Generation of bat-derived influenza viruses and their reassortants

Reverse Genetics of Bat Influenza A Viruses

New World fruit bats were recently found to harbor two distinct and previously unknown influenza A viruses (IAVs) of the subtypes H17N10 and H18N11. Although viral genome sequences were detected in the liver, intestine, lung, and kidney of infected bats and the complete genome sequences have been isolated from their rectal swab samples, all attempts to isolate an infectious virus from bats in nature have failed. The lack of an infectious bat IAV isolate was overcome by reverse genetic approaches that led to the generation of an infectious virus in vitro. Using such synthetic bat IAVs enabled the identification of their unconventional cell entry via major histocompatibility complex II (MCH-II) molecules and their ability to replicate in mice, ferrets, and bats. Importantly, we also showed that these synthetic recombinant bat IAVs are not able to reassort with conventional IAVs, preventing the acquisition of enhanced transmission properties in non-bat species by reassortment with conventional IAVs. As authentic viruses are key for understanding the molecular biology of bat IAVs, in this chapter, we describe our recently established reverse genetics protocol for generating H17N10 and H18N11 in vitro. This step-by-step protocol starts with cloning of cDNA copies of the viral RNA segments into reverse genetics plasmids, followed by the generation of a highly concentrated stock and finally a method to determine viral titers.

Efficacy of the commercial plant products acting against influenza-a review

Background

Influenza infection always poses a threat to human and animal health. Vaccines and antiviral drugs are recommended to deal with the situation. The drawback of these remedial agents made the scientist change their focus on an alternative therapy. The anti-influenza effects of plants have been extensively studied, and many pharmaceutical companies have prepared their products on this basis.

Main body

The present review documents the successfully launched anti-influenza commercial products. In specific, it exposes the scientifically validated and evidence-based supporting inhibitory action of influenza and its strains.

Conclusion

This review highlighted the efficacy of the commercial products which effectively combat influenza. It provides a complementary strategy to deal with the worst-case scenario of flu. Meanwhile, to face the emerging strains, brand new products are in great necessity besides prevailing and available drugs.

Receptor-Mediated Host Cell Preference of a Bat-Derived Filovirus, Lloviu Virus

Lloviu virus (LLOV), a bat-derived filovirus that is phylogenetically distinct from human pathogenic filoviruses such as Ebola virus (EBOV) and Marburg virus (MARV), was discovered in Europe. However, since infectious LLOV has never been isolated, the biological properties of this virus remain poorly understood. We found that vesicular stomatitis virus (VSV) pseudotyped with the glycoprotein (GP) of LLOV (VSV–LLOV) showed higher infectivity in one bat (Miniopterus sp.)-derived cell line than in the other bat-derived cell lines tested, which was distinct from the tropism of VSV pseudotyped with EBOV (VSV–EBOV) and MARV GPs. We then focused on the interaction between GP and Niemann–Pick C1 (NPC1) protein, one of the cellular receptors of filoviruses. We introduced the Miniopterus bat and human NPC1 genes into NPC1-knockout Vero E6 cells and their susceptibilities to the viruses were compared. The cell line expressing the bat NPC1 showed higher susceptibility to VSV–LLOV than that expressing human NPC1, whereas the opposite preference was seen for VSV–EBOV. Using a site-directed mutagenesis approach, amino acid residues involved in the differential tropism were identified in the NPC1 and GP molecules. Our results suggest that the interaction between GP and NPC1 is an important factor in the tropism of LLOV to a particular bat species.

Inferring the Urban Transmission Potential of Bat Influenza Viruses

Bats are considered natural reservoirs of various, potentially zoonotic viruses, exemplified by the influenza A-like viruses H17N10 and H18N11 in asymptomatic Neotropical bats. These influenza viruses are evolutionarily distinct, are poorly adapted to laboratory mice and ferrets and cannot reassort in vitro with conventional strains to form new influenza subtypes. However, they have attracted renewed attention following reports that their entry in host cells is mediated by the trans-species conserved MHC-II proteins, suggesting that they hold zoonotic potential. Despite the recent studies, the viruses' epidemiology and public health significance remain incompletely understood. Delineating the mechanistic basis of the interactions with their hosts and assessing their global distribution are essential in order to fully assess the zoonotic threat that these strains pose.

Niemann-Pick C1 Heterogeneity of Bat Cells Controls Filovirus Tropism

Fruit bats are suspected to be natural hosts of filoviruses, including Ebola virus (EBOV) and Marburg virus (MARV). Interestingly, however, previous studies suggest that these viruses have different tropisms depending on the bat species. Here, we show a molecular basis underlying the host-range restriction of filoviruses. We find that bat-derived cell lines FBKT1 and ZFBK13-76E show preferential susceptibility to EBOV and MARV, respectively, whereas the other bat cell lines tested are similarly infected with both viruses. In FBKT1 and ZFBK13-76E, unique amino acid (aa) sequences are found in the Niemann-Pick C1 (NPC1) protein, one of the cellular receptors interacting with the filovirus glycoprotein (GP). These aa residues, as well as a few aa differences between EBOV and MARV GPs, are crucial for the differential susceptibility to filoviruses. Taken together, our findings indicate that the heterogeneity of bat NPC1 orthologs is an important factor controlling filovirus species-specific host tropism.