Swine-to-Ferret Transmission of Antigenically Drifted Contemporary Swine H3N2 Influenza A Virus Is an Indicator of Zoonotic Risk to Humans

Human-to-swine transmission of influenza A (H3N2) virus occurs repeatedly and plays a critical role in swine influenza A virus (IAV) evolution and diversity. Human seasonal H3 IAVs were introduced from human-to-swine in the 1990s in the United States and classified as 1990.1 and 1990.4 lineages; the 1990.4 lineage diversified into 1990.4.A-F clades. Additional introductions occurred in the 2010s, establishing the 2010.1 and 2010.2 lineages. Human zoonotic cases with swine IAV, known as variant viruses, have occurred from the 1990.4 and 2010.1 lineages, highlighting a public health concern. If a variant virus is antigenically drifted from current human seasonal vaccine (HuVac) strains, it may be chosen as a candidate virus vaccine (CVV) for pandemic preparedness purposes. We assessed the zoonotic risk of US swine H3N2 strains by performing phylogenetic analyses of recent swine H3 strains to identify the major contemporary circulating genetic clades. Representatives were tested in hemagglutination inhibition assays with ferret post-infection antisera raised against existing CVVs or HuVac viruses. The 1990.1, 1990.4.A, and 1990.4.B.2 clade viruses displayed significant loss in cross-reactivity to CVV and HuVac antisera, and interspecies transmission potential was subsequently investigated in a pig-to-ferret transmission study. Strains from the three lineages were transmitted from pigs to ferrets via respiratory droplets, but there were differential shedding profiles. These data suggest that existing CVVs may offer limited protection against swine H3N2 infection, and that contemporary 1990.4.A viruses represent a specific concern given their widespread circulation among swine in the United States and association with multiple zoonotic cases.

Pathogenesis and transmission of human seasonal and swine-origin A(H1) influenza viruses in the ferret model

Influenza A viruses (IAVs) in the swine reservoir constantly evolve, resulting in expanding genetic and antigenic diversity of strains that occasionally cause infections in humans and pose a threat of emerging as a strain capable of human-to-human transmission. For these reasons, there is an ongoing need for surveillance and characterization of newly emerging strains to aid pandemic preparedness efforts, particularly for the selection of candidate vaccine viruses and conducting risk assessments. Here, we performed a parallel comparison of the pathogenesis and transmission of genetically and antigenically diverse swine-origin A(H1N1) variant (v) and A(H1N2)v, and human seasonal A(H1N1)pdm09 IAVs using the ferret model. Both groups of viruses were capable of replication in the ferret upper respiratory tract; however, variant viruses were more frequently isolated from the lower respiratory tract as compared to the human-adapted viruses. Regardless of virus origin, observed clinical signs of infection differed greatly between strains, with some viruses causing nasal discharge, sneezing and, in some instances, diarrhea in ferrets. The most striking difference between the viruses was the ability to transmit through the air. Human-adapted viruses were capable of airborne transmission between all ferret pairs. In contrast, only one out of the four tested variant viruses was able to transmit via the air as efficiently as the human-adapted viruses. Overall, this work highlights the need for sustained monitoring of emerging swine IAVs to identify strains of concern such as those that are antigenically different from vaccine strains and that possess adaptations required for efficient respiratory droplet transmission in mammals.

Avian Influenza A(H7N2) Virus in Human Exposed to Sick Cats, New York, USA, 2016

An outbreak of influenza A(H7N2) virus in cats in a shelter in New York, NY, USA, resulted in zoonotic transmission. Virus isolated from the infected human was closely related to virus isolated from a cat; both were related to low pathogenicity avian influenza A(H7N2) viruses detected in the United States during the early 2000s.

Antigenic characterization of highly pathogenic avian influenza A(H5N1) viruses with chicken and ferret antisera reveals clade-dependent variation in hemagglutination inhibition profiles

Highly pathogenic avian influenza (HPAI) A(H5N1) viruses pose a significant economic burden to the poultry industry worldwide and have pandemic potential. Poultry vaccination against HPAI A(H5N1) viruses has been an important component of HPAI control measures and has been performed in Vietnam since 2005. To systematically assess antigenic matching of current vaccines to circulating field variants, we produced a panel of chicken and ferret antisera raised against historical and contemporary Vietnamese reference viruses representing clade variants that were detected between 2001 and 2014. The antisera were used for hemagglutination inhibition (HI) assays to generate data sets for analysis by antigenic cartography, allowing for a direct comparison of results from chicken or ferret antisera. HI antigenic maps, developed with antisera from both hosts, revealed varying patterns of antigenic relationships and clustering of viruses that were dependent on the clade of viruses analyzed. Antigenic relationships between existing poultry vaccines and circulating field viruses were also aligned with in vivo protection profiles determined by previously reported vaccine challenge studies. Our results establish the feasibility and utility of HPAI A(H5N1) antigenic characterization using chicken antisera and support further experimental and modeling studies to investigate quantitative relationships between genetic variation, antigenic drift and correlates of poultry vaccine protection in vivo.

Assessment of Molecular, Antigenic, and Pathological Features of Canine Influenza A(H3N2) Viruses That Emerged in the United States

Background

A single subtype of canine influenza virus (CIV), A(H3N8), was circulating in the United States until a new subtype, A(H3N2), was detected in Illinois in spring 2015. Since then, this CIV has caused thousands of infections in dogs in multiple states.

Methods

In this study, genetic and antigenic properties of the new CIV were evaluated. In addition, structural and glycan array binding features of the recombinant hemagglutinin were determined. Replication kinetics in human airway cells and pathogenesis and transmissibility in animal models were also assessed.

Results

A(H3N2) CIVs maintained molecular and antigenic features related to low pathogenicity avian influenza A(H3N2) viruses and were distinct from A(H3N8) CIVs. The structural and glycan array binding profile confirmed these findings and revealed avian-like receptor-binding specificity. While replication kinetics in human airway epithelial cells was on par with that of seasonal influenza viruses, mild-to-moderate disease was observed in infected mice and ferrets, and the virus was inefficiently transmitted among cohoused ferrets.

Conclusions

Further adaptation is needed for A(H3N2) CIVs to present a likely threat to humans. However, the potential for coinfection of dogs and possible reassortment of human and other animal influenza A viruses presents an ongoing risk to public health.

Shifting Clade Distribution, Reassortment, and Emergence of New Subtypes of Highly Pathogenic Avian Influenza A(H5) Viruses Collected from Vietnamese Poultry from 2012 to 2015

Whole-genome sequences of representative highly pathogenic avian influenza A(H5) viruses from Vietnam were generated, comprising samples from poultry outbreaks and active market surveillance collected from January 2012 to August 2015. Six hemagglutinin gene clades were characterized. Clade 1.1.2 was predominant in southern Mekong provinces throughout 2012 and 2013 but gradually disappeared and was not detected after April 2014. Clade 2.3.2.1c viruses spread rapidly during 2012 and were detected in the south and center of the country. A number of clade 1.1.2 and 2.3.2.1c interclade reassortant viruses were detected with different combinations of internal genes derived from 2.3.2.1a and 2.3.2.1b viruses, indicating extensive cocirculation. Although reassortment generated genetic diversity at the genotype level, there was relatively little genetic drift within the individual gene segments, suggesting genetic stasis over recent years. Antigenically, clade 1.1.2, 2.3.2.1a, 2.3.2.1b, and 2.3.2.1c viruses remained related to earlier viruses and WHO-recommended prepandemic vaccine strains representing these clades. Clade 7.2 viruses, although detected in only low numbers, were the exception, as indicated by introduction of a genetically and antigenically diverse strain in 2013. Clade 2.3.4.4 viruses (H5N1 and H5N6) were likely introduced in April 2014 and appeared to gain dominance across northern and central regions. Antigenic analyses of clade 2.3.4.4 viruses compared to existing clade 2.3.4 candidate vaccine viruses (CVV) indicated the need for an updated vaccine virus. A/Sichuan/26221/2014 (H5N6) virus was developed, and ferret antisera generated against this virus were demonstrated to inhibit some but not all clade 2.3.4.4 viruses, suggesting consideration of alternative clade 2.3.4.4 CVVs.IMPORTANCE Highly pathogenic avian influenza (HPAI) A(H5) viruses have circulated continuously in Vietnam since 2003, resulting in hundreds of poultry outbreaks and sporadic human infections. Despite a significant reduction in the number of human infections in recent years, poultry outbreaks continue to occur and the virus continues to diversify. Vaccination of poultry has been used as a means to control the spread and impact of the virus, but due to the diversity and changing distribution of antigenically distinct viruses, the utility of vaccines in the face of mismatched circulating strains remains questionable. This study assessed the putative amino acid changes in viruses leading to antigenic variability, underscoring the complexity of vaccine selection for both veterinary and public health purposes. Given the overlapping geographic distributions of multiple, antigenically distinct clades of HPAI A(H5) viruses in Vietnam, the vaccine efficacy of bivalent poultry vaccine formulations should be tested in the future.

Expression and function of the LIM homeodomain protein Apterous during embryonic brain development of Drosophila

We analyzed the expression and function of the LIM-homeodomain transcription factor Apterous (Ap ) in embryonic brain development of Drosophila. Expression of Ap in the embryonic brain begins at early stage 12 and is subsequently found in approximately 200 protocerebral neurons and in 4 deutocerebral neurons. Brain glia do not express Ap. Most of the Ap-expressing neurons are interneurons and project their axons across the midline to the contralateral hemisphere; a smaller subset projects their axons into the ventral nerve cord. A few Ap-expressing neurons project to the ring gland, suggesting that they are neurosecretory cells. In ap loss-of-function mutants, some of the protocerebral and deutocerebral interneurons that express Ap in the wild type show axon pathfinding errors and fasciculation defects in the brain, notably in the fascicles of the brain commissure. In contrast, the interneurons that project to the ring gland do not appear to be affected in ap mutants. Thus, in brain development, Ap is required for correct axon guidance and fasciculation of interneurons, and Ap-expressing cells may also be involved in the brain neuroendocrine system.

Chip is an essential cofactor for apterous in the regulation of axon guidance in Drosophila

LIM-homeodomain transcription factors are expressed in subsets of neurons and are required for correct axon guidance and neurotransmitter identity. The LIM-homeodomain family member Apterous requires the LIM-binding protein Chip to execute patterned outgrowth of the Drosophila wing. To determine whether Chip is a general cofactor for diverse LIM-homeodomain functions in vivo, we studied its role in the embryonic nervous system. Loss-of-function Chip mutations cause defects in neurotransmitter production that mimic apterous and islet mutants. Chip is also required cell-autonomously by Apterous-expressing neurons for proper axon guidance, and requires both a homodimerization domain and a LIM interaction domain to function appropriately. Using a Chip/Apterous chimeric molecule lacking domains normally required for their interaction, we reconstituted the complex and rescued the axon guidance defects of apterous mutants, of Chip mutants and of embryos doubly mutant for both apterous and Chip. Our results indicate that Chip participates in a range of developmental programs controlled by LIM-homeodomain proteins and that a tetrameric complex comprising two Apterous molecules bridged by a Chip homodimer is the functional unit through which Apterous acts during neuronal differentiation.

Chip and apterous physically interact to form a functional complex during Drosophila development

LIM homeodomain (LIM-HD) proteins play key roles in a variety of developmental processes throughout the animal kingdom. Here we show that the LIM-binding protein Chip acts as a cofactor for the Drosophila LIM-HD family member Apterous (Ap) in wing development. We define the domains of Chip required for LIM-HD binding and for homodimerization and show that mutant proteins deleted for these domains act in a dominant-negative fashion to disrupt Ap function. Our results support a model for multimeric complexes containing Chip and Ap in transcriptional regulation. This model is confirmed by the activity of a chimeric fusion between Chip and Ap that reconstitutes the complex and rescues the ap mutant phenotype.

A LIM-homeodomain combinatorial code for motor-neuron pathway selection

Different classes of vertebrate motor neuron that innervate distinct muscle targets express unique combinations of LIM-homeodomain transcription factors, suggesting that a combinatorial code of LIM-homeodomain proteins may underlie the control of motor-neuron pathway selection. Studies of LIM-homeodomain genes in mouse, Drosophila melanogaster and Caenorhabditis elegans have revealed functions of these genes in neuronal survival, axon guidance, neurotransmitter expression and neuronal function, but, to our knowledge, none of these studies have addressed the issue of a functional code. Here we study two members of this gene family in Drosophila, namely lim3, the homologue of the vertebrate Lhx3 and Lhx4 genes, and islet, the homologue of the vertebrate Isl1 and Is12 genes. We show that Drosophila lim3 is expressed by a specific subset of islet-expressing motor neurons and that mutating or misexpressing lim3 switches motor-neuron projections predictably. Our results provide evidence that lim3 and islet constitute a combinatorial code that generates distinct motor-neuron identities.

Cell type-specific regulation of the Drosophila FMRF-NH2 neuropeptide gene by Apterous, a LIM homeodomain transcription factor

We describe the direct and cell-specific regulation of the Drosophila FMRFa neuropeptide gene by Apterous, a LIM homeodomain transcription factor. dFMRFa and Apterous are expressed in partially overlapping subsets of neurons, including two of the seventeen dFMRFa cell types, the Tv neuroendocrine cells and the SP2 interneurons. Apterous contributes to the initiation of dFMRFa expression in Tv neurons, but not in those dFMRFa neurons that do not express Apterous. Apterous is not required for Tv neuron survival or morphological differentiation. Apterous contributes to the maintenance of dFMRFa expression by postembryonic Tv neurons, although the strength of its regulation is diminished. Apterous regulation of dFMRFa expression includes direct mechanisms, although ectopic Apterous does not induce ectopic dFMRFa. These findings show that, for a subset of neurons that share a common neurotransmitter phenotype, the Apterous LIM homeoprotein helps define neurotransmitter expression with very limited effects on other aspects of differentiation.

Function and specificity of LIM domains in Drosophila nervous system and wing development

LIM domains are found in a variety of proteins, including cytoplasmic and nuclear LIM-only proteins, LIM-homeodomain (LIM-HD) transcription factors and LIM-kinases. Although the ability of LIM domains to interact with other proteins has been clearly established in vitro and in cultured cells, their in vivo function is unknown. Here we use Drosophila to test the roles of the LIM domains of the LIM-HD family member Apterous (Ap) in wing and nervous system development. Using a rescuing assay of the ap mutant phenotype, we have found that the LIM domains are essential for Ap function. Furthermore, expression of LIM domains alone can act in a dominant-negative fashion to disrupt Ap function. The Ap LIM domains can be replaced by those of another family member to generate normal wing structure, but LIM domains are not interchangeable during axon pathfinding of the Ap neurons. This suggests that the Ap LIM domains mediate different protein interactions in different developmental processes, and that LIM domains can participate in conferring specificity of target gene selection.

The Drosophila islet gene governs axon pathfinding and neurotransmitter identity

We have isolated the Drosophila homolog of the vertebrate islet-1 and islet-2 genes, two members of the LIM homeodomain family implicated in the transcriptional control of motor neuronal differentiation. Similar to vertebrates, Drosophila islet is expressed in a discrete subset of embryonic motor neurons and interneurons that includes the dopaminergic and serotonergic cells of the ventral nerve cord. In contrast to mouse where mutation of islet-1 leads to loss of neurons due to programmed cell death, Drosophila islet is not required for neuron survival. Instead, loss of islet function causes defects in axon pathfinding and targeting plus loss of dopamine and serotonin synthesis. Ectopic expression of islet induces both specific alterations in pathfinding and changes in neurotransmitter identity. These findings indicate that islet coordinately controls two distinct aspects of neuronal identity.

Structural and concentration effects on the deposition of tricyclic antidepressants in human hair

In order to elucidate the possibility of a long-term compliance analysis the hair samples of 56 patients, who were under a permanent treatment with tricyclic antidepressants, were analyzed for amitriptyline, clomipramine, doxepine, imipramine and maprotiline as well as their nor-metabolites. The hair concentrations varied between 0.4 and 40 ng/mg with no strong difference between the five drugs. In comparison to the therapeutic plasma levels described in literature the nor-metabolites always accumulate less in hair than drugs. No correlation was found between the hair concentration and the daily dose. The investigation of the full hair length in 3-cm sections for several examples of all five drugs shows that they can be detected in normally kept hair at least 1 year after intake.

Effect of pigmentation on the drug deposition in hair of grey-haired subjects

The hair samples of 15 grizzled patients with a permanent medical treatment by amitriptyline, carbamazepine, chlorprothixene, diclofenac, doxepine, indomethacine, maprotiline or metoclopramide, or with a chronic heroin and cocaine abuse were separated into white and pigmented fibers and both fractions were independently investigated by GC-MS. The drugs were found in pigmented fibers as well as in white fibers, but the concentrations in the white fibers were smaller than in the pigmented ones for the most of the samples investigated. The concentration ratio of the drugs or their metabolites in both hair fractions (white/pigmented) was found to be between 0.09 and 1.57 (mean 0.70, 30 concentration pairs). There are large differences in this ratio between different subjects with the same drug, whereas for different drugs in the same subject in many cases similar ratios were measured. As a reason a different grade of pigmentation of the hair and the influence of the drug structure are discussed. From these results it follows that the natural hair colour is an important parameter in the evaluation of drug concentration in hair.

Motoneuron fate specification revealed by patterned LIM homeobox gene expression in embryonic zebrafish

In zebrafish, individual primary motoneurons can be uniquely identified by their characteristic cell body positions and axonal projection patterns. The fate of individual primary motoneurons remains plastic until just prior to axogenesis when they become committed to particular identities. We find that distinct primary motoneurons express particular combinations of LIM homeobox genes. Expression precedes axogenesis as well as commitment, suggesting that LIM homeobox genes may contribute to the specification of motoneuronal fates. By transplanting them to new spinal cord positions, we demonstrate that primary motoneurons can initiate a new program of LIM homeobox gene expression, as well as the morphological features appropriate for the new position. We conclude that the patterned distribution of different primary motoneuronal types within the zebrafish spinal cord follows the patterned expression of LIM homeobox genes, and that this reflects a highly resolved system of positional information controlling gene transcription.

Islet expression of Rhombotin and Isl-1 suggests cell type specific exposure of LIM-domain epitopes

The homeodomain protein Isl-1 and the proto-oncogene Rhombotin (a LIM-only protein), share a double zinc-binding LIM domain and have both been implicated in neural and possibly endocrine development. Isl-1 is expressed in all endocrine cell-types of the islet of Langerhans while Rhombotin mRNA expression was reported in rat insulinoma cells. We have cloned and sequenced Rhombotin cDNA from rat insulinoma (99.4% identical to human and mouse sequences) and demonstrate that it is expressed in normal islets, intestinal tissue, and testis, in addition to the brain; but absent in all other organs tested. Rhombotin mRNA is expressed in phenotypically distinct islet tumours (α-, β, and δ-tumours) at levels comparable to that of normal islets. Antisera raised against two distinct epitopes contained within a short synthetic peptide representing part of the N-terminal LIM domain of Rhombotin surprisingly stain α- and δ-cells, respectively, on sections of rat pancreas. Rhombotin is undetectable by immunocytochemistry using LIM-domain antisera on intact monolayer islet tumor cells or transfected fibroblasts while readily detectable when equipped with a FLAG epitope, as detected with FLAG antiserum. In contrast, recombinant FLAG-Rhombotin is efficiently recognised by Western blotting or immunoprecipitation with all LIM-specific antisera. Almost identical results were obtained with LIM-specific versus homeodomain/C-terminal Isl-1 antisera staining α-cell cytoplasm or all islet nuclei, respectively. We conclude that Rhombotin in addition to Isl-1 is expressed in the islet of Langerhans and propose that the differential staining patterns obtained with antisera towards the LIM domains versus flanking epitopes of both proteins reflect (1) cell-specific protein-protein interactions of these domains or, alternatively, (2) islet cell type specific expression of novel homologous LIM domain proteins.

Control of neuronal pathway selection by the Drosophila LIM homeodomain gene apterous

The Drosophila apterous gene encodes a LIM homeodomain protein expressed embryonically in a small subset of differentiating neurons. To establish the identity of these neurons and to study the role of apterous in their development, we made apterous promoter fusions to an axon-targeted reporter gene. We found that all apterous-expressing neurons are interneurons that choose a single pathway within the developing central nervous system. In apterous mutants, these neurons choose incorrect pathways and fail to fasciculate with one another. Our results indicate that apterous functions to control neuronal pathway selection and suggest that other vertebrate and invertebrate members of the LIM homeodomain class of proteins may serve similar functions.

Zebrafish primary neurons initiate expression of the LIM homeodomain protein Isl-1 at the end of gastrulation

Isl-1 has previously been established as the earliest marker of developing chicken spinal motor neurons where it is regulated by inductive signals from the floorplate and notochord. We now report that, in zebrafish, the expression of Isl-1 is initiated in Rohon-Beard cells, primary motor neurons, interneurons and cranial ganglia, hours before the neural tube itself is formed. The expression is initiated simultaneously in the Rohon-Beard cells and the primary motor neurons, at the axial level of the presumptive first somite. The Isl-1-expressing motor neurons appear on either side of the ventral midline whereas the interneurons and Rohon-Beard cells initiate expression while located at the edge of the germinal shield. Isl-1 expression is initiated in these cells before the formation of a differentiated notochord. Isl-1 is expressed in the various functional classes of primary neurons at 24 hours postfertilization. This selective expression of a homeodomain protein in the primary neurons implies that these neurons share a common program of early development and that they have evolved and been selected for as a coordinated system. One of the functions of the primary neurons is to send long axons which pioneer the major axon tracts in the zebrafish embryo. An evolutionary conserved functional role for Isl-1 in the expression of the pioneering phenotype of the primary neurons is suggested.

Early stages of motor neuron differentiation revealed by expression of homeobox gene Islet-1

Motor neurons in the embryonic chick spinal cord express a homeobox gene, Islet-1, soon after their final mitotic division and before the appearance of other differentiated motor neuron properties. The expression of Islet-1 by neural cells is regulated by inductive signals from the floor plate and notochord. These results establish Islet-1 as the earliest marker of developing motor neurons. The molecular nature of the Islet-1 protein suggests that it may be involved in the establishment of motor neuron fate.

The homeodomain LIM protein Isl-1 is expressed in subsets of neurons and endocrine cells in the adult rat

We have used immunocytochemical methods to localize the homeodomain LIM protein Isl-1 in the adult rat. Isl-1 immunoreactivity is expressed in polypeptide hormone-producing cells of the endocrine system, in neurons of the peripheral nervous system, and in a subset of brain nuclei. Isl-1 is also expressed in a subset of motoneurons in the spinal cord and brain stem, but not in regions of the central nervous system involved in sensory function or in neocortical areas. The pattern of expression of Isl-1 suggests that this gene may be involved in the specification and maintenance of differentiated phenotypical properties of these cells.

Novel insulin promoter- and enhancer-binding proteins that discriminate between pancreatic alpha- and beta-cells

In the mouse insulin is first detected on embryonic day 12 (e12) in a subpopulation of the cells that on e10 start to produce glucagon. During the continued embryonic development, the number of cells that coexpress the two hormones is gradually decreased, and in adults the expression of these two hormone genes is segregated to the beta- and alpha-cells. To begin to understand the process of terminal differentiation that restricts insulin gene expression to beta-cells, we have assayed for the presence of nuclear proteins that interact with transcriptional regulatory sequences of the rat insulin I gene in pancreatic alpha- and beta-cell lines. All except one of the previously identified insulin enhancer-binding proteins were found to be present in both cell types. A new insulin promoter-binding protein, IPF1, which was present in beta-cells but absent in alpha-cells, was identified. The beta-cell specificity of IPF1 implies that the insulin promoter is involved in the restriction of insulin gene expression to the beta-cells. The binding sites for IPF1 and the beta-cell-specific enhancer-binding protein IEF2 are both recognized by the previously isolated homeodomain-containing LIM protein isl-1, but these three proteins were all shown to be different entities.

Insulin gene enhancer binding protein Isl-1 is a member of a novel class of proteins containing both a homeo- and a Cys-His domain

The activity of the rat insulin I gene enhancer is mainly dependent on two cis-acting protein-binding domains. Here we report the isolation of a complementary DNA encoding a protein, Isl-1, that binds to one of these domains. Isl-1 contains a homeodomain with greatest similarity to those of the Caenorhabditis elegans proteins encoded by mec-3 and lin-11. In addition, Isl-1, like the lin-11 and mec-3 gene products, contains a novel Cys-His domain which is reminiscent of known metal-binding regions. Together these proteins define a novel class of proteins containing both a homeo- and a Cys His-domain. Isl-1 is preferentially expressed in cells of pancreatic endocrine origin. If the structural homologies between Isl-1 and the C. elegans gene products reflect functional similarities, a role for Isl-1 in the development of pancreatic endocrine cells could be envisaged.