Specific detection of IgM-antibodies by ELISA, applied in hepatitis-A

Survival of rotavirus antibody activity derived from bovine colostrum after passage through the human gastrointestinal tract

BACKGROUND

Rotavirus is a major cause of infectious diarrhea in infants and young children. Several studies have shown that hyperimmune bovine colostrum, derived from cows immunized with rotavirus, can prevent rotavirus diarrhea when given passively. The objective of this study was to determine whether colostral antibody activity survived transit through the gut by measuring the level of rotavirus antibody activity in the feces.

METHODS

Hyperimmune colostrum containing different levels of rotavirus antibody was administered to 105 children attending nine Adelaide childcare centres. Subjects were asked to drink 100 ml of whole milk supplemented with colostrum 3 times a day, for a period of 6 days. Stool samples were collected from the subjects before, during, and after consumption of the study product. Rotavirus activity was determined using a novel virus reduction enzyme-linked immunosorbent assay (ELISA) and a virus neutralization assay.

RESULTS

Rotavirus antibody activity was detected in 521 (86%) of 602 fecal specimens obtained during the study using the virus reduction ELISA. The antibody activity was detected as early as 8 hours after ingestion of hyperimmune colostrum and up to 72 hours after consumption had ceased. There was a strong relation (r = 0.81) between the titer of rotavirus antibody administered to subjects and the level of antibody activity detected in the feces.

CONCLUSIONS

The results show that antirotavirus activity survived passage through the gut. Therefore, passive immunotherapy may be used to prevent or treat infectious diseases that affect the entire length of the gastrointestinal tract.

New, ultrasensitive enzyme immunoassay for detecting vaccine- and disease-induced hepatitis A virus-specific immunoglobulin G in saliva

Although detection of disease-induced hepatitis A virus (HAV)-specific antibodies in saliva has been successfully utilized in a few epidemiological studies, available assays fail to detect lower salivary anti-HAV levels associated with vaccine-induced immunity. We present a new capture enzyme immunoassay which employs a three-layer antibody recognition system. Evaluation of paired saliva-serum specimens from 1,025 international travellers, 134 other volunteers, and 91 hepatitis A vaccine recipients demonstrated 99.6% (95% confidence interval, 98.4 to 99.9) specificity and 98.7% (95% confidence interval, 97.7 to 99.4) sensitivity of this salivary assay in differentiating between immune and susceptible individuals, compared with serum-based methods. We conclude that this assay is sufficiently sensitive for reliable detection of both vaccine- and infection-induced HAV-specific immunoglobulin G in saliva, even when corresponding anti-HAV levels in serum are very low (< 1 IU/ml).

Development and evaluation of capture enzyme-linked immunosorbent assays for detection of immunoglobulin G and M antibodies to group A streptococcal antigens

Capture enzyme-linked immunosorbent assays (ELISAs) were developed to detect immunoglobulin G and M antibodies to group A streptococcal (GAS) antigens, streptolysin O, streptokinase, and group A carbohydrate. The sensitivities and the specificities of the IgM capture ELISAs to each GAS antigen were high enough to distinguish the patients with GAS infections (diagnosed as GAS pharyngitis or scarlet fever) from the control groups (healthy people and patients with pharyngitis from whom GAS could not be isolated). On the other hand, the specificities of the IgG capture ELISAs were not very effective in diagnosis of GAS infections. When the capture ELISA and an indirect ELISA detecting IgM antibodies to group A carbohydrate were compared, false-positive reactions due to rheumatoid factor occurred in the indirect ELISA, but did not occur in the capture ELISA. These results indicate that the capture ELISA works better than the indirect ELISA in detecting the IgM antibody, and that the IgM capture ELISA to GAS antigen provides a rapid and highly reliable serodiagnosis for GAS infections employing only a single serum.

Capture ELISA for IgM antibodies against Plasmodium falciparum glutamate rich protein

This report describes a novel mu chain capture ELISA for the detection of IgM antibodies against a Plasmodium falciparum antigen. A fragment of the 220 kDa P. falciparum glutamate rich protein containing amino acid residues 489-1271 was expressed in E. coli as a recombinant chimeric beta-galactosidase fusion protein and used as antigen after purification and biotinylation. Specific IgM antibodies were found in 51% (39/77) of sera from adult Liberians immune to malaria. The binding of IgM antibodies was specific for the malaria portion of the fusion protein and no cross-reactivity was found in sera from patients with IgM antibodies due to other diseases. Inhibition studies with a fusion protein containing amino acid residues 816-1134 (GLURP816-1134) representing the carboxy-terminal repeat region suggested a different use of epitopes for IgM antibodies in different individuals.

Improved immunoglobulin M serodiagnosis in Lyme borreliosis by using a mu-capture enzyme-linked immunosorbent assay with biotinylated Borrelia burgdorferi flagella

A mu-capture enzyme-linked immunosorbent assay (ELISA) for detection of serum immunoglobulin M (IgM) antibodies to Borrelia burgdorferi by using biotinylated purified B. burgdorferi flagella was developed. The diagnostic performance of the mu-capture ELISA was compared with that of a conventional indirect ELISA. Sera from untreated patients with erythema migrans (n = 50), neuroborreliosis (n = 100), and acrodermatitis chronica atrophicans (ACA; n = 48) were investigated. The cutoff of the ELISAs was adjusted to a diagnostic specificity of 98% on the basis of examination of 200 serum specimens from healthy controls. The mu-capture ELISA increased the diagnostic sensitivity in patients with erythema migrans from 32 to 48% (P less than 0.01) and in patients with neuroborreliosis from 37 to 57% (P less than 0.001). Because of an increased signal/noise ratio, the mu-capture ELISA yielded a significantly better quantitative discrimination of individual positive measurements from the cutoff (P less than 0.001). The increased signal/noise ratio was most likely a consequence of the elimination of IgG competition for the test antigen. This may also explain why 12% of patients with ACA showed significantly increased specific IgM levels only by the mu-capture ELISA. Of patients with ACA, 27% had IgM rheumatoid factor. The mu-capture principle with a directly labeled antigen showed no interference with IgM rheumatoid factor, in contrast to the indirect ELISA. The high diagnostic performance and ease of this three-step mu-capture ELISA make it suitable for routine anti-B. burgdorferi IgM serodiagnosis.

Comparison of six commercial enzyme linked immunosorbent assays for detecting IgM antibodies against Toxoplasma gondii

To evaluate the usefulness of different commercial enzyme linked immunosorbent assays (ELISAs) for the detection of IgM antibodies against Toxoplasma gondii the results of six of these assays for a panel of 81 sera were compared. The following tests were selected: Toxoplasma gondii IgM ELISA (Clark Laboratories), Toxoplasma IgM EIA (Labsystems), Toxo-M EIA (Abbott), Toxonostika M (Organon), Toxo M Enzyme Immunoassay (Hybritech) and Platelia Toxo IgM (Diagnostics Pasteur). An antibody capture ELISA developed at our laboratory was used as the reference test. An IgM immunoblotting assay was also performed. Four (Toxoplasma IgM EIA, Tox-M EIA, Toxonostika M, and Platelia Toxo IgM) of the commercial IgM ELISAs gave a high sensitivity and a high specificity. Toxo-M EIA, Toxonostika M, Toxoplasma IgM EIA and the Toxo M Enzyme Immunoassay were too insensitive, and the Toxoplasma gondii IgM ELISA was both insensitive and unspecific. No remarkable differences were observed between the results of indirect or antibody capture ELISAs, and between the results of ELISAs performed with polyclonal or monoclonal antibodies.

Use of monoclonal antibodies in an ELISA to detect IgM class antibodies specific for Toxoplasma gondii

Two monoclonal antibodies CH6 and C1E3 were used in an antibody class capture assay for the detection of IgM antibodies specific for Toxoplasma gondii. CH6 was used on the solid phase to capture human IgM. After a Toxoplasma gondii antigen had been added, specifically bound material was detected using C1E3 coupled to horseradish peroxidase. The assay was compared with an established system using polyclonal antisera at both the capture and antigen detection stages. A good correlation was found, with 97.3% (125 of 128) of sera giving the same classification in both assays. Three sera were positive only in the polyclonal system. No false positive results were found when 118 negative sera were examined. The two monoclonal antibodies provide a viable alternative to the use of polyclonal sera at the capture and antigen detection stages in the antibody class capture assay for the measurement of specific IgM against T gondii.

An ELISA study on varicella-zoster virus infection in acute peripheral facial palsy

ELISA was applied to atraumatic acute peripheral facial palsy for the purpose of examining the usefulness of the method with respect to early diagnosis of varicella-zoster virus (VZV) infection. The material for this study consisted of 287 cases of Bell's palsy, 64 cases of Hunt's syndrome and 12 cases of zoster sine herpete diagnosed by the CF method, obtained from 16 institutions throughout Japan. In view of the results thus obtained, it was provided that cases of specific anti-VZV-IgG antibodies (anti-VZV-IgG) with a titre of 0.6 or more or specific anti-VZV-IgM antibodies (anti-VZV-IgM) with a titre of 0.2 or more were to be regarded as cases of VZV infection. By adopting ELISA, a diagnostic ratio of 94.3% in Hunt's syndrome was achieved. Moreover, possible cases of zoster sine herpete increased further by 28. Furthermore, most of the cases became diagnosable in the second week after onset of the facial palsy. It was therefore presumed that ELISA makes possible diagnosis in the comparatively early stages with only one testing, and that it is a more useful method than CF.

Epidemiological aspects of acute viral hepatitis in São Paulo, Brazil

As few reports on the prevalence of each type of viral hepatitis have been published in our country, we studied 154 patients with acute viral hepatitis consecutively seen at the Liver Unit from November 1980 to November 1984. The frequency of hepatitis A, B and non-A, non-B was 52.6%, 27.3% and 20.1% respectively. Greater frequency in young people, previous contact with infected patients and ingestion of suspected foods were the predominant epidemiological features in the hepatitis A group. Hepatitis B was characterized by the parenteral, non-transfusional exposure, previous contact and a high occurence in health-care workers. A history of blood transfusion was a significant finding in the hepatitis non-A, non-B group. Finally, the routes of transmission were unknown in 30-40% of the three groups of patients.

Rapid double-sandwich enzyme-linked immunosorbent assay for detection of human immunoglobulin M anti-Toxoplasma gondii antibodies

The double-sandwich enzyme-linked immunosorbent assay has been compared with the indirect fluorescence assay for the detection of immunoglobulin M antibodies against Toxoplasma gondii in humans. Incubation times have been shortened, permitting the test to be completed within 2 h. The double-sandwich enzyme-linked immunosorbent assay is confirmed to be more sensitive and more specific than the immunofluorescence assay.

Rapid separation of IgM from whole serum using spun column chromatography

Spun columns were used to separate IgM from serum samples by exploiting molecular weight and size difference between IgM and other serum antibodies. Miniature gel chromatography columns were prepared in 3 ml syringe barrels. A polyacrylamide liquid chromatography gel, Bio-Gel P-200, was chosen to exclude proteins with molecular weights greater than 200,000. IgM, 900,000 MW, was excluded while IgG, 150,000 MW, was retained in the gel column. Centrifugation of the serum-loaded columns in test tubes accomplished the separation in one step by eluting a void volume equal to the sample volume from each column into a holding tube. IgM recovery in the eluent exceeded 96% of the total serum IgM in the pre-column sample. No IgG was detected in the eluent. IgM separated from La Crosse encephalitis immune human serum retained immunological activity in a viral neutralization test. Spun column chromatography is eminently suitable for diagnostic laboratories as more than 100 sera may be fractionated in one day using inexpensive materials and a low-speed centrifuge equipped with a swinging-bucket rotor.

Use of a monoclonal antibody in a double-sandwich ELISA for detection of IgM antibodies to Toxoplasma gondii major surface protein (P30)

A double-sandwich ELISA, developed for detection of IgM antibodies to the major surface protein of Toxoplasma gondii (P30), is proposed for the diagnosis of acute acquired toxoplasmosis. The method is based on the capture of serum IgM antibodies, which are revealed indirectly by the sequential addition of a Toxoplasma extract and a beta-galactosidase-conjugated anti-P30 monoclonal antibody. All 57 patients tested with serological characteristics of recently acquired toxoplasmosis showed high levels of IgM anti-P30 antibodies. In addition, 5 out of the 24 patients with chronic toxoplasmosis and all 7 patients with a clinical acute infection in which the classical IgM serology was negative, also presented significant anti-P30 IgM antibodies. Patients with either rheumatoid factor or antinuclear antibodies were all negative. In view of its simplicity, specificity and sensitivity, this method is recommended for the current diagnosis of T. gondii infection.

Tick-borne encephalitis: a simple method for detection of antibody production in the brain

Antibodies found in c.s.f. of patients with TBE are usually produced in the CNS itself, although their presence might also be due to a leak in the blood brain barrier. In the case of local antibody production the ratio of the TBE specific IgM or IgG to the total immunoglobulin is relatively high in c.s.f., whereas in case of a leak this ratio is lower and corresponds to that of the serum. Local antibody production in the brain can therefore be assumed, if the ratio is higher in c.s.f. than in serum. It is possible to determine this ratio in an anti-mu or anti-gamma capturing antibody ELISA, provided that the concentration of capturing antibodies represents the limiting factor of the test system. Under these conditions the absorbance values obtained are a direct reflection of the TBE reactive to nonreactive antibody ratio, since they compet for the limited binding sites presented on the solid phase. Higher extinction values of c.s.f. compared to that of serum are therefore an indication for local antibody production in the brain. Using the method described, differences were found in the production of IgM and IgG antibodies against TBE in the CNS from patients with different clinical history.

Detection of hepatitis A virus and antibody by solid-phase radioimmunoassay and enzyme-linked immunosorbent assay with monoclonal antibodies

Monoclonal antibodies (K3-2F2 and K3-4C8) raised against hepatitis A virus were used to develop a solid-phase radioimmunoassay and enzyme-linked immunosorbent assay for the detection of hepatitis A virus and antibody. Assays with this pair of monoclonal antibodies were compared in parallel with similarly constructed solid-phase radioimmunoassays and enzyme-linked immunosorbent assays in which human polyclonal serum was used. The monoclonal antibody assay proved to be more sensitive for the detection of hepatitis A virus from fecal specimens as well as for anti-hepatitis A virus immunoglobulin G (IgG) and IgM in sera.

Evaluation of commercial methods of enzyme immunoassay (EIA) for the measurement of rubella-specific IgM

Four commercial EIA methods for measuring rubella-specific IgM (three indirect tests and one anti-mu capture test) were evaluated, using sucrose gradient centrifugation and hemagglutination inhibition as the reference method. Evaluation was conducted with the aid of four serum panels, including 53 primary rubella cases, 30 healthy pregnant women, 21 sera positive for rheumatoid factor(s) (RF) and 35 sera from 29 cases of heterophil-positive infectious mononucleosis with EBV-specific IgM detected by immunofluorescence. All EIA methods were more sensitive than the reference method when applied to very early samples (1-5 days post-exanthema) and no differences in sensitivity were found between them. On the other hand, we observed a significant incidence of false-positive results if an indirect EIA method is applied to RF-positive samples. False positivity is significantly reduced, but not totally eliminated, when samples are preabsorbed with anti-human IgG serum and, in all cases, the absorbance values obtained were low. In contrast, there were no false-positive results using an anti-mu capture method, even in sera from cases of infectious mononucleosis. The basis for choosing between an indirect method and an anti-mu capture method for the diagnosis of congenital and post-natal rubella virus infection is discussed.

ELISA: highlights of the present state of the art

ELISA is now very widely used. Many variations on the theme have been described. The search for further improvements is ongoing, mainly in the areas of sensitivity, specificity and practicability. Of course, the application of monoclonal antibodies is important in this respect. Next to that, further improvements in the detection of the enzyme label have come to the fore. Examples regarding the use of tetra-methylbenzidine as a peroxidase-substrate and details on its safety, a novel amplification method for detecting alkaline phosphatase and an enhanced luminescence method to detect peroxidase are given.

Rapid diagnosis of acute mumps infection by a direct immunoglobulin M antibody capture enzyme immunoassay with labeled antigen

A new immunoglobulin M (IgM) antibody capture enzyme immunoassay with peroxidase-labeled mumps antigen (dMACEIA) is described, and its suitability for practical diagnosis of acute mumps infection is evaluated. All 54 patients with proven mumps infection that were tested showed mumps-specific IgM antibodies. On the other hand, no specific IgM antibodies were present in 16 cases of suspected mumps that could not be confirmed by classical complement fixation serology, and IgM mumps virus antibodies could be detected neither in the sera of 100 healthy individuals nor in those of 16 patients positive for rheumatoid factor. In all, 22 children with acute respiratory illness caused by parainfluenza virus and 44 patients with infections due to other viruses showed no IgM response in mumps dMACEIA. The particular characteristic in which complement fixation antibodies against mumps nucleocapsids appear before and disappear earlier than antibodies to the enveloped mumps virus could not be demonstrated in the dMACEIA. In an extensive epidemic of mumps virus infection, the dMACEIA gave a clear diagnosis of mumps infection in 200 out of 371 suspected cases. By day 2 of the illness, 71% of the patients had detectable IgM, and by day 3, all of them had detectable IgM. In 99% of the cases, dMACEIA gave a positive result in the first available serum specimens, most of which were negative for complement fixation antibodies. A positive but only moderate correlation was thus observed between the two serological procedures. IgM antibodies persisted for at least 6 weeks. The dMACEIA, performed in 3 h, offers a reliable, simple, and rapid alternative to routine methods for detection of acute mumps infection.

An enzyme-linked immuno-filtration assay used to compare infant and maternal antibody profiles in toxoplasmosis

Enzyme-linked immuno-filtration assay is carried out on a micropore membrane. This doubly analytical technique permits simultaneous study of antibody specificity by immunoprecipitation and characterisation of antibody isotypes by immuno-filtration with enzyme-labelled antibodies. Recognition of the same T. gondii antigenic constituent by IgG, IgA, IgM or IgE antibodies produces couplets (IgG-IgM; IgG-IgA) or triplets (IgG-IgM-IgA; IgG-IgM-IgE) which identify the functional fractions of the toxoplasmosis antigen. In acquired toxoplasmosis, the persistence of IgM antibody long after infestation puts in question the implication of recent infestation normally linked to detection of this isotype. For sera of comparable titres, comparison of immunological profiles by the method described demonstrates disparities in the composition of the specific antibody content as expressed in international units. Use of the same method to detect IgM antibodies or distinguish between transmitted maternal IgG and IgG antibodies synthesised by the foetus or neonate makes a diagnosis of congenital toxoplasmosis possible in 85% of cases during the first few days of life. With the method described the diagnosis may be made on average 5 months earlier than with classical techniques. In the course of surveillance for latent congenital toxoplasmosis, the appearance of IgM or IgE antibodies raises the possibility of complications (hydrocephalus, chorioretinitis). After cessation of treatment, a rise in IgG antibodies indicating persistence of infection is detected earlier by the present than by classical methods.

An anti-human mu chain monoclonal antibody: use for detection of IgM antibodies to Toxoplasma gondii by reverse immunosorbent assay

A precipitating anti-human mu chain monoclonal antibody (designated Tibi 82 McAb) was produced by the cell fusion technique. This McAb (isotype: IgG1 kappa) reacted by radioimmunoassay with all 10 human IgM proteins tested. In contrast, no reactivity was observed with IgG, IgA, IgE, lambda and kappa chains. 19 S IgM proteins were precipitated by Tibi 82 McAb using the Ouchterlony method under standard conditions. Hence specificity of this McAb for the C mu 2 domain was characterized by inhibition of precipitin reactions using human IgM fragments. Despite its narrow specificity for the C mu 2 domain, such a McAb could be used for IgM capture in the detection of specific IgM to Toxoplasma gondii employing the IgM immunosorbent agglutination assay (IgM-ISAGA). Tibi 82 McAb was compared with 3 anti-human IgM polyclonal reagents in the routine analysis of 117 sera. With 2 of them, a correlation coefficient of 0.976 was obtained and Tibi 82 McAb was more sensitive than the third polyclonal reagent tested. The IgM-ISAGA technique was shown to be reproducible using Tibi 82 McAb and similar anti-human mu chain McAbs could permit the wider development of reverse immunosorbent methods for the detection of specific IgM in various infectious diseases.

An anti-human immunoglobulin M monoclonal antibody for detection of antibodies to Toxoplasma gondii

An anti-human mu-chain monoclonal antibody, Tibi 82, was produced and tested for specificity by radioimmunoassay. Its reliability in detecting IgM antibodies to Toxoplasma gondii was tested by two reverse immunosorbent methods (IgM-ISAGA and IgM-SPIHA) and the IgM fluorescent antibody test (IgM-IFA) on 400 sera. Whereas the results obtained with Tibi 82 and with two polyclonal reagents were highly correlated, the third commercial polyclonal reagent provided many false negative results. By standardizing IgM binding, Tibi 82 allowed the comparison of IgM-ISAGA with IgM-SPIHA on 100 sera: 17% of the sera tested showed discrepancies due to the different toxoplasma antigens used. Although Tibi 82 facilitated the reading of results and enhanced sensitivity and specificity of the double-sandwich IgM-IFA method, the latter was still less sensitive than IgM-ISAGA with Tibi 82. Tests with the monoclonal antibody were consistently superior to tests with polyclonal antibodies.

Evaluation of an enzyme immunoassay for IgM antibodies to Treponema pallidum in syphilis in man

An enzyme immunoassay (EIA) for the detection of immunoglobulin M (IgM) antibodies to Treponema pallidum was investigated for specificity and sensitivity. Using the results in serum from 1192 patients with successfully treated syphilis, the assay was calculated to be about 97% specific. As in any other IgM enzyme linked immunosorbent assay (ELISA), rheumatoid factor played an important part in causing false positive results. Pre-absorption of serum with aggregated IgG was therefore necessary to perform the test. Evaluation of the results in serum from 385 patients with untreated primary, secondary, and latent syphilis as well as patients with untreated reinfections showed that the sensitivity of the assay depended on the stage of infection and varied between 98% and 93%. IgM antibody titres were about ten times higher in the EIA than in the indirect immunofluorescence assay using the IgM fractions of serum. From the results it may be concluded that the EIA is an appropriate technique not only for rapid and sensitive measurement of IgM antibodies in most patients with untreated syphilis but also for selecting treponemal IgM non-reactive patients.

Specificity and sensitivity of the IgM capture immunoassay: studies of possible factors inducing false positive or false negative results

The specificity and sensitivity of the IgM-capture immunoassay (IgM-CI) were evaluated for detection of rubella specific IgM and hepatitis B core (HBc) specific IgM. For rubella specific IgM, antibodies bound to the solid phase were detected by haemadsorption and for HBc specific IgM, by using HBc antigen (HBcAg) and radiolabelled IgG anti-HBc. Rheumatoid factor (RF) was found to interfere in the test for HBc specific IgM because IgM-RF bound to the solid phase reacted with aggregated radiolabelled HBc specific IgG. This false positive reaction did not occur when radiolabelled F(ab')2 was used instead of the whole IgG molecule. HBcAg purified from biological fluids might be coated with host IgG and under these conditions, HBcAg could react with RF. It was also demonstrated that high levels of IgG antibodies could interfere with IgG anti-mu coated-surface by means of non-immunological protein-protein interactions. In fact, IgG did not interfere in the rubella assay, whereas it did in the very sensitive anti-HBc test. To prevent this false-positive reaction, different dilution media were tested. Only the addition of non-specific IgG and fetal calf serum (FCS), to the dilution medium, seems to improve the specificity of the test. Furthermore, in order to decrease this non-specific IgG-IgG interaction and an occasional prozoning phenomenon, the dilution of serum to be tested was taken into account. Parameters considered to decrease sensitivity were also studied. RF, anti-F(ab')2 antibodies and non-specific IgM did not decrease significantly the sensitivity of the assay.

Detection of specific immunoglobulin M antibody to different flaviviruses by use of enzyme-labeled antigens

An enzyme immunoassay was developed for the detection of human immunoglobulin M (IgM) antibody to different flavivirus antigens. The IgM antibody of human sera was selectively bound to anti-IgM antibody-coated solid-phase plates. Flavivirus IgM antibodies were then detected by use of various enzyme-labeled antigens. The flavivirus antigens (dengue type 2 virus, West Nile virus, and tick-borne encephalitis virus) were produced in suckling mice. The antigens were labeled with horseradish peroxidase by adding the activated enzyme at alkaline pH to sucrose-acetone-treated antigens. Addition of unlabeled mouse brain suspension of uninfected animals to the diluted enzyme-labeled antigens effectively reduced nonspecific binding to the solid phase. In patients with acute flavivirus infections, viral IgM antibody could be demonstrated with high sensitivity. Furthermore, the enzyme-labeled antigen-IgM test showed greater specificity than the hemagglutination inhibition test.

Teste reverso para anticorpos igm na toxoplasmose, com hemácias sensibilizadas por antígenos de Toxoplasma gondii

Descreve-se um teste para anticorpos IgM-antitoxoplasma baseado na técnica de captura de IgM do soro por anticorpos anti-IgM adsorvidos a placas plásticas. Para evidenciação dos anticorpos antitoxoplasma nessa fração, utiliza-se uma suspensão de hemácias humanas, formolizadas e sensibilizadas por antígenos de Toxoplasma gondii. Nos testes positivos estas aparecem como uma camada contínua, enquanto que nos testes negativos depositam-se ao fundo das cavidades das placas. A leitura dos testes é muito mais evidente do que na técnica anteriormente proposta por Desmonts e cols, 1981, que utiliza suspensões de toxoplasmas. A suspensão de hemácias sensibilizadas pode ser preparada por simples diluição do reagente para o teste de hemaglutinação para a toxoplasmose.

Use of hepatitis B core antigen produced in Escherichia coli to detect immunoglobulin M specific antibodies in an enzyme-linked immunosorbent assay

The antigenic activity of HBcAg produced in Escherichia coli and HBcAg from human liver was compared in a mu-specific solid-phase antibody-capture assay for detection of anti-HBc-IgM. HBcAg from liver could be detected in dilutions up to 1:3, HBcAg from Escherichia coli in dilutions up to 1:10,000. Using HBcAg from Escherichia coli, sera from five patients with acute resolving hepatitis B and sera from four patients with acute hepatitis B who had developed chronic liver disease were tested for anti-HBc-IgM in ELISA. IgM fractions separated out of the same sera by immunoaffinity chromatography were tested for anti-HBc-IgM using a commercially available test. The results were in good agreement with those obtained by ELISA. Anti-HBc-IgM could be detected up to 900 days after onset of disease. Different groups of patients were tested for presence of anti-HBc-IgM in ELISA. Fifty-nine of 60 patients with acute hepatitis B were positive for anti-HBc-IgM at onset of illness. Ten of 16 patients with chronic aggressive hepatitis and seven of 23 HBsAg positive dialysis patients were also positive for anti-HBc-IgM, whereas only two of 12 patients with chronic persistent hepatitis and one of 15 HBsAg positive blood donors ("healthy" carriers of HBsAg) had detectable anti-HBc-IgM.

False positive results occurring in a radioimmunoassay for hepatitis A IgM antibody of the IgM class

The diagnosis of hepatitis A infection is usually based on the presence of hepatitis A specific IgM in a single serum sample. The fortuitous observation in one patient that this reactivity was apparently still present 19 mth after her original illness led to the discovery that the ABBOTT HAVAB-M kit method may produce false positive results. A series of patients who had previously had hepatitis A was retested and false positive results were found in 6% of this group. Control groups consisted of patients with other acute and chronic liver disorders and other acute viral diseases. No reactivity was detected in the control sera. Sucrose gradient fractionation revealed that the factor responsible for the false positive results was associated only with serum fractions containing IgA and IgG and that it could be removed by absorption of sera with staphylococcal protein A but not by absorption with streptococcus AR1 or by 2-mercaptoethanol treatment. It was concluded that following hepatitis A infection some patients produce a rheumatoid factor-like substance (not of IgM class) which is cleared from the serum in 2-3 yr. The presence of this factor may lead to a misdiagnosis in patients presenting with jaundice.

Report of a joint DMRQC/Organon field trial to detect hepatitis A IgM by ELISA

The results of a field trial of a joint DMRQC/Organon ELISA kit for the detection of hepatitis A IgM antibody are reported. The participating laboratories were asked to use the kit to test a panel of 360 specimens consisting of duplicate coded samples of 180 sera. The panel was also tested by MACRIA in the Virus Reference Laboratory, Colindale. The ELISA was shown to be specific and sensitive giving good discrimination between acute and late convalescent hepatitis A sera. It was proposed that the same cut-off control as is used in the RIA (equivalent to 10 RIA units) should be adopted for the ELISA also.

Determination of IgG, IgM and IgA antibody responses in human toxoplasmosis by enzyme-linked immunosorbent assay (ELISA)

A 4-layer modification of ELISA for the determination of toxoplasma antibodies is described. In 103 Finnish blood donors 27 had antibodies against Toxoplasma gondii. One donor had IgM antibodies and IgA antibodies were found in 9. In patients with acute toxoplasmosis a vigorous IgG antibody response resulted in high antibody levels soon after infection, declining gradually to mean adult levels in approximately 2 yr. IgM antibodies appeared during the earliest phases of infection and disappeared as early as in 1 or 2 months in some cases and in most cases by the 6th month after infection. An IgA antibody response was also always seen. It was slower than the IgM response and could therefore be used to improve the laboratory diagnosis especially in cases where IgM antibodies had already disappeared and no further increase in IgG antibodies could be detected.

Serodiagnosis of viral hepatitis A: rise in antibody titre and evaluation of three methods for detecting early and late antibodies

A serological investigation was made on patients with viral hepatitis A and individuals with a past history of this disease. Titration of antibody in sequential samples was found to be of no help in diagnosis. Separation of early (IgM) from late (IgG) antibodies by protein A or by 2-mercaptoethanol did not prove to be convenient for the serodiagnosis. A chromatographic separation of late and early antibody was found to be satisfactory, and equivalent to a radioimmunoassay for IgM-antibodies.

Comparison of methods for quantitating antigen-specific immunoglobulin M antibody with a reverse enzyme-linked immunosorbent assay

We compared two methods for quantitating antigen-specific antibody by a reverse enzyme-linked immunosorbent assay. In the serial-dilution method, the result was determined to be the highest dilution of a serum yielding an absorbance above an established threshold. In the single-dilution method, the result was determined by comparing the absorbance yielded by the test serum at a standard dilution to that yielded by positive and negative reference sera at the same dilution. The results in the single-dilution method reflected the antigen-specific immunoglobulin M antibody activity as a proportion of total immunoglobulin M antibody in a serum, i.e., the immune load, whereas the results in the serial-dilution method reflected the absolute concentration of antigen-specific immunoglobulin M antibody activity. Compared with results in the serial-dilution method, results in the single-dilution method had considerably greater reproducibility on a day-to-day basis and under various test conditions. The single-dilution method was more useful in discriminating between sera from patients in an early stage of clinical infection due to Toxoplasma gondii and sera from patients in a later stage of infection.

Enzyme-linked immunosorbent assay that uses labeled antigen for detection of immunoglobulin M and A antibodies in toxoplasmosis: comparison with indirect immunofluorescence and double-sandwich enzyme-linked immunosorbent assay

A direct enzyme-linked immunosorbent assay (ELISA) is described that uses horseradish peroxidase-labeled antigen for detection of immunoglobulin M (IgM) and IgA antibodies to toxoplasma. In this assay, polystyrene microtiter plates were sensitized with anti-human IgM or IgA antibody to separate IgM or IgA from other classes of antibody. The presence of IgM or IgA antibodies to toxoplasma (Tox-IgM, Tox-IgA) was then detected by sequential addition of soluble horseradish peroxidase-labeled toxoplasma antigen and substrate. As judged by examining sucrose gradient-fractionated sera, the assay was specific for IgM or IgA classes of antibody. In contrast to the indirect immunofluorescence for IgM antibodies to toxoplasma, no inhibition of IgM reactivity by specific IgG antibodies could be detected. Furthermore, rheumatoid factor did not cause false-positive results. Of 80 single sera with high antibody titer to toxoplasma in indirect immunofluorescence and complement fixation, 40 were positive in the direct ELISA for Tox-IgM, 36 were positive in the double-sandwich ELISA, and only 21 were positive in the indirect immunofluorescence for Tox-IgM when whole serum was used. In the indirect immunofluorescence, another 13 sera became positive after sucrose gradient fractionation. The direct ELISA for IgA antibodies to toxoplasma was positive in 43 sera, of which 39 were positive in the direct ELISA for Tox-IgM. High levels of IgM antibodies were found within 3 months after the onset of symptoms, slowly decreasing thereafter. Tox-IgM may persist for more than 1 year after infection.

Enzyme-linked immunosorbent assay for immunoglobulin G and M antibodies to Chlamydia trachomatis in human sera

Microimmunofluorescence methods used for detection of immunoglobulin G and M antibodies to Chlamydia trachomatis are not available to many clinical laboratories. We evaluated a simple enzyme-linked immunosorbent assay in which serotype L2 elementary bodies are used as antigen. The enzyme-linked immunosorbent assay proved satisfactory for the detection of serum IgG. A total of 160 human sera were tested, and the results correlated well with those obtained by microimmunofluorescence. Results for IgM antibody detection were not as successful, and correlation with current methods was poor.

Prevalence and significance of anti-HBc IgM (radioimmunoassay) in acute and chronic hepatitis B and in blood donors

Anti-HBc IgM was determined by a modified radioimmunoassay (RIA) in 35 patients with acute hepatitis B, 35 patients with chronic hepatitis B (7 with chronic persistent, and 28 with chronic active hepatitis), 157 HBsAg positive blood donors, and in 143 HBsAg negative but anti-HBc positive donors. The results of the RIA test were compared with those obtained by an ELISA technique. In chronic hepatitis, anti-HBc IgM was correlated with the occurrence of HBeAg, anti-HBe, Dane particles in the serum, HBsAg, and HBcAg in liver tissue and with biochemical and histological degrees of hepatic inflammatory activity. In acute self-limited hepatitis B, anti-HBc IgM (RIA and ELISA) was initially positive in all 35 patients. Twelve months after the acute illness, 94% of the patients were negative for anti-HBc IgM in the RIA test with only one patient showing a persistence of up to 18 months, whereas in the ELISA test anti-HBc IgM persisted in 17% of the patients over 2 years. In chronic hepatitis, the occurrence of anti-HBc IgM (RIA) showed a strong relation with the inflammatory activity, the anti-HBc IgM positive patients revealing a significantly more severe liver disease than did anti-HBc IgM negative patients. Anti-HBc IgM (RIA), however, did not correlate with the occurrence of HBeAg and Dane particles in the serum and HBcAg in liver tissue of patients with chronic hepatitis. Of the 157 HBsAg positive blood donors, anti-HBc IgM (RIA) could be demonstrated in 10 (6%), but in none of the 143 HBsAg negative, but anti-HBc positive donors, as compared to 43 (27%) and 9 (6%), respectively, in the ELISA test. Comparing the two test methods, the RIA exhibits higher specificity than did the ELISA due to a better blocking of nonspecific reactions, but possibly somewhat lower sensitivity. In this form, however, the RIA test is a more useful tool in the diagnosis of the different forms of hepatitis B virus infection and in determining the severity of chronic hepatitis B.

Microenzyme-linked immunosorbent assay for detection of immunoglobulin G and immunoglobulin M antibodies to Legionella pneumophila

The microenzyme-linked immunosorbent assay (ELISA) for the detection of immunoglobulin M and G (IgM, IgG) antibodies to Legionella pneumophila serogroup 1 antigens was evaluated. IgM antibodies were measured by both double-sandwich and single-sandwich techniques. These assays were compared with the previously standardized indirect immunofluorescence test in four groups of subjects: (i) pneumonia patients with culture-proven Legionnaires disease with serogroup 1 isolates, (ii) pneumonia patients with serogroup 1 organisms detected by direct immunofluorescence testing of respiratory secretions but without culture confirmation, (iii) pneumonia patients with negative culture and direct immunofluorescence tests, and (iv) healthy hospital employees. In addition, the sensitivity and specificity of the IgG ELISA were evaluated with larger groups of controls and Legionnaires disease patients. The ELISA was more sensitive than the indirect immunofluorescence test. However, it detected antibody rises in pneumonia patients without culture or direct immunofluorescence evidence of L. pneumophila serogroup 1 infection, thereby suggesting that the specificity of the ELISA was slightly lower than that of the indirect immunofluorescence test. The double-sandwich ELISA was a sensitive method for detecting IgM antibodies and, as previously reported, appeared to be free from interference by rheumatoid factor. IgM anti-Legionella antibodies detected by the ELISA appeared earlier and were less persistent than IgG antibodies. In addition, the IgM ELISA was useful in detecting antibodies in necropsy serum samples obtained from patients dying acutely of Legionnaires disease. The data presented show that the ELISA is a reliable method for the detection of specific anti-Legionella antibodies.

Enzyme-linked immunosorbent assay for detection of immunoglobulin M antibody against the Reiter treponeme flagellum in syphilis

An enzyme-linked immunosorbent assay (ELISA) for detection of immunoglobulin M (IgM) antibodies against the periplasmatic flagellum of the Reiter treponeme is described. IgM in the test samples was bound to anti-IgM-coated microtest plates, and flagellum-specific IgM antibody was subsequently detected by incubation with a purified flagellum preparation and monospecific anti-flagellum conjugate. Rheumatoid factor, antinuclear antibodies, or flagellum-specific IgG did not interfere. The specificity of the ELISA for IgM antibodies was 99.5% for sera from 200 blood donors and 98.6% for 147 patient sera that gave false-positive reactions in other syphilis serological tests. The sensitivity was 88.5% for sera from 87 patients with first-time primary syphilis, 93.5% for sera from 62 patients with first-time secondary syphilis, 21.4% for sera from 42 patients who were reinfected, and 0% for sera from 13 patients with late syphilis. Of the sera from 153 patients with treated syphilis, 7.2% had IgM antibodies, and sera from patients with primary or secondary syphilis generally had no IgM antibodies 6 months after treatment. The finding of IgM antibodies indicates that patients should receive antisyphilis treatment if they have not been treated recently, but a negative result does not exclude the possibility of active syphilis. The method may prove useful for the diagnosis of congenital syphilis in newborns.

Enzyme-linked immunosorbent assay (ELISA) using antibody class capture for the detection of antitoxoplasma IgM

Sera from 180 patients with suspected toxoplasmic lymphadenopathy were examined for antitoxoplasma IgM by an enzyme-linked immunosorbent assay (ELISA), using antibody class capture (ACCA). Of 82 positive ACCA results, 78 were confirmed by testing the IgM fractions of the sera, obtained by sucrose density gradient centrifugation (SDGC). The four positive results which could not be confirmed were all from patients with at least a year's history of lymphadenopathy. Sera from 10 patients with low Sabin Feldman dye test (DT) titers gave positive ACCA results and subsequent specimens from them showed a rise in antibody concentration, confirming the diagnosis of acute toxoplasmosis. The antitoxoplasma IgM immunofluorescent antibody test (IgM-IFA) on whole serum was relatively insensitive and gave false-positive results with sera containing rheumatoid factor (RF) and antinuclear factor (ANF). There were no false-positive ACCA results with such sera, probably because the conjugates were prepared from F(ab')2 fragments of antitoxoplasma serum. The ACCA proved to be sensitive, specific and easily automated enabling examination of large numbers of specimens.

IgM antibody to the hepatitis B core antigen in acute hepatitis determined by SPRIA--diagnostic value

A solid phase radio-immunoassay (SPRIA) was developed for the detection of anti-HBc IgM. The assay proved sensitive and easy to perform and rheumatoid factor did not affect the test results. Anti-HBc IgM titres were followed in consecutive samples from 15 patients after uncomplicated acute hepatitis B. In the acute phase anti-HBc IgM titres ranged from 10(-5) to 10(-7) (mean 10(-6.4)). One year after onset of disease ten of the 15 had titres below 10(-4) and between two and three years after onset most patients had titres 10(-3). Anti-HBc IgM titres were determined in six episodes of acute hepatitis B, all HBsAg negative but anti-HBc positive in the first samples obtained (within 8 days) and developing anti-HBs during convalescence. Acute phase anti-HBc IgM titres in these patients ranged between 10(-5.5) and 10(-7) (mean 10(-6.5)) and were thus identical with HBsAg positive cases. When acute phase sera from 168 episodes of acute hepatitis primarily classified as non-A, non-B, were tested for anti-HBc IgM titres above 10(-5), sera from 13 episodes were positive and in seven of these hepatitis B diagnosis could be confirmed by rising anti-HBs titres in convalescence. Sera from four of the 13 patients contained HBeAg, which was thus demonstrated in the absence of HBsAg. The results show that testing for anti-HBc IgM is important for a true non-A, non-B diagnosis.

Antibody class capture assay (ACCA) for rubella-specific IgM antibody

Enzyme-linked immunosorbent assays for IgM antirubella were carried out on 1,546 sera, using an IgM capture method with a F (ab')2 conjugate (ACCA). Under the conditions described, sera containing IgM antirubella bound up to 15 times as much enzyme activity as negative specimens. Paired serum specimens from 27 patients, serial serum specimens from 6 patients, and single serum specimens from 15 patients who had had recent rubella were examined by the haemagglutination inhibition test (HAI) in the presence and absence of 2-mercaptoethanol following sucrose density gradient centrifugation (SDGC). ACCA confirmed all the results found with HAI following SDGC. Specimens were examined from ten patients with congenital rubella; ACCA confirmed the results found with both immunofluorescence following SDGC and radioimmunoassay. Pre- and post-vaccination specimens from 123 patients who had been vaccinated against rubella were examined. An IgM response could only be demonstrated in the 57 cases when IgG was absent in the first specimen. The specificity of the assay was confirmed by testing 31 serum specimens from rubella immune patients that also contained rheumatoid factor, 163 serum specimens from patients with acute infections other than rubella, and 12 serum specimens from infants with miscellaneous neonatal abnormalities other than congenital rubella. The ACCA proved a simple, sensitive, and specific test for IgM antirubella and the results compared favourably with those obtained by the SDGC technique.

Determination of immunoglobulin M antibodies against hepatitis B core antigen and hepatitis A virus by reorienting sucrose gradient high-speed centrifugation for diagnosis of acute viral-hepatitis

Immunoglobulin M (IgM) antibodies against hepatitis B core antigen (anti-HBc) and hepatitis A virus (anti-HAV) were determined in 41 cases of acute viral hepatitis. In sera positive for anti-HBc or anti-HAV, IgM was separated from IgG by reorienting sucrose gradient high-speed centrifugation, and the IgG- and IgM-containing serum fractions were tested for the presence of specific antibody by radioimmunoassay. At the onset of illness, 4 of the 41 cases were classified as hepatitis A, 31 were hepatitis B, and 6 were non-A, non-B hepatitis, based on the results of these tests and of assays for hepatitis B surface antigen and antibody and hepatitis B e antigen and antibody. Fourteen of these 41 patients (34%) required IgM anti-HBc or IgM anti-HAV testing or both for appropriate classification. IgM anti-HBc persisted for at least 7 weeks after onset but no longer than 17 weeks in all patients tested with transient hepatitis B surface antigen-positive acute hepatitis. IgM anti-HAV persisted up to but not longer than 62 days in the patients with hepatitis A. Therefore, IgM anti-HBc and IgM anti-HAV determinants are valuable tools for the differential diagnosis of acute A, B, and non-A, non-B hepatitis.

Enzyme immunoassays for measurement of cytomegalovirus immunoglobulin M antibody

The diagnosis of congenital cytomegalovirus (CMV) infection is often accomplished by the detection of circulating antibody directed against CMV. We devised a method for measuring CMV-specific immunoglobulin M (IgM) based on the isolation of IgM antibody by reaction with a solid phase coated with antihuman IgM. The determination of IgM antibody specific for CMV was accomplished by the subsequent addition of CMV or control antigen and enzyme-labeled CMV antibody (solid phase-IgM method). We compared the sensitivity and specificity of this method with those of a conventional form of solid-phase enzyme immunoassay in which CMV antigen is bound to the solid phase (solid phase-antigen method). Both assay systems were capable of detecting CMV-specific IgM antibody in the sera of 10 babies with documented CMV infection and in those of the mothers of 4 of these babies. The solid phase-IgM method yielded negative results in all 66 sera available from babies who did not have congenital CMV infection. On the other hand, the solid phase-antigen system yielded false-positive results in 12 (18%) of these sera. In addition, the solid phase-antigen system yielded false-positive results in 8 of 12 sera obtained from patients with demonstrable rheumatoid factor. However, the solid phase-IgM system yielded negative results for the rheumatoid sera, provided that appropriate control reactions were performed. The solid phase-IgM system is thus a specific and sensitive method for the determination of CMV IgM antibody.