Cell Rep . Multiple transatlantic incursions of highly pathogenic avian influenza clade 2.3.4.4b A(H5N5) virus into North America and spillover to mammals

[tetano]

Cell Rep


. 2024 Jul 13;43(7):114479.
doi: 10.1016/j.celrep.2024.114479. Online ahead of print. Multiple transatlantic incursions of highly pathogenic avian influenza clade 2.3.4.4b A(H5N5) virus into North America and spillover to mammals

Cassidy N G Erdelyan ¹ , Ahmed Kandeil ² , Anthony V Signore ¹ , Megan E B Jones ³ , Peter Vogel ⁴ , Konstantin Andreev ⁵ , Cathrine Arnason Bøe ⁶ , Britt Gjerset ⁶ , Tamiru N Alkie ¹ , Carmencita Yason ⁷ , Tamiko Hisanaga ¹ , Daniel Sullivan ¹ , Oliver Lung ⁸ , Laura Bourque ³ , Ifeoluwa Ayilara ¹ , Lemarie Pama ¹ , Trushar Jeevan ⁵ , John Franks ⁵ , Jeremy C Jones ⁵ , Jon P Seiler ⁵ , Lance Miller ⁵ , Samira Mubareka ⁹ , Richard J Webby ¹⁰ , Yohannes Berhane ¹¹



Affiliations

• PMID: 39003741
• DOI: 10.1016/j.celrep.2024.114479

Free article Abstract

Highly pathogenic avian influenza (HPAI) viruses have spread at an unprecedented scale, leading to mass mortalities in birds and mammals. In 2023, a transatlantic incursion of HPAI A(H5N5) viruses into North America was detected, followed shortly thereafter by a mammalian detection. As these A(H5N5) viruses were similar to contemporary viruses described in Eurasia, the transatlantic spread of A(H5N5) viruses was most likely facilitated by pelagic seabirds. Some of the Canadian A(H5N5) viruses from birds and mammals possessed the PB2-E627K substitution known to facilitate adaptation to mammals. Ferrets inoculated with A(H5N5) viruses showed rapid, severe disease onset, with some evidence of direct contact transmission. However, these viruses have maintained receptor binding traits of avian influenza viruses and were susceptible to oseltamivir and zanamivir. Understanding the factors influencing the virulence and transmission of A(H5N5) in migratory birds and mammals is critical to minimize impacts on wildlife and public health.

Keywords: A(H5N5); CP: Microbiology; HPAI; Sable Island; antiviral susceptibility; avian influenza; clade 2.3.4.4b; contact transmission; ferret model; wildlife transmission.

[Commonground]

The above is now Open Access - July 23, 2024

Some excerpts

Antiviral susceptibility

The susceptibility of the A(H5N5) viruses to NA inhibitors (NAIs) and the cap-dependent endonuclease inhibitor (CENI) baloxavir was assessed by genotypic and phenotypic approaches. Analysis of all A(H5N5) virus sequences from 2021 through 2023 did not identify any of the established NAI resistance markers. All 41 viruses isolated in Canada in 2023 contained the NA-I117T substitution that has been previously shown to confer reduced inhibition (RI) to oseltamivir/zanamivir in HPAI A(H5N1) viruses.49 Substitutions in the polymerase acidic (PA) protein associated with RI by CENI (PA-E23 G/K, PA-K34R, PA-A36V, PA-A37T, PA-I38 M/T, and PA-E199G) were absent from the Canadian A(H5N5) viruses. One virus isolated from a swan in Sweden (A/Mute Swan/Sweden/SVA210303SZ0392/KN000806/Kal/2021) had the PA-E199G substitution, which may cause >3-fold reduced sensitivity to baloxavir.50 The Canadian viruses did have a PA-T40A substitution that is located close to the highly conserved isoleucine residue (I38) in the PA catalytic site. While this substitution is also prevalent among European A(H5N5) viruses (24.1%; 13/54), the frequencies are low among HPAI A(H5N1) (0.07%; 4/6,162), and seasonal H3N2 (0.02%; 9/38,741) viruses.

The in vitro susceptibility of A/Raccoon/PEI/FAV-0193-1/2023 and A/American_Crow/PEI/FAV-0035-6/2023 to the NAIs oseltamivir, zanamivir, and peramivir was determined by NA inhibition fluorometric assays using fluorogenic 2′-(4-methylumbelliferyl)-α-d-N-acetylneuraminic acid substrate.51 Plaque reduction assays and Influenza replication inhibition NA-based assays were used for measuring sensitivity to baloxavir.52 Phenotypic testing confirmed both viruses to be susceptible to antivirals with half-maximal inhibitory concentration/half-maximal effective concentration values being ≤2-fold higher than clade 2.3.4.4.b reference viruses (Table S3). As such, NA-I117T and PA-T40A do not confer RI to NAIs and CENI, respectively, in the context of A(H5N5) viruses.

Receptor binding properties

Both A(H5N5) isolates examined preferentially bound sialic acid receptors with a 3′SLN-linked sialic acid (preferred AIV receptor), rather than 6′SLN-linked sialic acid (preferred human influenza virus receptor)

Four GBBGs infected with A(H5N5) virus were detected at the end of January and beginning of February 2023 in Cape Cod, Massachusetts, a peninsula that extends into the Atlantic Ocean.5

[well we got a mammal now!].

While infections with IAV containing N5 have been described in seals (H4N5)89 and swine (H10N5),90 to our knowledge there have been no previously reported cases of A(H5N5) infection in mammals. In the present study, we have 7 confirmed cases of mammalian A(H5N5) infections leading to deaths (4 raccoons, 2 red foxes, 1 striped skunk). While it is concerning that individual mammalian-adaptive mutations were detected in these animals, there was no evidence of mammal-to-mammal transmission. The high proportion of Canadian A(H5N5) detections in mammals (7 of the 41, 17%, total detections) is surprising. In contrast, of the 2,118 Canadian A(H5N1) detections, only 96 were from mammals (4.5%).

Ferrets have been the benchmark model for assessing risk to humans. In our hands, the A(H5N5)-Δstalk viruses were highly virulent in ferrets (100% mortality; Figure 3B) and transmitted, albeit inefficiently, to direct contact animals (as measured by clinical signs and seroconversion). Inefficient viral detection in nasal washes of directly contacted ferrets, together with observed clinical signs, including severe diarrhea, neurologic signs, and weight loss, suggest that infection may have initiated in the lower respiratory tract through small infectious droplets or extrapulmonary sites like the digestive system or nervous system, although tissue was not available to confirm this. A total of three amino acid substitutions were found in A/Raccoon/PEI/FAV-0193-1/2023 compared to A/American_Crow/PEI/FAV-0035-6/2023: PB2 (T271A), PB1 (N328K), and HA (I200V). These three mutations have previously been characterized with mammalian adaptation of IAVs and are possibly linked to the more robust systemic replication of A/Raccoon/PEI/FAV-0193-1/2023 in ferrets. Transmission of the A(H5N5)-Δstalk viruses is consistent with previous reports linking HA-T156A to airborne transmission among ferrets^87,91 and guinea pigs.⁹² Similar ferret studies with the EA A(H5N1) viruses A/Fancy Chicken/Newfoundland/FAV-0033/2021 and A/American Wigeon/South Carolina/22-000345-001/2021 led to no mortality or transmission in infected ferrets.⁹³

The A(H5N5)-Δstalk viruses appear to be neurotropic in mammals, as seen from the histologic lesions and immunostaining in ferret brain tissues (Figures 4 and 5). Neuroinvasion is known to occur in mammalian A(H5Nx) infection,⁹⁴ and our ferret data are consistent with other cases of Canadian mesocarnivores from which clade 2.3.4.4b A(H5N1) viruses were isolated from brain samples.⁵⁵ While the A(H5N5)-Δstalk viruses exhibit high mortality in the ferret model, they remained susceptible to antivirals such as NAIs and CENI (Table S3). Although the NA subtypes differ, results are consistent with clade 2.3.4.4b A(H5N1) resistance data.⁹⁵

The A(H5N5)-Δstalk viruses appear to be neurotropic in mammals, as seen from the histologic lesions and immunostaining in ferret brain tissues (Figures 4 and 5). Neuroinvasion is known to occur in mammalian A(H5Nx) infection,⁹⁴ and our ferret data are consistent with other cases of Canadian mesocarnivores from which clade 2.3.4.4b A(H5N1) viruses were isolated from brain samples.⁵⁵ While the A(H5N5)-Δstalk viruses exhibit high mortality in the ferret model, they remained susceptible to antivirals such as NAIs and CENI (Table S3). Although the NA subtypes differ, results are consistent with clade 2.3.4.4b A(H5N1) resistance data.⁹⁵

https://www.cell.com/cell-reports/fu...showall%3Dtrue