Skin T cell proliferative response to M protein and other cell wall and membrane proteins of group A streptococci in chronic plaque psoriasis

To determine and compare the T cell response to M protein and other group A streptococcal (GAS) antigens, T cell lines (TCL) were cultured from the lesional skin of 33 psoriatic patients and 17 disease controls. GAS-reactive skin TCL were tested in proliferation assays with recombinant M6 protein, and extracts of cell wall and membrane from type M6 GAS and its corresponding M gene deletion mutant. Initially, GAS-reactive skin TCL were obtained from 16 of 25 (64%) psoriasis, and from seven of 17 (41%) control patients. Eleven psoriatic and four control GAS-reactive TCL proliferated to M6 cell wall extract, whereas all the TCL from both groups responded to the extract of M6 membrane proteins. This difference in response to the two extracts was significant for both groups of patients (psoriasis, P = 0.0335, controls, P = 0.0156). GAS-reactive TCL from a further eight psoriasis patients showed no difference in response to cell wall extract from M6 GAS (containing the M protein minus its C-terminus) compared to that of its corresponding M gene deletion mutant. Furthermore, GAS-reactive TCL did not proliferate to recombinant M6 protein. However, a small, but significant reduction in proliferation by the eight psoriatic GAS-reactive TCL to the M-negative (lacking the M protein C-terminus) compared to M6-positive membrane extract was observed (P = 0.01). These findings suggest that GAS-reactive T cells in skin lesions of chronic plaque psoriasis proliferate to streptococcal membrane and, to a lesser extent, cell wall proteins. However, psoriatic skin T cells do not recognize cell wall M protein.

Epidermal CD8+ T cells in chronic plaque psoriasis are Tc1 cells producing heterogeneous levels of interferon-gamma

The majority of epidermal CD8+ T cells in chronic plaque psoriasis are activated Tc1 cells producing interferon-gamma and no interleukin-4, a small proportion of which express NK-T receptors. To quantitate their level of cytokine production and characterize them further, CD8+ T cells were isolated from epidermal cell suspensions of lesional biopsies from 24 patients with chronic plaque psoriasis. T-cell lines (TCL) were established by culture of CD8+ T cells with feeders and IL-2 for 11 days and expansion with PHA. Ten TCL were stained for surface markers; 6 were cloned with PHA by limiting dilution. Interferon-gamma, interleukin-4 and interleukin-10 production was measured by ELISA after PMA/anti-CD3 activation of 15 TCL and 39 CD8+ T-cell clones. The 10 TCL stained were CD8alphabeta+ (93.3%), T-cell receptor-alphabeta+ (99.5%), costimulatory molecule CD28+ (90.1%), with a small CD8alphaalpha+ population (2.3%). No NK-T-cell receptor CD158a or CD158b expression was detected, whilst CD94 was expressed on 6.2% of cells in 6/9 TCL. All the TCL and 37/39 CD8+ T-cell clones produced interferon-gamma but no or minimal interleukin-4 or interleukin-10. The TCL produced a wide range of interferon-gamma levels (138 to 15,020 pg/ml). Clones from 3 patients showed low levels (60 to 1,410 pg/ml), from 2 patients high levels (6,105 to 43,040 pg/ml) and from 1 patient a wide range (405 to 36,010 pg/ml) of interferon-gamma production. Thus epidermal CD8+ Tc1 cells in chronic plaque psoriasis produce highly heterogeneous levels of interferon-gamma, which may reflect clinical diversity.

Rotavirus G and P genotypes in rural Ghana

An epidemiological study of rotavirus infection was conducted on specimens collected from patients with gastroenteritis and domiciled in the rural Upper Eastern Region of Ghana during 1998. Fifty isolates, randomly selected from 165 human group A rotavirus-positive samples, were G and P characterized by a reverse transcription (RT)-PCR assay using a seminested multiplex method. Rotaviruses of the G3 genotype were found to be the predominant strain (78%), followed by G2 (14%) and G1 (2%). Mixed infections, as shown by combinations of G3 and G2 (4%) and G3 and G1 (2%), were also observed. P typing showed P[4] (72.34%) to be the prevalent strain, followed by P[6] (21.3%), P[8] (2.13%), and a combination of P[4] and P[6] (4.3%).

Non-M protein(s) on the cell wall and membrane of group A streptococci induce(s) IFN-gamma production by dermal CD4+ T cells in psoriasis

Recently we have demonstrated that a disease-specific subpopulation of CD4+ T cells isolated from skin lesions of chronic plaque psoriasis produces interferon-gamma in response to group A streptococcal (GAS) antigens. To determine if these T cells recognize M or non-M protein, extracts from cell wall of type M6 GAS (M6W) and its isogenic M gene deletion mutant (M-W), M6 membrane extract (M6M) and recombinant M6 protein (rM6) were used to stimulate GAS-reactive T-cell lines from nine patients with chronic plaque psoriasis. T-cell lines were incubated with or without streptococcal extracts for 18 h in the presence of a transport inhibitor, stained for surface CD4 and intracellular cytokine expression, and analysed by flow cytometry. Variable numbers (0.2-34%) of CD4+ T cells produced interferon-gamma, in all but one of the T-cell lines tested, in response to M6W, M-W and M6M extracts. No significant difference between the response to M6W and M-W extracts was detected. In addition, rM6 protein failed to increase CD4+/interferon-gamma+ T-cell numbers in seven of nine T-cell lines compared to medium alone. For the group, there was a highly significant correlation between the responses to the three extracts (M6W vs M-W, P = 0.0005; M6W vs M6M, P = 0.0003; M-W vs M6M, P = 0.0001). Low or minimal numbers of interleukin-4- and interleukin-10-producing CD4+ T cells were occasionally induced. These findings suggest that a subpopulation of CD4+ T cells isolated from skin lesions of chronic plaque psoriasis patients produces interferon-gamma in response to non-M protein(s) present on the cell wall and membrane of GAS.

Capsid protein diversity among Norwalk-like viruses

We have determined the complete capsid gene sequence of 20 Norwalk-like viruses (NLVs) collected predominantly from outbreaks in the UK between 1989 and 1996. These comprised nine genogroup I and eleven genogroup II strains. Phylogenetic analysis of these and 15 published sequences suggest seven genomic sub-groups within genogroup I, including three previously described. In genogroup II, eight sub-groups were apparent, of which four were novel. Amino acid identities between strains of distinct genogroups ranged from 37 to 44% while varying between 61 and 100% for strains within a genogroup. Separate phylogenetic analyses of the N-terminus and central variable region of the capsid showed good correlation. Sequence divergence between strains was greatest within the central variable region, with amino acid sequence identities as low as 28% within a genogroup. These 15 genomic sub-groups provide a framework for further investigations of genetic and antigenic relationships within this calicivirus clade.

A Genetic and Biochemical Approach to Study Trichothecene Diversity in Fusarium sporotrichioides and Fusarium graminearum

The trichothecenes T-2 toxin and deoxynivalenol (DON) are natural fungal products that are toxic to both animals and plants. Their importance in the pathogenicity of Fusarium spp. on crop plants has inspired efforts to understand the genetic and biochemical mechanisms leading to trichothecene synthesis. In order to better understand T-2 toxin biosynthesis by Fusarium sporotrichioides and DON biosynthesis by F. graminearum, we compared the nucleotide sequence of the 23-kb core trichothecene gene cluster from each organism. This comparative genetic analysis allowed us to predict proteins encoded by two trichothecene genes, TRI9 and TRI10, that had not previously been described from either Fusarium species. Differences in gene structure also were correlated with differences in the types of trichothecenes that the two species produce. Gene disruption experiments showed that F. sporotrichioides TRI7 (FsTRI7) is required for acetylation of the oxygen on C-4 of T-2 toxin. Sequence analysis indicated that F. graminearum TRI7 (FgTRI7) is nonfunctional. This is consistent with the fact that the FgTRI7 product is not required for DON synthesis in F. graminearum because C-4 is not oxygenated.

White blood cell count: an independent predictor of coronary heart disease mortality among a national cohort

An association between elevated white blood cell (WBC) count and coronary heart disease (CHD) mortality has been previously observed. However, the relationship between WBC count and CHD mortality independent of cigarette smoking and the possible interaction between WBC count and smoking remains unclear. We examined the association between WBC count and CHD mortality with Cox regression analyses of data from 8914 adults, aged 30-75, in the NHANES II Mortality Study (1976-1992). Covariates included age, sex, race, education, physical activity, smoking status, hypertensive status, total serum cholesterol, body mass index, hematocrit, and history of cardiovascular disease, stroke, and diabetes. During 17 follow-up years, there were 548 deaths from CHD (ICD-9 410-414) and 782 deaths from diseases of the heart (ICD-9 390-398, 402, 404, 410-414, 415-417, 420-429). Mean WBC count (x10(9) cells/L) was greater among persons who died from CHD (7.6 vs 7.2, P <.001). Compared to persons with a WBC count <6.1, persons with a WBC count > 7.6 were at increased risk of death from CHD (relative risk = 1.4, 95% confidence interval = 1.1-1.8) after adjustment for smoking status and other CVD risk factors. Similar results were observed among nonsmokers (RR = 1.4, 95% CI = 0.9-2.0). These results suggest that higher WBC counts are a predictor of CHD mortality independent of the effects of smoking and other traditional CVD risk factors, which may indicate a role for inflammation in the pathogenesis of CHD. Additional studies are needed to determine whether interventions to decrease inflammation can reduce the risk for CHD associated with elevated WBC.

Genetic polymorphism across regions of the three open reading frames of "Norwalk-like viruses"

Genomic characterization of Norwalk-like human caliciviruses (NLVs) originating from outbreaks and sporadic cases of acute gastroenteritis has revealed surprisingly high levels of diversity, even in the RNA polymerase gene, which is anticipated to be highly conserved. Since information on antigenic relationship is limited, due to the lack of a tissue culture system for these viruses, strains mostly are described on the basis of their genetic relatedness. However, the lack of uniformly applied criteria has led to a confusing array of strains with different groups employing different names for similar genetic lineages. Our goal was to conduct a structured analysis of genomic relationships among NLV strains in an attempt to provide an interim framework for genotyping. We assembled a panel of 31 potentially distinct genogroup I (GGI) and genogroup II (GGII) NLVs that reflected the diversity seen in strains detected by our laboratories and in published sequences. Phylogenetic analysis of sequences from regions of the open reading frames (ORF) 1, 2 and 3 was performed in order to investigate genomic relationships. The strains sequenced fell into seven phylogenetic groups in GGI and at least five phylogenetic groups in GGII, based on greater than 80% nucleotide identity in the region of ORF2 encoding the N-terminus of the capsid protein, and consistent clustering with high bootstrap values irrespective of the method used. Analysis of the ORF1 and ORF3 regions supported for most strains the clustering as established for those derived from ORF2. In the ORF1 region, used by most laboratories for diagnostic RT-PCR, clustering was consistent when a putative genotype border was set at 15% nucleotide mismatches for viruses in GGI and at 10% for viruses in GGII. Two strains grouped within different clusters based on ORF1 and ORF2 indicating that recombination may have occurred. We discuss the implications of these observations for the classification and typing of NLVs.

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.

Left ventricular hypertrophy as a predictor of coronary heart disease mortality and the effect of hypertension

BACKGROUND

Although associations between hypertension, left ventricular hypertrophy (LVH), and coronary heart disease (CHD) have been described, it is less clear whether LVH is associated with increased rates of CHD in the absence of hypertension.

METHODS

We examined this association with Cox regression analyses of data from 7924 adults 25 to 74 years of age from the Second National Health and Nutrition Examination Survey (NHANES II) Mortality Study (1976 to 1992). Covariates included age, race, sex, history of cardiovascular diseases and diabetes, cholesterol, body mass index, blood pressure, and smoking.

RESULTS

During 16.8 follow-up years, there were 462 (26%) deaths from CHD (ICD-9 410-414) and 667 (38%) deaths from diseases of the heart (ICD-9 390-398, 402, 404, 410-414, 415-417, 420-429). LVH prevalence was 13.3 per 1000 population. Hypertension prevalence was 29.1%. LVH prevalence was higher among hypertensive adults than among normotensive adults (29.9 vs 6.4 per 1000, P <.001). Persons with LVH were twice as likely to die of CHD (relative risk, 2.0; 95% confidence interval, 1.2, 3.5) and diseases of the heart (relative risk, 1.9; 95% confidence interval, 1.1, 3.0) after adjustment for hypertension and covariates. In age-adjusted predicted survival, probability plots for CHD, and diseases of the heart, normotensives with LVH had survival similar to hypertensive adults with LVH and lower survival than normotensive and hypertensive adults with no LVH.

CONCLUSIONS

Our results confirm previous findings that the presence of LVH is a strong predictor of future cardiovascular death. Although LVH appears to be rare among normotensives, clinicians should be aware that such individuals may have an increased risk for death similar to that of hypertensive adults with LVH.

Molecular epidemiology of human group A rotavirus infections in the United Kingdom between 1995 and 1998

The G and P types of 2,912 rotavirus-positive fecal specimens collected from eight geographical areas of the United Kingdom between 1995 and 1998 were determined by reverse transcription-PCR. Although 15 different G-P combinations were identified, G1P[8], G2P[4], G3P[8], and G4P[8] strains constituted 95% of all the rotaviruses typed. Other genotypes included G9P[6] and G9P[8], which were first identified in the United Kingdom in 1995, or other uncommon G and/or P types of strains that may have had an animal origin. Unusual combinations of G1 or G4 with P[4] and G2 with P[8] which may have arisen by reassortment between human strains were also identified. G1P[8] was the genotype most frequently found (57 to 87%) in each season, followed by G2P[4] in the 1995-1996 (18%) and 1997-1998 (16%) seasons, although the incidence of infection with this virus decreased significantly to 2% during the 1996-1997 season. Significant differences were seen in the distributions of G1P[8], G2P[4], and G9P[8] strains between children and adults, in the temporal distributions of G4P[8] and G9P[8] strains within a season, and in the geographical distributions of each of the four most common genotypes from one season to the next.

Interactions between herpes simplex virus type 2 and human immunodeficiency virus type 1 infection in African women: opportunities for intervention

Sexually transmitted diseases (STDs) are cofactors for human immunodeficiency virus (HIV) transmission, but the specific role of herpes simplex virus type 2 (HSV-2) is unclear. This study aimed to examine the in vivo relationships between HSV-2 and HIV-1 in 300 women in Bangui, Central African Republic. Sera were tested for syphilis, HIV-1, HSV-2 antibody, and levels of vitamins A and E. Genital specimens were tested for other STDs. HSV-2 DNA and HIV-1 RNA were quantified in cervicovaginal lavage. The prevalences of HSV-2 antibody (91% vs. 78%, P=.02), HSV-2 shedding (43% vs. 22%, P=. 003), and levels of HSV-2 DNA (P=.01) were all significantly higher among HIV-1-seropositive than among HIV-1-seronegative women. There was a significant correlation between genital HIV-1 RNA and HSV-2 DNA levels (P=.02) among the 23 women who were shedding HSV-2 DNA. If confirmed, such associations highlight the urgent need for HSV-2 control measures in populations at high risk of both infections.

Influenza virus infection in the second and third trimesters of pregnancy: a clinical and seroepidemiological study

OBJECTIVE

To determine whether maternal influenza virus infection in the second and third trimesters of pregnancy results in transplacental transmission of infection, maternal auto-antibody production or an increase in complications of pregnancy.

DESIGN

Case-control cohort study.

POPULATION

Study and control cohorts were derived from 3,975 women who were consecutively delivered at two Nottingham teaching hospitals between May 1993 and July 1994. A complete set of three sera was available for 1,659 women.

METHODS

Paired maternal ante- and postnatal sera were screened for a rise in anti-influenza virus antibody titre by single radial haemolysis and haemagglutination inhibition. Routine obstetric data collected during and after pregnancy were retrieved from the Nottingham obstetric database. Cord samples were tested for the presence of IgM anti-influenza antibodies, and postnatal infant sera were tested for the persistence of influenza-virus specific IgG. Paired antenatal and postnatal sera were tested against a standard range of auto-antigens by immunofluorescence.

MAIN OUTCOME MEASURES

Classification of women as having definite serological evidence of an influenza virus infection in pregnancy (cases) or as controls.

RESULTS

Intercurrent influenza virus infections were identified in 182/1,659 (11.0%) pregnancies. None of 138 cord sera from maternal influenza cases was positive for influenza A virus specific IgM. IgG anti-influenza antibodies did not persist in any of 12 infant sera taken at age 6-12 months. Six of 172 postnatal maternal sera from cases of influenza were positive for auto-antibodies. In all cases the corresponding antenatal serum was also positive for the same auto-antibody. There were no significant differences in pregnancy outcome measures between cases and controls. Overall, there were significantly more complications of pregnancy in the cases versus the controls, but no single type of complication achieved statistical significance.

CONCLUSIONS

Influenza infection in the second and third trimesters of pregnancy is a relatively common event. We found no evidence for transplacental transmission of influenza virus or auto-antibody production in pregnancies complicated by influenza infections. There was an increase in the complications of pregnancy in our influenza cohort.

The genomic sequence of a contemporary wild-type mumps virus strain

Vaccination has the potential to eradicate mumps, and 82 countries now include a live attenuated mumps vaccine as part of their childhood vaccination programme. Although, monotypic, genetic variants of mumps virus (MuV) have been described based on comparison of the SH gene sequences, and at least seven genotypes have been identified. We now report the entire sequence of a recently isolated wild type MuV strain, Glouc1/UK96 (Glouc1) by direct sequencing of the cDNA obtained from cell culture fluid. The genome of this recent isolate was 15384 nucleotides in length. There were 579 nucleotide differences (3.8%) and 71 amino acid differences (1.5%) between Glouc1, a genotype G strain and Ur-AM9, a genotype B strain. Other MuV strains with available sequences were also compared with this pathological strain. The sequence of the contemporary strain reported here provides a picture of the variability of MuV over its entire genome (GenBank accession no. AF280799).

Widespread environmental contamination with Norwalk-like viruses (NLV) detected in a prolonged hotel outbreak of gastroenteritis

A protracted outbreak of Norwalk-like virus (NLV)-associated gastroenteritis occurred in a large hotel in North-West England between January and May 1996. We investigated the pattern of environmental contamination with NLV in the hotel during and after the outbreak. In the ninth week, 144 environmental swabs taken from around the hotel were tested for NLV by nested RT-PCR. The sites were categorized according to the likelihood of direct contamination with vomit/faeces. The highest proportion of positive samples were detected in directly contaminated carpets, but amplicons were detected in sites above 1.5 m which are unlikely to have been contaminated directly. The trend in positivity of different sites paralleled the diminishing likelihood of direct contamination. A second environmental investigation of the same sites 5 months after the outbreak had finished were all negative by RT-PCR. This study demonstrates for the first time the extent of environmental contamination that may occur during a large NLV outbreak.

Comparison of a monoclonal antibody-blocking enzyme-linked immunoassay and a strip immunoblot assay for identifying type-specific herpes simplex virus type 2 serological responses

Detection of herpes simplex virus type 2 (HSV-2)-specific antibodies by a monoclonal antibody (MAb)-blocking enzyme-linked immunoassay (EIA) was compared with detection by a strip immunoblot assay (SIA) in a sexually transmitted disease (STD) clinic population. The study population consisted of 1,683 genitourinary medicine clinic attendees (582 women and 1,101 men). Sera were tested for the presence of HSV-2 antibody by use of the blocking EIA, in which binding of the MAb AP-1 to HSV-2 glycoprotein G-2 (gG-2) is blocked by HSV-2-specific antibody. The Chiron RIBA HSV-1 and -2 strip immunoassay (SIA) utilizes HSV-1- and HSV-2-specific or cross-reactive antigens immobilized on nitrocellulose strips (HSV gB-1 and HSV gG-1 peptide bands specific for HSV-1 antibody, HSV-2 gG-2 band specific for HSV-2 antibody, and HSV gD-2 band cross-reactive for HSV-1 and HSV-2 antibodies). A total of 1,612 sera were tested by MAb-blocking EIA for HSV-2 antibody and by SIA for HSV-1 and HSV-2 antibodies. By EIA, 541 (33.6%) sera were positive for HSV-2 antibody and 1,068 sera were negative for HSV-2 antibody; 3 sera gave equivocal results. HSV-2 antibody was detected in 555 (34.4%) sera by SIA; 144 (26%) of these sera possessed only HSV-2 antibody, and 411 (74%) sera contained both HSV-1 and HSV-2 antibodies. SIA detected HSV-1 antibody in 1,155 (71.6%) sera; 744 (64%) of these sera contained HSV-1 antibody alone. Sixteen sera contained antibody against HSV but could not be typed by SIA. A total of 512 sera were positive for HSV-2 antibody by both the EIA and SIA. We concluded that the blocking EIA and SIA showed a high level of agreement in detecting HSV-2 antibody in this population. In contrast to the SIA, the blocking EIA is a useful tool for large epidemiological studies, though the SIA proved to be slightly more sensitive once sera with discrepant results were further tested.

Diagnosis of rubella infection by detecting specific immunoglobulin M antibodies in saliva samples: a clinic-based study in Niterói, RJ, Brazil

This study was designed to investigate whether saliva could be a feasible alternative to serum for the diagnosis of recent rubella infection in a clinic setting. Forty-five paired blood and saliva samples collected 1 to 29 days after onset of illness were tested for specific immunoglobulin (Ig) M by antibody-capture radioimmunoassay (MACRIA). Rubella IgM was detected in all serum samples and in 38 (84.4%) saliva specimens. Forty-six serum and saliva samples from other patients with rash diseases were tested by MACRIA for control purposes and two saliva specimens were reactive. The saliva test had specificity of 96%. These results indicate that salivary IgM detection may be a convenient non-invasive alternative to serum for investigation of recent rubella cases, especially for disease surveillance and control programmes.

The burden of infection with HSV-1 and HSV-2 in England and Wales: implications for the changing epidemiology of genital herpes

OBJECTIVE

To measure the burden of infection with herpes simplex type 1 (HSV-1) and herpes simplex type 2 (HSV-2) in the general population of England and Wales and to assess temporal changes in the incidence of HSV-1 infection in childhood.

METHODS

4930 residual blood samples taken from people aged 0-69 years and submitted to 15 public health laboratories in England and Wales between January 1994 and June 1995, and 500 samples taken from people aged 10-14 years between November 1986 and December 1987, were screened for IgG antibody to HSV-1 and HSV-2 using type specific ELISA assays.

RESULTS

The prevalence of antibody to HSV-1 in 10-14 year olds declined from 34% in samples collected in 1986-7 to 24% in samples collected in 1994-5 (p < 0.001). HSV-1 antibody prevalence in adults increased with age and was higher in females than males, reaching 54% in females aged 25-30 years in 1994-5. In samples collected in 1994-5 from people aged 16-69 years HSV-2 antibody was detected in sera from 3.3% of men and 5.1% of women.

CONCLUSIONS

The incidence of HSV-1 infection in childhood is falling in England and Wales. The prevalence of HSV-2 infection in the general population is low, with the rate of infection significantly lower than that described for the general population in the United States and developing countries. The falling rate of HSV-1 infection in childhood may be one factor contributing to the increasing incidence of genital HSV-1 infection.

A monoclonal blocking EIA for herpes simplex virus type 2 antibody: validation for seroepidemiological studies in Africa

A competitive type-specific enzyme-linked immunosorbent assay (ELISA) for herpes simplex virus type 2 (HSV-2) antibody was developed using an infected cell antigen and a monoclonal antibody to glycoprotein G-2. This assay has been validated for use for epidemiological studies using a large panel of sera collected in rural Uganda and a panel of 143 sera characterised previously by Western blotting, the 'gold standard' for HSV type-specific serology. This evaluation was found to have a sensitivity of 96% and a specificity of 91% in comparison with Western blot on 143 sera from clinic patients. The ELISA had a sensitivity of 93% and a specificity of 91% in comparison with Western blot on 495 sera collected in Uganda. The assay showed good reproducibility and a low percentage of sera gave equivocal results, indicating its suitability for epidemiological studies.

The heteroduplex mobility assay (HMA) as a pre-sequencing screen for Norwalk-like viruses

Molecular epidemiological studies of Norwalk-like viruses (NLVs), previously known as small round structured viruses (SRSVs), are dependant currently on DNA sequencing of PCR amplicons, which is expensive and time consuming. The Heteroduplex Mobility assay (HMA) was evaluated as a method for identification of PCR amplicons from the commonly circulating NLV strains without DNA sequencing. The procedure was developed for use with two reference strains, a Mexico virus-like strain (MXV-like; Hu¿NLV¿RBH¿1993¿UK) and the Grimsby virus strain (Hu¿NLV¿Gimsby¿1995¿UK), and was optimised with regards to the annealing and electrophoresis conditions and the electrophoresis gel matrix. Using the optimised conditions, amplicons of less than 90% sequence identity formed visible heteroduplexes, allowing the strains to be placed into three categories; Mexico-like, Grimsby-like and non-Mexico virus/non-Grimsby virus strains. Outbreak strains 'genotyped' previously by DNA sequencing as Mexico virus or Grimsby virus were identified correctly by the heteroduplex mobility assay. The procedure was applied prospectively to strains from 130 outbreaks occurring in the UK between 1997 and 1998. Heteroduplex mobility assay was successful on 120 (92%) strains of which 68 (57%) were GRV-like strains, three (2.5%) were Mexico virus-like strains and 49 (41%) were categorised as non- Mexico/non-Grimsby virus strains. Amplicons from 50 of the 120 strains were sequenced and there was perfect correlation between the heteroduplex mobility assay categorisation and phylogenetic analysis. HMA offers a rapid, robust and far cheaper alternative to sequencing for the identification of prevalent Norwalk-like virus genotypes for molecular epidemiological studies.

Cloning and heterologous expression of Solorina crocea pyrG

A pyrG gene, encoding orotidine 5'-monophosphate decarboxylase, was cloned from a phage library derived from the lichen Solorina crocea. Phylogenetic analysis and a survey of geographically well-separated specimens were used to verify that the gene represented the fungal component of the lichen. Both coding and upstream sequences of S. crocea pyrG exhibited features typical of fungal genes. A 132-bp intron interrupting the coding region between nucleotides 157 and 288 was confirmed by RT-PCR and sequencing. Transformation of Aspergillus nidulans with S. crocea pyrG, controlled by either its native promoter or the A. nidulans trpC promoter, resulted in uridine-independent strains that exhibited appreciable growth only at 24 degrees C. Southern analysis indicated multiple integrations of S. crocea pyrG. These results demonstrate that heterologous expression may be used to investigate genes from lichens.

Identification of an epitope common to genogroup 1 "norwalk-like viruses"

A panel of 10 monoclonal antibodies (MAbs) to recombinant Norwalk virus (NV) capsid protein were tested in competition enzyme-linked immunosorbent assays. Patterns of competition indicated that these MAbs recognize six to eight epitopes covering five nonoverlapping regions of the capsid protein. A single epitope, recognized by NV MAbs NV3901, NV3912, and NV2461 was found to occur in the majority of genogroup 1 (G1) but not genogroup 2 (G2) "Norwalk-like viruses" (NLVs). This observation supports the subdivision of human NLVs into two genogroups and provides an assay for the rapid identification of G1 NLVs in fecal specimens.

Skin CD4+ T cells produce interferon-gamma in vitro in response to streptococcal antigens in chronic plaque psoriasis

Recently, we have demonstrated that group A streptococcal antigen reactive T cells are present in the skin lesions of chronic plaque psoriasis. To determine the cytokine profile (interferon-gamma, interleukin-4 and interleukin-10) of these T cells in response to streptococcal antigens, T cell lines were cultured from untreated lesional skin of 13 patients with chronic plaque psoriasis and 12 patients with other inflammatory skin diseases. T cell lines were incubated with or without a sonicated heat-killed mixture of group A streptococcal isolates for 18 h in the presence of a transport inhibitor, stained for surface CD4 or CD8 and intracellular cytokine expression, and analyzed by flow cytometry. Psoriatic T cell lines were grown from 10 of 13 patients and were predominately CD4+ (64%-85%) with 10%-32% CD8+ T cells. Variable numbers of CD4+ T cells produced interferon-gamma (0.8%-35%, median 13.9) in eight of 10 T cell lines (p < 0.02). In contrast, CD4+ T cells in five of 12 T cell lines obtained from disease controls did not produce or produced minimal interferon-gamma in response to group A streptococcal isolates; this was significantly different from the psoriatic T cell lines (p < 0.05). Small numbers of interleukin-10 positive (0.8%-1.3%) and interleukin-4 positive (2.1%-2.5%) CD4+ T cells induced by group A streptococcal isolates were also present in two out of five and three out of five psoriatic T cell lines, respectively. This was significantly less in each case than the numbers of CD4+/interferon-gamma+ T cells (p < 0.05). Cytokine-positive CD8+ T cells were rarely observed. These findings demonstrate that a subpopulation of CD4+ T cells in chronic plaque psoriasis skin lesions produces interferon-gamma in response to streptococcal antigens and may be relevant to the pathogenesis of psoriasis.

Genomic characterisation of the large segment of a rabbit picobirnavirus and comparison with the atypical picobirnavirus of Cryptosporidium parvum

The 2362 base pair sequence of the larger of the two double stranded RNA genome segments of a rabbit strain of picobirnavirus (PBV) has a major open reading frame (ORF) of 591 amino acids and two smaller ORFs of 55 and 155 amino acids. A clone of the segment did not hybridise with other viral bisegmented ds RNAs from faecal samples. There is no relationship in sequence or organisation between this PBV sequence and the bisegmented dsRNAs found associated with Cryptosporidium parvum. This suggests that there are at least two distinct classes of bisegmented dsRNA viruses or viral-like agents in faeces.