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.

Characterization of human cytomegalovirus strains by analysis of short tandem repeat polymorphisms

Human cytomegalovirus (HCMV) strains display genetic polymorphisms, and these polymorphisms can be analyzed to study viral transmission and pathogenesis. Recently, short tandem repeat (STR) length polymorphisms have been identified in the HCMV genome. We assessed the utility of STRs in characterizing HCMV strains and found that a multiplexed PCR assay using primers based upon these STRs accurately maps HCMV strains. Using primers for 10 microsatellite regions, the STR profiles of 44 wild-type and 2 laboratory strains of HCMV were characterized. The results of STR analysis were compared with those for strain characterization using nucleotide sequencing and restriction fragment length polymorphism analysis. In each instance, STR analysis accurately and specifically identified strains that were indistinguishable or distinct by conventional molecular analysis. Analysis of short tandem repeats also detected polymorphisms that supported simultaneous excretion of two HCMV strains. These results indicate that STR analysis allows rapid, precise molecular characterization of HCMV strains.

Intrauterine cytomegalovirus infection and glycoprotein B genotypes

Cytomegalovirus (CMV) strains display polymorphisms for the gene encoding glycoprotein B (gB; gpUL55). Recent data suggest that the gB genotype may influence the outcome of acquired CMV infections. To determine whether the gB genotype also contributes to the outcome of intrauterine infection, CMV strains were studied from 56 infants with culture-confirmed intrauterine CMV infections who were born in Iowa or Texas. CMV gB genotypes were compared with the neonatal clinical features and neurodevelopmental outcomes. Fifty-three strains (95%) could be assigned a gB genotype. The overall distribution of genotypes was as follows: type 1, 50%; type 2, 18%; type 3, 23%; and type 4, 4%. Strains with the gB 3 genotype were more common among the Iowa infants (P=.082). The gB 3 genotype was more common among infants with asymptomatic infections (P=.004), but geographic location and ascertainment biases may have accounted for these differences. The gB genotypes did not correlate with the neurodevelopmental outcome of intrauterine infection.

Cytomegalovirus transmission in child care homes

BACKGROUND

Children attending child care centers have high rates of cytomegalovirus (CMV) excretion. Women exposed to such children have an increased risk of acquiring CMV infection, and primary infection places the offspring of such women at risk of congenital CMV infection. We studied family child care homes to determine if this child care alternative might represent a safe haven from CMV.

METHODS

One hundred thirty-two women providing care in their homes were studied using a latex agglutination method to determine the rate of CMV seropositivity at baseline. Women who were seronegative for CMV were then sampled prospectively at 6-month intervals between March 1991 and August 1994 to determine the annual rate of CMV acquisition. A point prevalence of CMV excretion in family homes was determined by sampling 106 children from 25 randomly selected homes. Cytomegalovirus isolates were compared by molecular analysis using polymerase chain reaction-based methods to identify transmission.

RESULTS

At baseline, 57.6% of the 132 providers were seropositive for CMV. Seropositive providers were more likely to be caring for toddlers (aged 1-2 years) (67% vs 46%; P=.02) and had worked in child care somewhat longer (median of 28.5 vs 21.5 months; P=.11). Using stepwise logistic regression, the strongest predictors of seropositivity at baseline were caring for children aged 1 to 2 years (odds ratio [OR] =2.37; P=.02) and number of months as a child care provider (OR= 1.17 for an increase of 24 months as provider; P=.08). Six or more years as a provider was highly associated with seropositivity (OR=3.27; P=.02). During follow-up, 5 of 51 seronegative providers seroconverted, yielding an annual infection rate of 6.8%. The point prevalence survey of children from the 25 homes (14 had seropositive providers) identified 8 CMV-excreting children. Three children in 1 home had indistinguishable isolates by polymerase chain reaction mapping. The provider seroconverted and excreted an isolate with a molecular profile indistinguishable from that of the children.

CONCLUSIONS

The prevalence of CMV excretion is low among children attending child care homes (8% vs 15% in prior studies of child care centers; P=.07), and only 1 (20%) in 5 of the homes had CMV-excreting children. However, the overall CMV seroconversion rate of home child care providers was comparable to the rate observed among providers in child care centers. Families who use family home child care as an alternative to large child care centers are exposed to a low and unpredictable risk of CMV infection.

Epidemiology of congenital cytomegalovirus infection: maternal risk factors and molecular analysis of cytomegalovirus strains

To determine factors that influence the occurrence of congenital cytomegalovirus (CMV) infection, the authors surveyed prospectively 8,254 infants born in eastern Iowa between October 1989 and June 1994. The authors conducted a case-control study to identify maternal risk factors, matching each CMV-infected infant with three uninfected infants according to hospital and date of birth. CMV strains were compared by using the polymerase chain reaction (PCR) to identify common sources of infection. Of the 7,229 infants cultured successfully for CMV, 35 (0.48%) were congenitally infected. Mothers of CMV-infected infants were more likely to be single (odds ratio (OR) = 3.05, p = 0.016), to work in sales (OR = 4.93, p = 0.008), or to be students (OR = 5.01, p = 0.017). Conversely, women who worked in health-care professions were less likely to have a congenitally infected infant (OR = 0.14, p = 0.049). PCR analysis indicated 27 distinct strains of CMV, but two groups of infants (two infants per group) excreted strains with indistinguishable molecular patterns. One of these pairs of infants had older siblings who attended the same child-care center during their mothers' pregnancies. The authors concluded that demographic and occupational factors influenced the risk of giving birth to an infant with congenital CMV infection. Many distinct CMV strains were identified, suggesting that major point source outbreaks had not occurred. Nonetheless, point source acquisition of CMV from child-care environments did account for some cases of congenital CMV infection in eastern Iowa.

Cytomegalovirus infection in newborns and their family members: polymerase chain reaction analysis of isolates

Polymerase chain reaction (PCR) analysis with primers for the pp65, a-sequence, glycoprotein B, and major immediate early genes of human cytomegalovirus (CMV) was used to study five congenitally-infected infants and their CMV-infected family members. Family members excreting CMV included three mothers and two siblings. The PCR results indicated that the CMV strain excreted by each infant was indistinguishable from that excreted by the corresponding family member. By contrast, the molecular profiles of the CMV strains were distinct between families, indicating that the PCR algorithm described in this study is a useful method for analyzing CMV strains.

Cytomegalovirus reinfection in young children

OBJECTIVE

To determine the frequency of reinfection with new cytomegalovirus (CMV) strains in children in group child-care environments.

METHODS

Ninety-two CMV strains isolated serially from children attending child care centers were analyzed. Strains were obtained from 1986 to 1994, from 37 children attending one of six centers in the area of Cedar Rapids and Iowa City, Iowa. The CMV isolates were analyzed by a polymerase chain reaction-based algorithm using primers for the a-sequence, glycoprotein B, and major immediate early (MIE) genes of human CMV. The a-sequence polymerase chain reaction products were compared on the basis of size, and products derived from glycoprotein B and MIE genes were compared according to restriction fragment length polymorphisms.

RESULTS

Children were between 8 months and 5 years 7 months of age at the time of CMV isolation. The number of isolates ranged from 2 to 6 per child, and the intervals between the first and last CMV isolation ranged from 11 weeks to more than 3 years. At least 7 (19%) of the 37 children had evidence of infection with more than one CMV strain. In six of these children, reinfection with distinct strains was confirmed by analysis of the MIE gene products of sequential CMV strains.

CONCLUSIONS

Children who attend child care centers, like adults who are immunosuppressed or have multiple sexual partners, are at risk of being reinfected with distinct CMV strains.