Chicken and duck myotubes are highly susceptible and permissive to influenza virus infection.
Bottom Line: Besides its primary function in movement and posture, skeletal muscle is a significant innate immune organ with the capacity to produce cytokines and chemokines and respond to proinflammatory cytokines.Infected chicken myotubes produced significantly higher levels of proinflammatory cytokines than did the corresponding duck cells.Our results indicate that avian skeletal muscle fibers of chicken and duck could be significant contributors to progeny production of highly pathogenic H5N1 viruses.
Affiliation: School of Veterinary Medicine and Science, University of Nottingham, Loughborough, Leicestershire, United Kingdom.Show MeSH
Related in: MedlinePlus
Mentions: Differentiated chicken and duck myotubes were infected with a LPAI H2N3 virus at a MOI of 1.0. Uninfected control chicken and duck cultures typically displayed extensive swirls of myotubes immunopositive for muscle-specific intermediate desmin filaments (Fig. 4A and E, respectively). At 24 h p.i., severe cytopathic damage was evident, with widespread rounding or detachment of chicken and duck myotubes (Fig. 4B and F, respectively). There were numerous sarcoplasmic blebs, which appeared as small membrane-lined vesicles associated with degenerating myotubes (Fig. 4C to D′ and G to H′, respectively). These blebs appeared to be apoptotic bodies, a feature well recognized in other cell types but not previously observed in myotubes undergoing apoptosis in vitro (41, 42). Concentrations of viral NP colocalized with sarcoplasmic blebs in both infected chicken and duck myotubes (Fig. 4D and D′ and H and H′, respectively). Similar cytopathic changes were observed in chicken and duck myotubes infected with HPAI H5N1 50-92 virus (Fig. 4J and L, respectively). To further examine the cytopathic changes in chicken and duck myotubes infected with LPAI H2N3 virus at a MOI of 1.0 for 24 h, PS membrane translocation (apoptotic change) was localized by annexin V-EGFP binding, visualized as green fluorescence (Fig. 4M to P). Some annexin V-EGFP-positive cells had lost their membrane integrity, as demonstrated by the uptake of the red nuclear fluorochrome PI, indicating late apoptosis or even necrosis. PI-labeled myonuclei showed chromatin condensation and/or fragmentation in chicken and duck myotubes (Fig. 4M and N, respectively). Similar apoptotic changes were also detected in infected chicken and duck myoblasts (Fig. 4O and P, respectively). Both chicken and duck myotube cultures displayed similar and significant activation of caspases 3 and 7 at 24 h and 48 h after infection (Fig. 4Q and Q′). In summary, extensive and severe chicken and duck myotube damage from LPAI and HPAI virus infections was accompanied by clear hallmarks of apoptosis and evidence of necrosis.
Affiliation: School of Veterinary Medicine and Science, University of Nottingham, Loughborough, Leicestershire, United Kingdom.