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PubMed1990

[Epizoologic studies of the detection of antibodies against Aujeszky's disease virus in sera and blood eluates of swine from Thailand using ELISA ("Enzygnost," Behring), serum neutralization test and "Aujeszky Latex Kit" (Iffa Merieux)].

The results of three tests for Aujeszky's disease were analysed and compared. The presence of Aujeszky's antibodies was determined by "Enzyme-linked-Immunosorbent-Assays" (ELISA, "Enzygnost"), Behring company, Marburg; "Serum-Neutralization-Tests" (SNT); and "Latex Agglutination-Tests" (LT, "Aujeszky-Latex-Kit"), Iffa Merieux company, Laupheim. Whole blood and sera samples were taken from 805 swine from 26 of Thailand's provinces. These samples were analysed to determine if eluates of whole blood on filter paper were as effective as corresponding sera samples in determining the presence of Aujeszky's disease antibodies. From a total of 805 samples, 26% of the serum and 18% of the blood eluate samples showed a positive result when tested by the ELISA method. Clearly, testing whole blood eluates provides results which are inferior to results from sera samples. Therefore the ELISA whole blood eluates test can only be recommended with reservations. Further testing was done on 645 serum samples using SNT. Samples tested were those which gave negative, suspicious, or weakly positive results when tested by ELISA. Using SNT, 23% of these showed a positive result. Many serum and blood eluate samples were also tested by LT. Most of these test samples were chosen because they were deemed suspicious. Suspicious samples were defined as those which had deviant test results. According to these results the sensitivity of LT was between the sensitivity of SNT and ELISA. Owner survey responses tended to state that few animals had been vaccinated. This coupled with the frequency of antibody occurrence proves the high rate of infection among Thailand's swine population.

Animals↗
PubMed1990

A refined complement-enhanced neutralization test for detecting antibodies to Junin virus.

A refined, complement-enhanced, plaque-reduction neutralization test was developed for measuring neutralizing antibodies against Junin (Argentine hemorrhagic fever) virus. The assay measured neutralizing antibodies after natural as well as vaccine-induced Junin virus infections. Among vaccinated individuals, titers were 2-4-fold higher than those obtained with conventional assays, without loss of specificity. Enhanced sensitivity was achieved by using a standardized complement source (vs human or animal serum) for virus dilution, incubation of virus-serum mixtures at 36 degrees C for 2 h (vs overnight at 4 degrees C) prior to plaque assay, control of age and density of cell monolayers, and variation in overlay conditions.

Analysis of Variance↗
PubMed1976

[Use of the neutralization test for mass population studies].

The authors applied the antibody neutralization test (ANT) for detection of causative agent of intestinal infections in feces of healthy population in Turkmenia. Some part of the material was studied in parallel with the aid of the ANT and by the bacteriological method. As a result of comparison it appeared that in using the ANT causative agents of intestinal infections were revealed much more frequently than by the bacteriological method; in this connection this serological method can be recommended as an auxiliary one for the diagnosis of intestinal infections.

Diagnosis, Differential↗
PubMedDate not supplied

Comparison of indirect immunofluorescence test for measles antibodies with haemagglutination inhibition and plaque neutralization tests.

Indirect Immunofluorescence (IFA), Plaque Reduction Neutralization (PRN) and Haemagglutination Inhibition (HI) tests for measles antibodies were carried out in 197 sera obtained from umbilical cord and vaccinated children. The IFA was also applied to blood samples collected with filter paper. IFA results demonstrated that the test is relatively simple to perform, with good reproducibility for different antigen lots. Good correlation was obtained between IFA, PRN and HI antibody titers. Better correlation was demonstrated with IFA and PRN than with HI and PRN tests. Sensitivity of IFA in detecting antibody was less effective than PRN, however more effective than HI using rhesus monkey red blood cells. PRN antibody titers over 100 were detected by IFA but not by HI (9.7% with negative results). IFA may be of considerable practical use and able to substitute HI in seroepidemiological surveys and to evaluate vaccine efficacy. It also can be simplified by employing filter paper collected samples.

Adult↗
PubMedDate not supplied

[Study of the correlation between neutralization tests and hemagglutination inhibition tests in determinations of mumps virus antibodies].

In order to find out possibilities of wide application of the hemagglutination-inhibition (HI) test for determination of antibody to mumps virus, correlations between neutralization test (NT) and HI test was studied. Antibody to mumps virus was detected by parallel titrations of sera and gamma globulins in HI and NT tests in two experimental series each of which used various modifications of these tests. Statistically significant strong correlation was established between these tests.

Antibodies, Viral↗
PubMed1976

Comparison of a microneutralization test in cell culture and virus neutralization test in embryonated eggs for determining infectious bronchitis virus antibodies.

A microneutralization test (MNT) system utilizing cytopathic effect end points was effective in determing neutralization indexes for infectious bronchitis virus antibodies. The system is reproducible within 1 index unit at the 95% level of probability. Comparison of the MNT to tests in eggs resulted in a positive correlation (B =0.81), which was significant (P greater than 0.01). The quantitative dose-response relationship of the MNT is linear (P greater than 0.005), with the 95% prediction limits fitting between one 10-fold dilution.

Analysis of Variance↗
PubMed1975

The use of frozen cells in the microtitre serum neutralization test for infectious bovine rhinotracheitis.

Some parameters of the microtitre serum neutralization test were examined when using bovine fetal kidney cells derived from stocks stored in liquid nitrogen. In replicate tests with one serum there was no significant difference (p greater than 0.05) between titres calculated on the basis of cytopathic effect when either two or four wells were used per serum dilution. Also, there was no significant difference between titres calculated on the basis of a cell staining method when either two or four wells were used per serum dilution. When titres obtained by the 2-well-cytopathic effect method were compared with those obtained by the 2-well-stain method differences were not significantly different and it was concluded that the latter method using frozen cells constituted a practical and reproducible test. No significant titre variation occurred in cells serially passaged after having been frozen, or in cells derived from five different fetuses. Titres of sera from 41 cattle conformed to a log normal distribution pattern.

Cells, Cultured↗
PubMed1977

[Methods of using the antibody neutralization test in intestinal coli-infections].

Specificity and sensitivity of the antibody neutralization test intended for detection of the O-antigen of enteropathogenic escherichia were checked under experimental conditions. Only 3 strains of the Klebsiella genus proved to neutralize the antibodies to the enteropathogenic escherichia of the serological group O20:K84. In the rest of the cases a positive result was obtained only in homologous combinations. In comparative study of the microbial cultures of the infected feces on hard nutrient media by means of bacteriological and serological methods the latter was found to be more sensitive, capable of detecting the homologous O-antigen with the bacterial concentration of not less than 5-10(5) microbial cells per 1 ml.

Antigens, Bacterial↗
PubMed1978

A new microplate neutralization test for typing of herpes simplex virus.

A microplate serum neutralization test for estimation of complement-requiring neutralizing (CRN) antibody was established as the first step for simplification of typing of herpes simplex virus (HSV). When guinea pigs were immunized with type 2 HSV, the late sera could mostly differentiate the types of HSV better than hyperimmune rabbit sera, the CRN titer against the heterologous type 1 HSV being much lower than the homologous titer. Sera of guinea pigs immunized with type 1 HSV showed about the same level of cross reaction against type 2 HSV as did rabbit antisera. Guinea pig sera having minimal levels of cross reaction were selected, and their high dilution (1:160) and complement were added to serial 10-fold dilutions of virus in the microplate titration of virus infectivity. Selective reduction of virus titer by either antiserum could determine the type of HSV. No equivocal intermediate case was found among a number of stock strains including many fresh isolates. The typing result coincided with that determined by a modification of Yang et al's method based on virus titers obtained with Vero and primary chick embryo cells. The typing based on plaquing in chick embryo cells sometimes failed to identify type 1 HSV.

Animals↗
PubMed1975

[Antibody neutralization test in brucellosis].

The authors present the results of study of the antibody neutralization test in brucellosis with the use of erythrocytes sensitized with lipopolysaccharide. This test was shown to be highly specific and sensitive in detection of brucellae and brucellosis antigen in pathological material, food and objects of external environment.

Animals↗
PubMed1975

Antigenic relationships of group A arboviruses by plaque reduction neutralization testing.

Antigenic relationships of 20 group A arboviruses were assessed by the plaque reduction neutralization test, using highly specific hyperimmune mouse ascitic fluids and antisera. The existence of three complexes of group A viruses was verified. With rare exceptions, heterologous neutralization reactions were observed only among viruses in the same complex; however there were at least one or two immune reagents in each complex which were broadly cross-reactive within that complex.

Animals↗
PubMed1992

Antibodies to Puumala virus in humans determined by neutralization test.

An assay for detection of neutralizing antibodies to Puumala virus using 96-well microtiter plates (NT-ELISA) was developed and evaluated. The test proved to have similar sensitivity and specificity as an IgG ELISA and indirect immunofluorescence test, when screening 187 sera (with an antibody prevalence rate of 19%) from normal populations in an endemic area of Nephropathia epidemica (NE) in Sweden. NE-patients monitored for 2 years had neutralizing antibodies in early sera collected 1-4 days after the onset of disease with a continuous increase in neutralizing antibodies with time. Furthermore, high titers of neutralizing antibodies were detected 10-20 years post-infection. This neutralization assay was also evaluated as a screening method in the production of monoclonal antibodies. The format of the NT-ELISA makes it feasible to screen a large number of specimens with results similar to the standard plaque or focus-reduction neutralization tests.

Animals↗
PubMed1976

Varicella-zoster plaque assay and plaque reduction neutralization test by the immunoperoxidase technique.

A new plaque assay for the quantitation of varicella-zoster virus and a plaque reduction neutralization test for the determination of neutralizing antibody titer have been developed using the indirect immunoperoxidase technique. As compared with the classical plaque assay using a solid overlay, the test gives earlier results since plaque counting can be performed on day 3 after the inoculation of cell cultures. In six patients with zoster infection, neutralizing antibody titers ranged from 1:20 to 1:40 before the onset of infection and reached high levels (1:320 to 1:5,120) during the convalescent phase of the disease. Complement-fixing (CF) titers were all negative (less than 1:8) in prezoster serum samples from the same patients and ranged from 1:128 to 1:2,048 in the convalescent-phase sera. In the two cases in which late serum samples were available, neutralizing antibody titers matched the preillness levels, whereas CF titers dropped to undetectable levels. Neither neutralizing nor CF antibody was detected in two sera from individuals with no history of varicella-zoster infection. No differences in virus titers or neutralizing antibody titers were observed between the immunoperoxidase and the classical plaque assays. The appropriate characterization of reagent specificity is required before routine application of the test.

Antibodies, Viral↗
PubMed1978

[Detection of antigen of rickettsia of the tick group in bird droppings by antibody neutralization test].

The author presents methodical materials pointing to a possibility of using a micromethod of the antibody neutralization test for detection in bird pellets of the antigen of rickettsia referred to the Rocky Mountains spotted fever tick group. Specificity of the test, rickettsia antigen and sera was studied. The method is recommended for detection at the territory under study of circulation of the causative agent of tick-borne rickettsiosis by revealing the specific antigen in bird pellets.

Animals↗
PubMedDate not supplied

Serotyping of avian infectious bronchitis viruses by the virus-neutralization test.

The antigenic relationships of 12 strains of infectious bronchitis virus (IBV) were evaluated by a virus-neutralization procedure similar to that used in typing human rhinoviruses. Such a procedure consists of reciprocal neutralization tests performed by reacting 32-320 EID50 or plaque-forming units of virus with 20 antibody units of antiserum. Eight serologic groups were identified by chicken embryo assay, and 4 by plaque-reduction (90%). In general, serologic groupings were not distinct but reflected numerous intergroup relationships. The contrasting results exhibited by indicator systems are viewed as differences in the accuracy of the methods employed. It is suggested that before an IBV classification scheme can be proposed, agreement must be reached on the most suitable indicator system, techniques must be standardized, and reference viruses and antisera distributed to several institutions for comparison testing. In addition, cross-protection studies are needed to determine the importance of IBV serotypes and/or variants on vaccine efficacy.

Animals↗
PubMed1978

Neutralization tests for dengue and Japanese encephalitis viruses by the focus reduction method using peroxidase-anti-peroxidase staining.

Neutralization tests were made on 4 types of dengue (DEN) virus and Japanese encephalitis (JE) virus by incubation of serially diluted antisera and constant amounts of the viruses and then focus assay of surviving virus infectivity with peroxidase-anti-peroxidase (PAP) staining. Neutralization reactions were virtually completed in 2 hr on incubation of serum-virus mixtures at 28 C. A straight regression line was obtained on a probit chart by plotting the focus reduction rates at various dilutions of a given serum against the logarithm of the serum dilution used in the test. The slopes of the probit regression lines for the neutralization for DEN types 1 and 3 were similar, but differed somewhat from those for DEN type 2 and type 4. The slope of the line for JE virus was quite different from those for DEN viruses. Using these relations, the fifty percent focus reduction titer (FR50) of neutralizing antibodies of a given serum could be estimated from the focus reduction rates at several dilutions of the test serum when the latter was between 25-75% of the value of the control.

Animals↗