Abstract
Human herpesvirus 6B (HHV-6B) is a T-lymphotropic virus and the etiological agent of exanthem subitum. HHV-6B is present in a latent or persistent form after primary infection and is produced in the salivary glands or transmitted to this organ. Infected individuals continue to secrete the virus in their saliva, which is thus considered a source for virus transmission. HHV-6B primarily propagates in T cells because its entry receptor, CD134, is mainly expressed by activated T cells. The virus then spreads to the host’s organs, including the salivary glands, nervous system, and liver. However, CD134 expression is not detected in these organs. Therefore, HHV-6B may be entering cells via a currently unidentified cell surface molecule, but the mechanisms for this have not yet been investigated. In this study, we investigated a CD134-independent virus entry mechanism in the parotid-derived cell line HSY. First, we confirmed viral infection in CD134-membrane unanchored HSY cells. We then determined that nectin cell adhesion molecule 2 (nectin-2) mediated virus entry and that HHV-6B-insensitive T-cells transduced with nectin-2 were transformed into virus-permissive cells. We also found that virus entry was significantly reduced in nectin-2 knockout parotid-derived cells. Furthermore, we showed that HHV-6B glycoprotein B (gB) interacted with the nectin-2 V-set domain. The results suggest that nectin-2 acts as an HHV-6B entry-mediated protein.
Highlights
Human herpesvirus 6 (HHV-6) is classified into two distinct species, HHV-6A and Human herpesvirus 6B (HHV-6B) [1,2,3,4], and human herpesvirus 7 (HHV-7) [5]
The HHV-6B entry receptor has previously been identified as CD134 [7], but the virus has been detected in tissues in which CD134 is not expressed [10,12,13,14]
While single receptors have been identified for the entry of HHV-6A (CD46), HHV-6B (CD134), and HHV-7 (CD4) into T cells, other herpesviruses use multiple receptors that enable entry into diverse cell types [18]. glycoprotein B (gB), gH, gL, gM, and gN are conserved glycoproteins from the family Herpesviridae [55,56]
Summary
Human herpesvirus 6 (HHV-6) is classified into two distinct species, HHV-6A and HHV-6B [1,2,3,4], and human herpesvirus 7 (HHV-7) [5] It belongs to the genus Roseolovirus in the betaherpesvirus subfamily, which is a group of T-lymphotropic herpesviruses and the causal agents of exanthem subitum (ES), known as roseola infantum. The use of CD134 as an entry receptor is consistent with evidence that HHV-6B is a T-lymphotropic virus that propagates in primary activated T cells [9]. This virus was detected in the saliva, salivary glands [2,10,11], and livers of pediatric patients [12,13]. The expression of CD134 was not detected in the salivary glands, liver, or brain samples available from the Human Protein Atlas
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