Comparative analysis of sequence variation in gp116 and gp55 components of glycoprotein B of human cytomegalovirus

Cytomegalovirus Genetic Diversity and Evolution: Insights into Genotypes and Their Role in Viral Pathogenesis

Cytomegalovirus (CMV) is a ubiquitous virus that infects most of the human population and causes significant morbidity and mortality, particularly among immunocompromised individuals. Understanding CMV's genetic diversity and evolutionary dynamics is crucial for elucidating its pathogenesis and developing effective therapeutic interventions. This review provides a comprehensive examination of CMV's genetic diversity and evolution, focussing on the role of different genotypes in viral pathogenesis.

Multivalent cytomegalovirus glycoprotein B nucleoside modified mRNA vaccines did not demonstrate a greater antibody breadth

Human cytomegalovirus (HCMV) remains the most common congenital infection and infectious complication in immunocompromised patients. The most successful HCMV vaccine to date, an HCMV glycoprotein B (gB) subunit vaccine adjuvanted with MF59, achieved 50% efficacy against primary HCMV infection. A previous study demonstrated that gB/MF59 vaccinees were less frequently infected with HCMV gB genotype strains most similar to the vaccine strain than strains encoding genetically distinct gB genotypes, suggesting strain-specific immunity accounted for the limited efficacy. To determine whether vaccination with multiple HCMV gB genotypes could increase the breadth of anti-HCMV gB humoral and cellular responses, we immunized 18 female rabbits with monovalent (gB-1), bivalent (gB-1+gB-3), or pentavalent (gB-1+gB-2+gB-3+gB-4+gB-5) gB lipid nanoparticle-encapsulated nucleoside-modified RNA (mRNA-LNP) vaccines. The multivalent vaccine groups did not demonstrate a higher magnitude or breadth of the IgG response to the gB ectodomain or cell-associated gB compared to that of the monovalent vaccine. Also, the multivalent vaccines did not show an increase in the breadth of neutralization activity and antibody-dependent cellular phagocytosis against HCMV strains encoding distinct gB genotypes. Interestingly, peripheral blood mononuclear cell-derived gB-2-specific T-cell responses elicited by multivalent vaccines were of a higher magnitude compared to that of monovalent vaccinated animals against a vaccine-mismatched gB genotype at peak immunogenicity. Yet, no statistical differences were observed in T cell response against gB-3 and gB-5 variable regions among the three vaccine groups. Our data suggests that the inclusion of multivalent gB antigens is not an effective strategy to increase the breadth of anti-HCMV gB antibody and T cell responses. Understanding how to increase the HCMV vaccine protection breadth will be essential to improve the vaccine efficacy.

Prognosis of Human Cytomegalovirus in Cancer Patients Undergoing Chemotherapeutic Treatment in Egypt and an Emergent Prevalence of Glycoprotein B-5

The human cytomegalovirus (HCMV) is a global opportunistic β-herpes virus causing severe diseases in immune-compromised patients, such as malignant tumor patients, especially those undergoing chemotherapeutic treatment. This study aimed to determine the prevalence of HCMV-DNA in chemotherapeutic treatment naive cancer patients, and after chemotherapy, to compare between conventional nested PCR and ELISA techniques for the detection of HCMV, and to detect glycoprotein B genotypes. Plasma and serum samples before and after three chemotherapy cycles were collected from 49 chemotherapy-naive cancer patients. DNA was extracted from plasma samples using QIAamp® DNA Mini kit. HCMV-DNA was detected using a nested PCR technique. Multiplex nested PCR was used for HCMV-glycoprotein B (gB) genotyping. HCMV-IgG and -IgM were detected using ELISA technique. Thirty one (63.3 %) of the 49 plasma samples of the chemotherapy-naïve cancer patients were positive for HCMV-DNA; 21 of which remained positive after chemotherapy. However, 18 samples were negative of which 16 became positive after chemotherapy. gB-5 was the most common glycoprotein genotype detected (80.6 %), followed by gB-1, gB-3, gB-4, and gB-2. HCMV IgG was detected in the 49 serum samples of chemotherapy-naïve patients, and after exposure to chemotherapy. HCMV-DNA is commonly identified in cancer patients. Its detection after chemotherapy exposure may suggest HCMV reactivation. The most common genotype detected in cancer patients in Egypt is gB-5 in contrast to earlier research. IgG was detected in all patients. This indicates that HCMV is endemic in Egypt, necessitating the development of public awareness campaigns about HCMV infection and preventive strategies.

A Novel Strain-Specific Neutralizing Epitope on Glycoprotein H of Human Cytomegalovirus

Human cytomegalovirus (HCMV) is a ubiquitous pathogen that causes severe clinical disease in immunosuppressed patients and congenitally infected newborn infants. Viral envelope glycoproteins represent attractive targets for vaccination or passive immunotherapy. To extend the knowledge of mechanisms of virus neutralization, monoclonal antibodies (MAbs) were generated following immunization of mice with HCMV virions. Hybridoma supernatants were screened for in vitro neutralization activity, yielding three potent MAbs, 6E3, 3C11, and 2B10. MAbs 6E3 and 3C11 blocked infection of all viral strains that were tested, while MAb 2B10 neutralized only 50% of the HCMV strains analyzed. Characterization of the MAbs using indirect immunofluorescence analyses demonstrated their reactivity with recombinantly derived gH. While MAbs 6E3 and 3C11 reacted with gH when expressed alone, 2B10 detected gH only when it was coexpressed with gB and gL. Recognition of gH by 3C11 was dependent on the expression of the entire ectodomain of gH, whereas 6E3 required residues 1 to 629 of gH. The strain-specific determinant for neutralization by Mab 2B10 was identified as a single Met→Ile amino acid polymorphism within gH, located within the central part of the protein. The polymorphism is evenly distributed among described HCMV strains. The 2B10 epitope thus represents a novel strain-specific antibody target site on gH of HCMV. The dependence of the reactivity of 2B10 on the simultaneous presence of gB/gH/gL will be of value in the structural definition of this tripartite complex. The 2B10 epitope may also represent a valuable tool for diagnostics to monitor infections/reinfections with different HCMV strains during pregnancy or after transplantation. IMPORTANCE HCMV infections are life threatening to people with compromised or immature immune systems. Understanding the antiviral antibody repertoire induced during HCMV infection is a necessary prerequisite to define protective antibody responses. Here, we report three novel anti-gH MAbs that potently neutralized HCMV infectivity. One of these MAbs (2B10) targets a novel strain-specific conformational epitope on gH that only becomes accessible upon coexpression of the minimal fusion machinery gB/gH/gL. Strain specificity is dependent on a single amino acid polymorphism within gH. Our data highlight the importance of strain-specific neutralizing antibody responses against HCMV. The 2B10 epitope may also represent a valuable tool for diagnostics to monitor infections/reinfections with different HCMV strains during pregnancy or after transplantation. In addition, the dependence of the reactivity of 2B10 on the simultaneous presence of gB/gH/gL will be of value in the structural definition of this tripartite complex.

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

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

Trends and strategies to combat viral infections: A review on FDA approved antiviral drugs

The infectious microscopic viruses invade living cells to reproduce themselves, and causes chronic infections such as HIV/AIDS, hepatitis B and C, flu, etc. in humans which may lead to death if not treated. Different strategies have been utilized to develop new and superior antiviral drugs to counter the viral infections. The FDA approval of HIV nucleoside reverse transcriptase inhibitor, zidovudine in 1987 boosted the development of antiviral agents against different viruses. Currently, there are a number of combination drugs developed against various viral infections to arrest the activity of same or different viral macromolecules at multiple stages of its life cycle; among which majority are targeted to interfere with the replication of viral genome. Besides these, other type of antiviral molecules includes entry inhibitors, integrase inhibitors, protease inhibitors, interferons, immunomodulators, etc. The antiviral drugs can be toxic to human cells, particularly in case of administration of combination drugs, and on the other hand viruses can grow resistant to the antiviral drugs. Furthermore, emergence of new viruses like Ebola, coronaviruses (SARS-CoV, SARS-CoV-2) emphasizes the need for more innovative strategies to develop better antiviral drugs to fight the existing and the emerging viral infections. Hence, we reviewed the strategic enhancements in developing antiviral drugs for the treatment of different viral infections over the years.

Human cytomegalovirus envelope glycoprotein B, H, and N polymorphisms among infants of Shanghai area in China

Human cytomegalovirus (HCMV) is the leading cause of congenital infection and an opportunistic pathogen capable of establishing lifelong latency. In the present study, we aimed to investigate the distribution of glycoprotein B, H, and N in infants of Shanghai and correlate the genotype with active and latent HCMV infection. A total of 129 urine samples were collected between August 2014 and December 2015 from infants under 3 years with HCMV infection. Nested PCR was used to amplify the regions of UL55 (gB), UL75 (gH), and UL73 (gN). Gene sequencing and phylogenetic analyses were used to classify the genotypes. Overall, regarding gB, gB1 (57.27%) was predominant, followed by gB3 (41.82%) and gB4 (0.91%). gH1 (54.33%) was the most prevalent genotype of gH, followed by gH2 (45.67%). Concerning gN, we detected gN1 (17.44%), gN2 (2.33%), gN3a (29.07%), gN3b (8.14%), gN4a (13.95%), gN4b (15.12%), and gN4c (13.95%), among which gN3a was the dominant genotype. All the expected genotypes were present except gB2 in children with active infection: gB1 (56.25%), gB3 (42.5%), gB4 (1.25%), gH1 (58.70%), gH2 (41.30%), gN1 (19.05%), gN2 (3.17%), gN3a (25.40%), gN3b (6.35%), gN4a (15.87%), gN4b (17.46%), and gN4c (12.70%). However, among latent cases, we detected gB1 (60%), gB3 (40%), gH1 (42.86%), gH2 (57.14%), gN1 (13.04%), gN3a (39.13%), gN3b (13.04%), gN4a (8.70%), gN4b (8.70%), and gN4c (17.39%), respectively. gB2, gB4, and gN2 were absent in this group. The results revealed that gB1, gH1, and gN3a were predominant in the infants of Shanghai. gH showed different trends among children with active and latent infection.

Role of antibodies in confining cytomegalovirus after reactivation from latency: three decades' résumé

Cytomegaloviruses (CMVs) are highly prevalent herpesviruses, characterized by strict species specificity and the ability to establish non-productive latent infection from which reactivation can occur. Reactivation of latent human CMV (HCMV) represents one of the most important clinical challenges in transplant recipients secondary to the strong immunosuppression. In addition, HCMV is the major viral cause of congenital infection with severe sequelae including brain damage. The accumulated evidence clearly shows that cellular immunity plays a major role in the control of primary CMV infection as well as establishment and maintenance of latency. However, the efficiency of antiviral antibodies in virus control, particularly in prevention of congenital infection and virus reactivation from latency in immunosuppressed hosts, is much less understood. Because of a strict species specificity of HCMV, the role of antibodies in controlling CMV disease has been addressed using murine CMV (MCMV) as a model. Here, we review and discuss the role played by the antiviral antibody response during CMV infections with emphasis on latency and reactivation not only in the MCMV model, but also in relevant clinical settings. We provide evidence to conclude that antiviral antibodies do not prevent the initiating molecular event of virus reactivation from latency but operate by preventing intra-organ spread and inter-organ dissemination of recurrent virus.

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.

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.

Virion Glycoprotein-Mediated Immune Evasion by Human Cytomegalovirus: a Sticky Virus Makes a Slick Getaway

The prototypic herpesvirus human cytomegalovirus (CMV) exhibits the extraordinary ability to establish latency and maintain a chronic infection throughout the life of its human host. This is even more remarkable considering the robust adaptive immune response elicited by infection and reactivation from latency. In addition to the ability of CMV to exist in a quiescent latent state, its persistence is enabled by a large repertoire of viral proteins that subvert immune defense mechanisms, such as NK cell activation and major histocompatibility complex antigen presentation, within the cell. However, dissemination outside the cell presents a unique existential challenge to the CMV virion, which is studded with antigenic glycoprotein complexes targeted by a potent neutralizing antibody response. The CMV virion envelope proteins, which are critical mediators of cell attachment and entry, possess various characteristics that can mitigate the humoral immune response and prevent viral clearance. Here we review the CMV glycoprotein complexes crucial for cell attachment and entry and propose inherent properties of these proteins involved in evading the CMV humoral immune response. These include viral glycoprotein polymorphism, epitope competition, Fc receptor-mediated endocytosis, glycan shielding, and cell-to-cell spread. The consequences of CMV virion glycoprotein-mediated immune evasion have a major impact on persistence of the virus in the population, and a comprehensive understanding of these evasion strategies will assist in designing effective CMV biologics and vaccines to limit CMV-associated disease.

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.

A new look at a poorly immunogenic neutralization epitope on cytomegalovirus glycoprotein B. Is there cause for antigen redesign?

The immune response is able to control cytomegalovirus infection in most subjects. However, in some patient groups the virus is not well contained resulting in disease and severe morbidity. The development of efficacious vaccines is therefore a high priority. Antibodies may contribute to protection against disease caused by CMV but the most efficient targets for protective humoral immunity are not precisely known. Glycoprotein B (gB) is a protein that is targeted by virus-neutralizing antibodies. One epitope on gB, AD-2, is poorly immunogenic following natural infection and vaccination. It is consequently not effectively exploited as a target for antibodies by the immune system. However, antibodies specific for this epitope, when they develop, display important functional activities that may play a role in protection against infection. In this study critical features of human antibody recognition of this epitope are re-assessed based on structural and immunochemical data. The analysis suggests that the immune system may only be able to develop an AD-2 specific antibody response through rare, very specific rearrangement events that by chance create a naïve B cell that can be recruited into an AD-2 specific immune response. These results reinvigorate the notion that if we are to be able to effectively exploit AD-2 specific humoral immunity we need to readdress the nature of the antigen incorporated into vaccines so as to more effectively recruit B cells into the response against this epitope.

Rapid intrahost evolution of human cytomegalovirus is shaped by demography and positive selection

Populations of human cytomegalovirus (HCMV), a large DNA virus, are highly polymorphic in patient samples, which may allow for rapid evolution within human hosts. To understand HCMV evolution, longitudinally sampled genomic populations from the urine and plasma of 5 infants with symptomatic congenital HCMV infection were analyzed. Temporal and compartmental variability of viral populations were quantified using high throughput sequencing and population genetics approaches. HCMV populations were generally stable over time, with ~88% of SNPs displaying similar frequencies. However, samples collected from plasma and urine of the same patient at the same time were highly differentiated with approximately 1700 consensus sequence SNPs (1.2% of the genome) identified between compartments. This inter-compartment differentiation was comparable to the differentiation observed in unrelated hosts. Models of demography (i.e., changes in population size and structure) and positive selection were evaluated to explain the observed patterns of variation. Evidence for strong bottlenecks (>90% reduction in viral population size) was consistent among all patients. From the timing of the bottlenecks, we conclude that fetal infection occurred between 13-18 weeks gestational age in patients analyzed, while colonization of the urine compartment followed roughly 2 months later. The timing of these bottlenecks is consistent with the clinical histories of congenital HCMV infections. We next inferred that positive selection plays a small but measurable role in viral evolution within a single compartment. However, positive selection appears to be a strong and pervasive driver of evolution associated with compartmentalization, affecting ≥ 34 of the 167 open reading frames (~20%) of the genome. This work offers the most detailed map of HCMV in vivo evolution to date and provides evidence that viral populations can be stable or rapidly differentiate, depending on host environment. The application of population genetic methods to these data provides clinically useful information, such as the timing of infection and compartment colonization.

Cytomegalovirus (CMV) genotype in allogeneic hematopoietic stem cell transplantation

Background

Based on sequence variation in the UL55 gene that encodes glycoprotein B (gB), human cytomegalovirus (CMV) can be classified into four gB genotypes. Previous studies have suggested an association between CMV gB genotype and clinical outcome in patients who underwent an allogeneic hematopoietic stem cell transplant (HSCT). The goals of this study were identify patients with active infection caused by CMV in recipients of HSCT; determine the prevalence of CMV genotypes in the study group; correlate genotype with CMV disease, acute GVHD and overall survival.

Methods

The diagnosis of active CMV infection after allogeneic HSCT was detected by antigenemia (AGM) and/or nested-PCR (N-PCR). Positive samples from patients with active CMV infection were submitted to genotyping using N-PCR to amplify a region of UL55, followed by restriction analysis based on HinfI and RsaI digestion. Real-time PCR (qPCR) was used to determine the viral load during active CMV infection and antiviral treatment.

Results

Sixty-three allogeneic HSCT recipients were prospectively evaluated; 49/63 (78%) patients were infected with CMV genotypes – gB1 19/49 (39%), gB2 17/49 (35%), gB3 3/49 (6%), gB4 7/49 (14%) – and 3 (6%) had mixed CMV genotypes (gB1 + gB3, gB1 + gB4 and gB2 + gB4). Characterized by gastrointestinal disease, CMV disease occurred in 3/49 (6.1%) patients, who had CMV gB3 genotype. These gB3 genotype patients presented an increasing AGM number, mean 125 (± 250) (P = 0.70), and qPCR copies/ml, mean 37938 (SD ± 50542) (P = 0.03), during antiviral treatment, when compared with other CMV genotypes. According to CMV genotypes, stratified overall survival was 55% for gB1, 43% for gB2; 0% for gB3 and 57% for gB4 (P = 0.03).

Conclusions

One of the restrictions of the presented study was the low number of CMV gB sub-cohorts). However, we demonstrated that the frequency of active CMV infection in this HSCT population was high, and the most prevalent genotype in these patients with active CMV infection was gB1 and gB2 genotype (74%). In Brazil, HSCT recipients seem to carry mainly gB1 and gB2 CMV genotype.

Quantification of cytomegalovirus glycoprotein Bn DNA in hematopoietic stem cell transplant recipients by real-time PCR

Based on sequence variation in the N-terminus of the UL55 gene, which encodes glycoprotein B (gB), human cytomegalovirus (CMV) can be classified into four gBn genotypes. We assessed the distribution of CMV gBn genotypes and the correlation between CMV gBn DNA (detected by real-time PCR) and CMV-positive pp65 cells (identified by immunohistochemical staining) in a cohort of hematopoietic stem cell transplant patients. The distribution of gB genotypes was as follows: gBn1, 60% of patients; gBn2, 13.3%; mixed gBn1 and gBn3 infection, 26.7%; and gBn4 and other mixed infections, 0%. CMV gBn1 was the most common genotype. The detected level of CMV gB DNA correlated well with the number of CMV-positive pp65 cells detected by immunostaining (r = 0.585).

The genetic basis of human cytomegalovirus resistance and current trends in antiviral resistance analysis

Infections due to resistant human cytomegalovirus (CMV) are an emerging problem, particularly in immunocompromised hosts. When managing such patients, clinicians should be aware of the possibility of developing CMV antiviral resistance, especially while on prolonged therapy or if severe immunosuppression is present. CMV resistance to current antiviral agents is mediated by alterations in either the UL97 kinase or DNA polymerase, encoded by the UL97 and UL54 genes, respectively. UL97 mutations are capable of conferring resistance to ganciclovir, while UL54 mutations can impart resistance to ganciclovir, cidofovir, and foscarnet. If treatment failure is suspected to be due to antiviral resistance, CMV resistance analysis should be obtained. Phenotypic resistance assays performed on clinical isolates measure antiviral susceptibilities directly, but are laborious and time-consuming. Therefore, genotypic resistance analysis has become the more common means of diagnosing CMV resistance. Mutations in UL97 or UL54 may be clinically associated with resistance, but their effect on antiviral susceptibility must be confirmed by marker transfer techniques such as recombinant phenotyping.

Extensive genome-wide variability of human cytomegalovirus in congenitally infected infants

Research has shown that RNA virus populations are highly variable, most likely due to low fidelity replication of RNA genomes. It is generally assumed that populations of DNA viruses will be less complex and show reduced variability when compared to RNA viruses. Here, we describe the use of high throughput sequencing for a genome wide study of viral populations from urine samples of neonates with congenital human cytomegalovirus (HCMV) infections. We show that HCMV intrahost genomic variability, both at the nucleotide and amino acid level, is comparable to many RNA viruses, including HIV. Within intrahost populations, we find evidence of selective sweeps that may have resulted from immune-mediated mechanisms. Similarly, genome wide, population genetic analyses suggest that positive selection has contributed to the divergence of the HCMV species from its most recent ancestor. These data provide evidence that HCMV, a virus with a large dsDNA genome, exists as a complex mixture of genome types in humans and offer insights into the evolution of the virus.

Human Cytomegalovirus (HCMV) is a dsDNA virus that is the leading source of birth defects associated with an infectious agent. There is currently no effective HCMV vaccine and few treatment strategies for congenital infections exist. Thus, a better understanding of HCMV infections is warranted. Limited data has shown that HCMV exists as a mixture of a few genotypes in human hosts. Here, we describe our use of high throughput sequencing to study the extent of genome wide variability within HCMV infections sampled from congenital infections. Surprisingly, we find that HCMV populations are as variable as quasispecies RNA viruses; it is commonly believed that DNA viruses are more genetically stable than RNA viruses, and thus produce homogenous populations. Additionally, we find evidence of evolutionary pressures acting on the HCMV genome, both within and among populations. These results provide the first evidence that diversity of DNA virus populations can be comparable to that of RNA virus populations.

Glycoprotein C Gene of Caprine Herpesvirus Type 1 Contains Short Sequence Repeats (SSR)

Caprine herpesvirus 1 (CpHV-1) is responsible for vaginal and respiratory disease in goats. Infection by vaginal route is usually restricted to the genital tract whereas by nasal route the virus can spread throughout the body. In order to evaluate genomic diversity, nucleotide sequences of glycoprotein C (gC) of 13 (n.8 vaginal, n.5 nasal) CpHV-1 strains were analyzed. Amino acid (aa) sequences showed a variable number of short sequence repeats (SSR). Nucleotide and amino acid sequences of amplified products showed to contain a variable number of short sequence repeats among the examined strains. These results indicated that CpHV-1 isolates had genetic diversity in the gC gene regarding the number of SSR: 4 SSR of 60 bp in one strain, 2 SSR of 30 bp in seven strains and 1 SSR of 15 bp in three strains. Two strains had no SSR.

Cytomegalovirus blood viral load and hearing loss in young children with congenital infection

BACKGROUND

This study was designed to determine whether elevated viral load in infants and young children is associated with congenital cytomegalovirus (CMV)-related hearing loss.

METHODS

Blood samples were obtained from 135 children with congenital CMV infection. CMV DNA in the peripheral blood was quantitated with a real-time polymerase chain reaction assay. Viral load measurements were analyzed in 3 different age groups (<2 months, 2-12 months, 12-36 months).

RESULTS

In children with symptomatic and asymptomatic infection, CMV DNA levels were not different between children with hearing deficit and those with normal hearing in all 3 age groups. In children with asymptomatic infection, the positive predictive value of a peripheral blood viral load >3500 genomic equivalents per milliliter (ge/mL) at <2 months and 2 to 12 months of age is 8%, and at 12 to 36 months of age is 11.8%. However, the negative predictive value of a viral load <3500 ge/mL is 94.4% at <2 months of age, and 100% at 2 to 36 months of age.

CONCLUSIONS

Peripheral blood viral load is not associated with hearing loss in children with congenital CMV infection. However, a viral load of <3500 ge/mL is associated with a lower risk of hearing loss in children born with asymptomatic congenital infection.

Enzyme-linked immunosorbent assay method for detection of cytomegalovirus strain-specific antibody responses

Reliable methods for the detection of cytomegalovirus (CMV) strain-specific serological responses are lacking. We describe a simple and reliable enzyme-linked immunosorbent assay method developed to detect antibodies against the polymorphic epitopes within the two envelope glycoproteins of CMV, glycoproteins H and B. This assay is useful for the detection of serologic responses to CMV strains and the identification of CMV reinfections.

Genetic variations in the gB, UL144 and UL149 genes of human cytomegalovirus strains collected from congenitally and postnatally infected Japanese children

Human cytomegalovirus (CMV) is the leading cause of intrauterine viral infection. The association of genetic polymorphisms in some particular genes with the incidence and severity of congenital infection has been controversial. To address this issue, we analyzed the genotypes of the glycoprotein B (gB), UL144 and UL149 genes of CMV clinical strains obtained from 33 congenitally and 31 postnatally infected Japanese children. Our results demonstrated that (1) CMV strains with any combination of genotypes could be vertically transmitted from mother to fetus, potentially causing neurological abnormalities, (2) the gB3 genotype was more prevalent in the congenital cases than in postnatally infected children (P < 0.05), particularly in congenital cases with sensorineural hearing loss (P = 0.009), (3) there was no relationship between gB genotype and viral load in the urine and dried umbilical cord specimens in the congenital cases, and (4) the UL144 and UL149 genotype distributions had no bias for congenial infection. In future studies, it would be interesting to see whether the gB genotypes serve as a prognostic indicator of CMV-associated diseases.

Cytomegalovirus strain diversity in seropositive women

Infection and reinfection with multiple cytomegalovirus (CMV) strains have been shown to occur in immunocompromised individuals, sexually transmitted disease clinic attendees, and children attending day care centers. To characterize the CMV diversity in healthy seropositive individuals, 16 CMV PCR-positive specimens from 113 seropositive women were analyzed for glycoprotein gN and gB genotypes by cloning, followed by nucleotide sequencing of the plasmid DNA and/or restriction fragment length polymorphism (RFLP). The results showed that most (93.7%) of the PCR-positive specimens contained multiple gN and/or gB genomic variants, suggesting that the majority of women were infected with more than one virus strain. The results also showed that the RFLP technique might not be sufficiently sensitive to detect all of the genomic variants present in a sample.

Genetic variation within the glycoprotein B and H genes of human cytomegalovirus in solid organ transplant recipients

This study was performed to investigate human cytomegalovirus (HCMV) infection and genetic variations within glycoprotein B (gB) and H (gH) genes in Chinese transplant recipients. A total of 245 ethylene-diamine tetraacetic acid (EDTA)-treated blood samples were obtained from 79 transplant recipients in southeast China. Based on the sequences of highly variable regions of the gB endoprotease cleavage site (gBclv), N-terminus of gp116 (gBn), and the gH N-terminus (gH), nested polymerase chain reaction assays for the detection of HCMV were established. Nucleotide sequencing was employed to differentiate gB and gH genotypes. Twenty-six of 79 (32.9%) transplant recipients were proved HCMV positive. The distribution of genotypes was gBclv1, 12/25; gBclv2, 3/25; gBclv3, 4/25; gBn1, 6/23; gBn2, 2/23; gBn3, 11/23; and no gBclv/n 4-related genotypes were presented. The distribution of gH genotypes was gH1, 11/26; gH2, 9/26; and co-infected with both gH1/2 in 6/26. These data show that genetic variability within the gB genes occurs frequently. Mixtures of gB and gH genotypes infection were common in Chinese solid organ transplant recipients.

Divergence and recombination of clinical herpes simplex virus type 2 isolates

Herpes simplex virus type 2 (HSV-2) infects the genital mucosa and is one of the most common sexually transmitted viruses. Here we sequenced a segment comprising 3.5% of the HSV-2 genome, including genes coding for glycoproteins G, I, and E, from 27 clinical isolates from Tanzania, 10 isolates from Norway, and 10 isolates from Sweden. The sequence variation was low compared to that described for clinical HSV-1 isolates, with an overall similarity of 99.6% between the two most distant HSV-2 isolates. Phylogenetic analysis revealed a divergence into at least two genogroups arbitrarily designated A and B, supported by high bootstrap values and evolutionarily separated at the root. Genogroup A contained isolates collected in Tanzania, and genogroup B contained isolates collected in Tanzania and Scandinavia, implying that the genetic variability of HSV-2 is higher in Tanzania than in Scandinavia. Recombination network analysis and bootscan analysis revealed a complex pattern of phylogenetically conflicting informative sites in the sequence alignments. These signals were present in synonymous and nonsynonymous sites in all three genes and were not accumulated in specific regions, observations arguing against positive selection. Since the PHI test applied solely to synonymous sites revealed a high statistical probability of recombination, we suggest as a novel finding that homologous recombination is, as reported earlier for HSV-1 and varicella-zoster virus, a prominent feature in the evolution of HSV-2.

DNA vaccines expressing glycoprotein complex II antigens gM and gN elicited neutralizing antibodies against multiple human cytomegalovirus (HCMV) isolates

Human cytomegalovirus (HCMV) glycoprotein complex II (gcII) consists of two glycoproteins, gM and gN. Although gcII specific IgG purified from HCMV positive patient sera can neutralize HCMV, there has been no report describing the generation of virus-neutralizing antibodies by immunization with individual recombinant gM or gN antigens. In the current study, gM and gN antigens were expressed by the mammalian expression vector pJW4303 and used as DNA vaccines to determine the immunogenicity of these proteins. Sera from mice or rabbits immunized with individual or combinations of gM and gN DNA vaccines contained gM and gN specific antibodies as confirmed by ELISA and Western blot analyses. The combined gM and gN antigens induced the strongest antibody responses that recognized both gM and gcII complex while gM DNA vaccine alone could only elicit antibody specific for gM antigen. When given alone, the gN DNA vaccine did not induce detectable gcII specific antibody even though in vitro gN expression was confirmed by the formation of gM/gN complex in FSK cells using a gN-specific monoclonal antibody 14-16A. The neutralizing antibody titer of anti-gM/gN sera (1:128) was higher than that of anti-gM sera (1:32) against the autologous virus, HCMV AD169. Heterologous HCMV strains including Towne and Davis could also be neutralized by the anti-gM/gN antisera. Our data supported the rationale for the use of the HCMV gM/gN protein complex as protective antigens for subunit based HCMV vaccine development. DNA vaccination is an effective approach to express the gM/gN antigen complex in vivo without the need to express and purify these highly insoluble and structurally complicated antigens.

Contrasting geographic distribution profiles of the herpes simplex virus type 1 BgOL and BgKL variants in Japan suggest dispersion and replacement

Thelifelong latent infection-reactivation mode of infection of herpes simplex virus type 1 (HSV-1) transmitted by close contact has allowed a diversity of restriction fragment length polymorphism (RFLP) variations to accumulate in human populations. Whether and how the variants of the HSV-1 that is ubiquitous worldwide spread to different human populations is not clear. In our previous study the geographically gradient distribution of the HSV-1 BgK(L) variant, which is a good marker for the BgK(L):SaCFJ(M):SaGH(M):SaD/E(L):KpM(S) variant, suggested that BgK(L) dispersed geographically. Southern hybridization analyses showed that in BgK(L) the BglII cleavage site between the BglII K and small "Q/#13" fragments is lost, the SalI cleavage sites between the SalI J and C and between SalI F and J fragments are lost, and the SalI E fragment is abnormally large (SaE(L) variation). The RFLP and geographic distribution of one more HSV-1 RFLP variant, BgO(L), were comparatively analyzed. The BglII cleavage site between the BglII O and Q/#13 fragments is lost in BgOL. BgO(L) clinical isolates were not associated with any of the SaCFJ(M), SaE(L), SaGH(M), or KpM(S) variations, whereas one-fourth of the non-BgO(L):non-BgK(L) isolates was associated with SaCFJ(M) and SaGH(M), indicating that BgK(L) and BgO(L) are distant in terms of diversification. BgO(L) is distributed highly in the northeastern region and the southwestern island of Kyushu but is rare between the two regions in Japan, in a remarkable contrast to BgK(L). These are the first epidemiologic data to show contrasting geographic distribution profiles of two HSV-1 variants and suggest the gradual dispersion and replacement of HSV-1 variants.

A full-genome phylogenetic analysis of varicella-zoster virus reveals a novel origin of replication-based genotyping scheme and evidence of recombination between major circulating clades

Varicella-zoster virus (VZV) is a remarkably stable virus that until recently was thought to exhibit near-universal genetic homogeneity among circulating wild-type strains. In recent years, the expanding knowledge of VZV genetics has led to a number of groups proposing sequence-based typing schemes, but no study has yet examined the relationships between VZV genotypes at a full-genome level. A central hypothesis of this study is that VZV has coevolved with humankind. In this study, 11 additional full VZV genomic sequences are presented, bringing the current number of complete genomic sequences publicly available to 18. The full-genome alignment contained strains representing four distinct clades, but the possibility exists that a fifth clade comprised of African and Asian-like isolates was not represented. A consolidated VZV genotyping scheme employing the origin-associated region between reiteration region R4 and open reading frames (ORFs) 63 and 70 is described, one which accurately categorizes strains into one of four clades related to the geographic origin of the isolates. The full-genome alignment also provided evidence for recombination having occurred between the major circulating VZV clades. One Canadian clinical isolate was primarily Asian-like in origin, with most of the genome showing strong sequence identity to the Japanese-like clade B, with the exceptions being two putative recombination regions, located in ORFs 14 to 17 and ORFs 22 to 26, which showed clear similarity to the European/North American clade A. The very low rate of single-nucleotide polymorphisms scattered across the genome made full-genome sequencing the only definitive method for identifying specific VZV recombination events.

Cytomegalovirus disease in the era of highly active antiretroviral therapy (HAART)

Cytomegalovirus (CMV) infection was one of the most important opportunistic infections in HIV-infected patients before the introduction of highly active antiretroviral therapy (HAART), i.e. the combination of at least three antiretroviral drugs of different classes. Thereafter, life expectancy and quality of life increased dramatically with the persistent suppression of HIV viremia and a significant reduction in incidence of CMV disease. Nevertheless, evidence for a multitude of direct and indirect effects of CMV on HIV progression is accumulating. Even in the era of HAART, a considerable number of HIV-infected patients have a CD4 cell count below <100 mm(-3), which involves a high risk for CMV disease. The focus of the present review is on interpretation of test results, their predictive value for CMV disease, and guidance for the rational use of diagnostic assays in HIV-infected patients. Identification of patients at immediate risk for CMV disease may be accomplished by detection of CMV-DNA in leucocytes or plasma. Evidence is growing that CMV genotypes may be also relevant for the risk of CMV disease. Diagnosis of CMV disease requires in most instances demonstration of virus in biopsy specimen from the affected organ because presence of CMV in blood may not be causally related to symptoms observed. Clinical symptoms and patient characteristics are essential in the interpretation of laboratory test results and may guide the rational collection of clinical specimen and use of laboratory assays. As a consequence, a reliable diagnosis of CMV disease and early identification of patients at high risk for CMV disease requires an integrated interpretation of clinical and virological information.

Analysis of equid herpesvirus 1 strain variation reveals a point mutation of the DNA polymerase strongly associated with neuropathogenic versus nonneuropathogenic disease outbreaks

Equid herpesvirus 1 (EHV-1) can cause a wide spectrum of diseases ranging from inapparent respiratory infection to the induction of abortion and, in extreme cases, neurological disease resulting in paralysis and ultimately death. It has been suggested that distinct strains of EHV-1 that differ in pathogenic capacity circulate in the field. In order to investigate this hypothesis, it was necessary to identify genetic markers that allow subgroups of related strains to be identified. We have determined all of the genetic differences between a neuropathogenic strain (Ab4) and a nonneuropathogenic strain (V592) of EHV-1 and developed PCR/sequencing procedures enabling differentiation of EHV-1 strains circulating in the field. The results indicate the occurrence of several major genetic subgroups of EHV-1 among isolates recovered from outbreaks over the course of 30 years, consistent with the proposal that distinct strains of EHV-1 circulate in the field. Moreover, there is evidence that certain strain groups are geographically restricted, being recovered predominantly from outbreaks occurring in either North America or Europe. Significantly, variation of a single amino acid of the DNA polymerase is strongly associated with neurological versus nonneurological disease outbreaks. Strikingly, this variant amino acid occurs at a highly conserved position for herpesvirus DNA polymerases, suggesting an important functional role.

Analysis of human cytomegalovirus UL144 variability in low-passage clinical isolates in Japan

To explore a possible role for viral genes as determinants of virulence, portions of the UL144 tumor necrosis factor-like receptor gene and the UL55 envelope glycoprotein B gene from 42 patients with congenital human cytomegalovirus (HCMV) infection or other diseases were sequenced. Of the 42 patients, 16 (38%) had UL144 group 1 [group 1A, 15 of 16 (94%); group 1B, 1 of 16 (6%); group 1C, 0 of 16 (0%)], 5 patients (12%) had UL144 group 2, and 21 patients (50%) had UL144 group 3. Although group 1C was not found in Japan strains (0%), it was found in USA strains (22%). Other HCMV polymorphisms should be further evaluated for their potential relevance to neonatal infection, and acquired immunodeficiency syndrome-associated HCMV diseases.

Congenital cytomegalovirus infection: association between virus burden in infancy and hearing loss

OBJECTIVE

To determine the relationship between the virus burden in infancy and hearing loss in congenital CMV infection.

STUDY DESIGN

A cohort of 76 infants with congenital cytomegalovirus (CMV) infection identified by means of newborn virologic screening was monitored for outcome. The amount of infectious CMV was analyzed in urine specimens obtained during early infancy. Peripheral blood (PB) samples obtained during early infancy were available from 75 children and CMV DNA was quantitated with a real-time quantitative polymerase chain reaction.

RESULTS

Infants with clinical abnormalities at birth (symptomatic congenital CMV infection) had higher amounts of CMV in urine (P = .005) and CMV DNA in PB (P = .001) than infants with no symptoms. Eight children with and 4 children without symptoms had hearing loss. Among children without symptoms, those with hearing loss had a significantly greater amount of CMV in urine (P = .03) and PB virus burden (P = .02) during infancy than those with normal hearing. Infants with < 5 x 10(3) pfu/mL of urine CMV and infants with < 1 x 10(4) copies/mL of viral DNA in PB were at a lower risk for hearing loss.

CONCLUSION

In children with asymptomatic congenital CMV infection, hearing loss was associated with increased amounts of urine CMV and PB CMV DNA during early infancy.

Inter- and intra-person cytomegalovirus infection in Malawian families

Sequence polymorphisms in the gN and gO genes of cytomegalovirus (CMV) amplified from mouth rinse and urine samples of 19 Malawian patients with Kaposi's sarcoma (KS) and 58 of their first-degree relatives were investigated. CMV-DNA was amplified from 41 people (53%) from either the gN or gO region in at least one sample, from 14 people (18%) in both domains in at least one sample, and from 13 (17%) in either domain in both samples. Twenty-one (51%) were seropositive for human immunodeficiency virus-1 (HIV). Identical gN sequences were recovered from eight families and non-identical sequences in six, while identical gO sequences were found in three families and non-identical sequences in five. Five people, four of whom were children, each carried multitypic gN sequences or gO sequences. The findings are consistent with CMV spread along intra- and extra-household routes, and with multiple intra-host CMV infection.

Cytomegalovirus (CMV) glycoprotein B genotype and CMV DNA load in the amniotic fluid of infected fetuses

OBJECTIVE

To assess the value of both cytomegalovirus (CMV) DNA quantification in amniotic fluid (AF) and CMV glycoprotein B (gB) genotype as prognostic factors in CMV congenital infection.

METHODS

Quantification of CMV DNA was performed prospectively by real-time PCR and gB genotypes were analysed by gene sequencing analysis in the amniotic fluid of 42 fetuses infected by CMV. These were correlated with clinical data on fetal anomalies and outcome.

RESULTS

The proportion of severely symptomatic fetuses was similar in each gB genotype group. Median CMV DNA load was higher in the group of symptomatic fetuses but this difference was not significant and high and low viral loads were found in both groups.

CONCLUSION

Neither gB genotype nor CMV DNA load in AF correlate with the severity of CMV congenital infection and these markers are unlikely to prove useful for the management of congenital infection.

Genomic variants among human cytomegalovirus (HCMV) clinical isolates: the glycoprotein n (gN) paradigm

Human cytomegalovirus (HCMV) clinical isolates display genetic polymorphisms, which are supposed to be implicated in strain-specific tissue tropism and HCMV-induced immunopathogenesis. One highly variable gene is ORF UL73, encoding for the envelope glycoprotein gN, which displays both a structural and an immunologic role as a component of the high-molecular weight complex gC-II. UL73 showed clustered polymorphisms, which originate four distinct genomic variants, denoted gN-1, gN-2, gN-3, and gN-4. This review reports the main features of gN genotypes and their potential implications on HCMV biologic properties. The clinical impact of gN variants is also discussed. This overview on gN clustered polymorphisms should be useful as a prototype model for a better understanding of the biologic and clinical relevance of HCMV clinical isolates genetic variability.

Genetic polymorphisms among human cytomegalovirus (HCMV) wild-type strains

Human cytomegalovirus (HCMV) clinical isolates display genetic polymorphisms in multiple genes. Some authors have suggested that those polymorphisms may be implicated in HCMV-induced immunopathogenesis, as well as in strain-specific behaviours, such as tissue-tropism and ability to establish persistent or latent infections. This review summarises the features of the main clustered HCMV polymorphic open reading frames and also briefly cites other variable loci within the viral genome. The implications of gene polymorphisms are discussed in terms of potentially advantageous higher fitness obtained by the strain, but also taking into account that the published data are often speculative. The last section of this review summarises and critically analyses the main literature reports about the linkage of strain specific genotypes with clinical manifestations of HCMV disease in different patient populations affected by severe cytomegalovirus infections, namely immunocompromised subjects and congenitally infected newborns.

Phylogenetic analysis of clinical herpes simplex virus type 1 isolates identified three genetic groups and recombinant viruses

Herpes simplex virus type 1 (HSV-1) is a ubiquitous human pathogen which establishes lifelong infections. In the present study, we determined the sequence diversity of the complete genes coding for glycoproteins G (gG), I (gI), and E (gE), comprising 2.3% of the HSV-1 genome and located within the unique short (US) region, for 28 clinical HSV-1 isolates inducing oral lesions, genital lesions, or encephalitis. Laboratory strains F and KOS321 were sequenced in parallel. Phylogenetic analysis, including analysis of laboratory strain 17 (GenBank), revealed that the sequences were separated into three genetic groups. The identification of different genogroups facilitated the detection of recombinant viruses by using specific nucleotide substitutions as recombination markers. Seven of the isolates and strain 17 displayed sequences consistent with intergenic recombination, and at least four isolates were intragenic recombinants. The observed frequency of recombination based on an analysis of a short stretch of the US region suggests that most full-length HSV-1 genomes consist of a mosaic of segments from different genetic groups. Polymorphic tandem repeat regions, consisting of two to eight blocks of 21 nucleotides in the gI gene and seven to eight repeats of 3 nucleotides in the gG gene, were also detected. Laboratory strain KOS321 displayed a frameshift mutation in the gI gene with a subsequent alteration of the deduced intracellular portion of the protein. The presence of polymorphic tandem repeat regions and the different genogroup identities can be used for molecular epidemiology studies and for further detection of recombination in the HSV-1 genome.

Comparison of a duplex quantitative real-time PCR assay and the COBAS Amplicor CMV Monitor test for detection of cytomegalovirus

A duplex quantitative real-time PCR (qPCR) assay was designed to detect both the polymerase gene (pol) and the glycoprotein gene (gB) of cytomegalovirus (CMV). The detection limit of the qPCR was determined to be 1 to 3 copies/reaction and the linear measure interval was 10(3) to 10(8) copies/ml. The qPCR system was compared to the COBAS Amplicor CMV Monitor test (COBAS) by an analysis of 138 plasma samples. Both systems detected CMV in 71 cases and had negative results for 33 samples. In addition, 34 samples were positive by qPCR and negative by the COBAS assay, but in no case was the COBAS result positive and the qPCR result negative. Thus, qPCR detected 48% more positive cases than the COBAS method. For samples with > or = 10(5) copies/ml by qPCR, a saturation effect was seen in the COBAS assay and quantification required dilution. Copy numbers for pol and gB by qPCR generally agreed. However, the reproducibility of qPCR assays and the need for an international standard are discussed. Discrepant copy numbers for pol and gB by qPCR were found for samples from two patients, and sequence analysis revealed that the corresponding CMV strains were mismatched at four nucleotide positions compared with the gB fragment primer sequences. In conclusion, a duplex qPCR assay in a real-time format facilitates quantitative measurements and minimizes the risk of false-negative results.

Mixed Cytomegalovirus Glycoprotein B Genotypes in Immunocompromised Patients

On the basis of sequence variation in the UL55 gene that encodes glycoprotein B (gB), human cytomegalovirus (CMV) can be classified into 4 gB genotypes. The goal of the present study was to determine the distribution of CMV gB genotypes and the effect of gB type on clinical outcomes in a cohort of immunocompromised patients, including both transplant recipients and nonrecipients. The distribution of gB genotypes was as follows: gB1, 28.9% of patients; gB2, 19.6%; gB3, 23.7%; gB4, 2.0%; and mixed infection, 25.8%. In contrast to patients infected with a single gB genotype, patients infected with multiple gB genotypes developed progression to CMV disease, had an increased rate of graft rejection, had higher CMV loads, and were significantly more often infected with other herpesviruses. The presence of multiple gB genotypes, rather than the presence of a single gB genotype, could be a critical factor associated with severe clinical manifestations in immunocompromised patients.

Linkage of human cytomegalovirus glycoprotein gO variant groups identified from worldwide clinical isolates with gN genotypes, implications for disease associations and evidence for N-terminal sites of positive selection

Previously, we identified the glycoprotein gO gene, UL74, as a hypervariable locus in the human cytomegalovirus (HCMV) genome [Virology 293 (2002) 281]. Here, we analyze gO from 50 isolates from congenitally infected newborns, transplant recipients, and HIV/AIDS patients from Italy, Australia, and UK. These are compared to four gO groups described from USA transplantation patients [J. Virol. 76 (2002) 10841]. Phylogenetic analyses identified seven genotypes. Divergence between genotypes was up to 55% and within 3%. Discrete linkage was shown between seven hypervariable gO and gN genotypes, but not with gB. This suggests interactions, while gN and gO are known to form complexes with distinct conserved glycoproteins gM, gH/gL, respectively, both are involved in fusogenic entry and exit. Codon-based maximum likelihood models showed evidence for sites of positive selection. Further analyses of disease relationships should take into account these newly defined gO/gN groups.

Intrauterine cytomegalovirus infection and glycoprotein N (gN) genotypes

BACKGROUND

Human cytomegalovirus (HCMV) clinical isolates display genetic polymorphisms, supposed to be related with strain-specific tissue-tropism and HCMV-induced immunopathogenesis. One recently discovered polymorphic gene is ORF UL73, encoding for the envelope glycoprotein gN. Among HCMV clinical strains, it shows four distinct genomic variants denoted as gN-1, gN-2, gN-3 and gN-4.

OBJECTIVES

Aims of this study were to assess the prevalence of the different gN types in the populations examined and to investigate the possible relationship between genotypes and severity of congenital CMV disease.

STUDY DESIGN

The gN genotyping was carried out by sequencing analysis of the HCMV ORF UL73. Comparisons were made by chi-square test and contingency tables.

RESULTS

All the four gN genotypes can cause congenital infections and the overall distribution was as follows: gN-1, 23.6%; gN-2, 1.1%; gN-3, 12.9%; gN-4, 62.4%. None of them seems to be preferentially associated with vertical transmission or with acute outcome of congenital infection. However, considering the chronic outcome and long-term sequelae, there was a statistically significant (P<0.05) difference between congenitally infected infants with or without adverse chronic outcome.

CONCLUSIONS

HCMV congenital infections, which displayed a prevalence of the gN-1 variants, seem to be associated with favorable chronic outcome.

Different cytomegalovirus glycoprotein B genotype distribution in serum and cerebrospinal fluid specimens determined by a novel multiplex nested PCR

A novel and highly sensitive multiplex nested PCR assay has been developed for the simultaneous glycoprotein B (gB) typing of four gB genotypes of human cytomegalovirus (CMV) directly from clinical specimens. Specifically, a pair of primers to conserved regions of all gB genotypes within the gB gene (gB and gpUL55) was used for primary amplification. A mixture of nested primers to specific and conserved regions of each gB genotype was used for a secondary PCR amplification, yielding amplicons of different sizes for each gB genotype that could easily be differentiated by agarose gel electrophoresis. A total of 40 of 44 serum specimens and 26 of 26 cerebrospinal fluid (CSF) samples, which had previously tested positive for CMV in 66 of 70 AIDS patients with different CMV disease conditions, were gB genotyped by this novel assay. Significant differences in glycoprotein B genotype distribution between serum and CSF specimens were found (P = 0.001). gB genotype 3 (gB3) and gB2 were the most prevalent genotypes in sera (42.5%) and CSF (38.5%), respectively. A different distribution was also observed when only patients with CMV retinitis were studied (P = 0.005), suggesting a gB2 neuron tropism. Neither CMV disease nor any particular clinical manifestation of CMV disease was associated with gB genotypes (P > 0.05). A high incidence of mixed infection with the gB1 and gB3 genotypes (27.5%) was detected in serum specimens, indicating that reinfection and reactivation are common traits in advanced AIDS patients.

Human cytomegalovirus glycoprotein N (gpUL73-gN) genomic variants: identification of a novel subgroup, geographical distribution and evidence of positive selective pressure

Human cytomegalvirus (HCMV) ORF UL73 is a polymorphic locus, encoding the viral glycoprotein gpUL73-gN, a component of the gC-II envelope complex. The previously identified gN genomic variants, denoted gN-1, gN-2, gN-3 and gN-4, were further investigated in this work by analysing a large panel of HCMV clinical isolates collected from all over the world (223 samples). Sequencing and phylogenetic analysis confirmed the existence of the four gN genotypes, but also allowed the identification of a novel subgroup belonging to the gN-3 genotype, which was designated gN-3b. The number of non-synonymous (d(N)) and synonymous (d(S)) nucleotide substitutions and their ratio (d(N)/d(S)) were estimated among the gN genotypes to evaluate the possibility of positive selection. Results showed that the four variants evolved by neutral (random) selection, but that the gN-3 and gN-4 genotypes are maintained by positive selective pressure. The 223 HCMV clinical isolates were subdivided according to their geographical origin, and four main regions of gN prevalence were identified: Europe, China, Australia and Northern America. The gN variants were found to be widespread and represented within the regions analysed without any significant difference, and no new genotype was detected. Finally, for clinical and epidemiological purposes, a rapid and low-cost method for genetic grouping of the HCMV clinical isolates was developed based on the RFLP revealed by SacI, ScaI and SalI digestion of the PCR-amplified UL73 sequence. This technique enabled us to distinguish all four gN genomic variants and also their subtypes.

The genes encoding the gCIII complex of human cytomegalovirus exist in highly diverse combinations in clinical isolates

The UL74 (glycoprotein O [gO])-UL75 (gH)-UL115 (gL) complex of human cytomegalovirus (CMV), known as the gCIII complex, is likely to play an important role in the life cycle of the virus. The gH and gL proteins have been associated with biological activities, such as the induction of virus-neutralizing antibody, cell-virus fusion, and cell-to-cell spread of the virus. The sequences of the two gH gene variants, readily recognizable by restriction endonuclease polymorphism, are well conserved among clinical isolates, but nothing is known about the sequence variability of the gL and gO genes. Sequencing of the full-length gL and gO genes was performed with 22 to 39 clinical isolates, as well as with laboratory strains AD169, Towne, and Toledo, to determine phylogenetically based variants of the genes. The sequence information provided the basis for identifying gL and gO variants by restriction endonuclease polymorphism. The predicted gL amino acid sequences varied less than 2% among the isolates, but the variability of gO among the isolates approached 45%. The variants of the genes coding for gCIII in laboratory strains Towne, AD169, and Toledo were different from those in most clinical isolates. When clinical isolates from different patient populations with various degrees of symptomatic CMV disease were surveyed, the gO1 variant occurred almost exclusively with the gH1 variant. The gL2 variant occurred with a significantly lower frequency in the gH1 variant group. There were no configurations of the gCIII complex that were specifically associated with symptomatic CMV disease or human immunodeficiency virus serologic status. The potential for the gCIII complex to exist in diverse genetic combinations in clinical isolates points to a new aspect that must be considered in studies of the significance of CMV strain variability.

Cytomegalovirus glycoprotein B genotype does not correlate with outcomes in liver transplant patients

BACKGROUND

Based on sequence variation in the UL55 gene that encodes glycoprotein B (gB), human cytomegalovirus (CMV) can be classified into four gB genotypes. Previous studies have suggested there could be an association between CMV gB genotype and clinical outcome in transplant patients.

OBJECTIVES

The goal of this study was to determine the distribution of gB genotypes in a cohort of liver transplant recipients with CMV infection and the effect of gB type on clinical outcomes including CMV disease and rejection.

STUDY DESIGN

DNA was extracted directly from the blood of 58 liver transplant recipients with CMV infection. The gB genotype of CMV was determined using the polymerase chain reaction to amplify a region of UL55, followed by restriction analysis based on HinfI and RsaI digestion. Results were correlated with CMV viral load, symptomatic disease, and development of acute rejection.

RESULTS

The distribution of CMV gB genotypes was: gB1, 15/58 (25.9%); gB2, 16/58 (27.6%); gB3, 21/58 (36.2%); gB4, 2/58 (3.4%) and four patients (6.9%) had mixed infection. No correlation between CMV genotype and peak CMV viral load was observed. Symptomatic CMV disease developed in 25/58 (43.1%) patients and 26/58 (44.8%) had acute rejection. The rate of CMV disease and acute graft rejection in patients infected with the different CMV gB genotypes was not significantly different. However, all four patients with infection with a mixture of CMV gB genotypes developed progression to CMV disease (P=0.030).

CONCLUSIONS

The gB genotype did not correlate with peak CMV viral load and with the development of CMV disease or acute rejection following liver transplantation.

gpUL73 (gN) genomic variants of human cytomegalovirus isolates are clustered into four distinct genotypes

Clinical isolates of human cytomegalovirus (HCMV) show differences in tissue tropism, severity of clinical manifestations and ability to establish persistent or latent infections, characteristics that are thought to be related to genomic variation among strains. This work analysed the genomic variants of a new HCMV polymorphic locus, open reading frame (ORF) UL73. This ORF encodes the envelope glycoprotein gpUL73 (gN), which associates in a high molecular mass complex with its counterpart, gM, and induces a neutralizing antibody response in the host. Detailed sequence analysis of ORF UL73 and its gene product from clinical isolates and laboratory-adapted strains shows that this glycoprotein is highly polymorphic, in the N-terminal region in particular. gpUL73 hypervariability is not randomly distributed, but the identified genomic variants are clearly clustered into four distinct genotypes (gN-1, gN-2, gN-3 and gN-4), which are not associated with the gB subtype.

Antibodies to the major linear neutralizing domains of cytomegalovirus glycoprotein B among natural seropositives and CMV subunit vaccine recipients

The gB protein (gpUL55) of human cytomegalovirus (CMV) contains C-terminal (AD-1) and N-terminal (AD-2) linear immunodominant neutralizing domains. To measure antibodies to these epitopes, a modified protein (delta-gB) lacking heavily glycosylated intervening regions, the transmembrane domain, and the cytoplasmic domain, was expressed in recombinant baculovirus-infected cells. Eighty-six percent of 600 naturally CMV-seropositive individuals and 93% of 121 gB vaccine recipients had antibodies to delta-gB as detected by enzyme-linked immunosorbent assay (ELISA). The antibody level in vaccinees (median optical density [OD] = 1.73) exceeded that in natural seropositives (median OD = 0.94; p < .0001). Eleven percent of 95 natural seropositives and 7% of 120 gB vaccinees lacked A-gB antibodies but had neutralizing activity. Among subjects with delta-gB antibody, there were weak correlations between antibody level and neutralizing titer. These data suggest that antibodies to linear neutralizing gB domains are highly prevalent in naturally-infected individuals and regularly develop in gB vaccinees. However, for some individuals, discontinuous and/or linear epitopes not represented on delta-gB may be more important in the generation of neutralizing responses.

Investigation of CMV disease in immunocompromised patients

Cytomegalovirus (CMV) is a recognised cause of morbidity and mortality in immunocompromised individuals. This review will concentrate on recent advances in the understanding of the complex interplay between the host and parasite and the pathological consequences of perturbation of the host immune system. The classic view of CMV as a slowly replicating virus is challenged by recent in vivo findings suggesting that active replication occurs dynamically in the human host, with a doubling time of approximately one day. In addition, CMV load plays a major role in viral pathogenesis, such that increased CMV replication is a significant risk factor for disease in all immunocompromised groups studied to date. These studies focus attention on understanding the virological and immunological determinants of enhanced viral replication and its pathological consequences.