Lecture 15 - Human Papillomavirus (introduction)

What are the two main types of HPV based on infection site?

Mucosal and cutaneous.

Which HPV type is associated with genital and respiratory infections?

Mucosal HPV.

What does cutaneous HPV typically cause?

Warts (e.g., plantar, palmar, or skin warts).

How is mucosal HPV transmitted?

Through sexual contact and vertically from mother to child.

How is cutaneous HPV transmitted?

Through direct skin contact or indirectly via surfaces.

When does initial HPV infection typically occur?

Between ages 15–25, soon after sexual debut.

What symmetry does the HPV capsid have and is it enveloped?

Icosahedral capsid and no envelope

What type of genome does HPV have?

Circular dsDNA

What are the two capsid proteins of HPV?

L1 (major) and L2 (minor).

What are the three genomic regions of HPV?

Early (E), Late (L), and the Long Control Region (LCR or URR).

What is the order of gene transcription in HPV?

LCR → E6 → E7 → E1 → E2/E4 → E5 → L2 → L1.

What type of cells does HPV infect?

Squamous epithelial cells, especially basal cells.

How does HPV gain access to basal cells?

Through microabrasions or wounds.

What molecule does HPV initially attach to on the host cell?

Heparan sulfate proteoglycans (HSPGs).

What host enzyme cleaves L1 to assist entry?

Furin.

How is HPV internalized?

Through a macropinocytosis-like process (slow, ~14 hours).

Where does uncoating of HPV occur?

In the acidified endosome.

What type of transport occurs for the viral DNA?

Retrograde transport or movement of DNA to nucleus.

What protein assists retrograde transport of vDNA to the Golgi and how?

L2 by tethering vDNA to host cell chromosome, which localizes the DNA.

When does HPV genome enter the nucleus?

During mitosis, via tethering to host chromosomes.

Which promoter is active in basal epithelial cells?

Early promoter (P early).

Which promoter is active in differentiated cells?

Late promoter (P late).

What allows HPV to produce >20 mRNAs from 8 genes?

Extensive alternative splicing.