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The epidermal growth factor receptor (EGFR) plays a central role in regulating neoplastic processes. The EGFR overexpression in many human epithelial tumors has been correlated with disease progression and bad prognosis. Passive EGFR-directed immunotherapy, but not active specific approaches, has already been introduced in medical oncology practice. Then we wonder if mice immunization with the extracellular domain of murine EGFR (mEGFR-ECD) in adjuvants can circumvent tolerance to self EGFR, by inducing an immune response with consequent antitumor effect. The present study demonstrated that despite mEGFR expression in thymus, strong DTH response was induced by inoculation of mice with the mEGFR-ECD. This self-immunization, using both CFA and very small sized proteoliposomes from Neisseria meningitidis (VSSP), promoted highly specific IgG titers, predominantly IgG2a and IgG2b. Sera from mice immunized with mEGFR-ECD/VSSP not only recognized EGFR1 tumor cell lines by FACS, but also inhibited their in vitro growth, even in the absence of complement. Noteworthy, vaccination of mice with mEGFR-ECD/VSSP stimulated a potent antimetastatic effect in the EGFR1 Lewis lung carcinoma model, while reproductionassociated side effects were absent. Curiously, mice immunized with the human EGFR-ECD (Her1-ECD) in VSSP though induced highly specific IgG antibodies with strong in vitro cytotoxic effect over EGFR1 human cell lines, showed low cross-reactivity with the mEGFR-ECD. These results further encouraged the development of the Her1-ECD/VSSP vaccine project for patients with EGFR1 tumors. ' 2006 Wiley-Liss, Inc.

The development of recombinant COVID-19 vaccines has resulted from scientific progress made at an unprecedented speed during 2020. The recombinant spike glycoprotein monomer, its trimer, and its recombinant receptorbinding domain (RBD) induce a potent anti-RBD neutralizing antibody response in animals. In COVID-19 convalescent sera, there is a good correlation between the antibody response and potent neutralization. In this review, we summarize with a critical view the molecular aspects associated with the interaction of SARS-CoV-2 RBD with its receptor in human cells, the angiotensin-converting enzyme 2 (ACE2), the epitopes involved in the neutralizing activity, and the impact of virus mutations thereof. Recent trends in RBD-based vaccines are analyzed, providing detailed insights into the role of antigen display and multivalence in the immune response of vaccines under development.

BackgroundSOBERANA 02 is a COVID-19 conjugate vaccine candidate based on SARS-CoV-2 recombinant RBD conjugated to tetanus toxoid. SOBERANA Plus antigen is dimeric-RBD. Here we report safety, reactogenicity and immunogenicity from phase I and IIa clinical trials using two-doses SOBERANA 02 (homologous protocol) and three-doses (homologous) or heterologous (with SOBERANA Plus) protocols.MethodWe performed an open-label, monocentric, sequential and adaptive phase I for evaluating safety, reactogenicity and exploring immunogenicity of SOBERANA 02 in two formulations (15 and 25 μg) in 40 subjects, 19–59 years old. Phase IIa was open-label including 100 volunteers 19–80 years, receiving two doses of SOBERANA 02-25 μg. In both trials, half of volunteers received a third dose of SOBERANA 02, half received a heterologous dose of SOBERANA Plus-50 μg. Primary outcomes were safety and reactogenicity. The secondary outcome was vaccine immunogenicity evaluated by anti-RBD IgG ELISA, molecular neutralization test of RBD:hACE2 interaction, live-virus neutralization test and specific T-cells response.ResultsThe most frequent AE was local pain, other AEs had frequencies ≤ 5%. No serious related AEs were reported. Phase IIa confirmed the safety results in 60–80 years subjects. In phase-I SOBERANA 02-25µg elicited higher immune response than SOBERANA 02-15 µg; in consequence, the higher dose progressed to phase IIa. Phase IIa results confirmed the immunogenicity of SOBERANA 02-25 μg even in 60–80 age range. Two doses of SOBERANA02-25 μg elicited an immune response similar to that of the Cuban Convalescent Serum Panel; it was higher after both the homologous and heterologous third doses; the heterologous scheme showing a higher immunological response.ConclusionsSOBERANA 02 was safe and immunogenic in persons aged 19–80 years, eliciting neutralizing antibodies and specific T cell response. Highest immune responses were obtained in the heterologous three doses protocol. Trial registry: https://rpcec.sld.cu/trials/RPCEC00000340 and https://rpcec.sld.cu/trials/RPCEC00000347