Abstract
Purpose :
The complement system (CS) contributes to the initial containment of viral and bacterial pathogens and clearance of dying cells in circulation. Previously, we reported mice deficient in complement component 3 (C3KO mice) were more sensitive than wild type (WT) to ocular HSV-1 infection as measured by a reduction in cumulative survival and elevated viral titers in the nervous system but not the cornea between days 3-7 post infection (pi). The present study was undertaken to determine if complement deficiency impacted virus replication and associated changes in inflammation at earlier time points in the cornea.
Methods :
Male and female C3KO and WT mice (6-12 weeks old) were anesthetized and subsequently challenged in the cornea with 500 PFU HSV-1 McKrae. Viral titers, viral copy number, and lytic gene expression were measured 12-24 hr pi by plaque assay, PCR, and real time RT-PCR, respectively. Leukocyte infiltration was evaluated by spectral flow cytometry. Anti-viral gene expression and cytokine/chemokine levels were measured 12-24 hr pi by real time RT-PCR and multiplex assays, respectively. Data were analyzed for significance (p<.05) using GraphPad software
Results :
C3KO mice were found to possess significantly (p<.05) less infectious virus in the cornea at 24 hr pi that corresponded to a decrease in viral genome copy number as well as expression of HSV-1 lytic genes at 12 and 24 hr pi compared to WT animals. Flow cytometry acquisition found no differences in the myeloid cell populations residing in the cornea including total macrophage and neutrophil populations at 24 hr pi with minimal infiltrating cell populations detected at the 12 hr pi time point. Of the 25 analytes measured at 12 and 24 hr pi, only CCL3 (MIP-1α) was found to be different between WT and C3KO mice with > 2-fold increased levels (p<.05, ANOVA and Tukey’s post-hoc t-test) in the cornea of WT mice at 12 hr pi. C3KO mouse resistance to HSV-1 infection at the early time points correlated with a significant increase in type I interferon (IFN) gene expression including IFN-α1 and IFN-β and downstream effector genes including tetherin and RNase L in the cornea (p<.05, Mann-Whitney rank order test).
Conclusions :
These results suggest early activation of the CS interferes with the induction of the type I IFN response that leads to a transient increase in virus replication following corneal HSV-1 infection.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.