Human Papillomavirus (HPV)- An Overview


Human Papillomavirus (HPV) is a group of more than 100 related viruses that infect the skin or mucosal cells of humans. HPV can cause various benign and malignant lesions, such as warts, cervical cancer, and other anogenital and head and neck cancers.

Structure of HPV

HPV is a small, non-enveloped virus with a diameter of about 52-55 nm. It has an icosahedral capsid composed of 72 pentameric capsomers, each containing five molecules of the major capsid protein L1. The capsid also contains a variable number of molecules of the minor capsid protein L2, which are not fully exposed on the surface of the virion .

The capsid encloses a circular, double-stranded DNA genome of about 8 kb in length. The genome is associated with cellular histones to form nucleosomes.

Genome of HPV

The genome of HPV can be divided into three functional regions: the early region (E), the late region (L), and the long control region (LCR). The E region encodes six proteins (E1-E7) that are involved in viral replication, transcription, and transformation. The L region encodes two proteins (L1 and L2) that are involved in viral assembly and encapsidation. The LCR contains the origin of replication and various cis-regulatory elements that control viral gene expression .

The genome organization of HPV is highly conserved among different types, but there is considerable variation in the nucleotide sequence and gene expression patterns. HPV types are classified into low-risk and high-risk groups based on their association with cervical cancer and other malignancies. Low-risk types (such as HPV 6 and 11) mainly cause benign lesions, such as genital warts, while high-risk types (such as HPV 16 and 18) can cause precancerous and cancerous lesions of the cervix and other anogenital and oropharyngeal sites .