Presenting the Common Neutralizing Epitope for the L2

Both the Human papillomavirus (HPV) major (L1) and minor (L2) capsid proteins have been well investi-gated as potential vaccine candidates. The L1 protein first oligomerizes into pentamers, and these capsomers assemble into virus-like particles (VLPs) that are highly immunogenic. Here we examine the potential of using HPV type 16 (HPV-16) L1 subunits to display a well-characterized HPV-16 L2 epitope (LVEETSFIDAGAP), which is a common-neutralizing epitope for HPV types 6 and 16, in various regions of the L1 structure. The L2 sequence was introduced by PCR (by replacing 13 codons) into sequences coding for L1 surface loops D-E (ChiC-L2), E-F (ChiA-L2), and an internal loop C-D (ChiH-L2); into the h4 helix (ChiF-L2); and between h4 and -J structural regions (ChiE-L2). The chimeric protein product was characterized using a panel of monoclonal antibodies (MAbs) that bind to conformational and linear epitopes, as well as a polyclonal antiserum raised to the L2 epitope. All five chimeras reacted with the L2 serum. ChiA-L2, ChiE-L2, and ChiF-L2 reacted with all the L1 antibodies, ChiC-L2 did not bind H16:V5 and H16:E70, and ChiH-L2 did not bind any conformation-dependent MAb. The chimeric particles elicited high-titer anti-L1 immune re-sponses in BALB/c mice. Of the five chimeras tested only ChiH-L2 did not elicit an L2 response, while ChiF-L2 elicited the highest L2 response. This study provides support for the use of PV particles as vectors to deliver various epitopes in a number of locations internal to the L1 protein and for the potential of usin