Jae-Keun Park

Intranasal administration of live Lactobacillus species facilitates protection against influenza virus infection in mice.

Influenza virus infections continue to be a significant public health problem. For improved therapies and preventive measures against influenza, there has been an increased tendency in modern medicine involving the use of probiotics. In this study, we compared the protective efficacy of various live and dead Lactobacillus species against challenge with influenza virus in mice according to the administration route and dose. In addition, to understand the underlying mechanism behind this clinical protective effect, we performed immunologic assays including examination of IgA levels and cytokine profiles in the lung. The survival rate of mice receiving intranasal administration of Lactobacillus was higher than after oral administration, and administration of live bacteria was more protective than of dead bacteria. The lung levels of interleukin (IL)-12 and IgA were significantly increased (P<0.05). Conversely, the levels of the pro-inflammatory cytokines tumor necrosis factor-alpha and IL-6 were decreased. Interestingly, there were huge differences in protective effects of various Lactobacillus strains on influenza virus infection. Therefore, for clinical applications, selection of effective strains could be critical and individually optimized application regimens of the selected strains are required.

An emerging recombinant cluster of nephropathogenic strains of avian infectious bronchitis virus in Korea.

Abstract The infectious bronchitis virus (IBV) is continuously evolving through point mutation and recombination of their genome, subsequently the emergence of IBV variants complicates disease control. The objective of this study was to investigate genetic characterization of new IBV variants isolated from commercial chicken flocks in Korea collected between 2005 and 2010. Phylogenetic analysis revealed that all new IBV isolates belonged to Korean group II (K-II), which included the nephropathogenic IBV strains. However, the isolates formed a new gene cluster that was distinguished from the two distinct K-II subgroups (KM91-like and QX-like). Recombination events were identified in the S1 gene, with their putative parental strains being the KM91-like or QX-like subgroup. In addition, two crossover sites were observed in the S1 gene of IBV isolates. These results suggest that natural genetic recombination between heterologous strains classified into different genetic groups has occurred and may have caused the emergence of new IBV strains. This finding provides important information on IBV evolution and is essential for the effective control of IB in Korea.

H9N2 avian influenza virus-like particle vaccine provides protective immunity and a strategy for the differentiation of infected from vaccinated animals

In the present study, virus-like particles (VLPs) were evaluated as a candidate poultry vaccine against avian influenza virus (AIV) subtype H9N2. Specific pathogen-free chickens received a single injection of the VLP vaccine expressing HA and M1 protein of AIV H9N2 (H9 HA VLP) at escalating doses in the presence or absence of ISA70 water-in-oil adjuvant. At 3 weeks post vaccination, we performed hemagglutination inhibition (HI) test and enzyme-linked immunosorbent assay (ELISA) to determine serological immune responses, and challenge studies using SPF chickens. A single dose of H9 HA VLP vaccine induced high levels of HI antibodies and lowered frequencies of virus isolation after the wild-type virus challenge. The addition of ISA70 adjuvant significantly increased the immunogenicity of H9 HA VLP vaccines. Furthermore, it allows differentiation of AIV-infected chickens from vaccinated chickens with an ELISA using nucleocapsid antigen, which offers a promising strategy to differentiate infected from vaccinated animals (DIVA). These results provide support for continued development of the VLP as an animal vaccine against influenza virus.

Identification and virulence characterization of fowl adenoviruses in Korea.

SUMMARY. Since 2007, 55 adenovirus strains have been isolated from commercial chicken flocks in Korea and have been identified and the pathogenicity of these isolates was confirmed in specific-pathogen-free chickens of different age. Based on sequencing analysis of the hexon gene, 55 FAdV isolates were genetically related to the IBH-2A strain of FAdV3 (4 isolates, 99.2% to 100%), the KR5 strain of FAdV4 (22 isolates, 97.9% to 99.2%), the 764 strain of FAdV9 (11 isolates, 99.1% to 99.3%), and the 1047 strain of FAdV11 (18 isolates, >99%). Experimental infections with four serotypes of FAdV resulted in high mortality of 18-day-old chicken embryos and 1-day-old chicks with marked liver necrosis similar to those observed in the natural outbreaks. Notably, specific hydropericardium was observed in chicks challenged with the K531 strain (serotype 4). However, 3-wk-old chickens challenged with FAdVs, regardless of serotype, did not show any clinical signs or mortality except histologic lesions of focal hepatocytic necrosis with mild lymphocytic infiltration. The results indicate that four FAdV serotypes (3, 4, 9, and 11) are the dominant serotypes of FAdVs in the Korea and are pathogenic enough to cause clinical disease in young chicks. The present investigation provides important information on the epidemiology and pathogenesis of FAdVs and highlights the importance of control strategies against FAdV infection in Korea.

Use of bacteriophage for biological control of Salmonella Enteritidis infection in chicken

Bacteriophage ΦCJ07 with broad host ranges for Salmonella strains isolated from sewage effluent were used to reduce Salmonella Enteritidis (SE) infection in chickens. One-day-old chicks challenged with 5×10(7) colony-forming units/bird of SE were cohabitated with contact chicks and treated with three concentrations (10(5), 10(7) and 10(9) plaque forming units (PFU)/g) of bacteriophage prepared as a feed additive for 21days after challenge. Salmonella in the intestine was quantified and environmental contamination level was examined at 1, 2 and 3weeks after challenge. All treatments reduced intestinal SE colonization in challenged and contact chickens and reduced the environmental contamination level, but the reductions produced by 10(7) and 10(9)PFU/g of bacteriophage were significant (P<0.05) as compared with untreated controls. In addition, seven out of 10 (70%) contact chickens treated with 10(9)PFU/g of bacteriophage had no detectable intestinal Salmonella at 3weeks after treatment, suggesting that bacteriophage therapy significantly prevented the horizontal transmission of SE. These results provide important insights into preventive and control strategies against SE infection in poultry and indicate that the use of bacteriophage could reduce the incidence of Salmonella food poisoning.

Exchange of Newcastle disease viruses in Korea: The relatedness of isolates between wild birds, live bird markets, poultry farms and neighboring countries

Newcastle disease virus (NDV) has a worldwide distribution and is often carried by wild ducks, which may represent one of the natural reservoirs. However, the epidemiological relatedness of NDV between wild ducks and domestic poultry is unclear. A total of 14 isolates were obtained from 8439 samples from live bird markets (LBMs) and wild bird populations in Korea during from 2007 to 2010. These isolates were characterized genetically and phylogenetic analysis was conducted to investigate the relatedness between isolates from wild birds, LBM and poultry farms. In phylogenetic analysis, all 14 isolates belonged to genotype I virus within class II. Of these, nine isolates from wild birds were most closely related to the Aomori-like cluster. The five LBM isolates were most closely related to the V4-like cluster. All isolates in this study were closely related to isolates from domestic duck farms in Korea and Chinese LBM isolates. The results indicate that NDV exchange occurs between wild birds, poultry farms, LBMs and neighboring countries. Enhanced NDV surveillance is required to monitor the introduction of variant NDV in consequence of evolution in LBMs and to investigate NDV epidemiology in various species of putative hosts.

Sublingual administration of Lactobacillus rhamnosus affects respiratory immune responses and facilitates protection against influenza virus infection in mice.

The extensive morbidity and mortality caused by influenza A viruses worldwide prompts the need for a deeper understanding of the host immune response and novel therapeutic and/or prophylactic interventions. In this study, we assessed the sublingual route as an effective means of delivering probiotics against influenza virus in mice. In addition, IgA levels, NK cell activity, T cell activation, and cytokine profiles in the lungs were examined to understand the mechanism underlying this protective effect. Sublingual administration of Lactobacillus rhamnosus provided enhanced protection against influenza virus infection by enhancing mucosal secretory IgA production, and T and NK cell activity. Moreover, interleukin (IL)-12 levels in the lungs increased significantly. Conversely, IL-6 and tumor necrosis factor alpha levels in the lungs decreased significantly. On the basis of these promising findings, we propose that the sublingual mucosal route is an attractive alternative to mucosal routes for administering probiotics against influenza virus.

Prevalence and characterization of Salmonella species in entire steps of a single integrated broiler supply chain in Korea

The purpose of this study was to investigate the distribution of Salmonella species in an integrated broiler supply chain in Korea. A total of 1,214 samples from various steps of an integrated broiler production company including broiler breeder farms, broiler farms, broiler trucks, slaughterhouse, and retail chicken meats were collected and investigated. Salmonella was detected in 195 of the samples. The highest prevalence of Salmonella was observed in broiler transporting trucks (71.43%), followed by the slaughterhouse (63.89%) and broiler farms (16.05%). Salmonella Hadar was the most frequently isolated serotype (83.08%). All Salmonella Hadar isolates investigated in this study with pulsed-field gel electrophoresis showed the same XbaI pulsed-field gel electrophoresis pulsotype.

Evidence of intercontinental transfer of North American lineage avian influenza virus into Korea.

Avian influenza viruses (AIV) can be genetically distinguished by geographical origin. The present study found evidence of intercontinental transfer of North American lineage AIV into Asia via migratory bird populations. The North American lineage genes were detected in live animal markets during avian influenza surveillance, seemed to have reassorted with Eurasian AIV in wild bird habitats, and had transmitted to live animal markets. Enhanced AIV surveillance is required to understand the influence of newly transferred North American lineage AIV genes on AIV evolution in Asia and to investigate AIV ecology in various transcontinental migrant species.

Complete genome sequence of a natural reassortant H9N2 avian influenza virus found in bean goose (Anser fabalis): direct evidence for virus exchange between Korea and China via wild birds.

In 2011, we isolated a natural recombinant H9N2 avian influenza virus from fecal droppings of bean goose (Anser fabalis) in Korea. Phylogenetic analyses showed that the A/bean goose/Korea/220/2011(H9N2) isolate is a reassortant of Eurasian and North American lineages of avian influenza virus. In addition, the complete genome sequence, including all 8 gene segments, was associated with Chinese H9N2 viruses isolated from wild birds in the Hunan East Dongting Lake National Nature Reserve. These data provide direct evidence for the exchange of avian influenza viruses between Korea and China via wild birds.