LALF32-51 -E7, a HPV-16 therapeutic vaccine candidate, forms protein body-like structures when expressed in Nicotiana benthamiana leaves.

High-risk human papillomaviruses (HPVs) cause cervical cancer, and while there are good prophylactic vaccines on the market, these are ineffective against established infections, creating a clear need for therapeutic vaccines. The HPV E7 protein is one of the essential oncoproteins for the onset and maintenance of malignancy and is therefore an ideal therapeutic vaccine target. We fused the HPV-16 E7 protein to the Limulus polyphemus antilipopolysaccharide factor (LALF32-51 ), a small hydrophobic peptide that can penetrate cell membranes and that has immunomodulatory properties. LALF32-51 -E7 was transiently expressed in Nicotiana benthamiana, and we previously determined that it accumulated better when targeted to chloroplasts compared to being localized in the cytoplasm. Subsequently, we aimed to prove whether LALF32-51 -E7 was indeed associated with the chloroplasts by determining its subcellular localization. The LALF32-51 -E7 gene was fused to one encoding enhanced GFP to generate a LG fusion protein, and localization was determined by confocal laser scanning microscopy and transmission electron microscopy (TEM). The fluorescence observed from chloroplast-targeted LG was distinctively different from that of the cytoplasmic LG. Small spherical structures resembling protein bodies (PBs) were seen that clearly localized with the chloroplasts. Larger but less abundant PB-like structures were also seen for the cytoplasmic LG. PB-like structure formation was confirmed for both LG and LALF32-51 -E7 by TEM. LALF32-51 -E7 was indeed targeted to the chloroplasts by the chloroplast transit peptide used in this study, and it formed aggregated PB-like structures. This study could open a new avenue for the use of LALF32-51 as a PB-inducing peptide.

Identification of a novel antitumor peptide based on the screening of an Ala-library derived from the LALF(32-51) region.

Novel therapeutic peptides are increasingly making their way into clinical application. The cationic and amphipathic properties of certain peptides allow them to cross biological membranes in a non-disruptive way without apparent toxicity increasing drug bioavailability. By modifying the primary structure of the Limulus-derived LALF(32-51) peptide we designed a novel peptide, L-2, with antineoplastic effect and cell-penetrating capacity. Interestingly, L-2 induced cellular cytotoxicity in a variety of tumor cell lines and systemic injection into immunocompetent and nude mice bearing established solid tumor, resulted in substantial regression of the tumor mass and apoptosis. To isolate the gene transcripts specifically regulated by L-2 in tumor cells, we conducted suppressive subtractive hybridization (SSH) analysis and identified a set of genes involved in biological processes relevant to cancer biology. Our findings describe a novel peptide that modifies the gene expression of the tumor cells and exhibits antitumor effect in vivo, indicating that peptide L-2 is a potential candidate for anticancer therapy.

Impact on antitumor response using a new adjuvant preparation as a component of a human papillomavirus type 16 therapeutic vaccine candidate.

Cervical cancer is a global public health problem and human papillomavirus (HPV) 16 accounts for approximately 50% of cases worldwide. Although there are several types of HPV therapeutic vaccines in clinical research, there are currently not approved for use in humans. We developed the fusion protein LALF32-51-E7 (hereafter denominated CIGB550-E7) defined by a cell-penetrating peptide linked to an E7 mutein for the treatment of HPV16-associated tumors. We have demonstrated previously the benefit on antitumor response induced by the immunization with CIGB550-E7 admixed with very small size proteoliposomes (VSSP) adjuvant compared with the adjuvant-free immunization. In this study, we obtained a similar antitumor response in mice immunized with CIGB550-E7 admixed with the new adjuvant sVSSP that does not contain any animal-derived product. Also, the immunization with the above mentioned vaccine preparation induced a cell-mediated immune response. Our results are encouraging for the future clinical trials with the vaccine candidate CIGB550-E7+sVSSP.

Expression optimization of a cell membrane-penetrating human papillomavirus type 16 therapeutic vaccine candidate in Nicotiana benthamiana.

High-risk human papillomaviruses (hr-HPVs) cause cervical cancer, the fourth most common cancer in women worldwide. A HPV-16 candidate therapeutic vaccine, LALF32-51-E7, was developed by fusing a modified E7 protein to a bacterial cell-penetrating peptide (LALF): this elicited both tumour protection and regression in pre-clinical immunization studies. In the current study, we investigated the potential for producing LALF32-51-E7 in a plant expression system by evaluating the effect of subcellular localization and usage of different expression vectors and gene silencing suppressors. The highest expression levels of LALF32-51-E7 were obtained by using a self-replicating plant expression vector and chloroplast targeting, which increased its accumulation by 27-fold compared to cytoplasmic localization. The production and extraction of LALF32-51-E7 was scaled-up and purification optimized by affinity chromatography. If further developed, this platform could potentially allow for the production of a more affordable therapeutic vaccine for HPV-16. This would be extremely relevant in the context of developing countries, where cervical cancer and other HPV-related malignancies are most prevalent, and where the population have limited or no access to preventative vaccines due to their typical high costs.

LALF32-51-E7 therapeutic vaccine induces antitumor immunity against human papillomavirus type 16 E7-expressing murine tumor metastases in the lungs.

One important goal of cancer immunotherapy is to prevent and treat tumor metastasis. We have previously reported the significant antitumor effect induced by the immunization with our human papillomavirus therapeutic protein-based vaccine (LALF32-51-E7) without adjuvant and admixed with clinically relevant adjuvants in the subcutaneous TC-1 tumor challenge model. In the present study, we evaluated the efficacy of the above mentioned vaccine formulations in controlling the hematogenous spread of TC-1 tumor cells using a more tumourigenic clone named TC-1* and other intravenous injection site less stressful than the tail vein. We generated a lung metastasis model by injecting TC-1* cells into the retro-orbital venous sinus and this is the first study describing it. Also, this is the first study that demonstrates the efficacy of the immunization with LALF32-51-E7 without adjuvant and admixed with VSSP or Al(OH)3 in controlling metastatic tumors increasing the survival of the mice. Our TC-1 lung metastasis model can be used to test the efficacy of other immunotherapeutic strategies based on E6/E7 antigens.

Expression, purification and characterization of a recombinant fusion protein based on the human papillomavirus-16 E7 antigen.

A fusion protein comprising a cell penetrating and immunostimulatory peptide corresponding to residues 32 to 51 of the Limulus polyphemus protein linked to human papillomavirus (HPV)-16 E7 antigen (LALF32-51-E7) was expressed in E. coli BL21 (DE3) cells. The recombinant protein in E. coli accounted for approximately 18% of the total cellular protein and purified with a single affinity chromatographic step. Yields of approximately 38 mg purified LALF32-51-E7 per liter of induced culture was obtained with an overall 52% recovery and constitutes a promising setting for the future production and scaling-up. Purified protein was characterized as soluble aggregates with molecular weight larger than 670 kDa, which is considered an important property to increase the immunogenicity of an antigen preparation. The recombinant fusion protein LALF32-51-E7 will be a promising vaccine candidate for the treatment of HPV-16 related malignancies.

A novel fusion protein-based vaccine comprising a cell penetrating and immunostimulatory peptide linked to human papillomavirus (HPV) type 16 E7 antigen generates potent immunologic and anti-tumor responses in mice.

The ultimate success of cancer vaccination is dependent upon the generation of tumor-specific CTLs. In this study, we designed and evaluated a novel fusion protein comprising a cell penetrating and immunostimulatory peptide corresponding to residues 32-51 of the Limulus polyphemus protein (LALF(32-51)) linked to human papillomavirus (HPV) 16 E7 antigen (LALF(32-51)-E7). We demonstrated that LALF(32-51) penetrates the cell membrane and delivers E7 into cells. In a preclinical model of HPV16-induced cervical carcinoma we showed that vaccination with adjuvant-free LALF(32-51)-E7 fusion protein significantly improves the presentation of E7-derived peptides to T-cells in vitro and induces suppression of tumor growth.

Safety and Immunogenicity of a Human Papillomavirus Peptide Vaccine (CIGB-228) in Women with High-Grade Cervical Intraepithelial Neoplasia: First-in-Human, Proof-of-Concept Trial.

Objective. CIGB-228 is a novel therapeutic vaccine consisting of HLA-restricted HPV16 E7 epitope adjuvated with VSSP. This trial was designed to evaluate the toxicity, safety, immunogenicity, HPV clearance, and lesion regression. Methods. Seven women were entered. All were HLA-A2 positive, had biopsy-proven high-grade CIN, histologically positive for HPV16, and beared persistent postbiopsy lesions visible by digital colposcopy. HLA-A2 women with biopsy-proven high-grade CIN, HPV16-positive, and beared persistent postbiopsy lesions visible by digital colposcopy were vaccinated. One weekly injections of CIGB-228 vaccine was given for four weeks. Then, loop electrosurgical excision procedure (LEEP) of the transformation zone was performed. Study subjects were followed for 1 year after LEEP. Results. No toxicity beyond grade 1 was observed during and after the four vaccinations. Five of seven women had complete and partial regression. Cellular immune response was seen in all patients. HPV was cleared in three of the patients with complete response. Conclusion. CIGB-228 vaccination was well tolerated and capable to induce IFNγ-associated T-cell response in women with high-grade CIN. In several patients, lesion regression and HPV clearance were observed.

Immunization with Neisseria meningitidis outer membrane vesicles prevents bacteremia in neonatal mice.

Although vaccines based on outer membrane vesicles (OMV) of Neisseria meningitidis have been developed and administered to children, little is known about the magnitude and quality of the immune response in animal models of early life immunization. We investigated the immunogenicity of meningococcal OMV, and the influence of route and immunization schedule, in neonatal mice. The administration of two intraperitoneal doses of OMV, given at 7 and 14 days after birth, induced a significant antibody response and was highly effective in conferring protection against bacteremia in 21-day-old mice challenged with meningococci. Intranasal immunization was less effective and did not generate a protective immune response. The antibodies elicited by intraperitoneal immunization were cross-reactive with several meningococcal strains and a memory response was demonstrated when mice immunized as neonates were given a booster immunization at 6 weeks of age.