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PubMed1975

Dynamics of the immune response in rabbits immunized with spreptococcal extracellular antigens: comparison of the Streptozyme agglutination test with three specific neutralization tests.

The dynamics of the immune response to streptococcal extracellular antigens as measured by the streptozyme agglutination test have been defined in experimental animals andcompared with the dynamics of the immune response as determined by three established neutralization tests for streptococcal antibodies (ASO, anti-DNase B,and anti-NADase). In rabbits immunized with streptococcal extracellular Streptozyme-measured antibodies rose more quickly and peaked earlier than did antibodies to streptolysin O, streptococcal DNase-B, and streptococcal NADase. Additional studiesrevealed that the early peak was primarily due to 2-mercaptoethanol-sensitive (19S) antibody and that the later rise in Streptozyme-measured antibodies was due to 2-mercaptoethanol-resistant (7S) antibody. Preliminary observations using sucrose gradient ultracentrifugation tended to confirm this interpretation. These data provide a possible explanation for the early detection of a streptococcal antibody response by the Streptozyme test which has also been described in humans. The data suggest a theoretical advantage for the Streptozyme agglutination test in patients with streptococcal infections and their sequealae. However, the complexity of the Streptozyme reagent suggests that more extensive studies are needed to assure the consistent reproductivity of results with different lots of the test reagent.

Agglutination Tests↗
PubMed1978

Vero microcultures for adenovirus neutralization tests.

A microculture neutralization test is described for measuring specific antibody levels to the 35 human adenovirus serotypes in Vero cells. The test is read at 5 days by macroscopic observation after staining the uninfected cells with crystal violet. The test is performed with a minimum of manipulations and gives serum titers comparable with those obtained in tube macrocultures of monkey kidney, human embryonic kidney, and Vero cells. The Vero microculture neutralization test measures inhibition of adenovirus toxicity, although selected human adenoviruses serially subpassaged in Vero cells were shown to successfully adapt and replicate in the absence of detectable helper viruses.

Adenoviruses, Human↗
PubMed1987

A comparison of the indirect haemagglutination test with the toxin neutralization test for the estimation of diphtheria antitoxin in mouse sera.

Serum samples from 42 groups of mice immunized for different immunization periods with various doses of Adsorbed Diphtheria-Tetanus Vaccine, Adsorbed Diphtheria-Tetanus and Pertussis Vaccine and a standard diphtheria toxoid were assayed for their diphtheria antitoxin content by indirect haemagglutination (IHA) and by toxin neutralization (TN) tests. A very good correlation of 0.91 was obtained between the results of the two methods. There was no statistically significant difference between the IHA and the TN titres obtained. Adsorption with sheep red cells and treatment of the sera with 2-mercaptoethanol had no effect on the IHA titres. The minimum level of antitoxin detectable by the IHA test was 0.00039 IU ml-1. IHA proved to be a sensitive, specific and reproducible method which can be used reliably for the assay of diphtheria antitoxin in mouse sera.

Animals↗
PubMed2001

Comparison of immunoperoxidase plaque staining and neutralizing tests for canine distemper virus.

The use of immunoperoxidase plaque staining (IP) in the antibody test for canine distemper virus (CDV) and its diagnostic value were investigated. Antibody titres by the IP test and neutralizing test (NT) against CDV were compared in 114 specific pathogen-free (SPF) dogs, including 84 CDV-vaccinated and 30 unimmunized dogs. All of the unimmunized dogs, which had negative NT titres, also showed negative IP titres, and all of the CDV-vaccinated dogs, which had positive NT titres, showed positive IP titres. Furthermore, the IP titres showed similar changes with time after vaccination to the NT titres in five CDV-vaccinated SPF dogs. These findings indicate that the IP test has similar specificity to the NT. Next, the IP and NT titres were compared in 190 clinically suspected cases of canine distemper (CD), including 107 dogs with neurological signs and 83 dogs without neurological signs, and also in 50 clinically healthy dogs. Among the suspected cases of CD, of 46 dogs with neurological signs and 29 dogs without neurological signs, and which had negative NT titres, 33 (72%) and 19 (66%), respectively, showed positive IP titres. Many suspected cases of CD showed a high IP titre despite a low NT titre. In contrast, among healthy dogs, none of 9 NT-negative dogs showed positive IP titres. The difference in the IP and NT titres (log10) [reciprocal of IP titre] - log10) [reciprocal of NT titre]) was measured to investigate the agreement between IP test and NT. The differences were 1.488 +/- 0.867, 1.245 +/- 0.833, 0.595 +/- 0.351 and 0.594 +/- 0.372, respectively, in the suspected cases of CD with neurological signs, the suspected cases of CD without neurological signs, the healthy dogs and the SPF dogs. The differences in the suspected cases of CD were significantly high compared to those for the SPF dogs (p < 0.001). Furthermore, in 8 dogs diagnosed as cases of CD from their paired sera, whose initial sera showed a markedly low NT titre compared to the IP titre, 5 dogs without neurological signs developed neurological signs later. These findings suggest that the IP test can detect CD during its early phases and in dogs with low antibody levels, undetectable by NT, and so would be useful for serological diagnosis.

Animals↗
PubMed2006

Human cell lines used in a micro neutralization test for measuring influenza-neutralizing antibodies.

An in situ neutralization test (NT) including ELISA for the measurement of influenza antigen was developed and evaluated. Two human cell lines, fibroblasts (HS27) cells and salivary gland epithelial duct (HSG) cells, were compared with Madin-Darby Canine Kidney (MDCK) cells. The viral production in the human cell lines was lower than that for MDCK cells, which influenced the results of the assay in the HSG and HS27 cells. However, when lowering the infectious dose, the NT using HS27 cells gave a sensitive and stable assay with low background in the ELISA. The NT titres were very low when using HSG cells compared to MDCK cells. The HS27 NT was used to analyze the humoral response after an influenza A infection in patients from a placebo-controlled zanamivir study. We found no differences in NT titres between patients treated with zanamivir or placebo. The MDCK and HS27 NT gave higher titres and more pronounced titre differences than the gold standard haemagglutinin inhibition (HAI) assay. Compared to the HAI assay, the sensitive NT using HS27 cells also revealed heterologous NT-titre rises after influenza infection in the patients.

Adolescent↗
PubMedDate not supplied

The micro-focus reduction neutralization test for determining dengue and Japanese encephalitis neutralizing antibodies in volunteers vaccinated against dengue.

A micro-focus reduction neutralization test (mFRNT) was evaluated as an alternative test to the ordinary plaque reduction neutralization test (PRNT) for the determination of dengue virus and Japanese encephalitis virus neutralizing antibody responses in persons receiving dengue vaccine. The 2 tests were similar in terms of titres and ability to detect seroconversion. Although the neutralizing antibody titres obtained by mFRNT were slightly lower than those given by PRNT, the differences were less than two-fold, indicating than mFRNT was reliable. Reproducibility of mFRNT was confirmed by 10 replicate tests using the same control serum. Therefore, mFRNT may be useful in large-scale investigations of neutralizing antibody levels, for example, in young children forming part of an immunization programme; it can be performed quickly and is economical, requiring only a small volume of sera.

Antibodies, Viral↗
PubMed1950

Immunological reactions of the Coxsackie viruses. I. The neutralization test; technic and application.

The neutralization test is a reliable and useful procedure for following immunological reactions of the Coxsackie viruses (C virus). The standard procedure has been an incubation period of 1 hour at room temperature followed by subcutaneous inoculation into newborn mice. However, this time and temperature are not critical, for the virus in neutralized within 10 minutes of mixing with immune serum and remains neutralized for long periods. During the variable incubation periods used, the control virus remained active, even in dilute suspensions. The neutralization test is not affected by the presence or absence of complement. Neutralizing antibody is stable at 65 degrees C. for 30 minutes, and immune serum has to be heated to 80 degrees C. for 30 minutes before the antibody is no longer detectable. As the quantity of virus is increased, the quantity of serum required for neutralization likewise increases, but not in a regular or predictable fashion. Neutralized mixtures of the virus can be made infective again by simple dilution before inoculation. The neutralization test is a satisfactory means for typing Coxsackie viruses. At least seven antigenic types have been identified. Similar antigenic types have been found to be scattered over wide areas. Thus the Conn.-5 type was present in 1948 in Massachusetts, Connecticut, New York, and North Carolina. The Texas-1 type was present in 1943 in Connecticut and in 1948 in North Carolina and Texas. Further information on the specificity of the neutralizing antibody response has been obtained from a study of the occurrence and development of antibodies in 6 patients who contracted infections with one or another of the C viruses while working with them in the laboratory. From each patient a virus was isolated during the illness. No patient had detectable antibodies to his strain before his illness, but each soon thereafter developed antibodies to his own strain and to the prototype strain to which it was related. By means of the neutralization test, it has been shown that a family epidemic may include two different immunological types of virus. Neutralizing antibodies appear at the time of or soon after onset of illness, increase rapidly to titers of about 1:1000 which are maintained during the period of 1 to 3 months following infection, and are still present 2 years later, although at lower levels. Neutralizing antibodies are present in the normal population. In North Carolina, over 80 per cent of the children have antibodies at birth. The level falls rapidly to a minimum of 14 per cent at the age of 1, and then it quickly rises to reach the adult level at the age of 7. Gamma globulin collected in various parts of the United States between 1944 and 1949 and in Denmark in 1949 neutralizes at least four antigenically different Coxsackie viruses.

Adult↗
PubMed1997

[Comparison of different BVD virus strains for their use in the differential diagnosis of classical swine fever--an attempt to standardize neutralization tests].

Six bovine virus diarrhoea (BVD) virus strains were tested in the neutralization test for their use in the differential diagnosis in classical swine fever (CSF) serology. The aim of the investigation was to find a suitable BVD virus strain guaranteeing a safe differentiation of CSF- and BVD virus induced antibodies using permanent cell cultures (PK-15, MDBK). For test purposes the neutralizing antibody titres of 73 defined test sera were titrated against the CSF virus strain Alfort/187 as well as the BVD virus strains Grub, Paplitz, NADL, 1138/69, Stendal, 10421/Han 94). Tests were repeated fivefold. The level of mean antibody titres, the differences in titre to the homologous pestivirus strain, the standard deviation and the variation coefficient served as test criteria. The BVD virus strains Grub and NADL yielded the best results. In view of harmonization and standardization the BVD virus strain NADL in connection with a standard protocol for neutralization tests is recommended for the differential diagnosis in CSF serology. Due to the adaptation of the permanent cell-lines PK-15 and MDBK to horse serum a further source of contamination with non cytopathogenic BVD viruses under routine conditions can be excluded.

Animals↗
PubMed2002

Applications of selective neutrality tests to molecular ecology.

This paper reviews how statistical tests of neutrality have been used to address questions in molecular ecology are reviewed. The work consists of four major parts: a brief review of the current status of the neutral theory; a review of several particularly interesting examples of how statistical tests of neutrality have led to insight into ecological problems; a brief discussion of the pitfalls of assuming a strictly neutral model if it is false; and a discussion of some of the opportunities and problems that molecular ecologists face when using neutrality tests to study natural selection.

Animals↗
PubMed1979

Sensitive neutralization test for rubella antibody.

A modified rubella virus plaque neutralization test for measuring rubella antibody was developed based on the potentiation of the virus-antibody complex by heterologous anti-immunoglobulin. The test is highly sensitive, yielding titers on the average 50 to 100 times higher than the haemagglutination inhibition test or the conventional plaque neutralization test. The sensitivity of this enhanced neutralization test is somewhat limited by the existence of a prozone phenomenon which precludes testing of low-titered sera below a dilution of 1:16. No prozone effect was observed with cerebrospinal fluids. The specificity of the enhanced neutralization test was determined by seroconversion of individuals receiving rubella vaccine. Although the rubella hemagglutination inhibition test remains the test of choice in routine diagnostic and surveillance work, the enhanced rubella neutralization test is particularly useful in monitoring low-level antibody in the cerebrospinal fluid in patients with neurological disorders and in certain instances of vaccine failure.

Adolescent↗
PubMed1980

Modified radial-plaque-neutralization test for demonstration of enterovirus neutralizing antibodies.

A simple radial method based on the formerly described paper disc technique was developed for demonstration of neutralizing antibodies to enteroviruses with plaque forming ability. Sera administered by 5 microliter wire-loops to wells cut into the agar overlay of virus infected cell monolayers produced radial neutralization zones with a size directly related to their specific antibody contents. Results of poliovirus neutralizing antibody tests performed by the radial plaque neutralization method were found to be in a good agreement with those obtained in antibody titrations either in monolayer tube cultures or in microtitre system. The relatively simple technique makes possible to investigate several hundreds of serum samples in a single experiment, so it is especially suitable for use in expanded serological surveys. It proved to be useful also for identification of enteroviruses and for testing the laboratory strains for identity.

Antibodies, Viral↗