Protective cross-reactive epitope on the nonstructural protein NS1 of influenza A virus

In vitro evidence that commercial influenza vaccines are not similar in their ability to activate human T cell responses

We evaluated three commercial trivalent inactivated vaccines (TIVs) from the 2007-2008 season in terms of their ability to elicit in vitro T cell responses. T cell-mediated immunity may offer a more cross-reactive vaccine approach for the prevention of pandemic or epidemic influenza. Human cytotoxic T cell lines demonstrated differences in matrix protein 1 and nucleocapsid protein recognition of autologous target cells. Peripheral blood mononuclear cells stimulated with each of the TIVs showed statistically significant differences between the vaccines in the numbers of IFNgamma producing cells activated. These data suggest that TIV vaccines are not similar in their ability to activate human T cell responses.

Human cytotoxic T lymphocyte responses to live attenuated 17D yellow fever vaccine: identification of HLA-B35-restricted CTL epitopes on nonstructural proteins NS1, NS2b, NS3, and the structural protein E

Yellow fever virus (YFV) is a re-emerging problem despite the existence of an effective live-attenuated vaccine. The induction of YFV-neutralizing antibodies undoubtedly contributes to vaccine efficacy, but T lymphocyte responses to YFV likely play a role in long-term efficacy. We studied the T lymphocyte responses to YFV in four vaccinees. Proliferation and cytolytic responses to YFV were demonstrated in all subjects. We isolated 13 YFV-specific CD8(+) CTL lines that recognized epitopes on the E, NS1, NS2b, and NS3 proteins; eight CTL lines were HLA-B35-restricted. YFV-specific T cell responses were detectable by IFN gamma ELISPOT assays 14 days postvaccination, with T cell frequencies sustained for up to 19 months. To our knowledge, this is the first report of human T lymphocyte responses following YFV vaccination. These results indicate that the live 17D YFV vaccine induced CD8(+) T cell responses directed against at least four different HLA-B35-restricted YFV epitopes.

Immunization with the N-terminal region of the nonstructural protein NS1 promotes survival after challenge with lethal influenza A virus dose

We previously reported that the epitope recognized by an influenza A virus H1, H2, and H3-crossreactive, H-2 Ld-restricted CD8+ cytotoxic T lymphocyte (CTL) is located between amino acids 1 and 40 on the nonstructural protein NS1. In the present experiments, we examined whether immunization with recombinant vaccinia virus which contained genes coding for amino acids 1-40 of NS1 (Vac-10) protected mice from lethal challenge with influenza A virus. Mice immunized with this recombinant virus developed influenza A virus-specific cytotoxic activity but not neutralizing antibodies. Challenge with a lethal dose of influenza A virus demonstrated that the first deaths were delayed by 2 days, and the mortality rate was significantly reduced (p < 0.05) in Vac-10-immunized mice compared with mice immunized with control vaccinia virus. These results suggest that immunization with a single subtype-crossreactive CTL epitope on NS1 can induce protective immunity against lethal influenza A virus infection.

Definition of amino acid residues on the epitope responsible for recognition by influenza A virus H1-specific, H2-specific, and H1- and H2-cross-reactive murine cytotoxic T-lymphocyte clones

We defined the epitopes recognized by three influenza A virus-specific, H-2Kd-restricted CD8(+) cytotoxic T-lymphocyte (CTL) clones: H1-specific clone A-12, H2-specific clone F-4, and H1- and H2-cross-reactive clone B7-B7. The A-12 and B7-B7 clones recognized the same peptide, which comprises amino acids 533 to 541 (IYSTVASSL) of A/PR/8 hemagglutinin (HA). The F-4 and B7-B7 clones both recognized the peptide which comprise amino acids 529 to 537 (IYATVAGSL) of A/Jap HA. Amino acids 533 to 541 of A/PR/8 HA are compatible with amino acids 529 to 537 of A/Jap HA. Amino acid S at positions 3 and 7 was responsible for recognition by H1-specific clone A-12, while amino acid G at position 7 was responsible for recognition by H2-specific clone F-4. Two conserved amino acids, T at position 4 and A at position 6, were responsible for recognition by H1-, and H2-cross-reactive clone B7-B7. These results indicate that a single nine-amino-acid region is recognized by HA-specific CTL clones of three different subtype specificities and that the amino acids responsible for the recognition by the CTL clones are different.

Design of peptide and polypeptide vaccines

Advances have been made in the development of vaccines based on synthetic peptides and polypeptides representing tumor-associated antigens and protective epitopes of viruses and parasites. Advances within the past year include the design of vaccines based on artificial proteins, for example multiantigen peptides, branched polypeptides, fusion and recombinant peptides, as well as single T cell epitopes and tumor antigen peptides. Although peptide vaccines are not in use as yet, their potential is being explored.

Detection of enhanced cytotoxic T lymphocyte response with spleenic dendritic cells enriched by a simple sequential adherence method

Dendritic cells (DC), which are present in many tissues, play a critical role in the initiation of the immune response by presenting antigens to T and B lymphocytes. DC are present in tissues as a minority cell type as compared to other APCs. Although clearly distinguished by morphology and surface markers, dendritic cells are difficult to isolate and multiple step procedures including Percoll/Hypaque or BSA gradient centrifugation have been used. Here we describe a simple method for isolating an enriched population of dendritic cells from mouse spleen by sequential adherence to petri dishes. The purity of dendritic cells enriched thereby was found to be above 70%. The identity of these cells was confirmed to be DC by morphology, presence of surface markers, and their functions, e.g., strong allogeneic MLR reaction and induction of antigen-specific cytotoxic T lymphocyte response.