The major capsid protein Ll of human papillornavirus (HPV) contains the immunodominant neutralization epitopes of the virus and can auto-assembles to form virus-like particles (VLPs). Therefore, HPV Ll capsid proteins have been well investigated as potential vaccine candidates. To express large quantities of human papillornavirus type 16 (HPV-16) Ll in Escherichia coli (E coli), The HPV-16 Ll gene was cloned into pGEX-4T-1, resulting in only low expression levels of HPV-16 L1 in E. coli. The first 129 nucleotides of the 5' end of the Ll gene, which contains the major inhibitory RNA element, were then deleted. The deletion RNA was efficiently translated, resulting in about 2-fold higher Ll accumulation in E. coli. The N-terminal amino-acid deletion did not affect the ability of Ll to auto-assemble in E. coli and form small VLPs. (c) 2007 Elsevier Inc. All rights reserved.