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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↗
PubMed1984

The titration of tetanus antitoxin II. A comparative evaluation of the indirect haemagglutination and toxin neutralization tests.

Serum samples from 77 guinea pigs immunized against tetanus have been titrated for tetanus antitoxin by a standardized indirect haemagglutination (IHA) test and the conventional toxin neutralization (TN) test. These sera were titrated before and after treatment of the sera with 2-mercaptoethanol (2-ME) by the IHA test using unfixed sheep erythrocytes and erythrocytes fixed with glutaraldehyde, formaldehyde and pyruvic aldehyde. The titres of these sera obtained by IHA using unfixed and glutaraldehyde-fixed sheep erythrocytes before treatment of the sera with 2-ME were two to six times higher than the TN titres, whereas the IHA-titres using formaldehyde- and pyruvic aldehyde-fixed sheep erythrocytes were 10 times higher than the TN titres in some of the sera. There was no statistically significant difference between TN and IHA titres using unfixed and glutaraldehyde-fixed sheep erythrocytes after the treatment of the sera with 2-ME.

Animals↗
PubMed1996

[Comparison between the plaque reduction neutralization test and the hemagglutination inhibition test in determination of human anti-measles antibodies].

In order to evaluate the difference between plaque reduction neutralization test (PNt) and hemagglutination inhibition (HI) test on human anti-measles antibodies, pre- and postimmunization sera collected from 328 infants aged 3-6 months who were immunized with Shanghai 191 measles vaccine, were detected by both methods. The results demonstrated that PNt was more sensitive than HI when they were used to measure the pre-immunization sera. No significant difference was found between these two methods when they were used to measure the post-immunization sera. PNt can be used to test low level maternal anti-measles antibodies in infants, especially for estimating the effect of maternal anti-measles antibodies on the immunogenicity of measles vaccine.

Antibodies, Viral↗
PubMed1986

Neutralization test for BK virus: plaque reduction detected by immunoperoxidase staining.

We developed an immunoperoxidase staining test to detect structural antigens of BK virus (BKV) in Vero cell cultures. This test was used to examine the neutralizing activity of human and immunized animal sera. It was shown that sera positive for BKV antibodies measured by hemagglutination inhibition test and enzyme-linked immunosorbent assay (ELISA) were able to prevent expression of BKV structural antigens in cell cultures. The correlation between titers in the hemagglutination inhibition test, levels of BKV IgG measured by ELISA, and the titers assayed by the immunoperoxidase neutralization test was high. We suggest that this type of test may be used instead of conventional neutralization tests for other viruses with slowly developing cytopathogenic effects.

Adult↗
PubMed1969

Yellow fever virus. II. Factors affecting the plaque neutralization test.

In studies on the factors and conditions influencing the yellow fever (YF) virus plaque neutralization test, 60 min was found to be the minimal time necessary for equilibration of the virus-antibody complex at 23 and 37 C. Maximal virus titers in the diluent controls and the pre- and postinoculation serum-containing mixtures occurred by the 60-min adsorption time. Serum neutralization indices also seemed to level by this time. Heating (56 C for 30 min) decreased the neutralizing capacity of serum. However, the slope of the neutralization curve was not affected. The addition of native (unheated) "serum factor" in the form of fresh guinea pig or monkey sera partially restored the neutralizing activity lost by heating in some, but not all, sera. Many sera contained nonspecific inhibitors of YF virus infectivity and neutralization. Preliminary studies with ether extraction suggest that these inhibitors are lipid in nature.

Adsorption↗
PubMed1985

Rapid focus reduction neutralization test of Japanese encephalitis virus in microtiter system. Brief report.

An improved rapid focus reduction neutralization test for Japanese encephalitis (JE) virus in microtiter system was developed. 96-well tissue culture plates were used for preparation of cell monolayers and PAP (peroxidase-antiperoxidase) staining technique was used for visualization of foci of infected cells. As the test has many advantages over other methods, it might be applied widely for rapid diagnosis and seroepidemiological studies.

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↗
PubMed1984

Enzyme-linked immunosorbent assay compared with neutralization tests for evaluation of live mumps vaccines.

Mumps-specific antibody levels before and after vaccination with live mumps vaccines were determined by enzyme-linked immunosorbent assay (ELISA) and neutralization tests. A correlation was found between neutralization titers and optical density in ELISA. However, postvaccination sera from some vaccinees who failed to seroconvert by neutralization contained significant levels of mumps-specific antibody detectable by ELISA. In some of these serum specimens, the antibody directed to the F polypeptide of mumps virus was predominant. Most sera positive in ELISA neutralized mumps virus upon the addition of fresh guinea pig serum to the virus-serum mixture.

Antibodies, Viral↗
PubMed2003

Power of neutrality tests to detect bottlenecks and hitchhiking.

The power of several neutrality tests to reject a simple bottleneck model is examined in a coalescent framework. Several tests are considered including some relying on the frequency spectrum of mutations and some reflecting the linkage disequilibrium structure of the data. We evaluate the effect of the age and of the strength of the bottleneck, and their interaction. We contrast two qualitatively different bottleneck effects depending on their strength. In genealogical terms, during severe bottlenecks, all lineages coalesce leading to a star-like gene genealogy of the sample. Some time after the bottleneck, once new mutations have arisen, they tend to show an excess of rare variants and a slight excess of haplotypes. On the contrary, more moderate bottlenecks allow several lineages to survive the demographic crash, leading to a balanced genealogy with long internal branches. Soon after the event, data tend to show an excess of intermediate frequency variants and a deficit of haplotypes. We show that for moderate sequencing efforts, severe bottlenecks can be detected only after an intermediate time period has allowed for mutations to occur, preferably by frequency spectrum statistics. Moderate bottlenecks can be more easily detected for more recent events, especially using haplotype statistics. Finally, for a single locus, the bottleneck results closely approximate those of a simple hitchhiking model. The main difference concerns the frequency distribution of mutations and haplotypes after moderate perturbations. Hitchhiking increases the number of rare ancestral mutations and leads to a more predominant major haplotype class. Thus, despite a number of common features between the two processes, hitchhiking cannot be strictly modeled by bottlenecks.

Algorithms↗
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↗
PubMed1996

Correlation between ELISA, hemagglutination inhibition, and neutralization tests after vaccination against tick-borne encephalitis.

The significance of IgG antibody levels determined by a binding assay (ELISA) was investigated as a surrogate marker for the presence of neutralizing and hemagglutination inhibiting antibodies in sera from individuals vaccinated against tick-borne encephalitis (TBE). To assess the extent of interference by flavivirus cross-reactive antibodies, sera from persons with a proven or suspected history of other flavivirus infections and/or vaccinations were also examined. An excellent and highly significant correlation was found between ELISA IgG units and the antibody titers obtained by the hemagglutination inhibition (HI) as well as by the neutralization test (NT), provided that there was no other exposure to flavivirus antigens except TBE vaccination. Yellow fever vaccination and/or dengue virus infections induced significant levels of antibodies reactive in the TBE ELISA and HI test, which did not exhibit, however, neutralizing activity against TBE virus. The phenomenon and problem of "original antigenic sin" was demonstrated in a TBE vaccinee with a history of previous flavivirus infections. TBE vaccination first induced a booster reaction resulting in a rise in the level of cross-reactive antibodies only, whereas TBE virus-neutralizing antibodies became detectable only after the third vaccination. It is concluded that the level of IgG antibodies determined by ELISA is a good marker for predicting the presence of neutralizing antibodies after TBE vaccination, but only in the absence of flavivirus cross-reactive antibodies. Otherwise, a neutralization assay is necessary for assessing immunity.

Animals↗