFP suggests that the CyCMV-seropositive cynomolgus macaques were not productively infected with RhCMV-eGFP under these inoculation conditions. In a continued effort to develop CMV as a viral vector for an HIV/SIV vaccine, these studies demonstrate that CMV is highly restricted to its host species and can be highly affected by laboratory cell culture. Consideration of the differences between lab-adapted and primary viruses with respect to species range and cell tropism should be a priority in evaluating CMV as vaccine vector for HIV or other pathogens at the preclinical development stage.

Inflammatory breast cancer: high incidence of detection of mixed human cytomegalovirus genotypes associated with disease pathogenesis

Inflammatory breast cancer (IBC) is a highly metastatic, aggressive, and fatal form of breast cancer. Patients presenting with IBC are characterized by a high number of axillary lymph node metastases. Recently, we found that IBC carcinoma tissues contain significantly higher levels of human cytomegalovirus (HCMV) DNA compared to other breast cancer tissues that may regulate cell signaling pathways. In fact, HCMV pathogenesis and clinical outcome can be statistically associated with multiple HCMV genotypes within IBC. Thus, in the present study, we established the incidence and types of HCMV genotypes present in carcinoma tissues of infected non-IBC versus IBC patients. We also assessed the correlation between detection of mixed genotypes of HCMV and disease progression. Genotyping of HCMV in carcinoma tissues revealed that glycoprotein B (gB)-1 and glycoprotein N (gN)-1 were the most prevalent HCMV genotypes in both non-IBC and IBC patients with no significant difference between patients groups. IBC carcinoma tissues, however, showed statistically significant higher incidence of detection of the gN-3b genotype compared to non-IBC patients. The incidence of detection of mixed genotypes of gB showed that gB-1 + gB-3 was statistically significantly higher in IBC than non-IBC patients. Similarly, the incidence of detection of mixed genotypes of gN showed that gN-1 + gN-3b and gN-3 + gN-4b/c were statistically significant higher in the carcinoma tissues of IBC than non-IBC. Mixed presence of different HCMV genotypes was found to be significantly correlated with the number of metastatic lymph nodes in non-IBC but not in IBC patients. In IBC, detection of mixed HCMV different genotypes significantly correlates with lymphovascular invasion and formation of dermal lymphatic emboli, which was not found in non-IBC patients.

Childhood environments and cytomegalovirus serostatus and reactivation in adults

Childhood adversity, defined in terms of material hardship or physical or emotional maltreatment has been associated with risk for infection with cytomegalovirus (CMV) among children and adolescents, and with CMV reactivation in children and adults. The present study examined whether different dimensions of childhood experience-those pertaining to socioeconomic status (SES), physical environment, or family relationships-relate differentially to CMV serostatus and reactivation during adulthood. Participants were 140 healthy adults, aged 18-55years (41% female; 64% white). Childhood environments were assessed retrospectively and included family SES (parental housing tenure); childhood neighborhood environment (urban residence; physical conditions; safety; and social atmosphere); residential exposures (parental smoking and physical condition of home); and family relationships (parental divorce; warmth; harmony; dysfunction; parental bonding). Approximately 39% (n=53) of participants were CMV+. In individual analyses controlling for age, sex, race, body mass, current adult SES and smoking status, fewer years of parental home ownership, having a parent who smoked, and living in a poorly maintained or unsafe neighborhood each were associated with greater odds of infection with CMV. By comparison, in individual analyses limited to CMV+ participants, less family warmth, less harmony, greater dysfunction, and suboptimal parental bonding each were related to higher antibody levels, independent of the aforementioned covariates. Findings were not attributable to current adult perceptions of psychological stress or relative levels of emotional stability. These results suggest that different types of childhood adversity may be associated with differential effects on CMV infection and latency.

Consistent associations between measures of psychological stress and CMV antibody levels in a large occupational sample

Cytomegalovirus (CMV) is a herpes virus that has been implicated in biological aging and impaired health. Evidence, largely accrued from small-scale studies involving select populations, suggests that stress may promote non-clinical reactivation of this virus. However, absent is evidence from larger studies, which allow better statistical adjustment for confounding and mediating factors, in more representative samples. The present study involved a large occupational cohort (N=887, mean age=44, 88% male). Questionnaires assessed psychological (i.e., depression, anxiety, vital exhaustion, SF-12 mental health), demographic, socioeconomic (SES), and lifestyle variables. Plasma samples were analyzed for both the presence and level of CMV-specific IgG antibodies (CMV-IgG), used as markers for infection status and viral reactivation, respectively. Also assessed were potential biological mediators of stress-induced reactivation, such as inflammation (C-reactive protein) and HPA function (awakening and diurnal cortisol). Predictors of CMV infection and CMV-IgG among the infected individuals were analyzed using logistic and linear regression analyses, respectively. Confirming prior reports, lower SES (education and job status) was positively associated with infection status. Among those infected (N=329), higher CMV-IgG were associated with increased anxiety (β=.14, p<.05), depression (β=.11, p=.06), vital exhaustion (β=.14, p<.05), and decreased SF-12 mental health (β=-.14, p<.05), adjusting for a range of potential confounders. Exploratory analyses showed that these associations were generally stronger in low SES individuals. We found no evidence that elevated inflammation or HPA-function mediated any of the associations. In the largest study to date, we established associations between CMV-IgG levels and multiple indicators of psychological stress. These results demonstrate the robustness of prior findings, and extend these to a general working population. We propose that stress-induced CMV replication warrants further research as a psychobiological mechanism linking stress, aging and health.

Cytomegalovirus glycoprotein H genotype distribution and the relationship with hearing loss in children

Cytomegalovirus (CMV) is a leading cause of congenital infection and a leading infectious cause of hearing loss in children. The ORF UL75 gene encodes envelope glycoprotein H (gH), which is essential for CMV entry into host cells and the target of the immune response in humans. However, the distribution of gH variants and the relationship between the viral genotype, viral load, and sequelae in children infected with CMV is debated. The UL75 genetic variation of CMV isolates from 42 newborns infected congenitally with CMV and 93 infants with postnatal or unproven congenital CMV infection was analyzed. Genotyping was performed by analysis of PCR-amplified fragments, and the viral load was measured by quantitative real-time PCR. There were no differences in the distribution of gH genotypes in the children infected congenitally and postnatally. Mixed-genotype infections with both gH1 and gH2 variants were detected in approximately 25% of the examined patients. No relationship between UL75 gene polymorphisms and the symptoms at birth was observed. The results suggest that the infection with gH2 genotype diminishes the risk of hearing loss in children (P = 0.010). In addition, sensorineural hearing loss was associated with CMV gH1 genotype infection in infants (P = 0.032) and a high viral load in urine (P = 0.005). In conclusion, it was found that the gH genotype does not predict clinical sequelae in newborn infants following congenital CMV infection. However, these results suggest that the gH genotype might be associated with hearing loss in children.

Induction of innate immune signatures following polyepitope protein-glycoprotein B-TLR4&9 agonist immunization generates multifunctional CMV-specific cellular and humoral immunity

Recent studies have suggested that a successful subunit human cytomegalovirus (CMV) vaccine requires improved formulation to generate broad-based anti-viral immunity following immunization. Here we report the development of a non-live protein-based vaccine strategy for CMV based on a polyepitope protein and CMV glycoprotein B (gB) adjuvanted with TLR4 and/or TLR9 agonists. The polyepitope protein includes contiguous multiple MHC class I-restricted epitopes with an aim to induce CD8⁺ T cell immunity, while gB is an important target for CD4⁺ T cell immunity and neutralizing antibodies. Optimal immunogenicity of this bivalent non-live protein vaccine formulation was dependent upon the co-administration of both the TLR4 and TLR9 agonist, which was associated with the activation of innate immune signatures and the influx of different DC subsets including plasmacytoid DCs and migratory CD8-DEC205+CD103-CD326- langerin-negative dermal DCs into the draining lymph nodes. Furthermore these professional antigen presenting cells also expressed IL-6, IL-12p70, TNFα, and IFNα which play a crucial role in the activation of adaptive immunity. In summary, this study provides a novel platform technology in which broad-based anti-CMV immune responses upon vaccination can be maximized by co-delivery of viral antigens and TLR4 and 9 agonists which induce activation of innate immune signatures and promote potent antigen acquisition and cross-presentation by multiple DC subsets.

Recent approaches and strategies in the generation of antihuman cytomegalovirus vaccines

The development of prophylactic and to lesser extent therapeutic vaccines for the prevention of disease associated with human cytomegalovirus (HCMV) infections has received considerable attention from biomedical researchers and pharmaceutical companies over the previous 15 years, even though attempts to produce such vaccines have been described in the literature for over 40 years. Studies of the natural history of congenital HCMV infection and infection in allograft recipients have suggested that prophylaxis of disease associated with HCMV infection could be possible, particularly in hosts at risk for more severe disease secondary to the lack of preexisting immunity. Provided a substantial understanding of immune response to HCMV together with several animal models that faithfully recapitulate aspects of human infection and immunity, investigators seem well positioned to design and test candidate vaccines. Yet more recent studies of the role of a maternal immunity in the natural history of congenital HCMV infection, including the recognition that reinfection of previously immune women by genetically distinct strains of HCMV occur in populations with a high seroprevalence, have raised several questions about the nature of protective immunity in maternal populations. This finding coupled with observations that have documented a significant incidence of damaging congenital infections in offspring of women with immunity to HCMV prior to conception has suggested that vaccine development based on conventional paradigms of adaptive immunity to viral infections may be of limited value in the prevention of damaging congenital HCMV infections. Perhaps a more achievable goal will be prophylactic vaccines to modify HCMV associated disease in allograft transplant recipients. Although recent descriptions of the results from vaccine trials have been heralded as evidence of an emerging success in the quest for a HCMV vaccine, careful analyses of these studies have also revealed that major hurdles remain to be addressed by current strategies.

Copy numbers of telomeric repeat sequences of human herpesvirus 6B in clinical isolates: possibility of mixed infections

In order to determine whether mixed infections of human herpesvirus 6B (HHV-6B) occur in immunocompetent and immunocompromised individuals, we examined the copy numbers of telomeric repeat sequences (TRS) of clinical isolates. In clinical isolates obtained from patients with exanthem subitum caused by primary HHV-6B infection, PCR products with HHV-6B TRS ranging between 400 and 800 bp were amplified. PCR products of various sizes were amplified in four clinical isolates from drug-induced hypersensitivity syndrome (DIHS) patients and 15 isolates from hematopoietic stem cell transplant (HSCT) recipients with HHV-6B reactivation. Based on the sequence analysis of the PCR products, the copy numbers of TRS in DIHS and HSCT patients were between 42 and 82 and 22 and >90, respectively. For two of the HSCT recipients, HHV-6B TRS PCR products of different sizes were detected in several isolates from each patient, which suggests mixed HHV-6B infections. In two of the posttransplant HHV-6B encephalitis patients, the sizes of the TRS nested PCR products amplified from the reactivated virus detected in the central nervous system differed from those of the virus detected in initial isolates from peripheral blood mononuclear cells. Taken together, these results suggest that PCR analysis of TRS copy number is a reliable tool for the discrimination of HHV-6B clinical isolates. Additionally, mixed HHV-6B infections occurred in HSCT recipients, and in some cases, compartmentalization of the HHV-6B strains to the central nervous system versus the blood compartment occurred in posttransplant HHV-6B encephalitis patients.

Genotypic diversity and mixed infection in newborn disease and hearing loss in congenital cytomegalovirus infection

BACKGROUND

Congenital cytomegalovirus (cCMV) is a common congenital infection and a leading nongenetic cause of sensorineural hearing loss (SNHL). CMV exhibits extensive genetic variability, and infection with multiple CMV strains (mixed infection) was shown to be common in congenital CMV. The role of mixed infections in disease and outcome remains to be defined.

METHODS

Genotyping of envelope glycoproteins, UL55 (gB), UL73 (gN) and UL75 (gH), was performed on saliva specimens of 79 infants from the ongoing CMV and Hearing Multicenter Screening (CHIMES) Study and on blood and urine specimens of 52 infants who participated in natural history studies at the University of Alabama at Birmingham. Genotyping of UL144 and US28 was also performed in the CHIMES cohort. The association of individual genotypes and mixed infection with clinical findings at birth and SNHL was examined.

RESULTS

Thirty-seven of 131 infants (28%) were symptomatic at birth and 26 (20%) had SNHL at birth. All known genotypes of UL55, UL75, UL73 and US28 were represented, and no particular genotype was associated with symptomatic infection or SNHL. UL144 subtype C was more common in symptomatic infants but not associated with SNHL. Mixed infection was observed in 59 infants (45%) and not associated with symptoms (P = 0.43) or SNHL at birth (P = 0.82). In the cohort of 52 infants with long-term hearing outcome, mixed infection at birth was not predictive of SNHL.

CONCLUSIONS

Mixed infection is common in infants with congenital CMV but is neither associated with symptomatic infection nor associated with SNHL.

Recent advances in designing an effective vaccine to prevent cytomegalovirus-associated clinical diseases

It is now well over a decade since the US Institute of Medicine of the National Academy of Sciences assigned the highest priority for a vaccine to prevent congenital human CMV infection, which was subsequently endorsed by the US National Vaccine Program Office. In spite of extensive efforts over many years, successful licensure of a CMV vaccine formulation remains elusive. While the understanding of immune regulation of CMV infection in healthy virus carriers and diseased patients has dramatically improved, traditional vaccine development programs have failed to exploit this knowledge. Until recently, most efforts have concentrated on designing vaccine formulations that block CMV infection through neutralizing antibodies. However, studies carried out in various disease settings, especially in transplant patients, have clearly emphasized the importance of cellular immunity and it is indeed encouraging to see that recent CMV vaccine development programs have started to incorporate this arm of the immune system. A number of new vaccine candidates have been found to be effective in preclinical studies, and are able to induce CMV-specific immune responses in clinical studies, although firm evidence for long-term efficacy is not yet available. For successful implementation of these vaccines in clinical settings, it will be important to demonstrate that the vaccine can induce effective levels of immunity for prevention of transmission of viral infection from mother to unborn baby and thus reduce CMV-related pathogenesis. For transplant recipients, vaccine strategies should be aimed at the induction of immunity that restricts viral reactivation and limits development of disease.

Natural killer cell dependent within-host competition arises during multiple MCMV infection: consequences for viral transmission and evolution

It is becoming increasingly clear that many diseases are the result of infection from multiple genetically distinct strains of a pathogen. Such multi-strain infections have the capacity to alter both disease and pathogen dynamics. Infection with multiple strains of human cytomegalovirus (HCMV) is common and has been linked to enhanced disease. Suggestions that disease enhancement in multi-strain infected patients is due to complementation have been supported by trans-complementation studies in mice during co-infection of wild type and gene knockout strains of murine CMV (MCMV). Complementation between naturally circulating strains of CMV has, however, not been assessed. In addition, many models of multi-strain infection predict that co-infecting strains will compete with each other and that this competition may contribute to selective transmission of more virulent pathogen strains. To assess the outcome of multi-strain infection, C57BL/6 mice were infected with up to four naturally circulating strains of MCMV. In this study, profound within-host competition was observed between co-infecting strains of MCMV. This competition was MCMV strain specific and resulted in the complete exclusion of certain strains of MCMV from the salivary glands of multi-strain infected mice. Competition was dependent on Ly49H⁺ natural killer (NK) cells as well as the expression of the ligand for Ly49H, the MCMV encoded product, m157. Strains of MCMV which expressed an m157 gene product capable of ligating Ly49H were outcompeted by strains of MCMV expressing variant m157 genes. Importantly, within-host competition prevented the shedding of the less virulent strains of MCMV, those recognized by Ly49H, into the saliva of multi-strain infected mice. These data demonstrate that NK cells have the strain specific recognition capacity required to meditate within-host competition between strains of MCMV. Furthermore, this within-host competition has the capacity to shape the dynamics of viral shedding and potentially select for the transmission of more virulent virus strains.

Infection of the host with multiple strains of a pathogen is common and occurs with the herpesvirus, human cytomegalovirus (HCMV). However the effects of multi-strain infection on the host and the pathogen remain poorly studied. Here we show, in a mouse model, that infection of C57BL/6 mice with multiple strains of murine CMV (MCMV) results in profound within-host competition. Competition between the strains of MCMV is dependent on Ly49H⁺ natural killer (NK) cells. The NK cell activation receptor Ly49H receptor targets certain genotypes of the viral protein, m157. During multi-strain infection, strains of MCMV encoding an m157 capable of binding Ly49H are excluded from the salivary gland and the saliva of C57BL/6 mice, allowing for the shedding of only non-Ly49H binding strains of MCMV in the saliva. This within-host competition could therefore have significant impacts on the circulation of MCMV strains, as only the most virulent MCMV strains were present in the saliva.

Clinical evaluation of new automated cytomegalovirus IgM and IgG assays for the Elecsys(®) analyser platform

Cytomegalovirus (CMV) is a leading cause of physical and neurological abnormalities in newborns. Hence, the diagnosis of CMV infection in pregnant women is necessary in order to allow appropriate management of their pregnancy. New assays have been developed for the Roche Elecsys® immunoassay platform that detect CMV-specific immunoglobulin (Ig)M and IgG, with the IgM assay designed to target IgM produced at the start of infection rather than IgM persisting later in infection. This study aimed to evaluate the performance of the new assays compared with other commercial kits widely distributed in laboratories. The performance of the Elecsys and comparator CMV IgM and IgG assays was assessed using 967 preselected patient samples characterised by CMV infection status, as well as being compared using 1,668 unselected clinical samples. The Elecsys CMV IgM and IgG assays performed consistently with comparator assays using the preselected samples. The Elecsys CMV IgM assay showed improved sensitivity compared with the Enzygnost® assay in primary infection (91.2 % vs. 79.4 %) and improved specificity over the Architect® assay in potentially cross-reacting samples (94.1 % vs. 82.4 %). The Elecsys IgM assay reported fewer positive results in the later stages of CMV infection compared with ETI-CYTOK-M ELISA, while the Elecsys IgG assay reported slightly fewer negative results in the early stages of infection compared with ETI-CYTOK-G ELISA. There was good agreement between Elecsys and comparator assays using unselected clinical samples (range 90.4-99.4 %). The Elecsys CMV IgM and IgG assays compare well with routinely used assays and are suitable for clinical use.

Strain-specific neutralizing antibody responses against human cytomegalovirus envelope glycoprotein N

The human cytomegalovirus (HCMV) gM-gN complex is a major target of virus-neutralizing activity, and gN subtypes induce strain-specific antibodies. However, the biological significance of HCMV gN polymorphisms is not known. Neutralizing antibody responses against HCMV gN recombinant viruses were investigated at study entry in 80 healthy HCMV-seropositive women who were monitored for the appearance of new antibody specificities against linear strain-specific epitopes on glycoproteins gH and gB as evidence of HCMV reinfection. Neutralizing activity against all four gN recombinant viruses was seen in 74% of subjects, and 61% of subjects had strain-specific responses. Significantly fewer women (9/39 subjects [23%]) with serological evidence of reinfection had strain-specific neutralizing responses than the women without reinfection (21/41 subjects [51%]). Women with antibodies against at least one of the four linear gB and gH antigens at study entry had higher neutralizing titers against gN-1 (P = 0.006) and gN-2 (P = 0.007). Neutralizing titers of ≥400 against gN-3 (P = 0.043) and gN-4 (P = 0.049) at study entry were associated with longer times to serological evidence of reinfection. The findings demonstrate that HCMV gN elicits strain-specific neutralizing antibody responses and that broader anti-gN neutralizing activity may provide some protection from reinfection with a different virus strain.

Differential decay kinetics of human cytomegalovirus glycoprotein B genotypes following antiviral chemotherapy

Background

The impact of different cytomegalovirus (HCMV) glycoprotein B (gB) genotypes on pathogenesis remains controversial.

Objectives

To investigate the effect of gB genotypes either as single infections or as part of multiple infections on the early kinetics of response to ganciclovir therapy.

Methods

Patients (n = 239) enrolled in a study of intravenous ganciclovir or valganciclovir for the treatment of HCMV disease were analysed by a gB genotype specific PCR to quantify the amount of each gB genotype present at initiation of therapy (baseline, day 0) and at days 3, 7, 14 and 21 post therapy.

Results and conclusions

In all gB groups (individual gB genotype infections and mixed genotype infections) there was a biphasic decline in viral load after therapy. The first phase half life (days 0–3) was ≤1 day and was followed over the next 18 days by a slower second phase decline with half lives ranging from 3.4 to 4.4 days. The 1st phase rapid decline in viral load was dependent upon gB genotype whereas the ultimate viral load reduction at day 21 was relatively insensitive to gB genotype. A strong correlation between 1st phase decline and extent of viral load reduction at day 21 was observed (r = 0.37; p = 0.002). These data imply that early reductions in HCMV load after therapy may be useful in predicting the duration of drug therapy needed to control HCMV replication.

HSV-2: in pursuit of a vaccine

Herpes simplex virus type 2 (HSV-2) is one of the most prevalent sexually transmitted infections worldwide. In addition to recurrent genital ulcers, HSV-2 causes neonatal herpes, and it is associated with a 3-fold increased risk for HIV acquisition. Although many HSV-2 vaccines have been studied in animal models, few have reached clinical trials, and those that have been tested in humans were not consistently effective. Here, we review HSV-2 pathogenesis, with a focus on novel understanding of mucosal immunobiology of HSV-2, and vaccine efforts to date, in an attempt to stimulate thinking about future directions for development of effective prophylactic and therapeutic HSV-2 vaccines.

Rapid genotyping of cytomegalovirus in dried blood spots by multiplex real-time PCR assays targeting the envelope glycoprotein gB and gH genes

Genotyping of cytomegalovirus (CMV) is useful to examine potential differences in the pathogenicity of strains and to demonstrate coinfection with multiple strains involved in CMV disease in adults and congenitally infected newborns. Studies on genotyping of CMV in dried blood spots (DBS) are rare and have been hampered by the small amount of dried blood available. In this study, two multiplex real-time PCR assays for rapid gB and gH genotyping of CMV in DBS were developed. Validation of the assays with 39 CMV-positive plasma samples of transplant recipients and 21 urine specimens of congenitally infected newborns was successful in genotyping 100% of the samples, with gB1 and gB3 being the most prevalent genotypes. Multiple gB and gH genotypes were detected in 36% and 33% of the plasma samples, respectively. One urine sample from a newborn with symptomatic congenital CMV was positive for gB1 and gB2. DBS of congenitally infected newborns (n = 41) were tested using 9 μl of dried blood, and genotypes were detected in 81% (gB) and 73% (gH) of the samples, with gB3 being the most prevalent genotype. No clear association of specific genotypes with clinical outcome was observed. In conclusion, the CMV gB and gH PCR assays were found to be rapid, sensitive for detecting mixed infections, and suitable for direct usage on DBS. These assays are efficient tools for genotyping of CMV in DBS of congenitally infected newborns.

Mixed infection and strain diversity in congenital cytomegalovirus infection

BACKGROUND

Cytomegalovirus (CMV), the most common cause of congenital infection, exhibits extensive genetic variability. We sought to determine whether multiple CMV strains can be transmitted to the fetus and to describe the distribution of genotypes in the saliva, urine, and blood.

METHODS

Study subjects consisted of a convenience sampling of 28 infants found to be CMV-positive on newborn screening as part of an ongoing study. Genotyping was performed on saliva specimens obtained during newborn screening and urine, saliva, and blood obtained at a later time point within the first 3 weeks of life.

RESULTS

Six (21.4%) of the 28 saliva samples obtained within the first 2 days of life contained >1 CMV genotype. Multiple CMV genotypes were found in 39% (5/13) of urine, saliva, and blood samples obtained within the first 3 weeks of life from 13 of the 28 newborns. There was no predominance of a CMV genotype at a specific site; however, 4 infants demonstrated distinct CMV strains in different compartments.

CONCLUSIONS

Infection with multiple CMV strains occurs in infants with congenital CMV infection. The impact of intrauterine infection with multiple virus strains on the pathogenesis and long-term outcome remains to be elucidated.

Human cytomegalovirus glycoprotein B genotypes in Chinese hematopoietic stem cell transplant recipients

OBJECTIVES

To investigate the distribution of human cytomegalovirus (HCMV) glycoprotein B (gB) genotypes and to explore the possible relationship between gB genotypes and clinical characteristics in Chinese hematopoietic stem cell transplant (HSCT) recipients.

METHODS

A prospective analysis of gB genotypes was conducted on HCMV clinical isolates obtained from 102 HSCT recipients. Real-time quantitative PCR and PCR-based restriction fragment length polymorphism analysis were applied for the determination of viral loads and gB genotypes, respectively.

RESULTS

The distribution of gB genotypes was as follows: gB1, 54/102 (52.9%); gB3, 21/102 (20.6%); and mixtures, 27/102 (26.5%). The rate of viral clearance at day 21 was higher in patients infected with the gB1 genotype than in those infected with the gB3 genotype (56 and 29%, respectively; p = 0.036). In contrast, the rate of HCMV reactivation/reinfection was higher in patients infected with the gB3 genotype than in those infected with the gB1 genotype (81 and 56%, respectively; p = 0.041).

CONCLUSIONS

The HCMV gB1 genotype is the most prevalent among Chinese HSCT recipients; patients infected with the gB3 genotype have more difficulty eradicating the virus and have a higher risk of reactivation/reinfection than those infected with the gB1 genotype.

Review of cytomegalovirus shedding in bodily fluids and relevance to congenital cytomegalovirus infection

Congenital cytomegalovirus (CMV) infections are a leading cause of sensorineural hearing loss (SNHL) and neurological impairment. Congenital transmission of CMV can occur with maternal primary infection, reactivation, or reinfection during pregnancy. We reviewed studies of CMV shedding in bodily fluids (defined as CMV detected by culture or CMV DNA detected by polymerase chain reaction). Following diagnosis at birth, children with congenital CMV infection exhibited the highest prevalences of CMV shedding (median = 80%, number of sample population prevalences [N] = 6) and duration of shedding, with a steep decline by age five. Healthy children attending day care shed more frequently (median = 23%, N = 24) than healthy children not attending day care (median = 12%, N = 11). Peak shedding prevalences in children occurred at 1-2 years of age, confirming that young children are the key transmission risk for pregnant women. CMV shedding among children was more prevalent in urine specimens than in oral secretions (median prevalence difference = 11.5%, N = 12). Adults with risk factors such as STD clinic attendance had higher shedding prevalences (median = 22%, N = 20) than adults without risk factors (median = 7%, N = 44). In adults with risk factors, CMV was shed more frequently in urine; in adults without risk factors genital shedding was most common. The prevalence of CMV shedding in nine sample populations of pregnant women increased with advancing gestation. In seven sample populations of children with congenital CMV infection, higher viral load at birth was consistently associated with an elevated risk of SNHL. Higher CMV viral load at birth also consistently correlated with the presence of symptoms of congenital CMV at birth. Published 2011. This article is a US Government work and is in the public domain in the USA.