Enzyme-linked immunosorbent assay for antibodies to ZEBRA, an Epstein-Barr trans-activator

Application of circulating plasma/serum EBV DNA in the clinical management of nasopharyngeal carcinoma

Elevated levels of circulating cell-free Epstein-Barr virus (EBV) DNA have been detected in plasma and serum samples from nasopharyngeal cancer (NPC) patients by quantitative real time PCR (qPCR) test. This qPCR test for circulating EBV DNA was found to be useful in the clinical management of NPC patients. For instance, EBV DNA qPCR test has good sensitivity and specificity in the detection of NPC at disease onset. Increase of the viral DNA load was found in NPC patients at late stages of disease. High EBV DNA load at disease onset or detectable viral load post-treatment was associated with poor survival or frequent relapse in NPC patients. Residual EBV DNA load after primary treatment could be a useful indicator to justify adjuvant chemotherapy. The qPCR test might also be applied to define a poor prognostic group in patients at early stage (I/II) for implementing concurrent chemo-radiotherapy (chemo-RT) to improve patients' outcome. The test is also useful to monitor distant metastases or response to radiotherapy, chemo-RT or surgery. Supplementary tests, however, are needed to pick up EBV negative WHO type I NPC and test improvement is needed to increase sensitivity in detecting stage I disease and local recurrence.

Analyses of the prognostic significance of the Epstein-Barr virus transactivator ZEBRA protein and diagnostic value of its two synthetic peptides in nasopharyngeal carcinoma

BACKGROUND

Although numerous serological studies have determined the diagnostic and prognostic values of Epstein-Barr virus (EBV) antibodies in adult patients with nasopharyngeal carcinoma (NPC), little data about the anti-EBV immune response in children with NPC is available.

OBJECTIVES

To examine the diagnostic value of IgG antibodies against BamHI Z Epstein-Barr replication activator (ZEBRA) protein and two related synthetic peptides (Zp125 and Zp130). To compare the prognostic value of IgA antibodies against early antigens (EA) and viral capsid antigen (VCA), and IgG antibodies against ZEBRA protein, of Moroccan children treated for NPC with their prognostic value for young and adult NPC patients.

STUDY DESIGN

Sera were collected from 255 newly diagnosed Moroccan NPC patients and 226 healthy donors. IgA antibody against VCA and EA was measured by immunofluorescence assays. IgG antibody against ZEBRA, Zp125, and Zp130 was measured by ELISA.

RESULTS

No significant difference in the detection of IgG-Zp125 and Zp130 antibodies was observed in children with NPC. IgG-Zp130 were detected less frequently than IgG-Zp125 in young and adult patients, as compared to children. High specificity of IgG-Zp125 and -Zp130 antibodies was found in the three age groups. A decrease in IgG-ZEBRA was observed in patients with NPC in clinical remission, whereas patients with NPC who died or developed metastases maintained or had an increase in these titers.

CONCLUSION

IgG-ZEBRA is a better diagnostic and post-therapeutic prognostic marker in children with NPC, who showed very low titers of IgA -VCA and -EA.

Antibody responses to recombinant Epstein-Barr virus antigens in nasopharyngeal carcinoma patients: complementary test of ZEBRA protein and early antigens p54 and p138

Serological tests based on the antibodies directed against the Epstein-Barr virus early antigen (EA) and viral capsid antigen (VCA), which have been recognized as tumor markers for nasopharyngeal carcinoma (NPC), are routinely used to help in the diagnosis of this malignancy. The detection of these antibodies reveals very low titers, found only in a small proportion of young compared with older NPC patients. This is a problem for the diagnosis of NPC, especially among Maghrebians, among whom young people are also affected, and emphasizes the necessity to search for more reliable markers. The present study reports results of immunoglobulin G (IgG) and IgA responses of NPC patients to recombinant EA antigens p54 (BMRF1) and p138 (BALF2), VCA complex antigens p18 (BFRF3) and p23 (BLRF2), and EBNA antigen p72 (BKRF1). Our results show that IgA-EA-p54 and -p138 (IgA-EA-p54+138) antibodies have a diagnostic value for detection of NPC (70%), compared with IgA-VCA-p18+23 and IgA-EBNA-p72, which have limited diagnostic value, especially in young patients. It is also noteworthy that IgA-EA-p54+138 can detect a high percentage (64%) of NPC cases negative by immunofluorescence. These results, however, clearly show that a single test cannot achieve the objective of detecting all NPC patients, and it seems advisable to combine different tests for the diagnosis of NPC. The combination of IgG-ZEBRA with IgA-EA-p54+138 improved the sensitivity of detection of NPC to 95% in the overall NPC population. The use of IgA-EA-p54+138 in combination with IgG-ZEBRA will facilitate detailed studies on the pattern of antibody response, which may result in the development of useful serological markers to guide the treatment of NPC.

Antibodies to the Epstein-Barr virus transactivator protein (ZEBRA) as a valuable biomarker in young patients with nasopharyngeal carcinoma

Epstein-Barr virus (EBV)-associated nasopharyngeal carcinoma (NPC) generally occurs in adults, especially in high-prevalence populations such as the Chinese and Eskimos. In Maghrebian populations, young patients affected with this malignancy represent 25% of the total NPC cases. In adults with NPC, relatively high titers of IgA antibodies to the EBV viral capsid antigen (VCA) and early antigen (EA) represent important markers. However, nearly 50% of young NPC patients are negative for IgA-anti-VCA and -EA or exhibit very low titers of these antibodies. We report here that 92% of sera from young NPC patients negative for IgA-EA and 89% of those negative for IgA-VCA were positive for IgG antibodies to the EBV transactivator protein (ZEBRA) at very high titers. Our results show that in young patients with NPC these antibodies represent the most reliable marker for diagnosis and prognosis, particularly when compared with conventional NPC markers, i.e., IgA-VCA (58%) and anti-EA (25%). The titers of IgG-ZEBRA antibodies increased along with lymph node involvement only in the young patient group, suggesting a prognostic value of this marker in this patient group.

Study of mother-to-child Epstein-Barr virus transmission by means of nested PCRs

The aim of this study was to investigate the possibility of vertical Epstein-Barr virus (EBV) transmission. We developed two nested-PCR methods for amplifying distinct regions of EBV DNA (BNRF1 and BamHI W) in circulating lymphocytes. Nested PCR was applied to samples obtained from 67 mother-infant pairs within 1 week of birth. We also tested samples from 16 neonates born to human immunodeficiency virus (HIV)-infected mothers to determine whether HIV increases the potential risk of vertical EBV transmission. About half of the 67 women in the first population were positive by nested PCR. Two neonates born to EBV PCR-positive women were also PCR positive. One of the 16 neonates born to HIV-infected women was PCR positive for EBV. These results strongly support the possibility of EBV transmission in utero or during delivery but do not suggest that HIV infection increases this risk. Further studies are required to confirm these findings, to identify the precise mode of vertical EBV transmission, and to determine the outcome for infants who are positive at birth for EBV DNA by nested PCR.

Compact Epstein-Barr virus diagnosis based on a defined antigen mix and specific IgA

An ELISA was evaluated to measure EBV-specific IgM, IgG and IgA using a test plate coated with a controlled mix of EA, VCA and EBNA. Using the IgM version, the multi-reactive surface reduced false-negative findings in cases of infectious mononucleosis (sensitivity 98%), but was confronted with polyclonal IgM responses (specificity 85% to 95% depending on the population). For the IgG version, a national research standard was involved, and in combination with the IgA estimation, a new diagnostic strategy became possible for chronic EBV infections and reactivations. Patients screened by enhanced IgG (> 650 U/ml) were confirmed by an elevated IgA signal (> 0.6 A), with an efficacy of 95%. A raised virus-specific IgA response was not observed in cases of infectious mononucleosis, but was seen for healthy HIV-positive persons. Superior to the traditional antibody puzzle for EBV diagnosis, it will now become possible, using this compact diagnostic concept, to reduce laboratory expenses without loss of reliable results.

A possible prognostic role of immunoglobulin-G antibody against recombinant Epstein-Barr virus BZLF-1 transactivator protein ZEBRA in patients with nasopharyngeal carcinoma

BACKGROUND

Epstein-Barr virus BZLF-1 replication activator (ZEBRA) is involved in the switch from viral latency to a productive cycle. Previous immunofluorescent study has shown that patients with nasopharyngeal carcinoma (NPC) have elevated immunoglobulin-G (IgG) antibody titres against recombinant ZEBRA protein (ZEBRA/IgG).

METHODS

The prognostic role of ZEBRA/IgG was further investigated by enzyme-linked immunosorbent assay (ELISA) in 110 NPC patients under long period of clinical follow-up.

RESULTS

Ninety-seven percent (85 of 88) of the patients with NPC had significantly higher ZEBRA/IgG titres (geometrical mean titre, i.e., GMT = 8397) than normal Chinese individuals (GMT = 233 and P < 0.0001). Based on Kaplan-Meier analysis, the actuarial survival in patients with high ZEBRA/IgG titres (25%) after radiotherapy was significantly lower than that of those with low (76%; P = 0.0008) or intermediate titres (62%; P = 0.0036), although the titres taken before treatment did not bear such a relationship. Subdividing the patients into either individual UICC or Ho's stages, those with late-stage disease (UICC Stage 4 and Ho's Stages 3 and 4) and with high ZEBRA/IgG titres also had poorer prognosis than those with disease of the same stages but who had low titres. Poor prognosis in those with high titres could be associated with a high risk of distant metastasis because consistent titre increase was found in the majority of patients who later developed distant metastasis either in the lung or liver. Only a minimal increase was found in patients with recurrence in the cervical lymph nodes. No consistent increase was observed, however, in patients whose disease was in remission or the majority of those with bone metastasis or local recurrence in the nasopharynx.

CONCLUSION

The postradiotherapy ZEBRA/IgG titre could be a potentially useful marker for differentiating NPC patients with poor prognosis from those at high risk for the development of distant metastasis to the lung or liver.