Transient expression of HPV16 E7 peptide (aa 44-60) and HPV16 L2 peptide (aa 108-120) on chimeric potyvirus-like particles using Potato virus X-based vector.

The optimized expression of recombinant Potato virus A coat protein (ACP) carrying two different epitopes from Human papillomavirus type 16 (HPV16) was developed. Epitope derived from minor capsid protein L2 was expressed as N-terminal fusion with ACP while an epitope derived from E7 oncoprotein was fused to its C-terminus. The construct was cloned into Potato X potexvirus (PVX) based vector and transiently expressed in plants using Agrobacterium tumefaciens mediated inoculation. To increase the level of expressed protein the transgenic Nicotiana benthamiana plants expressing Potato virus A HC-Pro gene and transgenic Nicotiana tabacum, cv. Petit Havana SR1 carrying Potato virus A P3 protein gene were tested. Synergistic infection of host plants with PVX carrying the construct and Potato virus Y(O) (PVY(O)) increased the expression of L2ACPE7 in N. tabacum and in transgenic N. benthamiana carrying potyviral HC-Pro gene as compared to control plants infected with L2ACPE7 only.

DNA staining with the fluorochromes EtBr, DAPI and YOYO-1 in the comet assay with tobacco plants after treatment with ethyl methanesulphonate, hyperthermia and DNase-I.

We applied the alkaline version of the single-cell gel electrophoresis (comet) assay to roots and leaves of tobacco (Nicotiana tabacum var. xanthi) seedlings or isolated leaf nuclei treated with: (1) the alkylating agent ethyl methanesulphonate, (2) necrotic heat treatments at 50 degrees C, and (3) DNase-I. All three treatments induced a dose-dependent increase in DNA migration, expressed as percentage of tail DNA. A comparison of the fluorochrome DNA dyes ethidium bromide, DAPI and YOYO-1 demonstrated that for the alkaline version of the comet assay in plants, the commonly used fluorescent dye ethidium bromide can be used with the same efficiency as DAPI or YOYO-1.

DNA vaccines based on chimeric potyvirus-like particles carrying HPV16 E7 peptide (aa 44-60).

Vaccine strategies for the treatment of human papillomavirus-induced cervical cancer are based mainly on the human papillomavirus 16 E7 (HPV16 E7) oncoprotein. The immunogenicity of the E7 gene has been enhanced by its fusion to many different genes. Here, we linked a short sequence coding for the E7 peptide (aa 44-60) containing immunodominant epitopes for B and T cells to the 3' end of the gene coding for the whole coat protein (CP) of the poty-virus, potato virus A (PVA), and its deleted form (CPdel) with a short C-terminal deletion of 5 amino acids (LGVKG). CP-E7 and CPdel-E7 fusion proteins, just like CP alone, spontaneously assembled into virus-like particles in both procaryotic and eucaryotic cells. The CP-E7 and CPdel-E7 fusion genes induced slightly stronger E7-specific cytotoxic T-lymphocyte responses than the whole E7 gene, although they were still lower than those elicited by the previously constructed fusion gene, Sig/E7GGG/LAMP-1. The E7- and CP-specific antibody responses were not detected in mice vaccinated with CP-E7 and CPdel-E7 fusion genes. The CP-E7 and CPdel-E7 fusion genes protected mice against the development of tumors induced by TC-1 cells producing the E7 antigen and were also effective in the therapeutic setting, i.e. when the vaccination was performed after tumor cell administration. Their antitumor effect was comparable to those of the whole E7 gene and Sig/E7GGG/LAMP-1 fusion gene. There was no relevant difference between immune responses elicited by CP-E7 and CPdel-E7 DNA vaccination.