Effect of tuftsin on embryo vaccination with Newcastle disease virus vaccine.

The effect of tuftsin of embryo and post-hatch vaccination with NDV-F was studied. The embryo vaccination with NDV-F resulted in more number of dead-in-shell embryos. To overcome this problem, the vaccine was treated separately with ethyl methane sulfate (EMS) and 5-fluorouracil (5-FU) and administered. Treating the vaccine with 5-FU resulted in better hatchability as compared to EMS treatment. In embryo, NDV antibody titres increased upto 2 weeks of age and declined thereafter, whereas in post-hatch vaccination, the antibody titre increased from second to fourth week of age and declined thereafter. The seroconversion was better when the vaccine was given along with tuftsin either to embryos or chicks (post-hatch vaccination) as compared to those vaccinated without tuftsin. Moreover, the percentage of hatchability was more in tuftsin administered groups. It was found that embryo vaccination can ensure definite protection during the early life of the chicks despite the presence of maternal antibodies. In cases where breeder vaccinations do not result in concomitant transfer of antibody to progeny chicks, embryo vaccination would give only neonatal resistance. During the later stages, embryo vaccination did not confer any advantage over post-hatch vaccination.

Detection of rabies virus antigen in animals by avidin-biotin dot ELISA.

An avidin-biotin dot ELISA test was standardized to detect rabies viral antigens from the brain of rabies-suspected animals. This test was compared with the direct fluorescent antibody test (FAT). The advantages of the avidin-biotin dot ELISA are discussed. The incorporation of avidin-biotin into a conventional ELISA is a step forward in improving the available rabies antigen detection procedures as this technique is more sensitive, highly specific and exploits the great affinity of avidin for biotin. No significant difference was observed between FAT and avidin-biotin dot ELISA.

A Dot enzyme linked immunosorbent assay (Dot ELISA): comparison with standard fluorescent antibody test (FAT) for the diagnosis of rabies in animals.

A modified enzyme linked immunosorbent assay (Dot ELISA) is described for visual detection of rabies antigen in animals. The test materials were dotted onto the nitrocellulose paper and allowed to react with rabies antiserum. The bound antigen--anti-body were reacted with a peroxidase conjugated antirabbit immunoglobulin. Positive reactions were easily visualized as brown dots after enzyme degradation of the substrate. A total of 400 specimens from various geographical locations were tested with the dot ELISA technique, and also with the fluorescent antibody test (FAT), which was used as a reference method. The concordance between the two tests was 95.25%. The dot ELISA may have potential applications as a rapid, simple and economical field test in the diagnosis of rabies.

Rapid Dot enzyme immuno assay for the quantitation of rabies antibodies.

A rapid dot enzyme immuno assay (Dot ELISA) for rabies antibody estimation has been standardized in which nitrocellulose sheet has been used as a solid support absorbing a commercial tissue culture rabies vaccine as antigen. The test was compared with a standard plate ELISA test. The results were comparable and the student "t' test for proportion revealed that plate ELISA test is significantly better (P 0.05) when compared to Dot ELISA for the number of sera with titre < 0.5 Iu/ml and in the case of > 0.5 IU/ml Dot ELISA is found to be better over plate ELISA test at the same significance level.

A dipstick dot enzyme immunoassay for detection of rabies antigen.

A dipstick Dot enzyme immuno diagnosis test was standardized to detect rabies viral antigens from brain, of rabies-suspected dogs, cattle, horses, cats and goats. This test was compared with the direct fluorescent antibody test (FAT). When compared to the direct FAT, the dipstick dot ELISA test did not produce non-specific false-positive results and was therefore specific and reliable. The advantages of the dipstick Dot-ELISA are discussed.

Dipstick enzyme immunoassay for rinderpest antibody in cattle.

A dipstick enzyme immunoassay (ELISA) has been standardized for the detection of rinderpest antibodies. One hundred and thirty bovine serum samples were analysed by the dipstick ELISA method and the results compared with the conventional plate ELISA method. The sensitivity was found to be similar in both methods. The dipstick ELISA does not require expensive micro-plates and an ELISA reader, and is recommended for use in field laboratories where the qualitative detection of rinderpest antibodies is required.

Characterisation of Newcastle disease viruses isolated in India.

Eleven Newcastle disease virus (NDV) isolates obtained from outbreaks of disease in chickens (9) and Japanese quail (2) in Tamil Nadu, India were characterised in pathogenicity tests, antigenically, using mouse monoclonal antibodies (MAbs), and other established tests devised to distinguish between different strains. All 11 isolates were shown to be highly virulent for chickens. In indirect immunoperoxidase tests used to assess the ability of a panel of 28 MAbs to bind to infected cell cultures, 10 of the isolates showed an identical reaction pattern, the other isolate (No. 4) failed to react with one MAb which bound to cells infected with the other isolates. Isolates 9 was unstable at pH 3 while the other 10 were stable. All other properties were shared by the 11 isolates.

Effect of carrageenan on humoral and protective immune responses of chicks vaccinated with Newcastle disease virus.

The effect of carrageenan (CGN) treatment on the generation of humoral and protective immune response to Newcastle disease virus vaccine was investigated in chicks. Carrageenan treatment significantly impaired the primary humoral immune response in vaccinated chicks. Further, the protective immune response in CGN-treated chicks was only 50% of that in the control vaccinated chicks. However, the post-challenge response was not altered by drug treatment. Indomethacin, a potent inhibitor of prostaglandin synthesis, was able to reverse the immunosuppressive effect of CGN. This finding suggests that prostaglandins might be involved in CGN-mediated immunosuppression in chicks.

Cross-protection aginst Salmonella enteritidis infection in mice. I. Immunization trials.

Mice were immunized subcutaneously with live and killed vaccines, with and without complete adjuvant incorporating Salmonella typhi-murium M206, Salmonella gallinarum 9R, Salmonella pullorum Sp223 as well as homologous Salmonella enteritidis Se795. The animals were challenged 21 days post-vaccination with 100 LD50 of virulent S. enteritidis 5694 SMR subcutaneously along with unvaccinated control mice. To assess the immunity against acute and chronic infections, the percentage of absolute survivors i.e. survivors without lesions and without the challenge organism, was taken as the criterion. Live vaccines proved better than killed vaccines. Live vaccines with complete adjuvant induced a good protection. Cross-protection could be induced with the live vaccine with complete adjuvant against S. enteritidis infection in mice.

Cross-protection against Salmonella enteritidis infection in mice.

Mice were immunized subcutaneously with live vaccines and live vaccines with complete adjuvant incorporating Salmonella enteritidis Se 795, Salmonella typhi-murium M206, Salmonella gallinarum 9R or Salmonella pullorum Sp223. They were challenged along with unvaccinated controls with 100 LD50 of virulent S. enteritidis 5694 SMR subcutaneously on the 21st day post-vaccination. The humoral immune response was studied by assessing the sequential level of agglutinins, complete and incomplete somatic antibodies, opsonophagocytic antibodies, cytophilic antibodies and bactericidal antibodies before and after challenge. The level of these antibodies and the protection afforded by the particular vaccine is correlated and the possible involvement of a humoral mechanism is discussed.

Cross-protection against Salmonella enteritidis infection in mice. III. Delayed hypersensitivity reaction and clearance of the challenge organism.

Mice were immunized with live vaccines and with live vaccines with complete adjuvant incorporating Salmonella enteritidis, Salmonella typhi-murium, Salmonella gallinarum or Salmonella pullorum. On the 21st day after vacination, the hypersensitivity reactions elicited by the mice to extracts of the challenge organism (S. enteritidis 5694 SMR) were assessed. The degree of delayed hypersensitivity reaction was compared with the level of protection induced by the vaccine. The role in protection of delayed hypersensitivity is discussed. Clearance of the challenge organism from the liver of previously vaccinated and unvaccinated mice was assessed quantitatively.