Protective immune response induced by Leghorn male hepatoma cell-adapted fowl adenovirus-4.

Fowl adenovirus-4 (FAdV-4) is a highly contagious virus that causes acute and lethal hepatitis. It leads to substantial economic losses in the poultry industry. Among the structural proteins of FAdV-4, hexon and fiber2 are associated with immunopathogenesis. A frameshift mutation was generated in the fiber2 protein by seral passages in the Leghorn male hepatoma (LMH) cell line. Immunization using the attenuated virus (80 times passaged) before the virulent FAdV-4 challenge protected hosts from the infection and cleared the invading virus. In immunized animals, activated CD4+ and CD8+ T cell populations were larger during the FAdV-4 challenge. The change in the B cell population was similar. Myeloid cells were highly increased during FAdV-4 infection after the immunization, but the immunization inhibited the expansion in both liver and spleen. The functional gene expression for immune modulation was strongly associated with immune cell changes in the liver, however, this association was not strong in the spleen. The present findings imply that genetic modification by cellular adaptation regulates immune cell phenotype and function in the target organ. In addition, we suggest the attenuated virus as a protective strategy against the novel FAdV-4 strains.

Plant-expressed Zika virus envelope protein elicited protective immunity against the Zika virus in immunocompetent mice.

Zika virus infection causes multiple clinical issues, including Guillain-Barré syndrome and neonatal malformation. Vaccination is considered as the only strategy for the prevention of ZIKV-induced clinical issues. This study developed a plant-based recombinant vaccine that transiently expressed the ZIKV envelope protein (ZikaEnv:aghFc) in Nicotiana benthamiana and evaluated the protective immunity afforded by it in immunocompetent mice. ZikaEnv:aghFc induced both humoral and cellular immunity at a low dose (1-5 µg). This immune-inducing potential was enhanced further when adjuvanted CIA09A. In addition, antigen-specific antibodies and neutralizing antibodies were vertically transferred from immunized females to their progeny and afforded both protective immunity to ZIKV and cross-protection to Dengue virus infection. These results suggest that our plant-based ZIKV vaccine provides a safe and efficient protective strategy with a competitive edge.

Short chain fatty acids facilitate protective immunity by macrophages and T cells during acute fowl adenovirus-4 infection.

Short chain fatty acids (SCFAs) are major gut metabolites that are involved in the regulation of dysfunction in immune responses, such as autoimmunity and cytokine storm. Numerous studies have reported a protective action of SCFAs against infectious diseases. This study investigated whether SCFAs have protective effect for immunity during fowl adenovirus-4 (FAdV-4) infection. We examined whether SCFA mixture (acetate, propionate, and butyrate) administration could protect against intramuscular challenge of a virulent viral strain. SCFA treatment promoted MHCII-expressing monocytes, the active form of T cells, and effector molecules in both peripheral and lymphoid tissues. It also boosted the production of immune molecules involved in pathogen elimination by intraepithelial lymphocytes and changed the intestinal microbial composition. We suggest that gut metabolites influence the gut microbial environment, and these changes stimulate macrophages and T cells to fight against the intramuscular challenge of FAdV-4.

Genetic modification regulates pathogenicity of a fowl adenovirus 4 strain after cell line adaptation (genetic mutation in FAdV-4 lowered pathogenicity).

Fowl adenovirus 4 (FAdV-4) is a major avian virus that induces fatal diseases in chicken such as, hydropericardium and hepatitis. The viral structure consists of hexon, penton, fiber-1, and fiber-2 which are associated with immunopathogenesis. In this study, we investigated the genetic modification of a FAdV-4 strain after continuous passages in a cell line and evaluated the pathogenicity associated with mutations. We used the FadV-4 KNU14061 strain, which was isolated from layers in 2014. The virus went through 80 passages in the Leghorn male hepatoma (LMH) cell line. The full genetic sequence was identified, and we found a frameshift in the fiber-2 amino acid sequence after the initial thirty passages. To examine whether the frameshift in the fiber-2 gene affects the pathogenicity in chicken, we inoculated LMH80 (80 times passaged) and LMH10 (10 times passaged) into 3-day-old chickens and examined the pathogenesis. LMH10 infection via intramuscular route induced fatal pathology, but LMH80 did not. Furthermore, LHM80 pre-treatment protected hosts from the LMH10 challenge. Thus, the genetic modification isolated by serial passage lowered pathogenicity and the resulting virus acted as an attenuated vaccine that can be a FAdV-4 vaccine strain candidate.

5-Azacytidine (5-aza) Induces p53-associated Cell Death Through Inhibition of DNA Methyltransferase Activity in Hep3B and HT-29 Cells.

BACKGROUND/AIM: DNA methylation regulates the expression of genes that control mechanisms of cell death. TP53 gene expression inhibits tumorigenesis, and its action is closely associated with cell death. 5-Azacytidine (5-aza), increases the expression of the TP53 gene by inhibiting DNA methyltransferase. MATERIALS AND METHODS: Using 5-aza, we induced DNA hypomethylation in p53-null and p53-expressing cancer cell lines and investigated potential mechanisms of cancer cell death. RESULTS: TP53 expression promoted cell death. Notably, methylation-specific PCR (MSP) and bisulfite sequencing revealed more methylation sites at the TP53 promoter region in p53-null cells than in p53-expressing cells. CONCLUSION: This study suggests a novel mechanism of tumorigenesis regulated by p53 expression.

Genetic and immunological characterization of commercial infectious bronchitis virus vaccines used in Korea.

The aim of the study was to investigate the genetic and immunogenic features of commercial vaccines against infectious bronchitis virus (IBV), which is a major contagious pathogen of poultry. Although numerous vaccines have been developed based on the genetic characteristics of field strains, the continual emergence of variants decreases vaccine efficacy and cross-protection. To address this issue, we compared the S1 gene sequences of three IBV vaccines commercially available in Korea with those of various field isolates. Phylogenetic analysis showed that the vaccine strains clustered into two different lineages. Comparison of commercial vaccines with their parental viruses showed that most of the genetic variability occurred around hypervariable regions (HVRs). Conversely, antigenic stimulation with commercial vaccines and regional IBV variants was not sufficient to alter major immune cell phenotypes. Our study suggests that vaccines should be selected carefully based on their genetic background because genetic variability can affect the antigenicity of vaccines and host immune responses.

Zika virus baculovirus-expressed envelope protein elicited humoral and cellular immunity in immunocompetent mice.

Zika virus (ZIKV) is a mosquito-borne virus that has a high risk of inducing Guillain-Barré syndrome and microcephaly in newborns. Because vaccination is considered the most effective strategy against ZIKV infection, we designed a recombinant vaccine utilizing the baculovirus expression system with two strains of ZIKV envelope protein (MR766, Env_M; ZBRX6, Env_Z). Animals inoculated with Env_M and Env_Z produced ZIKV-specific antibodies and secreted effector cytokines such as interferon-γ, tumor necrosis factor-α, and interleukin-12. Moreover, the progeny of immunized females had detectable maternal antibodies that protected them against two ZIKV strains (MR766 and PRVABC59) and a Dengue virus strain. We propose that the baculovirus expression system ZIKV envelope protein recombinant provides a safe and effective vaccine strategy.

Transcriptome analysis of primary chicken cells infected with infectious bronchitis virus strain K047-12 isolated in Korea.

Infectious bronchitis virus (IBV), an avian coronavirus, is highly contagious. Chickens with IBV infection develop acute pathogenesis in multiple organs, including the respiratory and urogenital tracts. Frequent recombination in the spike (S) glycoprotein gene has made vaccine strategies ineffective. To understand IBV pathogenesis, we analyzed the genetic distance between Korean IBV isolates and other coronaviruses, including SARS-CoV-2. To obtain comprehensive information about early immune responses such as innate cytokine production and associated immune regulation during IBV infection, we infected primary chicken embryonic kidney cells and performed transcriptome analysis. We observed that the functional pathways of innate immunity are regulated and confirmed expression of genes that coordinate early immune responses. Understanding the immune profile of the host cell may assist in vaccine development.