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Biomedical subjects

D W Brown

Publications and source records attributed to D W Brown.

At least 109 records · Page 6Linked to original sources
PubMed1995

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.

Journal Article↗
PubMed1995

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.

Journal Article↗
PubMed1995

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.

Amino Acid Sequence↗
PubMed1995

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.

Amino Acid Sequence↗
PubMed1994

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.

Adolescent↗
PubMed1994

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.

Adult↗
PubMed1994

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.

Hemadsorption Inhibition Tests↗
PubMed1994

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.

Acetylcholine↗
PubMed1994

Isolation and Characterization of Sexual Spore Pigments from Aspergillus nidulans.

The homothallic ascomycete Aspergillus nidulans produces two types of pigmented spores: conidia and ascospores. The synthesis and localization of the spore pigments is developmentally regulated and occurs in specialized cell types. On the basis of spectroscopic evidence, we propose that the major ascospore pigment of A. nidulans (ascoquinone A) is a novel dimeric hydroxylated anthraquinone. The structure of ascoquinone A, as well as a comparison to model compounds, suggests that it is the product of a polyketide synthase. Previous studies have revealed that the conidial pigments from A. nidulans and a related Aspergillus species (A. parasiticus) also appear to be produced via polymerization of polyketide precursors (D. W. Brown, F. M. Hauser, R. Tommasi, S. Corlett, and J. J. Salvo, Tetrahedron Lett. 34:419-422, 1993; M. E. Mayorga and W. E. Timberlake, Mol. Gen. Genet. 235:205-212, 1992). The structural similarity between the ascospore pigment and the toxic anthraquinone norsolorinic acid, the first stable intermediate in the aflatoxin pathway, suggests an evolutionary relationship between the respective polyketide synthase systems.

Journal Article↗
PubMed1994

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.

Base Sequence↗
PubMed1993

Unfolding of nucleosome cores dramatically changes the distribution of ultraviolet photoproducts in DNA.

Nucleosome core particles undergo a conformational change at ionic strengths below 0.2 mM; the fluorescence anisotropy decay of bound ethidium indicates that under these conditions the particle adopts a highly extended structure. We have measured the distribution of UV-induced DNA damage (primarily cyclobutane-pyrimidine dimers) through a process termed photofootprinting. As the core particle is exposed to ionic strengths below 0.2 mM, the photofootprint pattern changes from that observed for native cores, with a characteristic 10.3 base repeat pattern presumably derived largely from the bending of DNA around the histone octamer, to a more evenly distributed pattern resembling that of free DNA. These results provide clear evidence that the DNA in the core particle at these very low ionic strengths, although still tightly bound to histones, is no longer bent to a significant degree.

Animals↗
PubMed1993

Detection of JC virus DNA in the cerebrospinal fluid of patients with progressive multifocal leukoencephalopathy.

JC virus (JCV) DNA was detected by polymerase chain reaction (PCR) amplification in the cerebrospinal fluid (CSF) of 10 of 13 patients with a diagnosis of progressive multifocal leukoencephalopathy (PML) previously confirmed by histological and virological techniques. It was not found in 42 CSF samples from 41 patients who did not have PML. Four sets of primers were used to amplify polyomavirus DNA. One was from the region of the genome coding the T antigen, a conserved region common to JC and BK viruses. A second set nested to these was used as a confirmatory test in a secondary PCR. The remaining two were from the region of the genome coding VP1, one specific for JCV and the other for BKV. CSF did not inhibit the PCR and preliminary DNA extraction was not considered necessary.

Base Sequence↗
PubMed1993

Detection of measles, mumps, and rubella antibodies in saliva using antibody capture radioimmunoassay.

Antibody capture radioimmunoassays were developed for detecting virus specific IgM (MACRIA) and IgG (GACRIA) to measles, mumps, and rubella and used to investigate saliva as an alternative specimen to serum for diagnosis. Saliva was collected from 63 patients with measles, 19 with mumps, and 150 with rubella, which were all clinically diagnosed and serologically confirmed. Virus specific IgM was detected in 92% of measles, 75% of mumps, and 100% of rubella saliva samples collected during the first week of illness. Between 1 and 5 weeks after onset virus specific IgM was detected in 100% of saliva specimens. After the 5th week the proportion of reactive specimens declined. The specificity of the MACRIA tests was established by testing saliva samples collected from blood donors for measles (88), mumps (88), and rubella IgM (91). All of the saliva specimens tested for measles and rubella specific IgM were unreactive, 1/88 specimens tested for mumps specific IgM contained significant reactivity. Saliva specimens collected from acute cases of MMR were tested in all 3 MACRIAs. A small proportion of saliva samples contained detectable IgM of more than one virus infection. Rubella and measles specific IgG was detected in the saliva of all cases from the 4th or 5th day of illness, respectively. Detection of mumps specific IgG was less successful. We have demonstrated that virus specific IgM can be reliably detected in saliva samples collected from acute cases of measles, mumps, and rubella and identified 1-5 weeks after onset of illness as the optimum time for collection of samples.

Adolescent↗
PubMed1993

Tissue tropism of avian leukosis viruses: analyses for viral DNA and proteins.

Analyses of six tissues from Rous-associated virus type 1-infected chickens have revealed a number of tissue-specific differences in virus synthesis and distribution. Chicks were infected at 1 day of age. Tissue (bursa, thymus, liver, kidney, muscle, and brain) were harvested 1 month later. Each of the tissues contained an average of 1.8 to 4 copies of viral DNA per cell. Most of this DNA was integrated. In brain, about one-third of the total viral DNA was in an unintegrated, linear form. Bursa, thymus, liver, and kidney expressed both Gag and Env proteins. In contrast, muscle expressed more Gag than Env, and brain expressed neither Gag nor Env. Tissues that were producing both Gag and Env contained higher levels of mature virus particles than tissues that were not producing both of these proteins.

Animals↗