Monoclonal antibody targeting a novel linear epitope on nucleoprotein confers pan-reactivity to influenza A virus.

Nucleoprotein (NP) functions crucially in the replicative cycle of influenza A virus (IAV) via forming the ribonucleoprotein complex together with PB2, PB1, and PA proteins. As its high conservation, NP ranks one of the hot targets for design of universal diagnostic reagents and antiviral drugs for IAV. Here, we report an anti-NP murine monoclonal antibody (mAb) 5F10 prepared from traditional lymphocyte hybridoma technique with the immunogen of a clade 2.3.4.4 H5N1 subtype avian influenza virus. The specificity of mAb 5F10 to NP protein was confirmed by immunofluorescence assay and western blotting, and the mAb 5F10 could be used in immunoprecipitation and immunohistochemistry assays. Importantly, mAb 5F10 possessed broad-spectrum reactivity against H1~H11 subtypes of avian influenza viruses, including various HA clades of H5Nx subtype. In addition, mAb 5F10 also showed good affinity with H1N1 and H3N2 subtype influenza viruses of swine and human origin. Furthermore, the recognized antigenic epitope of mAb 5F10 was identified to consist of the conserved amino acid motif 81EHPSA85 in the second flexible loop region of NP protein through screening the phage display peptide library. Collectively, the mAb 5F10 which recognizes the novel universal NP linear B-cell epitope of IAV with diverse origins and subtypes will be a powerful tool for NP protein-based structural, functional, and mechanistic studies, as well as the development of detection methods and universal vaccines for IAV. KEY POINTS: • A broad-spectrum mAb against various subtypes and sources of IAV was developed • The mAb possessed good reactivity in IFA, western blot, IP, and IHC assays • The mAb targeted a novel conserved linear B-cell epitope involving 81EHPSA85 on NP protein.

Decanoic acid modification enhances the antibacterial activity of PMAP-23RI-Dec.

Antimicrobial peptides are a new type of antibacterial drugs with a broad antibacterial spectrum. Based on our previous research, PMAP-23RI-Dec was designed by modifying the C-terminal of PMAP-23RI with decanoic acid. In this study, we measured the antibacterial activity, stability, hemolysis, and cytotoxicity of PMAP-23RI-Dec. The mechanism of PMAP-23RI-Dec on biofilm and cell membranes were also studied. The results show that PMAP-23RI-Dec exhibited high antibacterial activity and stability, but the hemolytic activity and cytotoxicity of PMAP-23RI-Dec were not enhanced. Moreover, PMAP-23RI-Dec could inhibit biofilm formation at low concentrations, and enhance the killing effect on bacteria by changing the permeability of their cell membranes. Finally, PMAP-23RI-Dec reduced Pseudomonas aeruginosa GIM1.551 and Staphylococcus aureus ATCC25923 damage to organs, and showed superior efficacy against peritonitis. PMAP-23RI-Dec also reduced the scope of abscess and alleviated wound infections. Our research indicated that PMAP-23RI-Dec is a new antibacterial agent with potential clinical application.

Antimicrobial activity of the antibacterial peptide PMAP-36 and its analogues.

The growing problem of antibiotic resistance has attracted people's attention; thus, the search for new antibacterial agents is imminent. In this study, a series of antimicrobial peptides (AMPs) based on the porcine antibacterial peptide PMAP-36 were designed by amino acid substitution to develop peptide analogues as new classes of antimicrobial agents. By extending the α-helix and increasing the positive charge, two peptide analogues, PMAP-36PW and PMAP-36PK, were synthesized. The antibacterial activities of PMAP-36 and its peptide analogues were detected in vitro and in vivo. The results showed that PMAP-36PW and PMAP-36PK had a broadened antibacterial spectrum compared to that of PMAP-36. After the modification, PMAP-36PW and PMAP-36PK exhibited antibacterial activities on swine Escherichia coli K88, while PMAP-36 did not. PMAP-36, PMAP-36PW and PMAP-36PK did not have antibacterial activities against Enterococcus faecium B21. PMAP-36 PW had significant antibacterial activity against seven bacterial strains compared to PMAP-36, and PMAP-36PK had significant antibacterial activity against five bacterial strains compared to PMAP-36. Furthermore, PMAP-36PW exhibited enhanced pH stability. Moreover, in the in vivo efficacy assessment of mice infected with Salmonella choleraesuis C78-1 and Listeria monocytogenes CICC 21533, the peptide analogues exhibited an impressive therapeutic effect by reducing bacterial gene copies and decreasing inflammatory damage in mouse livers and lungs, resulting in a reduction in mouse mortality. This study provides reference data for the design of clinically effective antibacterial peptides.

Enhancing the antibacterial activity of PMAP-37 by increasing its hydrophobicity.

With increasing resistance against conventional antibiotics, there is an urgent need to discover novel substances to replace antibiotics. This need provides an opportunity for the development of antimicrobial peptides (AMPs). To develop new AMPs with effective and safe therapeutic effects, two PMAP-37 analogs called PMAP-37(R13-I) and PMAP-37(K20/27-I) were designed to increase hydrophobicity. Antimicrobial susceptibility testing and animal infection models were used to assess their antibacterial activity. The results showed that the minimal inhibitory concentrations of PMAP-37(R13-I) were lower than those of PMAP-37 for two gram-negative strains. Compared with PMAP-37, PMAP-37(K20/27-I) not only inhibited the growth of most bacterial strains, but also exhibited antibacterial activity against Shigella flexneri CICC21534. In addition, PMAP-37(K20/27-I) exhibited pH and thermal stability. PMAP-37(R13-I) had a therapeutic effect only in mice infected with Salmonella typhimurium SL1344. However, PMAP-37(K20/27-I) exhibited the therapeutic effects, whether in the clinical symptoms, the tissue lesions, or the tissue bacterial loads and the survival rates in mice infected with Staphylococcus aureus ATCC25923 or S. typhimurium SL1344. Therefore, PMAP-37(K20/27-I) can be used as a substitute for antibiotics against infection with bacterial strains.

Comparison of immunoadjuvant activities of four bursal peptides combined with H9N2 avian influenza virus vaccine.

The bursa of Fabricius (BF) is a central humoral immune organ unique to birds. Four bursal peptides (BP-I, BP-II, BP-III, and BP-IV) have been isolated and identified from the BF. In this study, the immunoadjuvant activities of BPs I to IV were examined in mice immunized with H9N2 avian influenza virus (AIV) vaccine. The results suggested that BP-I effectively enhanced cell-mediated immune responses, increased the secretion of Th1 (interferon gamma)- and Th2 (interleukin-4)-type cytokines, and induced an improved cytotoxic T-lymphocyte (CTL) response to the H9N2 virus. BP-II mainly elevated specific antibody production, especially neutralizing antibodies, and increased Th1- and Th2-type cytokine secretion. BP-III had no significant effect on antibody production or cell-mediated immune responses compared to those in the control group. A strong immune response at both the humoral and cellular levels was induced by BP-IV. Furthermore, a virus challenge experiment followed by H&E staining revealed that BP-I and BP-II promoted removal of the virus and conferred protection in mouse lungs. BP-IV significantly reduced viral titers and histopathological changes and contributed to protection against H9N2 AIV challenge in mouse lungs. This study further elucidated the immunoadjuvant activities of BPs I to IV, providing a novel insight into immunoadjuvants for use in vaccine design.

Adjuvant Activity of Bursal Pentapeptide-(III-V) in Mice Immunized with the H9N2 Avian Influenza Vaccine.

BACKGROUND: Bursal Pentapeptide (BPP)-(III-V) are peptides isolated from the Bursa of Fabricius (BF). METHOD: The peptides' adjuvant activities were evaluated in mice immunized with the H9N2 avian influenza vaccine. RESULTS: The results showed that BPP-IV did not promote humoral or cellular immune responses. BPP-III had no effect on antibody production, but increased populations of CD3+ and CD8+ T cells, CTL levels and proliferation activities of splenic T-lymphocytes. BPP-V increased the level of antibodies (HI, IgG and its subtype IgG1) and the cytokine IL-4, as well as the ratio of CD3+ T cells and its subsets CD4+ and CD8+ T cells, BPP-V also increased CTL level and promoted the proliferation activity of T- and B-lymphocyte. Furthermore, in animal challenge experiment, BPP-III and BPP-V reduced viral RNA copies and viral titers, and reduced inflammatory cell infiltration. CONCLUSION: In summary, BPP-IV did not have an effect on specific immune responses, therefore it could not reduce pathological damage in mice lungs; BPP-III provided resistance to the antigen through the cell-mediated immune response; BPP-V enhanced both humoral and cellular immune responses, therefore provided protections against the H9N2 Avian Influenza Virus (AIV). Altogether, BPP-III and BPP-V could be adjuvant candidates for the H9N2 avian influenza vaccine.

Bursal Hexapeptide, A Potential Immunomodulator, Inhibits Tumor Cells Proliferation via p53 Signaling Pathway.

BACKGROUND: The Bursa of Fabricius (BF) is acknowledged as the central humoral immune organ unique to birds. Bursal Hexapeptide (BHP, AGCCNG) is a recently reported bursal-derived bioactive peptide. However, there are few reports of the molecular basis of the mechanism on immune induction and potential antitumor activity of BHP. METHOD: In this paper, Gene microarray analyses demonstrated that BHP regulated expression of 1347 genes, of which 832 were up-regulated and 515 were down-regulated. Differentially expressed genes involved in various pathways were identified, of which 16 pathways were associated with immune responses and tumorigenic processes. RESULT: Specifically, we found that BHP selectively inhibited tumor cell proliferation. Furthermore, BHP enhanced antitumor factor p53 luciferase activity and stimulated expression of p53, p21, and p130 protein. Moreover, we observed that the inhibitory effect of BHP on cell proliferation and premature senescence in a p53-dependent manner. CONCLUSION: Taken together, we uncovered that BHP may be involved in antitumor suppressor via p53 signaling pathway.

Gene cloning, expression and immune adjuvant properties of the recombinant fusion peptide Tα1-BLP on avian influenza inactivate virus vaccine.

Thymosin α1 (Tα1) and bursin-like peptide (BLP) are both immunopotentiators. In order to investigate adjuvant of thymosin α1-bursin-like peptide (Tα1-BLP), we cloned the gene of Tα1-BLP and provided evidence that the gene of Tα1-BLP in a recombinant prokaryotic expression plasmid was successfully expressed in E. coli BL21. To evaluate the immune adjuvant properties of Tα1-BLP, chickens were immunized with Tα1-BLP combined with H9N2 avian influenza whole-inactivated virus (WIV). The titers of HI antibody, antigen-specific antibodies, AIV-neutralizing antibodies, levels of Th1-type cytokines (IFN-γ) and Th2-type cytokines (IL-4) and lymphocyte proliferation responses were determined. What's more, the viral loads and pathologic changes of lung tissue were observed by virus challenge experiment and HE staining to evaluate the immune protection of chickens. We found that Tα1-BLP enhanced HI antibody and antigen-specific IgG antibodies titers, increased the level of AIV-neutralizing antibodies, induced the secretion of Th1- and Th2-type cytokines, and promoted the proliferation of T and B lymphocyte, Furthermore, virus challenge experiment and HE staining confirmed that Tα1-BLP contributed to inhibition replication of the virus from chicken lungs and protected the lungs from damage. Altogether, this study suggested that Tα1-BLP is a novel adjuvant suitable for H9N2 avian influenza vaccine.