Aijun Chen

Enhanced immune response induced by a potential influenza A vaccine based on branched M2e polypeptides linked to tuftsin.

Vaccination is the most effective means for preventing influenza-associated morbidity and mortality. Since the influenza virus mutates frequently, the virus strains for new vaccine production should be changed according to predicted epidemic strains. The extracellular domain of matrix protein 2 (M2e) is 24 amino acids long, which is highly conserved and therefore a good target for the development of a universal vaccine which may protect against a much wider range of influenza A virus strains. However its low antigenicity and immunogenicity, which are related to its small size, poses a big challenge for vaccine development. Multiple antigen peptide system (MAP) is based on an inert core molecule of radially branching lysine dendrites onto which a number of peptide antigens are anchored. Tuftsin is an immuno-stimulant molecule peptide. Here we developed a novel peptide vaccine by connecting a tuftsin to a branched, four-copy M2e. Not only did this increase the molecular mass, but also potentiate the immunogenicity. Two branched peptides, (M2e)4-tuftsin and (M2e)4-G4(tuftsin was replaced with four glycines), and a M2e monomer were synthesized using standard solid-phase methods. In vitro and in vivo studies were performed to compare their antigenicity and immunogenicity. Experiments in BALB/c mice demonstrated that the branched M2e could induce stronger humoral and cellular immune responses than the M2e monomer, and (M2e)4-tuftsin induced stronger humoral and cellular immune response than (M2e)4-G4. After lethal challenge with influenza virus PR8 strain, up to 80% of the animals in the (M2e)4-tuftsin vaccinated group still survived, in contrast to 44% in the (M2e)4-G4 group and 30% in the M2e monomer group. The combination of branched polypeptides and tuftsin in vaccine design is presented here for the first time, and the results show that the new construct is a promising candidate for a universal vaccine against the influenza A virus.

Identification of the ligand-binding domain of human vascular-endothelial-growth-factor receptor Flt-1

The vascular‐endothelial‐growth‐factor (VEGF) receptor Flt‐1 has been shown to be involved in vasculogenesis and angiogenesis. The receptor is characterized by seven immunoglobulin‐like loops within the extracellular domain and the first three N‐terminal immunoglobulin‐like loops are involved in high‐affinity binding of VEGF. The minimal extracellular domains of Flt‐1 to achieve VEGF binding were screened using the yeast two‐hybrid system. The result showed that the binding capacity of loop2‐3 was close to that of loop1‐3. The two truncated mutants consisting of loop2‐3 and loop1‐3 were expressed in the methylotrophic yeast Pichia pastoris at high levels (0.3 mg/litre). The corresponding proteins, named soluble (s)Flt‐1(2‐3) and sFlt‐1(1‐3), were purified. An in vitro biological activity assay showed that the binding capacity of sFlt‐1(2‐3) to human VEGF165 and the inhibiting effect of it on human umbilical‐vein endothelial cell proliferation stimulated by human VEGF165 were close to those of sFlt‐1(1‐3). Animal tests showed that sFlt‐1(2‐3) could significantly inhibit the formation of regenerated blood vessels stimulated by hVEGF165.

Inhibitory effect of small interfering RNA specific for a novel candidate target in PB1 gene of influenza A virus.

Influenza, mainly caused by influenza virus, is becoming one of the major concerns in the world. Limitation in vaccines necessitates the urgent development of new therapeutic options against this virus. In the present study, we designed small interfering RNA (siRNA) targeting overlapping gene of PB1 and PB1-F2 gene of the influenza A virus and investigated its effect against influenza A virus infection. A reduction in virus-associated cell apoptosis was observed in A549 cells treated with this siRNA. Furthermore, its antiviral effect was confirmed by different methods. Also, a marked decrease of virus titer in chicken embryos treated with the siRNA was observed. The findings of this work highlight the potential of this shared region to be an additional therapeutic target for the treatment of influenza virus infection.

[Expression of sTNFR-IgGFc fusion gene in endothelial cell and its application in gene therapy for rheumatoid arthritis].

Tumor necrosis factor alpha (TNFalpha) is a pro-inflammatory cytokine, acting as a regulator of inflammation and immunity. TNFalpha plays a critical role in the pathogenesis of rheumatoid arthritis. Blocking of TNFa activity suppressed inflammatory tissue damage. In present study, the chimeric gene of soluble TNF receptor and IgG Fc fragment (sTNFR-IgG FC) was cloned into the mammalian cell expression vector pStar. When the plamid pStar/sTNFR-IgGFc-GFP was transfected into endothelial cells, a considerable expression of the sTNFR-IgG Fc fusion protein was detected. Moreover, the product in 100microL expression supernatant could completely antagonize the cytolytic effect of 1ng TNFa on L929 cells, even at 1/64 dilution. Then the plasmid was delivered into CIA-induced rheumatoid arthritis mice by tail vein injection. The expression of sTNFR-IgG Fc was detected in liver by RT-PCR. Animals in treatment group showed reduced symptoms of arthritis and more active. This treatment induced decrease of synovial incrassation and prevented the cartilage destruction of the mice RA model. These results show that tail vein injection is an effective way for gene therapy and sTNFR-IgGFc expression plasmid is potential for the treatment of rheumatoid arthritis.

Screening of human vascular endothelial growth factor (VEGF) receptor Flt-1 domain and study on its biological activity.

Four human vascular endothelial growth factor receptor Flt-1 cDNA fragments containing extracellular domain loops 2, 1–2, 2–3 and 1–3 respectively were amplified from human placental cDNA library by PCR and used for screening ligand binding domains by yeast two-hybrid system. The result showed that, not only loop 1–3, but also the smaller fragment loop 2–3 could bind to hVEGF165. Recombinant expression plasmids pPIC9K/Flt-1(1–3) and pPIC9K/Flt-1(2–3) were constructed and transformed toPichia. pastoris host strain GS115, cultured in flasks, and expressed under the induction of 1% methanol. The expressed product existed in supernatant in the form of soluble molecules and contained more than 60% of total protein after being induced for 4d. After being purified by CM-Sepharose FF and Sephacryl S-100 chromatography, its purity reached above 90%. Biological assayin vitro showed that the binding capacity of expressed soluble Flt-1 (2–3) to hVEGF165 and its inhibiting effect on the proliferation of human umbilical veins endothelial cells (HUVEC) stimulated with hVEGF165 were close to those of sFlt-1(1–3). Animal test showed that sFlt-1(2–3) could inhibit the formation of regenerate blood vessels stimulated with hVEGF165 significantly.