The Z Proteins of Pathogenic but Not Nonpathogenic Arenaviruses Inhibit RIG-i-Like Receptor-Dependent Interferon Production

Abstract

Arenavirus pathogens cause a wide spectrum of diseases in humans ranging from central nervous system disease to lethal hemorrhagic fevers with few treatment options. The reason why some arenaviruses can cause severe human diseases while others cannot is unknown. We find that the Z proteins of all known pathogenic arenaviruses, lymphocytic choriomeningitis virus ( IMPORTANCEWe show that all known human-pathogenic arenaviruses share an innate immune suppression mechanism that is based on viral Z protein-mediated RLR inhibition. Our report offers important insights into the potential mechanism of arenavirus pathogenesis, provides a convenient way to evaluate the pathogenic potential of known and/or emerging arenaviruses, and reveals a novel target for the development of broad-spectrum therapies to treat this group of diverse pathogens. More broadly, our report provides a better understanding of the mechanisms of viral immune suppression and host-pathogen interactions. Intracellular RNA viruses are recognized by a family of cytosolic RNA helicase proteins called retinoic acid-inducible gene 1 (RIG-i)-like receptors (RLRs) to activate the antiviral and inflammatory signals (1, 2). The RLR members include RIG-i, Melanoma Differentiation-Associated protein 5 (MDA5), and Laboratory of Genetics and Physiology 2 (LGP2) (3-5). RIG-i recognizes short double-stranded RNA (dsRNA) with 5= triphosphate, while MDA5 recognizes long RNA duplexes (6). Upon ligand binding by the C-terminal domains (CTD) of RIG-i and MDA5, these proteins undergo conformational changes to activate the N-terminal CARD domains that mediate their interactions with the adaptor molecule mitochondrial antiviral signaling (MAVS)/IPS-1/virus-induced signaling adaptor (VISA)/Cardif to trigger the signaling cascades that consist of tumor necrosis factor (TNF) receptor-associated factors (TRAFs), TANK-binding kinase 1 (TBK1), and inhibitor-B kinase ε (IKKε) to activate transcription factors NF-B, interferon (IFN) regulatory factor 3 (IRF3), and IRF7, which induce the production of the type I IFNs and other cytokines (3). The RLR pathway is essential for host innate immunity to RNA viruses and is thus a major target of viral immune evasion mechanisms (4, 7). Influenza virus NS1 inhibits RIG-i activation by interacting with TRIM25 to prevent RIG-i ubiquitinylation (8). Paramyxovirus V protein binds and inhibits MDA5 (9). Ebola virus (EBOV) VP35 blocks RLR signaling through multiple mechanisms such as sequestering the RIG-i cofactor PKR activator (PACT), preventing the interactions of TBK1 and IKKε with IRFs, and inhibiting IRF7 activity (10-14). Arenaviral nucleoprotein (NP) strongly inhibits the production of type I IFNs through its DEDDH exoribonuclease (RNase) activity, possibly by degrading the immunostimulatory dsRNA substrates (15)(16)(17)(18)(19)(20).Arenaviruses are a diverse family of negative-strand enveloped RNA viruses with a bisegmented RNA genome, which encodes two proteins on each segment in an ambisense orientation-glycoprotein GPC and nuc...

The New World arenavirus Tacaribe virus induces caspase-dependent apoptosis in infected cells

“…Using this approach, we have previously identified differences in the induction of cytokine responses to infection with TCRV or JUNV in macrophages, as well as differences in their influence on host cell apoptosis (Groseth et al, 2011;Wolff et al, 2013a). Other known differences that also might play a role for the virulence include receptor usage (Abraham et al, 2009), as well as the ability to engage in IFN antagonism (Xing et al, 2015). Previous studies have shown that TCRV lacks a novel NP-mediated anti-apoptotic function that was described for JUNV (Wolff et al, 2013a), and together with the observation that TCRV infection also induces severe cytopathic effects (CPEs) during infection in cell culture (Groseth et al, 2011), this suggests that cell death might be due at least in part to apoptotic responses.…”

A Novel Live Pichinde Virus-Based Vaccine Vector Induces Enhanced Humoral and Cellular Immunity after a Booster Dose

“…The generally innocuous nature of PICV is also supported by our recent molecular analysis of the viral gene products. We found that the Z proteins of all known human arenavirus pathogens, including the low-risk pathogen LCMV and the highly virulent pathogen Lassa fever virus (LASV), but not those of others such as PICV, can inhibit the RIG-I-like receptors (RLRs) (5). Therefore, we believe that PICV has a better biosafety profile than LCMV, but like LCMV, PICV can induce strong immune responses, especially cellular immunity (19,22).…”

“…The arenavirus is composed of a total of four genes on two genomic RNA segments in opposite orientations (1). The Z protein, produced from the large (L) genomic segment, is a small RING domain-containing matrix protein that mediates virus budding, regulates viral RNA synthesis, and mediates host immune suppression (4,5). The large L protein (ϳ200 kDa), also encoded on the L segment, is the RNA-dependent RNA polymerase (RdRp), which is required for viral RNA synthesis (6).…”

Molecular-Biological Peculiarities of Arenavirus Reproduction in Sensitive Cells

“…аналогичным образом первичные макрофаги чело-века показывают более высокий уровень продукции интерлейкина-6, интерлейкина-10 и α-интерферона при инфицировании вирусом такарибе по сравнению с инфицированием патогенным для человека вирусом хунин [7]. показано, что Z-белок всех известных па-тогенных аренавирусов, в отличие от непатогенных, способен ингибировать активацию макрофагов [27]. поскольку макрофаги и дендритные клетки являют-ся антигенпрезентирующими клетками, играющими важную роль в формировании иммунного ответа, ингибирование этих клеток приводит к иммунной супрессии, которая во многом определяет патогенез вирусных геморрагических лихорадок [13].…”

“…белок Z патогенных для человека арена-вирусов ингибируют рецепторы, индуцирующие образование интерферона [27]. процесс ингибиро-вания осуществляется в результате взаимодействия N-концевой последовательности белка Z (31 амино-кислотный остаток) и N-концевой последователь-ности соответствующего рецептора, что затрудняет связывание последнего с митохондриальным сиг-нальным белком.…”