In novel potent antibody and vaccine development, identifying the most sensitive amino acid fragment of the target antigen is very critical issue. Taking the advantage for the new study similarity in nucleic acid sequence and host ACE2 receptors in SARS-CoV-1 and SARS-CoV-2 is important. An impressive study was reported that S1 subunit protein amino acid residue from 318-510 bounds ACE2 host very efficiently than the full length S1 daman (amino acid residue 12-672).⁶⁰ Furthermore, amino acid residue 327-510 and 318-490 did not detectably bind to detect ACE2. Interestingly, the major reason was investigated as the reason that about 7 amino acid cysteine which are 5 of them essential to ACE2 expression and the aspartic acid, glutamic acid amino acid which also have an important association with ACE2 are found within 318-510 amino acid (aa) residue domains.⁶⁰

Figure 4. S1 subunit spiked protein SARS-CoV-1 amino acid residue domain. The aa represents for: amino acid residue, N: N- Terminal, C: C-Terminal.

In the same fashion, recently the receptor-biding domain (RBM) in the S-protein COVID-19 apparently amino acid residue (Gln493) showed favorable interactions with human ACE2 and the binding sites of S protein COVID-19 to human ACE2 were identified as residues 455, 486, 493, 501, and 505.³⁹ So that, taking those critical scientific evidence could lead to produce robust neutralizing antibody and vaccine against COVID-19.

Surprisingly, from the recent study reported that, the monoclonal antibody CR3022 only showed a cross reactivity of SARS-Cov-1 with spiked protein of COVID-19. However, m396 and CR3014 failed to bind the RBD of COVID-19. ⁴⁸ This CR3022 is developed from convalescent serum SARS-CoV-1 patient B lymphocyte single chain variable antibody fragment (scFv) phage display library.⁵⁰ This antibody is targeted a C-terminal of sensitive amino acid residue from 318-510 of spiked protein RBD SARA-CoV-1 Moreover, this antibody is targeted spiked protein of RBD. ⁴⁸ Similar study was reported only ACE2-non-blocking SARS-CoV-1 RBD antibodies was shown a positive cross reactivity with COVID-19. ¹⁸ Thus, we suggest that further more studies and CR3022 may have the therapeutic and diagnostic potential alone or in combination with other neutralizing antibodies, for the prevention and treatment of COVID-19 infections. Production of novel antibody and vaccine based on those very important scientific backgrounds is an urgent needed. ⁴⁸

Plasma serum containing polyclonal antibody from fully recovered patient is as an immediate optional therapy against COVID-19 to slowdown spread and save live.²⁴ However, getting enough recovered volunteer donors and transfusion compatibility remind as big challenges. In order to overcome this draw back, improved method for EBV (Epstein–Barr virus) immortalization transformation of human B cells which secrets a neutralization antibody have been developed.^61,62 interestingly, specific monoclonal antibody isolated from EBV transformed B cell of patients recovered from severe acute respiratory syndrome coronavirus (SARS-CoV-1) infection resulted in vitro neutralizing efficiency from 10–8M to 10–11M.⁶³ Surprisingly, monoclonal antibody CR3022 which was developed from B cell SARS-CoV-1 recovered patients showed a dramatic cross reactivity binding potential for COVID-19.⁴⁸ Blood group O individuals was shown very low risk of infection against COVID-19. Moreover, convalescent plasma taking from O blood group recovered individuals results better efficacy.^12,13,22 Taking all together, isolation of specific monoclonal antibody from EBV transformed B lymphocyte of fully recover ABO blood group typically O could be an effective approach at this very critical emergency time to overcome COVID-19 pandemic.