Polymonoclonal (Not Polyclonal) Antibodies Derived from Convalescent Human B Cell Hybridomas Might Be a Better Therapeutic Option than Single Target Monoclonal Antibodies

Abstract

Both human B cell hybridoma technology and convalescent plasma therapy are promising immunological tools for therapeutic interventions. Here we propose using antibody producing B cells from convalescent SARS-CoV2 patients for developing human B cell hybridomas, and a combination of monoclonal antibodies against multiple immunogenic targets of SARS-CoV-2 spike protein might deliver an antibody cocktail for long-lasting therapeutic targeting.

Human B cell hybridoma technology is an emerging technology that is supposed to help develop human-like therapeutic antibodies. Convalescent plasma therapy is recently been tested for its efficacy to treat COVID 19 patients in various countries. While improvement in patient health has been reported by some groups, recent reports suggest that the level of neutralizing IgG antibodies in the plasma eventually starts decreasing significantly. Thus, while convalescent plasma therapy can potentially be an immediate tool, we postulate that, convalescent blood could be used to isolate the antibody producing plasma cells, develop human B cell hybridomas, and produce strong neutralizing monoclonal antibodies as also shown by Baum et al.¹ The importance of human neutralizing antibodies has also been shown by Ju et al.² In this article we propose that instead of using monoclonal antibodies developed from single source/convalescent blood donor, hybridomas could be generated from multiple sources representing recovered patients who were infected by viruses having spike proteins with different mutations/variation possibilities. Strongly neutralizing monoclonal antibodies representing spike variants could be pooled together and used as a cocktail for better protection.

The first step of virus life cycle is entry. The most important protein of SARS-CoV2 mediating the entry is the spike protein. Spike protein has two domains, S1 and S2. While the scientific community has been mainly focusing on the receptor binding domain that lies in the S1 subunit, S2 also plays a significant role in successful transduction of the virus particle into the host cell by mediating cell fusion. The receptor ACE2 is primarily required for attachment of the virus via its spike protein while a host cell protease TMPRSS2 has been reported to prime the fusion process.

Considering the above known facts, we propose the concept of combining the following components in developing human monoclonal antibody cocktail/s as a therapeutic (Figure 1):

• 1.consideration of multiple convalescent individual sources for B cell isolation (preferably from different geographical locations)
• 2.development of human B cell hybridomas and selection of immunodominant antibodies against receptor binding domain (RBD) of the spike protein
• 3.consideration of selection of monoclonal antibodies against dominantly selected S1 variants (commonly occurring or selected in the isolates)
• 4.consideration of immunodominant monoclonal antibody against the TMPRSS2 cleavage site in the S2 domain of the spike protein

Figure 1.

Multiorigin human monoclonal antibody cocktail therapy. From convalescent blood donors of different origins and who were infected with different commonly circulating spike variants, sera could be collected followed by B cell isolation and human B cell hybridoma culture. B cell clones could be selected for both constant RBD domain and TMPRSS2 cleavage site immunogens as well as the positively selected commonly circulating S1 and S2 antigenic variants. Such monoclonal antibodies could be combined as cocktail and used for therapeutic purposes.

The authors declare no competing financial interest.