Antigenic variation in alkaline deoxyribonuclease induced by three different strains of Epstein-Barr virus

A Distinct Anti-EBV DNase Profile in Patients with Undifferentiated Nasopharyngeal Carcinoma Compared to Classical Antigens

Nasopharyngeal cancer (NPC) is a prevalent type of cancer that often takes the form of undifferentiated carcinoma in the Maghreb region. It affects people of all ages. NPC diagnosis, mainly based on detecting Epstein-Barr virus (EBV), has not been well evaluated in North Africa. We compared the classical EBV serological tests using indirect immunofluorescence to the detection of EBV DNase antibodies by immunoblot in Algerian NPC patients. Significant variations were observed among different age groups of patients regarding the presence of VCA-IgA antibodies (0-14 and ≥30 years old, p < 0.0001; 15-19 and ≥30 years old, p < 0.01) and EA-IgA (0-14 and ≥30 years old, p < 0.01; 15-29 and ≥30 years old, p < 0.05). Differences were also noted in the titers of IgA anti-VCA and anti-EA antibodies across the three age groups. Some patients under the age of 30 with detectable IgG anti-VCA antibodies had undetectable IgA anti-VCA antibodies. These patients had a strong anti-DNase IgA response. However, older individuals had a higher level of anti-DNase IgG. Before treatment, children had strong DNase reactivity as indicated by specific IgA antibodies. Young adults had high IgA anti-DNase response, but the elderly (90.9%) had a lower response for these antibodies. Following therapy, the children retained high levels of IgA anti-DNase antibodies, and 66% of the young adults demonstrated robust antibody reactivity against DNase. In contrast, IgG responses to anti-DNase were low in children. This study demonstrated the utility of anti-DNase responses in the diagnosis and prognosis of NPC.

Demonstration of the human herpesvirus 6-induced DNA polymerase and DNase

Infection of HSB-2 cells with human herpesvirus 6 (HHV6) results in an approximately 51-fold increase in the level of DNA polymerase activity and a 4.44-fold increase in the level of DNase activity when compared to mock-infected cells. There was no increase in thymidine kinase, uracil-DNA glycosylase, or deoxyuridine triphosphate nucleotidohydrolase activities in the infected cells. The HHV6-induced DNase and DNA polymerase activities could be distinguished from their normal cellular counterparts on the basis of immunological specificities and in the case of DNA polymerase based upon differences in electrophoretic migration. Serological studies also demonstrated reactivity of the antisera not only for HHV6 but also for Epstein-Barr virus.

The characterization of the EBV alkaline deoxyribonuclease cloned and expressed in E. coli

Studies of nucleic acid homology suggest the BGLF5 open reading frame of Epstein-Barr virus (EBV) encodes an alkaline deoxyribonuclease (DNase) sharing some homology with that of herpes simplex virus. We report here the expression of the BGLF5 open reading frame in E. coli and the expression of high levels of a novel alkaline DNase activity in induced cells. This alkaline DNase has been purified to apparent homogeneity as a single protein species. This is the first report of the expression of a herpesvirus coded DNase in a prokaryotic system and of the purification of the EBV DNase to demonstrable purity. It has the biochemical characteristics of a typical herpesvirus alkaline exonuclease showing a high pH optimum, an absolute requirement for Mg2+ for activity and sensitivity to high salt concentrations and polyamines. The enzyme activity was neutralized by sera from patients with nasopharyngeal carcinoma and was reactive with these sera in Western blot analysis. Thus the prokaryotic expression system described here provides an economical and efficient source of the EBV DNase for biochemical and seroepidemiological analysis.