Identification of the first human gyrovirus, a virus related to chicken anemia virus

Molecular analysis of Gyrovirus galga1 variants identified from the sera of dogs and cats in China

Gyrovirus galga1 (GyVg1), a member of the Anelloviridae family and Gyrovirus genus, has been detected in chicken and human tissue samples. In this study, the DNA of GyVg1-related gyroviruses in the sera of six dogs and three cats from Central and Eastern China was identified using PCR. Alignment analysis between the nine obtained and reference GyVg1 strains revealed that the genome identity ranged from 99.20% (DOG03 and DOG04 strains) to 96.17% (DOG01 and DOG06 strains). Six recombination events were predicted in multiple strains, including DOG01, DOG05, DOG06, CAT01, CAT02, and CAT03. The predicted major and minor parents of DOG05 came from Brazil. The DOG06 strain is potentially recombined from strains originating from humans and cats, whereas DOG01 is potentially recombined from G17 (ferret-originated) and Ave3 (chicken-originated), indicating that transmissions across species and regions may occur. Sixteen representative amino acid mutation sites were identified: nine in VP1 (12 R/H, 114S/N, 123I/M, 167 L/P, 231 P/S, 237 P/L, 243 R/W, 335 T/A, and 444S/N), four in VP2 (81 A/P, 103 R/H, 223 R/G, and 228 A/T), and three in VP3 (38 M/I, 61 A/T, and 65 V/A). These mutations were only harbored in strains identified in dogs and cats in this study. Whether this is related to host tropism needs further investigation. In this study, GyVg1 was identified in the sera of dogs and cats, and the molecular characteristics prompted the attention of public health.

Genetic heterogeneity and potential recombination across hosts of Gyrovirus galga1 in central and eastern China during 2021 to 2024

Gyrovirus galga1 (GyVg1), formerly known as AGV2, was initially identified in chickens in southern Brazil. The prevalence of GyVg1 from 2021 to 2024 in 28 out of the 63 poultry farms located in Jiangsu, Anhui, Henan, Hunan, Shandong, and Hubei provinces in eastern and central China was detected via PCR. The complete genomes of the 28 strains were sequenced and exhibited a full length of 2,376 bp. Similarity analysis of these strains did not suggest definite correlation with evolutionary branching and geographical distribution. Compared with the reference GyVg1 strains, HN2202 shared the highest similarity of 99.71% with HLJ1511 (chicken-originated) from northeastern China in 2015 to 2016. Recombination analysis revealed that AH2102 was a potential recombinant of peafowl-originated HN2019-PF1 and chicken-originated HLJ1506-2, whereas HN2304 was a recombinant of peafowl-originated HN2019-PF1 and the Hungarian ferret strain G13. Mutation site analysis of the capsid protein revealed that highly mutated regions occurred between sites 288 to 316 and 383 to 419. These results indicate that GyVg1 may have undergone an interspecies transmission, which involved complex mutations and recombination. This study may provide a reference for subsequent investigations targeting the molecular epidemiology and viral evolution of GyVg1.

Prevalence and phylogenetic analysis of Gyrovirus galga 1 in southern China from 2020 to 2022

Since 2011, the Gyrovirus galga 1 (GyVg1, previously recognized as avian gyrovirus 2) strain has extensively been detected worldwide. However, because there are no up-to-date reports of examining the distribution of GyVg1 in flocks in southern China, the epidemiology of this virus is unknown. To investigate the prevalence and genetic evolution of GyVg1, a total of 2,077 field samples collected from 113 chicken farms in 6 provinces in southern China during 2020 to 2022 were tested. Among them, 315 samples (315/2,077, 15.17%) were positive for GyVg1 by PCR. The positive rate of GyVg1 detection between different regions of southern China ranged from 11.69% (Guangdong) to 22.46% (Yunnan). The correlation between GyVg1 prevalence and sample source groups was analyzed, the results showing that the highest seroprevalence of GyVg1 was observed in visceral tissues (27.34%, 187/684), significantly higher (P < 0.05) than that of feather shafts (17.22%, 31/180), serums (8.85%, 78/881), and fecal (5.72%, 19/332). Additionally, the complete genomes of 10 GyVg1 strains were sequenced and analyzed, which showed nucleotide identities of 96.2 to 99.9%, 97.0 to 100.0%, 95.2 to 100.0%, and 95.7 to 99.8% in the complete genome, ORF1, ORF2, and ORF3, respectively, and 94.4 to 100.0%, 91.3 to 100.0%, and 98.7 to 100.0% amino acid similarity in the VP2, VP3, and VP1 proteins, respectively. Phylogenetic analysis of the whole genome showed that 10 GyVg1 strains belong to genotype I, and one strain belongs to genotype III. Sequence analysis showed several amino acid substitutions in both the VP1, VP2, and VP3 proteins. Our results enhance the understanding of the molecular characterization of GyVg1 infection in southern China. In conclusion, this study reveals the high prevalence and high genetic differentiation of GyVg1 in Chinese chickens and suggests that the potential impact of GyVg1 on the chicken industry may be of concern.

Molecular evolution analysis of three species gyroviruses in China from 2018 to 2019

Gyrovirus (GyV) is a widespread ssDNA virus with a high population diversity, and several of its species, including the chicken anemia virus (CAV), gyrovirus galga 1 (GyG1), and gyrovirus homsa 1 (GyH1), have been shown to be pathogenic to poultry. The evolution of these viruses, however, is still unclear. Our study analyzed epidemiology and molecular evolution of three species of GyVs (CAV, GyG1, and GyH1) from 2018 to 2019 in China. The survey results indicated that GyV was widespread in China. It is vital to consider the coinfections among the three species of GyV. The phylogenetic analysis showed that CAV was divided into three clades and GyG1 and GyH1 were divided into two clades. Based on the recombination analysis, CAV and GyG1 had similar recombination regions associated with viral replication and transcription. Furthermore, the substitution rates for CAV and GyG1 were approximately 6.09 × 10^-4 and 2.784 × 10^-4 nucleotides per site per year, respectively. The high substitution rate and recombination were the main factors for the high diversity of GyVs. Unfortunately, GyH1 strains have not been discovered in enough numbers to allow evolutionary analysis. The GyVs had several positively selected sites, possibly related to their potential to escape the host immune response. In summary, our study provides insights into the time of origin, evolution rate, and recombination of GyV for assessing their evolutionary process and genetic diversity.

The Synergy of Chicken Anemia Virus and Gyrovirus Homsa 1 in Chickens

Chicken anemia virus (CAV) and Gyrovirus homsa 1 (GyH1) are members of the Gyrovirus genus. The two viruses cause similar clinical manifestations in chickens, aplastic anemia and immunosuppression. Our previous investigation displays that CAV and GyH1 often co-infect chickens. However, whether they have synergistic pathogenicity in chickens remains elusive. Here, we established a co-infection model of CAV and GyH1 in specific pathogen-free (SPF) chickens to explore the synergy between CAV and GyH1. We discovered that CAV and GyH1 significantly inhibited weight gain, increased mortality, and hindered erythropoiesis in co-infected chickens. Co-infected chickens exhibited severe immune organ atrophy and lymphocyte exhaustion. The proventriculus and gizzard had severe hemorrhagic necrosis and inflammation. We also discovered that the viral loads and shedding levels were higher and lasted longer in CAV and GyH1 co-infected chickens than in mono-infected chickens. Our results demonstrate that CAV and GyH1 synergistically promote immunosuppression, pathogenicity, and viral replication in co-infected chicken, highlighting the interaction between CAV and GyH1 in the disease process and increasing potential health risk in the poultry breeding industry, and needs further attention.

Detection of Gyrovirus galga 1 in Cryopreserved Organs from Two Commercial Broiler Flocks in Japan

Gyrovirus galga 1 (GyVg1, previously recognized as avian gyrovirus 2), which was first reported in chicken in 2011, is a new member of the genus Gyrovirus. The presence of GyVg1 has also been confirmed in different regions of Europe, South America, Africa, and Asia, indicating its global distribution. However, because there are no reports of examining the distribution of GyVg1 in animals in Japan, the epidemiology of this virus is unknown. In this study, we attempted to retrospectively detect GyVg1 in cryopreserved chicken materials derived from different two commercial broiler flocks in 1997. The GyVg1 genome was detected in organ materials derived from both flocks by PCR. GyVg1 detected in both flocks was classified into four genetic groups by analyzing the nucleotide sequences of the detected PCR products. These results suggest that diverse GyVg1 strains were present in commercial chicken flocks as early as 1997 in Japan.

Multitargeted Molecular Dynamic Understanding of Butoxypheser Against SARS-CoV-2: An in Silico Study

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) was initially reported in the Wuhan province of China, spread throughout the world, and caused massive destruction in the form of a global pandemic that started back in 2020. SARS-CoV-2 is an RNA virus with various proteins like main protease, spike protein, NSP15 endoribonuclease, RNA-dependent RNA polymerase, and papain-like protease targeted to screen and find the novel drug candidate that can potentially work against the virus. Previous studies have reported multiple drugs after screening and validation against a single target and reported multiple medications. Nevertheless, many drugs are being used to date but do not have enough potential to work against SARS-CoV-2 and curb the spread and death rate. In this study, with the hypothesis of 1 drug and multiple targets, we have taken 5 main target proteins and screened the Asinex's complete BioDesign library (1,70,269 compounds) and identified N-{2-[(2S)-2-Amino-3-methylbutoxy]-6-propylbenzoyl}-L-phenylalanyl-L-serine (Butoxypheser) as multitarget inhibitor against SARS-CoV-2. Also, Butoxypheser has shown excellent docking scores, hydrogen bonding, and other bonding configurations like van der Waals force and water bridges. The stability and interaction pattern of the compound was validated with structural interaction fingerprints (SIFts) and molecular dynamics (MD) simulation. The Butoxypheser has performed flawlessly throughout the study, and the same results were used to compare the compound's activity against multiple targets. After a thorough theoretical comparative analysis, Butoxypheser can be treated as a multitargeted inhibitor candidate against SARS-CoV-2. Further, this study needs to be validated experimentally before human use.

Serological investigation of Gyrovirus homsa1 infections in chickens in China

BACKGROUND

Gyrovirus homsa1 (GyH1) (also known as Gyrovirus 3, GyV3) is a non-enveloped, small, single-stranded DNA virus, which was first identified in children with acute diarrhea, and was subsequently detected in marketed chickens, broilers with transmissible viral proventriculitis (TVP), and mammals. GyH1 is a pathogenic virus in chickens, causing aplastic anemia, immunosuppression, and multisystem damage. However, the seroepidemiology of GyH1 infection in chickens remains unclear. Here, we investigated the seroprevalence of GyH1 in chickens by ELISA to reveal the endemic status of GyH1 in China.

RESULTS

An indirect ELISA with high sensitivity and specificity was developed for investigation of seroepidemiology of GyH1 in chickens in China. The seropositive rate of GyH1 ranged from 0.6% to 7.7% in thirteen provinces, and ranged from 4.1% to 8.1% in eight species chickens. The seropositive rate of GyH1 in broiler breeders was significantly higher than that of in layers. There was a negative correlation between seropositive rate and age of chickens. The highest and lowest seropositive rate were present in chickens at 30-60 days and over 180 days, respectively.

CONCLUSIONS

The seroepidemiological investigation results demonstrated that natural GyH1 infection is widespread in chickens in China. Different species showed different susceptibility for GyH1. Aged chickens showed obvious age-resistance to GyH1. GyH1 has shown a high risk to the poultry industry and should be highly concerned.

Cross-species transmission potential of chicken anemia virus and avian gyrovirus 2

The Gyrovirus genus consists of nonenveloped, icosahedral viruses with small circular single-stranded DNA genomes. Gyroviruses have been detected in diverse hosts, including humans, chickens, rodents, and cats. Two Gyroviruses were detected in canine serum samples using PCR in this study. The results indicated that four serum samples were positive for CAV (0.28%, 2/700) or AGV2 (0.28%, 2/700). Additionally, recombination analysis showed that AGV2 and CAV might have originated from the recombination of viruses similar to those detected in chickens and humans. We detected a total of 14 mutations in CAV VP1 amino acid sequences and identified new mutations at positions 31, 388, 390, 399, and 421 for the first time. The identification of T390C, C912T, T1230C, and T1297C mutations in AGV2 VP1, R93C mutations in AGV2 VP2, and R58C mutations AGV2 VP3 indicated that the differences might be related to a transboundary movement among hosts, which requires further elucidation. To the best of our knowledge, this study is the first report of an AGV2-infected dog in China, suggesting that the cross-species transmission of viruses with circular single-stranded DNA genomes is a public health concern.

A novel gyrovirus in a common pheasant (Phasianus colchicus) with poult enteritis and mortality syndrome

A novel gyrovirus was detected in an intestinal specimen of a common pheasant that died due to poult enteritis and mortality syndrome. The genome of the pheasant-associated gyrovirus (PAGyV) is 2353 nucleotides (nt) long and contains putative genes for the VP1, VP2, and VP3 proteins in an arrangement that is typical for gyroviruses. Gyrovirus-specific motifs were identified in both the coding region and the intergenic region of the PAGyV genome. The VP1 of PAGyV shares up to 67.6% pairwise nt sequence identity with reference sequences and forms a distinct branch in the phylogenetic tree. Thus, according to the recently described species demarcation criteria, PAGyV belongs to a novel species in the genus Gyrovirus, family Anelloviridae, for which we propose the name "Gyrovirus phaco 1".

Insights into the Role of Commensal-Specific T Cells in Intestinal Inflammation

Trillions of microorganisms exist in the human intestine as commensals and contribute to homeostasis through their interactions with the immune system. In this review, we use previous evidence from published papers to elucidate the involvement of commensal-specific T cells (CSTCs) in regulating intestinal inflammatory responses. CSTCs are generated centrally in the thymus or peripherally at mucosal interfaces and present as CD4+ or CD8+ T cells. Bacteria, fungi, and even viruses act commensally with humans, warranting consideration of CSTCs in this critical relationship. Dysregulation of this immunological balance can result in both intestinal inflammation or damaging autoimmune responses elsewhere in the body. Given the relative novelty of CSTCs in the literature, we aim to introduce the importance of their role in maintaining immune homeostasis at barrier sites such as the intestine.

Kinetic analysis of pathogenicity and tissue tropism of gyrovirus 3 in experimentally infected chickens

Gyrovirus 3 (GyV3), the third novel emerging species of the genus Gyrovirus of the Anelloviridae family, has been described in multiple hosts. Epidemiologically, there are suggestions that GyV3 is associated with diarrhea/proventriculitis, however, no direct causal evidence exists between GyV3 infection and specific clinical diseases. Herein, we infected special pathogen-free (SPF) chickens with GyV3, and then assessed the pathogenicity and tissue tropism. The results revealed that GyV3 induced persistent infection characterized by diarrhea, aplastic anemia, immunosuppression, and persistent systemic lymphocytic inflammation. Clinically, the infected chickens presented ruffled feathers, diarrhea, anemia, and weight loss. Aplastic anemia was characterized by progressive depletion of hematopoietic cells in the bone marrow, immunosuppression was associated with atrophy of the thymus, spleen, and bursa of Fabricious, progressive lymphocytic inflammations were characterized by proventriculitis, adrenalitis, pancreatitis, hepatitis, nephritis, and bronchitis. Viral loads of GyV3 in tissues exhibited “M”, “N”, “W” or “V” type dynamic changes. The highest level of viral loads was reported in bone marrow at 7dpi, followed by the adrenal gland at 2 dpi, the sciatic nerve at 7 dpi, and bile at 35 dpi. The bone marrow and kidney demonstrate the strongest immunostaining of GyV3-VP1 antigen and were suggested as the target tissues of GyV3. Collectively, GyV3 is an immunosuppressive pathogenic virus that targets the bone marrow and kidney in chickens. Exploring the pathogenicity and tissue tropism of GyV3 will guide the basic understanding of the biology of GyV3 and its pathogenesis in chickens.

Cross-species pathogenicity of gyrovirus 3 in experimentally infected chickens and mice

Gyrovirus 3 (GyV3) has been identified in humans and other hosts, suggesting its cross-species pathogenicity, which poses an increased public health risk. In the current study, we established chicken and mouse models of GyV3 infection. We found that GyV3 induced persistent infections, characterized by viremia, aplastic anemia, immunosuppression, and systematic lymphocytic inflammation, in both species. Kinetic viral loads and antigen expression demonstrated rapid viral replication and broad tissue tropism of GyV3 in both models. The highest viral loads and the strongest antigen immunostaining were present in bone marrow and cerebrum in both chickens and mice, indicating that these are target tissues for GyV3. Genetic diversity analysis of VP1 in infected chickens and mice showed that GyV3 adapts to new hosts via rapid evolution of the hypervariable region of the gene encoding the structural protein VP1. Overall, our results indicate that GyV3 is a cross-species pathogenic virus; therefore, more attention needs to be paid to high levels of GyV3-induced neurotropism and aplastic anemia as a public health risk.

Complex evolutionary history of felid anelloviruses

Anellovirus infections are highly prevalent in mammals, however, prior to this study only a handful of anellovirus genomes had been identified in members of the Felidae family. Here we characterise anelloviruses in pumas (Puma concolor), bobcats (Lynx rufus), Canada lynx (Lynx canadensis), caracals (Caracal caracal) and domestic cats (Felis catus). The complete anellovirus genomes (n = 220) recovered from 149 individuals were diverse. ORF1 protein sequence similarity network analysis coupled with phylogenetic analysis, revealed two distinct clusters that are populated by felid-derived anellovirus sequences, a pattern mirroring that observed for the porcine anelloviruses. Of the two-felid dominant anellovirus groups, one includes sequences from bobcats, pumas, domestic cats and an ocelot, and the other includes sequences from caracals, Canada lynx, domestic cats and pumas. Coinfections of diverse anelloviruses appear to be common among the felids. Evidence of recombination, both within and between felid-specific anellovirus groups, supports a long coevolution history between host and virus.

Harmless or Threatening? Interpreting the Results of Molecular Diagnosis in the Context of Virus-Host Relationships

Molecular methods, established in the 1980s, expanded and delivered tools for the detection of vestigial quantities of nucleic acids in biological samples. Nucleotide sequencing of these molecules reveals the identity of the organism it belongs to. However, the implications of such detection are often misinterpreted as pathogenic, even in the absence of corroborating clinical evidence. This is particularly significant in the field of virology where the concepts of commensalism, and other benign or neutral relationships, are still very new. In this manuscript, we review some fundamental microbiological concepts including commensalism, mutualism, pathogenicity, and infection, giving special emphasis to their application in virology, in order to clarify the difference between detection and infection. We also propose a system for the correct attribution of terminology in this context.

The Role of Apoptin in Chicken Anemia Virus Replication

Apoptin is the Vp3 protein of chicken anemia virus (CAV), which infects the thymocytes and erythroblasts in young chickens, causing chicken infectious anemia and immunosuppression. Apoptin is highly studied for its ability to selectively induce apoptosis in human tumor cells and, thus, is a protein of interest in anti-tumor therapy. CAV apoptin is known to localize to different subcellular compartments in transformed and non-transformed cells, depending on the DNA damage response, and the phosphorylation of several identified threonine residues. In addition, apoptin interacts with molecular machinery such as the anaphase promoting complex/cyclosome (APC/C) to inhibit the cell cycle and induce arrest in G2/M phase. While these functions of apoptin contribute to the tumor-selective effect of the protein, they also provide an important fundamental framework to apoptin’s role in viral infection, pathogenesis, and propagation. Here, we reviewed how the regulation, localization, and functions of apoptin contribute to the viral life cycle and postulated its importance in efficient replication of CAV. A model of the molecular biology of infection is critical to informing our understanding of CAV and other related animal viruses that threaten the agricultural industry.

Cancer Treatment Goes Viral: Using Viral Proteins to Induce Tumour-Specific Cell Death

Cell death is a tightly regulated process which can be exploited in cancer treatment to drive the killing of the tumour. Several conventional cancer therapies including chemotherapeutic agents target pathways involved in cell death, yet they often fail due to the lack of selectivity they have for tumour cells over healthy cells. Over the past decade, research has demonstrated the existence of numerous proteins which have an intrinsic tumour-specific toxicity, several of which originate from viruses. These tumour-selective viral proteins, although from distinct backgrounds, have several similar and interesting properties. Though the mechanism(s) of action of these proteins are not fully understood, it is possible that they can manipulate several cell death modes in cancer exemplifying the intricate interplay between these pathways. This review will discuss our current knowledge on the topic and outstanding questions, as well as deliberate the potential for viral proteins to progress into the clinic as successful cancer therapeutics.

Genetic Analysis of Avian Gyrovirus 2 Variant-Related Gyrovirus Detected in Farmed King Ratsnake (Elaphe carinata): The First Report from China

Avian gyrovirus 2 (AGV2), which is similar to chicken infectious anemia virus, is a new member of the genus Gyrovirus. AGV2 has been detected not only in chicken but also in human tissues and feces. This study analyzed 91 samples (8 from liver tissue and 83 from fecal samples) collected from king ratsnakes (Elaphe carinata) from 7 separate farms in Hubei and Henan, China, for AGV2 DNA using PCR. The results demonstrated a low positive rate of AGV2 (6.59%, 6/91) in the snakes, and all the positive samples were collected from the same farm. The AGV2 strain HB2018S1 was sequenced, and its 2376 nt genome comprised three partially overlapping open reading frames: VP1, VP2, and VP3. Phylogenetic analysis revealed that the HB2018S1 and NX1506-1 strains from chickens in China belong to the same clade and that they have a nucleotide identity as high as 99.5%. Additionally, recombination analysis showed that HB2018S1 might originate from the recombination of viruses similar to those detected in chickens and a ferret. A total of 10 amino acid mutation sites (44(R/K), 74(T/A), 256 (C/R), 279(L/Q), and 373(V/A) in AGV2 VP1; 60(I/T), 125(T/I), 213(D/N), and 215(L/S) in AGV2 VP2; and 83(H/Y) in AGV2 VP3) different from those observed in most reference strains were found in the genome of HB2018S1, indicating that the differences may be related to a transboundary movement among hosts, which needs further elucidation. To the best of our knowledge, this study is the first report on an AGV2-infected poikilotherm, suggesting that cross-host transmission of viruses with circular single-stranded DNA genomes would be a public health concern.

Genomic Characterization of Diverse Gyroviruses Identified in the Feces of Domestic Cats

Gyroviruses (GyVs) are small, single-stranded, circular DNA viruses in the genus Gyrovirus, which consists of the chicken anemia virus (CAV) prototype and nine other viral species. These different GyV species have been reported in chickens, humans, mice, and companion animals. To date, CAV has been identified in the feces of domestic cats, while the circulation of other GyV species in cats is currently unknown. In the present study, 197 fecal samples were collected from pet cats in northeast China, and samples were screened for different GyV species by PCR. Twelve GyV strains were identified from the feces of pet cats. These included 4 positive for CAV, 3 for HGyV/AGV2, 3 for GyV3 and 2 positive for GyV6. The complete genome sequences of the 12 cat-sourced GyV strains showed 93.9-99.7% nucleotide identities to the homologous reference GyV strains. Phylogenetic analyses based on the complete genomes, VP1, VP2 and VP3 genes showed the identical classification of GyV species with previous reports. Moreover, one and four unique amino acid substitutions were identified in the VP1 protein of the cat-sourced HGyV/AGV2 and GyV6 strains, respectively, and one substitution was also observed in the VP2 protein of one GyV6 strain identified in this study. In conclusion, our investigation demonstrates that the diverse GyV species were circulating in domestic cats, and provides the first molecular evidence for the circulation of HGyV/AGV2, GyV3 and GyV6 in domestic cats. These cat-origin GyVs possessed considerable genetic diversity. This study also raises the possibility that domestic cats, as reservoirs for gyroviruses, may inadvertently disseminate viruses to other species, e.g., humans and chickens.

Molecular epidemiology of chicken anaemia virus in sick chickens in China from 2014 to 2015

Chicken anaemia virus (CAV), a member of the genus Gyrovirus, is the etiological agent of chicken infectious anaemia. CAV infects bone marrow-derived cells, resulting in severe anaemia and immunosuppression in young chickens and a compromised immune response in older birds. We investigated the molecular epidemiology of CAV in sick chickens in China from 2014 to 2015 and showed that the CAV-positive rate was 13.30%, in which mixed infection (55.56%) was the main type of infection. We isolated and identified 15 new CAV strains using different methods including indirect immunofluorescence assay and Western Blotting. We used overlapping polymerase chain reaction to map the whole genome of the strains. Phylogenetic analyses of the obtained sequences and related sequences available in GenBank generated four distinct groups (A-D). We built phylogenetic trees using predicted viral protein (VP) sequences. Unlike CAV VP2s and VP3s that were well conserved, the diversity of VP1s indicated that the new strains were virulent. Our epidemiological study provided new insights into the prevalence of CAV in clinical settings in recent years in China.

Genome Sequence of a Gyrovirus Associated with Ashy Storm-Petrel

Ashy storm-petrels (order Procellariiformes) are seabirds that are found along the coast of California to Baja Mexico. A novel gyrovirus was identified from a cloacal swab of an ashy storm-petrel, which is the second gyrovirus to be identified in sea birds, the first being found in the related northern fulmar.

Prevalence of fecal viruses and bacteriophage in Canadian farmed mink (Neovison vison)

Recent viral metagenomic studies have demonstrated the diversity of eukaryotic viruses and bacteriophage shed in the feces of domestic species. Although enteric disease is a major concern in the commercial mink farming industry, few etiologic agents have been well characterized. This study aimed to identify viruses shed in the fecal matter of clinically healthy commercial mink from 40 southern Ontario farms. Viral RNA was extracted from 67 pooled fecal samples (30 adult female mink and 37 kit) and amplified for Illumina sequencing on the NextSeq platform, and the resulting contigs were trimmed and assembled using Trimmomatic 0.36.0 and Spades 3.8.0 in iVirus (CyVerse, AZ, USA) and SeqMan NGen 12 (DNAStar, WI, USA). Identification of assembled sequences >100 bp (Geneious 10.1.3) showed an abundance of bacteriophage sequences, mainly from families Siphoviridae (53%), Podoviridae (22%), Myoviridae (20%), Inoviridae (1%), Leviviridae (0.04%), Tectiviridae (0.01%), and Microviridae (0.01%). A diverse range of vertebrate viruses were detected, of which posavirus 3, mink bocavirus, gyroviruses, and avian‐associated viruses were most abundant. Additionally, sequences from nonvertebrate viruses with water and soil‐associated amebal and algal hosts were also highly prevalent. The results of this study show that viruses shed in the fecal matter of healthy commercial mink are highly diverse and could be closely associated with diet, and that more research is necessary to determine how the detected viruses may impact mink health.

Unexpected heat shock element binding ability and tumor-killing activity of the combinatorial function domain of apoptin

Apoptin, derived from the chicken anemia virus, has been found to exert tumor-preferential apoptotic activity. It is a potential anticancer agent with direct clinical applications. However, if this viral protein were to be used as a new drug, it might also induce a strong immune response, causing toxic side effects. In a previous study, our group showed that TAT-apoptin downregulates the stress expression of heat shock protein 70 by competing with heat shock factor protein 1 in binding to the heat shock element (HSE) of the promoter region of heat shock protein 70, thus inducing specific apoptosis in HepG2 cells. In this study, we investigated the HSE-binding properties of the minimal functional region of apoptin. We showed that apoptin's nuclear localization signals 1 and nuclear localization signals 2 represented functional regions that could bind with HSE and that this binding capacity was increased by polymers formed through the introduction of a leucine-rich stretch. Our data also showed that truncated combinatorial apoptin peptide has greater tumor-specific cell-killing activity and could be a potential antitumor agent.

Identification of the interaction and interaction domains of chicken anemia virus VP2 and VP3 proteins

Chicken anemia virus (CAV) is a small, single-stranded DNA virus of Anelloviridae family. Its genome segments encode three proteins, VP1, VP2, and VP3. This study identified an interaction between VP2 and VP3 and mapped the interaction domains. Through the yeast two-hybrid (Y2H) system, VP2 was found to interact with VP3. The presence of the VP2-VP3 complex in CAV-infected chicken cells was confirmed by co-immunoprecipitation. Confocal microscopy showed that VP2 and VP3 were expressed in the cytoplasm in cotransfected Vero cells. In the Y2H system, the interaction domains were identified as being within the N-terminal aa 1-30 and C-terminal aa 17-60 for VP2 and the N-terminal aa 46-60 and C-terminal aa 1-7 for VP3. This study showed the interaction between VP2 and VP3 of CAV and identified multiple independent interactive domains within the two proteins. This provides novel information for investigating the biological functions of these proteins.

VP2 of Chicken Anaemia Virus Interacts with Apoptin for Down-regulation of Apoptosis through De-phosphorylated Threonine 108 on Apoptin

Chicken anaemia virus (CAV) is an important contagious agent that causes immunosuppressive disease in chickens. CAV Apoptin is a nucleoplasmic shuffling protein that induces apoptosis in chicken lymphoblastoid cells. In the present study, confocal microscopy revealed co-localisation of expressed CAV non-structural protein VP2 with Apoptin in the nucleus of MDCC-MSB1 cells and the nucleoplasmic compartment of CHO-K1 cells. In vitro pull-down and ex vivo biomolecular fluorescent complementation (BiFC) assays further showed that the VP2 protein directly interacts with Apoptin. Transient co-expression of VP2 and Apoptin in MDCC-MSB1 cells significantly decreased the rate of apoptosis compared with that in cells transfected with the Apoptin gene alone. In addition, the phosphorylation status of threonine 108 (Thr108) of Apoptin was found to decrease upon interaction with VP2. Although dephosphorylated Thr108 did not alter the subcellular distribution of Apoptin in the nucleus of MDCC-MSB1 cells, it did suppress apoptosis. These findings provide the first evidence that VP2 directly interacts with Apoptin in the nucleus to down-regulate apoptosis through alterations in the phosphorylation status of the latter. This information will be useful to further elucidate the underlying mechanism of viral replication in the CAV life cycle.

Virome comparisons in wild-diseased and healthy captive giant pandas

BACKGROUND

The giant panda (Ailuropoda melanoleuca) is a vulnerable mammal herbivore living wild in central China. Viral infections have become a potential threat to the health of these endangered animals, but limited information related to these infections is available.

METHODS

Using a viral metagenomic approach, we surveyed viruses in the feces, nasopharyngeal secretions, blood, and different tissues from a wild giant panda that died from an unknown disease, a healthy wild giant panda, and 46 healthy captive animals.

RESULTS

The previously uncharacterized complete or near complete genomes of four viruses from three genera in Papillomaviridae family, six viruses in a proposed new Picornaviridae genus (Aimelvirus), two unclassified viruses related to posaviruses in Picornavirales order, 19 anelloviruses in four different clades of Anelloviridae family, four putative circoviruses, and 15 viruses belonging to the recently described Genomoviridae family were sequenced. Reflecting the diet of giant pandas, numerous insect virus sequences related to the families Iflaviridae, Dicistroviridae, Iridoviridae, Baculoviridae, Polydnaviridae, and subfamily Densovirinae and plant viruses sequences related to the families Tombusviridae, Partitiviridae, Secoviridae, Geminiviridae, Luteoviridae, Virgaviridae, and Rhabdoviridae; genus Umbravirus, Alphaflexiviridae, and Phycodnaviridae were also detected in fecal samples. A small number of insect virus sequences were also detected in the nasopharyngeal secretions of healthy giant pandas and lung tissues from the dead wild giant panda. Although the viral families present in the sick giant panda were also detected in the healthy ones, a higher proportion of papillomaviruses, picornaviruses, and anelloviruses reads were detected in the diseased panda.

CONCLUSION

This viral survey increases our understanding of eukaryotic viruses in giant pandas and provides a baseline for comparison to viruses detected in future infectious disease outbreaks. The similar viral families detected in sick and healthy giant pandas indicate that these viruses result in commensal infections in most immuno-competent animals.

Viruses with Circular Single-Stranded DNA Genomes Are Everywhere!

Circular single-stranded DNA viruses infect archaea, bacteria, and eukaryotic organisms. The relatively recent emergence of single-stranded DNA viruses, such as chicken anemia virus (CAV) and porcine circovirus 2 (PCV2), as serious pathogens of eukaryotes is due more to growing awareness than to the appearance of new pathogens or alteration of existing pathogens. In the case of the ubiquitous human circular single-stranded DNA virus family Anelloviridae, there is still no convincing direct causal relation to any specific disease. However, infections may play a role in autoimmunity by changing the homeostatic balance of proinflammatory cytokines and the human immune system, indirectly affecting the severity of diseases caused by other pathogens. Infections with CAV (family Anelloviridae, genus Gyrovirus) and PCV2 (family Circoviridae, genus Circovirus) are presented here because they are immunosuppressive and affect health in domesticated animals. CAV shares genomic organization, genomic orientation, and common features of major proteins with human anelloviruses, and PCV2 DNA may be present in human food and vaccines.

Genetic Analysis of Two Chicken Infectious Anemia Virus Variants-Related Gyrovirus in Stray Mice and Dogs: The First Report in China, 2015

Chicken infectious anemia virus (CIAV) causes acute viral infection in chickens worldwide. It can infect chickens of all ages, but the disease is seen only in young chickens and is characterized by hemorrhagic lesions in the muscles, atrophic changes in the lymphoid organs, aplastic bone marrow, and immunosuppression causing increased mortality. Previous studies have demonstrated that CIAV can be isolated from blood specimens of humans and fecal samples of stray cats. In the present study, two variants of CIAV were isolated from fecal samples of mice (CIAV-Mouse) and stray dogs (CIAV-Dog), respectively. The genome of the two CIAV variants was sequenced and the results of the recombination detection program suggested that the CIAV-Dog strain could be a recombinant viral strain generated from parental CIAV strains, AB119448 and GD-1-12, with high confidence. Particularly, these findings were obtained from the comparison of genetic diversity and the relationship of CIAV between different hosts. This is the first report indicating that there is a significant difference in the number of transcription factor binding sites in CIAV noncoding regions from different hosts. Further studies are required to investigate the large geographic distribution of CIAV and monitor the variants, host range, and associated diseases.

Novel characteristics of the avian gyrovirus 2 genome

Avian gyrovirus 2 (AGV2) was the second member of the viral genus Cyclovirus to be discovered. This virus poses a significant potential threat to humans and poultry due to its global dissemination and infectiousness. We used three overlapping polymerase chain reactions (PCRs) to map the whole genome of AGV2. We then modelled the evolutionary history of these novel sequence data in the context of related sequences from GenBank. We analysed the viral protein characteristics of the different phylogenetic groups and explored differences in evolutionary trends between Chinese strains and strains from other countries. We obtained 17 avian-sourced AGV2 whole genomes from different regions of China from 2015 to 2016. Phylogenetic analyses of these Chinese AGV2 sequences and related sequences produced four distinct groups (A-D) with significant bootstrap values. We also built phylogenies using predicted viral protein sequences. We found a potential hypervariable region in VP1 at sites 288-314, and we identified the amino acid changes responsible for the distinct VP2 and VP3 groups. Three new motifs in the AGV2 5'-UTR direct repeat (DR) region were discovered and grouped. The novel characteristics and diverse research on the AGV2 genome provide a valuable framework for additional research.

Revisiting the taxonomy of the family Circoviridae: establishment of the genus Cyclovirus and removal of the genus Gyrovirus

The family Circoviridae contains viruses with covalently closed, circular, single-stranded DNA (ssDNA) genomes, including the smallest known autonomously replicating, capsid-encoding animal pathogens. Members of this family are known to cause fatal diseases in birds and pigs and have been historically classified in one of two genera: Circovirus, which contains avian and porcine pathogens, and Gyrovirus, which includes a single species (Chicken anemia virus). However, over the course of the past six years, viral metagenomic approaches as well as degenerate PCR detection in unconventional hosts and environmental samples have elucidated a broader host range, including fish, a diversity of mammals, and invertebrates, for members of the family Circoviridae. Notably, these methods have uncovered a distinct group of viruses that are closely related to members of the genus Circovirus and comprise a new genus, Cyclovirus. The discovery of new viruses and a re-evaluation of genomic features that characterize members of the Circoviridae prompted a revision of the classification criteria used for this family of animal viruses. Here we provide details on an updated Circoviridae taxonomy ratified by the International Committee on the Taxonomy of Viruses in 2016, which establishes the genus Cyclovirus and reassigns the genus Gyrovirus to the family Anelloviridae, a separate lineage of animal viruses that also contains circular ssDNA genomes. In addition, we provide a new species demarcation threshold of 80% genome-wide pairwise identity for members of the family Circoviridae, based on pairwise identity distribution analysis, and list guidelines to distinguish between members of this family and other eukaryotic viruses with circular, ssDNA genomes.

The Viruses of the Gut Microbiota

The gut virome is the viral component of the gut microbiome. Knowledge regarding its composition, interindividual and temporal variability is increasing, and the significance of its impact on human health, both in homeostasis and disease is being recognized. Here we review the recent advances in this field, and the questions that arise in the context of the rapidly increasing information regarding its composition and function. With the extending collection of human data, the power of next generation sequencing, and functional studies, the factors that influence the composition of the gut virome and its impact on human health will be further refined in the coming years.

Activation of the Chicken Anemia Virus Apoptin Protein by Chk1/2 Phosphorylation Is Required for Apoptotic Activity and Efficient Viral Replication

Chicken anemia virus (CAV) is a single-stranded circular DNA virus that carries 3 genes, the most studied of which is the gene encoding VP3, also known as apoptin. This protein has been demonstrated to specifically kill transformed cells while leaving normal cells unharmed in a manner that is independent of p53 status. Although the mechanistic basis for this differential activity is unclear, it is evident that the subcellular localization of the protein is important for the difference. In normal cells, apoptin exists in filamentous networks in the cytoplasm, whereas in transformed cells, apoptin is present in the nucleus and appears as distinct foci. We have previously demonstrated that DNA damage signaling through the ataxia telangiectasia mutated (ATM) pathway induces the translocation of apoptin from the cytoplasm to the nucleus, where it induces apoptosis. We found that apoptin contains four checkpoint kinase consensus sites and that mutation of either threonine 56 or 61 to alanine restricts apoptin to the cytoplasm. Furthermore, treatment of tumor cells expressing apoptin with inhibitors of checkpoint kinase 1 (Chk1) and Chk2 causes apoptin to localize to the cytoplasm. Importantly, silencing of Chk2 rescues cancer cells from the cytotoxic effects of apoptin. Finally, treatment of virus-producing cells with Chk inhibitor protects them from virus-mediated toxicity and reduces the titer of progeny virus. Taken together, our results indicate that apoptin is a sensor of DNA damage signaling through the ATM-Chk2 pathway, which induces it to migrate to the nucleus during viral replication.

IMPORTANCE

The chicken anemia virus (CAV) protein apoptin is known to induce tumor cell-specific death when expressed. Therefore, understanding its regulation and mechanism of action could provide new insights into tumor cell biology. We have determined that checkpoint kinase 1 and 2 signaling is important for apoptin regulation and is a likely feature of both tumor cells and host cells producing virus progeny. Inhibition of checkpoint signaling prevents apoptin toxicity in tumor cells and attenuates CAV replication, suggesting it may be a future target for antiviral therapy.

Torquetenovirus: the human virome from bench to bedside

Torquetenovirus (TTV) is the most abundant component of human virome. Virologists have long ignored this orphan and highly divergent virus, in part because TTV cannot be cultured and because it lacks serology reagents and animal models. Nevertheless, it is almost endemic worldwide and is insensitive to current antiviral drugs, so its monitoring is useful in various conditions. To date, TTV as a marker has proved useful in at least two circumstances: to identify anthropogenic pollution and to assess functional immune competence in immunosuppressed individuals. This review summarizes recent findings about TTV and discusses the main hurdles in translating them into clinical diagnostics.

Viral metagenomics applied to blood donors and recipients at high risk for blood-borne infections

BACKGROUND

Characterisation of human-associated viral communities is essential for epidemiological surveillance and to be able to anticipate new potential threats for blood transfusion safety. In high-resource countries, the risk of blood-borne agent transmission of well-known viruses (HBV, HCV, HIV and HTLV) is currently considered to be under control. However, other unknown or unsuspected viruses may be transmitted to recipients by blood-derived products. To investigate this, the virome of plasma from individuals at high risk for parenterally and sexually transmitted infections was analysed by high throughput sequencing (HTS).

MATERIALS AND METHODS

Purified nucleic acids from two pools of 50 samples from recipients of multiple transfusions, and three pools containing seven plasma samples from either HBV-, HCV- or HIV-infected blood donors, were submitted to HTS.

RESULTS

Sequences from resident anelloviruses and HPgV were evidenced in all pools. HBV and HCV sequences were detected in pools containing 3.8×10(3) IU/mL of HBV-DNA and 1.7×10(5) IU/mL of HCV-RNA, respectively, whereas no HIV sequence was found in a pool of 150 copies/mL of HIV-RNA. This suggests a lack of sensitivity in HTS performance in detecting low levels of virus. In addition, this study identified other issues, including laboratory contaminants and the uncertainty of taxonomic assignment of short sequence. No sequence suggestive of a new viral species was identified.

DISCUSSION

This study did not identify any new blood-borne virus in high-risk individuals. However, rare and/or viruses present at very low titre could have escaped our protocol. Our results demonstrate the positive contribution of HTS in the detection of viral sequences in blood donations.

Beyond the gut bacterial microbiota: The gut virome

The gastrointestinal tract is colonized with a highly different population of bacterial, viral, ad fungal species; viruses are reported to be dominant. The composition of gut virome is closely related to dietary habits and surrounding environment. Host and their intestinal microbes live in a dynamic equilibrium and viruses stimulate a low degree of immune responses without causing symptoms (host tolerance). However, intestinal phages could lead to a rupture of eubiosis and may contribute to the shift from health to disease in humans and animals. Viral nucleic acids and other products of lysis of bacteria serve as pathogen‐associated molecular patterns (PAMPs) and could trigger specific inflammatory modulations. At the same time, phages could elicit innate antiviral immune responses. Toll‐like receptors (TLRs) operated as innate antiviral immune sensors and their activation triggers signaling cascades that lead to inflammatory response. J. Med. Virol. 88:1467–1472, 2016. © 2016 Wiley Periodicals, Inc.

How a multidisciplinary 'One Health' approach can combat the tick-borne pathogen threat in Europe

In Europe, ticks are the major arthropod vectors of disease agents to humans and domestic animals. They are capable of transmitting many pathogens most of which have been discovered or identified as tick-borne pathogens in the last 20 years. In recent years, unexplained syndromes occurring after a tick bite have become an increasingly important issue in public and animal health. Ticks and wildlife (the main reservoir of tick-borne pathogens) are highly susceptible to global environmental and socio-economic changes, which in turn may lead to an increased burden of tick-borne diseases. In this review, we explain the importance of a 'One Health' approach to better combat tick-borne diseases.

Viral metagenomics and blood safety

The characterization of the human blood-associated viral community (also called blood virome) is essential for epidemiological surveillance and to anticipate new potential threats for blood transfusion safety. Currently, the risk of blood-borne agent transmission of well-known viruses (HBV, HCV, HIV and HTLV) can be considered as under control in high-resource countries. However, other viruses unknown or unsuspected may be transmitted to recipients by blood-derived products. This is particularly relevant considering that a significant proportion of transfused patients are immunocompromised and more frequently subjected to fatal outcomes. Several measures to prevent transfusion transmission of unknown viruses have been implemented including the exclusion of at-risk donors, leukocyte reduction of donor blood, and physicochemical treatment of the different blood components. However, up to now there is no universal method for pathogen inactivation, which would be applicable for all types of blood components and, equally effective for all viral families. In addition, among available inactivation procedures of viral genomes, some of them are recognized to be less effective on non-enveloped viruses, and inadequate to inactivate higher viral titers in plasma pools or derivatives. Given this, there is the need to implement new methodologies for the discovery of unknown viruses that may affect blood transfusion. Viral metagenomics combined with High Throughput Sequencing appears as a promising approach for the identification and global surveillance of new and/or unexpected viruses that could impair blood transfusion safety.

Apoptin interacts with and regulates the activity of protein kinase C beta in cancer cells

Apoptin, the VP3 protein from chicken anaemia virus (CAV), induces tumour cell-specific cell death and represents a potential future anti-cancer therapeutic. In tumour but not in normal cells, Apoptin is phosphorylated and translocates to the nucleus, enabling its cytotoxic activity. Recently, the β isozyme of protein kinase C (PKCβ) was shown to phosphorylate Apoptin in multiple myeloma cell lines. However, the exact mechanism and nature of interaction between PKCβ and Apoptin remain unclear. Here we investigated the physical and functional link between PKCβ and CAV-Apoptin as well as with the recently identified Apoptin homologue derived from human Gyrovirus (HGyV). In contrast to HCT116 colorectal cancer cells the normal colon mucosa cell lines expressed low levels of PKCβI and showed reduced Apoptin activation, as evident by cytoplasmic localisation, decreased phosphorylation and lack of cytotoxic activity. Co-immunoprecipitation and proximity ligation assay studies identified binding of both CAV- and HGyV-Apoptin to PKCβI in HCT116 cells. Using Apoptin deletion constructs the N-terminal domain of Apoptin was found to be required for interacting with PKCβI. FRET-based PKC activity reporter assays by fluorescence lifetime imaging microscopy showed that expression of Apoptin in cancer cells but not in normal cells triggers a significant increase in PKC activity. Collectively, the results demonstrate a novel cancer specific interplay between Apoptin and PKCβI. Direct interaction between the two proteins leads to Apoptin-induced activation of PKC and consequently activated PKCβI mediates phosphorylation of Apoptin to promote its tumour-specific nuclear translocation and cytotoxic function.

Respiratory viruses and torque teno virus in adults with acute respiratory infections

Objective

To define the molecular epidemiology of respiratory viral infections in adult patients.

Methods

Nasal and throat swabs were collected from all adult patients with influenza-like illness (ILI), acute respiratory infection (ARI), or severe ARI (SARI) admitted to a tertiary hospital in Surakarta, Indonesia, between March 2010 and April 2011 and analyzed for 19 respiratory viruses and for torque teno virus (TTV) and human gyrovirus (HGyV).

Results

Respiratory viruses were detected in 61.3% of the subjects, most of whom had ARI (90.8%, OR = 11.39), were hospitalized (96.9%, OR = 22.31), had asthma exacerbation (90.9%, OR = 8.67), and/or had pneumonia (80%, OR = 4.0). Human rhinovirus (HRV) A43 predominated. Influenza A H3N2, human metapneumovirus (HMPV) subtypes A1 and A2, the influenza B virus, human adenovirus B, and human coronavirus OC43 were also detected. All respiratory viruses were detected in the transition month between the rainy and dry seasons. No mixed respiratory virus infection was found. Coinfections of the influenza A H3N2 virus with TTV, HMPV with TTV, HRV with TTV, and human parainfluenza virus-3 with TTV were found in 4.7, 2.8, 19.8, and 0.9% of the samples, respectively.

Conclusions

This study highlights the need to perform routine detection of respiratory viruses in adults hospitalized with ARI, asthma exacerbation, and/or pneumonia.

A new gyrovirus in human feces

A novel gyrovirus genome found in the feces of an adult with diarrhea is described. The genome shows the three expected main ORFs encoding a structural protein (VP1), nonstructural protein (VP2), and Apoptin protein (VP3), which shared identities of 41, 42, and 38 % with those of the most closely related gyrovirus proteins, respectively. Given the high divergence in its genome, this gyrovirus may be considered the prototype for a new viral species (GyV9) in the Gyrovirus genus. Because the closest relatives of this gyrovirus infect chicken, a possible dietary origin for the presence of this virus in human feces is discussed.

Chicken skin virome analyzed by high-throughput sequencing shows a composition highly different from human skin

Recent studies show that human skin at homeostasis is a complex ecosystem whose virome include circular DNA viruses, especially papillomaviruses and polyomaviruses. To determine the chicken skin virome in comparison with human skin virome, a chicken swabs pool sample from fifteen indoor healthy chickens of five genetic backgrounds was examined for the presence of DNA viruses by high-throughput sequencing (HTS). The results indicate a predominance of herpesviruses from the Mardivirus genus, coming from either vaccinal origin or presumably asymptomatic infection. Despite the high sensitivity of the HTS method used herein to detect small circular DNA viruses, we did not detect any papillomaviruses, polyomaviruses, or circoviruses, indicating that these viruses may not be resident of the chicken skin. The results suggest that the turkey herpesvirus is a resident of chicken skin in vaccinated chickens. This study indicates major differences between the skin viromes of chickens and humans. The origin of this difference remains to be further studied in relation with skin physiology, environment, or virus population dynamics.

Human-gyrovirus-Apoptin triggers mitochondrial death pathway--Nur77 is required for apoptosis triggering

The human gyrovirus derived protein Apoptin (HGV-Apoptin) a homologue of the chicken anemia virus Apoptin (CAV-Apoptin), a protein with high cancer cells selective toxicity, triggers apoptosis selectively in cancer cells. In this paper, we show that HGV-Apoptin acts independently from the death receptor pathway as it induces apoptosis in similar rates in Jurkat cells deficient in either FADD (fas-associated death domain) function or caspase-8 (key players of the extrinsic pathway) and their parental clones. HGV-Apoptin induces apoptosis via the activation of the mitochondrial intrinsic pathway. It induces both mitochondrial inner and outer membrane permebilization, characterized by the loss of the mitochondrial potential and the release into cytoplasm of the pro-apoptotic molecules including apoptosis inducing factor and cytochrome c. HGV-Apoptin acts via the apoptosome, as lack of expression of apoptotic protease-activating factor 1 in murine embryonic fibroblast strongly protected the cells from HGV-Apoptin–induced apoptosis. Moreover, QVD-oph a broad-spectrum caspase inhibitor delayed HGV-Apoptin–induced death. On the other hand, overexpression of the anti-apoptotic BCL-XL confers resistance to HGV-Apoptin–induced cell death. In contrast, cells that lack the expression of the pro-apoptotic BAX and BAK are protected from HGV-Apoptin induced apoptosis. Furthermore, HGV-Apoptin acts independently from p53 signal but triggers the cytoplasmic translocation of Nur77. Taking together these data indicate that HGV-Apoptin acts through the mitochondrial pathway, in a caspase-dependent manner but independently from the death receptor pathway.

A gyrovirus infecting a sea bird

We characterized the genome of a highly divergent gyrovirus (GyV8) in the spleen and uropygial gland tissues of a diseased northern fulmar (Fulmarus glacialis), a pelagic bird beached in San Francisco, California. No other exogenous viral sequences could be identified using viral metagenomics. The small circular DNA genome shared no significant nucleotide sequence identity, and only 38-42 % amino acid sequence identity in VP1, with any of the previously identified gyroviruses. GyV8 is the first member of the third major phylogenetic clade of this viral genus and the first gyrovirus detected in an avian species other than chicken.