Identification of hepatitis B virus-specific CTL epitopes presented by HLA-A*33:03 in peripheral blood mononuclear cells from patients and transgenic mice.

Cytotoxic T lymphocyte (CTL) epitopes in the HBV protein of hepatitis B virus (HBV) may play a key role in viral control and liver damage. The aim of this study was to identify and study the function of HLA-A(∗)33:03-restricted CTL epitopes in HBV protein of the HBV genotypes B and C, which are epidemic in China. Sixteen HBV peptides were predicated by computational analysis, and synthesized peptides were examined for their affinity to HLA-A(∗)33:03 using a stable cell line. After being analyzed by enzyme-linked immunospot and cytolytic activity assays, as well as the tetramers staining method using peripheral blood mononuclear cells isolated from HBV-infected patients, five peptides (Hbs245-253, HBs335-343, HBc119-127, HBc104-112, and HBp391-399) were chosen to further confirm their HLA_A(∗)33:03 restriction in transgenic mice.

[High level expression of 5-helix protein in HIV gp41 heptad repeat regions and its virus fusion-inhibiting activity].

The artificial 5-helix can inhibit the formation of trimer-of-hairpins structure during the course of HIV-directed membrane fusion and then inhibit human immunodeficiency virus (HIV) infecting target cells. But 5-helix was apt to form inclusion body when expressed directly in prokaryotic cell and was difficult to renature, which causes inconvenience to future study. We found a proper expression vector by simulating protein structure. We simulated its proper conformation in two vectors pGEX-6P-1 and pET44b by homology modeling. The contrast of conformations showed that the energy of salvation of its fusion protein with NusA in vector pET44b was higher than its fusion protein with glutathione-S-transferase (GST) in pGEX-6P-1 and its restriction site lay on the surface of its fusion protein in vector pET44b. 5-helix gene was amplified from pGEX-6P-1-5H by PCR, and was ligated to pET44b to construct recombinant vector pET44b-PSP-5Helix after tested correctly by enzymes digestion. The recombinant vector was transformed into Escherichia coli BL21 (DE3) to express 5-helix protein at different temperatures. Aim protein was purified with Ni column and GST column, and was determined by SDS-PAGE. Then the purified 5 -Helix was used to test the inhibitive activity of pseudo HIV virus infecting GHOST-CXCR4. Results show that its fusion protein with NusA can be effectively soluble expressed and easier to be cleaved, and that the purified 5-helix can efficiently inhibit pseudo HIV virus infecting GHOST-CXCR4 and its IC50 value is (22.77 +/- 5.64) nmol/L, which lay the foundation to further discuss the application in HIV-1 infection.

Hepatitis B virus core antigen epitopes presented by HLA-A2 single-chain trimers induce functional epitope-specific CD8+ T-cell responses in HLA-A2.1/Kb transgenic mice.

The potency of CD8+ cytotoxic T lymphocyte (CTL) responses toward core antigen has been shown to affect the outcomes of hepatitis B virus (HBV) infection. Since single-chain trimers (SCT) composed of peptide epitope beta2-microglobulin (beta2m) and major histocompatibility complex (MHC) class I heavy chain covalently linked together in a single molecule have been shown to stimulate efficient CTL responses, we investigated the properties of human leucocyte antigen (HLA)-A2 SCTs encoding the HBV core antigen (HBcAg) epitopes C(18-27) and C(107-115). Transfection of NIH-3T3 cells with pcDNA3.0-SCT-C(18-27) and SCT-C(107-115) leads to stable presentation of HBcAg epitopes at the cell surface. HLA-A2.1/Kb transgenic mice vaccinated with the SCT constructs, either as a DNA vaccine alone or followed by a boost with recombinant vaccinia virus, were shown to generate HBcAg-specific CTL responses by enzyme-linked immunospot assay (ELISPOT) and in vitro interferon-gamma release experiments. HBcAg-specific CTLs from vaccinated HLA-A2.1/Kb transgenic mice were able to inhibit HBV surface and e antigen expression as indicated by HepG2.2.15 cells. Our data indicate that a DNA vaccine encoding a human HLA-A2 SCT with HBV epitopes can lead to stable, enhanced HBV core antigen presentation, and may be useful for the control of HBV infection in HLA-A2-positive HBV carriers.