Mucosal immunization with surface-displayed severe acute respiratory syndrome coronavirus spike protein on Lactobacillus casei induces neutralizing antibodies in mice.
Induction of mucosal immunity may be important for preventing SARS-CoV infections. For safe and effective delivery of viral antigens to the mucosal immune system, we have developed a novel surface antigen display system for lactic acid bacteria using the poly-gamma-glutamic acid synthetase A protein (PgsA) of Bacillus subtilis as an anchoring matrix. Recombinant fusion proteins comprised of PgsA and the Spike (S) protein segments SA (residues 2 to 114) and SB (residues 264 to 596) were stably expressed in Lactobacillus casei. Surface localization of the fusion protein was verified by cellular fractionation analyses, immunofluorescence microscopy, and flow cytometry. Oral and nasal inoculations of recombinant L. casei into mice resulted in high levels of serum immunoglobulin G (IgG) and mucosal IgA, as demonstrated by enzyme-linked immunosorbent assays using S protein peptides. More importantly, these antibodies exhibited potent neutralizing activities against severe acute respiratory syndrome (SARS) pseudoviruses. Orally immunized mice mounted a greater neutralizing-antibody response than those immunized intranasally. Three new neutralizing epitopes were identified on the S protein using a peptide neutralization interference assay (residues 291 to 308, 520 to 529, and 564 to 581). These results indicate that mucosal immunization with recombinant L. casei expressing SARS-associated coronavirus S protein on its surface provides an effective means for eliciting protective immune response against the virus.
Lee
Jong-Soo
JS
Bioleaders Corporation, Daejeon, Korea.
Poo
Haryoung
H
Han
Dong P
DP
Hong
Seung-Pyo
SP
Kim
Kwang
K
Cho
Michael W
MW
Kim
Eun
E
Sung
Moon-Hee
MH
Kim
Chul-Joong
CJ
D000595:Amino Acid Sequence; D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D018928:Immunity, Mucosal; D007114:Immunization; D007780:Lacticaseibacillus casei / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000276:immunology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008969:Molecular Sequence Data; D009500:Neutralization Tests; D045473:Severe acute respiratory syndrome-related coronavirus / Q000276:immunology*; D064370:Spike Glycoprotein, Coronavirus; D014614:Vaccines, Synthetic / Q000276:immunology*; D014759:Viral Envelope Proteins / Q000276:immunology*; D014765:Viral Vaccines / Q000276:immunology*
D000914:Antibodies, Viral; D008562:Membrane Glycoproteins; D064370:Spike Glycoprotein, Coronavirus; D014614:Vaccines, Synthetic; D014759:Viral Envelope Proteins; D014765:Viral Vaccines; C578557:spike glycoprotein, SARS-CoV; C578553:spike protein, mouse hepatitis virus