Fig. 5

Strategies employed by viruses to evade the respiratory immune response. A. Disruption of Physical Barriers: Viruses breach respiratory barriers by I. degrading mucus, II. disrupting ciliary motility, and III. damaging epithelial tight junctions. B. Blockade of Immune Signaling: Viruses evade immune detection by IV. inhibiting PRRs. They also V. upregulate host receptors or VI. induce apoptosis. C. Suppression of Immune Cell Function: VII. Viruses impair DCs maturation and induce macrophage necrosis. D. Interference with Bioactive Mediators: VIII. Viruses inhibit IFN production and disrupt IFN signaling. E. Viral Mutational Escape: IX. Antigenic drift and spike protein mutations in virus variants evade neutralizing antibodies and reduce vaccine efficacy. RSV, respiratory syncytial virus; CD31, cluster of differentiation 31; HLA I, human leukocyte antigen class I; ACE2, angiotensin-converting enzyme 2; SA, sialic acid; CX3CR1, C-X3-C-motif chemokine receptor 1; NS1, non-structural protein 1; Nsp1, non-structural protein 1; Nsp13, non - structural protein 13; TBK1, TANK-binding kinase 1; PLPro, papain-like protease; ISG15, interferon-stimulated gene 15; IRF3, interferon regulatory factor 3; IAV, influenza A virus; IFNAR1, interferon-alpha / beta receptor 1; JAK, janus kinase; TYK2, tyrosine kinase 2; STAT1, signal transducer and activator of transcription 1; STAT2, signal transducer and activator of transcription 2; IRF9, interferon regulatory factor 9; RIPK1, receptor-interacting protein kinase 1; RIPK3,receptor-interacting protein kinase 3; MLKL, mixed-lineage kinase domain-like