Purification of a polypeptide complex (p52) belonging to the D-subspecificites of Epstein-Barr virus-induced early antigens

Native early antigen of Epstein-Barr virus, a promising antigen for diagnosis of nasopharyngeal carcinoma

The Epstein-Barr virus (EBV) early antigen (EA) complex consists of multiple proteins with relevance for diagnosis of acute, chronic and malignant EBV related diseases, including nasopharyngeal carcinoma (NPC). In a recent study, it was found that the molecular diversity of EBV-specific IgG and IgA antibody responses in NPC patients and demonstrated that these reflect independent B-cell triggering leading to distinct EBV antigen-recognition profiles. The fine-specificity of NPC-related IgG and IgA responses was explored further against defined recombinant and synthetic EBV-EA antigens using immunofluorescence, immunoblot and ELISA techniques and determined their diagnostic value in a large panel of sera from NPC (n = 154), non-NPC tumor patients (n = 133), acute mononucleosis patients (n = 70) and healthy EBV carriers (n = 259). Individual recombinant EBV-EA markers yielded sensitivity/specificity values not exceeding 86%, whereas selected EA-specific peptide epitopes were rather poorly recognized by IgG and IgA antibodies in NPC sera. Surprisingly, we found that a "low salt" native EA-protein extract reproducibly prepared from purified nuclei of EA-induced HH514 cells, and containing characteristic EA(D)-polypeptides, such as p47-54 (BMRF1), p138 (BALF2), p55-DNAse (BGLF5), and p65-TK (BXLF1), but without viral capsid (VCA) or nuclear antigen (EBNA) reactivity, gave highest sensitivity (90.4%) and specificity (95.5%) values for NPC diagnosis in both IgG and IgA ELISA. The data support further the notion that EBV-EA reactive IgG and IgA antibodies in NPC patients are directed against distinct conformational and-in part-linear epitopes on EBV-specific proteins, barely recognized in other EBV-related syndromes. The use of a defined native EBV EA-specific antigen opens the way to further improve serological diagnosis of NPC.

Antibody responses against polypeptide components of Epstein-Barr virus-induced early diffuse antigen in patients with connective tissue diseases

The specific humoral response against polypeptide components of Epstein-Barr virus (EBV), the induced early diffuse antigen (EA-D), in patients with connective tissue diseases, including systemic lupus erythematosus (SLE) and mixed connective tissue disease (MCTD), was investigated by using the immunoblotting technique. The EA(D)-positive sera from patients with infectious mononucleosis (IM), nasopharyngeal carcinoma (NPC), immunocompromised patients (renal transplant recipients and patients with AIDS) as well as the EA(D)-negative sera from patients with Burkitt's lymphoma and from clinically healthy subjects served as controls. Seven major antigenic polypeptides with molecular weights of 33 kDa, 35 kDa, 52 kDa, 54 kDa, 56 kDa, 58 kDa, and 134 kDa were detected reproducibly by the EA(D)-positive reference sera and, in particular, by each of the NPC sera tested. The EA(D)-positive sera from the other groups showed various combinations of detection patterns and few samples reacted with all the major EA(D) polypeptides. Seventy-three percent of sera from SLE and 47% of sera from MCTD were found to react with EA(D). Sixty-one percent of sera from SLE vs. 5% from MCTD detected all the EA(D) polypeptides. These results could either reflect perturbations of the immune response linked to the autoimmune disease or suggest a possible pathogenic role of EBV.

Specific Epstein-Barr virus serological response in patients with nasopharyngeal carcinoma detected by immunoblotting

The specific humoral immune response against Epstein-Barr virus (EBV) antigens in patients with nasopharyngeal carcinoma (NPC) was compared to that of patients with infectious mononucleosis (IM) and other EBV-seropositive subjects using immunoblotting technique. Almost all sera from EBV serologically associated NPC reacted reproducibly with a major group of polypeptides (four to six) of early antigen (EA) complex with molecular weights ranging from 50 kD to 58 kD, and with some additional polypeptides. Sera from IM-patients reproducibly recognized only one polypeptide of 50 kD belonging to the major group of polypeptides of EA-complex. Sera from patients with other types of head and neck cancer and relatively high levels of IgG antibody against viral capsid antigen (VCA) and EA did not react reproducibly with any of the EBV-associated proteins.

Serum antibodies to a normal cellular protein (P-65) in patients with Hodgkin's disease

Samples from the L-428 Hodgkin's cell line and from several other lymphoma cell lines were lysed and the soluble proteins were subjected to one- or two-dimensional gel electrophoresis. The separated proteins were transferred to nitrocellulose by the Western Blot technique; antibody reactivity was detected by an immunoperoxidase reaction. Of 152 sera from patients with Hodgkin's disease (HD) 26 (17%) reacted with protein P-65 whereas in the control group, consisting of 35 healthy persons and 20 patients with other malignant diseases only 1 serum was reactive. Thus, the difference between the two groups was highly significant (P less than 0.01). These antibodies were most common in stage III HD. Splenectomy had no effect on the incidence of these antibodies, and there seemed to be no correlation with B-symptoms or with the histological subtype.

Antigenically important proteins of Aujeszky's disease (pseudorabies) virus identified by immunoblotting

Immunoblotting was used to identify those Aujeszky's disease virus proteins which elicited major antibody responses in naturally and experimentally infected pigs. Although some proteins comprising purified virus preparations reacted nonspecifically, proteins with mol. wts. of 120 K, 90 K, 71 K and 60 K were antigenically important. These corresponded in size to the virus glycoproteins identified by 3H-glucosamine labelling. Glycoproteins isolated by affinity chromatography from infected PK 15 cells solubilised by Triton X-100 (Triton-soluble glycoproteins) contained antigenic components similar in size to virus glycoproteins and produced minimal non-specific immunoblotting reactions. Antibody responses to the 120 K and 71 K proteins usually occurred together and were more pronounced than responses to other proteins especially at early times postinfection.

Characterization of the Epstein-Barr virus-induced early polypeptide complex p50/58 EA-D using rabbit antisera, a monoclonal antibody, and human antibodies

A polypeptide complex (p52) belonging to the D-subspecificity of the EBV-induced early antigens (EA-D) was purified from chemically induced P3HR-1 cells. Rabbit antisera raised against the isolated polypeptides reacted with components of EA-D as could be shown by indirect immunofluorescence and immunoperoxidase staining of IdU-induced EA positive Raji cells, ELISA, and immunoblotting. In one-dimensional immunoblots the rabbit antisera detected a predominant polypeptide complex of 52 kDa. Two-dimensional immunoblots prepared with proteins from IdU-induced Raji cells showed that the rabbit sera detect three series of polypeptides of 52 kDa (pl 8.5-6.2), 55-58 kDa (pl 6.2-4.5), and 48-50 kDa (pl 6.0-4.5). These three groups of polypeptides could also be identified by 50 high titered anti-EA-D positive human sera and a specific monoclonal antibody (R3) as being the main components of EA-D in Raji and B95-8 cells. All polypeptides of the p50/58 complex showed DNA binding properties either by themselves or by an interaction with other proteins. When TPA or IdU-induced Raji cells were labeled with 2Pi, two phosphorylated polypeptides pp50 and pp58 could be immunoprecipitated with the rabbit sera and a high anti-EA titered human serum. The time course of the synthesis of polypeptides associated with the EA-D complex was studied by 2-D immunoblots: EA polypeptides of 52 kDa appeared as early as 6 hr after the addition of IdU to Raji cells in culture, polypeptides of 55-58 and 48-50 kDa after 18 and 25 hr, respectively. The coordinated appearance of these groups of polypeptides and their similar size and reactivity with human sera and rabbit antisera produced against the isolated p52 as well as with a monoclonal antibody (R3) suggested that most of these polypeptides are derived from post-translational modifications of one or a few initially synthesized polypeptides, possibly p52. Phosphorylation seems to be at least one possibility of post-translational modification.

Increased incidence of IgA antibodies to the Epstein-Barr virus-associated viral capsid antigen and early antigens in patients with chronic lymphocytic leukemia

Antibody titers to Epstein-Barr virus (EBV)-associated early antigens (EA) and the viral capsid antigen (VCA) were determined by ELISA on 263 sera obtained from healthy donors, patients with Hodgkin's disease (HD), non-Hodgkin lymphomas (NHL), infectious mononucleosis (IM), Burkitt's lymphoma (BL), and nasopharyngeal carcinoma (NPC). As expected, most lymphoma patients showed markedly elevated anti-VCA IgG and anti-EA IgG antibody titers. Only one patient in the NHL group (n = 56) consisting of patients with lymphomas other than chronic lymphocytic leukemia (CLL) and hairy-cell leukemia (HCL), and 3 patients with HCL (n = 19) had high antibody titers of the IgA class to VCA and EA. Seventeen out of 48 patients (36%) with CLL had high IgA anti-VCA titers and 10 of these sera (21%) also contained IgA anti-EA. The geometric mean titer (GMT) of IgA anti-VCA was 2,510, the GMT of IgA anti-EA was 780. These antibody titers were about 10 times lower than the corresponding GMT of the NPC patients investigated in this study. The elevated IgG and IgA antibody titers to VCA and EA in CLL and HCL patients seem to reflect an immunodeficiency secondary to the malignant disease leading to reactivation of latent EBV infection. The possibility that at least some of these B-cell lymphomas are associated with EBV cannot be excluded.