Complementation of the Function of Glycoprotein H of Human Herpesvirus 6 Variant A by Glycoprotein H of Variant B in the Virus Life Cycle

Abstract

dHuman herpesvirus 6 (HHV-6) is a T-cell-tropic betaherpesvirus. HHV-6 can be classified into two variants, HHV-6 variant A (HHV-6A) and HHV-6B, based on genetic, antigenic, and cell tropisms, although the homology of their entire genomic sequences is nearly 90%. The HHV-6A glycoprotein complex gH/gL/gQ1/gQ2 is a viral ligand that binds to the cellular receptor human CD46. Because gH has 94.3% amino acid identity between the variants, here we examined whether gH from one variant could complement its loss in the other. Recently, we successfully reconstituted HHV-6A from its cloned genome in a bacterial artificial chromosome (BAC) (rHHV-6ABAC). Using this system, we constructed HHV-6ABAC DNA containing the HHV-6B gH (BgH) gene instead of the HHV-6A gH (AgH) gene in Escherichia coli. Recombinant HHV-6ABAC expressing BgH (rHHV-6ABAC-BgH) was successfully reconstituted. In addition, a monoclonal antibody that blocks HHV-6B but not HHV-6A infection neutralized rHHV-6ABAC-BgH but not rHHV-6ABAC. These results indicate that HHV-6B gH can complement the function of HHV-6A gH in the viral infectious cycle.

The putative U94 integrase is dispensable for human herpesvirus 6 (HHV-6) chromosomal integration

“…Cell-free virus stocks were generated by concentrating the supernatant of highly infected JJHan cells and titrated by analysing the genome copies in newly infected cells by qPCR. Multi-step growth kinetics (Oyaizu et al, 2012;Nukui et al, 2015) revealed that the DU94 mutant had a significant growth defect compared to the wt and revertant virus (Fig. 1c), suggesting that the impaired HHV-6A replication is either due to the abrogation of U94 expression or effects on neighbouring genes such as U95 caused by deletion of the U94 sequences.…”

Detailed Study of the Interaction between Human Herpesvirus 6B Glycoprotein Complex and Its Cellular Receptor, Human CD134

“…6B). As mentioned previously, the HHV-6B gH/gL/ gQ1/gQ2 complex did not bind to CD46 (12), even when HHV-6B gQ1 formed a complex with HHV-6A gH, gL, and gQ2 (19) (Fig. 6C).…”

“…Human CD46 was identified as the cell receptor for HHV-6 (8) and binds the HHV-6A gH/gL/gQ1/gQ2 complex (9,10). Interestingly, we found that a similar glycoprotein complex exists in HHV-6B but does not bind to CD46 (11,12), even though it shares a relatively high sequence identity with the glycoprotein in HHV-6A (especially the gH and gL components). Recently, we found that human CD134 is a specific cellular receptor for HHV-6B and binds to the HHV-6B gH/gL/gQ1/gQ2 complex (13).…”

Roseomics: a blank slate

“…These studies have almost exclusively focused on HHV-6A, as it is the only roseolovirus genome that has been cloned into a bacterial artificial chromosome (BAC) (11) and is therefore applicable to genetic manipulation. Examples of reverse genetic approaches in roseoloviruses include defining the role of viral glycoproteins in replication (11), and confirming the role of homologous genes conserved across the herpesvirus family (12). …”