Conventional Neutralization Test Research Articles

Immunoradiometric assay of inhibitors of antihaemophilic factor A.

An immunoradiometric assay (IRMA) for determination of antibodies against f. VIII:C in haemophilia A was developed. The assay was based on competitive binding of radiolabelled anti-VIII:C and antibodies in the test material to immobilized VIII:C. Fifteen haemophiliacs with known inhibitors were investigated with the new method and with a conventional neutralization test. In 3 cases the inhibitors were detected only with the IRMA and in the other 12 there was good agreement between the inhibitor levels found with the two methods. It was also possible to demonstrate the antibodies in three non-haemophilic patients with acquired inhibitors. The IRMA, which can detect the antibodies down to a concentration of 0.02 inhibitor units per ml, is more sensitive than conventional neutralization tests and is thus of practical importance in the investigation of patients with low inhibitor titres.

Role of virus strain dm conventional and enhanced measles plaque neutralization test

A low-passage Edmonston strain of measles virus gave on the average four-fold higher antibody titers than two high-passage strains of Edmonston virus when used in a virus plaque neutralization test. Heterologous anti-human immunoglobulin did not affect antibody liters obtained with the lowpassage virus but enhanced antibody titers obtained with the high-passage viruses on the average eight-fold. These differences in virus sensitivity to neutralization and neutralization potentiation by anti-immunoglobulin were interpreted as being possibly due to differences in density or accessibility of the functional antigens of measles virus. The conventional plaque neutralization test utilizing the low-passage Edmonston virus was about 10 times more sensitive than the virus CPE-neutralization test, 60 times more sensitive than the measles hemagglutination-inhibition test and 220 times more sensitive than the measles complement-fixation antibody test.

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.

Sensitive neutralization test for virus antibody

A sensitive mumps virus plaque neutralization test has been developed based on the potentiation of virus-antibody complexes by heterologous anti-immunoglobulins (AIG). The enhanced neutralization test was approximately 100 times more sensitive than the conventional neutralization test or the hemagglutination-inhibition test. Using AIG against human immunoglobulin G (IgG) or human IgM permitted determination of the relative titers of the two classes of mumps antibody. The test does not require special equipment or expertise and can be readily introduced in virological laboratories.

High prevalence of antibodies to BK virus, an SV40-related papovavirus, in residents of Maryland.

The prevalence of HAI antibodies to BK virus in sera of Maryland residents increased from 50% to 100% between the ages of three and 10-11 years, and then declined to 67% in the group aged 35 years or older. Examination of sera for antibodies by indirect fluorescent antibody tests and by conventional and immunofluorescence neutralization tests supported the results of HAI tests. Infection with BK virus appears to be common in early childhood.

Hand, foot and mouth disease: An outbreak with interesting virological features

<h2>Summary</h2> During 1969-1970, 12 strains of virus were isolated in cell culture from 9 patients with hand, foot and mouth disease investigated at Fairfield Hospital for Communicable Diseases, Melbourne. The strains, although acid stable and producing an enterovirus-like cytopathic effect, could not be neutralized, in conventional tube neutralization tests, by antisera to any of the prototype enteroviruses. Immunodiffusion studies and mouse neutralization tests performed on selected isolates showed them to be strains of Coxsackie A16 virus. When suspensions of the strains which had proved difficult to neutralize were treated by sodium deoxycholate or filtered, the difficulty was overcome, suggesting that it had been due to the presence of viral aggregates.

Studies on intratypic variants of coxsackie B 1 virus.

Six virus isolates recovered from clinical material and producing in inoculated infant mice histopathological changes resembling those produced by coxsackie B viruses were investigated. On the basis of cross neutralization tests all six isolates were found to be antigenically interrelated but distinct from all existing enteroviruses, including Public Health Laboratory (PHL) prototype coxsackie B 1 strain. All six isolates, however, were neutralized by the WHO reference antiserum to coxsackie B 1, Conn-5 strain, although the antisera to these isolates failed to neutralize Conn-5 strain. Conventional and kinetic neutralization tests revealed a considerable degree of antigenic heterogeneity among these isolates as well as antigenic difference between the two prototype strains, PHL and Conn-5. In the light of current definition, these six isolates, because of their narrower antigenic spectrum, as compared to prototype Conn-5 strain, cannot be considered as prime strains of coxsackie B 1 virus. The present study emphasizes the need for reexamination of present definition of “prime” and “prototype” strains. The findings also indicate the importance of using the enterovirus strains with the broadest antigenic spectrum in identification work.

Detection of Anti-Phage Antibody by Passive Hemagglutination

Abstract A hemagglutination test capable of detecting 2.5 × 10-5 µg of antibody nitrogen was applied to the measurement of anti-T2 phage activity during early phases of the antibody response induced in vivo or in vitro. Using this test serum antibody was detected within 24 hr of immunization and rose rapidly, whereas conventional neutralization tests indicated a slow increase in activity. Neutralization tests in the presence of complement indicated a rise in activity with time that paralleled the increase in hemagglutination activity. Antibody induced in vitro was detected by the conventional neutralization test only with difficulty but was readily demonstrable by the hemagglutination test.

Immunoelectrophoretic Studies of the California Encephalitis Virus Group

Abstract Immunoelectrophoretic studies of the California encephalitis group (CEV) of arboviruses were carried out. Both single and multiple injection rabbit antisera prepared against the various antigens were used in several agar-buffer-pH systems. Multiple shared antigens were demonstrable among BFS-283 (CE) and all other members of the group except Keystone (KEY) and trivittatus (TVT), thus showing a close antigenic relationship among the majority of members. However, only a minor common antigen was shared between CE and the latter two, indicating a distant antigenic relationship. Guaroa, a member of the Bunyamwera (BUN) group shown by the more conventional neutralization and hemagglutination tests to be related to the CEV group, was found to show a common minor antigen with all members of the CEV group except TVT. At least two common antigens were shared with the latter. Based on this present work and immunodiffusion studies previously reported, it is suggested that the CEV group be considered as a separate group with at least three types. These would be represented by prototypes CE, TVT and KEY. More exhaustive antigenic studies may eventually define additional types and further elucidate the extent of relatedness among members of the CEV and BUN groups.

Neutralization anti-IgG test for antisera to Venezuelan equine encephalomyelitis.

SUMMARY A precise, reproducible, and sensitive serum neutralization test was developed to estimate Venezuelan equine encephalomyelitis neutralizing antibody activity within 24 hr. The test depends on the interactions of virus with antiviral globulins and of the resultant complexes with anti-gamma globulin (IgG) antibodies. The 50 % serum neutralizing dilutions were calculated from the reduction of fluorescent cells in McCoy cell monolayers resulting from the neutralization of infective virus by antibody. In comparative estimates of the neutralizing activity of human and monkey antisera, the sensitivity of the serum neutralization anti-IgG test was several hundredfold greater than that of the conventional serum neutralization test in mice.

Microneutralization test for the reoviruses. Application to detection and assay of antibodies in sera of laboratory animals.

SummaryThe problem of determining the specificity of hemagglutination-inhibiting activity for reovirus type 3 seen in mouse, hamster and rat sera examined as part of a mu-rine virus monitoring program, together with the need for a sensitive and efficient technic for detection of reovirus antibodies in the sera of other laboratory animals, led to the development of a microneutralization technic. The test, conducted in a HeLa cell system in disposable microplates, is a modified metabolic inhibition procedure which permits reading of results colorimetrically. The results obtained in microneutralization tests showed good correlation with those obtained in conventional neutralization tests conducted in tube cultures of monkey kidney cells. The technic was found to be suitable for detection of antibodies to all 3 reovirus types in sera of a variety of species, and it is particularly useful for monitoring rodent colonies for reovirus type 3 infections. HI tests appeared to possess less specificity than neutraliz...

Sensitivity and Error Limits of Two Tests for Distemper Virus Neutralizing Antibody: A Conventional Neutralization Test and the “Single Dilution-Probit Test”

The sensitivity and error limits of a conventional in ovo neutralization test for antibody to distemper virus were compared with the same parameters of a single dilution-probit test for neutralizing antibody. With the former test, antibody was demonstrable in ferrets 8 days following a single subcutaneous injection of virus while probit analysis of data from the single dilution test revealed the appearance of antibody as early as 4 days post-immunization. The error terms of the single dilution test were relatively large as compared to those of the conventional test for antibody. Distinctly biphasic antibody responses were observed in ferrets following a single subcutaneous injection of distemper virus.

ANTIGENIC RELATIONSHIP BETWEEN ECHOVIRUS TYPES 29 AND 32.

SummaryAn antigenic relationship has been demonstrated between the newly classified echovirus types 29 and 32. The amount of crossing seen in conventional tube neutralization tests was relatively minor, but fairly high reciprocal titers were observed in plaque reduction neutralization tests. In cross hemagglutination-inhibition and complement fixation tests these two viral types were virtually indistinguishable. The question arises as to whether these two new echovirus types should be classified as distinct immunotypes or whether they represent antigenic variants of a single viral type.

Identification of a cytopathogenic agent called U-virus recovered from patients with non-diphtheritic croup and from day-nursery children.

An identification of the virus called U-virus has been presented and the results have shown this virus to be antigenically related to ECHO-11-virus. This was ascertained by conventional neutralization tests in tissue cultures and by the plaque reduction test as well as by haemagglutination-inhibition and complement-fixation tests.

Immuno-inactivation of poliovirus.

The term immuno-inaotivation as distinct from neutralization is used to designate a technic by which the reaction between virus and antibody as well as by this reaction possibly induced changes in the virus are allowed to proceed to completion after which the residual virus activity is determined. The degree of inactivation was found to be inversely proportional to the amount of virus added. Maximum sensitivity wan thus obtained when the virus dose was reduced to the lowest possible limit. With due regard to this fact the technic was found to be 100 times more sensitive than the conventional neutralization test.