Browsing by Subject "Virus Internalization"
Now showing 1 - 2 of 2
- Results Per Page
- Sort Options
Item Characterization of Host Factors Affecting Viral Entry(2019-04-10) Rinkenberger, Nicholas Ryan; Alto, Neal; Schoggins, John W.; Pfeiffer, Julie K.; Reese, Tiffany A.Viruses are obligate, intracellular parasites. For a virus to infect a host cell, it must gain access to the interior of the host cell by some means. In animals, this often involves the exploitation of host processes such as receptor-mediated endocytosis and vesicular trafficking. Zika virus is an emerging arbovirus with global health and economic impacts. Interestingly, while Asian lineage Zika virus causes human disease and has been associated with severe neurological complications, African lineage Zika virus has only rarely been reported to cause human disease. Large strides have been made in understanding Zika virus infection. However, the mechanism used by Zika virus to enter host cells remains somewhat obscure. In chapter 2, I delineate and compare the pathway utilized by both Asian and African lineage Zika virus to enter host cells. I find that these viruses require clathrin-mediated endocytosis and Rab5a function in a conserved manner. Additionally, all Zika virus strains tested were sensitive to pH in the range of 6.5-6.1 and were reliant on endosomal acidification for infection. I found that Zika virus preferentially fuses with late endosomes. Comparing lineages, Zika virus enters cells in a highly conserved manner. Just as viruses have evolved to exploit host factors to promote their entry and replication, hosts have developed mechanisms of defense against viral infection. Recognition of viral infection by vertebrate hosts results in the expression and secretion of interferon. Interferon signaling subsequently results in the induction of hundreds of interferon-stimulated genes (ISGs) which restrict pathogen infection. Some of these ISGs specifically block viral entry. Surprisingly, a small group of ISGs was previously identified which actually promote viral infection. In chapter 3, I characterize the mechanism of action of MCOLN2, one of the ISGs found to promote viral infection. I assign a role for MCOLN2 in modulating viral entry. I show that MCOLN2 specifically promotes viral vesicular trafficking and subsequent escape from endosomal compartments. This mechanism requires channel activity, occurs independently of antiviral signaling, and broadly applies to enveloped RNA viruses that require endosomal acidification for infection, including influenza A virus, yellow fever virus, and Zika virus.Item Factors That Influence Murine Norovirus Stability and Tropism(2024-05) Budicini, Melissa Renee; Gammon, Don B.; Schoggins, John W.; Pfeiffer, Julie K.; Orchard, Robert C.In this work I investigated factors that influence murine norovirus stability and tropism through two independent projects. Murine norovirus (MNV) is a model system used to study human noroviruses due to its robust replication in cell culture and mouse model. I first investigated the interactions between MNV and bacteria in vitro by determining what bacteria and bacterial components could impact viral thermostability. I found that that specific Gram-positive bacteria and conditioned medium from Gram-positive bacteria could stabilize MNV against heat inactivation. However, I found that Gram-negative bacteria and conditioned medium had no impact on viral stability. These stabilizing effects of bacteria may play a role in viral transmission due to the fact that the virus must remain stable in the environment to transmit to a new host. In my second project I used a forward genetic approach to select for MNV variants with increased host cell range. I found that by serially passaging murine norovirus in human HeLa cells I could select for mutant viruses that increased replication as compared with the parental strain in a non-natural host. The passaged viruses had many mutations spanning the viral genome, however I determined three specific mutations in the NS1/2 protein that allowed for the virus to grow better in human cells. I determined that the adapted viruses have increased replication because they overcame a post-entry replication block in HeLa cells, not because they have increased attachment. This was surprising given that HeLa cells do not have the MNV receptor. These studies show that MNV tropism is not only determined by receptor availability. Overall, these studies illuminate unique aspects of MNV biology that may be applicable to other viruses.