Detection of antibodies specific for herpes simplex virus in human sera by the enzyme-linked immunosorbent assay

Rotavirusnachweis in Faezes: Erfahrungen mit dem Enzyme Linked Immunosorbent Assay (ELISA)

Zusammenfassung

313 Kälber‐, 47 Ferkel‐ und 100 menschliche Faezesproben von an Durchfall erkrankten neugeborenen Patienten wurden mit Hilfe einer modifizierten Immunelektronenmikroskopie‐Technik (IEM) und im Enzyme‐linked immunosorbent assay (ELISA) vergleichend untersucht. In 112 Kälber‐ (36%), 2 Ferkel‐ (4 %) und 21 (21 %) menschlichen Faezesproben konnte Rotavirus oder ‐antigen nachgewiesen werden.

Die Sicherheit der Methodik wurde zusätzlich anhand der Virusausscheidung von drei experimentell infizierten, kolostrumfrei aufgezogenen Kälbern überprüft.

Der ELISA, bei dem Meerrettichperoxidase als Enzym verwendet wurde, war spezifisch und erwies sich im Vergleich zur IEM als empfindlicher.

Bei 18 von insgesamt 136 positiven Proben gelang der Virusnachweis nur mit der IEM, diese Proben waren negativ im ELISA. In diesen Proben werden Virus‐Antikörperkomplexe vermutet.

Weitere Untersuchungen sind notwendig, bevor der ELISA zum Rotavirusnachweis in der Routinediagnostik empfohlen werden kann.

Summary

Demonstration of Rotavirus in Faeces: Experiences with the Enzyme linked immunosorbent assay (ELISA)

313 calf, 47 piglet and 100 human faecal samples from newborn patients with diarrhea were investigated comparing a modified immune electron microscopy method and the enzyme linked immunosorbent assay (ELISA). In 112 (36 %) calf, 2 (4 %) piglet and 21 (21 %) human samples rotavirus or its antigen could be demonstrated.

The suitability of the method was also tested by studying virus shedding of three experimentally infected, colostrum‐deprived calves.

The ELISA, using horse‐radish peroxidase as enzyme and 5 amino‐salicylic acid as indicator, was very specific and showed a higher sensitivity compared to IEM.

In 18 out of the 136 positive samples rotavirus could only be demonstrated by IEM; these samples were negative in the ELISA. It is assumed that these samples contain virus‐antibody complexes.

Further investigations are necessary before the ELISA can be recommended as a routine diagnostic test.

Résumé

Mise en évidence de Rotavirus dans des matières fécales: Expériences avec ELISA (Enzyme Linked Immunosorbent Assay)

313 maitères fécales de veaux, 47 de porcelets et 100 échantillons humains de patients nouveaux‐nés atteints de diarrhée ont été examinés en comparaison avec une technique immunologique modifiée en microscopie électronique (IEM) et avec ELISA. Rotavirus ou l'antigène ont pu être mis en évidence chez 113 veaux (36%), 2 porcelets (4%) et 21 enfants

La fiabilité de la méthode a été en plus testée sur la base de l'excrétion du virus chez trois veaux infectés expérimentalement et privés de colostrum. (21 %).

Le test ELISA, l'enzyme utilisée étant la peroxydase de Meerrettich, fut spécifique et s'est révélé plus sensible que IEM.

La mise en évidence du virus a été possible dans 18 cas sur 136 positifs avec la méthode IEM, ces échantillons s'étant révélés négatifs avec ELISA. On a supposé l'existence de complexes virus‐anticorps dans ces échantillons. D'autres recherches sont nécessaires avant de pouvoir recommander le test ELISA pour la mise en évidence de Rotavirus dans le diagnostic de routine.

Resumen

Identificación de virus Rota en heces: Experiencia con el Enzyme Linked Immunosorbent Assay (ELISA)

Se examinaron comparativamente 313 muestras de heces de terneros, 47 de lechones y 100 de niños, pacientes recién enfermos de diarrea, con ayuda de una técnica modificada de inmunomicroscopía de electrones (IEM) y en el Enzyme Linked Immunosorbent Assay (ELISA). En 113 muestras de heces de terneros (36 %), 2 de lechones (4 %) y 21 de niños (21 %) se pudo identificar virus o antígeno Rota.

La seguridad de la metodología se controló además con ayuda de la eliminación de virus por tres terneros infectados experimentalmente, criados sin calostro.

El ELISA, en el que se utilizó peroxidasa de rábano rusticano como enzima, era específico, resultando ser más sensible en comparación con la IEM.

Solo en 18 de un total de 136 muestras positivas se logró la identificación de virus con la IEM, siendo estas pruebas negativas en el ELISA. Se sospecha que en estas muestras había complejos de anticuerpos de virus.

Se precisa proseguir con las experiencias antes de poder recomendar el ELISA para la identificación de virus Rota en el diagnóstico de rutina.

An dieser Stelle möchte ich Dr. D. Ellens und Dr. P. de Leeuw, Central Diergeneeskundig Instituut, Leystad, Holland, sehr herzlich für die Überlassung von Referenzmaterial und die Hilfe bei der Entwicklung des ELISA in unserem Labor danken.

Whole cell lysate enzyme immunoassays vs. recombinant glycoprotein G2-based immunoassays for HSV-2 seroprevalence studies

Seroepidemiology studies of herpes simplex virus type 2 (HSV-2) infections have been difficult to carry out because antibodies to HSV type 1 (HSV-1) show an extensive cross-reactivity with HSV-2 antigens. Many kits available currently are not entirely type specific for serodiagnosis of HSV-2 infections and therefore do not allow reliable discrimination of past exposure to these closely related alphaherpes viruses. Attempts to develop type-specific antigens have focused on the envelope glycoproteins, particularly glycoprotein G (gG). A cross-sectional study was carried out to examine the seroprevalence of antibodies to HSV-2 among healthy university students, using different methods: a whole cell lysate enzyme-linked immunosorbent assay (ELISA), two different ELISAs, and a newly developed immunoblot assay, the last three based on recombinant gG2. HSV-2 prevalence was 24 times higher with the whole cell lysate ELISA (31%; 95% confidence interval [CI]: 27-35%) than the ELISAs and the immunoblot assay based on recombinant gG2 (1.3%; 95% CI: 0.1-2.5%), thus showing the inaccuracy of commercial tests based on whole-antigen preparations for epidemiological studies. Laboratories should be cautious and ensure that commercial tests for HSV typing are based on type-specific glycoproteins.

Detection of antibodies to Sendai virus in mouse sera by enzyme-linked immunosorbent assay (ELISA)

Enzyme-linked immunosorbent assay (ELISA) for diagnosis of Sendai virus infection in mice was evaluated. A large-scale survey of infected mice showed that ELISA is approximately 100 times more sensitive than the hemagglutination-inhibition or complement-fixation test. Although a few SPF mice showed false-positive reactions at a serum dilution of 1:40, further dilution to 1:80 eliminated the non-specific reaction. It was shown that ELISA is a highly satisfactory method for examination of Sendai virus infection in mice.

Detection of influenza viruses through selective adsorption and detection of the M-protein antigen

A model system has been developed which permits rapid detection of influenza viruses through targeting of the M (membrane or matrix)-protein; a type-specific antigen, in an enzyme-linked immunosorbent assay system. This technique exploits the hydrophobic properties of M-protein; the M-protein is selectively and rapidly adsorbed to polystyrene surfaces even in the presence of a 5000-fold excess of bovine serum albumin. Hyperimmune antiserum prepared to purified M-protein is used as the detecting reagent. All type A influenza viruses could be detected by this technique, type B influenza viruses reacted to a slight extent and Sendai virus (parainfluenza virus, type 1) did not react. Virus could be detected to levels as low as 3 ng. Purification of M-protein and preparation of hyperimmune sera from other related virus groups, such as type B influenza viruses, paramyxoviruses and rhabdoviruses should permit detection of these agents by a similar technique.

Enzyme-linked immunoassays for the detection of microbial antigens and their antibodies

Antibodies could be labeled with enzymes for use in histochemical staining procedures by enzyme-immunoassay (EIA). The use of EIA is an extension of previously used serological tests, using enzyme-labeled antibody or antigen to determine antibody content. Direct detection of antigen by EIA represents a more dramatic departure from previous methods based on culture. Also, the method has enabled detection of infectious agents that are difficult to cultivate, such as hepatitis A virus and rotavirus, or agents that cannot be cultivated, such as hepatitis B. The use of EIA tests for detection of microbial antigens provides an alternative to culture as a means for direct identification of a specific microbial agent. It also provides a means to detect microbial agents which have not been successfully propagated. The detection of circulating antigen or detection of antigen in other body fluids by EIA is more difficult than detection of antibody because of the sensitivity required, and because of interfering substances in specimens such as feces and respiratory secretions. For this reason, very few antigen detection assays have the sensitivity and specificity required to be used as a primary diagnostic test. The number of tests that have been developed, however, is impressive and because of the possibilities for rapid, specific diagnosis, the interest in antigen detection by EIA remains high.

Enzyme-linked immunosorbent assay for detection of streptolysin O antibodies

An enzyme-linked immumosorbent assay (ELISA), based upon the detection of streptolysin O antibodies in human sera, was developed. Disposable polystyrene tubes, sensitized with streptolysin O antigen, were used as the test vehicles. Corresponding antibodies, present in test sera, were detected by binding of the antibodies to goat anti-human immunoglobulin G conjugated to horseradish peroxidase. Demonstration of bound conjugate was accomplished by monitoring peroxidase activity spectrophotometrically at 450 nm, using 5-aminosalicylic acid as the indicator. A total of 97 human sera, previously analyzed by means of the anti-streptolysin O titration technique, were evaluated with the ELISA procedure. A direct quantitative relationship, found to be statistically significant, was demonstrated between Todd units and absorbance values obtained with ELISA.

Early diagnosis of herpes simplex virus encephalitis in childhood by the enzyme-linked immunosorbent assay

IgG antibody of cerebro-spinal fluid (CSF) and serum IgM antibody were determined by the enzyme-linked immunosorbent assay (ELISA) in 3 patients with herpes simplex virus encephalitis (HSVE). The ELISA detected the early rise of IgG antibody for herpes simplex virus (HSV) in CSF on the 3rd/4th day from onset of symptoms and IgM antibody in serum similarly on the 3rd/4th day, respectively. CSF albumin, IgG index and daily IgG synthesis during the early phase of HSVE showed significantly high levels. However, there was no significant increase of complement-fixing antibody and neutralizing antibody for HSV of serum and CSF in 2 of 3 patients. The ELISA turned out to be a more sensitive and convenient test for the early diagnosis of HSVE.

An enzyme-linked immunosorbent assay for rat prolactin

A sensitive and specific competitive enzyme-linked immunosorbent assay (ELISA) for rat prolactin was developed using reagents from the National Institute of Arthritis, Diabetes, Digestive Diseases and Kidney. In this assay soluble prolactin and prolactin adsorbed to a solid-phase support compete for rabbit anti-prolactin antibody binding sites. Therefore, a high concentration of soluble prolactin in the sample will result in a low concentration of antibody immobilized to the adsorbed prolactin. The immobilized antibody-prolactin complex is detected and quantified using goat anti-rabbit immunoglobulin G covalently conjugated to the enzyme horseradish peroxidase. Assay parameters were optimized by investigating the concentration of reagents and the reaction kinetics in each of the assay steps. The assay can be performed in 24 h. A sensitivity range of 0.06 to 6 ng in the region of 90 to 10% binding was obtained. Near 50% binding (0.6 ng), the intraassay coefficient of variation (CV) was 4.2% and the interassay CV was 7.6%. The correlation between radioimmunoassay and the ELISA was 0.868. Selected applications of the assay are described. The assay should prove a useful alternative to the radioimmunoassay in those instances where steps involving the use of 125I become limiting, for example, iodination facility and gamma counter availability or prolonged reagent storage.

Nitrocellulose-enzyme-linked immunosorbent assay (NC-ELISA) - a sensitive technique for the rapid visual detection of both viral antigens and antibodies

A modification of the enzyme-linked immunosorbent assay (ELISA) is described for sensitive and rapid direct visual detection of antigens of four adenoviruses (Ad) and anti-Ad antibodies using nitrocellulose (NC) membrane discs as high-capacity solid phase. The NC-ELISA was performed in microtitre plates containing NC-discs. Small amounts of crude supernatants from Ad-infected cells as antigen were bound to the discs. Additional binding capacity was blocked with an excess of bovine serum albumin. The subsequent reaction of virus antigen with specific rabbit antibody was visualized using alkaline phosphatase-conjugated anti-rabbit IgG and histochemical substrates. The sensitivity of the NC-ELISA for the detection of Ad-antigens was found to be 8-10-fold higher than a conventional ELISA using polystyrene solid phase supports. The sensitivity levels were estimated to be similar comparing NC-ELISA and tissue culture assay results. The quantitative determination of anti-Ad antibodies by NC-ELISA showed 8-fold higher sensitivity compared to microneutralization test. The NC-ELISA could detect purified immunoglobulin at a level of 1 ng using a direct test procedure and 10 ng using the indirect method. The detection limits are good compared to other highly sensitive assays. The use of crude antigen combined with high sensitivity and easy technical performance makes the NC-ELISA useful as a tool for rapid viral diagnosis.

A micro solid-phase radioimmunoassay for detection of herpesvirus type-specific antibody: specificity and sensitivity

The specificity and sensitivity of a micro solid-phase radioimmunoassay (micro-SPRIA) that detects type-specific IgG antibody to herpes simplex virus types 1 and 2 (HSV1 and HSV2) were evaluated. Glycoproteins VP123 (molecular weight, 123,000) of HSV1 and VP119 (molecular weight, 119,000) of HSV2 were found to display the greatest degree of antigenic type-specificity of several HSV antigens tested with the micro-SPRIA technique. When testing a group of sera, negative for anti-HSV antibodies by microneutralization, in the micro-SPRIA, a range of negative reactivities was noted, suggesting that cut-points should be determined for each antigen preparation. The micro-SPRIA detected appropriate antibody activity in patients with recurrent infection and a marked agreement was noted in comparison to detection of anti-HSV antibodies measured with the microneutralization test. The type-specificity of the micro-SPRIA was substantiated by the independence of test results using VP119 and VP123 antigens for a random group of positive sera. The assay is rapid, specific, and sensitive and allows the testing of multiple serum samples with a standardized set of reagents.

Immunoglobulin class of antibody to herpes simplex virus in patients with oral cancer

An enzyme-linked immunosorbent assay was used to measure antibody of the IgG, IgA, and IgM classes against Herpes simplex virus type 1 (HSV-1) in human sera. Patients with untreated oral cancer had higher levels of IgM antibody to HSV-1 than did either patients with acute or recurrent herpetic infections or age-matched control subjects. Levels of IgM antibody to cytomegalovirus and total serum IgM concentrations were similar in all groups. Patients who had been treated successfully for oral cancer more than one year earlier did not have higher levels of IgM antibody to HSV-1. The results are consistent with the hypothesis that cancer of the mouth is associated with expression of HSV-1 antigens that stimulate IgM rather than IgG antibody responses.

Frequency and specificity of varicella zoster virus IgM response

A direct ELISA was developed for determination of IgM antibody to varicella zoster virus (VZV). With this sensitive method VZV IgM antibodies were detected in all patients with a varicella and in 84% with a herpes zoster infection. All but one of 28 renal allograft recipients had previously had varicella. A primary infection was seen in the last patient, and reactivated infections in 11 of the others. The VZV IgM response seems to be specific since patients with a herpes simplex virus (HSV) infection and a heterotypic VZV IgG titer rise did not have detectable VZV IgM. An indirect enzyme-linked immunosorbent assay (ELISA) for detection of IgG antibodies has been used for serodiagnosis of VZV infections and to determine the immune status. After injection of zoster immune globulin, it was possible to measure passively transferred antibodies.

Decline in specificity of the ELISA due to storage of serum, and its recovery by adsorption with kaolin

Several laboratories have experienced problems with the enzyme-linked immunosorbent assay (ELISA) due to non-specific background binding of human sera, but no general solution has been introduced. In this study the ELISA was used to measure antibody to herpes simplex virus in human sera which had been stored at -20 degrees C for up to 3 years, and the specificity was assessed by comparing the absorbance achieved with the virus neutralization titer. The severity of background binding was minimal in sera which had been obtained recently, but increased with storage time and gradually eliminated the specificity of the assay. When sera were adsorbed with kaolin, background binding of all sera was markedly reduced and the specificity was restored.

Enzymes as versatile labels and signal amplifiers for monitoring immunochemical reactions

Enzymes have proven to be sensitive and versatile labels for immunochemical assays. The sensitivity of an enzyme label stems from its extraordinary catalytic power which in turn provides a great amplification of signals. Its versatility, however, stems from the fact that enzyme activity can be modulated by a number of substances. Enzyme labeled immunoassays can be divided into two categories: (a) heterogeneous and (b) homogeneous (non-separation). In the heterogeneous systems, the quantitation of the antibody bound and unbound fractions requires a physical separation of these two fractions, whereas the homogeneous or non-separation systems do not require such a separation. In the homogeneous systems, the unbound and antibody bound fractions can be distinguished functionally. A total of 11 unique principles used in the development of enzyme labeled immunoassays are described. The advantages, disadvantages and limitations of them are considered, as well as the future paths for research and developments.

Evaluation of solubilized herpes simplex virus membrane antigens in diffusion in gel-enzyme-linked immunosorbent assay (DIG-ELISA)

Cell membranes were prepared from herpes simplex virus (HSV) type 1-infected cells and solubilized with a low concentration of sodium deoxycholate. The supernatant after ultracentrifugation was used as antigen in a newly developed solid phase assay, diffusion in gel-enzyme-linked immunosorbent assay (DIG-ELISA). Antigen solubilization was almost complete, all HSV glycoproteins were represented, the yield of antigen in the solubilization process was high, and the presence of a detergent, sodium deoxycholate, did not interfere with the adsorption of antigen to the solid phase. DIG-ELISA was compared with the neutralization test for the determination of HSC antibodies and zone diameters showed a good correlation with the titre obtained by the neutralization test.

Herpes simplex encephalitis treated with adenine arabinoside

We report a case of a 5-year-old girl with herpes simplex encephalitis (HSE) who was treated with adenine arabinoside (ara-A). The characteristic symptoms consisted of headache and vomiting followed by progressive disturbance of consciousness. CT scan revealed a translucent area in the left temporal lobe. Seven days after the onset vigorous treatment including ara-A was initiated. She recovered without apparent toxicity or sequelae except for mild motor aphasia. Our experience suggests that ara-A is effective in the treatment of HSE if given early enough.

Antibody responses in humans to individual proteins of herpes simplex viruses

Sera from 231 women were used to examine their frequency of precipitation of various herpes simplex virus type 1 and 2 (HSV-1 and HSV-2) proteins and to determine if there was a rank order of immune responsiveness of humans to these HSV antigens. Radiolabeled viral proteins were reacted with serum and immune complexes isolated with staphylococcal protein A. Individual antigens were resolved by polyacrylamide gel electrophoresis and visualized by fluorography. As a group, these sera precipitated 31 HSV-1 and 27 HSV-2 proteins. HSV-1 polypeptides with molecular weights of 133,000, 99,000, and 82,000, as well as HSV-2 polypeptides with molecular weights of 131,000 and 101,000, were precipitated by essentially all sera that contained antibodies to HSV-1 and HSV-2. When attempts were made to order the viral proteins by constructing precipitation profiles ranking the antigens in patterns according to their frequency of precipitation, it was observed that the antigens were generally not ordered. Demographic analysis of the sera suggested that the differences in the number of proteins precipitated were associated with differences in age, education, age at first marriage, and income, which collectively may reflect the frequency of exposure to the virus.

Milk-specific antibody measurement by elisa: development of an assay

This paper describes the development of a simple, sensitive and specific enzyme-linked immunosorbent assay (ELISA) for the measurement of serum IgG, IgA and IgM antibodies to cow's milk protein. The specificity of this assay was determined by preparing immunosorbents of cow's milk and human serum albumin (HSA). Fractionation of the antiserum-enzyme label by gel filtration and affinity chromatography showed that the conjugate preparation contained moieties of antiserum-enzyme, and antiserum-enzyme polymers. The preparation also contained enzyme-enzyme and antiserum-antiserum conjugates. Purification of the labeled reagent did not improve the sensitivity. The reagents and conditions used have been analyzed for purposes of standardisation.

Use of the enzyme-linked immunosorbent assay (ELISA) for the estimation of serum antibodies in an influenza virus vaccine study

The value of the enzyme-linked immunosorbent assay (ELISA) for determining the serum antibody responses of volunteers following immunisation with various inactivated influenza virus vaccines was assessed, and the incidence of seroconversions, as measured by both haemagglutination-inhibition (HI) and ELISA response of the volunteers determined. ELISA was found to be more sensitive than the HI test in detecting serum antibodies, but was also less specific under the conditions used. With regard to efficacy, the whole virus vaccine proved to be more effective in inducing serum antibody in an unprimed population than either tween-ether split or subunit adsorbed vaccines, but the reverse situation held when the population was primed with respect to the antigen concerned.

Rapid solid-phase enzyme immunoassay for antibodies to viruses and other microbes: effects of polyethylene glycol

A rapid and sensitive solid-phase enzyme immunoassay (EIA) was developed for determination of serum antibodies, including addition of 4% (w/v) polyethylene glycol (PEG) to the diluent buffers. This modification accelerated the antigen-antibody reactions and made it possible to complete the assay within 2 h and to incubate at room temperature only. The enhancing effect of the polymer was particularly prominent in the second solid-phase immune reaction, the interaction between the antigen-bound antibody and the enzyme-labeled anti-immunoglobulin. The PEG-EIA procedure was successfully applied in the assay of antibodies to rubella, influenza A, herpes simplex and cytomegalo viruses, to Mycoplasma pneumoniae and Toxoplasma gondii.

Correlation of herpes simplex virus antibody titers and specific lymphocyte stimulation in adult blood donors

Antibody titers to herpes simplex virus type 1 in sera from healthy adult donors were assayed by complement fixation, microneutralization, and an enzyme immunoassay (ELISA). This last test proved to be the most sensitive method for antibody detection. It was estimated that ELISA antibody titers were up to 40-fold higher than neutralizing antibody titers and up to 100-fold higher than complement fixation antibody titers. Due to the higher sensitivity of ELISA, only 3 of 36 blood donors tested in this assay were shown to be seronegative, whereas 6 additional persons of the same group were termed seronegative by the microneutralization assay. Furthermore, four of the latter also did not respond in the complement fixation test. In vitro stimulation of peripheral lymphocytes by using a partially purified herpes simplex virus type 1 particle antigen was achieved for all seropositive blood donors. Only those three donors who were ELISA negative reacted negatively in this stimulation assay. From these results it may be concluded that ELISA is an appropriate method not only for rapid and sensitive antibody determination but also for selecting herpes simplex virus-negative patients.

Comparison of alkaline phosphatase and horseradish peroxidase conjugated antisera in the ELISA test for antibodies to reovirus 3, mouse hepatitis and Sendai viruses

The method of enzyme-linked immunoadsorbent assay (ELISA) has been applied to the detection of antibodies to reovirus 3, Sendai virus and mouse hepatitis virus (type 1), and the serological response of mice after infection has been followed for 28 days to investigate the earliest appearance of ELISA titres. This has been compared to the appearance of haemagglutination-inhibiting and complement-fixing antibodies.

Alkaline phosphatase conjugated antiserum produces the most sensitive and convenient ELISA for the murine viruses examined.

The effect of high antigen density on solid-phase radioimmunoassays for antibody regardless of immunoglobulin class

Human sera containing antibody to casein or to bovine serum albumin were used to assess the validity and utility of a solid-phase assay for quantitating antibody activity. Rabbit anti-human immunoglobulin radiolabeled with 125I and capable of reacting with all human immunoglobulin classes was used to detect antibody bound to antigen immobilized to polystyrene tubes by a new covalent technique. This method results in very high antigen concentrations in highly stable association with polystyrene tubes. Kinetic and absorption studies demonstrated that low avidity antibodies are better detected when antigen is immobilized by the covalent method than when passively adsorbed. Conditions are described for minimizing artifactual interactions and for obtaining results similar to those obtained with conventional, liquid-phase assays. Failure to reach equilibrium in solid-phase assays and other problems are proposed to explain, in part, the inability to obtain a better correlation between solid- and liquid-phase immunoassays.

Enzyme-linked immunosorbent assay for herpes simplex virus tumor-associated antigen

The antibodies against herpes simplex virus (HSV) tumor-associated antigen (TAA) in human sera were investigated by the enzyme-linked immunosorbent assay (ELISA). By combining the findings of antibody levels in many human sera, a significant level of discrimination between normal and cancer sera could be reached. Thus, 57 of 74 pathological sera had increased levels of antibodies against HSV-TAA antigen as compared to 26 of 512 normal sera. A significant correlation between the ELISA values and complement fixing (CF) and radioimmunoassay (RIA) values was also found. The results suggest that serodiagnosis with the ELISA test may therefore be of some use in the detection of specific antibodies against HSV-TAA antigen in sera of cancer patients.

Enzyme linked immunosorbent assay (ELISA) for determination of IgG antibodies to human cytomegalovirus

A solid-phase enzyme linked immunosorbent assay (ELISA) for determination of IgG antibodies to cytomegalovirus (CMV) is described. The assay used purified CMV and extracts of CMV infected cells as antigen. Antigens were desiccated onto the bottom surface of polystyrene microcuvettes. The antibodies bound to the antigens were assayed by anti-IgG-alkaline phosphate conjugate followed by addition of the enzyme substrate. Titration curves have been obtained from the sera of 35 blood donors and of 23 patients. Comparison of results obtained by ELISA with those obtained by complement fixation (CF) shows that there is agreement between the tests. Both purified CMV and extracts of CMV infected cells were found to be suitable antigens. Purified CMV was of value particularly in those sera which show high reactivity against control antigen. The ELISA technique described is approximately 412 to 548 times more sensitive than the CF test when purified CMV or extracts of CMV infected cells, respectively, are used as antigens. No significant heterotypic rise to CMV was observed by ELISA in three sets of sera with seroconversion to herpes simplex virus. The ELISA technique gives objective results, is easily performed, and may be adaptable as a routine test both for serological diagnosis of CMV infection and for screening of the general population.

Enzyme immunoassay for measurement of antibodies to herpes simplex virus infection: comparison with complement fixation, immunofluorescent-antibody, and neutralization techniques

An enzyme immunoassay (EIA) was developed for detecting antibody to herpes simplex virus, and the results were compared with those of complement fixation, indirect immunofluorescent-antibody, and plaque reduction neutralization tests. Test sera showed very little nonspecific reactivity even at a starting dilution as low as 1:10. EIA results showed excellent correlation with results obtained by the neutralization test, with an average gain in sensitivity of 1.65. EIA proved very useful in detecting current herpes simplex virus infection, and antibody appeared in all cases soon after clinical onset. EIA appears to be a rapid, sensitive, and specific method for routine demonstration of herpes simplex virus antibody in a clinical setting.

Solid-phase radioimmunoassay techniques for the detection of African swine fever antigen and antibody

A solid phase radioimmunoassay (RIA) has been successfully developed to measure both African swine fever virus (ASFV) antigen and antibody. Studies show that the assay is reproducible and will detect limiting antigen concentrations equivalent to 50--500 HAD50/ml. Both direct and indirect antibody RIA have been developed and have proved to be approximately 100 times fore sensitive than the complement fixation test at present available and 1000 times more sensitive than the immuno-electro-osmophoresis test for the detection of ASFV antibody.

Immobilization of viral antigens on filter paper for a [125I]staphylococcal protein A immunoassay: a rapid and sensitive technique for detection of herpes simplex virus antigens and antiviral antibodies

A new technique is described for the rapid detection and quantitation of herpes simplex virus (HSV) antigens and antiviral antibodies. It involves immobilization of HSV antigens on filter paper discs and subsequent analysis by 125I-labeled staphylococcal protein A (SPA) radioimmunoassay. A specially designed 96-well filtration device is employed which serves both as an incubation chamber and as a filtration manifold. It is rapid, simple, sensitive and specific, and requires only small volumes of antiserum and few target cells. The results may be readily and objectively quantitated. This technique permits the simultaneous assay of a large number of specimens in less than 1 h. Its sensitivity is considerably greater than that of other currently used immunologic techniques, and it is amenable to automation. These characteristics suggest that this [125I]SPA immunofiltration technique may be applicable to the rapid diagnosis of viral infections.

Enzyme immunoassays with special reference to ELISA techniques

In this review outlines are given on various types of enzyme immunoassay. The applications to such enzyme immunoassays, especially ELISA, are dealth with in detail. It is concluded that these techniques have high sensitivity and will be suitable in due course as routine laboratory tests.