Date of Award

5-22-2019

Document Type

Master's Thesis - Open Access

Degree Name

Master of Science

Department

Microbiology and Immunology

First Advisor

Penghua Wang, Ph.D.

Second Advisor

Mary Petzke, Ph.D.

Third Advisor

Rudra Seedarnee, Ph.D.

Abstract

Zika virus is an enveloped virus with a single-stranded positive-sense RNA genome. The Zika virus is a member of the Flaviviridae family of viruses that was discovered to infect humans in 1952. The Flavivirus envelope is decorated by many copies of two membrane proteins that facilitate viral entry. The virus is primarily transmitted through mosquito bites. Another method by which Zika virus could be transmitted is through sexual contact with Zika infected partners or from an infected pregnant woman to fetus known as congenital transmission. Infected patients suffer from self-limiting febrile illness including headaches, skin rash myalgia, and conjunctivitis. Zika virus has a significant impact on pregnancies, causing developmental defects in fetal brain that leads to infants born with smaller head size, a disorder known as microcephaly. Zika virus has also been linked to the increase of the development of neurological disorder known as Guillain-Barre syndrome. Zika virus has been involved in multiple outbreaks around the world, beginning in 2007 where the Zika virus infected about 5,000 of the people of Yap Island in Micronesia. The following outbreak began between 2013-2014, affecting about 30,000 people in French Polynesia. In 2015-2016, Zika virus outbreak was reported to affect the Americas, where over 30,000 cases and about 4300 microcephaly cases. Upon entry into host cells, Zika virus begins to unpack and release the RNA genome to express the viral proteins as well as to replicate the RNA genome. Studies have revealed that autophagy, which is a cellular mechanism that protects host cells during starvation and pathogenic infections, is associated with Zika replication as it may facilitate the replication of the Zika virus. Here, we investigated the effects of autophagy in the replication of Zika virus using an autophagy inducer, rapamycin. For this study, we used a human trophoblast cell line which is physiologically relevant to congenital transmission of Zika virus. To better understand how autophagy is involved in Zika replication in trophoblast cells, a knockout was generated on one of the autophagy gene known as ATG12. The ATG12 autophagy protein forms a complex with another autophagy protein known as ATG5. PCR analysis revealed that the relative Zika viral load was increased in cells treated with rapamycin when compared to non-rapamycin treated cells. Consistent with the rapamycin treatment results, Zika replication was lower in ATG12-/- than wild type cells. Interestingly, the effect of rapamycin on Zika replication was abolished in ATG12-/- cells. These findings suggest that autophagy facilitates Zika replication. Understanding the effects that autophagy imposes on the replication of the Zika virus could provide therapeutic opportunities through designing drugs that control the autophagy by either entirely blocking the autophagy mechanism or partially in patients who have been infected with Zika virus. Another avenue that would benefit from controlling autophagy is by strategizing delivery of autophagy blockers to pregnant patients to control the severity of developmental disorders in fetuses such as microcephaly.

Download

Share

COinS