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H L Oei

Publications and source records attributed to H L Oei.

17 recordsLinked to original sources
PubMed2003

Correlation of haemagglutinin-neuraminidase and fusion protein content with protective antibody response after immunisation with inactivated Newcastle disease vaccines.

The correlation between the antigen content of inactivated Newcastle disease (ND) oil emulsion-vaccines and the serological response after immunisation was studied. The haemagglutinin-neuraminidase (HN) and fusion (F) proteins of Newcastle disease virus (NDV) were quantified in 33 inactivated oil-adjuvanted ND vaccines using isopropylmyristate (IPM)-extraction and antigen ELISAs. These commercial vaccines differed in NDV-vaccine strain, the method applied to inactivate the vaccine virus, the vaccine valence and the composition of the oil emulsions. Large differences, up to 100-fold, in the antigen quantities present in different vaccines were found. The NDV-HN content and the NDV-F content of the vaccines both highly correlated with the haemagglutination-inhibiting (HI) antibody titres after immunisation. These correlation's were found over a 10,000-fold range of applied antigen. The antigen content of the oil emulsion-vaccines also highly correlated with virus neutralising antibody titres. The presence of serum HI antibody titres in individual specific pathogens free (SPF)-chickens after immunisation with inactivated ND vaccines was highly indicative for clinical protection against challenge with the virulent NDV-Herts strain. Our results are the first to demonstrate that the protective serological response after immunisation highly correlates with the antigen content of oil-adjuvanted vaccines.

Adjuvants, Immunologic↗
PubMed2000

Antigen quantification as in vitro alternative for potency testing of inactivated viral poultry vaccines.

Routine batch control of licensed inactivated viral vaccines for poultry usually includes a potency assay as a measure of vaccine efficacy. Potency assays often consist of vaccination-challenge experiments in the target species or in laboratory animals. Instead of measuring the protection of vaccinated animals against virulent pathogens, the serological response after vaccination can be quantified for some vaccines. In vitro antigen quantification assays would be attractive alternatives for the current potency assays because the time and costs involved could be greatly reduced and animal use could be avoided. Such in vitro assays will only be acceptable when the correlation between results and efficacy or potency has been demonstrated convincingly. The results of our studies on antigen quantification assays indicate that, in principle, quantification of viral antigens from inactivated oil-adjuvanted vaccines is feasible and reproducible using specially developed antigen capture ELISAs in combination with specific software for statistical analysis of the ELISA data. We have developed methods to quantify the haemagglutination-neuraminidase (HN) and fusion (F) proteins of Newcastle disease virus (NDV), the viral protein 3 (VP3) of the infectious bursal disease virus (IBDV), and the spike-1 (S1) protein of the infectious bronchitis virus (IBV). Vaccination experiments with inactivated ND vaccines indicate that the in vitro quantified HN- or F-proteins of NDV are reliable indicators of the serological response after vaccination.

Animals↗
PubMed1987

Virulence of five live vaccines against avian infectious laryngotracheitis and their immunogenicity and spread after eyedrop or spray application.

Five live virus vaccines against avian infectious laryngotracheitis were studied with regard to safety, immunogenicity and route of administration. Significant differences in virulence between the vaccine strains were found. Reduced virulence was accompanied by a reduction of immunogenicity and capacity to spread. After eyedrop application, a low virulent vaccine induced 90-100% flock immunity for the first 10 weeks after vaccination (PV), followed by a slow decline to 50% at 31 weeks PV, whereas flock immunity induced with the more virulent types remained at about 90% till the end of the experiments (24 and 48 weeks PV). Aerosol vaccination induced 70-100% flock immunity but vaccine reactions were severe. Application of vaccine in a coarse spray did not result in adverse vaccine reactions but induced a maximal protection rate of only 50%. Microneutralisation titres provided a useful indicator of immunity from the onset of immunity until immunity started to decline. A vaccine virus carrier state was demonstrated by means of sentinel birds.

Aerosols↗
PubMed1987

Biological characteristics of Marek's disease vaccine CVI-988 clone C1.

Biological characteristics of Marek's disease virus (MDV) CVI-988 clone C, of importance for vaccine application, are described. CVI-988 clone C was shown to be nonpathogenic for highly MD-susceptible chickens and slightly more effective than prototype CVI-988 vaccine. During plaque purification and serial cell-culture passages, reductions were observed in the release of 'A' antigen from infected cell cultures, in spreading properties and in virus replication in vivo. Pre-licensing batches of CVI-988 clone C vaccine afforded excellent protection against challenge infection with virulent MDV and highly virulent MDV strains. Groups of chickens with bivalent (HVT/SB-1) vaccine-induced maternal antibodies were equally protected by a double dose of CVI-988 clone C vaccine. Field trials performed in the Netherlands and in the United States confirmed the safety and protective efficacy of monovalent CVI-988 clone C vaccine.

Animals↗
PubMed1985

Investigations on the sporicidal and fungicidal activity of disinfectants.

The sporicidal and fungicidal activity of disinfectants was studied in a suspension test. Glutaraldehyde 4%, sodium-dichloroisocyanurate-dihydrate (2400 ppm active chlorine) and peracetic acid 0.25% demonstrated after 30 min of exposure at 20 degrees C in the presence of 4% horse serum a clear activity against spores of Bacillus cereus. Under the same conditions formaldehyde 4% and glutaraldehyde 2% were also found to be sporicidal, but only after a longer time of exposure. Spores of Bacillus anthracis and B. cereus appeared to be comparably resistant against the investigated disinfectants, whereas conidiospores of Aspergillus fumigatus and Aspergillus niger were less resistant. Of the micro-organisms tested Candida albicans proved to be slightest resistant, while spores of Bacillus subtilis were found the most resistant.

Anti-Bacterial Agents↗
PubMed1984

[A study of the efficacy of disinfectants against anthrax spores].

The activity of disinfectants with regard to spores of Bacillus anthracis was determined in a suspension test. Creoline (10%) and also several other disinfectants for veterinary use showed no activity against spores of B. anthracis. Natriumdichloorisocyanuraat-dihydrate (2400 ppm active chlorine) and peracetic acid 0,25% demonstrated after 30 minutes of exposures at 20 degrees C in the presence of 4% horse serum a significant sporicidal effect. Under the same conditions formaldehyde 4% and glutaraldehyde 2% were also found to be sporicidal but only after 2 hours of exposure.

Bacillus anthracis↗
PubMed1980

Investigations on live vaccines against infectious bursal disease of chicks.

Four live virus vaccines against Infectious Bursal Disease (IBD) were studied with regard to their safety, immune response and applicability. None of the vaccines caused clinical symptoms or had an adverse impact on bodyweight. Differences between these vaccines were observed in their effect on the Bursa/Bodyweight Ratio and the severity of the microscopical lesions of the bursa Fabricii. The immunosuppressive effect of IBD vaccination at one day of age on the response to Newcastle disease vaccine applied was rather low. Three of the four vaccines induced antibodies associated with protection against challenge. Vaccination of SPF rearing chickens by drinking water at an age of 15 weeks produced an antibody response (Agar Gel Precipitin Test) whereas at 15 weeks produced an antibody response (Agar Gel Precipitin Test) whereas at an age of 23, 32 and 60 weeks it did not. Chickens of all age groups responded serologically to an intramuscular vaccination. A correlation was found between the immunological response and the effect of the vaccines on the bursa Fabricii.

Animals↗
PubMed1979

[Registering, licensing and investigating vaccines in animal disease control (author's transl)].

The registration, licensing and investigation of veterinary vaccines are discussed with reference to the producer, the user and the authorities. The significance of basic research by the producer, of testing by the authorities, of quality control and of evaluation (laboratory and field studies) in the control of animal diseases are examined more closely. The fact is stressed, that legislation concerning veterinary medicines in general and vaccines in particular should be well defined. All this is regarded as an integral part of recent developments in animal farming in the Netherlands.

Animal Diseases↗
PubMed1975

[Potency testing of inactivated rabies vaccines with the antibody binding test in comparison with the NIH and habel test(author's transl)].

The Antibody Binding Test, a new technique for the evaluation of inactivated Rabies vaccines, developed by Arko, Wiktor and Sikes, was compared with the NIH- and Habel Test. Various vaccines were tested with these methods with the following results and conclusions. 1. The Habel Test was useful for testing of Hempt vaccines. With highly potent vaccines however it was not possible to get exact protection values, for all vaccinated mice were protected against all virus dilutions. 2. The NIH Test seemed to have an advantage over the Habel Test, since animals are vaccinated only twice, instead of 6 times, within two weeks. But this test was less suitable for the evaluation of Hempt vaccines. The requested Antigenic Value was reached only rarely with these vaccines. Repeated, NIH Tests gave widely differing results with Hempt vaccines. Vaccines which passed the NIH Test also passed the Habel Test, but not always vice versa. Antigenic Values of highly potent vaccines could be determined exactly with the NIH Test. This method is much better standardized by using a Standard vaccine in the test. The NIH Test is preferable for inactivated Rabies vaccines, with the exception of vaccines containing brain tissue, like the Hempt vaccine. 3. The Antibody Binding Test is a useful technique for the examination of inactivated cell culture vaccines. Consistent results can be achieved by skilled and experienced laboratory personnel. To avoid irregularities in the mortality rates, at least 10 mice should be used for each dilution of vaccine. With this method only Rabies virus antigen is measured which is bound by serum antibody during an incubation period of 60 min. Other factors supporting immunization like adjuvant- or booster-effects are not evaluated. Compared with the Habel and NIH Test the Antibody Binding Test is the best method for the evaluation of the amount of antigen in a Rabies vaccine. Hempt vaccines reached - as they did in the NIH Test - only Antigenic Values in this test. Vaccines with an Antigenic Value of larger than or equal to 0,3 in the Antibody Binding Test gave positive results also in the Habel and NIH Test, Vaccines with a Protection Value of 10-3 in the Habel Test and an Antigenic Value of 0,3 in the NIH Test did not always reach an Antigenic Value of 0.3 in the Antibody Binding Test.

Animals↗
PubMed1975

[The effect of some antibiotics on multiplication of Coxiella burneti in the embryonated egg (author's transl)].

In chick embryos 7 days after cultivation, the effect of chloramphenicol, streptomycin, tylosin (0.5 to 32 mg/egg), and of penicillin (100 to 10000 IE/egg) on the process of replication of C.b. in the yolk sac was examined. The ELD50 and the EID50 were examined according to REED and MUENCH. The demonstration of coxiellae was performed microscopically. The results of the examinations are summarized in fig. 1 to 3. In infected untreated controls, the titres of the ELD50 were found at about 10(4) and those of the EID50 at 10(7). The best inhibition was obtained by means of chloramphenicol. In this case, neither a letality of embryos nor an infectivity of eggs was demonstrable by administration of 16 mg/egg. Streptomycin had a similar effect on the letality of embryos like chloramphenicol, but coxiellae were still microscopically demonstrable at doses of 16 and 32 mg/egg. A smaller effect had tylosin so that even after an administration of 32 mg/egg, a minimal letality of embryos and a minimal infectivity of eggs remained. Almost no inhibition was obtained by means of penicillin. Even at 10000 IE/egg, the letality of embryos was diminished only by 1 log 10 and the infectivity of eggs by about 3 log 10. After application of chloramphenicol, streptomycin, and tylosin, the embryos in infected eggs died regularly 1 to 2 days later than those in untreated infected controls with the same titres. Using penicillin, this effect could not be observed.

Animals↗
PubMedDate not supplied

Dose-response effects of inactivated Newcastle disease vaccines: influence of serologic assay, time after vaccination, and type of chickens.

Knowledge of the dose-response relation of inactivated vaccines and of the factors that influence this relation is essential for the evaluation of existing vaccine potency assays and the development of new potency assays that are based on the antigen content of the inactivated vaccines. We quantified the relation between vaccine dose, serologic response, and clinical protection after vaccination for three different inactivated Newcastle disease (ND) vaccines. Qualitatively, similar dose-response curves were obtained for the three vaccines when either the serologic response or the clinical protection of specific-pathogen-free (SPF) chickens was plotted against the different vaccine doses applied. However, the vaccines differed quantitatively: doses of vaccines that induced similar antibody titers or clinical protection differed 2-8-fold. In contrast with the narrow range of antibody titers induced by a full vaccine dose, a very broad range of titers was obtained after dilution of the vaccines. At least 95% of the SPF chickens with detectable antibody in the serum were protected against a challenge with virulent Herts ND virus. The relation between the dosage of two different ND vaccines and the serum antibody titers remained markedly constant between 3 and 18 wk after vaccination. Vaccination of broilers instead of layers with a dilution series of inactivated ND vaccine resulted in significantly lower antibody levels and less clinical protection against virulent challenge. In conclusion, despite quantitative differences, we found comparable dose-response relations for the three inactivated ND vaccines studied.

Animals↗
PubMedDate not supplied

Pathogenicity studies with plaque-purified preparations of Marek's disease virus strain CVI-988.

The pathogenicity of Marek's disease (MD) strain CVI-988 vaccine, eight plaque-purified preparations originating from this strain, and the vaccine HVT FC126 (based on herpesvirus of turkeys) was determined by intramuscular administration of high virus doses to day-old specific-pathogen-free Rhode Island Red (RIR) chickens, which are extremely MD-susceptible. Paralysis and neuritis were observed in 88% of RIR chickens inoculated with MDV CVI-988 at the cell-passage level of the commercial vaccine. HVT FC126 caused paralysis in two of 39 RIR chickens tested, of which one had an endoneural lymphoma, and another three had endoneural inflammation. Five plaque-purified MDV CVI-988 virus preparations at various cell-culture-passage levels caused no lesions. Of another three clones, two caused inflammatory B-type lesions in the nerves of 1/10 chickens, and the third clone caused inflammatory nonneoplastic MD lesions in the liver of 1/11 chickens.

Animals↗