Rubella seroprevalence in pregnant women in North Thames: estimates based on newborn screening samples.

OBJECTIVES: Routine screening for rubella susceptibility is recommended in the UK so that women found to be susceptible can be offered immunization in the post partum period. We demonstrate the use of newborn dried blood spot samples linked to routine vital statistics datasets to monitor rubella susceptibility in pregnant women and to investigate maternal characteristics as determinants of rubella seronegativity. SETTING: North Thames region of England (including large parts of inner London). METHODS: Maternally acquired rubella IgG antibody levels were measured in 18882 newborn screening blood spot samples. Latent class regression finite mixture models were used to classify samples as seronegative to rubella. Data on maternal country of birth were available through linkage to birth registration data. RESULTS: An estimated 2.7% (95% CI 2.4%-3.0%) of newly delivered women in North Thames were found to be seronegative. Mothers born abroad, particularly in Sub-Saharan Africa and South Asia, were more likely to be seronegative than UK-born mothers, with adjusted odds ratios of 4.2 (95% CI 3.1-5.6) and 5.0 (3.8-6.5), respectively. Mothers under 20 years were more likely to be seronegative than those aged 30 to 34. CONCLUSION: Our findings highlight the need for vaccination to be targeted specifically at migrant women and their families to ensure that they are protected from rubella in pregnancy and its serious consequences.

HIV-1 subtypes in pregnant women in the UK.

We analyse the distribution of HIV-1 subtypes in HIV-1-seropositive samples from 333,270 residual neonatal dried blood spot samples tested for routine newborn screening tests in the UK between July 1999 and December 2002. Of the 813 antibody-positive samples shown to contain passively acquired, maternal HIV-1 for which subtyping was attempted, 333 (41%) could not be subtyped due to cross-reactivity or low values of the assay results, and 480 (59%) were classified as B (35, 7.3%) or non-B (445, 92.7%). The proportions of subtyped B samples differed significantly (P=0.004) between those from neonates whose mothers were born in the UK (21.4%) and those from neonates whose mothers were known to be born abroad (7%). Using a serological approach to establish viral serotype, we document the distribution of HIV-1 subtypes in infected pregnant women in the UK.

Prevalence of antibodies to astrovirus types 1 and 3 in children and adolescents in Norfolk, Virginia.

OBJECTIVE: To determine the prevalence of antibody to human astrovirus types 1 (HAstV-1) and 3 (HAstV-3) in children. METHODS: Sera from children hospitalized in Norfolk, VA, for noninfectious conditions were collected for a 1-month period every 6 months from 1993 to 1996 and tested by enzyme immunoassay for antibody to HAstV-1 and HAstV-3 with the use of baculovirus-expressed recombinant capsid proteins as antigens. RESULTS: The seroprevalence of 393 infants and children to HAstV-1 decreased from 67% in infants <3 months of age to 7% by 6 to 8 months of age, consistent with loss of transplacental antibodies. Children acquired HAstV-1 antibody with a peak prevalence of 94% at 6 to 9 years of age (P < 0.001). Antibodies to HAstV-3 exhibited a lower prevalence, with 26% positive at <3 months, 0% at 6 to 11 months and 42% by 6 to 9 years of age. HAstV-1 seroprevalence in children O to 2 months of age decreased from 89% in November, 1993, to 40% in November, 1996 (P = 0.009). CONCLUSIONS: Astrovirus type-specific antibody prevalence can be measured by baculovirus-expressed capsid antigens in an enzyme immunoassay. Children developed antibody to HAstV-1 (94%) and to HAstV-3 (42%) by 6 to 9 years of age indicating frequent exposure to these enteric viruses in infancy and early childhood.

Modified latex agglutination test for antibodies to Toxoplasma gondii in eluates from Guthrie cards.

AIMS: To determine whether the Eiken particle agglutination test could be modified to make it sufficiently sensitive to screen blood samples collected on Guthrie cards for the presence of antibodies to Toxoplasma gondii; to evaluate the specificity of the modified system; and to compare seroepidemiological data on the prevalence of T gondii in pregnant women. METHODS: Simulated dried blood spots were prepared from sera from pregnant women booking for antenatal care. Eluates from the simulated dried blood spot cards and sera were tested in parallel using the modified test (1 in 5 dilution of latex) and the standard assay (neat latex particles) and endpoints determined. Guthrie card eluates, from neonates in three Thames regions, were then tested using the modified test. RESULTS: The modified test produced a 4.21-fold increase in antibody titre in 85 sera when tested in parallel with the standard test. Eluates of 168/170 from simulated dried blood spots derived from seropositive patients gave a positive result in the modified test. The two eluates which gave a negative result were derived from patients with an equivocal titre of 1/16 in the standard serum test. Of the eluates derived from serum negative patients all 103 were negative at a dilution of 1 in 4 in the modified test. The seroprevalence of antibodies to T gondii in pregnancy was 21.8% using the standard test. A similar value of 20.5% was obtained when dried blood spots from neonates in a similar region of London were tested by the modified test. CONCLUSIONS: The modified Eiken Toxo-reagent test is sensitive, simple, and economic for screening large numbers of dried blood spots. The procedure could be easily semiautomated and the technique applied to the mass screening of neonatal blood samples collected on Guthrie cards to determine the seroprevalence of T gondii in pregnant women.

An outbreak of rotavirus infection in a long-stay ward of a geriatric hospital.

An outbreak of rotavirus infection in elderly patients in a long-stay ward of a geriatric hospital is described. Virus was detected in 7/15 (47%) symptomatic individuals. Four members of staff were among those affected. The findings emphasise the need for electron microscopy to be used in the initial investigation of outbreaks of diarrhoea in all age groups.

Winter vomiting disease caused by calicivirus.

The clinical, epidemiological, and virological features of an outbreak of winter vomiting disease among London schoolchildren are described. Evidence is presented to support the view that this epidemic was caused by a human calicivirus, a virus not previously shown to be associated with this disease in man.

An outbreak of calicivirus infection in a mother and baby unit.

A small outbreak of infection due to a calicivirus occurred in a mother and baby unit. All the infants showed evidence of infection but the clinical features varied. None of the staff or mothers showed evidence of illness, and antibody studies indicated past experience of this virus.

Evaluation of five commercial assays for screening antenatal sera for antibodies to Toxoplasma gondii.

AIMS: To evaluate the suitability of five commercial assays (Toxoreagent, DA, Captia Toxo IgG, Toxenz-G, Toxonostika-G) for screening large numbers of sera for antibodies to Toxoplasma gondii. METHODS: Sera from 1000 pregnant women booking for antenatal care at a London hospital were screened in parallel by each test. Sera giving discordant results were retested. RESULTS: The Captia Toxo IgG enzyme immune assay gave the best specificity on initial screening, with 0/773 false positives and only 2/218 false negatives. The Toxoreagent latex agglutination test performed well provided sera were tested at several dilutions to prevent prozone effects; 0/218 false negatives (greater than 12 IU/ml). Only one evidently false positive result was seen in the 1000 samples tested. The DA test gave no false negative results but produced 23/773 false positives. After repeat testing there were 9/1000 sera which gave equivocal results which were negative by the Captia Toxo IgG test (less than 12 IU/ml) but with low titres of 16 in the Toxoreagent test or 4 IU/ml in the DA test. In this situation women would have been asked for a follow up sample for repeat testing. Only 300 sera were tested by Toxenz-G; initial screening produced 4/58 false negative results and 4/242 false positives. CONCLUSIONS: The Captia Toxo IgG test gave the fewest discordant results on initial screening. Results could be readily expressed in international units using a programmable plate reader, and this may be useful for epidemiological studies. The Toxoreagent test is considerably cheaper, and is a simple and reliable method for screening provided that at least two dilutions are used.

A new serotype of calicivirus associated with an outbreak of gastroenteritis in a residential home for the elderly.

An outbreak of gastroenteritis involving residents and members of staff in a nursing home for the elderly is described. The agent associated with this episode was a calicivirus which is serologically distinct from two strains causing gastroenteritis in children. We believe that this is the first report of calicivirus infection in adults.

Use of dried blood spots for the detection and confirmation of HTLV-I specific antibodies for epidemiological purposes.

AIMS--To modify and evaluate a gelatin particle agglutination test that could provide a sensitive, specific and inexpensive method for the detection of HTLV-I antibody in dried blood spot samples (DBS) collected on filter paper. METHODS--A set of 26 reference samples confirmed as HTLV-I antibody positive were assembled from patients with tropical spastic paraparesis or adult T cell leukaemia and blood donors. Serum samples and simulated antibody positive dried blood spot eluates were tested using the Serodia assay together with two confirmatory tests: HTLV BLOT 2.3, a western blot, and Select-HTLV, an enzyme immunoassay (EIA). Both confirmatory tests use synthetic peptides to differentiate between antibodies to HTLV-I and -II. The modified Serodia assay was then used to test anonymously 10,135 DBS collected from neonates from London. Samples reactive in the modified Serodia test producing a positive result were titrated to an end point and confirmed as before. RESULTS--All 26 eluates made from simulated DBS derived from positive reference samples were identified as positive by the modified Serodia HTLV-I test and were confirmed as anti-HTLV-I positive by EIA. Two eluates derived from relatively low titre reference samples gave indeterminate results on western blotting. Screening of the 10,135 neonatal DBS resulted in six repeat reactives, five of which were confirmed. The remaining reactive sample gave an indeterminate result on western blotting and there was insufficient eluate for testing by EIA. The overall seroprevalence of HTLV-I in this population was 0.05% (five of 10,135). CONCLUSION--The modified Serodia HTLV-I assay provides a sensitive, specific and inexpensive (10 pence/test) method for screening large numbers of DBS. The format of the assay makes it ideally suited for simultaneous screening of antibodies to HIV-1, HIV-2 and HTLV-I using semi-automated equipment.

Aplastic and hypoplastic episodes in sickle cell disease and thalassaemia intermedia.

Aplastic and hypoplastic crises are well recognised complications of sickle cell disease. Recent evidence has shown that most of these crises are caused by parvovirus infection. Five cases of aplastic or hypoplastic crises in patients born and living in this country were studied. Three patients had clear evidence of parvovirus infection, while in two evidence of parvovirus infection was lacking. One patient had evidence of concurrent parvovirus and Mycoplasma pneumoniae infection. Recurrent crises may occur, and reticulocyte monitoring during infection in patients with chronic haemolytic states is therefore important.

Pathology of astrovirus associated diarrhoea in a paediatric bone marrow transplant recipient.

Human astrovirus infection often causes outbreaks of self limiting diarrhoea, but may also infect patients who are immunodeficient or immunocompromised. Although there are previous publications relating to various aspects of astroviruses, there is a minimal amount of literature on the histopathological features of gastrointestinal astrovirus infection in humans. We report the histopathological findings, including immunohistochemical and electron microscopic features, of astrovirus infection in a bone marrow transplant recipient aged 4 years with diarrhoea. The appearance of a small intestinal biopsy did not suggest graft versus host disease, but demonstrated villous blunting, irregularity of surface epithelial cells, and an increase in lamina propria inflammatory cell density. Immunohistochemical staining with a murine astrovirus group specific monoclonal antibody demonstrated progressively more extensive staining in the duodenal and jejunal biopsies, predominantly restricted to the luminal surface and cytoplasm of surface epithelial cells, most marked at the villus tips. Electron microscopic examination demonstrated viral particles within the cytoplasm of enterocytes, focally forming paracrystalline arrays.

Impact of rotavirus infection on a paediatric hospital in the east end of London.

AIMS: To study the impact of confirmed rotavirus infection at a paediatric hospital; to use the data to obtain a minimum estimate of the cost of treating reported cases of rotavirus in England and Wales. METHODS: Data were obtained on all patients with rotavirus over a two year period. Information was collected on 386 patients with rotavirus infection who were treated at the 120 bed Queen Elizabeth Hospital for Children in East London. This included the virus serotype, the patient's age, whether they required intravenous infusion, duration of hospital stay, numbers of patients treated in the casualty department, and numbers who had to be admitted. Treatment costs were obtained from the Finance Department of the Hospitals for Sick Children. RESULTS: The minimum cost of treating patients, excluding the cost of medical staff at the hospital, was estimated to be 95,400 pounds a year. One hundred and forty eight (38%) patients were admitted to the wards and a further 49 patients developed symptoms while in hospital. Intravenous infusion was required by 18 patients. The mean duration of hospital stay was 5.5 days. One hundred and eighty nine (49%) patients were treated with oral rehydration solution in casualty, given advice, and sent home. Ninety four per cent of the patients were aged under 2 years. The findings were comparable with those obtained in a study at Texas Children's Hospital, USA. The G serotype (VP7) of rotavirus did not influence the severity of infection. CONCLUSION: Rotavirus infections accounted for a significant number of patients treated in casualty, admissions to hospital, and bed occupancy in a paediatric hospital. The estimated cost of treating reported cases of rotavirus in England and Wales is in excess of 6.3 pounds million a year.

Historical background and classification of caliciviruses and astroviruses.

Infections caused by caliciviruses, i.e., vesicular exanthema virus of swine were recognised as a major cause of economic loss in the 1930s. However, it was not until the application of electronmicroscopy in the 1970s that caliciviruses and astroviruses were recognised and proven to be a cause of diarrhoea and vomiting. The following review briefly describes the steps which have led to the development of diagnostic tests and enabled the characterization of several members of the Caliciviridae and Astroviridae. In the past five years this has culminated in the sequencing of their genomes and the expression of viral proteins. This in turn has led to the development of improved diagnostic tests e.g., RT-PCR and enzyme immunoassays, and may pave the way towards producing effective vaccines in the future.

Genetic and antigenic diversity of human caliciviruses (HuCVs) using RT-PCR and new EIAs.

RT-PCR using primers from conserved regions of calicivirus genomes, followed by sequencing, permits characterization of genetic variation within the family. EIAs based on baculovirus-expressed viral capsid proteins and hyperimmune antisera against the capsid proteins were developed to detect HuCV antigens and antibodies. Serologic surveys using recombinant Norwalk virus (rNV) and recombinant Mexico virus (rMX, a SMA-like virus) EIAs showed that infections by HuCVs are common and that children acquire antibodies to HuCVs at an early age in both developed and developing countries. Three HuCV genogroups have been described that are represented by Norwalk virus (NV), Snow Mountain agent (SMA), and Sapporo virus, although recently accumulated sequences of HuCV strains indicate these genogroups can be further divided. These genogroups also correspond to distinct antigenic groups based on the results of the recombinant EIAs. The three genogroups co-circulate and have a worldwide distribution, although the SMA genogroup seems to be predominant currently. Application of these new assays for further characterization of the genetic and antigenic properties of HuCVs remains an important task for HuCV research.

The development and evaluation of radioimmune assays for the detection of immune globulins M and G against astrovirus.

The development and evaluation of radioimmune assays for the detection of IgM and IgG antibodies to astrovirus are described. The test was shown to be sensitive and specific, and suitable for screening large numbers of sera. The use of the assays has established that astrovirus type 1 is prevalent in the United Kingdom and that not only infants but also schoolchildren and elderly patients are affected. Further evidence is given to support the view that Marin County Agent is antigenically related to astrovirus type 1.

Improved immunofluorescence techniques with microplates for the detection of M and G immunoglobulins against rotavirus.

A selection of microplates and an inverted microscope were used for the detection of immuno-fluorescence in large numbers of infected cell monolayers. The optical features of this instrument in combination with either Terasaki or Microlymp plates, simplify procedures and allow economical use of reagents, for determining fluorescent antibody levels. The techniques described were applied for estimating M and G immunoglobulins against rotavirus in elderly patients and the validity of the tests was established.

Propagation of human astrovirus in the PLC/PRF/5 hepatoma cell line.

Astroviruses are associated with gastroenteritis in humans and many diseases in animals. Human astroviruses (HAstVs) cannot be propagated readily or isolated in conventional cell cultures. The presence of trypsin supports HAstV growth in selected cell cultures such as the continuous colonic carcinoma cell line (CaCo-2). This study reports on the propagation of cell culture adapted reference strains of HAstV, and the direct isolation of HAstV from stool specimens in the human hepatoma cell line PLC/PRF/5.

A method for the detection and confirmation of antibodies to hepatitis C virus in dried blood spots.

This study describes the development and evaluation of a cost effective test rationale for the detection of anti-HCV in dried blood spots. Samples were screened using an 'in house' IgG ELISA that incorporated the recombinant proteins c22-3, c200 and NS5. Confirmation of specific antibody to HCV was by a modification of the immunoblot RIBA 3.0. An extensive panel of well evaluated anti-HCV positive and negative samples from the UK and South Africa were used to assess the sensitivity and specificity of the two tests. One third of the anti-HCV positive samples had been typed. All anti-HCV positive samples were detected by the 'in house' screening EIA. Test/negative optical density ratios showed that more than 95% of reactive samples produced values greater than 5.0. Antibodies to HCV could be detected in a wide range of samples derived from asymptomatic and symptomatic patients and of different genotypes, with similar sensitivity. The presence of anti-HCV could be confirmed by RIBA 3.0 in samples with low reactivity but not in anti-HCV negative samples. Furthermore the immunoblot assay successfully increased specificity by screening out false reactive EIA samples that might occur in an epidemiological survey of a multi-ethnic population.

PIP: While hepatitis C virus (HCV) is a major etiological agent of post-transfusion and community acquired non-A, non-B hepatitis, little is known about the epidemiology of HCV in the UK. A cost-effective method using dried blood spots to determine anti-HCV IgG in subjects which could be used in large-scale epidemiological studies is described. Samples were screened using an in-house IgG ELISA incorporating the recombinant proteins c22-3, c200, and NS5, while specific antibody to HCV was confirmed using a modified immunoblot RIBA 3.0. A panel of well evaluated anti-HCV positive and negative samples from the UK and South Africa were used to assess the sensitivity and specificity of the 2 tests. All anti-HCV positive samples were detected by the in-house screening EIA. Test/negative optical density ratios showed that more than 95% of reactive samples produced values greater than 5.0. Antibodies to HCV could be detected in a wide range of samples derived from asymptomatic and symptomatic patients and of different genotypes, with similar sensitivity. The presence of anti-HCV could be confirmed by RIBA 3.0 in samples with low reactivity, but not in anti-HCV negative samples. The immunoblot assay increased specificity by screening out false reactive EIA samples.

Outbreaks of astrovirus type 1 and rotavirus gastroenteritis in a geriatric in-patient population.

Two outbreaks of viral gastroenteritis occurred in seven psychogeriatric wards of a 469-bed psychiatric hospital. The outbreaks occurred over an eight-week period; the first affected 30 people and rotavirus was detected in 12 of 14 persons from whom faecal specimens were available. The second affected 32 people (15 of whom were affected in the previous outbreak) and astrovirus was detected in 5 of the 24 people from whom specimens were available. Specific IgM to astrovirus was demonstrated in 3 patients. The rotavirus outbreak was characterised by a longer duration of illness (mean 4 days), and more severe symptoms; two elderly female patients had severe symptoms over a 14-15 day period but recovered. In the astrovirus outbreak the duration of illness was shorter and symptoms were milder although the attack rate was higher than that observed for rotavirus.