Production and immunogenicity of chimeric virus-like particles containing the spike glycoprotein of infectious bronchitis virus

Infectious bronchitis virus (IBV) poses a severe threat to the poultry industry and causes heavy economic losses worldwide. Vaccination is the most effective method of preventing infection and controlling the spread of IBV, but currently available inactivated and attenuated virus vaccines have some disadvantages. We developed a chimeric virus-like particle (VLP)-based candidate vaccine for IBV protection. The chimeric VLP was composed of matrix 1 protein from avian influenza H5N1 virus and a fusion protein neuraminidase (NA)/spike 1 (S1) that was generated by fusing IBV S1 protein to the cytoplasmic and transmembrane domains of NA protein of avian influenza H5N1 virus. The chimeric VLPs elicited significantly higher S1-specific antibody responses in intramuscularly immunized mice and chickens than inactivated IBV viruses. Furthermore, the chimeric VLPs induced significantly higher neutralization antibody levels than inactivated H120 virus in SPF chickens. Finally, the chimeric VLPs induced significantly higher IL-4 production in mice. These results demonstrate that chimeric VLPs have the potential for use in vaccines against IBV infection.

Reverse genetic platform for inactivated and live-attenuated influenza vaccine

Influenza vaccine strains have been traditionally developed by annual reassortment between vaccine donor strain and the epidemic virulent strains. The classical method requires screening and genotyping of the vaccine strain among various reassortant viruses, which are usually laborious and time-consuming. Here we developed an efficient reverse genetic system to generate the 6:2 reassortant vaccine virus from cDNAs derived from the influenza RNAs. Thus, cDNAs of the two RNAs coding for surface antigens, haemagglutinin and neuraminidase from the epidemic virus and the 6 internal genes from the donor strain were transfected into cells and the infectious viruses of 6:2 defined RNA ratio were rescued. X-31 virus (a high-growth virus in embryonated eggs) and its cold-adapted strain X-31 ca were judiciously chosen as donor strains for the generation of inactivated vaccine and live-attenuated vaccine, respectively. The growth properties of these recombinant viruses in embryonated chicken eggs and MDCK cell were indistinguishable as compared to those generated by classical reassortment process. Based on the reverse genetic system, we generated 6 + 2 reassortant avian influenza vaccine strains corresponding to the A/Chicken/Korea/MS96 (H9N2) and A/Indonesia/5/2005 (H5N1). The results would serve as technical platform for the generation of both injectable inactivated vaccine and the nasal spray live attenuated vaccine for the prevention of influenza epidemics and pandemics.

Genetic characterization of nonstructural genes of H5N1 avian influenza viruses isolated in Thailand in 2004-2005.

The outbreak of highly pathogenic avian influenza (HPAI) viruses has severely disrupted poultry production and trade. Humans have been infected with HPAI H5N1 viruses and many have died. The nonstructural (NS) proteins of the virus are a factor that determines virulence. In this report, 80 NS genes of H5N1 HPAI viruses isolated from Thailand were completely sequenced and phylogenically analyzed. The percentages of identity and variable site NS1 genes were similar to NS2/nuclear export protein (NEP) genes. All NS1 genes from the samples were located in allelic group A. The NS1 and NS2/NEP proteins possess 225 and 121 amino acids, respectively. All NS1 protein samples had five amino acid deletions typical of avian influenza viruses isolated since 2002. An amino acid substitution at position 92 (G92E) of the NS1 protein, known to promote the inhibition of host immune responses, was also found in the samples.

Whole genome sequences of H5N1 influenza a virus isolated from a little grebe in Thailand.

This is the first report of the whole genome sequence of influenza A virus in an aquatic resident bird of Thailand. It was categorized into genotype Z according to its characteristics of a 20 amino acid deletion in neuraminidase and a five amino acid deletion in the nonstructural protein. The indicator for a highly pathogenic trait of the virus is the presence of a polybasic amino acid sequence at the cleavage site of HA0. The feature of resistance to the antiviral drug amantadine is found at the 31st amino acid position of M2 (serine to asparagine). Phylogenic analyses revealed that virus A/little grebe/Thailand/Phichit-01/2004 (H5N1) is closely related to the chicken and human isolates recovered from Thailand. The high degrees of similarity among the sequences and phylogenic trees indicate there was no difference between the viruses isolated from poultry and aquatic birds in Thailand at the time of study. The results also suggest the source of H5N1 avian influenza virus in the little grebe and others in Thailand may have the same origin.

Avian influenza A (H5N1) infection in a child.

A previously healthy, 9-year-old girl was admitted to the hospital with respiratory insufficiency. She had mild and severe respiratory symptoms for 3 weeks and 4 days before admission, respectively. She had a history of close contact with her domestic poultry, which was infected with avian influenza A (H5N1). She was isolated with the air-borne transmission prevention mode of treatment. Acute respiratory distress syndrome (ARDS) was documented from the time of admission and mechanical ventilation was introduced without improvement. She had multiple episodes of diarrhea for 2 days. Her condition deteriorated and she expired in 4 days. Throat swab RT-PCR and viral culture for avian influenza A (H5N1) were positive.

Avian influenza: preparing for a pandemic.

Since 1996 to 2006 there have been regular outbreaks of influenza. The genetics of virus plays an important role in its virulence mechanism. In this era of the impending threat on the influenza pandemic it is imperative that there be exchange of knowledge regarding the virus and its virulence. This article tries to address the above motive. An exhaustive review of literature has been provided regarding this viral threat.