Date of Award
Doctor of Philosophy (PhD)
Vector-borne diseases (VBDs) are human illnesses that are transmitted by vectors such as ticks, mosquitoes, and fleas. These arthropods transmit infectious pathogens such as viruses, protozoa, and bacteria, to humans during their blood-feeding. According to the estimation of the WHO, billions of people are affected by VBDs worldwide, and about 700,000 deaths are reported annually. Currently, very few reliable VBDs control approaches and vaccines available to treat various VBDs. Additionally, approaches to control arthropod’ proliferation and migration are difficult to develop. Furthermore, molecular determinants and mechanisms for the transmission are poorly understood. This work describes two studies identifying the novel role for exosomes in facilitating transmission of viral infectious material and viral infections.
The first study focused on tick-borne pathogen transmission via exosomes derived from several different cell types. The conclusions suggested that exosomes could protect full-length viral RNA genomes, and viral proteins from host immune surveillance. The results showed the exosomes assistance in the transmission of viral materials from infected cells to naïve cells leading to active viral replication in the recipient cells. The exosomal viral materials were highly infectious and replicative in recipient cells. However, treatment with GW4869, a commercial inhibitor for neutral Sphingomyelinases that mediated-exosome formation and release, resulted in reduced viral transmission via exosomes and affected the viral replication in recipient cells. These findings suggested a novel and promising therapeutic approach to block exosome-mediated viral transmission from arthropods to humans.
The second study demonstrated mosquito-borne arboviruses used exosomes for dissemination and infection of recipient vertebrate host cells as well. Results showed that ZIKV uses exosomes as mediators of viral transmission, and readily infected these neuronal cells. Neuronal exosomes enclosed both ZIKV viral RNA and proteins inside. Furthermore, the results addressed ZIKV induced both activity and gene expression of neutral Sphingomyelinase (nSMase)-2/SMPD3, a critical molecule regulates the formation and release of exosomes. The silencing of SMPD3 in neuronal cells resulted in decreased viral burden and dissemination via exosomes. Overall, this research elucidated that ZIKV mediated SMPD3 activity in cortical neurons for its infection and transmission through exosomes, perhaps caused severe neuronal death that result in neurological manifestations.
"Exosomes in Transmission and Blocking of Arthropod-Borne Flaviviral Infection and Pathogenesis"
(2020). Doctor of Philosophy (PhD), Dissertation, Biological Sciences, Old Dominion University, DOI: 10.25777/r1f8-7t55