Abstract
Resident cells in the skin serve as the first innate line of defense against insect-borne pathogens, but the role of these cell types in promoting or limiting arbovirus replication is not completely understood. Here, we have examined the outcome of infection of cultured human keratinocyte cells with La Crosse virus (LACV), using a spontaneously transformed cell line, HaCaT. In single cycle infections, keratinocyte HaCaT cells supported rapid and high level LACV replication, resulting in high virus yields and extensive caspase-dependent cell death. By contrast, multi-cycle LACV replication in HaCaT cells was restricted by an antiviral response elicited by the production of both IFN-β and IFN-λ. During low multiplicity LACV infections, HaCaT cell death was seen in non-infected bystander cells. Media from LACV-infected cells induced caspase-dependent killing of naïve non-infected HaCaT cells, and this bystander cell death was relieved by IFN-β neutralizing antibodies or by an inhibitor of JAK-STAT signaling. Naïve HaCaT cells showed dose-dependent killing by treatment with exogenous IFN-β but not IFN-λ. Our data suggest a model whereby keratinocytes produce IFNs which limit virus spread through both antiviral signaling and by induction of bystander cell death of potential new target cells for infection.
Highlights
The skin serves as the first line of defense against infection by insect-borne pathogens such as arboviruses, both as a physical barrier and as a source of antiviral responses which have the potential to limit dissemination [1]
To determine if La Crosse virus (LACV) can productively infect human keratinocyte cells, the HaCaT cell line was infected with LACV at a multiplicity of infection (MOI) of 5 plaque forming units (PFU)/cell
HaCaT cells were infected at a high MOI and viral protein expression was measured by Western blot analysis of LACV nucleocapsid protein (N) accumulation
Summary
The skin serves as the first line of defense against infection by insect-borne pathogens such as arboviruses, both as a physical barrier and as a source of antiviral responses which have the potential to limit dissemination [1]. The capacity of skin resident cells to support arbovirus replication or, alternatively, to limit virus spread could be an important determinant of pathogenesis. We have examined the host cell and antiviral interactions of La Crosse virus (LACV), a prototype negative strand RNA arbovirus with human keratinocytes in vitro. LACV infection results in a mild febrile illness, in a small subset of pediatric cases, LACV infection leads to meningoencephalitis, seizures, and paralysis [2,3]. La Crosse virus is the leading cause of pediatric arboviral encephalitis in the United States [4,5,6]. The actual number of LACV infection cases is estimated to be much higher than reported, since infection numbers are hard to calculate due to underreporting of non-neurological cases that lack distinct symptoms [7,8]
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