Amino acid #mutations K54E and S154P in the #neuraminidase attenuate #H3N2 #canine #influenza virus in mice

 

ABSTRACT

Dogs are considered mixing vessels for influenza viruses, posing a pandemic potential via viral reassortment. Our previous studies indicated that the avian-origin H3N2 canine influenza virus (A/canine/Zhejiang/1/2010, abbreviated C1) is virulent in canine and mice. Furthermore, we found that the HA and NA genes of C1 share a close genetic relationship with an H3N2 avian influenza virus (A/duck/Shanghai/06/2009, abbreviated D6), but they exhibit distinct pathogenicity. However, the understanding mechanisms remain unclear. In the present study, we explored the genetic determinants that contribute to the different pathogenicity between the C1 and D6. By using the reverse genetics approaches, we rescued several single-gene and position-substituted reassortant viruses based on the C1. The replication in Madin–Darby canine kidney cells and pathogenic trial in mice showed that the neuraminidase (NA) gene played a critical role in C1 virulence. Further analysis demonstrated that the K54E and S154P mutations in NA significantly reduced NA enzymatic activity, impairing viral release from infected cells. Consequently, these mutant viruses lost their ability to infect mice. Overall, our findings identify two novel virulence determinants in NA and elucidate the mechanisms behind the distinct pathogenicity between the C1 and D6 in mice. These results may provide some new targets for H3N2 influenza virus vaccines and antiviral drug development.

Source: 

Link: https://www.microbiologyresearch.org/content/journal/jgv/10.1099/jgv.0.002223

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#Adaptation differences and mechanisms of #influenza viruses to ANP32 #proteins across #species

 

ABSTRACT

Avian influenza virus cross-species infection in humans poses a major threat to global public health. Species-specific differences between avian ANP32A and mammalian ANP32 proteins create a natural barrier against viral cross-species infection by directly impairing the functional interaction between the avian-origin viral RNA polymerase and mammalian ANP32 proteins, thereby restricting viral genome replication. The key to overcoming this barrier lies in the adaptation of viral RNA polymerase to host ANP32 family proteins. This mini-review summarizes the mechanisms and variations in influenza virus adaptation to ANP32 proteins across different species. Influenza viruses adapt to species-specific ANP32 proteins through various mutations and display distinct preferences for specific ANP32 family members within the same host. Additionally, alternative splicing variants of ANP32A within a single species further modulate viral RNA polymerase adaptability. Despite this diversity, the underlying interaction mechanism remains conserved: ANP32–polymerase binding is necessary but not sufficient for optimal polymerase activity. This interaction facilitates the formation of asymmetric polymerase dimers and specifically supports viral genome replication, while the step from cRNA to vRNA remains subject to species-specific restrictions. This explains the classic adaptive mechanism of the PB2 E627K mutation, which restores efficient viral genome replication through acid–base pairing with ANP32A. Furthermore, adaptive mutations in emerging strains such as H3N2 canine influenza virus and recent cases of H5N1 in dairy cows underscore the need for continuous viral surveillance and deeper mechanistic studies on virus–ANP32 interactions. Such research is strategically critical for advancing the One Health approach and mitigating future influenza pandemics.

Source: 

Link: https://journals.asm.org/doi/full/10.1128/jvi.01900-25?af=R

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#Mammalian #adaptation and zoonotic #risk of #influenza A viruses in companion #animals

 

Abstract

Importance

Since the early 2000s, companion animals emerged as unexpected players in influenza A virus ecology. Canine influenza viruses and the increasing detection of highly pathogenic avian influenza viruses in cats have raised concerns about their potential role as intermediate hosts for pandemic emergence. Their unique position at human-animal interface creates unprecedented opportunities for viral evolution and bidirectional transmission between humans and animals.

Observations

This review examined the transmission pathways and molecular adaptations of influenza A virus in companion animals. Cats primarily acquire infections through alimentary routes, including consumption of raw poultry and unpasteurized milk, as well as environmental exposure through hunting. Dogs transmit influenza viruses via respiratory droplets in high-density settings such as shelters and kennels. Canine influenza viruses demonstrate successful mammalian adaptation through accumulated mutations across multiple viral proteins, particularly in polymerase and hemagglutinin genes, enabling sustained dog-to-dog transmission. Feline isolates consistently exhibit mammalian adaptive mutations across geographically disparate outbreaks. Several molecular changes appear convergently in both species, suggesting shared evolutionary pressures at companion animal-human interface.

Conclusions and Relevance

Despite molecular evidence of active viral evolution, companion animals currently pose a limited pandemic risk owing to no sustained zoonotic transmission chains. Critical knowledge gaps remain regarding subclinical infection frequency, natural transmission efficiency, and host genetic factors that influence susceptibility. Surveillance should prioritize high-risk interfaces, including raw pet food supply chains and veterinary facilities, while maintaining the perspective of actual versus theoretical risks. Understanding companion animal influenza virus dynamics is essential for comprehensive pandemic preparedness strategies.

Source: 

Link: https://vetsci.org/DOIx.php?id=10.4142/jvs.25153

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Synergistic effects of PA (S184N) and #PB2 (E627K) #mutations on the increased pathogenicity of #H3N2 canine #influenza virus #infections in mice and #dogs

ABSTRACT

As companion animals, dogs are susceptible to various subtypes of influenza A virus (IAV), with the H3N2 and H3N8 subtypes of canine influenza virus (CIV) stably circulating among canines. Compared to the H3N8 CIV, the H3N2 CIV is more widely prevalent in canine populations and demonstrates increased adaptability to mammals, potentially facilitating cross-species transmission. Therefore, a comprehensive elucidation of the mechanisms underlying H3N2 CIV adaptation to mammals is imperative. In this study, we serially passaged the GD14-WT strain in murine lungs, successfully establishing a lethal H3N2 CIV infection model. From this model, we isolated the lethal strain GD14-MA and identified the key lethal mutations PA(S184N) and PB2(E627K). Moreover, the GD14-ma[PA(S184N)+PB2(E627K)] strain exhibited markedly enhanced pathogenicity in dogs. Viral titers in lung tissues from infected dogs and mice showed that GD14-ma[PA(S184N)+PB2(E627K)] does not increase its pathogenicity to mice and dogs by upregulating viral titers compared to the GD14-WT strain. Notably, sequence alignments across all H3N2 IAVs showed an increasing prevalence of the PA (S184N) and PB2 (E627K) mutations from avian to human hosts. Finally, single-cell RNA sequencing of infected mouse lung tissues showed that GD14-ma[PA(S184N)+PB2(E627K)] effectively evaded host antiviral responses, inducing a robust inflammatory reaction. Considering the recognized role of the PB2 (E627K) mutation in the mammalian adaptation of IAVs, our findings underscore the importance of ongoing surveillance for the PA (S184N) mutation in H3N2 IAVs.

IMPORTANCE

Since the 21st century, zoonotic viruses have frequently crossed species barriers, posing significant global public health challenges. Dogs are susceptible to various influenza A viruses (IAVs), particularly the H3N2 canine influenza virus (CIV), which has stably circulated and evolved to enhance its adaptability to mammals, including an increased affinity for the human-like SAα2,6-Gal receptor, posing a potential public health threat. Here, we simulated H3N2 CIV adaptation in mice, revealed that the synergistic PA(S184N) and PB2(E627K) mutations augment H3N2 CIV pathogenicity in dogs and mice, and elucidated the underlying mechanisms at the single-cell level. Our study provides molecular evidence for adapting the H3N2 CIV to mammals and underscores the importance of vigilant monitoring of genetic variations in H3N2 CIV.

Source: Journal of Virology, https://journals.asm.org/doi/full/10.1128/jvi.01984-24?af=R

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Meta-Analysis of #Seroprevalence and #Prevalence of #Influenza A Viruses (Subtypes #H3N2, #H3N8, and #H1N1) in #Dogs

Abstract

Influenza A is a zoonotic disease that affects dogs, pigs, horses, poultry, and birds. In this report, a meta-analysis according to PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) was conducted. Studies of influenza A viruses in dogs providing prevalence or seroprevalence in any location worldwide were included. The results in this study show that the seroprevalence for the H3N8 influenza subtype was 7.96% (95% CI: 2.03–16.8, p < 0.001), for the H3N2 subtype was 7.44% (95% CI: 4.51–10.5, p < 0.001), and for the H1N1 subtype was 3.10% (95% CI: 0.890–6.01, p < 0.001). In the case of the prevalence analysis, a prevalence of 0.395% (95% CI: 0.160–2.44) for the H3N8 subtype. For the H3N2 subtype, a prevalence of 17.8% (95% CI: 6.66–32.6, p < 0.001) was found. No publication bias was observed in the studies evaluating seroprevalence in the H3N2 and H1N1 subtypes. In the H3N8 subtype, Begg’s test indicated publication bias, but Egger’s test showed no bias. It is essential to know the approximate prevalence and seroprevalence worldwide of canine influenza, so this study reports the presence of influenza subtypes in dogs, placing this species as a reservoir for human, swine, equine, and avian influenza A viruses.

Source: Animals (Basel), https://www.mdpi.com/2076-2615/14/23/3467 

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