A major DNA binding protein encoded by BALF2 open reading frame of Epstein-Barr virus (EBV) forms a complex with other EBV DNA-binding proteins: DNAase, EA-D, and DNA polymerase

A major 135-kDa DNA binding protein (mDBP) encoded by the BALF2 open reading frame of Epstein-Barr Virus (EBV) is known to be an essential protein for the induction of the lytic cycle. The present investigation was carried out to know whether this protein forms a complex in vivo with other viral DNA binding proteins (DBP) involved in DNA replication: DNA polymerase, EA-D (diffused early antigen), and DNAase. Immunoprecipitation assays followed by mono- and two-dimensional electrophoresis showed that mDBP forms a complex with these three DBP. Other complexes were also found such as EA-D/DNAase, DNA polymerase/DNAase, and DNA polymerase/EA-D. The complexed forms already exist in the early stage of EBV cycle before DNA synthesis is induced in the EBV producer P3HR-1 cell line. The exonuclease activity encoded by DNAase was found to be inhibited when this enzyme complexed with mDBP, while the EBV DNA polymerase retained its activity in the complexed form with mDBP. Our results suggest that these complexes already present before DNA synthesis are necessary for EBV DNA synthesis.

Presence of Epstein-Barr virus latency type III at the single cell level in post-transplantation lymphoproliferative disorders and AIDS related lymphomas

AIMS

To investigate the expression pattern of Epstein-Barr virus (EBV) latent genes at the single cell level in post-transplantation lymphoproliferative disorders and acquired immunodefiency syndrome (AIDS) related lymphomas, in relation to cellular morphology.

METHODS

Nine post-transplantation lymphoproliferative disorders and three AIDS related lymphomas were subjected to immunohistochemistry using monoclonal antibodies specific for EBV nuclear antigen 1 (EBNA1) (2H4), EBNA2 (PE2 and the new rat anti-EBNA2 monoclonal antibodies 1E6, R3, and 3E9), and LMP1 (CS1-4 and S12). Double staining was performed combining R3 or 3E9 with S12.

RESULTS

R3 and 3E9 anti-EBNA2 monoclonal antibodies were more sensitive than PE2, enabling the detection of more EBNA2 positive lymphoma cells. Both in post-transplantation lymphoproliferative disorders and AIDS related lymphomas, different expression patterns were detected at the single cell level. Smaller neoplastic cells were positive for EBNA2 but negative for LMP1. Larger and more blastic neoplastic cells, sometimes resembling Reed-Sternberg cells, were LMP1 positive but EBNA2 negative (EBV latency type II). Morphologically intermediate neoplastic cells coexpressing EBNA2 and LMP1 (EBV latency type III), were detected using R3 and 3E9, and formed a considerable part of the neoplastic population in four of nine post-transplantation lymphoproliferative disorders and two of three AIDS related lymphomas. All samples contained a subpopulation of small tumour cells positive exclusively for Epstein-Barr early RNA and EBNA1. The relation between cellular morphology and EBV expression patterns in this study was less pronounced in AIDS related lymphomas than in post-transplantation lymphoproliferative disorders, because the AIDS related lymphomas were less polymorphic than the post-transplantation lymphoproliferative disorders.

CONCLUSIONS

In post-transplantation lymphoproliferative disorders and AIDS related lymphomas, EBV latency type III can be detected by immunohistochemistry in a subpopulation of tumour cells using sensitive monoclonal antibodies R3 and 3E9. Our data suggest that EBV infected tumour cells in these lymphomas undergo gradual changes in the expression of EBV latent genes, and that these changes are associated with changes in cellular morphology.

P32/TAP, a cellular protein that interacts with EBNA-1 of Epstein-Barr virus

The Epstein-Barr virus (EBV) EBNA-1 protein has a central role in the maintenance of a latent EBV infection and is the only virus-encoded protein expressed in all EBV-associated tumors. EBNA-1 is required for replication of the episomal form of the latent viral genome and transactivates the latency C and LMP-1 promoters. The mechanisms by which EBNA-1 performs these functions are not known. Here we describe the cloning, expression, and characterization of a cellular protein, P32/TAP, which strongly interacts with EBNA-1. We show that P32/TAP is expressed at high levels in Raji cells and is synthesized as a proprotein of 282 amino acids (aa) that is posttranslationally processed by a two-step cleavage process to yield a mature protein of 209 aa. It has been previously reported that P32/TAP is expressed on the cell surface. Our transient expression assays detected full-length P32/TAP (1-282 aa) in the cytoplasm while mature P32/TAP protein localized to the nucleus. Three lines of evidence support P32/TAP interaction with EBNA-1. First, in the yeast two-hybrid system we mapped two interactive N-terminal regions of EBNA-1, aa 40-60 and aa 325-376, each of which contains arginine-glycine repeats. These regions interact with the C-terminal half of P32/TAP. Second, the full-length cytoplasmic P32/TAP protein can translocate nuclear EBNA-1 into the cytoplasm. Third, P32/TAP co-immunoprecipitated with EBNA-1. We have confirmed that a Gal4 fusion protein containing the C-terminal region of P32/TAP (aa 244-282) transactivates expression from a reporter containing upstream Gal4-binding sites. Deletion of the P32/TAP interactive regions of EBNA-1 severely diminished EBNA-1 transactivation of FRTKCAT in transient expression assays. Our data suggest that interaction with P32/TAP may contribute to EBNA-1-mediated transactivation.

Activated cytotoxic T cells as prognostic marker in Hodgkin's disease

Although the results of treatment of Hodgkin's disease (HD) have improved considerably in the last decades, the disease remains fatal in a minority of patients. We have recently shown that numbers of activated cytotoxic T cells (CTLs), present in tumor biopsy specimens, differ considerably among individual HD patients. Because CTLs are the major effector cells in elimination of neoplastic cells, we investigated whether the number of activated CTLs is related to the clinical outcome of the individual patient with HD. Activated CTLs present in tumor biopsy specimens of patients with nodular sclerosis or mixed cellularity HD were identified by immunohistochemistry using an antibody directed against granzyme B (GrB), a major constituent of the cytotoxic granules of activated CTLs and natural killer cells, and an antibody directed against CD8. The presence of a high percentage of GrB+ lymphocytes was found to be an unfavorable prognostic marker. The large majority of GrB+ cells were also CD8+, indicating that these cells are activated CTLs. Prognosis was found to decrease with increasing percentages of GrB+ lymphocytes. Optimal discrimination between patients with good and poor prognosis was obtained when the threshold was set at 15% GrB+ cells; 6 of 10 patients with > or = 15% GrB+ lymphocytes died as a result of the disease, as compared with 6 of 70 patients with less than 15% GrB+ lymphocytes (P < .0001). In stage-2 patients, the percentage of GrB+ lymphocytes retained its predictive value in a multivariate analysis including histology, sex, age, erythrocyte sedimentation rate, and the presence of B symptoms as covariables. In addition, patients with > or = 15% GrB+ lymphocytes had a shortened progression-free survival time (P = .002). We conclude that a high percentage of activated CTLs present in biopsy material of HD patients is a strong indicator for an unfavorable clinical outcome.

Expression of epstein-barr virus encoded nuclear antigen 1 in benign and malignant tissues harbouring EBV

AIMS

To determine levels of expression of Epstein-Barr virus (EBV) nuclear antigen 1 (EBNA1) in benign and malignant tissues harbouring EBV in relation to EBNA1 promoter usage.

METHODS

Expression of EBNA1 was investigated by means of immunohistochemistry using a mixture of two EBNA1 specific monoclonal antibodies, 1H4-1 and 2B4-1. The presence of EBV was detected by EBER1/2 RNA in situ hybridisation. Detection of promoter specific EBNA1 transcripts was by RT-PCR analysis.

RESULTS

EBNA1 positive cells were detected in all 20 EBV associated B cell lymphomas, 18 of which had arisen in immunocompromised patients; in eight of nine EBV associated T cell lymphomas; in 11 of 27 EBV positive cases of Hodgkin's disease; and in reactive lymphoid tissue harbouring EBV, including four cases of infectious mononucleosis. A diffuse EBNA1 staining pattern was observed in most of the EBV associated B cell lymphomas and was comparable with the EBER1/2 staining pattern. In the T cell lymphomas the number of EBNA1 positive cells was usually considerably less than the number of EBER1/2 positive ones. RT-PCR analysis revealed that in tumours with restricted EBNA1 expression-that is, T cell lymphomas and Hodgkin's disease lesions, EBNA1 transcripts were usually generated only by the F/Q promoter, whereas in B cell lymphomas EBNA1 transcripts were usually generated by both the C/W and F/Q promoters.

CONCLUSIONS

EBNA1 is expressed in all types of tissue harbouring EBV, but the level of expression varies greatly. This may be the result of differential promoter usage.

Two 21-kilodalton components of the Epstein-Barr virus capsid antigen complex and their relationship to ZEBRA-associated protein p21 (ZAP21)

The viral capsid antigen complex of Epstein-Barr virus (EBV), an important serodiagnostic marker of infection with the virus, consists of at least four components, with molecular masses of 150, 110, 40, and 21 kDa. Here we show that the 21-kDa component of the viral capsid antigen consists of products of two EBV genes, BFRF3 and BLRF2. Both products were expressed from late transcripts, were recognized by human antisera, and were present in virions. The BFRF3 product, but not that of BLRF2, fulfilled the definition of ZEBRA-associated protein p21 (ZAP21). In cells in which EBV was lytically replicating, BFRF3 protein was coimmunoprecipitated together with ZEBRA by a rabbit antiserum directed against amino acids 197 to 245 of BZLF1. In EBV-negative cells cotransfected with BZLF1 and BFRF3 expression vectors, BFRF3 was also coimmunoprecipitated with this antiserum. Although this antiserum could not detect BFRF3 on an immunoblot, it was able to immunoprecipitate BFRF3 in the absence of ZEBRA expression. The rabbit antiserum to amino acids 197 to 245 of BZLF1 was found to detect the same epitope at the carboxy end of BFRF3 as was recognized by rabbit antiserum to BFRF3 itself. Thus, coimmunoprecipitation of BFRF3 p21 with ZEBRA appeared to be due to cross-reactivity of the immunoprecipitating antiserum rather than to direct association of ZEBRA and BFRF3 p21.

Characteristics of viral protein expression by Epstein-Barr virus-infected B cells in peripheral blood of patients with infectious mononucleosis

The frequency of Epstein-Barr virus (EBV) antigen-positive B cells in the peripheral blood of patients with infectious mononucleosis compared with that for latently EBV-infected individuals was examined by immunocytochemistry. B cells positive for Epstein-Barr nuclear antigen (EBNA) 1, EBNA2, and latent membrane protein were frequently found in all peripheral B lymphocyte preparations from 25 patients suffering for 3 to 28 days from infectious mononucleosis by using monoclonal antibodies and the alkaline phosphatase anti-alkaline technique. There was a significant decrease in the number of positive B cells during the course of disease. EBNA1-positive B cells were detected in 0.01 to 2.5% of total B cells (median, 0.8%), EBNA2-positive B cells were detected in 0.01 to 4.5% of total B cells (median, 0.9%), and latent membrane protein-positive B cells were detected in 0.01 to 1.8% of total B cells (median, 0.5%), depending on the duration of clinical signs. In contrast, we did not find any EBNA1- or EBNA2-positive B cells in 2 x 10(6) peripheral blood B lymphocytes of 10 latently EBV-infected individuals, whereas aliquots of the same cell preparations were EBV DNA positive by a PCR assay. Therefore, it appears to be possible to detect infectious mononucleosis by immunocytochemical determination of latent EBV products, which might be of relevance for the diagnosis of EBV reactivations in immunosuppressed patients.

Human antibody reactivity against the lower matrix protein (pp65) produced by cytomegalovirus

The lower matrix protein (pp65) is a major product of many laboratory strains of cytomegalovirus (CMV). It is thus an integral part of many CMV serological assays based on native antigen. Recombinant fragments of pp65 have previously been investigated for their usefulness in more-defined assays. The latter antigens have, however, failed to develop a positive response with serum samples derived from a substantial number of infected individuals. Here we show that the human humoral immune response to CMV pp65 is highly diverse and recognizes at least seven distinct but in some cases partly overlapping epitopes. Most of these epitopes could not be mimicked by any of the investigated recombinant or synthetic antigens. Furthermore, when we investigated the ability of human CMV-seropositive serum samples to block the reactivity of pp65-specific antibodies recognizing five different epitopes within pp65, it was evident that several sera did not contain significant levels of antibodies against any of these or overlapping structures. It was thus concluded that the antibody response against CMV pp65 is weak in some CMV-infected individuals, making this antigen unsuitable for use alone in serological screening systems for CMV infection.

Significance of the immune response to a major, conformational B-cell epitope on the hepatitis C virus NS3 region defined by a human monoclonal antibody

The nonstructural protein NS3 of hepatitis C virus (HCV) possesses two enzymatic domains which are thought to be essential for the virus life cycle: an N-terminal serine-type proteinase, responsible for the processing of nonstructural polypeptides, and a C-terminal nucleoside triphosphatase/helicase, presumably involved in the unwinding of the viral genome. The human antibody response to NS3 usually appears early in the course of HCV infection and is predominantly directed against the carboxyl-terminal portion; however, its fine specificity and clinical significance are largely unknown. We have generated a human monoclonal antibody (hMAb), designated CM3.B6, from a cloned B-cell line obtained from the peripheral blood of a patient with chronic HCV infection, which selectively recognized the purified NS3 protein expressed in bacteria or in eukaryotic cells transfected with full-length or NS3 cDNA. Fine-specificity studies revealed that CM3.B6 recognized a 92-amino-acid sequence (clone 8, amino acids 1363 to 1454) selected from an NS3 DNase fragment library but failed to bind to 12-mer peptides synthesized from the same region, suggesting recognition of a conformational B-cell epitope. Experiments using deletion mutants of clone 8 and competitive inhibition studies using a panel of NS3 peptide-specific murine MAbs indicated that limited N-terminal and C-terminal deletions resulted in a significant reduction of hMAb binding to clone 8, thus identifying a minimal antibody binding domain within clone 8. Competition experiments showed that binding of CM3.B6 to the NS3 protein was efficiently inhibited by 39 of 44 (89%) sera from HCV-infected patients, suggesting that the hMAb recognized an immunodominant epitope within the NS3 region. More importantly, recognition of the sequence defined by CM3.B6 appeared to accurately discriminate between viremic and nonviremic anti-HCV positive sera, suggesting potentially relevant clinical applications in the diagnosis and treatment of HCV infection.

Localization and diagnostic application of immunodominant domains of the BFRF3-encoded Epstein-Barr virus capsid protein

The Epstein-Barr virus (EBV) open reading frame BFRF3 encodes a viral structural capsid protein or tegument protein, VCA p18, that is highly immunogenic in humans. In this study, a cluster of immunodominant epitopes in the C-terminus of VCA p18 has been identified. These epitopes were combined into a single synthetic peptide that was analyzed for diagnostic value in an ELISA. This VCA combined peptide appeared to be an excellent VCA marker with remarkable applications for IgG- and IgM-related EBV diagnostics. The combined peptide reacted with 95% of 159 sera that were IgG VCA-positive by immunofluorescence assay. In addition, 95% of sera from 67 persons with confirmed infectious mononucleosis were positive for IgM antibodies to this VCA combined peptide. An IgG-specific seroconversion could be demonstrated by subsequent serum samples during the acute phase of primary EBV infections. Although 97% of the tested sera from nasopharyngeal carcinoma patients had IgG antibodies reacting positively with the VCA combined peptide, only 61% contained IgA anti-VCA combined peptide.

Detection of hepatitis C virus antigen by immuno-histochemical staining: a histological marker of hepatitis C virus infection

Hepatitis C virus has been recognized as a major cause of non-A, non-B viral hepatitis. Although serologic tests have been commercialized, no specific histological or immuno-histochemical markers for hepatitis C virus infection are available for routine use. In an effort to detect hepatitis C virus antigen in liver tissue we investigated the immuno-reactivity to monoclonal antibodies on frozen liver tissue from a chimpanzee and patients with chronic non A, non B hepatitis. Monoclonal antibodies were developed in mice immunized with a synthetic peptide derived from hepatitis C virus core antigen. One monoclonal antibody was reactive and showed typical cytoplasmic granules in chimpanzee hepatocytes. Using this monoclonal antibody a similar staining pattern was found in the liver biopsies of 21 out of 28 chronic non-A, non-B hepatitis patients, positive for hepatitis C virus-RNA and anti-HCV. The granular immuno-reactivity was abolished after pre-incubation of this monoclonal antibody with infected chimpanzee liver or with hepatitis C virus synthetic peptide but not with normal chimpanzee or human liver tissue. There was no reactivity in four patients with hepatitis C virus-RNA-negative, anti-HCV-positive chronic non-A, non-B hepatitis, in 11 patients with chronic type B hepatitis or in 12 hepatitis C virus-RNA-negative, anti-HCV-negative patients with various liver diseases. However, staining was found in three out of four additional chronic type B hepatitis patients suspected of co-infection with non-A, non-B agents.(ABSTRACT TRUNCATED AT 250 WORDS)

Expression of Epstein-Barr-virus-related nuclear antigens and B-cell markers in lymphomas of SIV-immunosuppressed monkeys

Simian-immunodeficiency-virus(SIV)-infected cynomolgus monkeys develop B-cell lymphomas in approximately one third of the cases. We have now studied the expression of cynomolgus-Epstein-Barr-virus(cyno-EBV) nuclear antigens in 13 cyno-EBV-carrying SIVsm-associated monkey lymphomas and established cell lines from 3 of these tumors. Immunoblots of cell lysates were probed with polyspecific and monospecific reagents directed against human EB-virus EBNAI-6, and against the membrane protein LMPI. An EBNA2-cross-reacting protein was demonstrated in 8 lymphoma tissues (8/13) and in the 3 cell lines derived from the tumors. All tumors expressed a polypeptide with 50 to 55 kDa molecular weight, which cross-reacted with some antibodies to EBNAI. Absorption experiments with normal monkey tissue showed that this polypeptide was specific for the cyno-EBV-carrying lymphoma cells. Equivalents of EBNA3-6 and LMPI could not be detected. Immunophenotypical characterization showed that the monkey lymphomas were similar to human HIV-associated B-cell lymphomas. Malignant B-cell lymphomas in experimentally SIVsm-infected cynomolgus monkeys can be a model for EBV-associated lymphomagenesis in immunodeficiency states.

Separation of the complex DNA binding domain of EBNA-1 into DNA recognition and dimerization subdomains of novel structure

EBNA-1 is essential for replication of the latent episomal form of the Epstein-Barr virus genome and is involved in regulation of viral latency promoters. EBNA-1 activity is mediated through direct DNA binding. The DNA binding and dimerization functions of EBNA-1 have previously been located to a carboxy-terminal domain, amino acids (aa) 459 to 607. To identify and define the subdomains for these two functions, we created an extensive series of deletions and point mutations in an EBNA-1 (aa 408 to 641) background. The ability of the EBNA-1 mutants to heterodimerize with a wild-type EBNA-1 (aa 459 to 641) Immunoprecipitation assays with a monoclonal antibody, EBNA.OT1x, that recognizes EBNA-1 (aa 408 to 641) but not EBNA-1 (aa 459 to 641). These experiments revealed that mutations affecting dimerization occurred over two separate regions, aa 501 to 532 and aa 554 to 598. DNA binding was tested in mobility shift assays against a panel of oligonucleotide-binding sites. Dimerization was a prerequisite for DNA binding. The DNA recognition domain was localized to a separate region, aa 459 to 487, upstream of the dimerization domain. EBNA-1 variants carrying substitutions at aa 467 and 468 and at aa 477 gave a pattern of binding to mutant oligonucleotide probes that implicates these particular amino acids in DNA recognition. EBNA-1 appears to utilize novel mechanisms for both DNA recognition and dimerization since neither domain conforms to previously described structural motifs.

Epstein-Barr virus gene expression in oral hairy leukoplakia

A combination of Northern blotting and sequencing of clones from a cDNA library constructed using RNA isolated from oral hairy leukoplakia (OHL) has been used to study Epstein-Barr virus (EBV) gene expression in this AIDS-associated lesion, the only accessible source of in vivo-replicating EBV. Because of the limited amount of RNA available, Northern blotting was only useful for detection of very abundant EBV transcripts in the OHL biopsies. Analysis of cDNA clones containing the BdRF1, BCRF1, gp350/220, BARF0, and BKRF4 reading frames and further characterization of RNA structures spanning BCRF1 (viral IL-10) in lymphocytes infected with EBV has provided a preliminary comparison of some virus replicative gene expression in its two main host cell types. No expression of EBNA-1, EBNA-2, or EBNA-3A RNA was detected in the oral hairy leukoplakia cDNA library.

Gene mapping and expression of two immunodominant Epstein-Barr virus capsid proteins

The genomic localization of two immunodominant genes encoding two proteins of the Epstein-Barr virus capsid antigen (VCA) complex, VCA-p18 and VCA-p40, has been identified. For that purpose, lambda gt11-based cDNA libraries were constructed from HH514.c16 cells induced for virus production. The libraries were screened with a monoclonal antibody, EBV.OT41A, directed against VCA-p40 or with affinity-purified human antibodies against VCA-p18. Sequencing of the inserts of positive plaques showed that VCA-p18 and VCA-p40 are encoded within open reading frames (ORFs) BFRF3 and BdRF1, respectively. Peptide scanning analysis of the predicted protein of ORF BdRF1 resulted in defining the epitope of monoclonal antibody EBV.OT41A at the C-terminal region. The dominant VCA-p18 reactivity of human sera can be completely inhibited by preadsorption with Escherichia coli-expressed BFRF3-beta-galactosidase. Serum of a rabbit immunized with BFRF3-beta galactosidase reacts with a VCA-specific protein of 18 kDa. In addition, BFRF3-beta-galactosidase affinity-purified antibodies react with VCA-p18 of virus-producing cells (HH514.c16). Complete inhibition of viral DNA polymerase activity by phosphonoacetic acid is associated with the absence of RNAs and protein products of both ORFs, indicating that VCA-p18 and VCA-p40 are true late antigens.

Identification and molecular characterization of two diagnostically relevant marker proteins of the Epstein-Barr virus capsid antigen complex

The molecular specificity of the IgG response against Epstein-Barr virus (EBV) was studied in 345 randomly collected sera of normal healthy individuals. The sera were tested on immunoblots containing antigens of the cell line HH514.c16 (a superinducible derivate of P3HR1), noninduced or induced for the expression of early antigens (EA) or viral capsid antigens (VCA), and from the EBV-negative cell line Ramos-Nut. This study reveals a remarkable similar antigen recognition pattern of IgG class antibodies in sera of healthy EBV carriers. The protein bands recognized predominantly have molecular weights of 18 kD, 36/38 kD, 40 kD, 72 kD, and 160 kD. The 72 kD and 36/38 kD bands were identified as EBNA1 and "Zebra," respectively, using reading frame-specific antisera. The bands at 160 kD (major capsid protein), 40 kD, and 18 kD were identified as VCA-class proteins. Of all EBV-seropositive sera tested, 98% reacted with either p18 or p40 or both. The synthesis of the antigens p18 and p40 was inhibited by phosphonoacetic acid, indicating that these were true late proteins. The detection of p18 and p40 in purified virion and capsid preparations confirms that these proteins are structural components of viral capsid antigen complex.

Purification and quantification of recombinant Epstein-Barr viral glycoproteins gp350/220 from Chinese hamster ovary cells

Truncated Epstein-Barr virus (EBV) membrane antigen gp350/220 (EBV-MA) lacking the membrane anchor was expressed and secreted into the medium of recombinant Chinese hamster ovary cells that had been cultured in Plasmapur hollow-fibre modules using defined serum-free medium. The EBV-MA in the medium was concentrated by 70% (w/v) ammonium sulphate precipitation and subsequently purified by immunoaffinity chromatography using an anti-EBV-MA (EBV.0T6) monoclonal antibody (mAb) column. Adsorbed antigen was eluted with 3 M MgCl2 in phosphate-buffered saline, concentrated by Mono Q anion-exchange chromatography and analysed by sodium dodecyl sulphate-polyacrylamide gel electrophoresis, silver staining and Western blotting using EBV-positive serum and anti-EBV-MA specific mAbs. Monospecific polyclonal rabbit antibodies against the purified EBV-MA were raised and purified by protein G affinity chromatography. For the measurement of EBV-MA antigen levels a sandwich enzyme-linked immunosorbent assay using rabbit polyclonal antibodies and a horseradish peroxidase-conjugated anti-MA mAb was developed having a detection level of 10 ng/ml.

New oligopeptide immunoglobulin G test for human parvovirus B19 antibodies

A new, highly sensitive and specific enzyme immunoassay using oligopeptides as antigen (enzyme-linked immunosorbent assay [ELISA] B19-OP) for detecting parvovirus B19-specific immunoglobulin G (IgG) was established. As antigens, B19-specific oligopeptides of 24 and 30 kDa derived from a 196-kDa fusion protein of beta-galactosidase and viral capsid protein (VPI) of B19 after CNBr cleavage and separation by high-pressure liquid chromatography were used. Of 139 serum specimens tested in parallel for anti-B19 IgG by standard ELISA using B19 particles as antigen and by ELISA B19-OP, 73 (52.5%) were positive and 63 (45.3%) were negative in both tests, and 3 (2.2%) were negative by standard ELISA but positive by ELISA B19-OP and by immunoblot. By using ELISA B19-OP, it was possible to detect anti-B19 IgG in an asymptomatic blood donor 4 weeks after acute infection, and anti-B19 IgG titers of 10(-5) could be measured in convalescent-phase sera.

Rapid diagnosis of genital herpes simplex infection by an indirect ELISA method

Herpes simplex virus (HSV) detection was performed by a rapid ELISA antigen detection method in a small field trial, and the results were compared to the results of ordinary cell culture isolation. Swabs from 54 patients, suffering from clinically suspected genital HSV infection, were examined by both methods. In 49 samples the results were identical. Three samples were negative by ELISA, but HSV was isolated by culture, while two samples were positive by ELISA, but negative by culture. Compared to the culture results, the ELISA method had 87.5% sensitivity and 93.3% specificity. Most culture positive samples were identified within two (54%) or three (75%) days, and all within six days after inoculation. The ELISA method turned out as a good and easy method for rapid detection of genital HSV infections.

Epstein-Barr virus specific marker molecules for early diagnosis of infectious mononucleosis

The molecular specificity of the antibody response against Epstein-Barr Virus (EBV) is studied in patients with acute primary EBV-infection, i.e. infectious mononucleosis syndrome. Using the immunoblot technique both IgM and IgG antibody responses are studied in sera obtained serially until week 20 after onset of symptoms. Healthy seropositive blood donors are used as control. Antigens are prepared from virus producer cell lines B95-8, P3HR1 and HH514-c16 (a superinducible derivative of P3HR1), induced for the expression of early antigens (EA) or viral capsid antigens (VCA) and from the EBV-negative cell lines BJAB and RAMOS. The 'WC'-serum, described by Edson et al. (J. Immunol. 130, 1983) is used to characterize EA- and VCA-specific polypeptides and to define their subcellular location. The immunoblot studies reveal an enormous diversity in EBV-specific polypeptides recognised by different individual patients, both for IgM and IgG. In addition, these patterns were markedly different from those found with control blood donor sera. The latter predominantly recognised bands at 72 kDa (EBNA) and 41 and 18 kDa respectively (both VCA components). Despite the great individual variation observed, EA-specific polypeptides at 138 kDa and at 45-52 kDa were recognised by both IgM and IgG antibodies in first serum samples of all patients tested.

Development of an antibody-capture IgM-enzyme-linked immunosorbent assay for diagnosis of acute Epstein-Barr virus infections

An anti-EBV IgM-ELISA was developed using the antibody-capture principle, to be used for the diagnosis of acute infectious mononucleosis (IM). The test was based on anti-human IgM-coated microtiter plates; nuclei of EBV producer cells were used for antigen; conjugate was prepared by labeling sheep anti-EBV IgG with horseradish peroxidase. The specificity of the anti-EBV IgM-ELISA was studied with a panel of sera from acute infections with hepatitis A virus, rubella virus, Toxoplasma gondii and cytomegalovirus, and sera positive for rheumatoid factors, positive for antinuclear antibodies, as well as with sera from normal blood donors and pregnant women. Specificity in these panels was 98.4%. In a clinical study with 449 sera from patients with IM-like symptoms, 109 of 109 confirmed patients were detected by the anti-EBV IgM-ELISA. Specificity of the anti-EBV IgM-ELISA in this clinical study was 99.7%. The anti-EBV IgM-ELISA detected several acute EBV patients who had negative heterophile antibody titers.

Epitope-mapping on the Epstein-Barr virus major capsid protein using systematic synthesis of overlapping oligopeptides

Systematic solid-phase synthesis of all possible overlapping nonapeptides of the 1381 amino acid sequence of the Epstein-Barr virus major capsid protein (EBV-MCP) was used to identify the position of linear antigen epitopes on this protein as recognised by human polyclonal antisera. Antisera were selected for reactivity with EBV-MCP on immunoblots. The results show that antibodies from different individual donors may recognise EBV-MCP through binding to a variety of different epitopes. These epitopes are localized at random over the protein backbone though some non-binding areas are also present. In addition, ten 'hot-spots' were identified containing closely-spaced reactive peptides (epitope-clusters) recognised by most (greater than or equal to 70%) individuals. No significant correlation was found between the actual location of these epitope-clusters and computer predictions using either hydrophilicity plots, secondary structure plots or a combination of (additional) parameters. Epitope-clusters generally were located in regions of indifferent or hydrophilic nature and mostly contained predicted beta-turn configurations. Only one epitope-cluster was located within a region of sequence homology with the MCPs of herpes simplex virus type 1 and varicella-zoster virus. The present study demonstrates the potential of using systematic peptide synthesis to define serologically relevant linear epitopes on large and relatively unexplored viral polypeptides.

A sensitive enzyme-linked immunosorbent assay for the detection of herpes simplex virus antigens

A sandwich ELISA for the detection of herpes simplex virus (HSV) antigens was developed using sheep anti-HSV F(ab')2 fragments for capture and an indirect antibody system for detection. Current detection limits are 0.5 ng protein for HSV1 and 1.5 ng protein for HSV2. This compares to a single HSV1-infected Vero-cell in a background of 10(6) non-infected cells or 10 plaque forming units (PFU) of HSV1 in culture supernatants as determined in separate experiments. Limiting dilution experiments show that one PFU of HSV1 can be detected after overnight culture in both supernatant and cell extracts. The use of F(ab')2 for capture completely eliminated binding of Staphylococcus aureus. No cross-reactivity was observed with other human herpes viruses. When evaluated with 245 random 'left-overs' of genital swab specimens in transport medium the test showed a sensitivity and specificity of 77.2 and 97.8%, respectively, with respect to virus isolation in culture. In a preliminary study on 16 direct ELISA swab-specimens extracted in 0.5 ml ELISA sample buffer both sensitivity and specificity were 100% with respect to culture. In both clinical series there was a proportional relationship between the ELISA value and the estimated amount of infectious virus in the specimen.

Immunofluorescence for detection of antibodies against human cytomegalovirus-induced membrane antigens

This paper describes an improved method for the in vitro detection of antibodies specifically directed against human cytomegalovirus (CMV)-induced membrane antigens present on the surface of CMV-infected fibroblasts (CMV-MA). Viable cells were found to be essential for specific visualization of CMV-MA staining. The addition of divalent cations (2.6 mM Ca2+ and 2.2 mM Mg2+) and glucose (180 mM) to the incubation and washing buffers improved the viability and morphology of the cells and increased the cell yield at the end of the assay. Clustering of antigen-antibody complexes on the surface of viable CMV-infected cells was prevented by low-temperature incubation (0 to 4 degrees C) rather than by the addition of agents which act on the metabolism of the cell. No interaction with the CMV-induced Fc receptor was observed at 0 degrees C with either human sera or murine monoclonal antibodies. The specificity of the CMV-MA reaction was confirmed by using monoclonal antibodies to CMV nuclear, cytoplasmic, and membrane-associated antigens. Furthermore, a microplate modification of the membrane fluorescence test is described which is suitable for multisample screening purposes. This method can be applied to the determination of anti-CMV-MA antibody titers in human sera and to the screening of hybridoma supernatants for the presence of antibodies with specificity for CMV-MA.