Human papillomavirus belongs to the Papovaviridae family. These are small, epitheliotropic, non-enveloped (naked), double-stranded circular DNA viruses. The genome is approximately 8 kbp in size and encased in icosahedral capsid composed of 72 capsomeres (Sameera Mohotti, 2008). Capsomeres are composed of two structural proteins: L1 (57 kD) and L2 (43-53 kD).

These viruses cannot be cultured reliably in a laboratory setting; therefore, HPV diagnostics rely on molecular technologies that detect HPV DNA in cervical/vaginal samples (Curt Malloy, Dec. 2000). HPV act by the expression of two viral oncoproteins, E6 and E7 (Yuping Wu, 2006). Genome of HPV is functionally divided into 3 regions: upstream regulatory region (URR), the early region and the late region. While the URR is involved in viral replication, the early region of the genome includes six open reading frames (ORF’s) or genes named E1, E2, E4, E5, E6 and E7 (encode proteins involved in viral replication, transcription and cellular transformation) and the late region includes two L1 & L2 (encode L1 and L2 structural proteinswhich are necessary for capsid production) (Sameera Mohotti, 2008). HPV Type 41 exclusively contains three Extra ORFs namely, ORF ‘X’, ORF ‘Y’ and ORF ‘Z’.

More than 200 different types of HPV have been identified and classified on the basis of their DNA sequence homology (Sameera Mohotti, 2008) and amongst these, about 40 types are transmitted almost extensively through sexual contact affecting the

genital tract (James L. Klosky, 2009), while remaining strains are responsible for noncancerous warts/lesions on various regions of body. HPV strains are implicated in the development of cervical, vaginal, vulvar, penile, anal and oropharyngeal cancers (Douglas R. Lowy, 2008).

HPV types, based on the clinical prognosis of lesions which they cause, have been classified as “high risk” and others as “low risk” types (Karl Munger, 1997). While the low-risk HPV types (6, 11, 32, 40, 42, 44, 54, 55, 61, 62, 64, 71, 72, 74, 81, 83, 84, 87, 89 and 91) are associated with warts that do not progress toward cancer, the high-risk HPV types (16, 18, 26, 31, 33, 35, 39, 45, 51, 52, 53, 56, 58, 59, 66, 68, 69, 73 and 82) cause intraepithelial lesions that can progress to invasive carcinomas. High-risk HPV types are associated with 99.7% of cervical cancers (Sylvie Beaudenon, 2008) and is the leading cause of cancer related deaths among women in developing countries.