Intranasal Vaccination of Recombinant Adeno-Associated Virus Encoding Receptor-Binding Domain of Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) Spike Protein Induces Strong Mucosal Immune Responses and Provides Long-Term Protection against SARS-CoV Infection

Abstract

We have previously reported that a subunit protein vaccine based on the receptor-binding domain (RBD) of severe acute respiratory syndrome coronavirus (SARS-CoV) spike protein and a recombinant adeno-associated virus (rAAV)-based RBD (RBD-rAAV) vaccine could induce highly potent neutralizing Ab responses in immunized animals. In this study, systemic, mucosal, and cellular immune responses and long-term protective immunity induced by RBD-rAAV were further characterized in a BALB/c mouse model, with comparison of the i.m. and intranasal (i.n.) routes of administration. Our results demonstrated that: 1) the i.n. vaccination induced a systemic humoral immune response of comparable strength and shorter duration than the i.m. vaccination, but the local humoral immune response was much stronger; 2) the i.n. vaccination elicited stronger systemic and local specific cytotoxic T cell responses than the i.m. vaccination, as evidenced by higher prevalence of IL-2 and/or IFN-γ-producing CD3+/CD8+ T cells in both lungs and spleen; 3) the i.n. vaccination induced similar protection as the i.m. vaccination against SARS-CoV challenge in mice; 4) higher titers of mucosal IgA and serum-neutralizing Ab were associated with lower viral load and less pulmonary pathological damage, while no Ab-mediated disease enhancement effect was observed; and 5) the vaccination could provide long-term protection against SARS-CoV infection. Taken together, our findings suggest that RBD-rAAV can be further developed into a vaccine candidate for prevention of SARS and that i.n. vaccination may be the preferred route of administration due to its ability to induce SARS-CoV-specific systemic and mucosal immune responses and its better safety profile.

Prior Immunization with Severe Acute Respiratory Syndrome (SARS)-Associated Coronavirus (SARS-CoV) Nucleocapsid Protein Causes Severe Pneumonia in Mice Infected with SARS-CoV

“…To date, various types of SARS vaccine, including recombinant vaccines, inactivated vaccines, and DNA vaccine, have been reported (34 -39). There are only a few reports on the effect of a single immunization with recombinant SARS vaccines, namely SARS-CoV S protein-expressing vaccines based on rabies virus (56), vesicular stomatitis virus (39), and adeno-associated virus (57). It is noteworthy that a single i.m.…”

“…immunization with recombinant adeno-associated virus that expresses the receptor-binding domain of S protein conferred long-term protection against SARS-CoV infection (57). In the present study, we also show that a single immunization with m8rVV-S reduces viral load and improves the histopathologic findings in the lungs of BALB/c mice infected with high-titer (1 ϫ 10 5 TCID 50 /body) SARS-CoV, although a relatively low titer of SARS-CoV was used in the previous study conducted by Du et al (57). These results suggest that the systemic immune responses induced by a single immunization with SARS vaccine successfully protect the animal model against intranasal SARS-CoV infection.…”

Putative suppressing effect of IgG Fc-conjugated haemagglutinin (HA) stalk of influenza virus H7N9 on the neutralizing immunogenicity of Fc-conjugated HA head: implication for rational design of HA-based influenza vaccines

“…We have previously demonstrated that the Fc-conjugated RBD-containing H5N1 influenza vaccine induces strong cross-protection (Du et al, 2013c). We have also shown that vaccines based on the RBD of spike proteins of severe acute respiratory syndrome coronavirus and Middle East respiratory syndrome coronavirus elicit highly potent neutralizing antibody responses that protect animals from viral challenges (He et al, 2004;Du et al, 2007Du et al, , 2008Du et al, , 2009Du et al, , 2013aMa et al, 2014;Zhang et al, 2015).…”

“…Collected mouse sera were analysed for specific antibody responses by ELISA (Du et al, 2008). Briefly, 96-well ELISA plates were precoated with His-tagged HA protein of A/Hangzhou/1/2013 (H7N9) expressed in 293T cells overnight at 4 uC and blocked with 2 % non-fat milk for 2 h at 37 uC.…”

Severe acute respiratory syndrome coronavirus nucleocapsid protein does not modulate transcription of the human FGL2 gene

“…The virus was propagated in Vero cells in a biosafety level 3 laboratory as described by Chan et al (2006). Viral RNA copies were determined by quantitative RT-PCR as described by Du et al (2008). HEK293/ACE2 cells stably express the SARS-CoV receptor angiotensin converting enzyme 2 (Narayanan et al, 2008).…”