Immunomodulator plasmid projected by systems biology as a candidate for the development of adjunctive therapy for respiratory syncytial virus infection

Autophagy and Inflammation: Regulatory Roles in Viral Infections

Autophagy is a highly conserved intracellular degradation pathway in eukaryotic organisms, playing an adaptive role in various pathophysiological processes throughout evolution. Inflammation is the immune system's response to external stimuli and tissue damage. However, persistent inflammatory reactions can lead to a range of inflammatory diseases and cancers. The interaction between autophagy and inflammation is particularly evident during viral infections. As a crucial regulator of inflammation, autophagy can either promote or inhibit the occurrence of inflammatory responses. In turn, inflammation can establish negative feedback loops by modulating autophagy to suppress excessive inflammatory reactions. This interaction is pivotal in the pathogenesis of viral diseases. Therefore, elucidating the regulatory roles of autophagy and inflammation in viral infections will significantly enhance our understanding of the mechanisms underlying related diseases. Furthermore, it will provide new insights and theoretical foundations for disease prevention, treatment, and drug development.

Inhibition of NF-κB/IL-33/ST2 Axis Ameliorates Acute Bronchiolitis Induced by Respiratory Syncytial Virus

Background/Aim

Bronchiolitis is a common acute lower respiratory tract infectious disease in infants. Respiratory syncytial virus (RSV) infection is one of the main causes. Bronchiolitis can lead to a significant increase in the incidence of asthma in young children, but the mechanism of bronchiolitis transforming into asthma is still unclear. The study was aimed at investigating the role of NF-κB/IL-33/ST2 axis on RSV-induced acute bronchiolitis.

Methods

A total of 40 infants diagnosed with acute bronchiolitis infected by RSV, and 20 normal infants were included in this study. BALB/c mice (6-8 weeks old, 20 ± 1.1 g) were used as study models. Enzyme-linked immunosorbent assay (ELISA), quantitative real time PCR, western blot analysis, immunohistochemical staining, and flow cytometry analysis were performed to examine relevant indicators.

Results

IL-33 level was significantly elevated, and Th1/Th2 ratio is imbalance after in infants with acute bronchiolitis. In vivo study, we found that NF-κB/IL-33/ST2 axis is mediated the Th2 cytokine levels and BAL cell number induced by RSV. Acute bronchiolitis induced by RSV in a mouse model is attenuated after inhibition of NF-κB/IL-33/ST2 pathway. Moreover, we also confirmed that macrophages are important sources of IL-33 and are regulated by NF-κB pathway in RSV-induced mice.

Conclusion

We confirmed that inhibition of NF-κB/IL-33/ST2 axis could attenuate acute bronchiolitis by RSV infected. Our findings not only demonstrate the potential role of IL-33 antibody in attenuating RSV-induced lung damage but also provide a new insight into better prevention of RSV-induced asthma by mediating NF-κB/IL-33/ST2 axis.

Virus genes and host correlates of pathology are markedly reduced during respiratory syncytial and influenza virus co-infection in BALB/c mice

Globally, influenza A virus (IAV) and respiratory syncytial virus (RSV) infection remain very high. There is also a high burden of IAV and RSV co-infection in developing countries. To develop universally protective vaccines against these infections, it is imperative that viral genes and immune correlates of pathology are elucidated. As such, we profiled virus genes expressions, histopathology and immunological responses of BALB/c mice infected with RSV and/or IAV in this study.

RSV A2 and/or influenza A/H3N2/Perth/16/09 (Pr/H3N2) were induced over a seven-day period in BALB/c mice. Anaesthetized BALB/c mice (12–14 g) were divided into six groups (15–20 mice per group), inoculated with 32 μl each of 3LD₅₀ Pr/H3N2 and/or 100 TCID₅₀ RSV. Two groups (R or I) received RSV or Pr/H3N2 intranasally. Prior infection with either RSV or Pr/H3N2 was followed with a second challenge of the other virus 24 hours post inoculation in RI and IR groups. Another set was exposed to the two viruses simultaneously (I + R group) while the last group served as healthy controls. Five to seven mice per group were euthanized at days 2, 4 and 7. Lung and spleen organs were harvested for virus genes quantitation and immune cells phenotyping respectively.

I + R group showed progressive downregulation of RSV F, G, NS1 and NS2 genes. IAV PB2 and M genes had high fold increase on day 2 and 4 post infections. However, by day 7 post infection, M and PB2 fold increase was lower. Also, increased proportions of NKT and T cell subsets were observed throughout the period in I + R group. Conversely, I group was characterized by reduced NKT cell counts and enhanced CD8 T cells levels while R group only showed an increased proportion of CD8 T cells towards the peak of infection.

This study shows that RSV and IAV co-infection lead to reduced virulence and pathology compared to single infections. This information is very useful in combinatorial RSV/IAV vaccine design and development.