Safety and Therapeutic Profile of a GnRH-Based Vaccine Candidate Directed to Prostate Cancer. A 10-Year Follow-Up of Patients Vaccinated With Heberprovac

Influence of Humoral Response Against GnRH, Generated by Immunization with a Therapeutic Vaccine Candidate on the Evolution of Patients with Castration-Sensitive Prostate Adenocarcinoma

BACKGROUND AND AIMS

A gonadotropin-releasing hormone (GnRH)-based therapeutic vaccine candidate against hormone-sensitive prostate cancer has demonstrated its safety and signs of efficacy in phase I/II trials. In this study, we characterized the isotype/subclass profiles of the anti-GnRH humoral response generated by the vaccination and analyzed its association with patients' clinical outcomes.

METHODS

The immunoglobulin isotypes and IgG subclasses of the antibody responses of 34 patients included in a randomized, open, prospective phase I/II clinical trial were characterized. Every patient included in the study had a diagnosis of locally advanced prostate adenocarcinoma at stages 3 and 4 and received immunization with the vaccine candidate. Additionally, serum testosterone and prostate specific antigen (PSA) concentrations, serving as indicators of tumor response, were determined. The type of anti-GnRH antibody response was correlated to the time elapsed until the first biochemical recurrence in patients and the outcome of the disease.

RESULTS

All patients developed strong and prolonged anti-GnRH antibody responses, resulting in a short- to mid-term decrease in serum testosterone and PSA levels. Following immunizations, anti-GnRH antibodies of the IgM/IgG and IgG1/IgG3 subclasses were observed. Following radiotherapy, the humoral response switched to IgG (IgG1/IgG4). Patients who experienced a short-term biochemical relapse were characterized by significantly higher levels of anti-GnRH IgG titers, particularly IgG1 and IgG4 subclasses. These characteristics, along with a high response of specific IgM antibodies at the end of immunizations and the development of anti-GnRH IgA antibody responses following radiotherapy, were observed in patients whose disease progressed, compared to those with controlled disease.

CONCLUSION

The nature of the humoral response against anti-GnRH, induced by vaccination may play a key role in activating additional immunological mechanisms. Collectively, these mechanisms could contribute significantly to the regulation of tumor growth.

Self-adjuvanting cancer nanovaccines

Nanovaccines, a new generation of vaccines that use nanoparticles as carriers and/or adjuvants, have been widely used in the prevention and treatment of various diseases, including cancer. Nanovaccines have sparked considerable interest in cancer therapy due to a variety of advantages, including improved access to lymph nodes (LN), optimal packing and presentation of antigens, and induction of a persistent anti-tumor immune response. As a delivery system for cancer vaccines, various types of nanoparticles have been designed to facilitate the delivery of antigens and adjuvants to lymphoid organs and antigen-presenting cells (APCs). Particularly, some types of nanoparticles are able to confer an immune-enhancing capability and can themselves be utilized for adjuvant-like effect for vaccines, suggesting a direction for a better use of nanomaterials and the optimization of cancer vaccines. However, this role of nanoparticles in vaccines has not been well studied. To further elucidate the role of self-adjuvanting nanovaccines in cancer therapy, we review the mechanisms of antitumor vaccine adjuvants with respect to nanovaccines with self-adjuvanting properties, including enhancing cross-presentation, targeting signaling pathways, biomimicking of the natural invasion process of pathogens, and further unknown mechanisms. We surveyed self-adjuvanting cancer nanovaccines in clinical research and discussed their advantages and challenges. In this review, we classified self-adjuvanting cancer nanovaccines according to the underlying immunomodulatory mechanism, which may provide mechanistic insights into the design of nanovaccines in the future.

RNA-seq coupling two different methods of castration reveals new insights into androgen deficiency-caused degeneration of submaxillary gland in male Sprague Dawley rats

Background

Salivary gland (SMG) degeneration and dysfunction are common symptoms that occur after sex hormone deprivation, but the underlying mechanisms remain largely unknown. Additionally, immunocastration, which causes drop of sex hormones, has been developed as an alternative to surgical castration, however whether it exerts similar effects as surgical castration on the salivary glands is unknown. Through histological and RNA-seq analysis, we assessed changes in morphology and transcriptome of SMG in response to immunocastration (IM) versus surgical castration (bilateral orchiectomy, ORC).

Results

Compared to entire males (EM), ORC caused severe degeneration of SMG in rats, as evidenced by both decreased (P < 0.01) SMG weight and organ index, and by decreased (P < 0.01) quantity of SMG acini and ducts. IM had minimal effects (P > 0.05) on SMG weight and organ index, but it still caused degeneration (P < 0.05) of the acini and ducts. Even though, the quantity of both SMG acini and ducts was much higher (P < 0.001) in IM than in ORC. Functional enrichment analysis of the common regulated genes by ORC/IM revealed disrupted epithelial cell development, angiogenesis, anatomical structure morphogenesis and enhanced cell death are associated with SMG degeneration in deprivation of androgens. Integrated data analysis shown that there existed a selective hyperfunction of SMG ribosome and mitochondrion in ORC but not in IM, which might be associated with more severe degeneration of SMG in ORC than in IM.

Conclusions

Our findings suggested that both surgical castration and immunocastration caused SMG degeneration by disrupting epithelial cell development, angiogenesis, anatomical structure morphogenesis and enhancing cell death. But, surgical castration selectively induced hyperfunction of SMG ribosome and mitochondrion, thus causing more severe degeneration of SMG than immunocastration.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-022-08521-9.

Measurement of total and free prostate specific antigen (PSA) in human serum samples using an ultra-microanalytical system

Prostate specific antigen (PSA) is a serine protease used for the screening of prostate cancer. The total portion of PSA (tPSA) can be found in its free form (fPSA), or bound to other proteins forming a stable complex. A heterogeneous sandwich-type UltraMicro Enzyme-Linked ImmunoSorbent Assay (UMELISA) has been developed for the measurement of tPSA and fPSA in human serum samples. Strips coated with a high affinity monoclonal antibody (MAb) directed against PSA are used as solid phase, to ensure the specificity of the assay. Biotinylated MAbs specific for tPSA and fPSA ensured sensitivity, given the high affinity binding to streptavidin. The assay was completed in 1.5 h, with a measuring range 0.019-20 µg/L (tPSA), and 0.009-20 µg/L (fPSA). The intra- and inter-assay CV were lower than 9%. Recovery percentages were 96-105%. High correlations were found between the values of the UMELISA PSA standards and the International Reference Standards 96/670 (R² = 0.9996) and 96/688 (R² = 0.9989). The assay did not recognize any of the interfering molecules tested. Regression analysis of serum samples showed a good correlation with Roche Elecsys total PSA (n = 631, R² = 0.986, ρc = 0.992), BioMérieux VIDAS TPSA (n = 631, R² = 0.989, ρc = 0.993) and Roche Elecsys free PSA (n = 164, R² = 0.973, ρc = 0.979), all with a relative difference below 15%, and a p < 0.001. A retrospective study of the use of UMELISA PSA in Cuba was carried out. The analytical performance characteristics of UMELISA PSA support its use for the quantification of tPSA and fPSA in human serum samples in a single kit, making it an affordable diagnostic assay available to Cuban Public Health System and developing countries. Between the years 2014-2020, more than 3 million Cuban patients have benefited from the test for free.

Specific humoral response in cancer patients treated with a VEGF-specific active immunotherapy procedure within a compassionate use program

BACKGROUND

CIGB-247 is a cancer therapeutic vaccine that uses as antigen a variant of human vascular endothelial growth factor (VEGF) mixed with the bacterially-derived adjuvant VSSP. CIGB-247 has been already evaluated in two phase I clinical trials (CENTAURO and CENTAURO-2), showing to be safe and immunogenic in advanced cancer patients selected under well-defined and controlled clinical conditions. Surviving patients were submitted to monthly re-immunizations and some of them showed objective clinical benefits. Based on these results, a compassionate use program (CUP) with CIGB-247 was initiated for patients that did not meet the strict entry criteria applied for the CENTAURO and CENTAURO-2 clinical trials, but could potentially benefit from the application of this cancer therapeutic vaccine.

RESULTS

Polyclonal IgM, IgA and IgG antibodies specific for VEGF were detected by ELISA in serum samples from patients vaccinated with 400 μg of antigen combined with 200 μg of VSSP. Polyclonal antibody response showed no cross reactivity for other VEGF family member molecules like VEGF-C and VEGF-D. Serum from immunized individuals was able to block the binding of VEGF to its receptors VEGFR2 and VEGFR1. IgG fraction purified from immune sera shared the aforementioned characteristics and also inhibited the interaction between VEGF and the therapeutic recombinant antibody bevacizumab, an anti-angiogenic drug approved for the treatment of different tumors. No serious adverse events attributable to CIGB-247 have been documented yet in participants of the CIGB-247 CUP. The present paper is a first report of our findings concerning the humoral response and safety characteristics in treated CIGB-247 CUP cancer patients. The study has provided the unique opportunity of not only testing CIGB-247 in a broader clinical spectrum sample of Cuban cancer patients, but also within the context of the day-to-day clinical practice and treatment settings for these diseases in Cuban medical institutions.

CONCLUSIONS

The CIGB-247 CUP has demonstrated that immunization and follow-up of a variety of cancer patients, under day-to-day clinical practice conditions in several Cuban medical institutions, replicate our previous findings in clinical trials: CIGB-247 is safe and immunogenic.

Epitope targeting with self-assembled peptide vaccines

Nanoparticle-based delivery systems are being used to simplify and accelerate new vaccine development. Previously, we described the solid-phase synthesis of a 61-amino acid conjugate vaccine carrier comprising a α-helical domain followed by two universal T cell epitopes. Circular dichroism, analytical centrifugation, and dynamic light scattering indicate that this carrier forms coiled-coil nanoparticles. Here we expand the potential of this carrier by appending B cell epitopes to its amino acid sequence, thereby eliminating the need for traditional conjugation reactions. Peptides containing Tau or amyloid-β epitopes at either terminus assemble into ~20 nm particles and induce antibody responses in outbred mice. Vaccine function was verified in three experiments. The first targeted gonadotropin-releasing hormone, a 10-amino acid neuropeptide that regulates sexual development. Induction of peak antibody titers in male mice stimulated a dramatic loss in fertility and marked testis degeneration. The second experiment generated antibodies to an epitope on the murine IgE heavy chain analogous to human IgE sequence recognized by omalizumab, the first monoclonal antibody approved for the treatment of allergic asthma. Like omalizumab, the anti-IgE antibodies in immunized mice reduced the concentrations of circulating free IgE and prevented IgE-induced anaphylaxis. Finally, a peptide containing the highly conserved Helix A epitope within the influenza hemagglutinin stem domain induced antibodies that successfully protected mice against a lethal H1N1 challenge. These results establish the utility of a new vaccine platform for eliciting prophylactic and therapeutic antibodies to linear and helical B cell epitopes.

Synthetic nanoparticles have the potential to be a simple, efficacious, and customizable platform for vaccine delivery. Christopher H. Clegg and colleagues include B cell epitopes on a self-assembling α-helical peptide nanoparticle carrier in order to elicit robust antibody generation. This novel vaccine platform is validated in vivo to produce physiologically-relevant antibodies in three different settings: an antibody-mediated ‘castration’ approach (anti-gonadotropin-releasing hormone), depletion of IgE (by generation of anti-IgE), and finally production of antibodies to a conserved H1N1 influenza epitope that mediates a protective effect in mice.