A monoclonal antibody that neutralizes Epstein-Barr virus, human cytomegalovirus, human herpesvirus 6, and bacteriophage T4 DNA polymerases.

Abstract

A monoclonal antibody (mAb) designated 55H3 was produced by using chemically induced Epstein-Barr virus genome-positive B95-8 cells. mAb 55H3, which reacted with an 85-to 80-kDa polypeptide, neutralized Epstein-Barr virus-encoded DNA polymerase activity in crude extracts of chemically induced M-ABA, HR-1, and B95-8 cells, as well as the partially purified Epstein-Barr virus DNA polymerase in a dose-dependent manner. The mAb also neutralized the virusencoded DNA polymerase activity from cells infected with human cytomegalovirus, human herpesvirus 6, and the purified bacteriophage T4 DNA polymerases. However, mAb 55H3 did not neutralize the DNA polymerase activities encoded for by herpes simplex virus types 1 and 2, the reverse transcriptase of avian myeloblastosis virus, or Escherichia coli DNA polymerase 1 (Klenow fragment). These results suggest that mAb 55H3 recognizes an epitope common to some herpesviruses and T4 DNA polymerases and further supports the hypothesis that these organisms are evolutionarily related.Members of the poxviruses, adenoviruses, and herpesviruses encode specific DNA polymerases (1-6). These DNA polymerases are not only required for replication of these viruses, but they can also be used as a target site for development of antiviral agents. While there have been advances in our understanding of the conformation of various DNA polymerases and their interaction with various substrates and with template DNA, little is known about the interaction of viral DNA polymerase with other proteins involved in the DNA replication complex.Epstein-Barr virus (EBV), a human herpesvirus, is the etiological agent of infectious mononucleosis and is associated with African Burkitt lymphoma and nasopharyngeal carcinoma (7-11). EBV is similar to other herpesviruses in that it encodes a DNA polymerase essential for virus replication (12, 13). The EBV-encoded DNA polymerase activity has been purified from several EBV genome-positive cells, and at least four polypeptides with molecular masses of 110, 100, 55, and 49 kDa have been associated with this activity (14,15). Although the 110-kDa polypeptide may be the DNA polymerase (14), studies have demonstrated that the 55-and 49-kDa proteins (15), as well as a 45-kDa stimulatory protein (16), are required for EBV DNA polymerase activity in vitro. Elucidation of these protein interactions is important not only for understanding how EBV replicates but also in determining the role of these polypeptides in diseases caused by EBV.While sera from patients with nasopharyngeal carcinoma contain antibodies that neutralize EBV DNA polymerase, the sera also contain antibodies against the EBV DNA polymerase stimulatory protein (16)(17)(18)(19). Similarly, although a rabbit polyclonal antibody has been developed that can inhibit EBV DNA polymerase activity (20), it is not known whether this polyclonal antibody neutralizes the DNA polymerase activity by binding to the enzyme or due to its binding to one of the associated polypeptides. Thus, further studies on the intera...

Characterization of the DNA polymerase gene of human herpesvirus 6

“…Recently, Tsai et al (58) have isolated a monoclonal antibody that neutralizes the DNA polymerases of EBV, HCMV, HHV-6, and bacteriophage T4, but not the polymerase activity of HSV-1, HSV-2, or Escherichia coli DNA polymerase I Klenow fragment. This would imply that the DNA polymerases of HHV-6, HCMV, and EBV possess a common epitope not present in the polymerases of HSV-1 and HSV-2.…”