Yinghua Tang

Inactivated vaccine with adjuvants consisting of pattern recognition receptor agonists confers protection against avian influenza viruses in chickens

Use of adjuvant containing pathogen pattern recognition receptor agonists is one of the effective strategies to enhance the efficacy of licensed vaccines. In this study, we investigated the efficacy of avian influenza vaccines containing an adjuvant (CVCVA5) which was composed of polyriboinosinic polyribocytidylic, resiquimod, imiquimod, muramyl dipeptide and levomisole. Avian influenza vaccines adjuvanted with CVCVA5 were found to induce significantly higher titers of hemagglutiniton inhibition antibodies (P≤0.01) than those of commercial vaccines at 2-, 3- and 4-week post vaccination in both specific pathogen free (SPF) chickens and field application. Furthermore, virus shedding was reduced in SPF chickens immunized with H9-CVCVA5 vaccine after H9 subtype heterologous virus challenge. The ratios of both CD3(+)CD4(+) and CD3(+)CD8(+) lymphocytes were slowly elevated in chickens immunized with H9-CVCVA5 vaccine. Lymphocytes adoptive transfer study indicates that CD8(+) T lymphocyte subpopulation might have contributed to improved protection against heterologous virus challenge. Results of this study suggest that the adjuvant CVCVA5 was capable of enhancing the potency of existing avian influenza vaccines by increasing humoral and cellular immune response.

Chimaeric VP2 proteins from infectious bursal disease virus containing the N-terminal M2e of H9 subtype avian influenza virus induce neutralizing antibody responses to both viruses

Subunit vaccines capable of inducing antibody against both infectious bursal disease virus (IBDV) and H9 subtype avian influenza virus (AIV) were developed. The VP2 protein of IBDV was used as a cargo protein to display a 12-amino-acid immunodominant epitope derived from the N-terminal M2 extracellular domain (nM2e) of the H9 subtype AIV. Two chimaeric proteins were constructed by insertion of one copy of the nM2e into the PBC region (VP2BCnM2e(H9)) or by fusing four copies of nM2e to the carboxyl terminal (VP2-4nM2e(H9)) of VP2. Genes that encoded the VP2 chimaeras were subsequently cloned into a baculovirus vector and expressed in Spodoptera frugiperda cells. The recombinant proteins were used to vaccinate chickens at day 0 and again after 4 weeks. Blood was collected at 2-week intervals after primary and secondary vaccination to detect the antibody titre against VP2 or the nM2e via indirect enzyme-linked immunosorbent assay. Virus neutralization tests were also performed to measure anti-IBDV or anti-H9 AIV neutralizing antibodies in chick embryo fibroblasts. Oropharyngeal and cloacal swabs were collected 3, 5 and 7 days post H9 subtype AIV infection for virus isolation. Vaccination with VP2-4nM2e(H9) induced higher levels of antibody responses against IBDV or H9 subtype AIV, and provided better protection against an IBDV virulent challenge compared with vaccination with VP2BCnM2e(H9) vaccine, the wild-type VP2 subunit vaccine or the IBDV subunit commercial vaccines. Both chimaeric VP2 vaccines showed poor efficacy in inhibiting H9 virus replication post challenge. In summary, chimaeric proteins that contain the nM2e epitope were able to induce both IBDV and H9 subtype AIV-neutralizing antibody responses.

Immunopotentiators Improve the Efficacy of Oil-Emulsion-Inactivated Avian Influenza Vaccine in Chickens, Ducks and Geese.

Combination of CVCVA5 adjuvant and commercial avian influenza (AI) vaccine has been previously demonstrated to provide good protection against different AI viruses in chickens. In this study, we further investigated the protective immunity of CVCVA5-adjuvanted oil-emulsion inactivated AI vaccine in chickens, ducks and geese. Compared to the commercial H5 inactivated vaccine, the H5-CVCVA5 vaccine induced significantly higher titers of hemaglutinin inhibitory antibodies in three lines of broiler chickens and ducks, elongated the antibody persistence periods in geese, elevated the levels of cross serum neutralization antibody against different clade and subclade H5 AI viruses in chicken embryos. High levels of mucosal antibody were detected in chickens injected with the H5 or H9-CVCA5 vaccine. Furthermore, cellular immune response was markedly improved in terms of increasing the serum levels of cytokine interferon-γ and interleukine 4, promoting proliferation of splenocytes and upregulating cytotoxicity activity in both H5- and H9-CVCVA5 vaccinated chickens. Together, these results provide evidence that AI vaccines supplemented with CVCVA5 adjuvant is a promising approach for overcoming the limitation of vaccine strain specificity of protection.

Antigen-Sparing and Enhanced Efficacy of Multivalent Vaccines Adjuvanted with Immunopotentiators in Chickens

We previously described that immunopotentiators, CVCVA5, increased the efficacy of H5 and H9 subtype avian influenza vaccines in chickens, ducks, and geese. In this study, we further investigated the effects of the CVCVA5 for improving the efficacy of other univalent or multivalent inactivated vaccines. The immune response administrated with half-dose of monovalent vaccine plus CVCVA5 were higher than those of one dose of monovalent vaccine without immunopotentiators as measured by levels of antibodies from serum, tears and bronchoalveolar lavage fluids, and cytokines of IFNγ and IL-4 from serum. Vaccines included the univalent vaccine of Newcastle Disease virus (ND), Egg Drop Syndrome virus (EDS), Infectious Bronchitis virus (IB), and Infectious Bursal Disease virus (IBD). The CVCVA5 also improved the immune response of both ND and IBD vaccines with less dosage. The sterile protective immunity was monitored with one- or a half-dose of adjuvanted ND vaccine or one dose of adjuvanted IBD vaccine, respectively. The improved immune efficacy was observed in a half-dose of adjuvanted bivalent vaccines compared to one dose of vaccines without CVCVA5 as measured by the antibody levels, including bivalent vaccine of ND-H9, ND-IB, and ND-IBD. The CVCVA5 also boosted the immune efficacy of the tetravalent vaccine (ND-IB-EDS-H9). A half-dose of adjuvanted commercial vaccine or 75% antigen-sparing adjuvanted vaccine elicited similar antibody levels to those of one dose non-adjuvanted commercial vaccines. The CVCVA5 improved the effect of a booster vaccination as measured by the antibody levels against H5 or H9 virus antigens, in which chickens primed with the adjuvanted ND-IB vaccines given a booster with H5–H9 bivalent vaccines without CVCVA5 using 5-day intervals. The inflammatory response may contribute to these additional effects by increasing the levels of IFNγ and IL-4 after the injection of the adjuvanted ND-IB vaccines. Results indicated that the CVCVA5 improved the serum and mucosal antibody levels, cytokine levels of the chickens given the univalent vaccine, and also improved serum antibody titers in bivalent and tetravalent vaccines. This has a potential as an improve vaccine.

Single Dose of Consensus Hemagglutinin-Based Virus-Like Particles Vaccine Protects Chickens against Divergent H5 Subtype Influenza Viruses

The H5 subtype highly pathogenic avian influenza (HPAI) virus is one of the greatest threats to global poultry industry. To develop broadly protective H5 subunit vaccine, a recombinant consensus HA sequence (rHA) was constructed and expressed in virus-like particles (rHA VLPs) in the baculovirus-insect cell system. The efficacy of the rHA VLPs vaccine with or without immunopotentiator (CVCVA5) was assessed in chickens. Compared to the commercial Re6 or Re6-CVCVA5 vaccines, single dose immunization of chickens with rHA VLPs or rHA-CVCVA5 vaccines induced higher levels of serum hemagglutinin inhibition titers and neutralization titers, mucosal antibodies, IFN-γ and IL-4 cytokines in sera, and cytotoxic T lymphocyte responses. The rHA VLPs vaccine was superior to the commercial Re6 vaccine in conferring cross-protection against different clades of H5 subtype viruses. This study reports that H5 subtype consensus HA VLP single dose vaccination provides broad protection against HPAI virus in chickens.

H9 subtype influenza vaccine in MDCK single-cell suspension culture with stable expression of TMPRSS2: Generation and efficacy evaluation

Vaccination is the most effective way to protect chickens from avian influenza pandemics. Mammalian cells, especially MDCK cells, are being investigated as a good alternative to the embryonated chicken eggs for avian influenza vaccine production. In this work, we developed a new MDCK cell line, which has two main features: single‐cell suspension growth and stable expression of human TMPRSS2 protein (transmembrane protease serine S1 member 2) anchored on cells membrane, named MDCK‐Sus‐TMPRSS2. Reverse‐transcription polymerase chain reaction, western blot analysis and indirect immunofluorescence assay were employed to detect the expression of TMPRSS2 in the MDCK‐Sus‐TMPRSS2 cells. Then, H9 subtype avian influenza virus, NJ02/01 strain, was adapted in MDCK‐Sus‐TMPRSS2 cells with serial blind passages and propagated in stirred bioreactor with 9.5 log2/25 μL hemagglutination titers for inactivated avian influenza vaccine production without addition of exogenous trypsin. The MDCK‐Sus‐TMPRSS2 cell‐derived H9 subtype avian influenza vaccine could induce high titers of hemagglutiniton inhibition antibodies in specific pathogen‐free chickens and protect chickens against heterologous H9 subtype influenza virus challenge, showing lower virus shedding rate and sickness rate than in the egg‐derived vaccines group. High titers of H9 subtype‐specific antibodies above 6 log2 were maintained for 6 months in commercial chickens vaccinated by the MDCK‐Sus‐TMPRSS2 cells derived H9 subtype avian influenza vaccine and there were no negative effects on body weight increase in these chickens. Taken together, the results of this work revealed that MDCK‐Sus‐TMPRSS2 cell line could be a promising and safe substitute for embryonated chicken eggs as a host cell line for H9 subtype avian influenza virus propagation.

Immortalization of chicken embryonic liver-derived cell line by stable expression of hMRP18S-2 for serotype 4 fowl adenovirus propagation

Inclusion body hepatitis and hydropericardium-hepatitis syndrome caused by serotype 4 fowl adenovirus (FAdV-4) have emerged in China since 2013. FAdV is usually propagated in primary chicken embryonic liver cells or embryo yolk sac. The aim of this work was to develop an immortalized CEL cell line by stable expression of human mitochondrial ribosomal protein 18S-2, named CEL-hMRP18S-2 cells, for the propagation of FAdV-4. The maximum cell density of CEL-hMRP18S-2 cells could reach 2.65 × 106 cells/ml in four-days culture. According to the mRNA levels of cell-cycle related genes in CEL-hMRP18S-2 cells tested by qRT-PCR, we speculated that the transformation of hMRP18S-2 into CEL cells caused the functional inactivation of p53 and the significant down-regulation of p15INK4b might cause the hyperphosphorylated form of Rb, releasing E2F-1 factor and enhancing the E2F-dependent transcription for cell cycle progression. It was suspected that the up-regulated c-Myc mRNA level at the initial period of immortalization might prompt transformed cells through the G0-G1 checkpoint. The normal CPE was observed in CEL-hMRP18S-2 cells infected by FAdV-4 and microcarrier suspension culture performed for FAdV-4 propagation with 9.0 lgTCID50/ml suggested that CEL-hMRP18S-2 cells could be a useful continuous cell line for isolation of wild FAdV and production of FAdV-inactivated vaccine.