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Biomedical subjects

A MacGregor

Publications and source records attributed to A MacGregor.

At least 37 records · Page 2Linked to original sources
PubMed1998

Chromatographic removal and heat inactivation of hepatitis B virus during the manufacture of human albumin.

The purpose of the present study was to examine the efficacy of the chromatographic and pasteurization steps, employed in the manufacture of human albumin, in the removal and/or inactivation of hepatitis B virus (HBV). Most human albumins manufactured today are prepared from donor plasma by fractionation methods that use precipitation with cold ethanol. CSL Limited, an Australian biopharmaceutical company, has recently converted its method of manufacture for albumin from a traditional Cohn fractionation method to a method employing chromatographic techniques. A step-by-step validation of virus removal and inactivation was performed on this manufacturing process, which includes a DEAE-Sepharose(R) and CM-Sepharose(R) Fast Flow ion-exchange step, a Sephacryl(R) S200 High-Resolution gel-filtration step and a bulk pasteurization step where product is held at 60 degreesC for 10 h. HBV partitioning experiments were conducted on scaled-down chromatographic columns with hepatitis B surface antigen (HBsAg) as a marker, whereas the HBV model virus, duck HBV, was used to study the inactivation kinetics during pasteurization. Reductions for HBsAg through the three chromatographic steps resulted in a total log10 decrease of 1.5 log10, whereas more than 6.5 log10 decrease in duck HBV in Albumex(R)5 was achieved during pasteurization.

Animals↗
PubMed1997

Genetic bias in immune responses to a cassette shared by different microorganisms in patients with rheumatoid arthritis.

Rheumatoid arthritis (RA) is an autoimmune disease associated with HLA-DRbeta1 alleles which contain the QKRAA amino acid sequence in their third hypervariable region(s). The QKRAA sequence is also expressed by several human pathogens. We have shown previously that an Escherichia coli peptide encompassing QKRAA is a target of immune responses in RA patients. Here we address two questions: first, whether QKRAA may function as an "immunological cassette" with similar, RA-associated, immunogenic properties when expressed by other common human pathogens; and second, what is the influence of genetic background in the generation of these responses. We find that early RA patients have enhanced humoral and cellular immune responses to Epstein-Barr virus and Brucella ovis and Lactobacillus lactis antigens which contain the QKRAA sequence. These results suggest that the QKRAA sequence is an antigenic epitope on several different microbial proteins, and that RA patients recognize the immunological cassette on different backgrounds. ANOVA of immune responses to "shared epitope" antigens in monozygotic twin couples shows that, despite significantly elevated responses in affected individuals, a similarity between pairs is retained, thus suggesting a role played either by hereditary or shared environmental factors in the genesis or maintenance of these responses.

Antigen Presentation↗
PubMed1997

The removal of model viruses, poliovirus type 1 and canine parvovirus, during the purification of human albumin using ion-exchange chromatographic procedures.

The manufacturing process for albumin in Australia is based primarily on ion-exchange chromatography. The capacity of ion-exchange matrices to remove non-enveloped viruses (canine parvovirus and poliovirus type 1) was assessed using a scaled-down chromatographic process which was shown to yield product meeting purity criteria set for the manufacturing process. Poliovirus type 1 and canine parvovirus were added at one tenth the volume of desalted and delipidated Supernatant II + III produced by traditional Cohn Fractionation from human plasma before the material was applied to DEAE and CM ion-exchangers connected in series. Samples were taken at equilibration, wash, elution and regeneration steps and the log clearance and reduction of the viruses calculated. The mean clearance and reduction factors for viral load of poliovirus type 1 were 5.3 logs and 3.2 logs, respectively and 1.8 logs and 1.8 logs for canine parvovirus.

Animals↗
PubMed1995

Genetic epidemiology of rheumatoid disease.

The aetiology of rheumatoid arthritis (RA) has both genetic and environmental origins. However, the relationship of these with each other and with RA disease is complicated as both genes and environment may be protective or render individuals susceptible. Diagnostic certainty and disease heterogeneity have posed serious hurdles for investigating RA. Patients with similar disease phenotypes may have different aetiologies and it may now be more appropriate to investigate genetic susceptibility with respect to disease process or characteristic immunopathology. Disease concordance studies have been a classical approach to estimating the upper threshold of the genetic contribution to RA and recent studies have approximately halved the much quoted figure of 32% reported by Lawrence for RA concordance in monozygotic twins. However, the interpretation of twin data has to be treated with caution as MZ twins can differ in terms of somatic rearrangement/mutation of immunoglobulin and T cell receptor genes, X chromosome inactivation in females, genomic imprinting and in utero immune relationship. Calculations based on heritability put the genetic component in RA much higher. HLA is an important genetic factor in RA and risk is thought to be associated with a consensus sequence of amino acids within the third hypervariable region of certain DRB1 alleles. It is now clear that HLA is not particularly associated with onset of synovitis but is more associated with progression and severity of the disease process. The HLA-DRB1*0401/0404 genotype is particularly associated with severe, erosive and seropositive RA. Clear differences in RA susceptibility exist between males and females and this may be attributed to hormonal status. Males have a higher threshold requirement for developing RA and this may explain why RA in males is more associated with HLA risk alleles. We have now reached a critical time for the investigation of RA aetio-pathology. Recent advances in molecular biology and automated microsatellite gene scanning technology are making it possible to map disease susceptibility genes over the whole genome in common disorders such as RA. This will require large numbers of well characterised multiplex affected families. It is anticipated that some of the genes identified will fit in with our current concepts of which inflammatory and immune processes are pathologically important in RA. However others may be a major surprise.

Arthritis, Rheumatoid↗
PubMed1995

HLA-DRB1*0401/0404 genotype and rheumatoid arthritis: increased association in men, young age at onset, and disease severity.

OBJECTIVE: To confirm the reported strong association between the HLA-DRB1*0401/0404 genotype and susceptibility to rheumatoid arthritis (RA), and to investigate the influence of sex, age at disease onset, and variables of disease severity on the strength of this association. METHODS: A case control design was adopted comparing the frequency of specific HLA-DRB1 genotypes between 201 Caucasian patients with RA and 139 controls. HLA typing was performed using a polymerase chain reaction based oligonucleotide approach with HLA-DR4 subtyping using an amplification refractory mutation system RFLP technique. RESULTS: The risk of RA in those carrying a single shared epitope (SE) allele was 4 times, and in those carrying 2 SE alleles, 8 times that in the SE negative individuals. This increase was highest in individuals carrying 2 different SE alleles, with the risk in *0401/*0404 cases being 26 times higher. This genotype was associated with a 90-fold increased risk in men and this was more than doubled when age at disease onset was below 30. In all patients with RA, this genotype was associated with a substantially increased risk of being rheumatoid factor positive and having subcutaneous nodules and/or radiological erosion. CONCLUSION: Possession of the HLA-DRB1*0401/*0404 genotype carries a substantially high risk for RA development specifically in its more severe forms. The risks are particularly increased in young men.

Adolescent↗
PubMed1995

HLA-DPB1*0201 is associated with particular clinical features of rheumatoid arthritis.

AIMS: to determine the effect of HLA-DPB1 status on rheumatoid arthritis (RA) susceptibility and disease expression. METHODS: HLA-DPB1 alleles were identified in 158 RA patients and 106 controls using PCR-sequence specific oligonucleotide probing. HLA-DPB1 allele frequencies were compared between patient and control groups and the strength of associations assessed using odds ratios and with 95% confidence intervals (CI). Associations observed in the total RA group were confirmed using a relative predispositional effect (RPE) analysis. RESULTS: an association between DPB1*0201 and RA was observed (OR 1.8, 95% CI 1.0-3.4). By contrast, negative associations were found with DPB1*0301 (OR 0.5, 95% CI 0.3-1.0) and DPB1*1101 (OR 0.06, 95% CI 0.001-0.5). These associations were confirmed using RPE analysis. On further analysis the increase in DPB1*0201 and decrease in DPB1*0301 frequencies in RA was found to be independent of DR4 status. The association of DPB1*0201 with RA appears to be most pronounced in male patients (OR 3.3, 95% CI 1.3-8.3), seronegative patients (OR 2.6, 95% CI 0.9-7.3) those with non-erosive disease (OR 2.6, 95% CI 0.9-7.3) or in patients with high titre antinuclear antibodies (OR 2.4, 95% CI 0.8-7.1). CONCLUSIONS: HLA-DPB1 alleles may be associated with the pattern of disease expression in certain RA patients and in some cases confer protection against disease.

Adult↗
PubMed1994

P-glycoprotein expression on acute myeloid leukaemia blast cells at diagnosis predicts response to chemotherapy and survival.

P-glycoprotein (Pgp) expression, which is associated with the multi-drug resistance (MDR) phenotype, has been reported to be a useful predictor of treatment outcome in acute leukaemia. We have examined the expression of Pgp on acute myeloid leukaemia (AML) cells in 54 newly diagnosed patients, using a novel streptavidin-biotin complex (ABC) technique. 55% of patients at diagnosis were positive for Pgp with JSB-1, a monoclonal antibody that binds to an internal epitope of Pgp. All patients received intensive induction chemotherapy. Post-remission treatment consisted of further chemotherapy +/- bone marrow transplantation. Complete remission (CR) rates were significantly lower in the Pgp positive group than in the Pgp negative group (60% v 92%; P = 0.02). The overall survival for Pgp-positive patients was significantly shorter (329 v 534d, P = 0.004), disease-free survival was also reduced but the difference was not statistically significant (median 277 v 522d, P = 0.16). In this study CD34 expression was not predictive of response to chemotherapy nor was it associated with Pgp expression. Our results confirm the prognostic value of Pgp expression in AML at diagnosis and we suggest that Pgp could be a useful therapeutic target for reversing multi-drug resistance. Furthermore, our simple and sensitive method of detecting Pgp should enable widespread testing to be performed.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1993

Low prevalence of rheumatoid arthritis in the urbanized Chinese of Hong Kong.

OBJECTIVE: To establish the prevalence of rheumatoid arthritis (RA) in the urbanized Chinese of Hong Kong. METHODS: 2000 adults in 2 housing blocks were screened using a structured interview. Those who screened positive had an examination, rheumatoid factor analysis and radiographs taken. Subjects were classified using the Rome, New York and 1987 ACR criteria (modified and unmodified) for RA. RESULTS: The prevalence of RA, using the modified 1987 ACR criteria, was 0.35%. This is significantly lower than published data for European Caucasians (standardized morbidity ratio = 0.27; 95% CI 0.09-0.63). CONCLUSION: RA is rare in urbanized Chinese.

Adolescent↗
PubMed1991

Development of an enzyme immunoassay for the detection of Clostridium novyi type B alpha toxin.

Clostridium novyi type B alpha toxin was purified to homogeneity and shown to have a molecular weight of 200 kD by SDS polyacrylamide gel electrophoresis. The toxin was toxoided and used to produce a pair of non-interfering monoclonal antibodies. Their specificity was confirmed by immunoblotting and bioassay. The monoclonal antibodies were used to develop an enzyme immunoassay which was more sensitive than bioassay, and permitted less than 1 ng/ml toxin to be detected in a rapid 10 min assay format. Use of the assay can eliminate the requirement for in vivo testing of novyi toxin and toxoid, provided measurements of biological activity are not required. Because of its speed and sensitivity, the assay can be used to monitor toxin production during fermentation and as an alternative to bioassay to measure antigen content during toxoiding and vaccine formulation.

Animals↗
PubMed1985

Detection of hepatitis A virus and antibody by solid-phase radioimmunoassay and enzyme-linked immunosorbent assay with monoclonal antibodies.

Monoclonal antibodies (K3-2F2 and K3-4C8) raised against hepatitis A virus were used to develop a solid-phase radioimmunoassay and enzyme-linked immunosorbent assay for the detection of hepatitis A virus and antibody. Assays with this pair of monoclonal antibodies were compared in parallel with similarly constructed solid-phase radioimmunoassays and enzyme-linked immunosorbent assays in which human polyclonal serum was used. The monoclonal antibody assay proved to be more sensitive for the detection of hepatitis A virus from fecal specimens as well as for anti-hepatitis A virus immunoglobulin G (IgG) and IgM in sera.

Antibodies, Monoclonal↗
PubMed1983

Monoclonal antibodies against hepatitis A virus.

Three monoclonal antibodies (K2-4F2, K3-2F2, and K3-4C8) of the immunoglobulin G2a class were raised against hepatitis A virus. The specificity of these antibodies was confirmed by immune electron microscopy, solid-phase radioimmunoassay, and in vitro neutralization in cell culture. Binding studies suggested that they all recognize closely related antigenic determinants. These monoclonal antibodies should prove to be of great value as diagnostic and research reagents.

Animals↗
PubMed1983

Monoclonal hybridoma antibodies against human IgE and their use in a rapid and sensitive enzyme immunoassay for the semiquantitative assessment of total IgE levels in human blood.

A simple semiquantitative enzyme immunoassay (EIA) for the rapid estimation of IgE levels in specimens of human blood, plasma or serum is described. The test requires little labour input and does not require highly trained personnel or instrumentation. By using two monoclonal antibodies of different anti-IgE specificities it is possible, with a single incubation of 20 min at ambient temperature, to detect elevated IgE levels (greater than or equal to 333 IU/ml) within a total test time of 25 min, and low levels of IgE (less than or equal to 10 IU/ml) within 35 min. For diagnosis of elevated/normal IgE levels only, a single incubation of 10 min. at ambient temperature may be used with a total test time of less than 20 min. The EIA system utilizes glass capillary tubes and urease-labelled antibodies, a system that has proven satisfactory in other applications.

Animals↗
PubMed1982

An investigation of the use of urease-antibody conjugates in enzyme immunoassays.

The development of urease (E.C.3.5.1.5) as a label for enzyme immunoassay (EIA) procedures is described and the use of such conjugates illustrated with examples. Urease catalyzes the hydrolysis of urea to carbon dioxide and ammonia. The production of ammonia may be detected readily by a pH shift which we have found best indicated by the vivid colour change (yellow to purple) of bromocresol purple incorporated in the substrate solution. This enzyme-substrate system offers a number of important advantages. The substrate in aqueous solution is stable, titration end points are sharp and readily visible and the enzyme is not inhibited by sodium azide. Thus, test reagents may be prepared with this preservative and stored ready to use. Urease of high specific activity is commercially available and because it does not occur in mammalian tissues, it is suitable for use in EIA tests to detect cell-associated antigens and their antibodies. Finally, the enzyme reaction may be stopped by the addition of organomercurial preservatives, thus allowing storage of developed tests for later examination.

Alkaline Phosphatase↗