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Epstein-Barr viral latent and early antigen serology in nasopharyngeal carcinoma
Abstract
Nasopharyngeal carcinoma (NPC) is cancer of the nasopharynx in humans. It is an insidious and often rapidly fatal disease that is rare worldwide, but is very common among the Chinese from southern China and south-east Asia. It is difficult to detect since, in its early stages, patients are asymptomatic. However, NPC detected in its early stages is highly curable through radiation therapy. Clinically, it can be detected by an experienced medical practitioner using fibreoptic endoscopy, computer-assisted tomography or through serological tests. Serological testing detects the presence of specific antibodies to the Epstein-Barr virus, which is a crucial aetiological factor in the pathogenesis of the disease. Current methods include detection by indirect immunofluorescence assay which is laborious, subjective and requires highly-trained personnel, and enzyme-linked immunosorbent assay (ELISA), which can be easily performed by any hospital laboratory.
The purpose of this project was to characterise the serology to selected latent and early antigens, and assess the diagnostic significance of the presence of such serology in patients with NPC or NPC-associated symptoms, compared to healthy individuals. This data could then be used in developing assays for the early detection of NPC. To this end, a total of four individual viral antigens were developed for use in ELISA. Three were recombinant clones of viral Early Antigens (encoded by BORF2, BaRF1 and BMRF1 opening-reading frames) and one was a peptide epitope of a latent antigen (from the BKRF1 open-reading frame). The recombinant clones were bacterially-expressed as full-length proteins fused to the maltose-binding protein (MBP) from Escherichia coli, purified and subsequently used as antigens in ELISA.
The relative effectiveness of the various ELISA developed in this project were compared and discussed. The results were very significant, with up to 100% diagnostic sensitivity, achieved through the use of a duplexed ELISA utilising a pair of antigens from the Epstein-Barr virus. One antigen, MBP:BaRF1, was a novel recombinant clone of a previously little-studied protein from the Early Antigen-Restricted complex, and the other was the synthetic peptide of a defined epitope from the important latent antigen, EBNA-1. This perfect detection rate among NPC patients was achieved while maintaining a low rate of false positives among healthy individuals. Another recombinant antigen, MBP:BMRF1, from the Early Antigen-Diffuse complex was found to be useful for the differential diagnosis of NPC from among individuals with NPC-associated symptoms or risk factors. Certain groups of individuals with such symptoms or risk factors were also found to have significant serology to viral proteins and the implications of this are discussed.
There was also evidence suggesting that serological testing for NPC could also be used as a gauge of the progress and success of treatment. This was in contrast to the commonly used immunofluorescence assay where this is impractical.
In conclusion, the project was successful and met the objectives set out. The data generated as a result should provide a useful basis for further research and even in the development of commercially-viable assays for the sensitive and early detection of NPC.
The purpose of this project was to characterise the serology to selected latent and early antigens, and assess the diagnostic significance of the presence of such serology in patients with NPC or NPC-associated symptoms, compared to healthy individuals. This data could then be used in developing assays for the early detection of NPC. To this end, a total of four individual viral antigens were developed for use in ELISA. Three were recombinant clones of viral Early Antigens (encoded by BORF2, BaRF1 and BMRF1 opening-reading frames) and one was a peptide epitope of a latent antigen (from the BKRF1 open-reading frame). The recombinant clones were bacterially-expressed as full-length proteins fused to the maltose-binding protein (MBP) from Escherichia coli, purified and subsequently used as antigens in ELISA.
The relative effectiveness of the various ELISA developed in this project were compared and discussed. The results were very significant, with up to 100% diagnostic sensitivity, achieved through the use of a duplexed ELISA utilising a pair of antigens from the Epstein-Barr virus. One antigen, MBP:BaRF1, was a novel recombinant clone of a previously little-studied protein from the Early Antigen-Restricted complex, and the other was the synthetic peptide of a defined epitope from the important latent antigen, EBNA-1. This perfect detection rate among NPC patients was achieved while maintaining a low rate of false positives among healthy individuals. Another recombinant antigen, MBP:BMRF1, from the Early Antigen-Diffuse complex was found to be useful for the differential diagnosis of NPC from among individuals with NPC-associated symptoms or risk factors. Certain groups of individuals with such symptoms or risk factors were also found to have significant serology to viral proteins and the implications of this are discussed.
There was also evidence suggesting that serological testing for NPC could also be used as a gauge of the progress and success of treatment. This was in contrast to the commonly used immunofluorescence assay where this is impractical.
In conclusion, the project was successful and met the objectives set out. The data generated as a result should provide a useful basis for further research and even in the development of commercially-viable assays for the sensitive and early detection of NPC.
Date Issued
1999
Call Number
QR400.2.E68 Tan
Date Submitted
1999