Simple method of monoclonal antibody production against mammalian cellular prion protein

Murine monoclonal antibodies against RBD of the SARS-CoV-2 spike protein as useful analytical tools for subunit vaccine development and clinical trials

COVID-19 pandemic poses a serious threat to human health; it has completely disrupted global stability, making vaccine development an important goal to achieve. Monoclonal antibodies play an important role in subunit vaccines strategies. In this work, nine murine MAbs against the RBD of the SARS-CoV-2 spike protein were obtained by hybridoma technology. Characterization of purified antibodies demonstrated that five of them have affinities in the order of 10⁸ L/mol. Six MAbs showed specific recognition of different recombinant RBD-S antigens in solution. Studies of the additivity index of anti-RBD antibodies, by using a novel procedure to determine the additivity cut point, showed recognition of at least five different epitopes. The MAbs CBSSRBD-S.11 and CBSSRBD-S.8 revealed significant neutralizing capacity against SARS-CoV-2 in an ACE2-RBD binding inhibition assay (IC₅₀ = 85.5pM and IC₅₀ = 122.7pM, respectively) and in a virus neutralizing test with intact SARS-CoV-2 (VN₅₀ = 0.552 nM and VN₅₀ = 4.854 nM, respectively) when D614G strain was used to infect Vero cells. Also CBSSRBD-S.11 neutralized the SARS-CoV-2 strains Alpha and Beta: VN₅₀ = 0.707 nM and VN₅₀ = 0.132 nM, respectively. The high affinity CBSSRBD-S.8 and CBSSRBD-S.7 recognized different epitopes, so they are suitable for the development of a sandwich ELISA to quantitate RBD-S recombinant antigens in biomanufacturing processes, as well as in pharmacokinetic studies in clinical and preclinical trials.

Conditional expression of full-length humanized anti-prion protein antibodies in Chinese hamster ovary cells

Because of their high antigen specificity and metabolic stability, genetically engineered human monoclonal antibodies are on the way to becoming one of the most promising medical diagnostics and therapeutics. In order to establish an in vitro system capable of producing such biosimilar antibodies, we used human constant chain sequences to design the novel human antibody expressing vector cassette pMAB-ABX. A bidirectional tetracycline (tet)-controllable promotor was used for harmonized expression of immunoglobulin type G (IgG) heavy and light chains. As an example we used anti-prion protein (anti-PrP) IgGs. Therefore, the variable heavy (V(H)) and light chain (V(L)) sequences of anti-PrP antibodies, previously generated in our laboratory by DNA immunization of prion protein knock-out mice, were isolated from murine hybridoma cell lines and inserted into pMAB-ABX vector. After transfection of Chinese hamster ovary (CHO) cells, a number of stable antibody producing cell clones were selected. One cell line (pMAB-ABX-13F10/3B5) stably expressing the recombinant humanized antibody (rechuAb) 13F10/3B5 was selected for detailed characterization by Western blot, immunofluorescence, and flow cytometric analyses. The full-length recombinant humanized IgG antibody showed a high level of expression in the cytoplasm. In conclusion, the new cell system described here is a suitable tool to produce functional intact full-length humanized IgG antibodies.