| Primary Identifier | IPR035347 | Type | Family |
| Short Name | Putative_chemo_U83 |
| description | Human herpesvirus 6A (HHV-6A) and HHV-6B are classified as roseoloviruses and are highly prevalent in the human population. Roseolovirus reactivation in an immunocompromised host can cause severe pathologies []. HHV6 A/B encode two putative chemokine receptors and a chemokine-like protein. The HHV6 U83 gene encodes a CC chemokine, which functions as a highly selective and efficacious agonist for the human CCR2 receptor, both in respect of signal transduction and the ability to induce chemotaxis. Homologues of the U83 gene products are found in Human cytomegalovirus encoded chemokines vCXC1 and vCXC2.HHV-6 U83, also known as vCCL4, contains a region with the CC/CX3C chemokine motif and a glycosaminoglycan (GAG)-binding epitope, BBXB (B being a basic residue), found right before the third Cys residue, which very likely forms a disulfide bridge back to the first Cys of the protein []. This gene is the only HHV-6A/B divergent gene that is specific for these viruses. The U83 chemokine gene is distinct between HHV-6A and HHV-6B strains, encoding up to 13 amino acid differences. The HHV-6A (U83A) and HHV-6B (U83B) chemokines have distinct specificities which determine chemoattraction or diversion of different leukocyte subsets for infection or immune evasion, thus an early component of cellular tropism as well as mediator of innate immunity. U83 also has a varied gene structure, with N-terminal length variation determining production of the encoded mature secreted chemokine, coupled with control by cell-directed splicing which truncates the chemokine gene early in replication to encode an antagonist. The 'long' active form of U83A has a unique broad specificity for receptors CCR1, CCR4, CCR5, CCR6 and CCR8 present on plasmacytoid and myeloid dendritic and monocyte/macrophage antigen presenting cells, as well as both TH1 and TH2 skin homing lymphocytes and NK cells; it is also amongst the highest affinity ligands for CCR5 and inhibits HIV-1 binding at this coreceptor. U83A can both block and divert human chemokine action while occupying the human chemokine receptors []. |
