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J D Conradie

Publications and source records attributed to J D Conradie.

At least 19 recordsLinked to original sources
PubMed1998

Comparison of seroprevalences of human herpesvirus-6 and -7 in healthy blood donors from nine countries.

BACKGROUND AND OBJECTIVES: The purpose of the study was to register antibody prevalences of HHV-7 in various locations of the world in comparison to the closely related HHV-6. MATERIALS AND METHODS: Sera of healthy blood donors from nine countries in five continents were titered by indirect immunofluorescent assays using HHV-6 infected HSB2 and HHV-7 infected SupT1 cells. RESULTS: Antibody prevalence for HHV-7 is high (75-98%) in practically all countries except for Northern Japan (44%), with no simple correlation to elevated HHV-6 antibody titers. There were regions of low, intermediate and high mean antibody titers against HHV-7 such as 78.5-91.3 for Belgium, Israel, Japan, USA and Australia, 175.4-182.6 for Mexico and Cologne/Germany, and 389.2 for South Africa for which geographic characteristics may be responsible. CONCLUSION: HHV-7, similar to HHV-6, is a widespread human herpesvirus with elevated antibody titers in the healthy human population essentially everywhere. The data warrant further studies to evaluate its possible pathologic potential, preferentially in persons with defective immune responses.

Adolescent↗
PubMed1997

Detection of Maedi-Visna virus antibodies using a single fusion transmembrane-core p25 recombinant protein ELISA and a modified receiver-operating characteristic analysis to determine cut-off values.

The core p25 and transmembrane (TM) genes of Maedi-Visna virus (MVV) were cloned individually into the pGEX-2T expression vector. Both proteins were expressed as a combined fusion protein in frame with glutathione S-transferase (GST). The purified recombinant antigens (GST-TM and GST-TM-p25) were used to develop a MVV ELISA. A preliminary assessment of the diagnostic potential of the recombinant antigens (GST-TM and GST-TM-p25) was made by testing the antigens against 46 seropositive and 46 seronegative sheep and comparing the results with a commercial p25 ELISA kit. A two-graph receiver operating characteristic (TG-ROC) analysis program was used to interpret the data. The GST-TM-p25 ELISA was more sensitive than the commercial assay which is based on the p25 antigen alone and more specific than the GST-TM ELISA.

Animals↗
PubMed1993

Two methods for the introduction of amino groups into agarose-based matrices: their use in immunoaffinity chromatography.

In this study two methods of coupling antibody to Sepharose CL2B are described. They involve the introduction of amino groups either via an amino acid such as glycine or through polyethyleneimine. After introduction of amino groups into the matrices, their activation and simultaneous fixing were accomplished by treatment with glutaraldehyde. Monoclonal antibody raised against von Willebrand factor was used as a model ligand to demonstrate the stability and performance of the affinity supports. Both methods examined in this study resulted in good retention of the antibody's binding capabilities and excellent stability of the derivatized matrices. Leaching of the insolubilized protein was considerably less with the polyethyleneimine-glutaraldehyde than with cyanogen bromide.

Amines↗
PubMed1993

Natural antibodies to avidin in human serum.

Human serum was found to contain natural antibodies to the egg-white glycoprotein avidin. Of 270 samples tested, all contained antibodies to different extents, mainly of the IgG and IgM classes. Anti-avidin antibodies could be isolated by affinity chromatography.

Avidin↗
PubMed1993

Use of jacalin as a solid phase in ABO reverse grouping.

A major problem of using red cells as the solid phase in assay systems is the difficulty to bind them strongly to appropriate surfaces. We report here on a number of lectins of different specificities which were examined for their ability to bind red cells to polystyrene 96-well microtitre plates. The use of the Thomsen-Friedenreich antigen-specific lectins, jacalin, mushroom and Maclura pomifera agglutinin proved the most useful for ABO reverse grouping. Jacalin-coated plates were also compared with plates coated with poly-L-lysine and bovine serum albumin/glutaraldehyde for the binding of erythrocyte membranes and were found to be superior. We also describe the colorimetric detection of the solid phase red cell antibody reaction by using an indicator erythrocyte and peroxidase chromogenic substrate.

ABO Blood-Group System↗
PubMed1990

Prevalence of hepatitis C in South Africa: detection of anti-HCV in recent and stored serum.

The prevalence of anti-HCV was studied in a cohort of 2,072 South Africans. The results were compared in selected recently collected sera and in stored sera. The serum ALT and anti-HBc were also studied as surrogate markers in this population. The following groups were tested: (a) 498 urban, black blood donors (b) 500 white blood donors (c) 500 Asian blood donors (d) 216 rural hospitalized patients (e) 358 rural mineworkers. Sera found positive by the original ELISA were retested, and reproducibly positive tests in rural black men (group d) were confirmed both by recombinant immunoblot assay and by a second ELISA. An anti-HCV prevalence of 1.2%, 0.8%, and 0.6% in urban blacks, Asians, and whites was found. Antibodies to hepatitis B core antigen were found in 42.9%, 3.4%, and 1.2% of black, Asian, and white donors, respectively; 76% of donors positive for anti-HCV were anti-HBc negative. In rural African men, 17% of stored serum samples and 9.2% of recently collected serum samples were positive for anti-HCV. In this cohort 3.84% were positive by all three assays. These results suggest that the prevalence of anti-HCV in low and high-risk South African urban blood donors is comparable to high and low prevalence areas in Europe, the United States, and Japan, but indicates a relatively high degree of exposure to hepatitis C in rural African men. The reactivity of stored, frozen sera in this population requires further investigation. In South African urban blood donors, surrogate marker testing will not expedite HCV screening.

Adult↗
PubMed1989

Differences in the regional prevalence of chronic hepatitis B in southern Africa--implications for vaccination.

Chronic hepatitis B infection is an important cause of cirrhosis and subsequent hepatocellular carcinoma in South Africa. The disease can now be prevented by vaccination, but second-generation genetically engineered vaccines still necessitate planned allotment. We have tested 29,312 black southern African mineworkers for hepatitis B surface antigen (HBsAg) to indirectly ascertain the relative prevalence of hepatitis B infection in diverse linguistic and ethnic groups. The overall prevalence of HBsAg in this cohort of predominantly rural men was 9.9%, but the prevalence in men from different regions varied from 5.5% to 14%. The relative prevalence in 200 magisterial districts was ranked; these percentage prevalences ranged from 0% to 17%. A significantly lower mean prevalence was detected in Southern Sotho subjects than in those from coastal districts (Nguni). Based on these data, we believe that there are perhaps 2 million hepatitis B carriers in South Africa. The collected data in this report could provide a basis for a broad-based vaccine campaign whereby hepatitis B vaccine could be targeted to high-priority districts initially. This strategy could rapidly reduce the critical mass of carriers, and hasten control of the disease.

Adolescent↗
PubMed1989

The use of a monoclonal antibody against alpha-fetoprotein for the radioimmunodetection of hepatocellular carcinoma.

The purpose of this study was to investigate the use of a radiolabeled mouse monoclonal antibody (and its F(ab')2 fragment) against alpha-fetoprotein in the scintigraphic diagnosis of hepatocellular carcinoma. Twenty-six southern African Blacks and one Caucasian with hepatocellular carcinoma and four patients with other malignant tumors of the liver were studied. Although six hepatocellular carcinomas appeared to selectively concentrate alpha-fetoprotein antibody, one of these tumors was not producing alpha-fetoprotein. Moreover, in another 18 patients with alpha-fetoprotein-producing hepatocellular carcinomas, uptake of alpha-fetoprotein antibody was at best only equal to that in nontumorous hepatic tissue, and three hepatocellular carcinomas that were not producing alpha-fetoprotein concentrated the antibody to the same extent as did the alpha-fetoprotein-producing tumors and hepatic tissue. All four tumors other than hepatocellular carcinoma concentrated alpha-fetoprotein antibody as well as did hepatic tissue. These findings suggest that the penetration of hepatocellular carcinomas by alpha-fetoprotein antibody is a passive and nonselective process. This conclusion is supported by an in vitro study in which a non-alpha-fetoprotein-producing hepatic metastasis took up as much radiolabeled alpha-fetoprotein antibody as did three of four alpha-fetoprotein-producing hepatocellular carcinomas. A likely explanation for the failure of alpha-fetoprotein monoclonal antibody to be selectively concentrated by hepatocellular carcinomas is that alpha-fetoprotein is an export protein and is not expressed on the cell membranes of malignant hepatocytes.

Adult↗
PubMed1989

Regional prevalence of hepatitis B, delta, and human immunodeficiency virus infection in southern Africa: a large population survey.

Although hepatitis B infection is endemic in southern Africa, a changing epidemiology of the disease has recently been documented in the region. The authors surveyed migrant southern African male mineworkers during 1986 to establish the prevalence of chronic hepatitis B and D (delta) infection in their areas of origin. Hepatitis B surface antigen (HBsAg) was tested in 29,312 adult male mineworkers from 18 geographic regions, encompassing the diverse tribal and linguistic groups in the region, as well as in expatriate mineworkers from neighboring southern African countries. The same cohort was also tested for antibody to human immunodeficiency virus (HIV). Selected hepatitis B carriers were also tested for hepatitis B virus deoxyribonucleic acid (DNA), antibody to hepatitis D (anti-HD), and alpha-fetoprotein. The overall prevalence of HBsAg in this survey was 9.9%. However, the prevalence varied from 5.5% to 14% in different ethnic groups. A minority of carriers (4.9%) had replicative hepatitis B infection and were hepatitis B virus DNA-positive. Only 0.6% of tested carriers were anti-HD-positive. Alpha-fetoprotein determinations were abnormal in 1.2% of hepatitis B-positive men. These data show that although chronic hepatitis B infection remains widespread in southern Africa, carrier rates vary significantly from region to region. In contrast, hepatitis D co-infection remains extremely uncommon. These baseline seroprevalence data also establish that HIV infection was, in 1986, a rare infection in the indigenous population of South Africa.

Acquired Immunodeficiency Syndrome↗
PubMed1988

The interpretation of ELISA results by means of the standard deviation ratio.

An improved sensitivity to low levels of hepatitis B surface antigen (HBsAg) was demonstrated when ELISA results were interpreted by a statistical method. The absorbance of each test well was compared with the mean absorbance of all low-colour test samples. Those wells with an absorbance of more than two standard deviations above the mean were referred for confirmatory tests. Samples containing 1.0 ng/ml of HBsAg were reliably detected by a rapid assay technique (1.5 h). Predictive value analysis showed greater sensitivity than was possible from a direct comparison of test samples with controls.

Enzyme-Linked Immunosorbent Assay↗
PubMed1988

Radioiodination of murine anti-alpha-foetoprotein E.9 monoclonal antibody and its F(ab')2 fragment for the diagnosis of hepatocellular carcinoma.

The high incidence of hepatocellular carcinoma amongst certain population groups of Southern Africa made feasible the investigation of a radiolabelled monoclonal anti-alpha-foetoprotein as a radioimmunodiagnostic agent for this disease. This paper reports the preclinical trials with monoclonal anti-alpha-foetoprotein E.9 (anti-AFP) and its F(ab')2 fragment after radiolabelling with 131I. Various radioiodinations were tried. The best results were obtained with the lodogen and Bolton-Hunter methods. 131I from only one of the sources tested gave an 131I-labelled anti-AFP with meaningful immunoreactivity. It was shown by means of gamma-camera scans and monitoring of radioactivity in individual organs that 131I-anti-AFP and the 131I-anti-AFP F(ab')2 fragments did not accumulate abnormally in any organ(s) in healthy animals. The correlation in healthy mice of the biodistribution of 125I human IgG to 131I-anti-AFP, and 125I human IgG to 131I-F(ab')2 was good. Human hepatoma xenografts in athymic mice showed uptake of 131I-anti-AFP and the 131I-F(ab')2 fragment. The uptake of 131I-F(ab')2 was improved by liver background subtraction. There was correlation between circulatory alpha-foetoprotein concentrations and tumour uptake of 131I-F(ab')2 in tumour-bearing athymic mice and a definite relationship was found between tumour size and radiolabelled antibody and the F(ab')2 fragment. After the biological action of the 131I-anti-AFP and the 131I-F(ab')2 fragment was known, sterile pyrogen-free consignments were supplied for clinical trials in humans on a regular basis.

Animals↗
PubMed1985

Anti-HTLV-III testing--a practical solution for blood transfusion services?

Screening blood donations for anti-HTLV-III with a modification to a commercially available test kit has so far been found satisfactory--the reagent cost is less than R1.00 a donation. Should all transfusion services adopt this method, South Africa's total blood donations could be tested at a cost of about R650 000, instead of R2.7 million or more, a year.

Antibodies, Viral↗