Intragenic variability of human cytomegalovirus glycoprotein B in clinical strains

A comparative analysis depicting the disease characteristics and phylogenetic signature of human cytomegalovirus infection in Human Immunodeficiency Virus 1 seropositive patients with end-organ retinitis and gastro-enteric diseases

During advanced HIV infection, Human Cytomegalovirus (HCMV) has been proven to produce devitalizing end-organ diseases (EOD). The interactive co-existence of HIV and HCMV has been reported by many researchers and has been suggested to be linked with a more aggressive disease state. This study has been designed to bring forward an assessment of the clinical risk factors capable of defining the conditions of HCMV induced retinitis and gastro-enteric diseases among HIV1 seropositive patients. We also intended to analyse the phylogenetic variation if any, among the infecting virus types inducing the two separate clinical conditions. The patients were arranged in three different groups; (Group 1 with 26 individuals and group 2 and group 3 with 25 individuals each) based on their current status of HIV and HCMV infections. Serum ELISA, qualitative and quantitative detection of HCMV DNA, Real time mRNA expression study, sequencing, and phylogenetic analysis were performed. All statistical analyses and graphs were exercised using relevant software. We found that in HIV patients with HCMV induced end-organ diseases the components of the CXCL9, 10, 11-CXCR3 chemokine pathway is highly expressed with significant differences existing among patients with retinitis and gastrointestinal disease. We found that the gL gene sequences from the retinitis (HR) group clustered almost separately from that of the gastroenteritis (HG) group in the phylogenetic tree. It may be suggested that a form of natural selection pressure is working on the clinical HCMV strains creating a slight divergence in their phylogenetic lineage thereby helping them adapt to the particular tissue microenvironment they are colonizing.

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

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

Human Cytomegalovirus Genomes Sequenced Directly From Clinical Material: Variation, Multiple-Strain Infection, Recombination, and Gene Loss

The genomic characteristics of human cytomegalovirus (HCMV) strains sequenced directly from clinical pathology samples were investigated, focusing on variation, multiple-strain infection, recombination, and gene loss. A total of 207 datasets generated in this and previous studies using target enrichment and high-throughput sequencing were analyzed, in the process enabling the determination of genome sequences for 91 strains. Key findings were that (i) it is important to monitor the quality of sequencing libraries in investigating variation; (ii) many recombinant strains have been transmitted during HCMV evolution, and some have apparently survived for thousands of years without further recombination; (iii) mutants with nonfunctional genes (pseudogenes) have been circulating and recombining for long periods and can cause congenital infection and resulting clinical sequelae; and (iv) intrahost variation in single-strain infections is much less than that in multiple-strain infections. Future population-based studies are likely to continue illuminating the evolution, epidemiology, and pathogenesis of HCMV.

The nucleic acid positive rate and genotype distribution of human cytomegalovirus in human milk banks in China

To determine the status of human cytomegalovirus (HCMV) infection in human milk in China, a total of 510 human milk samples obtained from three provinces, including 211 donor human milk samples from human milk banks and 299 milk samples obtained from the mothers of premature infants, were tested to detect HCMV DNA. Overall, 46.4% of the donated milk samples and 59.2% of the samples obtained from mothers of premature infants were positive for HCMV DNA. The concentration of HCMV DNA was approximately 10³ -10⁴ copies/ml in the HCMV-DNA-positive human milk samples. Based on the nucleotide sequence of a 299- to 305-bp fragment of the glycoprotein B (gB) gene, three HCMV genotypes (gB1, gB2 and gB3) were identified in human milk samples. Mixed infection with genotypes gB1 and gB3 was also found in four milk samples from mothers. Genotype gB1 was the predominant genotype in the HCMV-DNA-positive human milk samples, and it could be subdivided into three lineages. There were also some characteristic nucleotides and amino acids in the three HCMV genotypes, which were helpful for distinguishing the genotypes. This is the first study to clarify the HCMV infection status and genetic characteristics of human milk obtained from banks in China, which will be helpful in preventing postnatal HCMV infections and ensuring the safety of human milk banks.

A Native Human Monoclonal Antibody Targeting HCMV gB (AD-2 Site I)

Hyperimmune globulin (HIG) has shown efficacy against human cytomegalovirus (HCMV) for both transplant and congenital transmission indications. Replicating that activity with a monoclonal antibody (mAb) offers the potential for improved consistency in manufacturing, lower infusion volume, and improved pharmacokinetics, as well as reduced risk of off-target reactivity leading to toxicity. HCMV pathology is linked to its broad cell tropism. The glycoprotein B (gB) envelope protein is important for infections in all cell types. Within gB, the antigenic determinant (AD)-2 Site I is qualitatively more highly-conserved than any other region of the virus. TRL345, a high affinity (Kd = 50 pM) native human mAb to this site, has shown efficacy in neutralizing the infection of fibroblasts, endothelial and epithelial cells, as well as specialized placental cells including trophoblast progenitor cells. It has also been shown to block the infection of placental fragments grown ex vivo, and to reduce syncytial spread in fibroblasts in vitro. Manufacturing and toxicology preparation for filing an IND (investigational new drug) application with the US Food and Drug Administration (FDA) are expected to be completed in mid-2019.

Distribution of cytomegalovirus genotypes among ulcerative colitis patients in Okinawa, Japan

BACKGROUND/AIMS

To determine the prevalence of glycoprotein B (gB), glycoprotein N (gN), and glycoprotein H (gH) genotypes of human cytomegalovirus (HCMV) superimposed on ulcerative colitis (UC) patients in Japan.

METHODS

Four archived stool samples and 7-archived extracted DNA from stool samples of 11 UC patients with positive multiplex polymerase chain reaction (PCR) results for HCMV were used UL55 gene encoding gB, UL73 gene encoding gN, and UL75 gene encoding gH were identified by PCR. Genotypes of gB and glycoprotein N were determined by sequencing.

RESULTS

Among 11 samples, 8 samples were amplified through PCR. gB, gN, and gH genotypes were successfully detected in 3 of 8 (37.5%), 4 of 8 (50%), and 8 of 8 (100%), respectively. The distribution of gB and gN genotypes analyzed through phylogenetic analysis were as follows: gB1 (2/3, 66.7%), gB3 (1/3, 33.3%), gN3a (2/4, 50%), and gN3b (2/4, 50%). Other gB genotypes (gB2 and gB4) and gN genotypes (gN1, gN2, and gN4) were not detected in this study. Out of successfully amplified 8 samples of gH genotype, gH1 and gH2 were distributed in 12.5% and 75% samples, respectively. Only 1 sample revealed mixed infection of gH genotype. The distribution of gH1 and gH2 differed significantly (1:6, P<0.05) in UC patients. The distribution of single gH genotype also revealed significant difference in UC patients who were treated with immunosuppressive drug (P<0.05).

CONCLUSIONS

In this study, gB1, gN3, and gH2 gene were determined as the most frequently observed genotypes in UC patients, which suggest that there might be an association between these genotypes of HCMV and UC.

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.

Seronegative invasive gastro-intestinal cytomegalovirus disease in renal allograft recipients a diagnostic dilemma! - Tissue PCR the saviour?

Seronegative Invasive Gastro-intestinal cytomegalovirus disease in renal allograft recipients Background -CMV as oppurtunistic infection affecting the gastrointerstinal tract is the most common cause for tissue invasive CMV disease occuring in 10-30% of organ transplant recepients. Gastrointerstinal CMV disease can be diagnosed in presence of clinical suspecion along with histopathological findings (CMV inclusions) and presence of mucosal lesion(s) on endoscopic examination with collaborative evidences via molecular technique. Aims-Few cases of CMV infection affecting the gastrointerstinal tract show no evidences of dissemintion despite use of highly sensitive molecular techniques. We encountered 6 cases where in despite strong clinical suspecion of Gastrointerstinal CMV disease there were seronegative and endoscopic negative evidences for CMV, blind tissue biopsy yeilded positive results for CMV disease with excellent improvement with antiviral therapy. Conclusions-Blind biopsy specimen for tissue PCR could serve as saviour in an immunocompromised individiual who has a strong clinical symptomatology for GI-CMV disease in absence of viremia, normal endoscopy and histopathology, so that the early therapeutic interventions could help in excellent patient and graft survival.

Cytomegalovirus glycoprotein B genotypes in Mexican children and women

OBJECTIVE

Cytomegalovirus (CMV) is widely distributed and constitutes the main cause of congenital infections worldwide. CMV transmission during pregnancy represents one of the major impacts of this virus on public health. This study aimed at assessing glycoprotein B (gB) CMV genotypes in Mexican children and pregnant women, since there is limited information regarding CMV genomic diversity in Mexico.

METHODS

We analyzed CMV strains detected in Mexican children (n = 38) and women (n = 38) between 2001 and 2012. A fragment of the gB gene was amplified and sequenced, and genotypes were defined based on prototype sequences.

RESULTS

The gB1 genotype was detected more frequently in children (68.4%) compared to women (31.6%; p = 0.0028), while genotype 2 was more common in women (65.8%) compared to children (26.3%, p = 0.0012). Genotype 3 was uncommon in both groups (5.3 and 2.6%). Nucleotide sequences exhibited a high degree of similarity to prototype strains. However, we identified 17 distinct sequences that resulted in changes in the encoded amino acid sequence in four strains.

CONCLUSIONS

gB1 and gB2 are the most common strains associated with CMV infection in Mexican children and women. In addition, we found that the frequency for each genotype differed amongst them, possibly due to variability in transmission or reactivation dynamics.

A high-affinity native human antibody neutralizes human cytomegalovirus infection of diverse cell types

Human cytomegalovirus (HCMV) is the most common infection causing poor outcomes among transplant recipients. Maternal infection and transplacental transmission are major causes of permanent birth defects. Although no active vaccines to prevent HCMV infection have been approved, passive immunization with HCMV-specific immunoglobulin has shown promise in the treatment of both transplant and congenital indications. Antibodies targeting the viral glycoprotein B (gB) surface protein are known to neutralize HCMV infectivity, with high-affinity binding being a desirable trait, both to compete with low-affinity antibodies that promote the transmission of virus across the placenta and to displace nonneutralizing antibodies binding nearby epitopes. Using a miniaturized screening technology to characterize secreted IgG from single human B lymphocytes, 30 antibodies directed against gB were previously cloned. The most potent clone, TRL345, is described here. Its measured affinity was 1 pM for the highly conserved site I of the AD-2 epitope of gB. Strain-independent neutralization was confirmed for 15 primary HCMV clinical isolates. TRL345 prevented HCMV infection of placental fibroblasts, smooth muscle cells, endothelial cells, and epithelial cells, and it inhibited postinfection HCMV spread in epithelial cells. The potential utility for preventing congenital transmission is supported by the blockage of HCMV infection of placental cell types central to virus transmission to the fetus, including differentiating cytotrophoblasts, trophoblast progenitor cells, and placental fibroblasts. Further, TRL345 was effective at controlling an ex vivo infection of human placental anchoring villi. TRL345 has been utilized on a commercial scale and is a candidate for clinical evaluation.

Genotype distribution, viral load and clinical characteristics of infants with postnatal or congenital cytomegalovirus infection

Background

Congenital cytomegalovirus infection is a leading cause of long-term sequelae. Cytomegalovirus is also frequently transmitted to preterm infants postnatally, but these infections are mostly asymptomatic. A correlation between cytomegalovirus genotypes and clinical manifestations has been reported previously in infants with congenital infection, but not in preterm infants with postnatal infection.

Objectives

The main objective of this study was to investigate cytomegalovirus genotype distribution in postnatal and congenital cytomegalovirus infection and its association with disease severity.

Methods

Infants admitted to the neonatal intensive care unit of the University Medical Center Utrecht, The Netherlands between 2003–2010 and diagnosed with postnatal or congenital cytomegalovirus infection were included. Classification of cytomegalovirus isolates in genotypes was performed upon amplification and sequencing of the cytomegalovirus UL55 (gB) and UL144 genes. Clinical data, cerebral abnormalities, neurodevelopmental outcome and viral load were studied in relation to genotype distribution.

Results

Genotyping results were obtained from 58 preterm infants with postnatal cytomegalovirus infection and 13 infants with congenital cytomegalovirus infection. Postnatal disease was mild in all preterm infants and all had favourable outcome. Infants with congenital infection were significantly more severely affected than infants with postnatal infection. Seventy-seven percent of these infants were symptomatic at birth, 2/13 died and 3/13 developed long-term sequelae (median follow-up 6 (range 2–8) years). The distribution of cytomegalovirus genotypes was comparable for postnatal and congenital infection. UL55 genotype 1 and UL144 genotype 3 were predominant genotypes in both groups.

Conclusions

Distribution of UL55 and UL144 genotypes was similar in asymptomatic postnatal and severe congenital CMV infection suggesting that other factors rather than cytomegalovirus UL55 and UL144 genotype are responsible for the development of severe disease.

Human cytomegalovirus intrahost evolution-a new avenue for understanding and controlling herpesvirus infections

Human cytomegalovirus (HCMV) is exquisitely adapted to the human host, and much research has focused on its evolution over long timescales spanning millennia. Here, we review recent data exploring the evolution of the virus on much shorter timescales, on the order of days or months. We describe the intrahost genetic diversity of the virus isolated from humans, and how this diversity contributes to HCMV spatiotemporal evolution. We propose mechanisms to explain the high levels of intrahost diversity and discuss how this new information may shed light on HCMV infection and pathogenesis.

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.

Development of two potential diagnostic monoclonal antibodies against human cytomegalovirus glycoprotein B

Human cytomegalovirus glycoprotein B (gB) represents a target for diagnosis and treatment in view of the role it plays in virus entry and spread. Nevertheless, to our knowledge, rare detection of a gB antigen has been reported in transplant patients and limited information is available about diagnostic gB monoclonal antibodies (mAbs). Our aim was to develop gB mAbs with diagnostic potential. Hydrophilic gB peptides (ST: amino acids 27-40, SH: amino acids 81-94) of favorable immunogenicity were synthesized and used to immunize BALB/c mice. Two mAbs, named ZJU-FH6 and ZJU-FE6, were generated by the hybridoma technique and limited serial dilution and then characterized by indirect ELISA, Western blotting, immunoprecipitation, and immunohistochemical staining. The mAbs displayed high titers of specific binding affinities for the ST and SH synthetic peptides at an mAb dilution of 1:60,000 and 1:240,000, respectively. Western blotting and immunoprecipitation indicated that these mAbs recognized both denatured and native gB of the Towne and AD169 strains. The mAbs, when used as the primary antibody, showed positive staining in cells infected with both Towne and AD169 strains. The mAbs were then tested on patients submitted to allogeneic hematopoietic stem cell transplantation. The gB antigen positivity rates of the patients tested using ZJU-FH6 and ZJU-FE6 were 62.0 and 63.0%, respectively. The gB antigen showed a significant correlation with the level of pp65 antigen in peripheral blood leukocytes. In conclusion, two potential diagnostic gB mAbs were developed and were shown to be capable of recognizing gB in peripheral blood leukocytes in a reliable manner.

Distribution of UL144, US28 and UL55 genotypes in Polish newborns with congenital cytomegalovirus infections

Human cytomegalovirus (HCMV) is the most common congenital infection. HCMV strains display genetic variability in different regions. Distribution of HCMV genotypes in the population of congenitally infected newborns from Central Poland and viral load in newborns' blood is described and discussed. HCMV isolates were analysed by sequencing at three sites on the genome: the UL144 tumour necrosis factor-alpha (TNFα)-like receptor gene, the US28 beta-chemokine receptor gene and the UL55 envelope glycoprotein B (gB) gene. The newborns' blood was examined for HCMV DNA with a nested (UL144, UL55) or heminested (US28) polymerase chain reaction, and the genotypes were determined by sequence analysis. HCMV DNA was detectable in 25 out of 55 examined newborns born by HCMV-infected mothers (45.5%). The blood viral load in mother-infant pairs was determined. Most of the newborns had identical virus genotype, gB2 (96%), UL144 B1 (88%) and US28 A2 (84%). These genotypes were detected in all newborns with asymptomatic congenital infection. The occurrence of UL144 B1 or US28 A2 genotypes in the babies examined was significant in comparison to other genotypes (p=0.0002 and p=0.040 respectively). There was no association between specific gB subtypes in all patients groups (p=0.463). There was no correlation between HCMV genotypes and the outcome.

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.

Restriction enzyme analysis of the human cytomegalovirus genome in specimens collected from immunodeficient patients in Belém, State of Pará, Brazil

INTRODUCTION: Human cytomegalovirus is an opportunistic betaherpesvirus that causes persistent and serious infections in immunodeficient patients. Recurrent infections occur due to the presence of the virus in a latent state in some cell types. It is possible to examine the virus using molecular methods to aid in the immunological diagnosis and to generate a molecular viral profile in immunodeficient patients. The objective of this study was to characterize cytomegalovirus genotypes and to generate the epidemiological and molecular viral profile in immunodeficient patients. METHODS: A total of 105 samples were collected from immunodeficient patients from the City of Belém, including newborns, hemodialysis patients, transplant recipients and HIV+ patients. An IgG and IgM antibody study was completed using ELISA, and enzymatic analysis by restriction fragment length polymorphism (RFLP) was performed to characterize viral genotypes. RESULTS: It was observed that 100% of the patients had IgG antibodies, 87% of which were IgG+/IgM-, consistent with a prior infection profile, 13% were IgG+/IgM+, suggestive of recent infection. The newborn group had the highest frequency (27%) of the IgG+/IgM+ profile. By RFLP analysis, only one genotype was observed, gB2, which corresponded to the standard AD169 strain. CONCLUSIONS: The presence of IgM antibodies in new borns indicates that HCMV continues to be an important cause of congenital infection. The low observed genotypic diversity could be attributed to the small sample size because newborns were excluded from the RFLP analysis. This study will be continued including samples from newborns to extend the knowledge of the general and molecular epidemiology of HCMV in immunodeficient patients.

HCMV gB genotype and its association with cytokine levels in hematopoietic stem cell transplantation

BACKGROUND

Glycoprotein B (gB) has been implicated in determining the pathogenicity and clinical outcomes of human cytomegalovirus (HCMV) disease.

OBJECTIVE

The purpose of this study was to assess the prevalence of gB genotypes in allogeneic hematopoietic stem cell transplantation (allo-HSCT) and the relationship between it and cytokine levels in saliva and blood samples. The impact of these parameters on patients' survival was also investigated.

METHODS

Samples were obtained from 63 patients receiving an allo-HSCT. HCMV gB genotyping was carried out by multiplex nested PCR. The cytokine levels were assessed using ELISA assay.

RESULTS

A single or mixed genotype infection was detected in the saliva and blood of 36/63 and 52/63 subjects, respectively. Patients with gB2 in their saliva showed lower IL-10 levels in comparison with patients without gB2. Reduced blood levels of IFN-γ and IL-1β were also found in recipients with the HCMV gB4 genotype compared with patients without it. Decreased IL-1β and increased IL-10 blood levels were associated with lower survival. However, HCMV gB genotypes have no impact on patient outcome.

CONCLUSION

Decreased IL-1β and increased IL-10 levels in the blood are associated with lower survival. HCMV genotypes are associated with different cytokine levels in saliva and blood.

High genotypic diversity and a novel variant of human cytomegalovirus revealed by combined UL33/UL55 genotyping with broad-range PCR

The known strains of human cytomegalovirus (HCMV) represent genotypic variants of a single species, and HCMV genotypic variability has been studied in order to reveal correlations between different disease patterns and the presence of certain HCMV genotypes, either as single or as multiple infections. The methods used for the detection of HCMV genotypes have not always been sophisticated enough to achieve complete comprehensiveness, mainly because only one genotype is usually detected in a certain specimen, due to primer specificity and genome copy number. To improve detection of variant HCMV genotypes in mixed infections, we developed PCR assays with degenerate primers targeting two variable HCMV genes, glycoprotein B (gB, UL55) and the G-protein-coupled receptor gene UL33. Primers were designed to bind conserved sites in the genomes of HCMV variants and great ape CMVs. To analyse if samples contained one or more HCMV genotypic variants, PCR assays were supplemented with oligonucleotides containing locked nucleic acids. This broad-range PCR methodology and subsequent sequence analysis detected all gB/UL55 and UL33 genotypic variants known to date in primary clinical specimens, but also revealed that many samples contained genotype mixtures. Importantly, a novel UL33 genotypic variant could be discovered in several specimens, and one HCMV isolate was plaque-purified containing the novel UL33 genotype and a so far undescribed variant of gB.

Human cytomegalovirus glycoprotein genotypes in the genital tract tissue of tubal pregnancy patients

This study investigated human cytomegalovirus (HCMV) glycoprotein genotypes in the genital tract tissue of 125 tubal pregnancy patients. The HCMV glycoprotein-B N-terminus (gBn, 54 - 485 NT), gB endoprotease cleavage site (gBclv, 1284 - 1600 NT) and glycoproteinH (gH, -58 - 213 NT) gene fragments were amplified by nested polymerase chain reaction and sequenced to identify gB and gH genotypes. Of 16 gBn-positive samples, four were gBn1, one was gBn2 and 11 were the gBn3 genotype. Of 13 positive gBclv samples, seven were gBclv1, two were gBclv2 and four were the gBclv3 genotype. Of 20 positive gH samples, 10 were gH1, six were gH2 and four were a combined gH1/gH2 genotype. In 10 of the samples that were positive for the gBn and gBclv genotypes, the gBn and gBclv genotypes were not consistent (four were gBclv1-gBn3). This study showed that: (i) HCMV infection with the gB1 - gB3 glycoprotein genotypes is present in tubal pregnancy; (ii) the gBclv and gBn genotypes are not strictly consistent; and (iii) intragenetic variability within the gB gene due to homologous recombination occurs frequently.

Variability of gB and gH genes of human herpesvirus-6 among clinical specimens

The isolates of human herpesvirus-6 (HHV-6), a betaherpesvirus closely related to human cytomegalovirus (HCMV), are classified as either variants A (HHV-6A) or B (HHV-6B) but their intravariant variability has not been studied extensively so far. The full-length genes of envelope glycoproteins gB and gH from 40 distinct HHV-6-DNA-positive specimens and 11 laboratory strains were amplified using PCR, and their nucleotide sequence determined. Nucleotide divergences were observed at 156 (6.2%) and 98 (4.7%) positions in the case of gB and gH genes respectively. Phylogenetic analysis, including reference strain sequences, confirmed the unambiguous distinction between HHV-6A and HHV-6B for both genes. In the case of HHV-6B isolates, two subgroups of gB gene (designated as gB-B1 and gB-B2) and two subgroups of gH gene (gH-B1 and gH-B2) were identified but the phylogenetic trees of both genes were not fully congruent with each other. The analysis of gB and gH protein sequences showed that 26 and 39 critical amino acid changes respectively permitted the unambiguous distinction between HHV-6A and HHV-6B. Among HHV-6B isolates, gB and gH gene subgroups were characterized by specific amino acid signatures made of six, and two residues respectively. The linkage unbalance between amino acid signatures as well as the distribution of crucial nucleotide changes strongly suggested the occurrence of intravariant recombination within gB gene among HHV-6B isolates. These results indicate that, as in the case of HCMV, homologous recombination may contribute to the genetic variability of HHV-6.

Correlation between infections with different genotypes of human cytomegalovirus and Epstein-Barr virus in subgingival samples and periodontal status of patients

Accumulating evidence indicates that herpesviruses may be putative pathogens in various types of periodontal diseases. The present study was performed to examine infections with different genotypes of human cytomegalovirus (HCMV) and Epstein-Barr virus (EBV) in subgingival samples from a Chinese population and to analyze the correlation with periodontal status. A nested PCR assay was used to identify the presence of HCMV, EBV type 1 (EBV-1), and EBV-2; and the amplicons were further analyzed by restriction fragment length polymorphism analysis. HCMV was detected in 79.0% of 143 chronic periodontitis (CP) patients, 78.5% of 65 gingivitis patients, and 76.3% of 76 periodontally healthy individuals, while EBV was found in 63.6%, 32.3%, and 30.3% of the three groups of subjects, respectively. The HCMV-positive PCR products from all the samples were identified as corresponding to gB genotype I (gB-I) or gB-II. HCMV gB-II (62.9%), EBV-1 (43.4%), and EBV-2 (18.2%) were associated with CP at higher frequencies (P < 0.05), whereas HCMV gB-I was more often observed in gingivitis patients (40.0%) and healthy individuals (40.8%) (P < 0.05). Furthermore, a higher rate of coinfection with HCMV and EBV was shown in CP patients (52.4%), especially dual infections with HCMV gB-II and EBV-1 (30.8%) or HCMV gB-II and EBV-2 (12.6%), compared with the rates of single infections with HCMV or EBV (P < 0.05). Infection with HCMV gB-II, EBV-1, or EBV-2 was correlated with higher rates of bleeding on probing (P < 0.05). In patients infected with HCMV gB-II or both HCMV and EBV, including HCMV gB-II and EBV-1, a deeper probing depth or more serious attachment loss was found (P < 0.05). These findings clearly indicate that HCMV gB-II is the dominant genotype detected in subgingival samples in CP. HCMV gB-II infection and HCMV gB-II coinfection with EBV-1 are closely associated with periodontal tissue inflammation and destruction.

Genetic variability of human cytomegalovirus UL132 gene in strains from infected infants

Human cytomegalovirus (HCMV) displays genetic polymorphisms. HCMV infects a number of organs and cell types, leading to the hypothesis that HCMV disease and tissue tropism may be related to specific sequence variability. A gene in UL/b' of HCMV, UL132 open reading frame (ORF), encodes glycoprotein (gpUL132) which is identified as a low-abundance structural component of HCMV. In this study, the sequence variability of the UL132 gene was studied in 30 clinical strains. The results showed that a large number of nucleotide non-synonymous substitutions occurred in the UL132 ORF, particularly in the 5' half, in comparison to the UL132 of reference strain, Toledo. The UL132 variants of the clinical strains were clustered clearly into three major groups in the phylogenetic tree: G1(10/30), G2(9/30), and G3(11/30). The precise definition of UL132 genotypes and their putative functions would be helpful in a better understanding of the HCMV.

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.

Human cytomegalovirus genetic variability in strains isolated from Japanese children during 1983-2003

The genetic variability of 74 human cytomegalovirus (HCMV) clinical isolates from 60 Japanese infants and children during 1983-2003 was investigated, and the relevance to their clinical course was studied. The patients consisted of 10 asymptomatic congenitally infected babies, 45 infected perinatally or postnatally resulting in HCMV mononucleosis/hepatitis and 5 immunocompromised hosts. The hypervariable region of the HCMV genome, that is the a sequence and UL144 region was analyzed using the polymerase chain reaction (PCR) and unrooted phylogenetic trees. HCMV glycoprotein B (gB) polymorphism was also studied. Unrooted phylogenetic trees of a sequence and UL144 allowed the isolates to be grouped to 5 and 3 clades, respectively. Three gB genotypes were also determined. However, there was no correlation between specific genotypes of these three genes and clinical forms, except for congenital infection which fell into one of three clades of the UL144 gene. In addition, the variability of the three genes had no correlation with each other. This implies that study of a single gene is insufficient for investigating the molecular epidemiology of HCMV. This study provides basic data on the genetic variability of HCMV in an Asian population and should help to determine the strains for vaccine candidates.

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.

Genetic variability of the major histocompatibility complex class I homologue encoded by human cytomegalovirus leads to differential binding to the inhibitory receptor ILT2

Human cytomegalovirus carries a gene, UL18, that is homologous to cellular major histocompatibility complex (MHC) class I genes. Like MHC class I molecules, the protein product of the UL18 gene associates with beta2-microglobulin, and the stability of this complex depends on peptide loading. UL18 protein binds to ILT2 (CD85j), an inhibitory receptor present on B cells, monocytes, dendritic cells, T cells, and NK cells that also recognizes classical and nonclassical MHC molecules. These observations suggest that UL18 may play a role in viral immune evasion, but its real function is unclear. Since this molecule has similarity with polymorphic MHC proteins, we explored whether the UL18 gene varied between virus isolates. We report here that the UL18 gene varies significantly between virus isolates: amino acid substitutions were found in the predicted alpha1, alpha2, and alpha3 domains of the UL18 protein molecule. We also studied the ability of several variant UL18 proteins to bind to the ILT2 receptor. All of the variants tested bound to ILT2, but there were marked differences in the affinity of binding to this receptor. These differences were reflected in functional assays measuring inhibition of the cytotoxic capacity of NK cells via interaction with ILT2. In addition, the variants did not bind other members of the CD85 family. The implications of these data are discussed.

Detection of baboon cytomegalovirus (BaCMV) by PCR using primers directed against the glycoprotein B gene

We have cloned and sequenced the glycoprotein B genes from five strains of BaCMV, isolated from three subspecies of cynocephalus baboons (olive, yellow and chacma). Primers were designed using conserved DNA regions of the gB gene to allow DNA amplification from all strains of BaCMV. These regions differ sufficiently from human CMV that HCMV strains are not amplified, thus allowing differentiation of BaCMV from HCMV. These diagnostic primers were used to test crude nucleic acid extracts from 27 strains of BaCMV and detected 26 of them. Overall, the sensitivity and specificity of this assay are 96.7 and 100%, respectively. BaCMV strains isolated from yellow and olive baboons were very similar and could be discriminated from strains isolated from chacma baboons using a second set of PCR primers. Phylogenetic analysis of the gB genes supported the inferred close relationship of strains isolated from olive and yellow baboons.

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.

Stability of human cytomegalovirus genotypes in persistently infected renal transplant recipients

Although most genes are highly conserved among strains of human cytomegalovirus (HCMV), several are unusually variable. By analyzing the sequence of two variable genes (UL146 and UL74) amplified directly from whole blood DNA extracts, multiple HCMV strains were detected in blood samples from 5/11 virus-infected renal transplant patients. These five patients were seronegative prior to transplantation and their likely acquisition of the virus was via the donated organ; HCMV-positive immunocompetent donors may thus be capable of harboring and transmitting multiple virus genotypes. In sequential samples taken up to 140 days post transplant no mutations in either gene were detected from 9/10 patients, and in the remaining patient a single nucleotide change was detected in UL146, and none in UL74. All sequences grouped into previously defined genotypes, with the detection of multiple members of the UL74 group 5 genotype establishing this previously tentative genotype. Additionally, identical sequences were identified in viruses from different patients, including examples from geographically distinct regions. Thus, although UL146 and UL74 exhibit impressive variation among strains, their sequences are maintained stably within and between infected individuals, suggesting that sequence differences between genotypes may be driven by differing gene function.

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.

Sequence variability of the alpha-chemokine UL146 from clinical strains of human cytomegalovirus

Human cytomegalovirus (HCMV) is a ubiquitous pathogen that infects a variety of cell types in vivo. A region (referred to as UL/b') present in the Toledo strain of HCMV and low passage clinical isolates contains 22 additional genes, which are absent in the highly passaged laboratory strain AD169. One of these genes, UL146, encodes an alpha-chemokine. PCR amplification and sequencing of this gene from serial samples obtained from transplant recipients and samples from infants with suspected congenital HCMV infection, revealed that UL146 is a hypervariable gene in vivo. However, genetic changes were highly conserved in individuals and in renal transplant recipients multiple genotypes of UL146 were present. The majority of strains characterized maintained the conserved ELRCXC motif present in the Toledo strain of HCMV. These results provide further evidence that AD169 does not represent the authentic virus in vivo and although Towne and Toledo are more representative, major genetic differences still exist. Mixed populations of HCMV strains occur in vivo so cloning of these strains is essential if an authentic genotype is to be defined.

Assessment of human cytomegalovirus specific T cell immunity in human immunodeficiency virus infected patients in different disease stages following HAART and in long-term non-progressors

T cell immunity to human cytomegalovirus (HCMV) was assessed in HAART-treated HIV-1 infected patients (9 asymptomatic, CDC group A; and 22 symptomatic, CDC group B), and in eight HIV-1 long term non-progressors. Patients were either prospectively or cross-sectionally examined for CD4(+) T cell counts, HIV RNA load, HCMV leukoDNAemia, HCMV DNA in urine, lymphoproliferative response (LPR) to HCMV and phytohemagglutinin (PHA), and cytokine secretion (IFN-gamma and IL-4) by HCMV-stimulated peripheral blood mononuclear cell (PBMC) cultures. No patient either progressed to clinical AIDS or developed HCMV active infection during the study period. Twenty-nine patients responded to HAART, though 12 patients failed to recover the LPR to HCMV over the study period (three from CDC group A and nine from CDC group B). In contrast to healthy control individuals, most patients displaying positive LPRs LPRs to HCMV had unstable responses. Sustained LPRs to HCMV were significantly associated with high pre-HAART nadir CD4(+) T cell counts. Long-term suppression of HIV viremia correlated with recovery of LPR to HCMV. Sequential PBMC cultures from most patients secreted IFN-gamma (but not IL-4) at normal levels upon HCMV stimulation, irrespective of the pre-HAART nadir CD4(+) T cell counts and CDC group to which patients belonged. Failure to reconstitute IFN-gamma response was associated with very low pre-HAART nadir CD4(+) T cell counts. Control of HCMV infection in the cohort was associated with either recovery or maintenance of IFN-gamma response rather than with reconstitution of LPR to HCMV. A LPR to HCMV was absent in three out of eight long term non-progressors; contrarily, all patients showed preserved IFN-gamma responses.

Specific detection and identification of herpes B virus by a PCR-microplate hybridization assay

Herpes B virus DNA was specifically amplified by PCR, targeting the regions that did not cross-react with herpes simplex virus (HSV). The amplified products, which were shown to be highly genetic polymorphisms among herpes B virus isolates, were identified by microplate hybridization with probes generated by PCR. The products immobilized in microplate wells were hybridized with the biotin-labeled probes derived from the SMHV strain of herpes B virus. The amplified products derived from the SMHV and E2490 strains of herpes B virus were identified by microplate hybridization. PCR products amplified from the trigeminal ganglia of seropositive cynomolgus macaques were identified as herpes B virus DNA. The utility of the PCR-microplate hybridization assay for genetic detection and identification of the polymorphic region of herpes B virus was determined.

Determination of human cytomegalovirus genetic diversity in different patient populations in Costa Rica

Seroprevalence of HCMV in Costa Rica is greater than 95% in adults; primary infections occur early in life and is the most frequent congenital infection in newborns. The objectives of this study were to determine the genetic variability and genotypes of HCMV gB gene in Costa Rica. Samples were collected from alcoholics, pregnant women, blood donors, AIDS patients, hematology-oncology (HO) children and HCMV isolates from neonates with cytomegalic inclusion disease. A semi-nested PCR system was used to obtain a product of 293-296 bp of the gB gene to be analyzed by Single Stranded Conformational Polymorphism (SSCP) and sequencing to determine the genetic polymorphic pattern and genotypes, respectively. AIDS patients showed the highest polymorphic diversity with 14 different patterns while fifty-six percent of HO children samples showed the same polymorphic pattern, suggesting in this group a possible nosocomial infection. In neonates three genotypes (gB1, gB2 and gB3), were determined while AIDS patients and blood donors only showed one (gB2). Of all samples analyzed only genotypes gB1, 2 and 3 were determined, genotype gB2 was the most frequent (73%) and mixed infections were not detected. The results of the study indicate that SSCP could be an important tool to detect HCMV intra-hospital infections and suggests a need to include additional study populations to better determine the genotype diversity and prevalence.

Coding potential of laboratory and clinical strains of human cytomegalovirus

Six strains of human cytomegalovirus have been sequenced, including two laboratory strains (AD169 and Towne) that have been extensively passaged in fibroblasts and four clinical isolates that have been passaged to a limited extent in the laboratory (Toledo, FIX, PH, and TR). All of the sequenced viral genomes have been cloned as infectious bacterial artificial chromosomes. A total of 252 ORFs with the potential to encode proteins have been identified that are conserved in all four clinical isolates of the virus. Multiple sequence alignments revealed substantial variation in the amino acid sequences encoded by many of the conserved ORFs.

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.

Association of glycoprotein B and immediate early-1 genotypes with human leukocyte antigen alleles in renal transplant recipients with cytomegalovirus infection

BACKGROUND

Numerous risk factors for cytomegalovirus (CMV) infection or disease, or both, such as serostatus of donor and recipient, immunosuppressive regimen, or intensity of viral load, have been identified in renal transplant recipients. Additional parameters may be involved, notably, genetic variability of both host and virus, which could modulate the efficacy of the immune response.

METHODS

Active CMV infection was analyzed retrospectively in 634 renal transplant recipients, according to human leukocyte antigen (HLA)-A, HLA-B, and HLA-DR alleles; CMV serostatus; presentation of the disease; and variations in the coding sequences of glycoprotein (g) B and IE1 proteins.

RESULTS

Active infection occurred in 141 of 634 patients: seropositivity of the donor and the recipient were identified as risk factors. Patients carrying the HLA-A11, HLA-A32, or HLA-DR11 allele developed active infection more frequently, whereas none of the patients with the HLA-B16 or HLA-B55 allele was actively infected. Significant independent associations between some genotypes and particular HLA alleles were observed: gB1 was more frequent in the HLA-A24 or HLA-B7 context and underrepresented in patients with HLA-DR11; gB2 was more frequent in HLA-A32 or HLA-DR11 carriers; and an increased frequency of gB3 was observed in the HLA-A29 context. Considering the IE1-2 genotype, increased frequency was noted for HLA-A3 carriers, whereas this type was underrepresented for patients with the HLA-DR11 allele.

CONCLUSION

Data strongly suggest that differential presentation of polymorphic gB or IE peptides by HLA molecules or differential recognition by host CD8+ and CD4+ T lymphocytes, or both, should modulate immunologic response and then CMV pathogenesis in renal transplant patients.

Binding characteristics determine the neutralizing potential of antibody fragments specific for antigenic domain 2 on glycoprotein B of human cytomegalovirus

Site I of antigenic domain 2 (AD-2) on human cytomegalovirus glycoprotein B (gB) is poorly immunogenic in both man and mouse and knowledge about antibody repertoires reactive with this epitope is thus limited. Here we have characterized a phage display-derived repertoire of antibody fragments specific for this epitope in terms of antigen recognition, fine-specificity, and virus-neutralizing capacity. Our results show that the functional properties within a closely related repertoire may differ widely and that the effectiveness of the members of the repertoire to neutralize the virus is determined by the fine-specificity and kinetics of the interaction with the antigen. The half-life of the interaction between monomeric antibody fragments and gB seems to be particularly critical for the neutralizing capacity. We also demonstrate that sequence variation within gB allows virus variants to escape at least a part of the AD-2-specific neutralizing antibody repertoire, apparently without preventing antibody binding to the epitope.

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.

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.

Human cytomegalovirus a sequence and UL144 variability in strains from infected children

Human cytomegalovirus (HCMV) displays genetic polymorphisms. This variability may contribute to strain-specific tissue tropism and disease expression in HCMV-infected humans. To determine strain variability in a sequence and UL144 gene regions, 51 low-passage isolates from 44 HCMV-infected children were studied. Isolates were obtained from 28 healthy children attending child care centers in Iowa and from 16 congenitally infected infants born in Texas. Isolates demonstrated substantial nucleotide variation in each gene region. Phylogenetic analysis of a sequence variability allowed 39 isolates to be grouped into six clades. The largest clade contained 16 isolates with > or = 95% nucleotide homology. Forty-eight of the 49 HCMV isolates yielding UL144 amplicons was grouped according to the clades described a few years ago [Lurain et al. (1999) Journal of Virology 73:10040-10050]. No linkage was observed among a sequence, UL144, and glycoprotein B (gB; UL55) polymorphisms. Four Texas and 11 Iowa isolates displayed > or = 95% sequence homology for a sequence and UL144 regions and possessed identical gB genotypes. No relationship between UL144 polymorphisms and outcome of congenital HCMV infection was observed. These data indicate that HCMV strains circulating among young children have UL144 polymorphisms similar to those of HCMV strains excreted by immunocompromised adults. Identification of conserved nucleotide sequences among Iowa and Texas children suggests genetic stability and biologic importance of these gene regions.