First Insight into the Modulation of Noncanonical NF-κB Signaling Components by Poxviruses in Established Immune-Derived Cell Lines: An In Vitro Model of Ectromelia Virus Infection

Dendritic cells (DCs) and macrophages are the first line of antiviral immunity. Viral pathogens exploit these cell populations for their efficient replication and dissemination via the modulation of intracellular signaling pathways. Disruption of the noncanonical nuclear factor κ-light-chain-enhancer of activated B cells (NF-κB) signaling has frequently been observed in lymphoid cells upon infection with oncogenic viruses. However, several nononcogenic viruses have been shown to manipulate the noncanonical NF-κB signaling in different cell types. This study demonstrates the modulating effect of ectromelia virus (ECTV) on the components of the noncanonical NF-κB signaling pathway in established murine cell lines: JAWS II DCs and RAW 264.7 macrophages. ECTV affected the activation of TRAF2, cIAP1, RelB, and p100 upon cell treatment with both canonical and noncanonical NF-κB stimuli and thus impeded DNA binding by RelB and p52. ECTV also inhibited the expression of numerous genes related to the noncanonical NF-κB pathway and RelB-dependent gene expression in the cells treated with canonical and noncanonical NF-κB activators. Thus, our data strongly suggest that ECTV influenced the noncanonical NF-κB signaling components in the in vitro models. These findings provide new insights into the noncanonical NF-κB signaling components and their manipulation by poxviruses in vitro.

Chronic Lymphocytic Choriomeningitis Infection Causes Susceptibility to Mousepox and Impairs Natural Killer Cell Maturation and Function

ABSTRACT Chronic viral infections. like those of humans with cytomegalovirus, human immunodeficiency virus (even when under antiretroviral therapy), and hepatitis C virus or those of mice with lymphocytic choriomeningitis virus (LCMV) clone 13 (CL13), result in immune dysfunction that predisposes the host to severe infections with unrelated pathogens. It is known that C57BL/6 (B6) mice are resistant to mousepox, a lethal disease caused by the orthopoxvirus ectromelia virus (ECTV), and that this resistance requires natural killer (NK) cells and other immune cells. We show that most B6 mice chronically infected with CL13 succumb to mousepox but that most of those that recovered from acute infection with the LCMV Armstrong (Arm) strain survive. We also show that B6 mice chronically infected with CL13 and those that recovered from Arm infection have a reduced frequency and a reduced number of NK cells. However, at steady state, NK cells in mice that have recovered from Arm infection mature normally and, in response to ECTV, get activated, become more mature, proliferate, and increase their cytotoxicity in vivo. Conversely, in mice chronically infected with CL13, NK cells are immature and residually activated, and following ECTV infection, they do not mature, proliferate, or increase their cytotoxicity. Given the well-established importance of NK cells in resistance to mousepox, these data suggest that the NK cell dysfunction caused by CL13 persistence may contribute to the susceptibility of CL13-infected mice to mousepox. Whether chronic infections similarly affect NK cells in humans should be explored. IMPORTANCE Infection of adult mice with the clone 13 (CL13) strain of lymphocytic choriomeningitis virus (LCMV) is extensively used as a model of chronic infection. In this paper, we show that mice chronically infected with CL13 succumb to challenge with ectromelia virus (ECTV; the agent of mousepox) and that natural killer (NK) cells in CL13-infected mice are reduced in numbers and have an immature and partially activated phenotype but do respond to ECTV. These data may provide additional clues why humans chronically infected with certain pathogens are less resistant to viral diseases.

Investigation of the Antiviral Activity of Experimental Samples Obtained from the Grass and Roots of Alchemilla vulgaris L. Against Vaccinia Virus and Ectromelia Virus

Introduction. The abolition of smallpox vaccination after its elimination in 1980 led to a decrease in the immunocompromised immunity in humans. Zoonotic monkeypox, camelpox, buffalopox and cowpox viruses that are close to the variola virus also pose a danger to humans. In Russia today there are no effective and safe medicines for the prevention and treatment of smallpox and other orthopoxvirus infections in humans and animals. The Lady's mantle (Alchemilla vulgaris) is a promising source for the development of new antiviral drugs. Previous studies have found that Alchemilla vulgaris shows activity against influenza virus and herpes simplex virus.Aim. The aim of this work was to study the chemical composition and antiviral activity of extracts from the roots and the grass of Alchemilla vulgaris against orthopoxviruses.Materials and methods. Qualitative analysis of the samples was performed by high performance liquid chromatography. Quantitative analysis was performed using a complex of spectrophotometric methods. To determine the toxicity and antiviral activity of experimental samples from Alchemilla vulgaris in vitro, a transplantable Vero cell culture was used. Antiviral activity of the obtained preparations was evaluated by reducing the infectivity (titer) of orthopoxviruses in the monolayer of Vero cells infected with orthopoxviruses in the presence of preparations with different concentrations relative to the cell culture infected with orthopoxviruses without the preparations.Results and discussion. It was shown that the experimental sample from Alchemilla vulgaris obtained by the method of ethyl acetate extraction from the roots of the studied plant and purified with chloroform contains mainly catechins and leucoanthocyanins (70 %). In parallel, extract from the raw mass of the grass of the plant purified with chloroform and ethanol contains the amount of flavonoids (71 %). Wherein the content of flavonoids in unpurified ethanol extracts from the roots and the grass of Alchemilla vulgaris composed 5 % and 6 %, respectively. It was revealed that purified preparations obtained from Alchemilla vulgaris roots when using ethyl acetate and ethanol as extractants showed antiviral activity against vaccinia virus and ectromelia virus, as well as preparations obtained from grass by ethanol extraction.Conclusion. Thus, purified ethyl acetate extracts from the roots and ethanol extracts from the wet grass mass of Alchemilla vulgaris exhibit antiviral activity against orthopoxviruses in vitro.