HPV stands for Human Papillomavirus. It is a type of papillomavirus belonging to the Papillomaviridae family. HPV is a spherical DNA virus that can cause proliferation of squamous epithelium in human skin and mucous membranes. It has the ability to immortalize normal cells and exhibits high species specificity and special epitheliotropism. The viral DNA exists in an integrated form within the host cells.

HPV virus types are mainly divided into two categories: low-risk and high-risk. There are about 12 types of low-risk HPV, which do not cause cervical cancer but can lead to various genital warts or mild cervical cell changes. These types include 6, 11, 40, 42, 43, 44, 53, 54, 61, 72, 73, and 81. High-risk HPV types can cause abnormal changes in cervical cells, which, if not treated promptly, may develop into cervical cancer. These types include 16, 18, 31, 33, 35, 39, 45, 51, 52, 56, 58, 59, and 68.

The process from HPV virus infection to lesion development is relatively long. After HPV enters the basal cells of the epithelium through injured areas of the skin or mucous membranes, the viral DNA enters the cell nucleus with the assistance of the capsid protein L2. The early proteins E1 and E2 of HPV begin to express, but at this stage, the copy number is generally low. As the host cells migrate upwards and differentiate, the proteins required for viral DNA replication increase, promoting large-scale replication of the viral genome.

In the terminal stage of viral infection, the early protein E4 and late proteins L1 and L2 begin to express. The new virus particles formed by late proteins and the genome are released from the cells with the help of E4, initiating the next round of infection.

The Life Cycle of HPV Virus in Human Epithelial Cells. 

https://www.std-gov.org/stds/human_papillomavirus_hpv.htm

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Currently, expression systems that have been successfully applied to the exogenous expression of HPV L1 protein include insect cells, S. cerevisiae, P. pastoris, and E. coli. Among these, the yeast expression system can efficiently secrete and express exogenous proteins while also possessing post-translational modification capabilities. This allows the HPV L1 protein to fold correctly and form virus-like particles (VLPs), giving it significant advantages compared to other expression systems.

Yeast Expression Process

LKtime Biotech has established recombinant protein expression platforms for Pichia pastoris and Saccharomyces cerevisiae, capable of providing full-process development services from Gene to IND, as well as early clinical sample preparation, with a development cycle of 9-15 months. The company has built a mature 500L microbial fermentation and purification production line that meets GMP requirements, capable of providing drug substance preparation at scales of 10L-50L and 500L.