Biology subjects

Di Genova, C.

Publications and source records attributed to Di Genova, C..

5 recordsLinked to original sources

bioRxiv2025

Generation of cloned sheep lacking galactose-α1,3-galactose and Nglycolylneuraminic acid antigens

Livestock have long been regarded as a potential source of donor organs to alleviate the global organ shortage for transplantation. Sheep have a similar physiology and anatomy to humans, providing the standard model for demonstrating biocompatibility and performance of biological heart valves to obtain regulatory approval for their use in transplantation. Like most mammals, sheep cells contain two well-characterized carbohydrate epitopes, galactose-1,3-galactose (-Gal) and N-glycolylneuraminic acid (Neu5Gc), which are absent in humans. Formation of these xenoantigens is catalysed by two enzymes, namely (1,3) galactosyltransferase (GGTA1) and CMP-Neu5Gc hydroxylase (CMAH), respectively. Towards generating new sheep models, we used Cas9-mediated genome editing in both male and female ovine fetal fibroblasts to knockout (KO) both alleles of CMAH and GGTA1. Selected double KO (DKO) fibroblast strains were used for somatic cell transfer cloning to produce blastocysts that were transferred into gestational surrogate ewes. Following transfer of 128 male and 40 female cloned blastocysts, 6 male and 8 female lambs were born, however, none of the males survived. Molecular analyses of cells from the five surviving ewes confirmed their compound heterozygous state, resulting in a functional DKO phenotype and subsequent immune rejection of embryonic tissues during natural breeding with wild-type rams. This new DKO sheep model better mimics the human immune status, offering greater physiological relevance for preclinical testing of biological heart valves, alleviation of red meat allergy syndrome due to the presence of dietary xenoantigens, and an alternative source of donor organs that may be culturally more widely accepted than pigs.

cell biology↗

bioRxiv2025

Detection of clade 2.3.4.4b H5N1 high pathogenicity avian influenza virus in a sheep in Great Britain, 2025

Clade 2.3.4.4b H5N1 high pathogenicity avian influenza virus (HPAIV) continues to pose a significant global threat, affecting wild and domestic avian populations, and mammalian species. In early 2024, H5N1 HPAIV was detected in dairy cattle in the United States of America, where it has continued to circulate, with sporadic detections also reported in other ruminant species. The detection of high viral loads in milk from infected cattle, has resulted in several human infections, underscoring the zoonotic potential of these viruses. In response, several countries have intensified surveillance in non-avian species to evaluate the potential for undetected viral circulation in captive mammals. In Great Britain, bulk milk tank testing of cattle and targeted surveillance of captive mammalian species on an infected premises is undertaken in accordance with the outcome of a rapid risk assessment undertaken to determine the epidemiological links between the poultry and captive mammals. A result of this testing was the first recorded detection of clade 2.3.4.4b H5N1 HPAIV in a sheep in March 2025, identified on an infected poultry premises in Great Britain. An initial seropositive result in a single ewe triggered further investigation, confirming serological positivity across repeated sampling and the presence of viral RNA in milk samples. This detection was confined to a single animal and was likely attributable to proximity to infected poultry and a presumed heavily contaminated environment. The implications of this ruminant detection are discussed in the context of interspecies transmission and surveillance strategies.

microbiology↗

bioRxiv2025

Pigeons exhibit low susceptibility and poor transmission capacity for H5N1 clade 2.3.4.4b high pathogenicity avian influenza virus

The ongoing panzootic of H5N1 high pathogenicity avian influenza virus (HPAIV) has caused the deaths of over half a billion wild birds and poultry, and has led to spillover events in both wild and domestic mammals, alongside sporadic human infections. A key driver of this panzootic is the apparent high viral fitness across diverse avian species, which facilitates an increased interface between wild and domestic species. Columbiformes (pigeons and doves) are commonly found on poultry premises, yet little is known about their potential role in contemporary HPAIV disease ecology. Here we investigated the epidemiological role of pigeons (Columba livia) by determining their susceptibility using decreasing doses of clade 2.3.4.4b H5N1 HPAIV (genotype AB). We investigated infection outcomes and transmission potential between pigeons and to chickens. Following direct inoculation, pigeons did not develop clinical signs, and only those inoculated with the highest dose shed viral RNA or seroconverted to H5N1-AB, revealing a MID50 of 105 EID50. Even in the high-dose group, only low-level shedding and environmental contamination was observed, and low-level viral RNA were present in the tissues of directly inoculated pigeons, with no distinct pathological lesions. Pigeons did not transmit the virus to pigeons or chickens placed in direct contact. We observed distinct differences in sialic acid receptor distribution in the pigeon respiratory tract compared to chickens and ducks. Together, these findings suggest that pigeons have low susceptibility to clade 2.3.4.4b H5N1 HPAIV and are unlikely to contribute significantly to virus maintenance, transmission to poultry, or zoonotic infection.

microbiology↗

bioRxiv2025

Investigating Factors Driving Shifts in Subtype Dominance within H5Nx Clade 2.3.4.4b High-Pathogenicity Avian Influenza viruses

H5Nx clade 2.3.4.4b high-pathogenicity avian influenza viruses (HPAIVs) have decimated wild bird and poultry populations globally since the autumn of 2020. In the United Kingdom (UK) and in continental Europe, the H5N8 subtype predominated during the first epizootic wave of 2020/21, with few detections of H5N1. However, during the second (2021/22) and third (2022/23) epizootic waves, H5N1 was the dominant subtype. The rapid shift in dominance from H5N8 to H5N1 was likely driven by a combination of virological, immunological, and/or host-related factors. In this study, we compared viral fitness and immunological responses in ducks, a key reservoir species, using dominant genotypes of H5N1 (genotype AB) and H5N8 (genotype A) from the second wave. While viral shedding dynamics were similar for both viruses, H5N8 was more pathogenic. Antigenic analysis of post-infection duck sera revealed that the haemagglutinin (HA) protein was antigenically similar across clade 2.3.4.4b H5 HPAIVs, but neuraminidase (NA) proteins displayed different patterns of cross-reactivity. We also modelled a scenario where ducks were pre-exposed to H5N1 (genotype C) or H5N8 (genotype A) from the first wave and subsequently challenged with either homologous or heterologous subtypes from the second wave (genotype AB or A). Despite the absence of seroconversion, pre-exposure to different subtypes resulted in varying clinical outcomes following challenge. These findings indicate that both viral and immunological factors likely played significant roles in the emergence and spread of H5Nx HPAIVs in wild bird populations.

microbiology↗

bioRxiv2023

Clade 2.3.4.4b H5N1 high pathogenicity avian influenza virus (HPAIV) from the 2021/22 epizootic is highly duck adapted and poorly adapted to chickens

The 2021/2022 epizootic of high pathogenicity avian influenza (HPAIV) remains one of the largest ever in the UK, being caused by a clade 2.3.4.4b H5N1 HPAIV. This epizootic affected more than 145 poultry premises, most likely through independent incursion from infected wild birds, supported by more than 1700 individual detections of H5N1 from wild bird mortalities. Here an H5N1 HPAIV, representative of this epizootic (H5N1-21), was used to investigate its virulence, pathogenesis and transmission in layer chickens and pekin ducks, two species of epidemiological importance. We inoculated both avian species with decreasing H5N1-21 doses. The virus was highly infectious in ducks, with high infection levels and accompanying shedding of viral RNA, even in ducks inoculated with the lowest dose, reflecting the strong waterfowl adaptation of the clade 2.3.4.4 HPAIVs. Duck-to-duck transmission was very efficient, coupled with high environmental contamination. H5N1-21 was frequently detected in water sources, serving as likely sources of infection for ducks, but inhalable dust and aerosols represented low transmission risks. In contrast, chickens inoculated with the highest dose exhibited lower rates of infection compared to ducks. There was no evidence for experimental H5N1-21 transmission to any naive chickens, in two stocking density scenarios, coupled with minimal and infrequent contamination being detected in the chicken environment. Systemic viral dissemination to multiple organs reflected the pathogenesis and high mortalities in both species. In summary, the H5N1-21 virus is highly infectious and transmissible in anseriformes, yet comparatively poorly adapted to galliformes, supporting strong host preferences for wild waterfowl. Key environmental matrices were also identified as being important in the epidemiological spread of this virus during the continuing epizootic.

microbiology↗