Solid-phase radioimmunoassay of rubella virus immunoglobulin G and immunoglobulin M antibodies

Evaluation of microparticle enzyme immunoassays for immunoglobulins G and M to rubella virus and Toxoplasma gondii on the Abbott IMx automated analyzer

The ability of the Abbott IMx automated analyzer to detect immunoglobulin G (IgG) and IgM antibodies to rubella virus and to Toxoplasma gondii was compared with the abilities of RUBAZYME, RUBAZYME-M, ABBOTT TOXO-G enzyme immunoassay, and ABBOTT TOXO-M enzyme immunoassay, respectively. Specimens that produced discordant results were evaluated by RUBACELL II, Behring Enzygnost-Rubella enzyme-linked immunosorbent assay, Behring Enzygnost Toxoplasmosis/IgG, and bioMerieux Toxo-ISAGA (immunosorbent agglutination assay), respectively. After resolution of discordant results, IMx Rubella IgG, IMx Rubella IgM, IMx Toxo IgG, and IMx Toxo IgM antibody assays had sensitivities of 99.9, 100, 98.0, and 100%; specificities of 98.9, 99.0, 97.5, and 98.7%; and accuracies of 99.8, 99.3, 97.8, and 98.8%, respectively.

Recent rubella virus infection indicated by a low avidity of specific IgG

Rubella-specific IgG in acute-phase sera produces a characteristically altered zone termed "soft hemolysis" in the radial hemolysis test. Here, the soft hemolysis was shown to be a product of the purified IgG1 subclass isolated from acute-phase sera. In contrast, ordinary hemolysis was produced by IgG1 isolated from sera of previous rubella immunity, indicating that the subclass composition of IgG was not involved in the mechanism of soft hemolysis. A novel type of solid-phase immunoassay was developed for the avidity of virus-specific IgG. Acute-phase IgG (with soft hemolysis) was dissociated from rubella antigen in an enzyme immunoassay (EIA) test by hydrogen-bond disrupting agents under conditions where IgG of previous immunity (showing ordinary hemolysis) remained mostly bound. These data suggest that the mechanism of soft hemolysis is the avidity of rubella-specific IgG. The new quantitative avidity EIA was tested with sera taken from 169 subjects. Recent infection could be shown from sera taken weeks or months after primary rubella.

First trimester prenatal diagnosis of congenital rubella: a laboratory investigation

Acute primary maternal infection with rubella virus during pregnancy often, but not invariably, leads to the congenital rubella syndrome. Diagnosis by detection of virus specific IgM in the mother is not always possible, and in those cases in which IgM is detected the fetus has not necessarily also been infected. A method for direct, prenatal detection of fetal infection would allow more accurate early diagnosis of congenital rubella syndrome. In this study a case of suspected preconception rubella infection that was not referred until 14 weeks after the appearance of a rash was studied to determine whether a retrospective serological diagnosis of primary rubella could be made, and whether direct evidence of fetal infection could be obtained from a chorionic villus biopsy specimen by detecting virus specific antigens or ribonucleic acid (RNA) sequences. Monoclonal antibodies and a cloned complementary deoxyribonucleic acid probe were used successfully to detect antigens to rubella virus antigens and RNA sequences in the chorionic villus biopsy specimen, which was taken at 15 weeks' gestation. This method should serve as a new approach to the diagnosis of congenital rubella syndrome in utero.

Evaluation of a rapid passive hemagglutination assay for anti-rubella antibody: comparison to hemagglutination inhibition and a vaccine challenge study

A rapid passive hemagglutination assay (Rubaquick) was developed that detects antibody to rubella virus in serum specimens. The test result is read visually after an incubation period of 15-30 minutes. When compared with a hemagglutination inhibition assay, the Rubaquick assay results obtained from 1,470 sera were greater than 99% specific, sensitive, and accurate. Studies of 179 paired serum specimens obtained before and 27 days after rubella vaccination showed that if antibody was detectable by the Rubaquick assay in the prevaccination specimens, the vaccine induced a secondary response consisting of increasing IgG antibody reactivity in the absence of a positive IgM response. In contrast to the positive prevaccination specimens, a negative prevaccination result was associated with IgM antibody in 98 of the 133 postvaccination specimens. Seroconversion was noted in all cases in which the prevaccination specimen was negative by the Rubaquick assay.

Comparison of various serological methods and diagnostic kits for the detection of acute, recent, and previous rubella infection, vaccination, and congenital infections

The antibody development after natural rubella infection and rubella vaccination has been followed in 802 sera from 493 patients and 71 sera from 22 vaccinees. Also examined were 67 sera from 28 infants with rubella embryopathy and sera from 50 children with presumed prenatal infection. In addition, 777 sera from 641 patients tested for routine rubella diagnosis were studied. Anamnestic information was available from all these patients. These sera were assayed for IgM antibody detection by sucrose density gradient (SDG), the commercial ELISAs (Enzygnost IgM and Rubazyme M), and the non-commercial anti-my-hemadsorption immunosorbent technique (HIT). For the determination of IgG antibodies the hemagglutination inhibition test (HAI), the commercial ELISAs (Enzygnost IgG, Rubazyme), and a single radial hemolysis test (SRH) were used. The SDG and HIT were less sensitive for IgM antibody detection than the two ELISAs, particularly when IgM concentrations were low. In total 26.5% of the IgM results with the newer tests were discordant with SDG, but only 0.5-1.3% of these results were not explicable when the clinical data was considered. Problems were encountered with all IgM assay systems used. For the detection of rubella antibodies after acute infection and vaccination the ELISA Enzygnost IgG was as sensitive as the HAI whereas the ELISA Rubazyme and SRH detected antibodies with some delay. Corresponding results with all tests were found more than 25 days after acute infection and more than 50 days after vaccination. All methods can be used for detection of antibodies in infants with rubella embryopathy. The results of this study suggest that certain combinations of tests can be used for the reliable detection of rubella infection.

Subcellular fractions in rubella immunoassays

Rubella virus-infected cells were fractionated by differential and sucrose gradient centrifugations. Rubella virus antigens distributed into all fractions but particulate material in the 100,000 x g pellet was shown to be enriched about two-fold for rubella virus antigen. Similarly, sucrose gradient fractions for rough endoplasmic reticulum and smooth cellular membranes were enriched for rubella virus antigens. The 100,000 x g pellet and the isolated cellular membranes proved to be useful when different fractions were used in solid-phase immunoassays for rubella virus-specific IgG or IgM. These fractions were equal in quality of the semipurified rubella virus preparations in the IgG assays but inferior to those in the IgM assays. However, simultaneous use of 35/25% sucrose fractions from infected and non-infected cells reveals non-specific binding of IgM to the antigens and renders the IgM tests more specific for rubella virus.

Evaluation of a latex agglutination test for detection of antibodies to rubella virus in selected sera

A new latex agglutination test for rubella virus was used to test sera with a hemagglutination inhibition titer of less than or equal to 8 (97 specimens) or greater than or equal to 256 (158 specimens). Maximum latex agglutination test sensitivity was achieved when low-titer sera were tested undiluted and high-titer sera were diluted (1:10). A modification of the protocol of the manufacturer resulted in a latex agglutination-hemagglutination inhibition agreement of 96.7%.

Intrathecal immune responses in mumps meningitis patients

The in vitro 3H-thymidine incorporation of peripheral blood (PB) and cerebrospinal fluid (CSF) lymphocytes from 11 mumps meningitis patients was studied after stimulation with non-specific mitogens and microbial antigens. Although corresponding viral antibodies were always found in the CSF of seropositive patients by a sensitive radioimmunoassay, their intrathecal synthesis was directed mainly against mumps virus. Most of the patients had PB lymphocytes that reacted on stimulation with phytohaemagglutinin (PHA) or pokeweed mitogen (PWM), but a smaller number of them had reactive CSF cells. Only four patients showed stronger responses to PHA in the CSF than in PB. Most patients had mumps-reactive lymphocytes in PB but only two of them in the CSF. In contrast, these patients more often had increased CSF cell reactivity when tested with purified protein derivative, measles, and herpes simplex virus antigens. The results could not be explained by a damaged blood-brain barrier alone but may reflect the immunological status of the brain compartment in these patients.

Rubella serology: a comparison of four methods for exclusion of non-specific serum inhibitors

The ability of the pyrogenic silica Aerosil 380R to exclude non-specific serum inhibitors (NSI) of rubella virus haemagglutination was evaluated. The developed procedure was compared with the kaolin, heparin/MnCl2 and dextran sulphate/CaCl2 methods. Aerosil and kaolin were found superior for the elimination of non-specific inhibitors and high density lipoproteins (HDL). The other methods left NSI and HDL in a majority of the sera, occasionally in high titres. Aerosil seemed to be somewhat more efficient than kaolin in NSI and HDL exclusion. The Aerosil method offers the opportunity to detect sera with rubella antibody titres less than 10. Among eight such sera, six were shown to contain rubella antibodies, while two were false positives.

Autoantibodies to an epidermal protease inhibitor in skin diseases

Solid phase radioimmunoassay for measurement of autoantibodies in human sera to an epidermal protein is presented. The protein purified from normal human epidermis is inhibitory to SH-dependent protease and its molecular weight is about 13,000. Antibodies were detected in 139 of the 4,400 sera collected from dermatological patients. Most of the patients suffered from wide-spread eczematous conditions. It is suggested that the antibodies are secondary to the inflammatory conditions, but they may exacerbate or delay the course of the disease.

Immunoglobulins M and G to varicella-zoster virus measured by solid-phase radioimmunoassay: antibody responses to varicella and herpes zoster infections

Both immunoglobulin M (IgM) and IgG antibodies to varicella-zoster virus (VZV) were detectable in a solid-phase radioimmunoassay with 125I-labeled goat antisera to human immunoglobulins. Primary infection with VZV was associated with early production of IgM and IgG antibodies and rapid development of lymphocyte transformation to VZV antigen. Among eight subjects with varicella tested 1 to 4 days after onset, seven patients had IgG and six patients had IgM antibodies; all patients had both IgG and IgM antibodies within 7 days. An IgM response was documented by radioimmunoassay in 18 of 26 patients with herpes zoster. VZV antibodies could be assayed by radioimmunoassay in unfractionated serum with commercial goat antisera to human immunoglobulins and commercial VZV antigen. VZV-specific IgG binding was present in all sera from 42 subjects with a VZB antibody titer of greater than or equal to 1:8 as determined by indirect immunofluorescence and cellular immunity to VZV as determined by lymphocyte transformation and who had had varicella at least 20 years before testing. The geometric mean titer was 1:6,309, and titers were greater than or equal to 1:16,384 in 20 subjects. Antibody was present as determined by radioimmunoassay in 14 samples negative by complement fixation and in five samples negative by complement fixation and immune adherence hemagglutination. No specific binding was observed in 21 sera from subjects who were not immune to VZV as determined by indirect immunofluorescence or lymphocyte transformation despite the presence of herpes simplex or cytomegalovirus antibody indicated by complement fixation in 15 sera. High titers of VZV IgM antibody were detected in unfractionated sera despite the presence of high titers of VZV IgG antibody. The VZV radioimmunoassay provided a sensitive and practical method for measuring VZV IgG and IgM antibodies.

Rubella antibody determination from heparinised finger-tip blood by single radial haemolysis and enzyme immunoassay

Rubella antibodies were determined by single radial haemolysis (SRH) and a micromodification of enzyme immunoassay (EIA) of samples of heparinised finger-tip blood or plasma collected into transportable vials, and the results were compared with antibody titres obtained from conventional samples of venous serum. The antibody titres of finger-tip specimens gave a high correlation with those of venous serum. For SRH only 5 microliters of heat-inactivated finger-tip plasma was needed, and for EIA only a single dilution, 1:100, in duplicate, of heparinised finger-tip plasma or while blood was sufficient. The minimal inconvenience in sample collection makes the finger-tip test particularly suitable for large-scale immunity screening when assessing the need for, or efficacy of, rubella vaccination.

Detection of enterovirus specific IgG and IgM antibodies in humans by an indirect solid phase radioimmunoassay

The development of a solid phase radioimmunoassay which is able to detect virus-specific IgG and IgM antibodies in serum specimens from patients with enterovirus infections is described. Viral antigen partially purified from infected tissue culture fluid was absorbed passively to individual polystyrene microtiter wells. Dilutions of sera were incubated on these antigens and bound anti-viral antibodies were monitored by the addition of 125-iodine labeled anti-human-IgG or anti-human-IgM antibody. Specificity of the assay to detect virus-specific IgM antibody was ensured by highly specific anti-IgM antibody which did not cross react with IgG and 2-mercaptoethanol sensitivity of IgM antibody titers. Changes of IgM antibody titers clearly indicated a current infection by that virus strain which was isoalted as etiological agent. Advantages and restrictions of the introduced radioimmunoassay are discussed.

Enzyme-linked immunosorbent assay for mumps and parainfluenza type 1 immunoglobulin G and immunoglobulin M antibodies

A solid-phase enzyme-linked immunosorbent assay (ELISA) for detection of mumps and parainfluenza type 1 antibodies (immunoglobulin G [IgG] and IgM classes) is described and compared with the conventional complement fixation (CF) test. A highly positive correlation was found between mumps IgG ELISA and the mumps CF test, whereas parainfluenza type 1 IgG ELISA had only a moderate positive correlation with the respective CF test. Mumps IgM antibodies could be demonstrated in all patients with serologically verified and clinically typical (parotitis, meningitis, or orchitis) mumps virus infection, but not in patients with rises in parainfluenza CF titers. Mumps IgM was already present in the acute-phase sera if they were not taken during the first 2 days after onset of disease. Mumps IgM was also found in some paired sera that were taken too late to demonstrate any significant increase in the antibody titers by CF. Therefore, mumps IgM ELISA provides an improvement over the conventional laboratory diagnosis of mumps infection, since the measurement of specific IgM antibodies in a single serum by ELISA is diagnostic, rather than the identification of a fourfold or greater rise in CF antibody titer. An unexpected finding was that parainfluenza type 1 IgM antibodies could not be demonstrated by ELISA in paired sera with rises in parainfluenza CF titers, suggesting a different antibody response from that occurring in mumps infection.

Comparison of immunofluorescence and radioimmunoassay for detecting IgM antibody in infants with the congenital rubella syndrome

Immunofluorescence (IF) and radioimmunoassay (RIA) have been compared as methods for detecting IgM antibody in 124 infants with confirmed or suspected congenital rubella. IF was used to test sucrose density gradient fractions and RIA to test fractions and whole serum. When fractions were tested IF and RIA were equally specific and distinguished clearly between IgM and IgG, but RIA was the more sensitive method. The RIA titre in whole serum was always greater than in the peak IgM fraction and there was no evidence that testing the serum, rather than the fraction, could result in failure to detect IgM. With some sera RIA gave low titres which became negative after absorption with IgG-coated latex beads. The mechanism of this 'false positive' effect, which may have been due to IgM with anti-IgG activity, was not investigated, but if it can be removed by absorption it need not reduce the specificity of the test. During the first 6 months of life IgM antibody was detected by RIA in 30 out of 32 unfractionated sera and by IF in fractions from 28 of these. After the age of 6 months IgM was found progressively less frequently and the greater sensitivity of RIA became a more obvious advantage: 17 out of 60 specimens were positive by RIA and 11 of these were negative by IF. RIA testing of whole serum appears to be an economical, specific and sensitive method for detecting IgM antibody in congenital rubella, of particular value when the titre of antibody is low.

Detection of immunoglobulin M antibodies to hepatitis A virus by enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay for the detection of immunoglobulin M (IgM) antibodies to hepatitis A virus is described. The test uses the principle of binding of IgM antibodies to anti-IgM-coated microtiter plates to determine whether the IgM antibodies attached have specificities for hepatitis A virus. In three patients with hepatitis type A followed up to 12 months, IgM antibodies to hepatitis A virus could be demonstrated from the onset of illness and during the following 2 to 3 months. When acute-phase sera from 48 patients with acute hepatitis were tested, IgM antibodies to hepatitis A virus could only be demonstrated in 18 patients previously classified as type A, whereas 30 patients with type B and non-A non-B hepatitis were negative. IgM antibodies to hepatitis A virus could not be demonstrated in 108 normal sera nor in 55 sera containing rheumatoid factor. These results indicate that the enzyme-linked immunosorbent assay for IgM antibodies to hepatitis A virus is useful in the serodiagnosis of acute hepatitis type A on a single serum sample taken during the acute phase of illness.

IgA antibody response in acute rubella determined by solid-phase radioimmunoassay

A solid-phase radioimmunoassay (RIA) for detecting rubella virus IgA serum antibodies was developed. Purified rubella virus grown in roller cultures of Vero cells was adsorbed onto polystyrene beads. The coated beads were then incubated with dilutions of serum, and rubella IgA antibodies which attached to the virus antigen on the solid-phase were subsequently detected with 125I-labelled anti-human-alpha antibodies. The specificity of the iodinated anti-human immunoglobulins was confirmed by RIA analysis of fractions obtained by chromatography of an early convalescent serum on an agarose column. A complete separation of IgM, IgA, and IgG was observed. A total of 144 serial serum specimens from 31 adult patients with an acute rubella infection were tested for rubella IgA antibodies, and the results were compared with the RIA IgG and IgM titres reported earlier from the same specimens. The RIA IgA response was detected in each of the 31 patients and the IgA antibodies appeared almost simultaneously with the IgG and IgM antibodies. The maximum titres, which were lower than the IgG and IgM titres, were reached in about 1 week after the onset of rash. In 6 patients out of 31 the IgA antibody response was transient and persisted approximately two months, while in the remaining 25 patients the IgA antibodies persisted throughout the study period of more than 5 months. The results obtained indicate that the presence of rubella IgA antibodies in serum is not an indication for a recent rubella infection.

Solid-phase radioimmunoassay of serum immunoglobulin A antibodies to respiratory syncytial virus and adenovirus

A solid-phase radioimmunoassay for detecting respiratory syncytial virus and adenovirus serum immunoglobulin A (IgA) antibodies was developed. An antigen consisting of purified adenovirus type 2 hexons or a crude lysate of respiratory syncytial virus-infected cells was first adsorbed onto polystyrene beads. The coated beads were then incubated with dilutions of serum, and IgA antibodies which attached to the solid-phase virus antigen were subsequently detected with 125I-labeled anti-human alpha antibodies. The anti-human alpha antibodies used were isolated by immunosorbent chromatography from rabbit antiserum produced by immunization with IgA purified from serum of an IgA myeloma patient. A total of 46 serum specimens from 13 patients with respiratory syncytial virus infections and 10 patients with adenovirus infections were tested. Complement fixation, homologous IgG and IgM radioimmunoassay, and heterologous IgA radioimmunoassay testing were also done. Specific values higher than 10,000 cpm were often reached with convalescent serum specimens, and positive-to-negative serum binding ratios of 50 or more were frequently obtained with lower serum dilutions. IgA titers of convalescent sera were from 1,000 to 16,000, and with few exceptions a fourfold or greater rise in the IgA titer was detected in the homologous IgA radioimmunoassay.

Method for rapid separation of immunoglobulin M from immunoglobulin G antibodies by using reorienting gardients in vertical rotors

The parameters for the use of reorienting gradients in vertical rotors for rapid separation of immunoglobulin M from immunoglobulin G on a preparative scale for the rapid diagnosis of infectious diseases are described.

Measurement of immunoglobulin M (IgM), IgG, and IgA antibodies against Yersinia enterocolitica by enzyme-linked immunosorbent assay: persistence of serum antibodies during disease

An enzyme-linked immunosorbent assay for the detection and quantitation of human immunoglobulin M (IgM), IgG, and IgA antibodies against Yersinia enterocolitica is described. Formalinized or heat-treated bacteria were adsorbed onto specially designed microcuvettes, and antibodies were allowed to attach to the antigen-coated cuvettes. Rabbit anti-human mu, anti-human gamma, and anti-human alpha antisera were allowed to react with human antibodies, and these class-specific anti-immunoglobulins were detected by alkaline phosphatase-labeled swine anti-rabbit IgG. A total of 423 sera were tested. The results obtained with the enzyme-linked immunosorbent assay were compared with the results of the conventional tube agglutination test. Persistence of different antibodies was studied in six patients. Antibodies of the IgM class persisted only for 1 to 3 months after onset of the disease; thus the occurence of IgM-class Yersinia antibodies in a single sample indicates a recently acquired infection. The persistence of the IgG- and IgA-class antibodies was variable and not parallel with each other. Remarkably, all three patients in which the disease was complicated with arthritis had IgA-class Yersinia antibodies at the end of the follow-up period of 9 to 14 months, and in those without arthritis the IgA-class antibodies disappeared within 3 months after onset of the disease.

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.

OC43 strain-related coronavirus antibodies in different age groups

Serum antibodies against human coronavirus OC43 in different age groups were measured by complement fixation (CF), haemagglutination inhibition (HI), radial diffusion haemolysis-in-gel (HIG), and solid-phase radioimmunoassay (RIA) methods. Antigen grown in suckling mouse brain was used in all tests. Results obtained by the CF and HIG tests, and the RIA, were in good agreement with regard to the presence or absence of antibodies. Similar results were also obtained with the HI test if nonspecific haemagglutination inhibitors were first removed by treatment with phospholipase C and only titers of 1:20 or greater were considered positive. Children 6--23 months of age (n = 45) were without measurable coronavirus antibodies in all four assays. A rapid increase in the prevalence of antibodies then occurred in subsequent age groups, and practically all persons 6 years of age or older were found to have OC43 antibodies as measured by the HIG test or the RIA. The mean antibody levels determined by these two methods continued to increase, however, up to the age group of 10--14 years. This increase in antibody levels after the initial antibody incidence plateau may be due to boosting effects caused by related coronavirus strains, since OC43 antigens are known to cross-react with antibodies induced by other human coronaviruses. Taken together, these data suggest that OC43 virus, or an antigenically related coronavirus strain, is very common in Finland.

Sensitive solid-phase radioimmunoassay for detection of human immunoglobulin G antibodies to varicella-zoster virus

A sensitive solid-phase radioimmunoassay for detection of antibodies to varicella-zoster virus (VZV) is described. The antigen consisted of a sonically disrupted extract of VZV-infected human embryo cells. 125I-labeled rabbit anti-human immunoglobulin G (IgG) specific for the Fc portion of human IgG was used to detect human IgG bound to viral antigen. With this technique, 193 human sera were evaluated for their IgG antibody titer against ZVZ. Subjects included 62 healthy adults, 33 young children (12 healthy), and 49 patients. Titers obtained by the radioimmunoassay were compared with those obtained by indirect fluoresence antibody staining of membrane antigen. The radioimmunoassay technique described gave titers approximately 5 X 10(4) times higher than those shown by indirect fluorescence. It can be used for routine diagnosis, but is especially suited to determining immune status to VZV, as defined by presence or absence of antibodies to the virus; for epidemiological studies; or for determining patients at risk who are exposed to the virus. No heterotypic titer rises to VZV were observed in sera with fourfold or greater rises to Epstein-Barr virus or cytomegalovirus. Sera of eight subjects with fourfold or greater titer rises to herpes simplex virus reacted in various ways: in six cases no significant change occurred in titer to VZV; one had a significant decrease in titer by the radioimmunoassay; and one had a significant increase. Possible reasons for these titer changes are discussed.

Selective detection of IgM-antibody against core antigen of the hepatitis B virus by a modified enzyme immune assay

IgM antibody against core antigen of the hepatitis B virus (anti-HBc IgM) was selectively determined by a new enzyme immunoassay (EIA). Microtiter plates were coated with anti-human micro chain immunoglobulin. On addition of serum IgM is bound by a factor of about 4,000 more than IgG. After removing the sample, HBcAg is added to the IgM-coated surface. Binding takes place if the IgM contained anti-HBc and was demonstrated by the aid of a conjugate made from anti-HBc IgG and horse radish peroxidase. Quantitation may be achieved without testing a dilution series. The assay was not disturbed by a large excess of anti-HBc IgG in the sample and rheumatoid factor did not produce false-positive results, provided the sample was diluted in an excess of aggregated IgG. The diagnostic relevance of the assay was demonstrated in selected cases of acute hepatitis B. Rapid diagnosis of acute hepatitis B infection is therefore now possible in those cases whihc are HBsAg-negative but anti-HBc-positive.

Enzyme-linked immunosorbent assay for determination of rubella IgG antibodies

A rubella virus antigen suited for enzyme-linked immunosorbent assay (ELISA) was grown in cultures of BHK/21/13 cells and purified and concentrated by membrane and ultrafiltration. This antigen was used in a semi-automated ELISA for determination of rubella IgG antibodies. The ELISA and the haemagglutination-inhibition (HI) test were compared in a study of 825 human sera. A close correlation was found between the results obtained by the two methods. Antibodies were, however, detected with ELISA in approximately 15% of the sera found negative in the HI test. The presence of antibodies was confirmed by the results of HI tests of the serum fractions of 19 sera separated by rate zonal ultracentrifugation. The EISA procedure employed in the present study was highly sensitive and allowed a precise quantitation of the antibodies by examination of one single serum dilution. ELISA was less time-consuming than the HI test and suited for routine laboratory use.

IgM-class rheumatoid factor interference in the solid-phase radioimmunoassay of rubella-specific IgM antibodies

The interference of IgM-class rheumatoid factor (RF) in the solid-phase radioimmunoassay (RIA) of rubella virus IgM antibodies was studied. Acute rubella infections did not significantly activate RF. False-positive rubella antibody results were obtained, however, when patients with raised RF levels were tested. If a low rubella IgG antibody titre was present, a high level of RF was required to cause a false-positive IgM result; conversely, in sera with high IgG titres, only a low level of RF was required for interference. Although the false-positive IgM titres obtained were generally low, thet did show a positive correlation to both RF levels and rubella IgG titres. False-positive results were successfully avoided by removing the RF by absorption with heat-aggregated human gamma globulin. The absorption procedure did not affect true rubella IgM antibody titres.

Immunological response to infection with human reovirus-like agent: measurement of anti-human reovirus-like agent immunoglobulin G and M levels by the method of enzyme-linked immunosorbent assay

The report describes the development of an enzyme-linked immunosorbent assay (ELISA) for the detection of antibodies against the human reovirus-like agent of infantile gastroenteritis (HRVLA). This ELISA system proved to be four times as sensitive as the standard anti-HRVLA fluorescent-antibody assay and ten times as sensitive as the standard anti-HRVLA complement fixation assay. In addition, the ELISA was capable of determining immunoglobulin G (IgG) and IgM subclasses of anti-HRVLA antibody using a single dilution os serum. With this assay, it was discovered that 11 of 21 infected children had anti-HRVLA IgM in their acute sera before the appearance of anti-HRVLA IgG. ELISA is a useful tool in the evaluation of immunological response to HRVLA infection.

Antibody responses in patients with rubella infection determined by passive hemagglutination, hemagglutination inhibition, complement fixation, and solid-phase radioimmunoassay tests

Antibody responses in serial serum specimens collected from 31 patients with an acute rubella infection were determined by passive hemagglutination (PHA), hemagglutination inhibition (HI), complement fixation (CF), radioimmunoassay (RIA) immunoglobulin G (IgG), and RIA immunoglobulin M (IgM) tests to evaluate the effectiveness of these tests in diagnosing a recent infection. The HI, RIA IgG, and RIA IgM antibodies appeared almost simultaneously and reached the maximum level about 1 week after the onset of rash. Compared to these, the CF antibodies developed only slightly later, whereas the development of the PHA antibodies was much more delayed. The RIA IgM response was shown to be transient, lasting approximately 1.5 to 2.5 months postinfection. The results of this study indicate that demonstration of specific IgM antibodies is the best method for diagnosing a recent infection, one within 2 months after the onset of the illness. If an IgM test is not available, a combination of the HI and PHA tests is recommended.

Rubella serology by solid-phase radioimmunoassay: its potential for screening programmes

Sera from 269 adult females who had experienced naturally acquired or vaccine-induced infection by rubella virus, including immune persons challenged intranasally with rubella vaccine (RA27/3) as well as sera from 100 patients attending antenatal clinics, were tested for rubella antibodies by the conventional haemagglutination inhibition tests (HAI), as well as a newly developed solid-phase radioimmunoassay (RIA) for rubella immunoglobulin G (IgG) antibodies. Following both naturally acquired and vaccine-induced infection, titres by RIA were approximately ten-fold higher than by HAI. The RIA test was particularly useful in assessing the true immune status of those with apparently low levels of HAI antibody and has the added advantage that pre-treatment of sera to remove inhibitors of haemagglutination and red cell agglutinins is unnecessary. The RIA test has potential for the large-scale screening programmes which need to be carried out if the Department of Health and Social Security recommendation, that women attending antenatal and family planning clinics be screened for rubella antibodies, is to be effectively met.

Persistence of immunoglobulin G and immunoglobulin M antibodies after postnatal rubella infection determined by solid-phase radioimmunoassay

The appearance and persistence of immunoglobulin M (IgM) and IgG antibodies in postnatal rubella infections were studied by employing a solid-phase radioimmunoassay test. Altogether, 222 serial serum specimens from 51 patients with acute rubella infection were tested. Both IgG and IgM antibodies developed rapidly and appeared in all patients within 4 days after the onset of rash. In some patients, the IgM antibodies clearly preceded the IgG antibodies; however, the reverse situation was also noticed in a few cases. The IgG antibodies showed only minor changes after 8 to 10 days from the onset of rash. The IgM titers also reached a maximum level at approximately 8 to 10 days after the onset of rash, after which time a rapid decrease was normally seen. The mean half-life of IgM antibodies after 15 days from the onset of rash was 4.5 days, giving for IgM antibodies persistence times from 43 to approximately 80 days. Two patients with a prolonged IgM antibody response were detected. One of these patients had bilateral arthritis of the knee as a complication, whereas in the other patient no complication caused by rubella virus was detected. The IgM antibody response and its value in diagnosis are discussed.

HLA antigens and antibody responses to measles and rubella viruses in multiple sclerosis

Twenty-four HLA-antigens coded by loci A and B were determined serologically for 60 multiple sclerosis patients from Northern Finland. Forty-five of the patients were also typed by mixed leucocyte culture reactivity for HLA-Dw2. The only statistically significant difference in antigen frequencies in these patients compared with those in controls was the decrease of HLA-A2 among patients. Measles and rubella antibody titres in patients with and without HLA-Dw2 and HLA-B7 antigens were compared using a sensitive radioimmunoassay method. There was no difference between age- and sex-matched patient groups.

Solid-phase radioimmunoassay detection of rubella virus IgG antibody in serum and CSF of patients with multiple sclerosis

Low levels of rubella virus IgG antibody have been detected in cerebrospinal fluid (CSF) specimens of multiple sclerosis (MS) patients by a solid-phase radioimmunoassay (RIA) previously developed for testing of clinical serum samples. Paired serum and CSF specimens of 36 MS patients and 12 control patients were analyzed. Of those MS patients which had negative CSF titers in the rubella hemagglutination inhibition (HAI) test, 90% (11/12) were found to have rubella IgG antibody by the RIA method. In specimens found to contain rubella IgG antibodies by both methods, the RIA test was approximately 15 times more sensitive than the rubella HAI test. The results presented suggest that a considerable portion of MS patients have significantly reduced serum/CSF rubella IgG antibody ratios, indicating that there is a local production of rubella antibodies in the central nervous system of these patients.

Solid-phase radioimmunoassay of human immunoglobulin M and immunoglobulin G antibodies against herpes simplex virus type 1 capsid, envelope, and excreted antigens

A solid-phase radioimmunoassay developed in our laboratory for detection of human viral immunoglobulin M (IgM) and IgG antibodies was applied to demonstrate human class-specific antibody response against capsid, envelope, and excreted antigens of herpes simplex virus type 1. In primary infections, a clear IgM and IgG antibody response was found predominantly against the envelope components, whereas the IgM and IgG antibodies to the capsid antigen appeared more slowly. Increasing IgG antibody titers to the excreted antigen were also found in primary infections, though appearing more slowly than antibodies to the other subunit antigens. The antibody response against capsid and envelope antigens was not type specific, whereas in primary infections IgG class antibodies against the excreted antigen showed distinct type specificity. In recurrent infections, no significant level of IgM class antibodies was demonstrated, but in the patients with a severe secondary herpes simplex virus infection a definite IgM class antibody response was found against the envelope antigen. In addition, during severe secondary infections the antibody response against the excreted antigen was enhanced. The host IgG antibody response in recurrent infections was directed against the envelope and excreted antigens, whereas the level of the capsid antibodies was relatively stable.