Immune Evaluation of Recombinant Lactobacillus plantarum With Surface Display of HA1-DCpep in Mice

Avian influenza viruses can be efficiently transmitted through mucous membranes, and conventional vaccines are not effective in protecting against mucosal infection by influenza viruses. To induce multiple immune responses in an organism, we constructed a recombinant Lactobacillus plantarum expressing the influenza virus antigen HA1 with the adjuvant dendritic cell-targeting peptide (DCpep). The recombinant L. plantarum strains NC8Δ-pWCF-HA1 and NC8Δ-pWCF-HA1-DCpep were used to immunize mice via oral administration, and the humoral, cellular and mucosal immune responses were evaluated. In addition, the serum levels of specific antibodies and hemagglutination inhibition (HI) levels were also measured. Our results showed that recombinant L. plantarum activated dendritic cells in Peyer's patches (PPs), increased the numbers of CD4⁺IFN-γ⁺ and CD8⁺IFN-γ⁺ cells in the spleen and mesenteric lymph nodes (MLNs), and affected the ability of CD4⁺ and CD8⁺ cells to proliferate in the spleen and MLNs. Additionally, recombinant L. plantarum increased the number of B220⁺IgA⁺ cells in PPs and the level of IgA in the lungs and different intestinal segments. In addition, specific IgG, IgG1 and IgG2a antibodies were induced at high levels in the mice serum, specific IgA antibodies were induced at high levels in the mice feces, and HI potency was significantly increased. Thus, the recombinant L. plantarum strains NC8Δ-pWCF-HA1 and NC8Δ-pWCF-HA1-DCpep have potential as vaccine candidates for avian influenza virus.

Induction of cross-group broadly reactive antibody response by natural H7N9 avian influenza virus infection and immunization with inactivated H7N9 vaccine in chickens

Pre-existing immunity against the conserved haemagglutinin (HA) stalk underlies the elicitation of cross-group antibody induced by natural H7N9 virus infection and immunization in humans. However, whether broadly reactive antibodies can be induced by H7N9 infection and immunization in the absence of pre-existing stalk-specific immunity is unclear. In this study, antibody response induced by H7N9 virus infection and immunization with inactivated and viral-vectored H7N9 vaccines in naïve chickens was analysed. The results showed that H7N9 infection and immunization with inactivated vaccine resulted in potent induction of haemagglutination-inhibition (HI), virus neutralization (VN) and HA-binding antibodies, whereas Newcastle disease virus (NDV)-vectored H7N9 vaccine induced marginal HI and VN titres but high levels of HA-binding antibody. In addition, H7N9 infection and immunization induced stalk-specific antibodies in naïve chickens and these antibodies recognized different epitopes in the stalk. Virus infection and immunization with inactivated vaccine elicited antibodies cross-reactive with both group 1 and group 2 HAs, while antibodies induced by NDV-H7N9 vaccination showed a narrower cross-reactivity within group 2. Moreover, only homologous neutralizing activity of the sera against H7N9 virus was observed, and cross-binding antibodies did not show heterosubtypic neutralizing activity. Our results indicated that cross-group binding but non-neutralizing antibodies primarily targeting the stalk can be induced by natural H7N9 infection and immunization with inactivated vaccine in naïve chickens. This suggests that at least in a naïve chicken model, pre-existing stalk-specific immunity is not required for induction of broadly reactive antibodies. Additionally, H7N9-based immunogens may be explored as vaccine candidates or as a prime component to induce broadly protective influenza immunity.

Hemagglutinin-Specific Non-neutralizing Antibody Is Essential for Protection Provided by Inactivated and Viral-Vectored H7N9 Avian Influenza Vaccines in Chickens

Hemagglutination inhibition (HI) and virus neutralization antibody (nAb) do not always correlate with the protection of H7 avian influenza vaccines in mammals and humans. The contribution of different classes of antibodies induced by H7N9 vaccines to protection is poorly characterized in chickens. In this study, antibody responses induced by both inactivated and viral-vectored H7N9 vaccines in chickens were dissected. Chickens immunized with inactivated H7N9 vaccine showed 50% seroconversion rate and low HI and nAb titers at week 3 post immunization. However, inactivated H7N9 vaccine elicited 100% seroconversion rate in terms of high levels of HA-binding IgG antibody determined by ELISA. Despite inducing low levels of nAb, inactivated H7N9 vaccine conferred full protection against H7N9 challenge in chickens and markedly inhibited virus shedding. Similarly, Newcastle disease virus (NDV)-vectored H7N9 vaccine induced marginal HI and nAb titers but high level of IgG antibody against H7N9 virus. In addition, NDV-H7N9 vaccine also provided complete protection against H7N9 challenge. Chicken antisera had a high IgG/VN ratio, indicating that a larger proportion of serum antibodies were non-neutralizing antibody (non-nAb). More importantly, passive transfer challenge experiment showed that non-neutralizing antisera provided partial protection (37.5%) of chickens against H7N9 challenge, without significant difference from that provided by neutralizing antisera. In conclusion, our results suggest that antibodies measured by the traditional HI and virus neutralization assays do not correlate with the protection of inactivated and viral-vectored H7N9 vaccines in chickens, and HA-binding non-nAb also contributes to the protection against H7N9 infection. Total binding antibody can be used as a key correlate to the protection of H7N9 vaccine.

[Willingness and influencing factors related to "centralized slaughtering, fresh poultry listing and marketing" strategy among the household chefs in Guangzhou]

Objective: To study the willingness and influence factors related to "centralized slaughtering, fresh poultry listing and marketing" strategy, among the household chefs, and provide reference for government to adjust and optimize the strategy on avian influenza prevention. Methods: According to the geographical characteristics and regional functions, 6 'monitoring stations' were selected from 12 residential districts of Guangzhou, respectively. Another 21 meat markets which selling live poultry, were selected in each station and 5 household chefs of each market were invited to attend a face to face interview. Basic information, personal cognitive, willingness and influencing factors to the policy were under study. Univariate and multivariate logistic regression methods were used. Results: A total of 664 household chefs underwent the survey and results showed that the rate of support to the "centralized slaughtering, fresh poultry listing and marketing" strategy was 44.6% (296/664). Results from the multi-factor logistic regression showed that those household chefs who were males (OR=1.618, 95% CI: 1.156-2.264, P=0.005), having received higher education (OR=1.814, 95% CI: 1.296-2.539, P=0.001), or believing that the existence of live poultry stalls was related to the transmission of avian influenza (OR=1.918, 95% CI: 1.341-2.743, P<0.001) were factors at higher risk. These household chefs also intended to avoid the use of live poultry stalls (OR=1.666, 95%CI: 1.203-2.309, P=0.002) and accept the "centralized slaughtering, fresh poultry listing and marketing" strategy. Conclusion: Detailed study on this subject and, setting up pilot project in some areas as well as prioritizing the education programs for household chefs seemed helpful to the implementation of the 'freezing-fresh poultry' policy.

Tackling a novel lethal virus: a focus on H7N9 vaccine development

INTRODUCTION

Avian-origin H7N9 influenza viruses first detected in humans in China in 2013 continue to cause severe human infections with a mortality rate close to 40%. These viruses are acknowledged as the subtype most likely to cause the next influenza pandemic. Areas covered: Here we review published data on the development of H7N9 influenza vaccine candidates and their evaluation in preclinical and clinical trials identified on PubMed database with the term 'H7N9 influenza vaccine'. In addition, a search with the same term was done on ClinicalTrials.gov to find ongoing clinical trials with H7N9 vaccines. Expert commentary: Influenza vaccines are the most powerful tool for protecting the human population from influenza infections, both seasonal and pandemic. During the past four years, a large number of promising H7N9 influenza vaccine candidates have been generated using traditional and advanced gene engineering techniques. In addition, with the support of WHO's GAP program, influenza vaccine production capacities have been established in a number of vulnerable low- and middle-income countries with a high population density, allowing the countries to be independent of vaccine supply from high-income countries. Overall, it is believed that the world is now well prepared for a possible H7N9 influenza pandemic.

Fear and trust: How risk perceptions of avian influenza affect Chinese consumers' demand for chicken

This article quantifies the impact of H7N9 bird flu on chicken demand and consumer willingness to pay (WTP) in China. We measure risk perception, fear and trust against actual reduction in consumption and stated change in WTP for safe chicken between 2012 and 2013. Through a survey conducted in each year on the same Chinese urban consumers, we found that the consumption of chicken never increased after the emergence of H7N9 in 2013, and WTP for safe chicken did not necessarily increase relative to generic risks associated with consuming chicken in 2012. Factors such as the fear of H7N9's spreading, the impact of distrust (especially the distrust in government) enhanced the deviation of consumption and WTP; and the sheer mentioning of H7N9 is more important and negative than whether it was associated with a risk-perception reducing or risk-perception elevating message given to consumers.

A new perspective on C-reactive protein in H7N9 infections. Int J Infect Dis. 2016;44:31-36. [PMID: 26809124 DOI: 10.1016/j.ijid.2016.01.009]

OBJECTIVES

The avian influenza H7N9 virus can cause cytokine overproduction and result in severe pneumonia and acute respiratory distress syndrome. Many studies have focused on hypercytokinemia during avian influenza infection. This study examined the association between C-reactive protein (CRP) and cytokines.

METHODS

The plasma cytokine and chemokine profiles of 57 H7N9 patients were investigated using a multiplex immunoassay. The CRP levels of patients with H7N9 and patients with H1N1 were also compared. Further, the association between cytokines and CRP in H7N9 infections was explored.

RESULTS

Compared with H1N1 virus, it was found that H7N9 virus induced higher expression of CRP, leading to cytokine storms. Several cytokines, including MIP-1β, MCP-1, IP-10, and IL-6, were observed to have significantly positive relationships with CRP levels, whereas IL-17A was negatively associated with CRP levels.

CONCLUSIONS

These findings suggest that CRP may be used as an early indicator to identify high-risk patients, to assess disease progression, and to determine the development of hypercytokinemia.

Characterization of Humoral Responses Induced by an H7N9 Influenza Virus-Like Particle Vaccine in BALB/C Mice

In April 2013, human infections with a novel avian influenza (H7N9) virus emerged in China. It has caused serious concerns for public health throughout the world. However, there is presently no effective treatment, and an A (H7N9) H7 subtype influenza vaccine is not available. Vaccination with virus-like particles (VLPs) has showed considerable promise for many other subtype influenza viruses. To produce H7N9 VLPs, full length, unmodified hemagglutinin (HA), neuraminidase (NA), and matrix1 (M1) genes from the A/Wuxi/1/2013(H7N9) were cloned into a pCDNA5.1 FRT vector. By co-transfection, VLPs containing HA, NA, and M1 were secreted by 293T cells. VLPs were purified by ultracentrifugation and injected into mice by the intramuscular route. In animal experiments, humoral and cellular immunoresponse were all triggered by H7N9 VLPs. High levels of specific antibodies and the isotypes of IgG were detected by ELISA. Anamnestic cellular immune responses were examined by detecting specific cytotoxic T cell for IFN-Υ production in ELISPOT assay. The hemagglutination-inhibition (HAI) against the homologous virus was more than 1:64, and cross-reactive HAI titers against the heterologous virus (H1N1 and H3N2) were more than 1:16. Moreover, VLPs immunized mice showed a rapid increase of neutralizing antibodies, with neutralizing antibody titers more than 1:8, which increased four-fold against PBS immunized mice in week four. By week six, the mice had high neutralization ability against the given strain and held a potent homologous virus neutralizing capacity. Thus, VLPs represent a potential strategy for the development of a safe and effective vaccine against novel avian influenza (H7N9) virus.

Chest X-ray and CT findings of early H7N9 avian influenza cases

BACKGROUND

The H7N9 strain of bird flu is a new type of avian flu that was identified at the end of March 2013. The disease is concerning because most patients have become severely ill.

PURPOSE

To study the X-ray and computed tomography (CT) findings of early H7N9 avian influenza cases.

MATERIAL AND METHODS

Chest radiography and CT were performed in six patients with H7N9 avian influenza within 1-20 days after onset. The CT examinations included conventional spiral CT and high-resolution CT. The findings on the radiography and CT images were analyzed.

RESULTS

Abnormal X-ray and CT findings were present in all of the patients. All of the cases had acute onset. In the early stage, the right lung was more commonly affected (particularly in the right upper and middle lobes). The lesions rapidly expanded to the entire lungs and were characterized primarily by ground-glass opacities (GGOs) combined with consolidation. Diffuse GGO was observed in all six cases (1 was symmetric, and 5 were non-symmetric). Local consolidation was found in four cases, and lobar consolidation was found in two cases. Normal lung tissue was observed between the lesions. Pleural thickening was common and was combined with pleural/pericardial effusion or mediastinal lymph node enlargement. Reticular changes, centrilobular nodules, and the tree-in-bud sign were observed in some cases, but reticular changes, bronchial wall thickening, and hyperinflation were not found.

CONCLUSION

Radiological changes associated with both acute pneumonia and acute interstitial inflammation were observed in early H7N9 avian influenza cases. Serial chest X-rays were useful for the diagnosis and severity assessment of the disease. CT may provide a more accurate assessment of the lung pathology.

Cytokine and chemokine levels in patients infected with the novel avian influenza A (H7N9) virus in China

H7N9 avian influenza is an emerging viral disease in China caused by avian influenza A (H7N9) virus. We investigated host cytokine and chemokine profiles in serum samples of H7N9 patients by multiplex-microbead immunoassays. Statistical analysis showed that IP-10, IL-6, IL-17, and IL-2 were increased in H7N9 infected patients. Furthermore, IL-6 and the chemokine IP-10 were significantly higher in severe H7N9 patients compared to nonsevere H7N9 cases. We suggest that proinflammatory cytokine responses, characterized by a combined Th1/Th17 cytokine induction, are partially responsible for the disease progression of patients with H7N9 infection.