Deep spatial profiling of human COVID-19 brains reveals neuroinflammation with distinct microanatomical microglia-T-cell interactions.

COVID-19 can cause severe neurological symptoms, but the underlying pathophysiological mechanisms are unclear. Here, we interrogated the brain stems and olfactory bulbs in postmortem patients who had COVID-19 using imaging mass cytometry to understand the local immune response at a spatially resolved, high-dimensional, single-cell level and compared their immune map to non-COVID respiratory failure, multiple sclerosis, and control patients. We observed substantial immune activation in the central nervous system with pronounced neuropathology (astrocytosis, axonal damage, and blood-brain-barrier leakage) and detected viral antigen in ACE2-receptor-positive cells enriched in the vascular compartment. Microglial nodules and the perivascular compartment represented COVID-19-specific, microanatomic-immune niches with context-specific cellular interactions enriched for activated CD8+ T cells. Altered brain T-cell-microglial interactions were linked to clinical measures of systemic inflammation and disturbed hemostasis. This study identifies profound neuroinflammation with activation of innate and adaptive immune cells as correlates of COVID-19 neuropathology, with implications for potential therapeutic strategies.

Enhanced fitness of SARS-CoV-2 variant of concern Alpha but not Beta.

Emerging variants of concern (VOCs) are driving the COVID-19 pandemic1,2. Experimental assessments of replication and transmission of major VOCs and progenitors are needed to understand the mechanisms of replication and transmission of VOCs3. Here we show that the spike protein (S) from Alpha (also known as B.1.1.7) and Beta (B.1.351) VOCs had a greater affinity towards the human angiotensin-converting enzyme 2 (ACE2) receptor than that of the progenitor variant S(D614G) in vitro. Progenitor variant virus expressing S(D614G) (wt-S614G) and the Alpha variant showed similar replication kinetics in human nasal airway epithelial cultures, whereas the Beta variant was outcompeted by both. In vivo, competition experiments showed a clear fitness advantage of Alpha over wt-S614G in ferrets and two mouse models-the substitutions in S were major drivers of the fitness advantage. In hamsters, which support high viral replication levels, Alpha and wt-S614G showed similar fitness. By contrast, Beta was outcompeted by Alpha and wt-S614G in hamsters and in mice expressing human ACE2. Our study highlights the importance of using multiple models to characterize fitness of VOCs and demonstrates that Alpha is adapted for replication in the upper respiratory tract and shows enhanced transmission in vivo in restrictive models, whereas Beta does not overcome Alpha or wt-S614G in naive animals.

Author Correction: Relatives of rubella virus in diverse mammals.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Relatives of rubella virus in diverse mammals.

Since 1814, when rubella was first described, the origins of the disease and its causative agent, rubella virus (Matonaviridae: Rubivirus), have remained unclear1. Here we describe ruhugu virus and rustrela virus in Africa and Europe, respectively, which are, to our knowledge, the first known relatives of rubella virus. Ruhugu virus, which is the closest relative of rubella virus, was found in apparently healthy cyclops leaf-nosed bats (Hipposideros cyclops) in Uganda. Rustrela virus, which is an outgroup to the clade that comprises rubella and ruhugu viruses, was found in acutely encephalitic placental and marsupial animals at a zoo in Germany and in wild yellow-necked field mice (Apodemus flavicollis) at and near the zoo. Ruhugu and rustrela viruses share an identical genomic architecture with rubella virus2,3. The amino acid sequences of four putative B cell epitopes in the fusion (E1) protein of the rubella, ruhugu and rustrela viruses and two putative T cell epitopes in the capsid protein of the rubella and ruhugu viruses are moderately to highly conserved4-6. Modelling of E1 homotrimers in the post-fusion state predicts that ruhugu and rubella viruses have a similar capacity for fusion with the host-cell membrane5. Together, these findings show that some members of the family Matonaviridae can cross substantial barriers between host species and that rubella virus probably has a zoonotic origin. Our findings raise concerns about future zoonotic transmission of rubella-like viruses, but will facilitate comparative studies and animal models of rubella and congenital rubella syndrome.

Phenotypic effects of mutations observed in the neuraminidase of human origin H5N1 influenza A viruses.

Global spread and regional endemicity of H5Nx Goose/Guangdong avian influenza viruses (AIV) pose a continuous threat for poultry production and zoonotic, potentially pre-pandemic, transmission to humans. Little is known about the role of mutations in the viral neuraminidase (NA) that accompanied bird-to-human transmission to support AIV infection of mammals. Here, after detailed analysis of the NA sequence of human H5N1 viruses, we studied the role of A46D, L204M, S319F and S430G mutations in virus fitness in vitro and in vivo. Although H5N1 AIV carrying avian- or human-like NAs had similar replication efficiency in avian cells, human-like NA enhanced virus replication in human airway epithelia. The L204M substitution consistently reduced NA activity of H5N1 and nine other influenza viruses carrying NA of groups 1 and 2, indicating a universal effect. Compared to the avian ancestor, human-like H5N1 virus has less NA incorporated in the virion, reduced levels of viral NA RNA replication and NA expression. We also demonstrate increased accumulation of NA at the plasma membrane, reduced virus release and enhanced cell-to-cell spread. Furthermore, NA mutations increased virus binding to human-type receptors. While not affecting high virulence of H5N1 in chickens, the studied NA mutations modulated virulence and replication of H5N1 AIV in mice and to a lesser extent in ferrets. Together, mutations in the NA of human H5N1 viruses play different roles in infection of mammals without affecting virulence or transmission in chickens. These results are important to understand the genetic determinants for replication of AIV in mammals and should assist in the prediction of AIV with zoonotic potential.

Rustrela Virus in Wild Mountain Lion (Puma concolor) with Staggering Disease, Colorado, USA.

We identified a rustrela virus variant in a wild mountain lion (Puma concolor) in Colorado, USA. The animal had clinical signs and histologic lesions compatible with staggering disease. Considering its wide host range in Europe, rustrela virus should be considered as a cause for neurologic diseases among mammal species in North America.

Red knots in Europe: a dead end host species or a new niche for highly pathogenic avian influenza?

The 2020/2021 epidemic in Europe of highly pathogenic avian influenza virus (HPAIV) of subtype H5 surpassed all previously recorded European outbreaks in size, genotype constellations and reassortment frequency and continued into 2022 and 2023. The causative 2.3.4.4b viral lineage proved to be highly proficient with respect to reassortment with cocirculating low pathogenic avian influenza viruses and seems to establish an endemic status in northern Europe. A specific HPAIV reassortant of the subtype H5N3 was detected almost exclusively in red knots (Calidris canutus islandica) in December 2020. It caused systemic and rapidly fatal disease leading to a singular and self-limiting mass mortality affecting about 3500 birds in the German Wadden Sea, roughly 1 % of the entire flyway population of islandica red knots. Phylogenetic analyses revealed that the H5N3 reassortant very likely had formed in red knots and remained confined to this species. While mechanisms of virus circulation in potential reservoir species, dynamics of spill-over and reassortment events and the roles of environmental virus sources remain to be identified, the year-round infection pressure poses severe threats to endangered avian species and prompts adaptation of habitat and species conservation practices.

The role of PB1-F2 in adaptation of high pathogenicity avian influenza virus H7N7 in chickens.

Avian influenza viruses (AIV) of the H7N7 subtype are enzootic in the wild bird reservoir in Europe, cause infections in poultry, and have sporadically infected humans. The non-structural protein PB1-F2 is encoded in a second open frame in the polymerase segment PB1 and its sequence varies with the host of origin. While mammalian isolates predominantly carry truncated forms, avian isolates typically express full-length PB1-F2. PB1-F2 is a virulence factor of influenza viruses in mammals. It modulates the host immune response, causing immunopathology and increases pro-inflammatory responses. The role of full-length PB1-F2 in IAV pathogenesis as well as its impact on virus adaptation and virulence in poultry remains enigmatic. Here, we characterised recombinant high pathogenicity AIV (HPAIV) H7N7 expressing or lacking PB1-F2 in vitro and in vivo in chickens. In vitro, full-length PB1-F2 modulated viability of infected chicken fibroblasts by limiting apoptosis. In chickens, PB1-F2 promoted gastrointestinal tropism, as demonstrated by enhanced viral replication in the gut and increased cloacal shedding. PB1-F2's effects on cellular immunity however were marginal. Overall, chickens infected with full-length PB1-F2 virus survived for shorter periods, indicating that PB1-F2 is also a virulence factor in bird-adapted viruses.

Genetic Determinants for Virulence and Transmission of the Panzootic Avian Influenza Virus H5N8 Clade 2.3.4.4 in Pekin Ducks.

Waterfowl is the natural reservoir for avian influenza viruses (AIV), where the infection is mostly asymptomatic. In 2016, the panzootic high pathogenicity (HP) AIV H5N8 of clade 2.3.4.4B (designated H5N8-B) caused significant mortality in wild and domestic ducks, in stark contrast to the predecessor 2.3.4.4A virus from 2014 (designated H5N8-A). Here, we studied the genetic determinants for virulence and transmission of H5N8 clade 2.3.4.4 in Pekin ducks. While ducks inoculated with recombinant H5N8-A did not develop any clinical signs, H5N8-B-inoculated and cohoused ducks died after showing neurological signs. Swapping of the HA gene segments did not increase virulence of H5N8-A but abolished virulence and reduced systemic replication of H5N8-B. Only H5N8-A carrying H5N8-B HA, NP, and NS with or without NA exhibited high virulence in inoculated and contact ducks, similar to H5N8-B. Compared to H5N8-A, HA, NA, NS, and NP proteins of H5N8-B possess peculiar differences, which conferred increased receptor binding affinity, neuraminidase activity, efficiency to inhibit interferon-alpha induction, and replication in vitro, respectively. Taken together, this comprehensive study showed that HA is not the only virulence determinant of the panzootic H5N8-B in Pekin ducks, but NP, NS, and to a lesser extent NA were also necessary for the exhibition of high virulence in vivo. These proteins acted synergistically to increase receptor binding affinity, sialidase activity, interferon antagonism, and replication. This is the first ad-hoc study to investigate the mechanism underlying the high virulence of HPAIV in Pekin ducks. IMPORTANCE Since 2014, several waves of avian influenza virus (AIV) H5N8 of clade 2.3.4.4 occurred globally on unprecedented levels. Unlike viruses in the first wave in 2014-2015 (H5N8-A), viruses in 2015-2016 (H5N8-B) exhibited unusually high pathogenicity (HP) in wild and domestic ducks. Here, we found that the high virulence of H5N8-B in Pekin ducks could be attributed to multiple factors in combination, namely, hemagglutinin (HA), neuraminidase (NA), nucleoprotein (NP), and nonstructural protein 1 (NS1). Compared to H5N8-A, H5N8-B possesses distinct genetic and biological properties including increased HA receptor-binding affinity and neuraminidase activity. Likewise, H5N8-B NS1 and NP were more efficient to inhibit interferon induction and enhance replication in primary duck cells, respectively. These results indicate the polygenic trait of virulence of HPAIV in domestic ducks and the altered biological properties of the HPAIV H5N8 clade 2.3.4.4B. These findings may explain the unusual high mortality in Pekin ducks during the panzootic H5N8 outbreaks.

Evidence for Different Virulence Determinants and Host Response after Infection of Turkeys and Chickens with Highly Pathogenic H7N1 Avian Influenza Virus.

Wild birds are the reservoir for all avian influenza viruses (AIV). In poultry, the transition from low pathogenic (LP) AIV of H5 and H7 subtypes to highly pathogenic (HP) AIV is accompanied mainly by changing the hemagglutinin (HA) monobasic cleavage site (CS) to a polybasic motif (pCS). Galliformes, including turkeys and chickens, succumb with high morbidity and mortality to HPAIV infections, although turkeys appear more vulnerable than chickens. Surprisingly, the genetic determinants for virulence and pathogenesis of HPAIV in turkeys are largely unknown. Here, we determined the genetic markers for virulence and transmission of HPAIV H7N1 in turkeys, and we explored the host responses in this species compared to those of chickens. We found that recombinant LPAIV H7N1 carrying pCS was avirulent in chickens but exhibited high virulence in turkeys, indicating that virulence determinants vary in these two galliform species. A transcriptome analysis indicated that turkeys mount a different host response than do chickens, particularly from genes involved in RNA metabolism and the immune response. Furthermore, we found that the HA glycosylation at residue 123, acquired by LP viruses shortly after transmission from wild birds and preceding the transition from LP to HP, had a role in virus fitness and virulence in chickens, though it was not a prerequisite for high virulence in turkeys. Together, these findings indicate variable virulence determinants and host responses in two closely related galliformes, turkeys and chickens, after infection with HPAIV H7N1. These results could explain the higher vulnerability to HPAIV of turkeys compared to chickens. IMPORTANCE Infection with HPAIV in chickens and turkeys, two closely related galliform species, results in severe disease and death. Although the presence of a polybasic cleavage site (pCS) in the hemagglutinin of AIV is a major virulence determinant for the transition of LPAIV to HPAIV, there are knowledge gaps on the genetic determinants (including pCS) and the host responses in turkeys compared to chickens. Here, we found that the pCS alone was sufficient for the transformation of a LP H7N1 into a HPAIV in turkeys but not in chickens. We also noticed that turkeys exhibited a different host response to an HPAIV infection, namely, a widespread downregulation of host gene expression associated with protein synthesis and the immune response. These results are important for a better understanding of the evolution of HPAIV from LPAIV and of the different outcomes and the pathomechanisms of HPAIV infections in chickens and turkeys.

Neuraminidase-associated plasminogen recruitment enables systemic spread of natural avian Influenza viruses H3N1.

Repeated outbreaks due to H3N1 low pathogenicity avian influenza viruses (LPAIV) in Belgium were associated with unusually high mortality in chicken in 2019. Those events caused considerable economic losses and prompted restriction measures normally implemented for eradicating high pathogenicity avian influenza viruses (HPAIV). Initial pathology investigations and infection studies suggested this virus to be able to replicate systemically, being very atypical for H3 LPAIV. Here, we investigate the pathogenesis of this H3N1 virus and propose a mechanism explaining its unusual systemic replication capability. By intravenous and intracerebral inoculation in chicken, we demonstrate systemic spread of this virus, extending to the central nervous system. Endoproteolytic viral hemagglutinin (HA) protein activation by either tissue-restricted serine peptidases or ubiquitous subtilisin-like proteases is the functional hallmark distinguishing (H5 or H7) LPAIV from HPAIV. However, luciferase reporter assays show that HA cleavage in case of the H3N1 strain in contrast to the HPAIV is not processed by intracellular proteases. Yet the H3N1 virus replicates efficiently in cell culture without trypsin, unlike LPAIVs. Moreover, this trypsin-independent virus replication is inhibited by 6-aminohexanoic acid, a plasmin inhibitor. Correspondingly, in silico analysis indicates that plasminogen is recruitable by the viral neuraminidase for proteolytic activation due to the loss of a strongly conserved N-glycosylation site at position 130. This mutation was shown responsible for plasminogen recruitment and neurovirulence of the mouse brain-passaged laboratory strain A/WSN/33 (H1N1). In conclusion, our findings provide good evidence in natural chicken strains for N1 neuraminidase-operated recruitment of plasminogen, enabling systemic replication leading to an unusual high pathogenicity phenotype. Such a gain of function in naturally occurring AIVs representing an established human influenza HA-subtype raises concerns over potential zoonotic threats.

Characterization of experimental Shuni virus infection in the mouse.

Shuni virus (SHUV), an orthobunyavirus of the Simbu serogroup, was initially isolated in Nigeria in the 1960s, further detected in other African countries and in the Middle East, and is now endemic in Israel. Transmitted by blood-sucking insects, SHUV infection is associated with neurological disease in cattle and horses, and with abortion, stillbirth, or the birth of malformed offspring in ruminants. Surveillance studies also indicated a zoonotic potential. This study aimed to test the susceptibility of the well-characterized interferon (IFN)-α/ß receptor knock-out mouse model (Ifnar-/-), to identify target cells, and to describe the neuropathological features. Ifnar-/-mice were subcutaneously infected with two different SHUV strains, including a strain isolated from the brain of a heifer showing neurological signs. The second strain represented a natural deletion mutant exhibiting a loss of function of the S-segment-encoded nonstructural protein NSs, which counteracts the host's IFN response. Here it is shown that Ifnar-/-mice are susceptible to both SHUV strains and can develop fatal disease. Histological examination confirmed meningoencephalomyelitis in mice as described in cattle with natural and experimental infections. RNA in situ hybridization was applied using RNA Scope™ for SHUV detection. Target cells identified included neurons and astrocytes, as well as macrophages in the spleen and gut-associated lymphoid tissue. Thus, this mouse model is particularly beneficial for the evaluation of virulence determinants in the pathogenesis of SHUV infection in animals.

Preferential Selection and Contribution of Non-Structural Protein 1 (NS1) to the Efficient Transmission of Panzootic Avian Influenza H5N8 Virus Clades 2.3.4.4A and B in Chickens and Ducks.

Highly pathogenic avian influenza virus H5N8 clade 2.3.4.4 caused outbreaks in poultry at an unprecedented global scale. The virus was spread by wild birds in Asia in two waves: clade 2.3.4.4A in 2014/2015 and clade 2.3.4.4B from 2016 up to today. Both clades were highly virulent in chickens, but only clade B viruses exhibited high virulence in ducks. Viral factors which contribute to virulence and transmission of these panzootic H5N8 2.3.4.4 viruses are largely unknown. The NS1 protein, typically composed of 230 amino acids (aa), is a multifunctional protein which is also a pathogenicity factor. Here, we studied the evolutionary trajectory of H5N8 NS1 proteins from 2013 to 2019 and their role in the fitness of H5N8 viruses in chickens and ducks. Sequence analysis and in vitro experiments indicated that clade 2.3.4.4A and clade 2.3.4.4B viruses have a preference for NS1 of 237 aa and 217 aa, respectively, over NS1 of 230 aa. NS217 was exclusively seen in domestic and wild birds in Europe. The extension of the NS1 C terminus (CTE) of clade B virus reduced virus transmission and replication in chickens and ducks and partially impaired the systemic tropism to the endothelium in ducks. Conversely, lower impact on fitness of clade A virus was observed. Remarkably, the NS1 of clade A and clade B, regardless of length, was efficient in blocking interferon (IFN) induction in infected chickens, and changes in the NS1 C terminus reduced the efficiency for interferon antagonism. Together, the NS1 C terminus contributes to the efficient transmission and high fitness of H5N8 viruses in chickens and ducks. IMPORTANCE The panzootic H5N8 highly pathogenic avian influenza viruses of clade 2.3.4.4A and 2.3.4.4B devastated the poultry industry globally. Clade 2.3.4.4A was predominant in 2014/2015 while clade 2.3.4.4B was widely spread in 2016/2017. The two clades exhibited different pathotypes in ducks. Virus factors contributing to virulence and transmission are largely unknown. The NS1 protein is typically composed of 230 amino acids (aa) and is an essential interferon (IFN) antagonist. Here, we found that the NS1 protein of clade 2.3.4.4A preferentially evolved toward long NS1 with 237 aa, while clade 2.3.4.4B evolved toward shorter NS1 with 217 aa (exclusively found in Europe) due to stop codons in the C terminus (CTE). We showed that the NS1 CTE of H5N8 is required for efficient virus replication, transmission, and endotheliotropism in ducks. In chickens, H5N8 NS1 evolved toward higher efficiency to block IFN response. These findings may explain the preferential pattern for short NS1 and high fitness of the panzootic H5N8 in birds.

Susceptibility of Raccoon Dogs for Experimental SARS-CoV-2 Infection.

Raccoon dogs might have been intermediate hosts for severe acute respiratory syndrome-associated coronavirus in 2002-2004. We demonstrated susceptibility of raccoon dogs to severe acute respiratory syndrome coronavirus 2 infection and transmission to in-contact animals. Infected animals had no signs of illness. Virus replication and tissue lesions occurred in the nasal conchae.

Aging and Senescence in Canine Testes.

Senescent cells accumulate with age but tissue-based studies of senescent cells are limited to selected organs from humans, mice, and primates. Cell culture and xenograft studies have indicated that senescent cells in the microenvironment may play a role in tumor proliferation via paracrine activities. Dogs develop age-related conditions, including in the testis, but cellular senescence has not been confirmed. We hypothesized that senescent cells accumulate with age in canine testes and in the microenvironment of testicular tumors. We tested the expression of the established senescence markers γH2AX and p21 on normal formalin-fixed, paraffin-embedded testes from 15 young dogs (<18 months of age) and 15 old dogs (7-15 years of age) and correlated the findings with age-dependent morphological changes. A statistically significant age-dependent increase in the percentage of p21-expressing cells was observed for testicular fibroblasts (4-fold) and Leydig cells (8-fold). However, p21-expressing cells were still a rare event. In contrast, the percentage of γH2AX-positive cells did not increase with age. P21- and γH2AX-expressing cells were rare in the microenvironments of tumors. Age-dependent morphological changes included an increased mean number of Leydig cells per intertubular triangle (2.95-fold) and a decreased spermatogenesis score. To our surprise, no age-related changes were recorded for interstitial collagen content, mean tubular diameter, and epithelial area. Opposed to our expectations based on previous in vitro data, we did not identify evidence of a correlation between age-associated accumulation of senescent cells and testicular tumor development. Understanding the role of the microenvironment in senescence obviously remains a challenging task.

Endothelial depletion of murine SRF/MRTF provokes intracerebral hemorrhagic stroke.

Intracerebral hemorrhagic stroke and vascular dementia are age- and hypertension-associated manifestations of human cerebral small vessel disease (SVD). Cerebral microvessels are formed by endothelial cells (ECs), which are connected through tight junctions, adherens junctions, and stabilizing basement membrane structures. These endothelial connections ensure both vessel stability and blood-brain barrier (BBB) functions, the latter enabling selective exchange of ions, bioactive molecules, and cells between the bloodstream and brain tissue. Srf(iECKO) mice, permitting conditional EC-specific depletion of the transcription factor Serum Response Factor (SRF), suffer from loss of BBB integrity and intracerebral hemorrhaging. Cerebral microbleeds and larger hemorrhages developed upon postnatal and adult depletion of either SRF or its cofactors Myocardin Related Transcription Factor (MRTF-A/-B), revealing essential requirements of ongoing SRF/MRTF activity for maintenance of cerebral small vessel integrity. In vivo magnetic resonance imaging allowed detection, localization, and time-resolved quantification of BBB permeability and hemorrhage formation in Srf(iECKO) brains. At the molecular level, direct and indirect SRF/MRTF target genes, encoding structural components of tight junctions (Claudins and ZO proteins), adherens junctions (VE-cadherin, α-Actinin), and the basement membrane (Collagen IV), were down-regulated upon SRF depletion. These results identify SRF and its MRTF cofactors as major transcriptional regulators of EC junctional stability, guaranteeing physiological functions of the cerebral microvasculature. We hypothesize that impairments in SRF/MRTF activity contribute to human SVD pathology.

Soluble CD200 Correlates With Interleukin-6 Levels in Sera of COPD Patients: Potential Implication of the CD200/CD200R Axis in the Disease Course.

BACKGROUND: COPD represents a multifactorial lung disorder with high morbidity and mortality. Despite intensive research concerning the underlying disease mechanisms, the involvement of the CD200/CD200R axis in supporting or preventing the onset of COPD has not yet been addressed. Since the CD200/CD200R axis is crucially implicated in the maintenance of pulmonary immune homeostasis, we hypothesized that it might be involved in controlling the onset of COPD. METHODS: To address this, we analyzed the serum samples from COPD patients and normal controls for soluble (s) CD200 and correlated the data to COPD-relevant clinical parameters. In addition, basic studies were conducted in CD200-deficient and wild-type mice in which COPD-like inflammation was induced with elastase/LPS followed by lung and serum component analysis. RESULTS: We observed a positive correlation between serum sCD200 and IL-6 levels as well as a trend toward a negative correlation of sCD200 with vitamin D3 in COPD patients. Further investigations in mice revealed that despite elevated serum concentration of MMP-9 in CD200KO mice, the early onset of COPD-like lung inflammation was similar in CD200-deficient and wild-type animals in terms of immune cell infiltration, emphysematous changes, and mucus overproduction. CONCLUSIONS: While our murine studies suggest that the co-inhibitory molecule CD200 does not appear to play a prominent role in the early onset of COPD-like features, correlation of sCD200 serum levels with COPD-related parameters in humans with established disease revealed that the CD200/CD200R axis may be mechanistically linked to the disease course in COPD patients.

Avian influenza virus hemagglutinins H2, H4, H8, and H14 support a highly pathogenic phenotype.

High-pathogenic avian influenza viruses (HPAIVs) evolve from low-pathogenic precursors specifying the HA serotypes H5 or H7 by acquisition of a polybasic HA cleavage site. As the reason for this serotype restriction has remained unclear, we aimed to distinguish between compatibility of a polybasic cleavage site with H5/H7 HA only and unique predisposition of these two serotypes for insertion mutations. To this end, we introduced a polybasic cleavage site into the HA of several low-pathogenic avian strains with serotypes H1, H2, H3, H4, H6, H8, H10, H11, H14, or H15, and rescued HA reassortants after cotransfection with the genes from either a low-pathogenic H9N2 or high-pathogenic H5N1 strain. Oculonasal inoculation with those reassortants resulted in varying pathogenicity in chicken. Recombinants containing the engineered H2, H4, H8, or H14 in the HPAIV background were lethal and exhibited i.v. pathogenicity indices of 2.79, 2.37, 2.85, and 2.61, respectively, equivalent to naturally occurring H5 or H7 HPAIV. Moreover, the H2, H4, and H8 reassortants were transmitted to some contact chickens. The H2 reassortant gained two mutations in the M2 proton channel gate region, which is affected in some HPAIVs of various origins. Taken together, in the presence of a polybasic HA cleavage site, non-H5/H7 HA can support a highly pathogenic phenotype in the appropriate viral background, indicating requirement for further adaptation. Therefore, the restriction of natural HPAIV to serotypes H5 and H7 is likely a result of their unique predisposition for acquisition of a polybasic HA cleavage site.

Liver and kidney concentrations of strontium, barium, cadmium, copper, zinc, manganese, chromium, antimony, selenium and lead in cats.

BACKGROUND: In order to provide new knowledge on the storage of strontium (Sr), barium (Ba), cadmium (Cd), copper (Cu), zinc (Zn), manganese (Mn), chromium (Cr), antimony (Sb), selenium (Se) and lead (Pb) in the feline organism, we measured the concentrations of these elements in the liver, renal cortex and renal medulla, evaluating also the impact of age, sex or the occurrence of a chronic kidney disease (CKD). The element concentrations in the tissues of 47 cats (22 male; 25 female; aged between 2 months and 18 years) were measured using inductively coupled plasma mass spectrometry. RESULTS: Cu, Zn and Mn were the highest in the liver, followed by the renal cortex and the renal medulla. The Cd concentrations were lower in the renal medulla compared to the renal cortex and the liver, and Sr was higher in the renal medulla compared to the liver. The Se concentrations in the cortex of the kidneys were higher than in the medulla of the kidneys and in the liver. Higher Cd concentrations were measured in the renal cortex of female cats, while no further gender-related differences were observed. Except for Cr, Sb and Se, age-dependencies were detected for the storage of all elements. The occurrence of a CKD also affected the storage of the elements, with lower concentrations of Ba (renal medulla), Zn (renal cortex; renal medulla) and Mn (liver; renal medulla), but higher Cd concentrations (liver; renal cortex) in diseased cats. CONCLUSIONS: In conclusion, the present results provide new information on the accumulation of specific elements in the feline liver and kidneys, demonstrating a dependency on age and an impaired kidney function, but not on the sex of the animals.

Leaderless foot-and-mouth disease virus serotype O did not cause clinical disease and failed to establish a persistent infection in cattle.

The foot-and-mouth disease virus (FMDV) Leader proteinase Lpro inhibits host mRNA translation and blocks the interferon response which promotes viral survival. Lpro is not required for viral replication in vitro but serotype A FMDV lacking Lpro has been shown to be attenuated in cattle and pigs. However, it is not known, whether leaderless viruses can cause persistent infection in vivo after simulated natural infection and whether the attenuated phenotype is the same in other serotypes. We have generated an FMDV O/FRA/1/2001 variant lacking most of the Lpro coding region (ΔLb). Cattle were inoculated intranasopharyngeally and observed for 35 days to determine if O FRA/1/2001 ΔLb is attenuated during the acute phase of infection and whether it can maintain a persistent infection in the upper respiratory tract. We found that although this leaderless virus can replicate in vitro in different cell lines, it is unable to establish an acute infection with vesicular lesions and viral shedding nor is it able to persistently infect bovine pharyngeal tissues.