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B J Cohen

Publications and source records attributed to B J Cohen.

At least 19 recordsLinked to original sources
PubMed2006

Genetic variants of parvovirus B19 identified in the United Kingdom: implications for diagnostic testing.

BACKGROUND: Discrepant results in diagnostic parvovirus B19 PCR assays have been observed with strains showing nucleotide sequence variation. OBJECTIVES AND STUDY DESIGN: To perform phylogenetic analysis on two parvovirus B19 strains that gave discrepant PCR results. RESULTS: One strain was found to be genotype 2; the second strain was genotype 3. CONCLUSIONS: Parvovirus B19 genotypes 2 and 3 strains were identified in diagnostic samples of UK origin following the investigation of discrepant PCR results. More structured investigations are needed to estimate the prevalence of these variants. In the meantime, diagnostic PCR results should be interpreted cautiously when they are at variance with serological testing. Manufacturers of PCR kits for the detection of B19 sequences will need to consider re-designing their primers.

Adult↗
PubMed2005

Measles immunity testing: comparison of two measles IgG ELISAs with plaque reduction neutralisation assay.

Two commercial IgG ELISAs, one based on recombinant nucleocapsid antigen and one based on cell culture grown native virus antigens, were evaluated for measles immunity testing by comparison with plaque reduction neutralisation test (PRNT). Qualitative results of the two ELISAs showed 92% agreement with those of PRNT. The sensitivity of the two ELISAs was 89.6%. False negative ELISA results were obtained in 10% of sera, mainly sera containing low levels of neutralising antibody. The specificity of both ELISAs was 100%. Measles IgG ELISAs perform adequately for immunity testing, correctly identifying seronegative individuals for vaccination.

Antibodies, Viral↗
PubMed2003

Validation of a modified commercial assay for the detection of rubella-specific IgG in oral fluid for use in population studies.

Matching serum and oral fluid (saliva) samples were collected from 369 subjects in Tunisia in 2002, from a city in the north and a rural district in the south. Rubella-specific IgG was detected in sera by commercial ELISA (Dade Behring) and in matching oral fluids by two methods, a previously described IgG-capture ELISA (GACELISA) [J. Clin. Microbiol. 37 (1999) 391] and the Dade Behring ELISA with the assay protocol modified for use with oral fluids. Total IgG concentration of oral fluids was also measured. Rubella-specific IgG was detected in 289 (78.3%) sera overall. Differences in the age distribution of the study population in the north and south led to a higher prevalence being found in the north (86.2%) than in the south (71.8%). This difference was reflected in the oral fluid rubella-specific IgG results. With GACELISA, rubella-specific IgG was detected in 79.4% of oral fluids from the north and 69.7% from the south and with the modified Dade Behring assay, in 81.4% of oral fluids from the north and in 64.9% from the south. The sensitivity and specificity of GACELISA in comparison to results from the matching sera were 92.4 and 93.2%, respectively. The sensitivity and specificity of the modified Dade Behring ELISA were 89.8 and 92.0%, respectively. Total IgG concentration in oral fluid showed a weak correlation (r=0.19) with the modified Dade Behring results and with samples where total IgG was >7.5 mg/l, the sensitivity and specificity were 94.4 and 90.0%, respectively. Twenty-nine oral fluids, which gave false negative rubella-specific IgG results with the modified Dade Behring ELISA, had a lower mean total IgG concentration than 256 oral fluids which gave concordant positive results (7.0mg/l versus 15.8 mg/l, P<0.001). The study validated the modified Dade Behring ELISA, providing an alternative to the GACELISA for assessing levels of rubella immunity for population studies using oral fluid samples.

Adolescent↗
PubMed2003

Use of RT-PCR on oral fluid samples to assist the identification of measles cases during an outbreak.

This study investigated the occurrence of mild modified measles cases during an outbreak in Niterói, RJ, Brazil by using RT-PCR on oral fluid samples. From August to December 1997 a total of 76 patients with rash were seen at the study sites. Confirmed diagnosis by serology was achieved in 47 cases: measles (39.5%), rubella (13.2%), HHV-6 (3.9%), human parvovirus B19 (3.9%), dengue fever (3%). For 19 of the 29 patients without a conclusive diagnosis paired serum and saliva samples were available for further tests. In four of them, measles virus RNA was detected by RT-PCR in saliva samples in the absence of specific IgM in serum samples. Vaccination histories obtained from three of the RT-PCR positive cases showed that individuals previously immunized can still be infected and contribute to the circulation of measles virus. This study demonstrated the usefulness of RT-PCR on non-invasive clinical samples for the investigation of measles cases.

Adolescent↗
PubMed2003

Detection of low-avidity immunoglobulin G in oral fluid samples: new approach for rubella diagnosis and surveillance.

Low-avidity rubella immunoglobulin G (IgG) was detected in oral fluid samples from 30 of 32 rubella IgM-positive patients (sensitivity, 94%) and from 4 of 34 IgM-negative patients (specificity, 88%). Measuring IgG avidity in oral fluid samples could improve the reliability of rubella surveillance when the incidence of the disease and the positive predictive value of IgM tests are low.

Antibodies, Viral↗
PubMed2002

Seroprevalence of parvovirus B19 in urban Chilean children and young adults, 1990 and 1996.

An immunofluorescence test for detecting parvovirus B19 IgG was developed by infecting insect cells with recombinant baculovirus expressing the capsid protein VPI. The test was used to study the prevalence of antibodies in 725 healthy children and young adults living in Santiago, Chile. In total, 248 sera were taken in 1990 and 477 in 1996. The seroprevalence was low in children less than 5 years old (3% in 1990 and 21% in 1996). It rose during school age to a prevalence around 50%, reaching 60% in young adults. No differences were found between genders. There was a statistically significant higher seroprevalence in the low socioeconomic status group in 1990 samples, but this was not observed in 1996. The higher prevalence observed in children less than 5 years of age in 1996 compared with 1990 could be explained by the occurrence of intervening epidemics of parvovirus B19 infection.

Adolescent↗
PubMed2001

Measles virus strains circulating in Ethiopia in 1998-1999: molecular characterisation using oral fluid samples and identification of a new genotype.

A measles outbreak in December 1998 in Bedelle (vaccine coverage <40%) and two sporadic cases in Addis Ababa, Ethiopia, were investigated. Paired serum and oral fluid samples were collected 2-8 days after the onset of symptoms. A total of 53 of 55 outbreak cases and both sporadic cases were positive for serum measles virus-specific IgM. Oral fluid measles-specific IgM was positive in 71% of cases collected up to 5 days after onset and in 90% collected at 6-8 days. By contrast, 100% of oral fluid samples were positive for measles virus RNA by RT-PCR, suggesting that early collection of samples favoured the detection of measles virus RNA by RT-PCR. The measles virus strain in the outbreak was identified as genotype D4. One strain from a sporadic case was also genotype D4; the strain from the other sporadic case was assigned to clade D but was distinct. The degree of divergence from recognised clade D strains suggested that, together with three strains from the United Kingdom, it represents an additional genotype of clade D (GenBank accession numbers AF280800-280807).

Adolescent↗
PubMed2001

Efficient isolation of mumps virus from a community outbreak using the marmoset lymphoblastoid cell line B95a.

The incidence of mumps infection in the UK was reduced greatly by vaccination as a component of MMR vaccine, but cases and outbreaks continue to occur. Although in specialised laboratories RT-PCR is available for detection of mumps virus RNA in clinical samples, in routine laboratories virus isolation remains a standard method for diagnosing mumps virus infection. Furthermore, isolation of mumps virus strains circulating currently is important for monitoring the ability of vaccine-induced antibody to neutralise any genotypes recognised recently and to detect any changes in phenotype. In this study we compared rhesus monkey kidney (RMK) cells with the cell line B95a for mumps virus isolation from twenty throat swabs collected during a mumps outbreak in a religious community with low MMR coverage. Mumps virus was isolated from eight cases (40%), six were positive in both cell cultures and two in only one, all positive samples being collected within 2 days of onset. Virus growth in B95a cells was detected by the production of a syncytial cytopathic effect, and confirmed by an indirect fluorescent antibody test using a mumps monoclonal antibody. The B95a cell line was found to be equally as sensitive for mumps isolation as RMK cells, which are regarded as the 'gold standard', thus providing an alternative to the use of primary animal cell culture.

Animals↗
PubMed2001

A comparison of oral fluid collection devices for use in the surveillance of virus diseases in children.

Three oral fluid collection devices (OraSure, Omni-SAL and Oracol) were compared in terms of the quality of oral fluid collected by each device for antibody testing and their acceptability to participants. Participants (143 children aged 3.5-5 y from North Hertfordshire, UK, who had recently received DTaP and MMR vaccination) were randomised to use one of the three types of collection device. Oral fluid was collected by a parent who completed a short questionaire recording information on ease of use and willingness to use the device again. A matching serum sample was collected by a nurse. Oral fluid samples were screened for total IgG and IgM by ELISA and for rubella specific IgG and parvovirus specific IgG by radioimmunoassay. Serum samples were screened for rubella specific IgG and parvovirus B19 specific IgG by ELISA. 87.4% (125) of participants provided a matching oral fluid and serum sample. Of these, 100% (125) and 10.4% (13) had serum IgG specific for rubella and parvovirus B19, respectively. The Oracol device provided oral fluid samples with the highest geometric mean titres of total IgG and IgM and with rubella specific IgG results which correlated most closely with those of matching sera. A higher proportion of parents found the Oracol and OraSure devices easier to use than the Omni-SAL (P<0.001) and the proportion who would not take another test was higher for the Omni-SAL than for the Oracol or Orasure. Oral fluid samples collected by each of the devices gave qualitative results acceptable for surveillance and epidemiological studies of rubella and parvovirus B19. The highest quality oral fluid sample for antibody testing in terms of total IgG and IgM concentration and rubella specific IgG concentration was collected by the Oracol. The acceptability to participants of both the Oracol and OraSure was high. As the cheapest device available, the Oracol is the preferred oral fluid collection device for studies involving children in the UK.

Antibodies, Viral↗
PubMed2001

Has oral fluid the potential to replace serum for the evaluation of population immunity levels? A study of measles, rubella and hepatitis B in rural Ethiopia.

OBJECTIVE: To assess the suitability of using oral-fluid samples for determining the prevalence of immunity to vaccine-preventable infections. METHODS: Paired blood and oral-fluid samples were obtained from 853 individuals of all ages from a rural Ethiopian community. Oral fluid around the gums was screened for measles- and rubella-specific antibodies using enhanced IgG antibody capture (GAC) enzyme-linked immunosorbent assays (ELISAs), and for anti-HBc antibodies using a prototype GACELISA. IgG antibodies in serum to measles, rubella and HBc were determined using commercial ELISAs. FINDINGS: Relative to serum, oral fluid assay sensitivity and specificity were as follows: 98% and 87% for measles, 79% and 90% for rubella, and 43% and 87% for anti-HBc. These assay characteristics yielded population prevalence estimates from oral fluid with a precision equal to that of serum for measles (all ages) and rubella (ages < 20 years). CONCLUSION: Our results suggest that oral fluid could have the potential to replace serum in IgG antibody prevalence surveys. Further progress requires assessment of variation in assay performance between populations as well as the availability of standardized, easy to use assays.

Adolescent↗
PubMed2000

Atypical measles in a patient twice vaccinated against measles: transmission from an unvaccinated household contact.

Described are two cases within the same household that were involved in an outbreak of measles in Niterói, RJ. Measles diagnosis was confirmed serologically by specific IgM detection in Case 1 (classic measles) who was unvaccinated, and rising measles specific IgG in the absence of IgM in Case 2 (mild modified measles) who had a history of two vaccinations with measles-containing vaccines. Measles virus was detected by reverse transcriptase polymerase chain reaction (RT-PCR) in saliva samples from both cases. The nucleic acid amplified by RT-PCR was sequenced and showed identical measles sequence in the two cases. This study highlights the difficulty of diagnosing nonclassical measles infection on clinical and serological grounds, and the usefulness of PCR for viral RNA sequencing from noninvasive specimens for confirming epidemiologic links.

Adult↗
PubMed2000

Anaemia in lung transplant patient caused by parvovirus B19.

The case history is presented of a lung transplant patient who developed prolonged parvovirus B19 infection with severe transfusion dependent anaemia. The patient was treated with intravenous immunoglobulin after which the haemoglobin rose, together with a reticulocytosis. The patient then remained transfusion free and the virus cleared more than three months after the initial immunoglobulin treatment. The clinical and social implications for this group of patients are discussed.

Anemia↗
PubMed1999

Detection of measles specific IgG in oral fluid using an FITC/anti-FITC IgG capture enzyme linked immunosorbent assay (GACELISA).

An IgG antibody capture enzyme linked immunosorbent assay (GACELISA) for the detection of measles specific IgG in oral fluid was developed using an FITC/anti-FITC amplification system. The GACELISA was evaluated by testing paired oral fluid and serum samples from 787 subjects in an epidemiological study of measles in rural Ethiopia. Oral fluids were tested by GACELISA and corresponding serum samples by a sensitive indirect ELISA for measles IgG (Behring Enzygnost). By comparison with the serum measles IgG assay, the oral fluid GACELISA had a sensitivity of 97.4% (95% confidence intervals: 95.9, 98.2) and a specificity of 90.0% (81.9, 94.3), with no significant differences observed by age group. Total IgG concentrations were measured on a subset of 160 oral fluids by an in-house ELISA. This showed that false negative GACELISA results tended to occur in samples with low concentrations of total IgG, although the trend was not statistically significant. It is concluded that the overall performance of the GACELISA was satisfactory, showing close agreement to the serum ELISA, and has potential to serve as an easily transferable tool for large scale epidemiological studies as required for the World Health Organisation's programme for the global control of measles.

Antibodies, Viral↗
PubMed1999

Infection with wild-type mumps virus in army recruits temporally associated with MMR vaccine.

Four cases of mumps were reported among 180 army recruits who had received MMR vaccine 16 days earlier. Mumps serology, salivary mumps IgM and PCR tests for the SH gene were performed on the 4 cases and on 5 control recruits who remained well. PCR products were sequenced and the sequences compared to those of wild type and vaccine strains of mumps. Further salivary mumps IgM tests were performed on the remaining 171 recruits. Mumps infection was confirmed in the 4 cases but not in the 5 controls. The controls had serological evidence of prior immunity. The SH gene sequence found in the 4 cases was wild type. Saliva tests identified 2 additional recruits with mumps IgM, one of whom had presented with suspected mumps 2 days before the MMR vaccine was given. Thus 6 (5 symptomatic and 1 asymptomatic) cases of mumps in army recruits recently receiving MMR vaccine were not due to the vaccine but to coincidental infection with wild-type mumps virus. The probable index case was revealed by salivary mumps IgM tests. This study highlights the importance of appropriate investigation of illness associated with MMR vaccination.

Adult↗
PubMed1999

Guidance for control of parvovirus B19 infection in healthcare settings and the community.

Interventions for parvovirus B19 infection need to balance the low risk of infection at a population level with the potential for serious adverse outcome for particular groups, notably the fetus, people with haemoglobinopathies and the immunocompromised. This guidance aims to assist the local decision-making process to be as evidence-based as the available evidence allows.

Adolescent↗
PubMed1999

Detection of rubella virus-specific immunoglobulin G in saliva by an amplification-based enzyme-linked immunosorbent assay using monoclonal antibody to fluorescein isothiocyanate.

An immunoglobulin G (IgG)-capture enzyme-linked immunosorbent assay (ELISA) for rubella virus is described. The assay uses a fluorescein isothiocyanate (FITC)-anti-FITC amplification system. The detection limit of the ELISA was approximately 7 IU of rubella virus-specific IgG per ml of serum sample. For saliva samples the performances of the capture ELISA and previously described radioimmunoassay were assessed, and the results of those two assays were compared to the rubella virus-specific IgG result obtained by a commercial ELISA (Behring Enzygnost) with a panel of paired serum and saliva samples. This comparison showed that the capture ELISA with saliva was more sensitive than the radioimmunoassay and that the results correlated better with the serum IgG result than the results of the radioimmunoassay did, with an overall sensitivity of 82% and a rank correlation of 0.68, whereas the sensitivity and rank correlation for the radioimmunoassay were 74% and 0.45, respectively. For subjects of 10 years of age or younger, the ELISA with saliva had a sensitivity of 94% and a specificity of 100% compared to the results of the ELISA (Behring Enzygnost) for rubella virus-specific IgG with corresponding serum samples. The sensitivity was much lower for subjects ages 17 years or older. The assay may have wider epidemiological use with saliva specimens, particularly those from children.

Adolescent↗
PubMed1998

Acute parvovirus B19 infection associated with fulminant hepatitis of favourable prognosis in young children.

BACKGROUND: The cause of fulminant hepatitis (FH) in children is unexplained in up to 50% of cases. We report parvovirus B19 as an agent associated with FH in children and compare clinical characteristics of these patients with those of age-matched patients with FH of other origin. METHODS: 45 patients presented with FH. No cause was apparent in 21 patients. Parvovirus B19 genome was retrospectively sought by PCR in serum collected at admission in 41 patients. FINDINGS: Parvovirus B19 genome was detected in serum from four of 21 patients with unexplained FH (four of 11 younger than 5 years). No B19 DNA was detected in serum from patients with other types of FH or from 82 patients with biliary atresia. Parvovirus B19 IgM was detected in one of the four patients. Patients with parvovirus B19 infection had significantly lower bilirubin concentrations than age-matched patients with FH due to hepatitis A (nine) or other causes (nine) (poisoning with amanita excluded). All patients with parvovirus B19 survived without orthotopic liver transplantation, with restoration of normal liver function within 17 days. INTERPRETATION: In patients younger than 5 years with FH of unexplained origin, evidence of acute parvovirus B19 was associated with a distinct clinical pattern. In particular, low bilirubin concentrations and rapid recovery of liver function without transplantation were distinctive features.

Child, Preschool↗