Biology subjects

Kipar, A.

Publications and source records attributed to Kipar, A..

41 records · Page 3Linked to original sources

bioRxiv2020

The WD and linker domains of ATG16L1 required for non canonical autophagy limit lethal influenza A virus infection at epithelial surfaces.

Respiratory viruses such as influenza A virus (IAV) and SARS-CoV-2 (Covid-19) cause pandemic infections where cytokine storm syndrome, lung inflammation and pneumonia lead to high mortality. Given the high social and economic cost of these viruses, there is an urgent need for a comprehensive understanding of how the airways defend against virus infection. Viruses entering cells by endocytosis are killed when delivered to lysosomes for degradation. Lysosome delivery is facilitated by non-canonical autophagy pathways that conjugate LC3 to endo-lysosome compartments to enhance lysosome fusion. Here we use mice lacking the WD and linker domains of ATG16L1 to demonstrate that non-canonical autophagy protects mice from lethal IAV infection of the airways. Mice with systemic loss of non-canonical autophagy are exquisitely sensitive to low-pathogenicity murine-adapted IAV where extensive viral replication throughout the lungs, coupled with cytokine amplification mediated by plasmacytoid dendritic cells, leads to fulminant pneumonia, lung inflammation and high mortality. IAV infection was controlled within epithelial barriers where non-canonical autophagy slowed fusion of IAV with endosomes and reduced activation of interferon signalling. This was consistent with conditional mouse models and ex vivo analysis showing that protection against IAV infection of lung was independent of phagocytes and other leukocytes. This establishes non-canonical autophagy pathways in airway epithelial cells as a novel innate defence mechanism that can restrict IAV infection and lethal inflammation at respiratory surfaces.

microbiology↗

bioRxiv2020

Identification of Reptarenaviruses, Hartmaniviruses and a Novel Chuvirus in Captive Brazilian Native Boa Constrictors with Boid Inclusion Body Disease

Boid Inclusion Body Disease (BIBD) is a transmissible viral disease of captive snakes that causes severe losses in snake collections worldwide. It is caused by reptarenavirus infection, which can persist over several years without overt signs, but is generally associated with the eventual death of the affected snakes. Thus far, reports have confirmed existence of reptarenaviruses in captive snakes in North America, Europe, and Australia, but there is no evidence that it also occurs in wild snakes. BIBD affects both boas and pythons, the habitats of which do not naturally overlap. Herein, we studied Brazilian captive snakes with BIBD using a metatranscriptomic approach, and report the identification of novel reptarenaviruses, hartmaniviruses, and a new species in the family Chuviridae. The reptarenavirus L segments identified represent six novel species, while we only found a single novel reptarenavirus S segment. Until now, hartmaniviruses had been identified only in European captive boas with BIBD, and the present results increase the number of known hartmanivirus species from four to six. The newly identified chuvirus showed 38.4%, 40.9%, and 48.1% amino acid identity to the nucleoprotein, glycoprotein, and RNA-dependent RNA polymerase of its closest relative, Guangdong red-banded snake chuvirus-like virus. Although we cannot rule out the possibility that the found viruses originated from imported snakes, the results suggest that the viruses would circulate in indigenous snake populations. IMPORTANCEBoid Inclusion Body Disease (BIBD) caused by reptarenavirus infection affects captive snake populations worldwide, but the reservoir hosts of reptarenaviruses remain unknown. Herein, we report the identification of novel reptarenavirus and hartmanivirus species, and a chuvirus in captive Brazilian boas with BIBD. Three of the four snakes studied showed co-infection with all three viruses, and one of the snakes harbored three novel reptarenavirus L and one novel S segment. The samples originated from collections with Brazilian indigenous snakes only, which could indicate that these viruses circulate in wild snakes. The findings could further indicate that boid snakes are the natural reservoir of reptarena- and hartmaniviruses commonly found in captive snakes. The snakes infected with the novel chuvirus all suffered from BIBD; it is therefore not possible to comment on its potential pathogenicity and contribution to the observed changes in the present case material.

microbiology↗

bioRxiv2019

A novel experimental system reveals immunoregulatory responses as mediators of persistent orthohantavirus infections in a rodent reservoir host

Orthohantaviruses are globally emerging zoonotic pathogens. Human infections are characterized by an overt immune response that is efficient at counteracting virus replication but can also cause severe tissue damage. In contrast, orthohantavirus infections in rodent reservoir hosts are persistent and asymptomatic. The mechanisms facilitating asymptomatic virus persistence in reservoir hosts are not well understood but could help to guide therapeutic strategies for human infections. Here we report on a study using in vivo and in vitro experiments to investigate immune responses associated with persistent Puumala orthohantavirus (PUUV) infections in the bank vole (Myodes glareolus), its reservoir host. We examined adaptive cellular and humoral responses by quantifying changes in T-cell related gene expression in the spleen and immunoglobulin (Ig) responses in blood, respectively. Since existing Vero E6-cell adapted hantavirus isolates have been demonstrated to have lost their wild-type infection characteristics, infections were conducted with a novel PUUV strain isolated on a bank vole cell line. Whole virus genome sequencing revealed that only minor sequence changes occurred during the isolation process, and critically, experimental infections of bank voles with the new isolate resembled natural infections. In vitro infection of bank vole splenocytes with the novel isolate demonstrated that PUUV promotes immunoregulatory responses by inducing interleukin-10, a cytokine strongly associated with chronic viral infections. A delayed virus-specific humoral response occurred in experimentally infected bank voles, which is likely to allow for initial virus replication and the establishment of persistent infections. These results suggest that host immunoregulation facilitates persistent orthohantavirus infections in reservoir hosts.\n\nImportanceOrthohantaviruses are a group of global pathogens that regularly spillover from rodent reservoirs into humans and can cause severe disease. Conversely, infections in reservoir hosts do not cause obvious adverse effects. The mechanisms responsible for persistent asymptomatic reservoir infections are unknown, and progress has been hindered by the absence of an adequate experimental system. Knowledge on these mechanisms could help provide strategies to treat human infections. We developed and validated an experimental system based on an orthohantavirus isolated in cells of its vole reservoir host. Using animal and cell culture experiments in the reservoir host system, we demonstrated that infection suppresses immunity in the vole reservoir via specific mechanisms, likely allowing the virus to take hold and preventing immune responses that can cause self-damage.

microbiology↗

bioRxiv2019

Snake deltavirus utilizes envelope proteins of different viruses to generate infectious particles

Hepatitis D virus (HDV) is the only known human satellite virus, and it requires hepatitis B virus (HBV) to form infectious particles. Until 2018 HDV was the sole representative of the genus Deltavirus. The subsequent identification of HDV-like agents in non-human hosts indicated a much longer evolutionary history of deltaviruses than previously hypothesized. Interestingly, none of the HDV-like agents were found in co-infection with an HBV-like agent suggesting that these viruses use different helper virus(es). Here we show, using snake deltavirus (SDeV), that HBV represents only a single example of helper viruses for deltaviruses. We cloned the SDeV genome into a mammalian expression plasmid, and by transfection could initiate SDeV replication in cultured snake and mammalian cells. By superinfecting SDeV infected cells with arenaviruses, or by transfecting different viral surface proteins, we could induce infectious SDeV particle production. Our findings indicate that deltaviruses can likely use a multitude of helper viruses or even viral glycoproteins to form infectious particles. Persistent and recurrent infections would be beneficial for the spread of deltaviruses. It seems plausible that new human and veterinary disease associations with deltavirus infections will be identified in the future.

microbiology↗

bioRxiv2018

Identification of a novel deltavirus in Boa constrictor

Human hepatitis D virus (hHDV) forms the genus Deltavirus which has not been assigned to any virus family. hHDV is a satellite virus and needs hepatitis B virus (HBV) to make infectious particles. Deltaviruses are thought to have evolved in humans, since they have thus far not been identified elsewhere. Herein we report, prompted by a recent observation of HDV-like agent in birds, the identification of a deltavirus in a snake (Boa constrictor) designated as snake-HDV (sHDV). The circular 1711 nt RNA genome of the newly identified virus resembles hHDV in its coding strategy and size. We discovered sHDV when performing a meta-transcriptomic study on brain samples of two boas with central nervous system signs. We did not identify accompanying HBV-like sequences in the samples. By sequence comparison, the putative hepatitis D antigen (HDAg) of sHDV, encoded by one of the two open reading frames (ORFs), is roughly 50% identical to the previously known HDAgs. We used antiserum raised against recombinant snake HDAg to demonstrate a broad viral target cell spectrum, ranging from neurons over epithelial cells to leukocytes. Using RT-PCR, we detected sHDV RNA also in the liver and blood of the two snakes and could show sHDV infection not only in two of their juvenile offspring, but also in a water python (Liasis mackloti savuensis) in the same snake colony, indicating potentially vertical and horizontal transmission. The finding of abundant sHDAg in several tissues suggests that sHDV actively replicated in the studied animals. Our findings suggest that sHDV spread may not be restricted to hepadnavirus co-infection. This would imply that deltaviruses may employ other enveloped viruses for producing infectious particles.

microbiology↗