Progress and hurdles in the development of influenza virus-like particle vaccines for veterinary use

Chimeric H5 influenza virus-like particle vaccine elicits broader cross-clade antibody responses in chickens than in ducks

Eurasian-lineage highly pathogenic avian influenza (HPAI) H5 viruses have spread throughout Asia, the Middle East, Europe, Africa, and most recently, North and South America. These viruses are independently evolving into genetically and antigenically divergent clades, and broad-spectrum vaccines protecting against these divergent clades are needed. In this study, we developed a chimeric virus-like particle (VLP) vaccine co-expressing hemagglutinins from two clades (clades 1 and 2.3.2.1) of HPAI H5 viruses and performed comparative cross-clade hemagglutination inhibition (HI) analysis in chickens and ducks. The chimeric VLP immunization induced a significantly broader spectrum of antibodies against various clades of HPAI H5 viruses than monovalent VLPs both in chickens and ducks. While the chimeric VLP led to broadened antibody responses in both species, significantly lower levels of HI antibodies were elicited in ducks than in chickens. Moreover, boost immunization failed to increase antibody responses in ducks regardless of the VLPs used, in contrast to chickens that showed significantly enhanced antibody responses upon boost immunization. These results suggest (1) the potential application of the chimeric VLP technology in poultry to help control HPAI H5 viruses by offering broader antibody responses against antigenically different strains and (2) possible obstacles in generating high levels of antibody responses against HPAI H5 viruses in ducks via vaccination, implying the need for advanced vaccination strategies for ducks.

Prevalence and associated risk factors of avian influenza A virus subtypes H5N1 and H9N2 in LBMs of East Java province, Indonesia: a cross-sectional study

Background

Avian influenza A virus subtypes H5N1 and H9N2 are contagious zoonotic diseases that are circulating in Indonesia and have raised increasing concern about their potential impacts on poultry and public health. A cross-sectional study was carried out to investigate the prevalence and associated risk factors of avian influenza A virus subtypes H5N1 and H9N2 among poultry in the live bird markets of four cities in East Java province, Indonesia.

Methods

A total of 600 tracheal and cloacal swabs (267 from backyards, 179 from broilers, and 154 from layers) from healthy birds were collected. The samples were inoculated into specific pathogenic-free embryonated eggs at 9-day-old via the allantoic cavity. qRT-PCR was used for further identification of avian influenza.

Results

The overall prevalence of circulating influenza A virus subtypes H5N1 and H9N2 was 3.8% (23/600, 95%CI [0.0229–0.0537]). Prevalence was higher in backyards at 5.99% (16/267) followed by broilers (2.23% (4/179)) and layers (1.68% (3/154)). The final multivariable model revealed five risk factors for H9N2 infections: presence of ducks (p = 0.003, OR = 38.2), turkeys (p = 0.017 OR = 0.032), and pheasants in the stall (p = 0.04, OR = 18.422), dry (p = 0.006) and rainy season (p < 0.001), and household birds (p = 0.002) and seven factors for H5N1 infections including: observing rodents (p = 0.036, OR = 0.005), stray dogs access (p = 0.004 OR ≤ 0.001), presence of turkeys (p = 0.03 OR = 0.007), chukars/partridges (p = 0.024 OR = 2500), and peafowls in the stalls (p = 0.0043 OR ≤ 0.001), rainy season (p = 0.001) and birds from the household sources (p = 0.002) in the live bird markets.

Conclusions

The findings of the current study illustrate the recurring infection and presence of both avian influenza viruses and associated risk factors in the surveyed marketplaces. Effective protective measures and mitigation strategies for risks outlined in this study could help to reduce the burden of H5N1 and H9N2 AI subtypes into the live bird markets of Indonesia.

Emerging threats and vaccination strategies of H9N2 viruses in poultry in Indonesia: A review

Avian influenza virus subtype H9N2 was first documented in Indonesia in 2017. It has become prevalent in chickens in many provinces of Indonesia as a result of reassortment in live bird markets. Low pathogenic avian influenza subtype H9N2 virus-infected poultry provides a new direction for the influenza virus. According to the latest research, the Indonesian H9N2 viruses may have developed through antigenic drift into a new genotype, posing a significant hazard to poultry and public health. The latest proof of interspecies transmission proposes that the next human pandemic variant will be the avian influenza virus subtype H9N2. Manipulation and elimination of H9N2 viruses in Indonesia, constant surveillance of viral mutation, and vaccine updates are required to achieve effectiveness. The current review examines should be investigates/assesses/report on the development and evolution of newly identified H9N2 viruses in Indonesia and their vaccination strategy.

Protective effect of bivalent H1N1 and H3N2 VLP vaccines against Eurasian avian-like H1N1 and recent human-like H3N2 influenza viruses in a mouse model

Eurasian avian-like (EA) H1N1 swine influenza viruses (SIVs) are currently the most prevalent SIVs in Chinese swine populations, but recent human-like H3N2 SIV subtypes have also been frequently isolated. Hence, there is an urgent need to develop an effective vaccine against both EA H1N1 and recent human-like H3N2 infections. In this study, we utilized the baculovirus expression system to produce virus-like particles (VLPs) containing hemagglutinin protein (HA) and matrix protein (M1) based on A/Swine/Guangdong/YJ4/2014 (H1N1) and A/swine/Guangdong/L22/2010 (H3N2). An immunological experiment showed that in a mouse model, bivalent VLP vaccines against H1N1 and H3N2 can induce stronger humoral and cellular immune responses than whole influenza virus vaccines. Compared with monovalent inactivated vaccines that cannot offer protection against different SIV subtypes, monovalent H1N1 or H3N2 VLP vaccines can provide partial protection against lethal challenge by viruses of different subtypes. Meanwhile, bivalent VLP vaccines against H1N1 and H3N2 can provide full protection against lethal doses of homologous and heterologous viruses belonging to the EA H1N1 or recent human-like H3N2 lineage. These results suggest a promising approach to the development of vaccines against SIVs.

Evaluation of Protective Efficacy of Influenza Virus Like Particles Prepared from H5N1 Virus of Clade 2.2.1.2 in Chickens

Highly pathogenic Avian Influenza (HPAI) viruses continue to cause severe economic losses in poultry species worldwide. HPAI virus of subtype H5N1 was reported in Egypt in 2006, and despite vaccination efforts, the virus has become endemic. The current study aims to evaluate the efficacy of a virus-like particle (VLP) based vaccine in vivo using specific pathogen-free (SPF) chickens. The vaccine was prepared from the HPAI H5N1 virus of clade 2.2.1.2 using the baculovirus expression system. The VLPs were quantitated and characterized, including electron microscopy. In addition, the protection level of the VLPs was evaluated by using two different regimens, including one dose and two-dose vaccinated groups, which gave up to 70% and 100% protection level, respectively. The results of this study emphasize the potential usefulness of the VLPs-based vaccine as an alternative vaccine candidate for the control of AIV infection in poultry.

Influence of temperature on the antigenic changes of virus-like particles

Purpose

In this study, we investigated whether the antigenic changes of the virus-like particles (VLPs) are affected by the temperature during storage.

Materials and Methods

After exposing the recombinant influenza VLPs to various temperatures for a period, antigenic changes were examined through in vitro hemagglutination receptor binding assay and in vivo mouse experiments.

Results

Influenza VLPs were exposed at three different temperatures of low, middle, and high on a thermo-hygrostat. High temperature exposed influenza VLPs were showed significantly reduced HA activity and immunogenicity after mouse single immunization over time compared low and middle. When the VLPs exposed to the high temperature were inoculated once in the mice, it was found that the immunogenicity was significantly reduced compared to the VLPs exposed to the low temperature. However, these differences were almost neglected when mice were inoculated twice even with VLPs exposed to high temperatures.

Conclusion

This study suggests that similar protective effects can be expected by controlling the number of vaccination and storage conditions, although the antigenic change in the VLP vaccines occurred when exposed to high temperature.

Vaccines against avian influenza in poultry

The review presents the latest data about the types of vaccines against avian influenza that are used in current medical practice or are under development. Inactivated whole virion vaccines, live vector vaccines, as well as experimental vaccines developed using genetic engineering techniques (e.g. subunit vaccines, VLP vaccines, DNA vaccines) were considered. The efficiency of influenza reverse genetic technology for the development of prototype vaccine strains was noted.

Chimeric Bivalent Virus-Like Particle Vaccine for H5N1 HPAI and ND Confers Protection against a Lethal Challenge in Chickens and Allows a Strategy of Differentiating Infected from Vaccinated Animals (DIVA)

Highly pathogenic avian influenza (HPAI) and Newcastle disease (ND) are considered as the most devastating poultry infections, owing to their worldwide distribution and economical threat. Vaccines have been widely used to control these diseases in the poultry industry in endemic countries. However, vaccination policy without differentiating infected animals from vaccinated animals (DIVA) makes the virus surveillance difficult. In this study, we developed a bivalent virus-like particle (VLP) vaccine that is composed of the hemagglutinin (HA) and matrix 1 (M1) proteins of the H5N1 HPAI virus (HPAIV) and a chimeric protein containing the ectodomain of the ND virus (NDV) fusion (F) protein fused with the cytoplasmic and transmembrane domains of the HPAIV HA protein. A single immunization of chickens with the chimeric VLP vaccine induced high levels of hemagglutination inhibition (HI) antibody titers against H5N1 HPAI virus and anti-NDV antibody detected in ELISA and protected chickens against subsequent lethal HPAIV and NDV infections. Furthermore, we could easily perform DIVA test using the commercial NP-cELISA tests against HPAIV and HI assay against NDV. These results strongly suggest that utilization of chimeric VLP vaccine in poultry species would be a promising strategy for the better control of HPAI and ND simultaneously.