Experimental studies of a vaccine formulation of recombinant human VEGF antigen with aluminum phosphate

Nanovaccines for cancer immunotherapy: Focusing on complex formation between adjuvant and antigen

As an interesting cancer immunotherapy approach, cancer vaccines have been developed to deliver tumor antigens and adjuvants to antigen-presenting cells (APCs). Although the safety and easy production shifted the vaccine designing platforms toward the subunit vaccines, their efficacy is limited due to inefficient vaccine delivery. Nanotechnology-based vaccines, called nanovaccines, address the delivery limitations through co-delivery of antigens and adjuvants into lymphoid organs and APCs and their intracellular release, leading to cross-presentation of antigens and induction of potent anti-tumor immune responses. Although the nanovaccines, either as encapsulating agents or biomimetic nanoparticles, exert the desired anti-tumor activities, there is evidence that the mixing formulation to form nanocomplexes between antigens and adjuvants based on the electrostatic interactions provokes high levels of immune responses owing to Ags' availability and faster release. Here, we summarized the various platforms for developing cancer vaccines and the advantages of using delivery systems. The cancer nanovaccines, including nanoparticle-based and biomimetic-based nanovaccines, are discussed in detail. Finally, we focused on the nanocomplexes formation between antigens and adjuvants as promising cancer nanovaccine platforms.

Murine Mammary Carcinoma Induces Chronic Systemic Inflammation and Immunosuppression in BALB/c Mice

Purpose

Methods

Results

Conclusion

Evaluation of methodologies to determine the effect of specific active immunotherapy on VEGF levels in phase I clinical trial patients with advanced solid tumors

Two phase I clinical trials were conducted to evaluate, among other parameters, the humoral response elicited by a vascular endothelial growth factor (VEGF)-based therapeutic vaccine in cancer patients with advanced solid tumors. VEGF reduction was studied using an indirect methodology named as “Platelet VEGF”. This methodology is based on the estimation of VEGF within platelets by subtracting the plasma VEGF level from the serum level and dividing this by the platelet count, and then this latter expression is additionally corrected by the hematocrit. However, there is broad debate, whether serum or plasma VEGF or platelet-derived VEGF measurements is the most appropriate strategy to study the changes that occur on ligand bioavailability when patients are submitted to a VEGF-based immunotherapy.

The current research is a retrospective study evaluating the changes on VEGF levels in serum and plasma as well as platelet-derived measurements. Changes in VEGF levels were related with the humoral response seen in cancer patients after an active immunotherapy with a VEGF-based vaccine. The present study indicates that “Platelet VEGF” is the most reliable methodology to investigate the effect of VEGF-based immunotherapies on ligand bioavailability. “Platelet VEGF” was associated with those groups of individuals that exhibited the best specific humoral response and the variation of “Platelet VEGF” showed the strongest negative correlation with VEGF-specific IgG antibody levels. This methodology will be very useful for the investigation of this VEGF-based vaccine in phase II clinical trials and could be applied to immunotherapies directed to other growth factors that are actively sequestered by platelets.

Efficacy for lung metastasis induced by the allogeneic bEnd3 vaccine in mice

BACKGROUND

The mouse brain microvascular endothelial cell line bEnd.3 was used to develop a vaccine and its anti-tumor effect on lung metastases was observed in immunized mice.

METHODS

Mouse bEnd.3 cells cultured in-vitro and then fixed with glutaraldehyde was used to immunize mice; mice were challenged with the metastatic cancer cell line U14, and changes in metastatic cancer tissues were observed through hematoxylin and eosin staining. Carboxyfluorescein succinimidyl amino ester (CSFE) and propidium iodide (PI) were used to detect cytotoxic activity of spleen T lymphocytes; the ratio of CD3⁺ and CD8⁺ T-cell sub-sets was determined by flow cytometry. Enzyme-linked immunosorbent assay (ELISA), immunocytochemistry and immunoblot were used to examine the specific response of the antisera of immunized mice.

RESULTS

The number of metastatic nodules in bEnd.3 and human umbilical vein endothelial cell (HUVEC) vaccine groups was less than NIH3T3 vaccine group and phosphate buffered saline (PBS) control group. The bEnd.3-induced and HUVEC-induced cytotoxic T-lymphocytes (CTLs) showed significant lytic activity against bEnd.3 and HUVEC target cells, while the antisera of mice in bEnd.3 and HUVEC vaccine groups showed specific immune responses to membrane proteins and inhibited target cell proliferation in-vitro. Immunoblot results showed specific bands at 180KD and 220KD in bEnd.3 and at 130 kD and 220 kD in HUVEC lysates.

CONCLUSIONS

Allogeneic bEnd.3 vaccine induced an active and specific immune response to tumor vascular endothelial cells that resulted in production of antibodies against the proliferation antigens VEGF-R II, integrin, Endog etc. Immunization with this vaccine inhibited lung metastasis of cervical cancer U14 cells and prolonged the survival of these mice.

Characteristics of the specific humoral response in patients with advanced solid tumors after active immunotherapy with a VEGF vaccine, at different antigen doses and using two distinct adjuvants

Background

CIGB-247, a VSSP-adjuvanted VEGF-based vaccine, was evaluated in a phase I clinical trial in patients with advanced solid tumors (CENTAURO). Vaccination with the maximum dose of antigen showed an excellent safety profile, exhibited the highest immunogenicity and was the only one showing a reduction on platelet VEGF bioavailability. However, this antigen dose level did not achieve a complete seroconversion rate in vaccinated patients. These clinical results led us to the question whether a “reserve” of untapped immune response potential against VEGF could exist in cancer patients. To address this matter, CENTAURO-2 clinical trial was conducted where antigen and VSSP dose scale up were studied, and also incorporated the exploration of aluminum phosphate as adjuvant. These changes were made with the aim to increase immune response against VEGF.

Results

The present study reports the characterization of the humoral response elicited by CIGB-247 from the combining of different antigen doses and adjuvants. Cancer patients were immunologically monitored for approximately 1 year. Vaccination with different CIGB-247 formulations exhibited a very positive safety profile. Cancer patients developed IgM, IgG or IgA antibodies specific to VEGF. Elicited polyclonal antibodies had the ability to block the interaction between VEGF and its receptors, VEGFR1 and VEGFR2. The highest humoral response was detected in patients immunized with 800 μg of antigen + 200 μg of VSSP. Off-protocol long-term vaccination did not produce negative changes in humoral response.

Conclusions

Vaccination with a human VEGF variant molecule as antigen in combination with VSSP or aluminum phosphate is immunogenic. The results of this study could contribute to the investigation of this vaccine therapy in an adequately powered efficacy trial.

Trial registration

Trial registration number: RPCEC00000155. Cuban Public Clinical Trial Registry. Date of registration: June 06, 2013. Available from: http://registroclinico.sld.cu/.

Electronic supplementary material

The online version of this article (doi:10.1186/s12865-017-0222-z) contains supplementary material, which is available to authorized users.

Enhanced Mitogenic Activity of Recombinant Human Vascular Endothelial Growth Factor VEGF121 Expressed in E. coli Origami B (DE3) with Molecular Chaperones

We describe the production of a highly-active mutant VEGF variant, α2-PI1-8-VEGF121, which contains a substrate sequence for factor XIIIa at the aminoterminus designed for incorporation into a fibrin gel. The α2-PI1-8-VEGF121 gene was synthesized, cloned into a pET-32a(+) vector and expressed in Escherichia coli Origami B (DE3) host cells. To increase the protein folding and the solubility, the resulting thioredoxin-α2-PI1-8-VEGF121 fusion protein was co-expressed with recombinant molecular chaperones GroES/EL encoded by independent plasmid pGro7. The fusion protein was purified from the soluble fraction of cytoplasmic proteins using affinity chromatography. After cleavage of the thioredoxin fusion part with thrombin, the target protein was purified by a second round of affinity chromatography. The yield of purified α2-PI1-8-VEGF121 was 1.4 mg per liter of the cell culture. The α2-PI1-8-VEGF121 expressed in this work increased the proliferation of endothelial cells 3.9-8.7 times in comparison with commercially-available recombinant VEGF121. This very high mitogenic activity may be caused by co-expression of the growth factor with molecular chaperones not previously used in VEGF production. At the same time, α2-PI1-8-VEGF121 did not elicit considerable inflammatory activation of human endothelial HUVEC cells and human monocyte-like THP-1 cells.