Abstract
The Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) is the etiological agent for the infectious disease, SARS, which first emerged 10 years ago. SARS-CoV is a zoonotic virus that has crossed the species barriers to infect humans. Bats, which harbour a diverse pool of SARS-like CoVs (SL-CoVs), are believed to be the natural reservoir. The SARS-CoV surface Spike (S) protein is a major antigenic determinant in eliciting neutralizing antibody production during SARS-CoV infection. In our previous work, we showed that a panel of murine monoclonal antibodies (mAbs) that target the S2 subunit of the S protein are capable of neutralizing SARS-CoV infection in vitro (Lip KM et al, J Virol. 2006 Jan; 80(2): 941–50). In this study, we report our findings on the characterization of one of these mAbs, known as 1A9, which binds to the S protein at a novel epitope within the S2 subunit at amino acids 1111–1130. MAb 1A9 is a broadly neutralizing mAb that prevents viral entry mediated by the S proteins of human and civet SARS-CoVs as well as bat SL-CoVs. By generating mutant SARS-CoV that escapes the neutralization by mAb 1A9, the residue D1128 in S was found to be crucial for its interaction with mAb 1A9. S protein containing the substitution of D1128 with alanine (D1128A) exhibited a significant decrease in binding capability to mAb 1A9 compared to wild-type S protein. By using a pseudotyped viral entry assay, it was shown that the D1128A substitution in the escape virus allows it to overcome the viral entry blockage by mAb 1A9. In addition, the D1128A mutation was found to exert no effects on the S protein cell surface expression and incorporation into virion particles, suggesting that the escape virus retains the same viral entry property as the wild-type virus.
Highlights
The Severe Acute Respiratory Syndrome (SARS) first emerged as an infectious disease ten years ago, manifesting itself as a severe form of pneumonia
In vitro neutralization of civet and bat Spseudotyped particle (S-pp) by monoclonal antibodies (mAbs) 1A9 As described in our previous publication, we have a panel of neutralizing mAbs largely grouped into Type I, II, III and IV based on their binding sites on the S protein
In order to evaluate the viral entry properties of the civet SARS-CoV SZ3, bat SARS-like coronaviruses (SL-CoVs) Rp3 and Rf1 strains, the receptor-binding domain (RBD) of S in the civet SARS-CoV SZ3 strain and bat SL-CoV Rp3 and Rf1 strains were replaced with the RBD of S in the human SARS-CoV to create chimeric S proteins (Figure 2A) to allow viral attachment step through the binding of the RBD of S to human angiotensin-converting enzyme 2 (ACE2) receptor
Summary
The Severe Acute Respiratory Syndrome (SARS) first emerged as an infectious disease ten years ago, manifesting itself as a severe form of pneumonia. SARS-CoV is a zoonotic virus that has crossed the species barrier to infect humans. In 2005, the complete sequences of SARS-like coronaviruses (SL-CoVs) of genetic homology of 87– 92% to SARS-CoV were identified from horseshoe bats of the genus Rhinolophus in China [5,6]. These SL-CoVs display significant differences in sequences at the receptor-binding domain (RBD) compared to SARS-CoV and are unable to use the SARS-
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
