Comparison of the Pathogenicity of SARS-CoV-2 Delta and Omicron Variants by Analyzing the Expression Patterns of Immune Response Genes in K18-hACE2 Transgenic Mice.

BACKGROUND: The recently emerged variants of the severe acute respiratory coronavirus 2 (SARS-CoV-2) pose a threat to public health. Understanding the pathogenicity of these variants is a salient factor in the development of effective SARS-CoV-2 therapeutics. This study aimed to compare the expression patterns of genes involved in immune responses in K18-hACE2 mice infected with the wild-type, Delta, and Omicron SARS-CoV-2 variants. METHODS: K18-hACE2 mice were intranasally infected with either wild-type (B.1), Delta (B.1.617.2), or Omicron (B.1.1.529) variants. On day 6 post-infection, lung, brain, and kidney tissues were collected from each variant-infected group. The mRNA expression levels of 39 immune response genes in all three groups were compared by RT-qPCR. Viral titers were measured using the median tissue culture infectious dose (TCID50) assay and expressed as Log10 TCID50/0.1 g. The statistical significance of the differences in gene expression was determined by one-way analysis of variance (ANOVA) (alpha = 0.05). RESULTS: The expression of toll-like receptors (TLRs) was upregulated in the lung and brain tissues of the wild-type- and Delta-infected groups but not in those of the Omicron-infected group. The highest expression of cytokines, including interleukin (IL)-1α, IL-1ß, IL-17α, interferon, and tumor necrosis factors, was observed in the lungs of mice infected with the wild-type variant. Additionally, CCL4, CCL11, CXCL9, and CXCL10 were upregulated (>3-fold) in wild-type-infected mice, with markedly higher expressions in the brain than in the lungs. Most of the apoptotic factors were mainly expressed in the brain tissues of Omicron-infected mice (caspase 8, caspase 9, p53, Bax, Bak, BCL-2, and Bcl-XL), whereas neither the lung nor kidney showed more than 3-fold upregulation of these apoptotic factors. CONCLUSIONS: Collectively, our findings revealed that the wild-type SARS-CoV-2 variant exhibited the highest pathogenicity, followed by the Delta variant, then the Omicron variant.

Evaluation of Efficacy of Oil Adjuvanted H5N6 Inactivated Vaccine against Highly Pathogenic H5N6 and H5N1 Influenza Viruses Infected Chickens.

BACKGROUND: Over the last 20 years, circulating highly pathogenic (HP) Asian H5 subtype avian influenza viruses have caused global pandemics in poultry and sporadic infections in humans. Vaccines are a desirable solution to prevent viral infections in poultry and reduce transmission to humans. Herein, we investigated the efficacy of an oil-adjuvanted inactivated H5N6 vaccine against highly pathogenic H5N6 and H5N1 influenza virus infections in chickens. METHODS: The polybasic amino acid cleavage site depleted HA gene and NA gene of A/Waterfowl/Korea/S57/2016 (clade 2.3.4.4) (H5N6) was assembled with the rest of the A/PR/8/34 (H1N1) genes to construct the vaccine virus. The vaccine virus was propagated in fertilized eggs, partially purified using a tangential flow filtration (TFF) system, and inactivated using formalin. The chickens were intramuscularly immunized with 384 HA, 192HA, and 96HA units of oil-adjuvanted inactivated H5N6 vaccine. Antibody titer, survival rate, and lung pathology were evaluated against the homologous H5N6: A/waterfowl/Korea/S57/2016 (clade 2.3.4.4) and heterologous H5N1: A/Hong Kong/213/2003 (clade 1) viruses 12 and 4 weeks post-vaccination (p.v.), respectively. Data were statistically analyzed using the Mann-Whitney U test. RESULTS: The 384HA (n = 10) and 192HA (n = 5) antigen-immunized chickens showed 100% survival after lethal infections with homologous H5N6, and no virus shedding was observed from tracheal and cloacal routes. All chickens that received the 384HA vaccine survived the challenge of heterologous H5N1 after 4 weeks of immunization. The chickens that received the 384HA vaccine showed mean HI titers of 60 and 240 after 12 and 4 weeks of vaccination, respectively, against HP H5N6, whereas a mean HI titer of 80 was observed in sera collected 4 weeks after vaccination against HP H5N1. CONCLUSIONS: Our findings indicate that one dose of 384HA oil-adjuvanted inactivated H5N6 vaccine can induce a long-lasting immune response against both homologous H5N6 and heterologous H5N1 infections in chickens.

Gene expression pattern differences in primary human pulmonary epithelial cells infected with MERS-CoV or SARS-CoV-2.

Coronaviruses such as MERS-CoV and SARS-CoV-2 infect the human respiratory tract and can cause severe pneumonia. Disease severity and outcomes are different for these two infections: the human mortality rate for MERS-CoV and SARS-CoV-2 is over 30% and less than 10%, respectively. Here, using microarray assay, we analyzed the global alterations in gene expression induced by MERS-CoV or SARS-CoV-2 infections in primary human pulmonary epithelial cells. Overall, the number of differentially expressed genes was higher in human lung cells infected with MERS-CoV than in cells with SARS-CoV-2. Out of 44,556 genes analyzed, 127 and 50 were differentially expressed in cells infected with MERS-CoV and SARS-CoV-2, respectively (> 2-fold increase, compared to uninfected cells). Of these, only eight genes, including the one coding for CXCL8, were similarly modulated (upregulated or downregulated) by the two coronaviruses. Importantly, these results were virus-specific and not conditioned by differences in viral load, and viral growth curves were similar in human lung cells infected with both viruses. Our results suggest that these distinct gene expression profiles, detected early after infection by these two coronaviruses, may help us understand the differences in clinical outcomes of MERS-CoV and SARS-CoV-2 infections.

Higher virulence of swine H1N2 influenza viruses containing avian-origin HA and 2009 pandemic PA and NP in pigs and mice.

Pigs are capable of harbouring influenza A viruses of human and avian origin in their respiratory tracts and thus act as an important intermediary host to generate novel influenza viruses with pandemic potential by genetic reassortment between the two viruses. Here, we show that two distinct H1N2 swine influenza viruses contain avian-like or classical swine-like hemagglutinins with polymerase acidic (PA) and nucleoprotein (NP) genes from 2009 pandemic H1N1 influenza viruses that were found to be circulating in Korean pigs in 2018. Swine H1N2 influenza virus containing an avian-like hemagglutinin gene had enhanced pathogenicity, causing severe interstitial pneumonia in infected pigs and mice. The mortality rate of mice infected with swine H1N2 influenza virus containing an avian-like hemagglutinin gene was higher by 100% when compared to that of mice infected with swine H1N2 influenza virus harbouring classical swine-like hemagglutinin. Further, chemokines attracting inflammatory cells were strongly induced in lung tissues of pigs and mice infected by swine H1N2 influenza virus containing an avian-like hemagglutinin gene. In conclusion, it is necessary for the well-being of humans and pigs to closely monitor swine influenza viruses containing avian-like hemagglutinin with PA and NP genes from 2009 pandemic H1N1 influenza viruses.