Inflammatory monocytes mediate control of acute alphavirus infection in mice

Abstract

Chikungunya virus (CHIKV) and Ross River virus (RRV) are mosquito-transmitted alphaviruses that cause debilitating acute and chronic musculoskeletal disease. Monocytes are implicated in the pathogenesis of these infections; however, their specific roles are not well defined. To investigate the role of inflammatory Ly6ChiCCR2+ monocytes in alphavirus pathogenesis, we used CCR2-DTR transgenic mice, enabling depletion of these cells by administration of diptheria toxin (DT). DT-treated CCR2-DTR mice displayed more severe disease following CHIKV and RRV infection and had fewer Ly6Chi monocytes and NK cells in circulation and muscle tissue compared with DT-treated WT mice. Furthermore, depletion of CCR2+ or Gr1+ cells, but not NK cells or neutrophils alone, restored virulence and increased viral loads in mice infected with an RRV strain encoding attenuating mutations in nsP1 to levels detected in monocyte-depleted mice infected with fully virulent RRV. Disease severity and viral loads also were increased in DT-treated CCR2-DTR+;Rag1-/- mice infected with the nsP1 mutant virus, confirming that these effects are independent of adaptive immunity. Monocytes and macrophages sorted from muscle tissue of RRV-infected mice were viral RNA positive and had elevated expression of Irf7, and co-culture of Ly6Chi monocytes with RRV-infected cells resulted in induction of type I IFN gene expression in monocytes that was Irf3;Irf7 and Mavs-dependent. Consistent with these data, viral loads of the attenuated nsP1 mutant virus were equivalent to those of WT RRV in Mavs-/- mice. Finally, reconstitution of Irf3-/-;Irf7-/- mice with CCR2-DTR bone marrow rescued mice from severe infection, and this effect was reversed by depletion of CCR2+ cells, indicating that CCR2+ hematopoietic cells are capable of inducing an antiviral response. Collectively, these data suggest that MAVS-dependent production of type I IFN by monocytes is critical for control of acute alphavirus infection and that determinants in nsP1, the viral RNA capping protein, counteract this response.

Mutating chikungunya virus non‐structural protein produces potent live‐attenuated vaccine candidate

“…This result is consistently observed on the UMAP biplot, which showed that mock‐infected joints were lacking an infiltrating leukocyte population corresponding to PhenoGraph clusters 1, 13, 14, 19, 29, 30, 32, 33 (Fig C–E). These clusters are collectively made up of populations expressing CD11b + , CD64 + , Ly6C hi , and MHC‐II + (Figs E and EV3B), indicative of inflammatory monocytes (Haist et al , ). Interestingly, the RH‐CHIKV‐infected group diverged the most from WT‐CHIKV and showed the highest level of similarity to the mock‐infected group (Fig B).…”

Mayaro virus replication restriction and induction of muscular inflammation in mice are dependent on age and type-I interferon response

“…Macrophage activation has a crucial role in articular and muscular inflammation-derived lesions in RRV and CHIKV infection (22,44). In addition, the production of type I IFN by activated inflammatory monocytes has been suggested as crucial to control acute RRV infection in mice (25). Here, we observed moderate cellular infiltrate on the focus of necrosis and high expression of inflammatory mediators in the muscle of MAYV infected mice, including TNF levels that may contribute to tissue damage.…”

“…Similar diversity and intensity of clinic signals were observed in WT 11-dayold mice ( Table 1). We also investigated MAYV infection in adult recombination activation gene-1 deficient mice (RAG1 -/-), which do not maturate B and T lymphocytes (26), used as a model to investigate the involvement of adaptive immunity in diseases (25). MAYV infection of adult RAG1 -/mice did not cause lethality, weight loss, and even other clinical signals observed in young WT and adult IFNAR -/mice (Table 1).…”

“…Consistent with this, a difference in cytokine expression between MAYV and CHIKV infection in human U937 cell lineage (21) 24). It was demonstrated that inflammatory monocyte infiltrates trigger tissue damage, contributing to the severity of the disease (25). However, currently, there is no systematic study evaluating replication, tissues damage, and immune activation in MAYV-infected mice.…”

dsRNA-Seq: Identification of viral infection by purifying and sequencing dsRNA

“…Total RNA from Vero cells infected with dengue virus type 2 (New Guinea C), influenza A (H3N2 Udorn) or mock-infected was extracted using Trizol (Thermo-Scientific) [19] and provided by Alex Stabell and Sara Sawyer (University of Colorado, Boulder). Total RNA extracted from whole quad muscle collected 5 days post-infection from C57BL/6J mice that were mock-infected or infected with Ross River virus (T48) as described in [20] was provided by Kelsey Haist and Thomas Morrison (University of Colorado, Anschutz Medical Campus). All mouse studies were performed at the University of Colorado Anschutz Medical Campus (Animal Welfare Assurance #A 3269-01) using protocols approved by the University of Colorado Institutional Animal Care and Use Committee and in accordance with the recommendations in the Guide for the Care and Use of Laboratory Animals of the National Institutes of Health.…”