Virus Life-cycle 

HPV is specific to infect the basal layer of stratified epithelium. Most HPV infections result in warts rather than cancers. These warts infect the skin, genitalia and mucous membranes.

 Entry of the Virus 

• The HPV virus enters the deep layers of epithelium through micro- wounds or abrasions.

• During repair of the wounds or abrasions, L1 interacts with specific cell surface receptors such alpha-6 beta-4 integrin.

• The virus gains entry via the process of receptor mediated endocytosis, where it is transported in vesicles into the cell. 

• The minor capsid protein, L2 then destroys the vesicle and the viral DNA enters the cell where it is transported to the nucleus. 

Figure-2. Entrance of HPV into host cell

Replication

• As the basal cell begins to divide and differentiate, the viral genome is amplified and more and more copies of the genome are present.

• This virus does not cause viraemia (condition where viruses enter the bloodstream) so no inflammatory response occurs during HPV infection.

• In the outer cell layers, late viral protein L1 and L2 are expressed causing viral assembly to occur.

• These proteins are expressed when the viral genome are highly amplified and exists as many copies in the host cell.  

• As the outer most layer is shed, the new viral particles are released to infect other hosts.