Molecular basis for Epstein-Barr virus induced pathogenesis and disease

Quantitative PCR for the detection of genomic DNA of Epstein-Barr virus in ocular fluids of patients with uveitis

PURPOSE

To measure the genomic DNA from Epstein-Barr virus (EBV) in ocular fluids and to analyze the clinical relevance of EBV in uveitis.

METHODS

Intraocular fluids (30 aqueous humor and 30 vitreous fluid samples) were taken from 55 patients with uveitis after informed consent was obtained. Samples were assayed for EBV DNA using qualitative multiplex polymerase chain reaction (PCR) and quantitative real-time PCR. Antibodies to EBV were examined using a complement fixation test.

RESULTS

EBV DNA was detected in 17 of 60 samples (28%) and 16 of 55 patients (29%) using multiplex PCR. However, only three of the 17 samples showed significantly high copy numbers of EBV DNA with real-time PCR. EBV DNA was not detected in the serum of all patients. EBV-specific antibodies were positive in the serum of all patients, but not in the vitreous fluid. Vitreous anti-EBV antibodies were positive only in patients displaying genomic DNA of EBV in the vitreous samples.

CONCLUSIONS

EBV DNA was detected by qualitative PCR in ocular fluids of many uveitis patients, but only a small proportion of patients showed high viral loads on quantitative real-time PCR, indicating that replication of the virus takes place only in a few patients.

Links between prolonged exposure to xenobiotics, increased incidence of hepatopathies, immunological disturbances and exacerbation of latent Epstein-Barr virus infections

Disturbances of several humoral and cellular immune parameters are significantly increased in individuals exposed to chemical pollutants. Moreover, exacerbations of the latent Epstein-Barr virus (EBV) infection were more frequently observed in the chemically exposed group than in the control groups. A significant correlation was seen between EBV exacerbations and the increased number of eosinophils, T-lymphocyte rosette formation and the respiratory burst of polymorphonuclear blood cells. Possible links between hepatopathy due to xenobiotics exposition, immunological disturbances and EBV exacerbation are discussed, including a putative role of EBV-induced (autocrine) cytokines.

Absence of a reservoir of Epstein-Barr virus (EBV) in normal tongue epithelium

We examined human tongue epithelium and serum samples at autopsy for evidence of latent Epstein-Barr virus (EBV) infection. Although clinical serology revealed anti-EBV antibodies in most sera indicating past EBV infection, we found no Epstein-Barr nuclear antigen (EBNA)-coding sequences in tongue tissue by polymerase chain reaction (PCR), or Epstein-Barr-encoded RNA (EBER1) by in situ hybridization. Tongue epithelium does not appear to be a natural reservoir for latent EBV in immunocompetent hosts.

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.

The Epstein-Barr virus nuclear protein 1 promoter active in type I latency is autoregulated

The only member of the Epstein-Barr virus family of nuclear proteins (EBNAs) expressed during type I and type II latent infections is EBNA-1. This is in contrast to type III latency, during which all six nuclear proteins are expressed from a common transcription unit. The exclusive expression of EBNA-1 during type I and II latency is mediated through a recently identified promoter, Fp. The objective of this study was to characterize Fp in the Burkitt lymphoma cell background, where it is known to be differentially utilized. Using a short-term transfection assay and reporter gene plasmids containing Fp linked to the human growth hormone, we examined Fp activity in type I and type III latently infected and virus-negative Burkitt lymphoma cells. The data suggested that Fp is predominantly regulated through two distinct elements located between +24 and +270 relative to the transcription start site. One element positively mediates Fp activity, probably at the level of transcription, and acts in a virus-independent manner. The second element contains the EBNA-1 DNA binding domain III and negatively regulates Fp-directed gene expression in trans with EBNA-1 in type III as well as type I latency. Thus, we have identified a third function of EBNA-1, i.e., that of a repressor of gene expression, in addition to its known role in viral DNA replication and its ability to trans-activate gene expression. The overall activity of Fp in type I latently infected Burkitt cells was approximately sixfold lower than in virus-negative Burkitt cells, in which there is no autoregulation, suggesting that there is a fine balance between these two opposing regulatory elements during type I latency.