Identification of human cytomegalovirus variants by analysis of single strand conformation polymorphism and DNA sequencing of the envelope glycoprotein B gene region-distribution frequency in liver transplant recipients

Prevention of human milk-acquired cytomegalovirus infection in very-low-birth-weight infants

BACKGROUND

The aim of the study was to determine the rate of cytomegalovirus virolactia in the human milk (HM) of mothers of VLBW infants, compare the CMV infection rates and the changes in CMV DNA viral load and nutrient profile among different HM preparation methods.

METHODS

A prospective randomized controlled study was performed in infants with gestational age < 32 weeks or birth-weight < 1500 g admitted to neonatal intensive care unit of Asan Medical Center and Haeundae Paik Hospital who were given mother's own milk. Enrolled infants were randomized into three groups according to the HM preparation methods: freezing-thawing (FT), FT + low-temperature Holder pasteurization (FT + LP), and FT + high-temperature short-term pasteurization (FT + HP). Urine CMV culture and PCR were obtained at birth and at 4, 8, and 12 weeks. HM CMV culture and PCR were obtained at birth and at 3, 6, 9, and 12 weeks. Changes in macronutrients in HM was obtained at 4 ~ 6 weeks.

RESULTS

Of 564 infants, 217 mothers (38.5%) produced CMV PCR positive milk. After exclusion, a total of 125 infants were randomized into the FT (n = 41), FT + LP (n = 42), and FT + HP (n = 42) groups, whose rate of HM-acquired CMV infection was 4.9% (n = 2), 9.5% (n = 4), and 2.4% (n = 1), respectively. Out of seven CMV infected infants, two infants fed with FT + LP HM developed CMV infection- associated symptoms. Ages at diagnoses were earlier (28.5 days after birth) and at younger post conceptional age (< 32 weeks) in comparison to infants with asymptomatic CMV infection. CMV DNA viral load significantly decreased after pasturizations, especially in FT + HP group.

CONCLUSIONS

HM-acquired symptomatic CMV infection rate is low and its impact on clinical course was not serious in our VLBW infants. However, evidences showing poor neurodevelopmental outcome in later life, we need to generate a guideline to protect VLBW infant form HM transmitted CMV infection. Based on our small sized study, we did not find any superiority in pasteurizing HM with frequently used LP in comparison to frozen or HP HM. More research is needed to determine the method and duration of pasteurization to reduce the HM-acquired CMV infection.

Comparison of conventional, immunological and molecular techniques for the diagnosis of symptomatic congenital human cytomegalovirus infection in neonates and infants

PURPOSE

Human cytomegalovirus (HCMV) is the commonest pathogen causing congenital infection globally. The diagnosis of congenital infection is based either on viral isolation (in cell culture) or demonstration of HCMV DNA from the urine. Saliva is also being used as an alternative sample to urine for the same. The objective of this study was to compare the following assays-polymerase chain reaction (PCR) from urine, saliva and blood, serology (anti-HCMV IgM) and antigen detection (HCMV pp65 antigenaemia) for the diagnosis of congenital HCMV infection.

MATERIALS AND METHODS

Urine and blood samples were collected from 31 infants (median age: 13 weeks) with suspected HCMV infection. For 18 infants, additional saliva samples were collected and all the above assays were compared.

RESULTS

PCR for HCMV DNA from urine and anti-HCMV IgM were performed for all 31 infants. Of these, 22 (70.9%) were positive for both assays. In 18 (of the 22) infants positive by both assays, PCR for HCMV DNA from saliva was positive in all 18 (100%), PCR from blood in 7/18 (38.8%) and HCMV pp65 antigenaemia only in 1/18 (5.5%) of the infants.

CONCLUSION

Detection of HCMV DNA in urine combined with anti-HCMV IgM are suitable assays to diagnose HCMV infection in infants. Both PCR from the blood and HCMV pp65 antigenaemia lack sensitivity in infants. Salivary PCR combines convenience with high sensitivity and can substitute PCR from urine, especially in the outpatient and field settings. To the best of our knowledge, this is the first study from India to evaluate salivary PCR for the diagnosis of congenital HCMV infection.

Diagnostic consequences of cytomegalovirus glycoprotein B polymorphisms

Failure of a cytomegalovirus (CMV) real-time PCR assay targeting glycoprotein B (gB) was investigated. A multiplex assay targeting gB and immediate-early 2 (IE2) genes showed discordant results (gB negative and IE positive or a >10-fold-higher viral load with IE primers) in saliva from 14.6% of CMV-infected newborns. Sequencing revealed 3 patterns of gB variations.

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.

Congenital cytomegalovirus infection in a highly seropositive semi-urban population in India

To determine the incidence and natural history of congenital cytomegalovirus (CMV) infection in a population of women with near universal serologic reactivity for CMV, a prospective study of 423 women attending the antenatal clinic of the Comprehensive Rural Health Center in northern India was conducted. All 9 (2.1%) CMV positive infants were born to mothers who were CMV seropositive at the first antenatal visit. One child had hepatosplenomegaly at birth and another child had mild unilateral hearing loss at 4 months of age.

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.

Relationship between human cytomegalovirus glycoprotein B genotype and serum alanine aminotransferase elevation in infants

The glycoprotein B (gB) region of the human cytomegalovirus (HCMV) is a major envelope glycoprotein that is a principal target of neutralizing antibodies and is known to stimulate the immune response of cytotoxic T lymphocytes. HCMV is currently classified into four genotypes on the basis of the nucleotide sequence of the gB region. The presence of HCMV in patients under 3 years of age was determined by subjecting urine samples taken from the patients to polymerase chain reaction (PCR) analysis. Analysis by direct sequencing of the gB region was carried out in 90 cases. These cases were grouped into the gB genotype 1 and gB genotype 3. Of 28 cases with a peak serum alanine aminotransferase (ALT) level(> or =100 IU/l), the duration of observed serum ALT elevation in the gB genotype 1 patients (166.7+/-126.7 days [mean+/-S.D.] [19 cases]) was significantly longer than that in the gB genotype 3 patients (39.7+/-31.7 days [9 cases]) (p<0.01). In the 54 cases with a serum ALT level(> or =50 IU/l), similar tendency was seen (p<0.05). These findings suggest that when serum ALT elevation is confirmed in young children infected with HCMV, analysis of the gB region is helpful for prediction of the duration of serum ALT elevation in the early stage of infection.

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.

Genotyping of human cytomegalovirus using non-radioactive single-strand conformation polymorphism (SSCP) analysis

Genetic variation in the glycoprotein B (gB) gene may play a role in human cytomegaloviruses (HCMVs) pathogenesis. Using restriction analysis of the gB gene product (PCR-RFLP), amplified by the nested polymerase chain reaction, the HCMV strains can be compared and classified into at least four HCMV groups. PCR single-strand conformation polymorphism (PCR-SSCP) is one of the techniques used to identify a mutant sequence or a polymorphism in a known gene. SSCP analysis has the advantage over RFLP analysis on detection of DNA polymorphisms and point mutations at a variety of positions in DNA fragments. However, the original SSCP protocols using the incorporation of radioactive label and polyacrylamide gel electrophoresis for detection are labour intensive and time-consuming. A simplified SSCP protocol is described to identify HCMV strains and the gB genotype, allowing the detection of sequence variations not residing in the endonuclease recognition sites.

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.