In vitro investigation of the antiviral activity of Ingavirin against human metapneumovirus

The antiviral activity of Ingavirin against human metapneumovirus (HMPV) infection was investigated in vitro. The investigation used the human cell line ChangConjunctiva, permissive for HMPV, clone 1-5C4, and the HMPV strain isolated at the D. I. Ivanovsky Research Institute of Virology. The experimental studies suggest that when added at a concentration of 50 to 500 microg/ml to a nutrient medium 24 hours after HMPV infection, Ingavirin suppressed effectively virus replication by 2.2-3.3 logs, respectively. When used at a concentration of 500 microg/ml 24 hours before cell infection, Ingavirin protected cells from HMPV infection.     

In vitro sensitivity of immature human mast cells to chemotherapeutic agents

Cells from the human immature mast cell line, HMC-1, were tested for their sensitivity to 11 chemotherapeutic agents by changes in viability and incorporation of tritiated thymidine ([3H]-thymidine) after 72 h of in vitro drug exposure. Doxorubicin hydrochloride and cytosine arabinoside were the most active agents against HMC-1 cells at the concentrations tested. Doxorubicin hydrochloride inhibited the incorporation of [3H]-thymidine and decreased the viability of HMC-1 cells by greater than 90% at a concentration of 0.06 microgram/ml. Cytosine arabinoside inhibited the incorporation of [3H]-thymidine and decreased the viability by greater than 95% at a concentration of 0.1 microgram/ml. A clone of HMC-1 cells, A4, with an enhanced percentage (70-80%) of metachromatically staining cells was equally sensitive to these two agents; however, A4 cells were more sensitive to vinblastine sulfate and less sensitive to methylprednisolone than was the parent cell line. Both HMC-1 cells and A4 cells showed approximately equal sensitivity to etoposide and to mitomycin. These results show that human mast cells are susceptible in vitro to a number of commonly used chemotherapeutic drugs.     

Effects of type I interferons in malaria

Type I interferons (IFNs) are a family of cytokines with a wide range of biological activities including anti‐viral and immune‐regulatory functions. Here, we focus on the protozoan parasitic disease malaria, and examine the effects of type I IFN‐signalling during Plasmodium infection of humans and experimental mice. Since the 1960s, there have been many studies in this area, but a simple explanation for the role of type I IFN has not emerged. Although epidemiological data are consistent with roles for type I IFN in influencing malaria disease severity, functional proof of this remains sparse in humans. Several different rodent‐infective Plasmodium species have been employed in in vivo studies of parasite‐sensing, experimental cerebral malaria, lethal malaria, liver‐stage infection, and adaptive T‐cell and B‐cell immunity. A range of different outcomes in these studies suggests a delicately balanced, multi‐faceted and highly complex role for type I IFN‐signalling in malaria. This is perhaps unsurprising given the multiple parasite‐sensing pathways that can trigger type I IFN production, the multiple isoforms of IFN‐α/β that can be produced by both immune and non‐immune cells, the differential effects of acute versus chronic type I IFN production, the role of low level ‘tonic’ type I IFN‐signalling, and that signalling can occur via homodimeric IFNAR1 or heterodimeric IFNAR1/2 receptors. Nevertheless, the data indicate that type I IFN‐signalling controls parasite numbers during liver‐stage infection, and depending on host–parasite genetics, can be either detrimental or beneficial to the host during blood‐stage infection. Furthermore, type I IFN can promote cytotoxic T lymphocyte immune pathology and hinder CD4⁺ T helper cell‐dependent immunity during blood‐stage infection. Hence, type I IFN‐signalling plays highly context‐dependent roles in malaria, which can be beneficial or detrimental to the host.     

The human intracellular Mx-homologous protein is specifically induced by type I interferons

The murine Mx-1 protein is one of the best biochemically and functionally characterized interferon (IFN)-induced proteins that is necessary, and sufficient, for providing resistance to murine cells against viral influenza infection. Recently an intracellular human protein homologous to the murine Mx-1 protein has been identified by means of a specific monoclonal antibody. The restricted induction of this intracellular protein in human mononuclear cells (MNC) by various cytokines was investigated. MNC from 26 of 28 healthy people and 35 of 36 cancer patients before IFN-alpha therapy had no detectable Mx-homologous protein. Incubation of human MNC with IFN-alpha and IFN-beta for 24 h at different concentrations led to a dose-dependent induction of the Mx-homologous protein. All IFN-alpha or IFN-beta preparations tested were equally effective in eliciting this intracellular protein. IFN-gamma induced only 1% of the Mx amount elicited by type-1 IFN compared on a weight basis. Neither interleukin (IL) 1 nor IL3, IL4, IL5, IL6, tumor necrosis factor-alpha/beta, granulocyte colony-stimulating factor (CSF) or granulocyte macrophage-CSF at any of the concentrations tested were capable of eliciting any detectable amount of the Mx homolog, while IL2 was a poor Mx-homologous protein inducer. In the presence of high-titered IFN-alpha antisera both IL2 and IFN-gamma were unable to stimulate this protein, proving that IFN-gamma and IL2 indirectly induce the Mx homolog via IFN-alpha. Therefore, the human Mx-homologous protein is a strictly by type I IFN-regulated protein in human peripheral blood lymphocytes.     

Maturation-dependent responses of human neuronal cells to western equine encephalitis virus infection and type I interferons

Innate cell-autonomous antiviral responses are essential first lines of defense against central nervous system infections but may also contribute to neuropathogenesis. We investigated the relationships between innate immunity and neuronal differentiation using an in vitro culture system with human cell lines to analyze cellular responses to the neurotropic alphavirus western equine encephalitis virus. Human neuronal cells displayed a maturation-dependent reduction in virus-induced cytopathology that was independent of autocrine interferon alpha or beta activity. In addition, maturation was associated with enhanced responsiveness to exogenous stimuli, such that differentiated neurons required five- to ten-fold less type I interferon to suppress viral replication or virus-induced cytopathology compared to immature cells, although this enhanced responsiveness extended to only a subset of unique type I interferons. These results demonstrate that maturation-dependent changes in human neuronal cells may be key determinants in the innate immune response to infections with neurotropic alphaviruses.     

In vitro sensitivity of Chlamydiae to antibiotics

The in vitro activity of 11 antibiotics against 16 Chlamydia trachomatis strains isolated from genital tract and 2 Chlamydia psittaci strains isolated from pulmonary tract. The CMI determination (the lowest dilution of the drug which inhibited the inclusion development when untreated control give 10(3) IFC) was assessed by growth in cycloheximide treated McCoy cells-antibiotics were added after incubation for 2 hours at 37 degrees C. The CMI values for Chlamydia trachomatis and Chlamydia psittaci are similar. The activity of antibiotics by comparison between CMI90 and serial levels. The CMI90 (mg/l) were: doxycycline = 0.2, minocycline = 0.2, roxythromycine = 0.12, érythromycine = 0.5, spiramycine = 4, rifampicine = 0.016, ofloxacine = 4, ciprofloxacine = 4, pefloxacine = 8, lomefloxacine = 8, fleroxacine = 8. For Chlamydia trachomatis species all the strains have the same sensibility, no resistance was detected.     

Systemic lupus erythematosus: all roads lead to type I interferons

In recent years, the study of systemic lupus erythematosus (SLE) patients has revealed a central role for type I interferon (IFN) in disease pathogenesis. IFN induces the unabated activation of peripheral dendritic cells, which select and activate autoreactive T cells rather than deleting them, thus failing to induce peripheral tolerance. IFN also directly affects T cells and B cells. Furthermore, immune complexes binding to FcgammaR and Toll-like receptors provide an amplification loop for IFN production and B-cell activation in SLE. Polymorphisms in genes that control IFN production or its downstream signaling pathway, such as IRF5, might be responsible for some of these alterations. This novel information is leading to the development of IFN antagonists as a potential therapeutic intervention in SLE, thus bringing hope to SLE patients.     

In vitro combined effects of human interferons and interleukin-2 on natural cell-mediated cytotoxicity

In vitro modulation of natural cell-mediated cytotoxicity (NCMC), following sequential treatment of human mononuclear cells (MNC) with cytokines was investigated. Recombinant Interleukin-2 (IL2) used in combination with interferons (IFNs) induced variable effects on the cytolytic function of different MNC preparations obtained from 16 healthy donors. When MNC were treated with IFNs on day 4, after IL2 induction of LAK cells, increase or no change in cytotoxic activity was found. On the other hand, either no change or decrease in LAK activity occured when MNC were treated with IFNs on day 0 before exposure to IL2. In this case the effect of IFNs on NCMC did not correlate with their activity on cell proliferation or on TAC antigen expression. In conclusion the present study points out that the NCMC of MNC of healthy donors, subjected to IL2 treatment in vitro, can be significantly increased by IFNs. However this effect is largely schedule-dependent (i.e. detectable with IL2-IFNs but not with IFNs-IL2 sequence), and can be obtained in a relatively limited number of cases. Moreover it is suggested that these in vitro studies could provide preclinical bases for a rational approach to in vivo treatment with cytokine cascade in a clinical setting.     

Effect of double-stranded RNA and type I interferons on cytomegalovirus reproduction in human fibroblasts

D. I. Ivanovskii Institute of Virology, Academy of Medical Sciences of the USSR, Moscow. (Presented by Academician of the Academy of Medical Sciences of the USSR D. K. L'vov) Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 112, No. 7, pp. 80–83, July, 1991.     

SARS-CoV-2 infection activates a subset of intrinsic pathways to inhibit type I interferons in vitro and in vivo

SARS-CoV-2 infection poses a global challenge to human health. Upon viral infection, host cells initiate the innate antiviral response, which primarily involves type I interferons (I-IFNs), to enable rapid elimination of the invading virus. Previous studies revealed that SARS-CoV-2 infection limits the expression of I-IFNs in vitro and in vivo, but the underlying mechanism remains incompletely elucidated. In the present study, we performed data mining and longitudinal data analysis using SARS-CoV-2-infected normal human bronchial epithelial (NHBE) cells and ferrets, and the results confirmed the strong inhibitory effect of SARS-CoV-2 on the induction of I-IFNs. Moreover, we identified genes that are negatively correlated with IFNB1 expression in vitro and in vivo based on Pearson correlation analysis. We found that SARS-CoV-2 activates numerous intrinsic pathways, such as the circadian rhythm, phosphatidylinositol signaling system, peroxisome, and TNF signaling pathways, to inhibit I-IFNs. These intrinsic inhibitory pathways jointly facilitate the successful immune evasion of SARS-CoV-2. Our study elucidates the underlying mechanism by which SARS-CoV-2 evades the host innate antiviral response in vitro and in vivo, providing theoretical evidence for targeting these immune evasion-associated pathways to combat SARS-CoV-2 infection.     

The role of type I interferons in non-viral infections

Summary: For a long time, the family of type I interferons (IFN‐α/β) has received little attention outside the fields of virology and tumor immunology. In recent years, IFN‐α/β regained the interest of immunologists, due to the phenotypic and functional characterization of IFN‐α/β‐producing cells, the definition of novel immunomodulatory functions and signaling pathways of IFN‐α/β, and the observation that IFN‐α/β not only exerts antiviral effects but is also relevant for the pathogenesis or control of certain bacterial and protozoan infections. This review summarizes the current knowledge on the production and function of IFN‐α/β during non‐viral infections in vitro and in vivo.     

The function of type I interferons in antimicrobial immunity

Type I interferons (IFN-alpha and IFN-beta) were originally described as potent antiviral substances, which are produced upon infection of animal cells with viruses. Despite a large body of literature that has accumulated during the past 25 years, their regulatory function in the immune system is still much less appreciated. Recent studies have highlighted the production of type I IFNs, their function in the immune response to infectious agents and the target cells of these interferons. Type I IFNs clearly affect the release of proinflammatory cytokines or nitric oxide by dendritic cells and macrophages, the capacity of type II interferon (IFN-gamma) to activate phagocytes, the differentiation of T helper cells and the innate control of non-viral pathogens.     

Human B cells fail to secrete type I interferons upon cytoplasmic DNA exposure

Most cells are believed to be capable of producing type I interferons (IFN I) as part of an innate immune response against, for instance, viral infections. In macrophages, IFN I is potently induced upon cytoplasmic exposure to foreign nucleic acids. Infection of these cells with herpesviruses leads to triggering of the DNA sensors interferon-inducible protein 16 (IFI16) and cyclic GMP-AMP (cGAMP) synthase (cGAS). Thereby, the stimulator of interferon genes (STING) and the downstream molecules TANK-binding kinase 1 (TBK1) and interferon regulatory factor 3 (IRF3) are sequentially activated culminating in IFN I secretion.Human gamma-herpesviruses, such as Epstein-Barr virus (EBV), exploit B cells as a reservoir for persistent infection. In this study, we investigated whether human B cells, similar to macrophages, engage the cytoplasmic DNA sensing pathway to induce an innate immune response. We found that the B cells fail to secrete IFN I upon cytoplasmic DNA exposure, although they express the DNA sensors cGAS and IFI16 and the signaling components TBK1 and IRF3. In primary human B lymphocytes and EBV-negative B cell lines, this deficiency is explained by a lack of detectable levels of the central adaptor protein STING. In contrast, EBV-transformed B cell lines did express STING, yet both these lines as well as STING-reconstituted EBV-negative B cells did not produce IFN I upon dsDNA or cGAMP stimulation. Our combined data show that the cytoplasmic DNA sensing pathway is dysfunctional in human B cells. This exemplifies that certain cell types cannot induce IFN I in response to cytoplasmic DNA exposure providing a potential niche for viral persistence.     

In vitro sensitivity of Mycobacterium xenopi to five antibiotics

We tested 20 strains of Mycobacterium xenopi (M. xenopi) in order to evaluate their in vitro sensitivity to amikacine, clarithromycine, ethambutol, ofloxacine and rifampicin, by establishing minimal inhibitory concentration (MIC) on agar medium. MICs of amikacine, clarithromycine and ofloxacine are low, so that these antibiotics can be used in the treatment of M. xenopi infections. MICs of ethambutol are higher than seric concentrations. Though, its therapeutic use is due to its in vivo ability to enhance penetration of other antibiotics in mycobacteria. Strain sensitivity to rifampicin seems heterogeneous but the small number of tested strains does not entitle the exclusion of rifampicin from the treatment of M. xenopi infections.