Evaluation of an antigen capture ELISA based on recombinant mexico virus capsid protein

BACKGROUND

The diagnosis of gastrointestinal infections caused by small round structured viruses (SRSV) has relied upon electron microscopy and antigen/antibody assays based on Norwalk virus. We investigated cases of gastroenteritis associated with SRSVs employing a new sandwich enzyme-linked immunosorbent assay (ELISA) using hyperimmune animal anti-sera against recombinant Mexico virus capsid protein (rMXV).

STUDY DESIGN

One hundred and thirty-five specimens from 86 episodes of gastroenteritis associated with SRSVs, collected in the UK between October 1993 and September 1994, were tested in the rMXV assay.

RESULTS

Forty-seven (35%) specimens from 35 of 86 (41%) episodes were positive in the rMXV ELISA and these could further be divided into high and low reactors. Sequencing of a 266-base region of the RNA polymerase gene revealed that strains highly reactive in the rMXV assay demonstrated a high degree of similarity to MXV (97-99% at the nucleotide level), whereas low-reactive strains consist of Mexico-like strains and a heterogeneous group of viruses exhibiting 70-75% similarity to MXV.

CONCLUSION

Our results indicate that the rMXV ELISA is predominantly a type specific assay, although some cross reactivity with other genogroup 2 SRSVs was observed. MXV was responsible for 26% of SRSV-associated gastrointestinal infections investigated in the UK during one year's surveillance.

Diagnosis of parvovirus B19 infection by detection of specific immunoglobulin M antibody in saliva

Serum and saliva samples were simultaneously collected from patients with B19 infection. Specimens were collected in a period of 1 to 18 days after the onset of symptoms. Saliva samples were collected with a commercial device, OraSure. The quality of these samples was evaluated by determining the concentration of total immunoglobulin G (IgG) by an enzyme immunoassay. The concentration of IgG in these samples ranged from 4.8 to > 250 mg/liter. B19 infection was confirmed for 20 patients by testing sera in a 1: 100 dilution by an IgM capture enzyme immunoassay (MACEIA) and an IgM capture hemadherence test (MACHAT). Saliva samples from these IgM-positive patients were tested neat by MACEIA and MACHAT. IgM could be detected in 11 of 20 (55%) samples by MACEIA and in 15 of 18 (83%) samples by MACHAT. Serum and saliva samples from a further 17 patients with rash were also tested. All of these specimens were unreactive by both assays. These results show that saliva may be a convenient alternative to serum for the diagnosis of recent B19 infection.

Detection of small round structured viruses in shellfish by reverse transcription-PCR

We describe the application of a previously developed sample extraction procedure to the detection of small round structured viruses (SRSVs) in shellfish. Initial seeding experiments showed that PCR inhibitor removal and virus recoveries were comparable to those in previous studies with poliovirus. Shellfish from a range of sewage-contaminated sites were then tested for the presence of SRSVs by using broadly reactive PCR primers followed by Southern blotting with internal probe sites. Positive results were obtained from 5 of 31 field samples tested. Four of these positive samples were from highly polluted sites. PCR product sequence analysis confirmed their identity as SRSV and showed sequence diversity compared with virus controls, suggesting that the results were not a consequence of PCR cross-contamination. Finally, shellfish associated with four separate outbreaks of viral gastroenteritis were tested by PCR and Southern blot for the presence of SRSVs. All outbreak samples tested gave positive results. As far as we are aware, this is the first demonstration of the detection in environmentally contaminated shellfish of the SRSVs responsible for human gastroenteritis. This development may help contribute to the further development of public health controls for molluscan shellfish.

Broadly reactive reverse transcriptase polymerase chain reaction for the diagnosis of SRSV-associated gastroenteritis

A limitation to date of reverse transcriptase polymerase chain reactions (RT-PCRs) for the detection of small, round structured viruses (SRSVs) has been that they have detected only a narrow range of SRSVs due to the marked genomic diversity among strains. A total of 331 faecal samples collected from 136 separate incidents of gastroenteritis occurring in the UK between 1992 and 1994 were examined by RT-PCR employing a single primer pair (N1/E3). SRSV RNA was detected in samples from 93 of 101 (91%) incidents shown to be SRSV-associated by electron microscopy (EM) and in 5 of 35 (14%) SRSV-negative incidents. Amplification products were tested by Southern blot hybridisation with a pool of four digoxigenin (DIG)-labelled oligonucleotides derived from genomic sequence data of SRSV SPIEM types UK 1 to 4. Products from approximately 5% of amplified strains did not hybridise. The N1/E3 primer pair were shown to be SRSV-specific by their failure to amplify other faecal viruses including other human caliciviruses with typical calicivirus morphology. Hybridisation of PCR products with the individual oligonucleotides relating to SRSV SPIEM types UK 1-4 was investigated: 1 of 60 (1.7%) reacted with the UK1 probe, 2/60 (3.4%) reacted with the UK2 probe, 51/60 (85%) with the UK3 probe, and 27/60 (45%) reacted with the UK4 probe. All PCR products that hybridised with the UK4 probe hybridised with the UK3 probe; 6 (10%) failed to hybridise. Identification of this primer pair facilitates routine diagnosis of SRSV infection by RT-PCR and offers the potential for direct detection in food and environmental samples.

Felonious sex crime: the possibility of unilateral cerebral irradiation for the offenders

Some felonious sex crimes might result from compulsions that the perpetrator finds impossible to control. Under judicial systems derived from British law, the court should be extraordinarily careful in mandating any medical procedure. However, if a rapist or child molester voluntarily asks a physician for help, then medical ethics might allow destruction of part of the patient's brain for the purpose of controlling compulsive behaviour. The part of the human brain primarily associated with volition might be near the anterior cingulate sulcus. Could unilateral irradiation of an area near the anterior cingulate sulcus partially destroy the patient's volition? By leaving intact the patient's will based on language and by partially destroying the patient's will based on intuition, could the physician diminish the patient's will to commit felonious sex crimes? Would some patients reject chemical castration but accept unilateral irradiation of an area near the anterior cingulate sulcus?

Complete nucleotide sequence of the herpesvirus simiae glycoprotein G gene and its expression as an immunogenic fusion protein in bacteria

The nucleotide sequence of a 2384 bp portion within the unique short (Us) region of the herpesvirus simiae (simian herpes B virus; SHBV) genome is presented. A partial and a complete open reading frame (ORF) were found within this nucleotide sequence. The partial ORF encodes the C terminus (147 amino acids) of a protein kinase which is highly conserved in the herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2) and simian agent 8 (SA8) Us regions. The complete ORF is located 3' to the partial ORF within the 2384 bp sequence and encodes a 593 amino acid glycoprotein which appears to be closely related to the SA8 glycoprotein G (gG), but shares little amino acid similarity with gG of HSV-1 and -2. However, the complete ORF shares certain features conserved among most alphaherpesvirus gGs, notably three highly conserved cysteine residues and an adjacent N-glycosylation site. Therefore, it was concluded that this complete ORF encodes the SHBV gG. The 358 amino acid C-terminal portion of SHBV gG was expressed in Escherichia coli as a fusion protein and this was detected by immunoblotting with sera from cynomolgus monkeys which were either experimentally or naturally infected with SHBV. The purified fusion protein was inoculated into rabbits to raise an antiserum which recognized a number of apparently SHBV gG-specific protein bands in extracts from SHBV-infected simian cells.

Monoclonal antibody blocking tests for the detection of HSV-1- and HSV-2-specific humoral responses: comparison with western blot assay

Monoclonal antibody blocking radioimmunoassays (MAb block RIAs) which detect specific humoral responses to each of the two human herpes simplex virus (HSV) types are described. RIAs were compared with Western blot assay (WBA) in a blind study of 64 sera obtained from clinically well-documented cases of genital herpes. WBA and MAb block RIA each detected HSV-1 antibodies in 16/17 (94%) sera from confirmed HSV-1 genital infections (first episodes and recurrent infections). Detection of HSV-2 antibody in 21 sera from HSV-2 first episodes was more effective by WBA which identified homologous antibody in 19 (96%), whereas MAb block RIA detected HSV-2 antibody in 16 (76%). HSV-2 antibody was detected in 24/25 (96%) sera from recurrent HSV-2 infections by WBA and by MAb block RIA, the highest degree of concordance for both methods. In addition, the MAb block RIA may be more effective in detecting the presence of HSV-1 antibody in sera from recurrent HSV-2 cases. Prevalence of HSV-1 and HSV-2 antibody was measured by the MAb block RIAs in 3 UK human study populations which consisted of 100 children/young adolescents, 104 adult blood donors and 80 genito-urinary medicine clinic attenders.

The JC virus antibody response in serum and cerebrospinal fluid in progressive multifocal leucoencephalopathy

BACKGROUND

A clinical diagnosis of progressive multifocal leucoencephalopathy (PML) can be confirmed by histological or virological examination of brain material. Whilst a less invasive method is provided by the detection of JC DNA in cerebrospinal fluid (CSF), very few studies have been done to assess the value of JC virus (JCV) serology in PML diagnosis.

OBJECTIVES

To study the JCV antibody response in the serum and CSF of PML patients.

STUDY DESIGN

A retrospective study was done using haemagglutination inhibition (HI), M-antibody capture radioimmunoassay (MACRIA) and JC-specific oligoclonal IgG banding on one or more sera and/or CSFs from 28 confirmed PML patients. Seventy-one serum and CSF samples were tested from patients with memory loss or dementia as a control group.

RESULTS

Twenty-seven PML patients (96%) had detectable JCV HI antibody in the serum, with titres ranging from 1 : 10 to > 1 : 20480, compared to 48 (68%) of the controls (P = <0.005). JCV IgM antibody was detected in the serum of 12/22 (55%) PML patients. JCV HI antibody was detected in the CSF in 12 of 18 (67%) PML patients, antibody index measurements being used to control for a possible breakdown of the blood-brain barrier. Intrathecal JCV antibody was not found in any control patient. Locally produced JCV-specific IgG bands were detected in the CSF of 7 PML patients tested, confirming the intrathecal origin and specificity of the HI antibody.

CONCLUSIONS

The presence of intrathecal JCV antibody indicates active central nervous system infection with JC virus, and provides a useful diagnostic test for PML, with a sensitivity of 67% and a specificity of 100%. The absence of serum JCV antibody nearly always excludes a diagnosis of PML, but the titre of antibody, IgG or IgM, correlates with the underlying condition rather than the development of neurological symptoms.

Werner syndrome and genetic obesity: speculation

Werner syndrome (WS) is a rare autosomal recessive disease with poor growth, premature aging, scleroderma-like skin changes, endocrine abnormalities, and deficiencies of adipose tissue. Could there be a genetic obesity syndrome which offers an instructive contrast to at least one form of WS? At least one form of WS might result from an enzyme defect that causes hypertriglyceridemia, hyperinsulinism, and hyperglucagonism; the defective enzyme might play a key role in the utilization of tryptophan, riboflavin (vitamin B2), or other vitamins or in the synthesis of prostaglandins that inhibit insulin secretion. At least one form of genetic obesity might result from an enzyme defect that causes hypotriglyceridemia and hyperinsulinism without hyperglucagonism; the defective enzyme might be unable to bind properly to a product that inhibits some step in the process of conversion of free fatty acid (FFA) CoA into ketoacids.

Detection of a picobirnavirus associated with Cryptosporidium positive stools from humans

A picobirnavirus with an atypical genome profile was detected by polyacrylamide gel electrophoresis (PAGE) in 37% (20/54) of human faecal samples also containing oocysts of Cryptosporidium typical of C. parvum. This virus shares many of the characteristics of the previously described picobirnaviruses, but has a significantly smaller genome (1.75 and 1.55 Kbp).

Prevalence and distribution of BK virus subtypes in healthy people and immunocompromised patients detected by PCR-restriction enzyme analysis

BACKGROUND

Four antigenic subtypes of BK virus (BKV) have recently been characterised by both genomic subtyping and serological reactivity.

OBJECTIVES

To study the prevalence and distribution of subtypes of BKV in different groups of patients.

STUDY DESIGN

Urine specimens were collected from 33 bone marrow transplant (BMT) recipients, from 101 HIV-infected patients, from 15 children aged 2-5 and from 40 pregnant women were tested for BKV DNA by polymerase chain reaction (PCR) and subtyped using a PCR-sequencing (PCR-S) and a modified PCR-restriction enzyme analysis (PCR-RE) methods.

RESULTS

BKV DNA was detected in 12/18 (67%) of BMT patients with haematuria and 5/15 (33%) without. Overall BKV DNA was detected in 45% of HIV-infected patients, the prevalence of BKV DNA increased with greater immunosuppression as defined by CD4 cell counts. BKV DNA was detected in urine samples from 27% of children and 47% of pregnant women. Four stable BKV subtypes were detected in these patient groups. Dual infections with more than one subtype were identified in urine samples from HIV-infected patients, children and pregnant women but not in the samples from bone marrow recipients.

CONCLUSION

This study has confirmed the high prevalence of BKV infection in immunocompromised patients and suggests that stable BKV subtypes with conserved sequences are circulating in the human population. The techniques of PCR-S and PCR-RE described in this study are sufficiently sensitive for subtyping BKV direct from clinical specimens.

Detection and characterisation of bisegmented double-stranded RNA viruses (picobirnaviruses) in human faecal specimens

The prevalence of picobirnaviruses (PBVs) in human stools was investigated by polyacrylamide gel electrophoresis (PAGE) analysis of 832 faecal specimens collected between 1982 and 1993 from patients in various clinical groups. Similar prevalences (9-13%) were detected in patients with or without gastroenteritis and throughout the age range of 3 to > 65 years. Two methods for the extraction of nucleic acid, a phenol/chloroform method and a guanidinium thiocynate (GTC)/silica method, were compared. Detection of PBVs by PAGE was three times more sensitive following RNA extraction by the GTC/silica method. Characterisation of three strains was carried out. Segment sizes ranged from 1.625 to 1.95 kilo base pairs (Kbp) and 2.2 to 2.5 Kbp for the fast and slow migrating bands, respectively. The nuclic acid was shown to be double-stranded RNA (dsRNA) by nuclease digestion. PBV-like particles were detected by electron microscopy in two PAGE-positive stools. Virion diameters ranged from 35 to 41 nm and a buoyant density of 1.38-1.4 g/ml in caesium chloride (CsCl) was demonstrated. These findings suggest that PBVs are widespread in humans in the United Kingdom. However, no disease association could be demonstrated.

Salivary antibody detection in epidemiological surveys: a pilot study after a mass vaccination campaign against rubella in São Paulo, Brazil

The sensitivity and specificity of salivary rubella antibody detection was investigated using samples collected from 301 children after a mass vaccination campaign in the state of São Paulo, Brazil. Saliva samples were collected by 2 different methods: directly dribbling into a container or using a commercial collecting device. Corresponding finger-prick blood samples were collected on filter paper. Rubella specific immunoglobulin G (IgG) was measured in saliva by antibody capture radioimmunoassay and in blood samples by indirect enzyme-linked immunosorbent assay. The detection of salivary rubella specific IgG showed good correlation with the detection of rubella antibody in the blood samples. For both collecting techniques the predictive value for a positive saliva test was > 99% compared with the results from the blood tests. However, the predictive value for a negative saliva test was only 58.3% for a dribbled sample, compared to 100% for saliva collected using the commercial device. Moreover, collecting saliva by dribbling from children less than 4 years old was difficult. The detection of rubella specific IgG in saliva collected using a commercial device proved to be sensitive and specific in this epidemiological study, encouraging its more widespread application as a means of surveillance after mass vaccination.

IgM antibody capture haemadherence test (MACHAT) for the detection of measles specific IgM

An antibody capture haemadherence test (MACHAT) for detecting measles-specific IgM is described. The assay is based on the antibody capture principle with rhesus monkey erythrocytes as detector system in place of labelled antisera. MACHAT was compared with a commercial indirect enzyme immunoassay (EIA) for measles-specific IgM using 382 sera from patients notified as measles. There was good agreement between the two tests; 106 sera were found to contain measles IgM by both tests, 7 further sera were positive only in the commercial EIA and 9 only in MACHAT. One sera gave an equivocal result in MACHAT and another in the commercial EIA. Twelve of the 18 sera with discrepant results were also tested by MACRIA; in 7 MACRIA gave the same results as MACHAT, in 3 the MACRIA results agreed with the commercial test and in 2 the MACRIA results were equivocal. Specificity was established by a lack of MACHAT reactivity in sera collected from blood donors (n = 83) and from cases of recent rubella, dengue and parvovirus B19 infection (n = 51). The MACHAT is a simple, cheap test that can be read by eye and is suitable for measles surveillance programmes in the developing world.

Early diagnosis of Lassa fever by reverse transcription-PCR

We developed a method based on a coupled reverse transcription-PCR (RT-PCR) for the detection of Lassa virus using primers specific for regions of the S RNA segment which are well conserved between isolates from Sierra Leone, Liberia, and Nigeria. The specificity of the assay was confirmed by Southern blotting with a chemiluminescent probe. The assay was able to detect 1 to 10 copies of a plasmid or an RNA transcript containing the target sequence. There was complete concordance between RT-PCR and virus culture for the detection of Lassa virus in a set of 29 positive and 32 negative serum samples obtained on admission to the hospital from patients suspected of having Lassa fever in Sierra Leone. Specificity was confirmed by the failure of amplification of specific products from serum samples collected from 129 healthy blood donors in Sierra Leone or from tissue culture supernatants from cells infected with related arenaviruses (Mopeia, lymphocytic choriomeningitis, Tacaribe, and Pichinde viruses). Sequential serum samples from 29 hospitalized patients confirmed to have Lassa fever were tested by RT-PCR and for Lassa virus-specific antibodies by indirect immunofluorescence (IF). RT-PCR detected virus RNA in 79% of the patients at the time of admission, comparing favorably with IF, which detected antibodies in only 21% of the patients. Lassa virus RNA was detected by RT-PCR in all 29 patients by the third day of admission, whereas antibody was detectable by IF in only 52% of the patients. These results point to an important role for RT-PCR in the management of suspected cases of Lassa fever.

Genomic diversity of small round structured viruses in the United Kingdom

Fifty-two faecal specimens collected in the United Kingdom between 1986 and 1992, which contained small round structured virus (SRSV) particles, were tested by reverse transcriptase polymerase chain reaction assays using two primer pairs derived from sequences of Snow Mountain Agent and Norwalk virus. There was poor correlation between results obtained with each primer pair. Twenty specimens (38%) gave positive bands with SM51/31 primers and 18 (34%) were positive with SM52/32 primers, with a total of 30 specimens (57.7%) giving amplification products of the expected size with one or both primer pairs. Genomic variation was investigated by sequencing a 266 bp region of the RNA polymerase gene from nine strains which had been antigenically typed by solid phase immune electron microscopy (SPIEM). RNA sequence identities ranged from 53 to 99%. Three genomic groups were suggested by phylogenic analysis, the first of which contained Norwalk virus, Southampton virus, and strains typed by SPIEM as SRSV UK2. The second contained Snow Mountain agent and strains typed as either SRSV UK3 or UK4. The third contained strains typed as SRSV UK1 and strains untypeable by SPIEM. Some correlation was demonstrated when antigen typing by SPIEM and phylogenic grouping based on sequence data were compared.

Amyotrophic lateral sclerosis: hypothetical pathogenesis

A hypothetical pathogenesis for a typical case of amyotrophic lateral sclerosis (ALS) follows from opinions of Rowland and results of neuroscientists at Baylor. ALS might typically result from an autoimmune disorder that causes IgG to enhance release of acetylcholine (ACh) from axon terminals. Motor neuron overactivity associated with fasciculation might result from enhanced release of ACh which is taken up by nicotinic ACh receptors. Increased levels of intracellular calcium ions might result from motor neuron overactivity associated with fasciculation. Neuronal cell degeneration and death might result from increased levels of intracellular calcium ions.

Salivary diagnosis of measles: a study of notified cases in the United Kingdom, 1991-3

OBJECTIVES

To validate a method for salivary diagnosis of measles and to assess the diagnostic accuracy of notified cases of measles.

DESIGN

Blood and saliva samples were collected within 90 days of onset of symptoms from patients clinically diagnosed as having measles and tested for specific IgM by antibody capture radioimmunoassay.

SETTING

17 districts in England and one in southern Ireland during August 1991 to February 1993.

SUBJECTS

236 children and adults with measles notified by a general practitioner.

RESULTS

Specific IgM was detected in serum in only 85 (36%) of the 236 cases. In cases associated with outbreaks and tested within six weeks of onset, 53/57 (93%) of samples were IgM positive, thereby confirming the sensitivity of serum IgM detection as a marker of recent infection. The serological confirmation rate was lower in cases with a documented history of vaccination (13/87; 15%) than in those without (70/149; 47%) and varied with age, being lowest in patients under a year, of whom only 4/36 (11%) were confirmed. Measles specific IgM was detected in 71/77 (92%) of adequate saliva samples collected from patients with serum positive for IgM. In cases where measles was not confirmed, 6/101 had rubella specific IgM and 5/132 had human parvovirus B19 specific IgM detected in serum.

CONCLUSIONS

The existing national surveillance system for measles, which relies on clinically diagnosed cases, lacks the precision required for effective disease control. Saliva is a valid alternative to serum for IgM detection, and salivary diagnosis could play a major role in achieving measles elimination. Rubella and parvovirus B19 seem to be responsible for a minority of incorrectly diagnosed cases of measles in the United Kingdom and other infectious causes of measles-like illness need to be sought.