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PubMed1978

[Control of immunity against swine plague by the viral neutralization test on rabbits].

An idea may be got on the properties of the vaccine by applying a specific gamma-globulin against swine fever in pigs, mixed in definite amounts with lapinized K-vaccine and this mixture is injected to rabbits. By studying the mixture of sera from pigs, vaccinated against swine fever prior to a fixed period of time, and the K-vaccine, applied to rabbits, an idea may be obtained on the tension of the immunity and re-vaccination requirements may be assessed.

Animals↗
PubMedDate not supplied

Jatobal virus antigenic characterization by ELISA and neutralization test using EIA as indicator, on tissue culture.

A virus antigenic characterization methodology using an indirect method of antibody detection ELISA with virus-infected cultured cells as antigen and a micro virus neutralisation test using EIA (NT-EIA) as an aid to reading were used for antigenic characterization of Jatobal (BeAn 423380). Jatobal virus was characterized as a Bunyaviridae, Bunyavirus genus, Simbu serogroup virus. ELISA using infected cultured cells as antigen is a sensitive and reliable method for identification of viruses and has many advantages over conventional antibody capture ELISA's and other tests: it eliminates solid phase coating with virus and laborious antigen preparation; it permits screening of large numbers of virus antisera faster and more easily than by CF, HAI, or plaque reduction NT. ELISA and NT using EIA as an aid to reading can be applicable to viruses which do not produce cytopathogenic effect. Both techniques are applicable to identification of viruses which grow in mosquito cells.

Animals↗
PubMed1981

Micro method for performing titration and neutralization test of hog cholera virus using established porcine kidney cell strain.

Hog cholera (HC) virus and antibody against it were estimated by the END method with microplates and CPK porcine kidney cell strain. To establish the technique of this method, studies were made on such basic conditions of the method as the type of strain of Newcastle disease virus (NDV), the time of challenge with this virus, and the concentration of serum in culture fluid. There was little difference in the infective titer of HC virus estimated between the END method performed by the established technique and the same method by the conventional technique with test tubes and swine testicle (ST) cells. Besides, there was a high correlation between the neutralizing antibody titer measured by the one technique and that measured by the other. The coefficient of correlation was r = +0.948 in this case. From the experimental results mentioned above it was concluded that the END method by the micro-technique with CPK cells was simpler than and as reliable as the same method conducted by any conventional technique, and that it was a practicable one capable of testing many samples.

Animals↗
PubMed1988

[A microtitration and neutralization test for infectious laryngotracheitis virus. Their reproducibility and the effect of various tests conditions].

The reproducibility of micro-assays for ILTV was assessed. The standard deviation of the virus assay in three successive determinations was 0.4, 0.4 and 0.3 log TCID50. The micro-neutralisation test produced standard deviations of 0.6, 0.8, 0.5, 1.2 and 1.1 log2 in various experiments. Preincubation for 24 hours at 39 degrees C, rather than for sixty minutes at 22 degrees C, which was suggested by Bitsch to enhance sensitivity, resulted in antibody titres which were approximately 1 log2 higher, though the specificity of the test declined markedly. The dose-response relationship between virus and antibody titre was curvilinear, the steepest part of the slope being in the lower range. Thermal inactivation and freezing and thawing resulted in a significant reduction of serum titres (P less than 0.01). The following method is suggested as a practical standardised procedure: freezing of sera prior to processing: omission of thermal inactivation and preincubation for sixty minutes at 22 degrees C.

Animals↗
PubMed2001

Comparison of 16 chelonid herpesviruses by virus neutralization tests and restriction endonuclease digestion of viral DNA.

A total of 16 chelonid herpesviruses that were isolated between 1992 and 1998 were compared with one another on the basis of serology and restriction enzyme digestion patterns of viral DNA. The viruses stem from tortoises of three different species in four different European countries and the United States of America. The majority of the isolates were similar to one another. One isolate, however, differed strongly from all others both serologically and in the restriction cleavage pattern of its DNA, showing that there are at least two different sero- and genotypes of herpesviruscs that infect tortoises.

Animals↗
PubMed1978

Thrombin generation and neutralization test (TGNT) - a simple, practical, and sensitive assay for plasma heparin quantitation.

A simple, quantitative method for detection of small amounts of heparin in human plasma is described. This method is based on the activation of coagulation factor X to its enzymatic form (Xa), by a mixture of RVV platelet substitute (Esnouf and Williams 1962, Esnouf and Jobin 1967) in a plasma rendered fibrinogen free without affecting other clotting factores (Bell et al. 1968, Bell 1973), by Arvin (Ancrod). Activation of factor X, results in thrombin generation. Thrombin inactivation by its natural inhibitors depends on the time elapsed from the start-point of activation. The inactivation process is enhanced by heparin (Biggs et al. 1970, Blombäck et al. 1963) and this enhancement depends on the quantity of heparin in the plasma.

Blood Coagulation↗
PubMed1969

The chick embryo neutralization test in the assay of meningococcal antibody. 1. Infection of the embryo with Neisseria meningitidis.

Present methods of controlling meningococcal cerebrospinal meningitis have failed to contain the disease. This has led to the search for effective vaccines and to the development of methods for assaying the potency of these vaccines, as well as for measuring the immune response of the individual. The feasibility of using the sero-protection test in embryonated eggs for the assay of meningococcal antibody has been investigated. The paper describes detailed investigations of the infectious process established by injecting Neisseria meningitidis by various challenge routes. Embryos, even 10-12 days old, showed high susceptibility to meningococci injected via the yolksac or chorioallantoic vein, and lesser susceptibility when injected via the intra-allantoic and chorioallantoic routes. The deaths of intravenously inoculated embryos coincided with the multiplication of the organisms and ensuing septicaemia. A study of the infection in embryos which had died, or were killed, 18-24 hours after inoculation showed a specific localization of the organisms in the brain.

Animals↗
PubMed1990

Ancestral lysozymes reconstructed, neutrality tested, and thermostability linked to hydrocarbon packing.

The controversy surrounding the idea that neutral mutations dominate protein evolution is attributable in part to the inadequacy of the tools available to evolutionary investigators. With a few exceptions, most investigations into the force driving protein evolution have relied on indirect criteria for distinguishing neutral and non-neutral variants. To investigate a particular pathway of molecular evolution, we have reconstructed by site-directed mutagenesis likely ancestral variants of the lysozymes of modern game birds (order Galliformes), tested their activity and thermostability and determined their three-dimensional structure. We focused on amino acids at three positions that are occupied in all known game birds either by the triplet Thr 40, Ile 55, Ser 91, or by the triplet Ser 40, Val 55, Thr 91. We have synthesized proteins representing intermediates along the possible three-step evolutionary pathways between these triplets. Although all of these are active and stable, none of these intermediates is found in known lysozymes. A comparison of the structures and thermostabilities of the variants reveals a linear correlation between the side-chain volume of the triplet and the thermostability of the protein. Each pathway connecting the two extant triplet sequences includes a variant with a thermostability outside the range of the extant proteins. This observation is consistent with a non-neutral evolutionary pathway. The existence of variants that are more stable than the extant proteins suggests that selection for maximum thermostability may not have been an important factor in the evolution of this enzyme.

Amino Acid Sequence↗
PubMed2004

Protective levels of canine distemper virus antibody in an urban dog population using plaque reduction neutralization test.

Blood samples from 50 dogs were collected at three veterinary clinics in Ibadan and Abuja, Nigeria and the serum from each sample was evaluated serologically for neutralizing antibodies against canine distemper virus (CDV) by the highly sensitive plaque reduction (PRN) neutralization assay. Thirteen dogs had plaque reduction neutralization titres of 0-100, seven had titres of 100-1,000 while 30 had titres ranging from 1,000-6,000. The PRN titres of vaccinated dogs were found to be significantly higher than unvaccinated dogs. The widespread use of the highly reproducible PRN test for the evaluation of antibody response to CDV may be very important in the generation of international CDV positive serum standards that should help to improve pre-and post-vaccination testing of dogs worldwide.

Animals↗
PubMed1973

Three-day assay for human cytomegalovirus applicable to serum neutralization tests.

A fluorescing cell assay (FCA) technique utilizing the indirect fluorescent-antibody method to measure human cytomegalovirus (CMV)-infected cells has been applied to the rapid determination of CMV-neutralizing antibody. Human sera with complement fixation titers to CMV of 1/32 or greater and fluorescein-conjugated rabbit anti-human globulin are the primary and secondary reagents in the fluorescent-antibody test. FCA measured in 3 days the same number of infectious units measured by plaque assay in 2 weeks. FCA and plaque assay yielded identical neutralizing antibody titers to CMV in 20 human sera.

Animals↗
PubMed1979

A rapid neutralization test for antibodies to bovine leukemia virus, with the use of rhabdovirus pseudotypes.

Two rhabdoviruses, vesicular stomatitis (type Indiana) and Chandipura viruses, formed pseudotype particles with envelope antigens provided by bovine leukemia virus (BLV). The pseudotypes are infectious for calf, human, mink, and rat cells, but the most sensitive indicator proved to be the Vero cells. Infectivity of the pseudotypes was increased by DEAE-dextran present during adsorption. Sera of spontaneously infected cattle contained high titers (some over 1/10,000) of antibodies neutralizing the pseudotypes, whereas sera of cattle from uninfected herds possessed no neutralizing activity in 1/10 dilution. The neutralization of these pseudotypes can serve as a rapid and sensitive test for the detection of antibodies in the cattle infected with BLV.

Antibodies, Viral↗
PubMedDate not supplied

Immunogenicity of Trypanosoma cruzi strains determined by neutralization test.

Trypomastigotes of the CA-I strain of Trypanosoma cruzi, which is practically non-lethal for mice, exhibited adhered antibodies when harvested 25-28 days pi and handled at 4 degrees C, whereas at 37 degrees C they became negative within 10-15 min. Mice injected with these tryp pre-incubated with anti-RA rabbit serum (shown to contained neutralizing antibodies against the homologous strain) developed a significantly lower parasitemia than controls while those pre-incubated with anti-CA-I serum showed only a delay in the parasitemia pattern. Neutralizing activity was undetectable in anti-CA-I rabbit and mouse sera when the test was performed under standard conditions against RA-tryp. On the other hand, neutralizing antibodies were demonstrated in few anti-CA-I mouse serum samples against RA strain when the test was performed increasing the sensitivity in order to reach no more than 75% lethality for controls. In these cases, a close relationship between "infective dose size-immune response achieved" was found, being only a narrow range of inocula able to trigger detectable neutralizing activity (10(4) CA-I tryp inoculum). Variations in the degree of neutralizing activity as a function of the infective doze size was also demonstrated for anti-RA mouse sera and, despite every antiserum prepared with this T. cruzi strain was reactive, the best values were proved for those prepared with inocula up to 10(2) tryp. Above optimal parasite dose size, both strains induced a drop of neutralizing activity.

Animals↗
PubMedDate not supplied

[The relationships between antitoxic titers determined in a group of young people before and after booster ADT by the in vivo neutralization test. Comparative NT-PHAR evaluations].

The geometrical mean of antitoxic titers determined in a lot of immunized young men who received, 5-7 years before, a booster with diphtheria-tetanus bivaccine, was of 1.54 (x/divided by 10.54) I.U./ml. At one month after another booster, performed with Tetanus toxoid (adsorbed), an increase of 34 times was recorded, the geometrical mean reaching the value of 52.67 (x/divided by 10.42 I.U./ml). The covering coefficients of the minimal protective antitoxin level have increased from 154 to 5267, in the estimation performed at the level of geometrical mean (calculating the ratio between the value of this indicator and that of the protection limit) and from 1623 to 54935, or from 15 to 505, respectively, in the estimations performed at the levels of the limits of the statistical range of one geometric standard deviation (Mg x/divided by D Sg). The study of the relations between pre- and post-antitoxic titers, performed by the linear regression analysis, leads to an equation whose slope evidenced the lower amplitude of the booster titers, along the increase of previous titers. The study of the inter-methods (neutralization-passive haemagglutination) regression allowed to obtain a correlation coefficient, between methods, of r = 0.83 and to perform the transposition of the minimal protective N.T. level (0.01 I.U.) in the terms of passive haemagglutination reaction, at the titer of 160 (0.3 PHAU/ml), for the p less than or equal to 0.05 probability level.

Adsorption↗
PubMed1987

Neutrality tests of highly polymorphic restriction-fragment-length polymorphisms.

The allele frequency data of Baird et al. were tested using Ewens-Watterson sampling theory for goodness of fit to the infinite-alleles model of neutral evolution. Although probes of both the HRAS-1 and D14S1 loci identify highly diverse restriction-fragment-length polymorphisms, the observed values of gene identity (F) and the common allele frequency (C) are not significantly different from the neutral expectation. Allele frequency distributions show a tendency toward a deficit in diversity for HRAS-1 and a slight excess diversity for D14S1. The direction of these departures is consistent with potential selective effects of the Harvey-ras oncogene and hitchhiking of the D14S1 locus to closely linked immunoglobulin genes. Direct chi 2-tests of goodness of fit of the observed and expected allele frequency distributions reveal significant departures in the caucasoid and Hispanic HRAS-1 distributions but not in any of the other tests.

Alleles↗
PubMed2000

Neutrality tests of conservative-radical amino acid changes in nuclear- and mitochondrially-encoded proteins.

The neutralist-selectionist debate should not be viewed as a dichotomy but as a continuum. While the strictly neutral model suggests a neutralist-selectionist dichotomy, the nearly neutral model is a continuous model spanning strict neutrality through weak selection (Ns approximately 1) to deterministic selection (Ns>3). We illustrate these points with polymorphism and divergence data from a sample of 73 genes (31 mitochondrial, 36 nuclear genes from Drosophila, and six Arabidopsis data sets). In an earlier study we used the McDonald-Kreitman (MK) test to show that amino acid replacement polymorphism in animal mitochondrial genes and Arabidopsis genes show a consistent trend toward negative selection, whereas nuclear genes from Drosophila span a range from negative selection, through neutrality, to positive selection. Here we analyze a subset of these genes (13 Drosophila nuclear, ten mitochondrial, and six Arabidopsis nuclear) for polymorphism and divergence of conservative and radical amino acid replacements (a protein-based conservative-radical MK, or pMK, test). The distinct patterns of selection between the different genomes is not apparent with the pMK test. Different definitions of conservative and radical (based on amino acid polarity, volume or charge) give inconsistent results across genes. We suggest that segregating fitness difference between silent and replacement mutations are more visible to selection than are segregating fitness differences between conservative and radical amino acid mutations. New data on the variation among genes with different opportunities for positive and negative selection are as important to the continuum view of the neutralist-selectionist debate as is the distribution of selection coefficients within individual genes.

Amino Acids↗
PubMed1984

Immune response to different tick-borne encephalitis vaccines as revealed by lymphocyte blast transformation and virus neutralization tests.

Immunological memory has been demonstrated in lymphocytes of persons vaccinated against tick-borne encephalitis (TBE). Stimulation indices (SI) of lymphocytes in response to TBE virus antigens in lymphocyte blast transformation test increased after complete vaccination course with the commercial vaccine; by this time, sera of vaccinees contained virus neutralizing antibodies. The concentrated purified vaccine had a higher immunogenic activity, as evidenced by increased SI and virus neutralizing antibodies (NA) in the vaccinated subjects already after the first and second vaccinations.

Adolescent↗
PubMed1986

A two-locus neutrality test: applications to humans, E. coli and lodgepole pine.

The expected disequilibrium between two loci with k alleles at one locus and l alleles at the other is given for a sample of size n drawn from a population under neutrality equilibrium. Three different measures of disequilibrium with 95% intervals are tabulated for combinations of n, k, l and 4Nc, where N is the effective population size and c is the amount of recombination between the loci. The extent and pattern of disequilibrium are strongly dependent upon 4Nc and are somewhat dependent on n, k and l. The 95% intervals are large, particularly for low numbers of alleles and low values of 4Nc. As examples, observed disequilibrium from histocompatibility loci in humans (HLA) and electrophoretic data in E. coli and lodgepole pine were compared to these theoretical values. Using information about recombination rates, the HLA data showed more disequilibrium than neutrality expectations, whereas electrophoretic data from E. coli and lodgepole pine had somewhat less disequilibrium than neutrality expectations.

Alleles↗