HPV16 Induces Filopodia Formation to Promote Viral Entry in Human Keratinocytes

Alyssa Biondo, Fordham University


Human papillomaviruses (HPVs) are common sexually transmitted viruses that contribute to over 5% of all cancers worldwide. HPV infections are attributed to virtually all cases of cervical cancer, with 50% caused by HPV16. Cervical cancer is the most common death in women, with 80% of cases occurring in developing countries that do not have access to cervical tissue screening and vaccines. In the United States, there is a significant reduction in cervical cancer. However, the reported incidences of oropharyngeal and anal cancers have increased three-fold in the last decade. There has been significant progress in understanding the viral lifecycle. Although, the specific mechanisms behind the early stages of viral entry and trafficking are unclear. The purpose of this dissertation was to define the role filopodia play in HPV16 entry of human keratinocytes (HaCaT cells). I determined that the initial binding of viruses to the cell membrane results in filopodia formation. I confirm with filopodia-inducing drugs that these protrusions increase the efficiency of viral binding and entry, as well as overall infection. Inhibition of filopodia by ML-141 resulted in a decrease in viral binding, entry, and infection. The second part of my dissertation addressed the initial signal cascade leading to filopodia formation. I demonstrate that the virus induces Rho GTPase signaling after associating with receptors along these protrusions. Cdc42 activation after virus addition coincided with filopodia induction time points. The depletion and inhibition of Cdc42 activity and its downstream signaling protein, PAK-1, resulted in a significant reduction of filopodia as well as a decrease in viral binding, entry, and infection. Additionally, my data suggest that Cdc42 contributes to cell cycle progression in human keratinocytes. Cdc42-depleted treatments resulted in a greater number of cells in the G1 phase and fewer cells in S or G2/M phase. Furthermore, I also suggest distinct roles for Rac1 and RhoA Rho GTPases in viral entry and trafficking. Taken together, my results help expand the field in understanding the interactions of HPV16 and host cytoskeleton. I present novel findings implicating Rho GTPases’ function in HPV16-induced filopodia formation and entry. There are still gaps in the field in determining what is necessary for virus internalization. Understanding the signaling mechanisms behind HPV16-induced actin rearrangement will allow for a better grasp of the entry mechanism as well as the discovery of effective prophylactic drugs.

Subject Area

Biology|Cellular biology|Molecular biology|Virology

Recommended Citation

Biondo, Alyssa, "HPV16 Induces Filopodia Formation to Promote Viral Entry in Human Keratinocytes" (2023). ETD Collection for Fordham University. AAI30246616.