Given the importance of innate defense mechanisms in the skin, we have examined the interactions of the arbovirus La Crosse virus (LACV) with serum factors that serve as a first line of antiviral defense, and the outcome of LACV infection of human keratinocytes, one of the main cell types present at viral entry. Incubation of LACV derived from insect cells (I-LACV) with normal human serum in vitro did not result in neutralization, but instead stabilized LACV virions and enhanced infectivity. Enhanced infectivity was also seen with heat inactivated serum devoid of complement activity and with serum from a range of animals including mouse, ferret and non-human primates. Depletion of antibodies from serum removed enhancement of I-LACV infectivity and sucrose gradient sedimentation assays showed IgG co-sedimenting with I-LACV particles. Serum-enhancement of LACV infectivity was not seen with virus derived from human cells, suggesting that insect cell-derived LACV is unique in its ability to subvert factors in serum to facilitate the initial infection of animal cells. In modeling initial replication following delivery of insect-derived virus to the skin, we show that I-LACV replication in HaCaT cells was restricted in culture by an antiviral response elicited by both IFN-β and IFN-λ. Media from I-LACV-infected cells induced killing of bystander non-infected HaCaT cells, and this cell death was relieved by blocking IFN-β signaling. Bystander cell killing was not seen with I-LACV infection of a human fibroblast cell line. Our data suggest that keratinocytes produce IFNs which limit virus spread through both antiviral signaling and by induction of cell death of potential new target cells for infection. These results are further evidence that virus and host immune interactions are complex and raises the question on how the combined outcome of these interactions determines the success of a virus infection and dissemination.
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Doctor of Philosophy (Ph.D.)
College of Medicine
Length of Campus-only Access
Doctoral Dissertation (Open Access)
Cruz Zamora, Maria A., "Early Host Defense Mechanisms against La Crosse Virus Infection" (2020). Electronic Theses and Dissertations, 2020-. 202.