title: The nucleocapsid protein of Rift Valley fever virus is a potent human CD8+ T cell antigen and elicits memory responses.
abstract: There is no licensed human vaccine currently available for Rift Valley Fever Virus (RVFV), a Category A high priority pathogen and a serious zoonotic threat. While neutralizing antibodies targeting the viral glycoproteins are protective, they appear late in the course of infection, and may not be induced in time to prevent a natural or bioterrorism-induced outbreak. Here we examined the immunogenicity of RVFV nucleocapsid (N) protein as a CD8(+) T cell antigen with the potential for inducing rapid protection after vaccination. HLA-A*0201 (A2)-restricted epitopic determinants were identified with N-specific CD8(+) T cells from eight healthy donors that were primed with dendritic cells transduced to express N, and subsequently expanded in vitro by weekly re-stimulations with monocytes pulsed with 59 15mer overlapping peptides (OLPs) across N. Two immunodominant epitopes, VT9 (VLSEWLPVT, N(121-129)) and IL9 (ILDAHSLYL, N165-173), were defined. VT9- and IL9-specific CD8(+) T cells identified by tetramer staining were cytotoxic and polyfunctional, characteristics deemed important for viral control in vivo. These peptides induced specific CD8(+) T cell responses in A2-transgenic mice, and more importantly, potent N-specific CD8(+) T cell reactivities, including VT9- and IL9-specific ones, were mounted by mice after a booster vaccination with the live attenuated RVF MP-12. Our data suggest that the RVFV N protein is a potent human T cell immunogen capable of eliciting broad, immunodominant CD8(+) T cell responses that are potentially protective. Understanding the immune responses to the nucleocapsid is central to the design of an effective RVFV vaccine irrespective of whether this viral protein is effective as a stand-alone immunogen or only in combination with other RVFV antigens.
authors.affiliation: Department of Biological Science and Border Biomedical Research Center, The University of Texas at El Paso, El Paso, Texas, United States of America.
authors.forename: Weidong
authors.initials: W
authors.lastname: Xu
authors.forename: Douglas M
authors.initials: DM
authors.lastname: Watts
authors.forename: Margaret C
authors.initials: MC
authors.lastname: Costanzo
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Tang
authors.forename: Leon A
authors.initials: LA
authors.lastname: Venegas
authors.forename: Feng
authors.initials: F
authors.lastname: Jiao
authors.forename: Alessandro
authors.initials: A
authors.lastname: Sette
authors.forename: John
authors.initials: J
authors.lastname: Sidney
authors.forename: Andrew K
authors.initials: AK
authors.lastname: Sewell
authors.forename: Linda
authors.initials: L
authors.lastname: Wooldridge
authors.forename: Shinji
authors.initials: S
authors.lastname: Makino
authors.forename: John C
authors.initials: JC
authors.lastname: Morrill
authors.forename: Clarence J
authors.initials: CJ
authors.lastname: Peters
authors.forename: June
authors.initials: J
authors.lastname: Kan-Mitchell
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000956:Antigens, Viral / Q000276:immunology*; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology*; D003713:Dendritic Cells / Q000276:immunology; D058501:Enzyme-Linked Immunospot Assay; D018984:Epitopes, T-Lymphocyte / Q000235:genetics; D005434:Flow Cytometry; D005822:Genetic Vectors; D015789:HLA-A2 Antigen / Q000276:immunology; D006801:Humans; D007156:Immunologic Memory / Q000276:immunology*; D016086:Lentivirus; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D008969:Molecular Sequence Data; D019590:Nucleocapsid Proteins / Q000276:immunology*; D012296:Rift Valley fever virus / Q000235:genetics*; D014765:Viral Vaccines / Q000276:immunology*
chemical_list: D000956:Antigens, Viral; D018984:Epitopes, T-Lymphocyte; C435939:HLA-A*02:01 antigen; D015789:HLA-A2 Antigen; D019590:Nucleocapsid Proteins; D014765:Viral Vaccines