The Influenza A Virus Non-structural Protein NS1 Upregulates The Expression of Collagen Triple Helix Repeat Containing 1 Protein

Positive Regulation of Cellular Proteins by Influenza Virus for Productive Infection

Influenza viruses cause annual epidemics and occasional pandemics through respiratory tract infections, giving rise to substantial morbidity and mortality worldwide. Influenza viruses extensively interact with host cellular proteins and exploit a variety of cellular pathways to accomplish their infection cycle. Some of the cellular proteins that display negative effects on the virus are degraded by the virus. However, there are also various proteins upregulated by influenza at the expression and/or activation levels. It has been well-established that a large number of host antiviral proteins such as type I interferon-stimulated genes are elevated by viral infection. On the other hand, there are also many cellular proteins that are induced directly by the virus, which are considered as pro-viral factors and often indispensable for rigorous viral propagation or pathogenicity. Here, we review the recent advances in our understanding of the cellular factors deemed to be upregulated and utilized by the influenza virus. The focus is placed on the functions of these pro-viral proteins and the mechanisms associated with promoting viral amplification, evading host immunity, or enhancing viral pathogenicity. Investigating the process of how influenza viruses hijack cellular proteins could provide a framework for inventing the host-factor-targeted drugs to conquer influenza.

Alternative Experimental Models for Studying Influenza Proteins, Host-Virus Interactions and Anti-Influenza Drugs

Ninety years after the discovery of the virus causing the influenza disease, this malady remains one of the biggest public health threats to mankind. Currently available drugs and vaccines only partially reduce deaths and hospitalizations. Some of the reasons for this disturbing situation stem from the sophistication of the viral machinery, but another reason is the lack of a complete understanding of the molecular and physiological basis of viral infections and host-pathogen interactions. Even the functions of the influenza proteins, their mechanisms of action and interaction with host proteins have not been fully revealed. These questions have traditionally been studied in mammalian animal models, mainly ferrets and mice (as well as pigs and non-human primates) and in cell lines. Although obviously relevant as models to humans, these experimental systems are very complex and are not conveniently accessible to various genetic, molecular and biochemical approaches. The fact that influenza remains an unsolved problem, in combination with the limitations of the conventional experimental models, motivated increasing attempts to use the power of other models, such as low eukaryotes, including invertebrate, and primary cell cultures. In this review, we summarized the efforts to study influenza in yeast, Drosophila, zebrafish and primary human tissue cultures and the major contributions these studies have made toward a better understanding of the disease. We feel that these models are still under-utilized and we highlight the unique potential each model has for better comprehending virus-host interactions and viral protein function.