IgA directed against early antigen of Epstein-Barr virus is no specific marker for the diagnosis of nasopharyngeal carcinoma

The aim of this study was to evaluate the significance and specificity of IgA directed against Epstein-Barr virus (EBV)-specific early antigens (EA) for the unequivocal diagnosis of nasopharyngeal carcinoma (NPC). Therefore, sera from patients with diseases other than NPC, selected on the basis of elevated antibody titres against EBV antigens, were compared to sera from NPC patients with regard to the presence of IgA directed against EBV viral capsid antigen (VCA-IgA) and IgA directed against EA (EA-IgA). Four hundred forty-seven out of 7,508 non-NPC sera tested showed high titres (>512) of IgG directed against Epstein Barr viral capsid antigen (VCA-IgG) and positive VCA-lgA (?32). Two hundred twenty-seven of these sera were compared to 51 VCA-IgA-positive sera from NPC patients regarding the titre of EA-lgA. 60.7% of VCA-lgA-positive NPC sera showed positive EA-lgA, however 33% of VCA-IgA-positive non-NPC patients also exhibited EA-lgA. This result demonstrates that EA-lgA is not specific for NPC and does not allow an unequivocal serological diagnosis of NPC in individual cases. It seems therefore to be of questionable use for screening programs in NPC low-risk areas. The data do not contradict the usefulness of this marker for monitoring of patients treated for NPC and for screening programmes in high-risk areas. © 1994 Wiley-Liss, Inc.     

Improved sensitivity of detection by avidin-biotin complex (ABC) immunocytochemistry in Epstein-Barr virus serology

Serum antibodies against Epstein-Barr virus (EBV)-determined antigens have traditionally been titrated by the indirect immunofluorescence (IIF) technique. The avidin-biotin complex (ABC) immunocytochemical technique was used to determine the serum levels of IgA against EBV viral capsid antigen (IgA/VCA) and IgA against EBV early antigen (IgA/EA) in sera of 106 nasopharyngeal carcinoma (NPC) patients prior to treatment and 100 normal individuals. The sensitivity of the ABC technique is enhanced by an amplification of the antigen-antibody reaction, which involves the binding of the enzyme-linked ABC to the second biotinylated antibody. There was a good correlation (r = 0.9988) between ABC and IIF-determined IgA/VCA-positive titres, with the ABC technique being more sensitive than IIF in the detection of IgA/VCA in NPC sera: 94% (99/106) and 76% (80/106), respectively. The frequency of IgA/EA reactivity in NPC sera was also markedly increased by immunodetection with the ABC technique as compared with IIF technique: 63% (69/106) and 28% (30/106) respectively. Both the immunocytochemical techniques were equally specific in discriminating between elevated serum titres of IgA/VCA and IgA/EA in NPC sera from normal human sera.     

EBV4型IgA/VCA IgA/EA IgG/EA IgG/ZEBRA抗体在鼻咽癌普查和早期诊断中的应用

目的摸索以疱疹病毒4型（EBV）IgG／ZEBRA为捕捉抗原的间接酶联免疫吸附试验（ELISA）条件,为大量人群普查奠定基础。方法将纯化的ZEBRA抗原用于对鼻咽癌（NPC）患者血清及健康人血清IgG／ZEBRA抗体的ELISA检测。结果检测NPC患者血清288份,其中ELISA实验显示阳性262份,敏感度91％,检测正常人血清96份,其中阳性5份,特异度94．8％。其结果显示NPC组的阳性率与健康对照组的数据之间差异有统计学意义（P〈0．001）。本研究在此基础上对广东惠州5463份和广西桂平2017份血清进行检测,检出早期鼻咽癌患者5例。并将结果与免疫酶法检测IgA／VCA、IgA/EA、IgG／EA比较。结论以EBV早期抗原ZEBRA为捕捉抗原的间接ELISA方法具有较高的特异性和敏感性,可以用于大量人群的NPC早期筛查和早期诊断。     

用基因工程表达的抗原早期诊断鼻咽癌

目的为了建立鼻咽癌（ＮＰＣ）早期诊断方法。方法以基因工程表达的、经纯化的ＥＢ病毒（Ｅｐｓｔｅｉｎ－Ｂａｒｖｉｒｕｓ，ＥＢＶ）早期抗原（ＥＡ）成分ＥＡ－Ｄ和ＥＡ－Ｒ作为诊断抗原，建立了酶联免疫吸附试验（ＥＬＩＳＡ），检查３０例ＮＰＣ病人及４９例正常人血清中的ＥＡ／ＩｇＡ抗体。结果用ＥＬＩＳＡ检测抗体较用细胞涂片免疫酶方法（ＩＥ）敏感。ＥＬＩＳＡ检测ＮＰＣ病人血清中ＥＡ／ｌｇＡ抗体，阳性率为１００％，ＥＡ／ｌｇＡ抗体效价均≥１∶１００。而用ＩＥ法，平行检测３０例ＮＰＣ病人血清中ＥＡ／ｌｇＡ抗体效价，结果６例为阴性（＜１∶１０），抗体阳性率为７０％。ＥＬＩＳＡ明显地提高了ＮＰＣ的检出率。以ｐ１３８（ＥＡ－Ｒ）和ｐ５４（ＥＡ－Ｄ）分别或混合包被，检测对ＥＢＶ特异的ＥＡ－Ｄ和ＥＡ－Ｒ的抗体。结论表明在ＮＰＣ病人血清中存在对ＥＡ两种抗原的抗体，对ＥＡ－Ｄ的抗体滴度高于对ＥＡ－Ｒ的抗体。因此，以两种抗原混合包被作为诊断抗原建立的ＥＬＩＳＡ方法，为ＮＰＣ的早期诊断提供更敏感、特异和简便的手段。     

Use of bacterially expressed EBNA-1 protein cloned from a nasopharyngeal carcinoma (NPC) biopsy as a screening test for NPC patients

EBV serological tests have been used for many years as accessory diagnostic predictors of nasopharyngeal carcinoma (NPC). To increase the sensitivity and specificity of the NPC detection rate, a novel enzyme-linked immunosorbent assay (ELISA) was established using a bacterially-expressed GST-EBNA-1 protein, containing the EBNA-1 sequence cloned from an NPC patient. Serum samples were collected from age- and gender-matched patients with NPC, community control subjects and hospital control patients and tested using this ELISA. The positivity rates were 78.7% (247/314) in NPC, 11.5% (28/244) in hospital controls and 3.8% (10/263) in the community control group. These serum samples were also tested for IgA anti-VCA antibodies and their ability to neutralize EBV DNase and the sensitivities of the anti-VCA antibody and DNase-neutralization tests also were analyzed. The optimum combination is VCA plus EBNA-1, which can identify 92.5% (287/310) of NPC patients, and shows a specificity of 92.7% (242/261) for normal individuals.     

Purified hexameric Epstein-Barr virus-encoded BARF1 protein for measuring anti-BARF1 antibody responses in nasopharyngeal carcinoma patients

WHO type III nasopharyngeal carcinoma (NPC) is highly prevalent in Indonesia and 100% associated with Epstein-Barr virus (EBV). NPC tumor cells express viral proteins, including BARF1, which is secreted and is considered to have oncogenic and immune-modulating properties. Recently, we found conserved mutations in the BARF1 gene in NPC isolates. This study describes the expression and purification of NPC-derived BARF1 and analyzes humoral immune responses against prototype BARF1 (B95-8) and purified native hexameric BARF1 in sera of Indonesian NPC patients (n = 155) compared to healthy EBV-positive (n = 56) and EBV-negative (n = 16) individuals. BARF1 (B95-8) expressed in Escherichia coli and baculovirus, as well as BARF1-derived peptides, did not react with IgG or IgA antibodies in NPC. Purified native hexameric BARF1 protein isolated from culture medium was used in enzyme-linked immunosorbent assay (ELISA) and revealed relatively weak IgG and IgA responses in human sera, although it had strong antibody responses to other EBV proteins. Higher IgG reactivity was found in NPC patients (P = 0.015) than in regional Indonesian controls or EBV-negative individuals (P < 0.001). IgA responses to native BARF1 were marginal. NPC sera with the highest IgG responses to hexameric BARF1 in ELISA showed detectable reactivity with denatured BARF1 by immunoblotting. In conclusion, BARF1 has low immunogenicity for humoral responses and requires native conformation for antibody binding. The presence of antibodies against native BARF1 in the blood of NPC patients provides evidence that the protein is expressed and secreted as a hexameric protein in NPC patients.     

Specific IgA antibody to Epstein-Barr viral capsid antigen: a better marker for screening nasopharyngeal carcinoma than EBV-DNA detection by polymerase chain reaction

Nasopharyngeal carcinoma (NPC) is strongly associated with Epstein-Barr virus (EBV) infection. To assess whether EBV DNA detection by polymerase chain reaction (PCR) or presence of specific serum antibody to viral capsid antigen (VCA) was a better marker for screening NPC, nasopharyngeal tissues and blood samples from 58 NPC patients and 24 non-NPC patients (23 with laryngotracheal stenosis and 1 with chronic tonsillitis) were tested for the presence of EBV DNA and serum specific VCA antibodies, respectively. EBV DNA was detected in 56 (96.5%) of NPC patients and 15 (62.5%) of non-NPC controls, with predominantly EBV type A in both groups. On the other hand, specific VCA IgA antibody was detected in the majority of NPC patients: 52 (89.7%) while only 4 (16.7%) were detected in non-NPC controls. Therefore, specific VCA IgA antibody may serve as a better marker for screening NPC than EBV DNA detected by PCR.     

Antibodies to the second Epstein-Barr virus nuclear antigen in non-Hodgkin lymphomas

Human antibodies against the first and second Epstein-Barr virus encoded nuclear antigens (EBNA-1 and EBNA-2) were analysed by modified ELISA reaction on immunoblots: 5 out of 20 EBNA-1 positive, healthy donor sera reacted with the EBNA-2. Healthy EBV seronegatives contained no antibodies against EBNA-2. The antibodies against this EBNA-2 developed several months after acute EBV infections. Four out of 8 infectious mononucleosis sera failed to react EBNA-2 in the late stage. In the group of EBV seropositive patients with non-Hodgkin lymphoma, 14 out of 18 sera contained EBNA-2 antibodies.     

Immune responses to Epstein-Barr virus lytic proteins in patients with nasopharyngeal carcinoma

Immune responses to three Epstein-Barr virus (EBV) lytic proteins, DNase, thymidine kinase (TK), and BMRF-1 gene products (50/52 kDa diffused early antigen, EA-D complex) were determined in EBV-infected control individuals and patients with nasopharyngeal carcinoma (NPC). Immunofluorescence assays (IFA) were used to detect their humoral immune responses using recombinant EBV lytic proteins expressed in a baculovirus system as antigens. Cell proliferation assays were performed to evaluate their cellular immune responses by monitoring 3H-thymidine incorporation. Seventy patients with NPC and 32 non-cancer controls were analyzed. The results of IFA showed antibody titers to all three EBV lytic proteins to be higher in the patients with NPC especially for the IgA class. Positivity rates of the three IgA antibodies also were higher in the patients with NPC population. Furthermore, the profiles of the IgA antibodies correlated with those to total early antigens (EA) expressed in the early phase and viral capsid antigen (VCA) expressed in the late phase, of EBV replication. The most interesting finding was that antibody titers to the three EBV lytic proteins were associated significantly with metastases of cervical lymph nodes in patients with NPC. As for cellular immunity to the EA-D complex and DNase, weak responses were observed in the cell proliferation assays. Peripheral blood cells from most individuals could not be stimulated to proliferate, except for a few patients with NPC whose antibody titers against the EA-D complex and DNase also were very high.     

Elevated immunoglobulin G antibodies to the proline-rich amino-terminal region of Epstein-Barr virus nuclear antigen-2 in sera from patients with systemic connective tissue diseases and from a subgroup of Sjögren's syndrome patients with pulmonary involvements

Associations of Epstein-Barr virus (EBV) and autoimmune diseases have been hypothesized. We have analysed IgG antibodies to EBV nuclear antigen (EBNA)-2 in sera from Japanese patients with autoimmune systemic connective tissue diseases (CTD), exemplified by systemic lupus erythematosus (SLE), primary Sjogren's syndrome (SS), rheumatoid arthritis (RA), systemic sclerosis (SSc) and secondary SS (classical CTDs complicated with SS). An enzyme-linked immunosorbent assay (ELISA) which uses glutathione-S-transferase polypeptides fused to EBV nuclear antigen (EBNA)-2 and EBNA-1 was developed. Ratios of IgG antibody reactivity to whole IgG concentrations of sera were calculated to normalize EBNA-2 and EBNA-1 antibody levels to the hypergammaglobulinaemia that occurs in CTD. The ELISA optical density OD(450) readings of IgG antibodies to both the amino-terminal aa 1-116 of EBNA-2 and carboxyl-terminal aa 451-641 of EBNA-1 were elevated significantly in patients with SLE, primary SS, RA, SSc and secondary SS when compared to EBNA-1. The OD readings were divided by serum IgG concentrations to normalize for the hypergammaglobulinaemia. The specific levels of IgG antibodies to the amino-terminal region of EBNA-2 were elevated in patients with SLE, primary SS or RA, as well as those with secondary SS complicated with SLE or RA. The EBNA-2 amino-terminal region contains a polyproline tract and a proline-rich sequence and has considerable amino acid sequence homology with many cellular proline-rich proteins. High ratios of EBNA-2 aa 1-116 to EBNA-1 aa 451-641 IgG antibody levels which probably suggest reactivation of EBV latent infection were associated significantly with pulmonary involvement in SS patients. These results are consistent with the hypothesis that the sequence similarity between the amino-terminal region of EBNA-2 and proline-rich cellular proteins is associated with pathogenesis in a subpopulation of CTD patients, possibly by the molecular mimicry-epitope shift mechanism.     

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.     

Detection of IgA antibody to EBV membrane antigen using Staphylococcus aureus preabsorbed sera is closely associated with nasopharyngeal carcinoma

The presence of IgA antibody to membrane antigen (MA) of Epstein-Barr virus (EBV) was tested in sera from 48 nasopharyngeal carcinoma (NPC) patients, 40 patients with tumors other than NPC and 46 normal individuals. The sera were preabsorbed with Staphylococcus aureus (SPA) (strain no. 1800) prior to their use in the indirect immunofluorescence test. One hundred percent of the NPC patients had the IgA/MA antibody with a GMT of 1:141. In patients with tumors other than NPC or normal individuals, IgA/MA antibodies were not detectable. The IgA/MA antibodies have been demonstrated in 6 NPC patients lacking detectable antibody levels in the indirect immunofluorescence test using nonabsorbed sera. Our data indicate that preabsorbtion of sera with SPA renders the diagnostic test significantly more sensitive for the detection of the nasopharyngeal carcinoma and can be used for trials on the prognosis of patients.     

Detection of IgA antibodies to Epstein-Barr virus-associated antigens by ELISA

The detection of IgA antibodies to the Epstein-Barr virus (EBV)-associated viral capsid antigen (VCA) and early antigens (EA) is of diagnostic and prognostic importance for patients with nasopharyngeal carcinoma (NPC). An ELISA for the determination of serum IgG antibodies to these antigens has been developed which uses the double antibody method. 136 sera obtained from healthy donors and patients with non-EBV related tumors and lymphomas were tested by ELISA; only 3 sera, from patients with chronic lymphatic leukemia, hairy cell leukemia and Burkitt-like lymphoma, contained antibodies of IgA class to VCA and EA. Ninety-five sera from patients suspected of having NPC were tested. IgA anti-VCA was found in 28 sera (29.5%), 12 of which also contained IgA anti-EA. The assays described are suitable for diagnosis and follow-up of patients with EBV-associated nasopharyngeal carcinoma. Furthermore, isolated EA components may be tested for their reactivity with IgA antibodies, as was shown for the 60 kDa polypeptide associated with the EA complex.     

Epstein-Barr virus nuclear antigen 1 linear epitopes that are reactive with immunoglobulin A (IgA) or IgG in sera from nasopharyngeal carcinoma patients or from healthy donors.

The entire amino acid sequence of the unique region of the EBNA 1 protein was synthesized as a set of 41 20-residue peptides with an overlap of 10 amino acids. The peptides were tested in the enzyme-linked immunosorbent assay for reactivity with immunoglobulin A (IgA) and IgG in sera from 50 patients with nasopharyngeal carcinoma (NPC) as compared with 36 serum samples from healthy Epstein-Barr virus (EBV)-seropositive donors and 5 serum samples from EBV-negative donors. The most immunoreactive peptide for both IgA and IgG binding was localized to the glycine-alanine repeat domain of the antigen. In the unique regions, 16 immunoreactive peptides were found. Of these, four were reactive with IgG but not IgA and three peptides were reactive with IgA but not IgG in NPC sera. In addition, several IgA and IgG epitopes on the carboxy-terminal region were specifically reactive with NPC sera, but unreactive with sera from healthy EBV-positive donors. The results suggest that EBV serology specific for individual epitopes may provide additional useful information not available by conventional serology with whole antigens or the EBNA complex.     

Epstein-Barr病毒壳抗原gp125的纯化和应用

目的研制ｅｐｓｔｅｉｎ－Ｂａｒ（ＥＢ）病毒诊断试剂。方法将重组痘苗病毒表达的Ｅｐｓｔｅｉｎ－Ｂａｒ病毒（ＥＢＶ）壳抗原（ＶＣＡ）主要多肽ｇｐ１２５纯化，作为诊断抗原建立了酶联免疫吸附试验（ＥＬＩＳＡ），检测了４８份鼻咽癌（ＮＰＣ）病人血清及１０份正常人血清中的ＶＣＡ／ＩｇＡ抗体。结果该方法与免疫荧光（ＩＦ）检测结果一致，但ＥＬＩＳＡ的平均几何滴度（ＧＭＴ）是ＩＦ的１２倍。结论以纯化的ＥＢ病毒壳抗原主要多肽ｇｐ１２５作为诊断抗原建立的检测方法，更适合于ＥＢＶ相关疾病的血清学诊断和血清流行病学调查。     

Assessment of rapid ELISA test for detection of Epstein-Barr virus infection.

A rapid test for the detection of IgM and IgG Epstein-Barr nuclear antigen (EBNA-1) has been extensively marketed. If IgM to Epstein-Barr viral capsid antigen (EBV VCA) is taken as evidence of current EBV infection, one observer detected 17 of 38 such samples and the other 22 of 38 as acute. The positive predictive value of the test was 63%, and the greatest difficulty was posed by the detection of IgM EBV VCA positive, heterophile antibody negative samples. Significant false positive results were obtained in sera with evidence of current Toxoplasma gondii, cytomegalovirus, and adenovirus infection. Rheumatoid factor was not a problem. Modification of the test protocol improved its performance: the positive predictive value rose to 87% and the negative predictive value to 81%. Although our modifications did not increase the speed of the test, there was reliable information on the EBNA-1 state. The test is best used as an adjunct to other EBV serology, and laboratories should be aware of the limitations of the rapid test.     

Antibody to Epstein-Barr virus-specific DNase as a marker for field survey of patients with nasopharyngeal carcinoma in Taiwan

A serological survey using antibody to Epstein-Barr virus (EBV)-specific DNase activity as a marker for the identification of patients with nasopharyngeal carcinoma (NPC) has been carried out on healthy subjects who visited Government Employees' Clinic Center (GECC) for routine health examination and on individuals residing in NPC high-risk areas (HRA) in Taiwan. During a 3-year prospective study, 22,596 and 9,869 sera were collected from the GECC and HRA groups, respectively. Taking neutralization of 2 or more units of EBV DNase activity as a positive response, the positivity rates in the GECC and HRA groups were 5.4% and 11.92%, respectively. Among the antibody-positive individuals, three cases of NPC were found in the GECC group (detection rate 0.63%) and 11 in the HRA group (detection rate 1.32%). A further patient at stage III of the disease was found in the first year of following up of 1,005 antibody-positive individuals. Among the 12 NPC patients in the HRA, five were newly diagnosed as having stage II (three patients) and stage III (two patients) NPC. These results support the hypothesis that antibody against EBV-specific DNase activity may be a useful marker for detection of patients with NPC, and they imply that individuals having high levels of antibody to EBV DNase activity may have an increased risk of development of NPC.     

Single-assay combination of Epstein-Barr Virus (EBV) EBNA1- and viral capsid antigen-p18-derived synthetic peptides for measuring anti-EBV immunoglobulin G (IgG) and IgA antibody levels in sera from nasopharyngeal carcinoma patients: options for field screening

Assessment of immunoglobulin A (IgA) antibody responses to various Epstein-Barr virus (EBV) antigen complexes, usually involving multiple serological assays, is important for the early diagnosis of nasopharyngeal carcinoma (NPC). Through combination of two synthetic peptides representing immunodominant epitopes of EBNA1 and viral capsid antigen (VCA)-p18 we developed a one-step sandwich enzyme-linked immunosorbent assay (ELISA) for the specific detection of EBV reactive IgG and IgA antibodies in NPC patients (EBV IgG/IgA ELISA). Sera were obtained from healthy donors (n = 367), non-NPC head and neck cancer patients (n = 43), and biopsy-proven NPC patients (n = 296) of Indonesian and Chinese origin. Higher values of optical density at 450 nm for EBV IgG were observed in NPC patients compared to the healthy EBV carriers, but the large overlap limits its use for NPC diagnosis. Using either EBNA1 or VCA-p18 peptides alone IgA ELISA correctly identified 88.5% and 79.8% of Indonesian NPC patients, with specificities of 80.1% and 70.9%, whereas combined single-well coating with both peptides yielded sensitivity and specificity values of 90.1 and 85.4%, respectively. The positive and negative predictive values (PPV and NPV, respectively) for the combined EBNA1 plus VCA EBV IgA ELISA were 78.7% and 93.9%, respectively. In the Indonesia panel, the level of EBV IgA reactivity was not associated with NPC tumor size, lymph node involvement, and metastasis stage, sex, and age group. In the China panel the sensitivity/specificity values were 86.2/92.0% (EBNA1 IgA) and 84.1/90.3% (VCA-p18 IgA) for single-peptide assays and 95.1/90.6% for the combined VCA plus EBNA1 IgA ELISA, with a PPV and an NPV for the combined EBV IgA ELISA of 95.6 and 89.3%, respectively. Virtually all NPC patients had abnormal anti-EBV IgG diversity patterns as determined by immunoblot analysis. On the other hand, healthy EBV carriers with positive EBV IgA ELISA result showed normal IgG diversity patterns. By using EBV IgG immunoblot diversity as confirmation assay for EBV IgA ELISA-positive samples, the sensitivity and specificity for NPC diagnosis increased to 98% and 99.2%, respectively, in the Indonesian NPC samples. The use of these combined methods for seroepidemiological screening studies is proposed.     

Significance of specific Epstein-Barr virus IgA and elevated IgG antibodies to viral capsid antigens in nasopharyngeal carcinoma patients

The feasibility of using elevated Epstein-Barr virus (EBV) specific-IgG antiviral capsid antigen (VCA) and IgA anti-VCA antibody levels as an aid in diagnosis of nasopharyngeal carcinoma (NPC) was analyzed by determination of serum antibody titers to EBV in 54 NPC patients, 114 healthy blood donors, and 40 family members by the immunoperoxidase assay (IPA). No significant difference was found in the prevalence rate of EBV IgG anti-VCA antibodies (titer greater than or equal to 20) between the patient group and the control and family groups (100% vs 92% and 90%, respectively). The prevalence rate of elevated EBV IgG anti-VCA titers (greater than or equal to 80, greater than or equal to 160, greater than or equal to 320, greater than or equal to 640) was significantly higher in the NPC patients than in controls. For example, at an IgG titer of greater than or equal to 320, the prevalence rate was 82% in the NPC patient group and 1.7% in the controls (P less than 0.0001). The prevalence of EBV IgA anti-VCA antibodies (greater than or equal to 10) was significantly higher in the NPC patients than in control and family groups (82% vs 6.1% and 0%, respectively). The prevalence rate for elevated EBV IgA anti-VCA (greater than or equal to 20) was found to be significantly higher (P less than 0.0001) in NPC patients than in the control group (70% vs. 1.7%). A significantly high proportion (P = 0.0004) of NPC patients who had serum EBV IgA anti-VCA titers of less than 20 had elevated IgG titers to VCA greater than or equal to 320 (21% vs 1.7% among controls). It appears that testing for IgG antibodies at a serum dilution of 1:320 and for IgA antibodies at a dilution of 1:20 by the IPA technique comprises the best combination for the differentiation between NPC patients and health controls (91% vs 3.4%), and it is suggested that these be used as screening markers for NPC patients.     

Evaluation of the Architect Epstein-Barr Virus (EBV) Viral Capsid Antigen (VCA) IgG,VCA IgM,and EBV Nuclear Antigen 1 IgG Chemiluminescent Immunoassays for Detection of EBV Antibodies and Categorization of EBV Infection Status Using Immunofluorescence Assays as the Reference Method

Commercial immunoassays for detecting IgG and IgM antibodies against Epstein-Barr virus (EBV), viral capsid antigens (VCA), and IgGs toward EBV nuclear antigen-1 (EBNA-1) are routinely used in combination to categorize EBV infection status. In this study, we evaluated the performances of the Architect EBV VCA IgG, VCA IgM, and EBNA-1 IgG chemiluminescent microparticle assays (CMIAs) in EBV serological analyses using indirect immunofluorescence assays and anticomplement immunofluorescence assays as the reference methods for VCA IgG, VCA IgM, and EBNA-1 IgG antibody detection, respectively. A total of 365 serum samples representing different EBV serological profiles were included in this study. The κ values (concordances between the results) obtained in the Architect CMIA and those in the reference assays were 0.905 (P < 0.0001) for VCA IgM, 0.889 (P < 0.0001) for VCA IgG, and 0.961 (P < 0.0001) for EBNA-1 IgG. The sensitivities and specificities were, respectively, 91.08% and 99.48% for VCA IgM, 99.23% and 86.27% for VCA IgG, and 96.77% and 99.16% for EBNA-1 IgG. The sensitivities and specificities of the Architect CMIA panel were, respectively, 99.15% and 98.6% for diagnosing a primary infection, 97.62% and 93.39% for diagnosing a past EBV infection, and 92.42% and 97.82% for diagnosing the absence of an EBV infection. In summary, we demonstrated that the Architect EBV antibody panel performs very well for EBV antibody detection and correctly categorizes clinically relevant EBV infection states.