Receptor-binding domain of SARS-CoV spike protein induces long-term protective immunity in an animal model

Abstract Development of effective vaccines against severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) is still a priority in prevention of re-emergence of SARS. Our previous studies have shown that the receptor-binding domain (RBD) of SARS-CoV spike (S) protein elicits highly potent neutralizing antibody responses in the immunized animals. But it is unknown whether RBD can also induce protective immunity in an animal model, a key aspect for vaccine development. In this study, BALB/c mice were vaccinated intramuscularly (i.m.) with 10μg of RBD-Fc (RBD fused with human IgG1 Fc) and boosted twice at 3-week intervals and one more time at 12th month. Humoral immune responses of vaccinated mice were investigated for up to 12 months at a 1-month interval and the neutralizing titers of produced antibodies were reported at months 0, 3, 6 and 12 post-vaccination. Mice were challenged with the homologous strain of SARS-CoV 5 days after the last boost, and sacrificed 5 days after the challenge. Mouse lung tissues were collected for detection of viral load, virus replication and histopathological effects. Our results showed that RBD-Fc vaccination induced high titer of S-specific antibodies with long-term and potent SARS-CoV neutralizing activity. Four of five vaccinated mice were protected from subsequent SARS-CoV challenge because no significant virus replication, and no obvious histopathological changes were found in the lung tissues of the vaccinated mice challenged with SARS-CoV. Only one vaccinated mouse had mild alveolar damage in the lung tissues. In contrast, high copies of SARS-CoV RNA and virus replication were detected, and pathological changes were observed in the lung tissues of the control mice. In conclusion, our findings suggest that RBD, which can induce protective antibodies to SARS-CoV, may be further developed as a safe and effective SARS subunit vaccine.

[1]  B. Murphy,et al.  Mucosal immunisation of African green monkeys (Cercopithecus aethiops) with an attenuated parainfluenza virus expressing the SARS coronavirus spike protein for the prevention of SARS , 2004, The Lancet.

[2]  Y. Zhang,et al.  Immunogenicity and protective efficacy in monkeys of purified inactivated Vero-cell SARS vaccine , 2005, Vaccine.

[3]  D. Ho,et al.  Recombinant Modified Vaccinia Virus Ankara Expressing the Spike Glycoprotein of Severe Acute Respiratory Syndrome Coronavirus Induces Protective Neutralizing Antibodies Primarily Targeting the Receptor Binding Region , 2005, Journal of Virology.

[4]  Sung Keun Kang,et al.  Molecular evolution of the SARS coronavirus during the course of the SARS epidemic in China. , 2004, Science.

[5]  G. Kobinger,et al.  Efficacy of severe acute respiratory syndrome vaccine based on a nonhuman primate adenovirus in the presence of immunity against human adenovirus. , 2006, Human gene therapy.

[6]  D. Normile.  Infectious diseases. Mounting lab accidents raise SARS fears. , 2004, Science.

[7]  Shibo Jiang,et al.  SARS vaccine development. , 2005, Emerging infectious diseases.

[8]  R. Proulx,et al.  Immunization with Modified Vaccinia Virus Ankara-Based Recombinant Vaccine against Severe Acute Respiratory Syndrome Is Associated with Enhanced Hepatitis in Ferrets , 2004, Journal of Virology.

[9]  Gary J. Nabel,et al.  Modulation of the Immune Response to the Severe Acute Respiratory Syndrome Spike Glycoprotein by Gene-Based and Inactivated Virus Immunization , 2005, Journal of Virology.

[10]  Y. Guan,et al.  Intranasal immunization with inactivated SARS-CoV (SARS-associated coronavirus) induced local and serum antibodies in mice , 2004, Vaccine.

[11]  Jonathan H. Epstein,et al.  Bats Are Natural Reservoirs of SARS-Like Coronaviruses , 2005, Science.

[12]  H. Schwalbe,et al.  Retroviral Vectors Pseudotyped with Severe Acute Respiratory Syndrome Coronavirus S Protein , 2004, Journal of Virology.

[13]  Ruifu Yang,et al.  Real-Time Polymerase Chain Reaction for Detecting SARS Coronavirus, Beijing, 2003 , 2004, Emerging infectious diseases.

[14]  L. Anderson,et al.  Laboratory Diagnosis of Four Recent Sporadic Cases of Community-acquired SARS, Guangdong Province, China , 2004, Emerging infectious diseases.

[15]  Shibo Jiang,et al.  Inactivated SARS-CoV vaccine elicits high titers of spike protein-specific antibodies that block receptor binding and virus entry , 2004, Biochemical and Biophysical Research Communications.

[16]  Gary J. Nabel,et al.  A DNA vaccine induces SARS coronavirus neutralization and protective immunity in mice , 2004, Nature.

[17]  Chengsheng Zhang,et al.  Receptor and viral determinants of SARS-coronavirus adaptation to human ACE2 , 2005, The EMBO journal.

[18]  Z. Rao,et al.  Protective humoral responses to severe acute respiratory syndrome-associated coronavirus: implications for the design of an effective protein-based vaccine. , 2004, The Journal of general virology.

[19]  Shibo Jiang,et al.  Receptor-binding domain of SARS-CoV spike protein induces highly potent neutralizing antibodies: implication for developing subunit vaccine , 2004, Biochemical and Biophysical Research Communications.

[20]  Jingxin Cao,et al.  Evaluation of modified vaccinia virus Ankara based recombinant SARS vaccine in ferrets , 2005, Vaccine.

[21]  A. Roberts,et al.  A single immunization with a rhabdovirus-based vector expressing severe acute respiratory syndrome coronavirus (SARS-CoV) S protein results in the production of high levels of SARS-CoV-neutralizing antibodies. , 2005, The Journal of general virology.

[22]  Kwanyee Leung,et al.  Evasion of antibody neutralization in emerging severe acute respiratory syndrome coronaviruses. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[23]  K. Yuen,et al.  Recombinant adeno-associated virus expressing the receptor-binding domain of severe acute respiratory syndrome coronavirus S protein elicits neutralizing antibodies: Implication for developing SARS vaccines , 2006, Virology.

[24]  Zhimin Zhou,et al.  A recombinant baculovirus-expressed S glycoprotein vaccine elicits high titers of SARS-associated coronavirus (SARS-CoV) neutralizing antibodies in mice , 2006, Vaccine.

[25]  B. Moss,et al.  Neutralizing antibody and protective immunity to SARS coronavirus infection of mice induced by a soluble recombinant polypeptide containing an N-terminal segment of the spike glycoprotein , 2005, Virology.

[26]  G. Simmons,et al.  Characterization of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) spike glycoprotein-mediated viral entry , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[27]  Kwok-Hung Chan,et al.  Severe acute respiratory syndrome coronavirus-like virus in Chinese horseshoe bats. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[28]  Shibo Jiang,et al.  Antigenic and Immunogenic Characterization of Recombinant Baculovirus-Expressed Severe Acute Respiratory Syndrome Coronavirus Spike Protein: Implication for Vaccine Design , 2006, Journal of Virology.

[29]  D. Normile.  Mounting Lab Accidents Raise SARS Fears , 2004, Science.

[30]  Guo-Ping Zhao,et al.  Cross-host evolution of severe acute respiratory syndrome coronavirus in palm civet and human. , 2005, Proceedings of the National Academy of Sciences of the United States of America.

[31]  John L. Sullivan,et al.  Angiotensin-converting enzyme 2 is a functional receptor for the SARS coronavirus , 2003, Nature.

[32]  Shibo Jiang,et al.  Identification of Immunodominant Sites on the Spike Protein of Severe Acute Respiratory Syndrome (SARS) Coronavirus: Implication for Developing SARS Diagnostics and Vaccines , 2004, The Journal of Immunology.

[33]  B. Moss,et al.  Severe acute respiratory syndrome coronavirus spike protein expressed by attenuated vaccinia virus protectively immunizes mice. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[34]  K. Subbarao,et al.  Long-term protection from SARS coronavirus infection conferred by a single immunization with an attenuated VSV-based vaccine , 2005, Virology.

[35]  Christian Drosten,et al.  Characterization of a Novel Coronavirus Associated with Severe Acute Respiratory Syndrome , 2003, Science.

[36]  X. L. Liu,et al.  Isolation and Characterization of Viruses Related to the SARS Coronavirus from Animals in Southern China , 2003, Science.

[37]  Shibo Jiang,et al.  Cross-Neutralization of Human and Palm Civet Severe Acute Respiratory Syndrome Coronaviruses by Antibodies Targeting the Receptor-Binding Domain of Spike Protein , 2006, The Journal of Immunology.

[38]  Obi L. Griffith,et al.  The Genome Sequence of the SARS-Associated Coronavirus , 2003, Science.

[39]  M. Reiter,et al.  A double-inactivated whole virus candidate SARS coronavirus vaccine stimulates neutralising and protective antibody responses , 2005, Vaccine.

[40]  Shibo Jiang,et al.  Vaccine design for severe acute respiratory syndrome coronavirus. , 2005, Viral immunology.

[41]  Shibo Jiang,et al.  Receptor-Binding Domain of Severe Acute Respiratory Syndrome Coronavirus Spike Protein Contains Multiple Conformation-Dependent Epitopes that Induce Highly Potent Neutralizing Antibodies , 2005, The Journal of Immunology.

[42]  Baoan Yang,et al.  Identification of a critical neutralization determinant of severe acute respiratory syndrome (SARS)-associated coronavirus: importance for designing SARS vaccines , 2005, Virology.

[43]  Guoping Zhao,et al.  Molecular Evolution of the SARS Coronavirus During the Course of the SARS Epidemic in China , 2004, Science.