IL-4/IL-13 polarization of macrophages enhances Ebola virus glycoprotein-dependent infection.

Background: Ebolavirus (EBOV) outbreaks, while sporadic, cause tremendous morbidity and mortality. No therapeutics or vaccines are currently licensed; however, a vaccine has shown promise in clinical trials. A critical step towards development of effective therapeutics is a better understanding of factors that govern host susceptibility to this pathogen. As macrophages are an important cell population targeted during virus replication, we explore the effect of cytokine polarization on macrophage infection. Methods/Main findings: We utilized a BSL2 EBOV model virus, infectious, recombinant vesicular stomatitis virus encoding EBOV glycoprotein (GP) (rVSV/EBOV GP) in place of its native glycoprotein. Macrophages polarized towards a M2-like anti-inflammatory state by combined IL-4 and IL-13 treatment were more susceptible to rVSV/EBOV GP, but not to wild-type VSV (rVSV/G), suggesting that EBOV GP-dependent entry events were enhanced by these cytokines. Examination of RNA expression of known surface receptors that bind and internalize filoviruses demonstrated that IL-4/IL-13 stimulated expression of the C-type lectin receptor DC-SIGN in human macrophages and addition of the competitive inhibitor mannan abrogated IL-4/IL-13 enhanced infection. Two murine DC-SIGN-like family members, SIGNR3 and SIGNR5, were upregulated by IL-4/IL-13 in murine macrophages, but only SIGNR3 enhanced virus infection in a mannan-inhibited manner, suggesting that murine SIGNR3 plays a similar role to human DC-SIGN. In vivo IL-4/IL-13 administration significantly increased virus-mediated mortality in a mouse model and transfer of ex vivo IL-4/IL-13-treated murine peritoneal macrophages into the peritoneal cavity of mice enhanced pathogenesis. Significance: These studies highlight the ability of macrophage polarization to influence EBOV GP-dependent virus replication in vivo and ex vivo, with M2a polarization upregulating cell surface receptor expression and thereby enhancing virus replication. Our findings provide an increased understanding of the host factors in macrophages governing susceptibility to filoviruses and identify novel murine receptors mediating EBOV entry. Author summary: Ebola virus causes outbreaks in Central and West Africa, often resulting in high mortality rates. Macrophages are important cell targets for the virus, yet infection of these cells remains poorly understood. Here, we show that macrophages stimulated with the immunomodulatory cytokines IL-4 and IL-13 are significantly more susceptible than unstimulated cells to a model virus that expresses the Ebola virus glycoprotein. These cytokines increase virus entry by enhancing the expression of the cell surface receptors DC-SIGN in humans and SIGNR3 in mice. Blocking availability of those receptors reduced virus load. Consistent with an important role for macrophages during EBOV infection, reconstitution of mice with macrophages treated with IL-4 and IL-13 exacerbated virus pathogenesis. Our studies argue for the critical importance of the macrophages and their response to immunomodulatory cytokines in controlling the pathological consequences of Ebola virus glycoprotein-dependent infections and highlight an important aspect of filovirus/macrophage interaction that if controlled could decrease virus pathogenesis. [ABSTRACT FROM AUTHOR]