Identification of a genetic determinant of pathogenicity in chicken anaemia virus

Genetic characterization of chicken infectious anaemia viruses isolated in Korea and their pathogenicity in chicks

Chicken infectious anaemia virus (CIAV) causes severe anemia and immunosuppression through horizontal or vertical transmission in young chickens. Especially, vertical transmission of virus through the egg can lead to significantly economic losses due to the increased mortality in the broiler industry. Here, 28 CIAV complete sequences circulating in Korea were first characterized using the newly designed primers. Phylogenetic analysis based on the complete sequences revealed that CIAV isolates were divided into four groups, IIa (2/28, 7.1%), IIb (9/28, 32.1%), IIIa (8/28, 28.6%) and IIIb (9/28, 32.1%), and exhibited a close relationship to each other. The major groups were IIb, IIIa and IIIb, and no strains were clustered with a vaccine strain available in Korea. Also, for viral titration, we newly developed a quantitative PCR assay that is highly sensitive, reliable and simple. To investigate the pathogenicity of three major genotypes, 18R001(IIb), 08AQ017A(IIIa), and 17AD008(IIIb) isolates were challenged into one-day-old specific-pathogen-free (SPF) chicks. Each CIAV strain caused anaemia, severe growth retardation and immunosuppression in chickens regardless of CIAV genotypes. Notably, a 17AD008 strain showed stable cellular adaptability and higher virus titer in vitro as well as higher pathogenicity in vivo. Taken together, our study provides valuable information to understand molecular characterization, genetic diversity and pathogenicity of CIAV to improve management and control of CIA in poultry farm.

Pathology and molecular characterization of chicken infectious anemia virus and in silico antigen prediction

The present study investigated five poultry flocks (size 142-600 birds) suspected of chicken infectious anemia (CIA) from Maharashtra, India. The necropsy of dead birds revealed severe atrophy of the thymus, gelatinization of bone marrow, subcutaneous hemorrhages, growth impairment, and severe anemia. Specific PCR targeting, 1390 bp fragment of the CIAV, VP1 gene was used in this study. Sequence analysis revealed that CIAV sequences of this study were grouped in genotype A. At the nucleotide level identity of 99.6% or more was seen between field sequences. At the amino acid level identity of 100% was seen between field sequences and NGP-1. Also, VP1 protein sequences of this study showed high identity with TJBD40, GD-K-12 strains from China and AB046590 strain from Japan. Further, the protein sequences of field CIAV had 0.7% to 2.5% divergence from VP1 sequences of vaccine strains. Antigenic epitopes of VP1 protein were predicted by SVMTriPtool and the field CIAV presented substitutions in two epitopes. To conclude, present study confirms the circulation of genotype A of CIAV in Maharashtra, India and predicted VP1 proteins of field CIAV revealed changes in two epitopes compared to vaccine strains.

Molecular Characteristics of Chicken Infectious Anemia Virus in Central and Eastern China from 2020 to 2022

To evaluate the recent evolution of CIAV in China, 43 flocks of chickens from the provinces of Henan, Jiangsu, Hubei, and Anhui were screened via polymerase chain reaction during 2020-2022. Of these, 27 flocks tested positive for CIAV nucleic acids, including 12 which were positive for other immunosuppression viruses. Additionally, 27 CIAV strains were isolated, and their whole genomes were sequenced. The AH2001 and JS2002 strains shared the highest identity at 99.56%, and the HB2102 and HB2101 strains shared the lowest identity at 95.34%. Based on the genome sequences of these strains and reference strains, a phylogenetic tree was constructed and divided into eight main branches. Most of the strains were grouped with the East Asian strains, whereas the HB2101 strain belonged to the Brazil and Argentina cluster. A recombination event was detected in multiple strains, in which AH2002 recombined from KJ728827/China/2014 (from Taiwan Province) and HN2203, and AH2202 recombined from KX811526/China/2017 (from Shandong Province) and HN2203. All the obtained strains had a highly pathogenic Gln amino acid site at position 394 of the VP1. Overall, our findings demonstrate the importance of CIAV monitoring and provide data that aid in understanding the evolution of CIAV.

Molecular characterization and pathogenicity study of a highly pathogenic strain of chicken anemia virus that emerged in China

Chicken infectious anemia (CIA) is caused by chicken anemia virus (CAV). Recently, severe anemia has emerged in layer chickens (8 to 10-week-old) on poultry farms in China. However, the etiological characteristics and pathogenic potential of CAV in chickens at 6 weeks or older are not well understood. In this study, we isolated a CAV strain, termed SD15, from two-month-old chicken with severe anemia and analyzed the genetic evolution relationship. We found that strain SD15 had the highest homology (98.9%) with CAV18 strain. Comparison with 33 reference strains revealed 16 amino acid mutations in strain SD15, two of which were previously unknown (F210S in VP1 and L25S in Vp3). Compared with low pathogenic strains (Cux-1 and C14), highly pathogenic strains (SDLY08 and SD15) had three base mutations in their noncoding region. To further understand its pathogenicity, 10-week-old specific-pathogen-free (SPF) chickens were challenged with the novel strain and SDLY08. No obvious clinical symptoms were observed in the SDLY08 group. However, SD15-infected chickens showed significant growth retardation and immunosuppression. The main manifestations of immunosuppression were the significantly reduced thymus and bursa indices and AIV-H9 vaccine-induced antibody levels (P < 0.05). The lowest number of red blood cells in the SD15 group was just 60% of that in the control group. Taken together, the novel strain SD15 not only showed higher pathogenicity but also exhibited the potential ability to break the age resistance of older chickens to CAV. Our study enhanced the understanding of the epidemiological characteristics of chickens infected with severe anemia and can facilitate the development of improved control strategies of CIA in China.

Molecular characterization of chicken infectious anaemia virus (CIAV) in China during 2020-2021

Chicken infectious anaemia virus (CIAV) has been identified as the causative agent of chicken infectious anaemia (CIA), causing huge economic losses to the poultry industry globally. In this study, a total of 573 clinical samples were collected from 197 broiler farms in 17 provinces of China during 2020-2021. Among them, 375 samples (375/573, 65.4%) were positive for CIAV by real-time PCR. The positive rate of CIAV detection between different regions of China ranged from 46.67% (North China) to 81.25% (Central China). The nucleotide sequences of the VP1 gene were obtained for 91 CIAV strains, whole genome sequencing was successful for 72 out of 91 strains. Phylogenetic analysis based on the VP1 gene revealed that 91 CIAV strains currently circulating in China belong to three genotypes (II, IIIa and IIIb), and most of the CIAV strains belong to genotype IIIa. Phylogenetic analysis of the whole genome showed that 71 CIAV strains belong to genotype IIIa, and one strain belongs to genotype II. 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 CIAV infection in China.RESEARCH HIGHLIGHTS A molecular systematic survey of CIAV in China during 2020-2021.CIAV genotype IIIa is the predominant genotype in China.

Genetic diversity, distribution, and evolution of chicken anemia virus: A comparative genomic and phylogenetic analysis

Chicken infectious anemia (CIA) is an immunosuppressive poultry disease that causes aplastic anemia, immunosuppression, growth retardation and lymphoid tissue atrophy in young chickens and is responsible for huge economic losses to the poultry industry worldwide. The disease is caused by the chicken anemia virus (CAV), which belongs to the genus Gyrovirus, family Anelloviridae. Herein, we analyzed the full-length genomes of 243 available CAV strains isolated during 1991–2020 and classified them into two major clades, GI and GII, divided into three and four sub-clades, GI a-c, and GII a-d, respectively. Moreover, the phylogeographic analysis revealed that the CAVs spread from Japan to China, China to Egypt and subsequently to other countries, following multiple mutational steps. In addition, we identified eleven recombination events within the coding and non-coding regions of CAV genomes, where the strains isolated in China were the most active and involved in ten of these events. Furthermore, the amino acids variability analysis indicated that the variability coefficient exceeded the estimation limit of 1.00 in VP1, VP2, and VP3 proteins coding regions, demonstrating substantial amino acid drift with the rise of new strains. The current study offers robust insights into the phylogenetic, phylogeographic and genetic diversity characteristics of CAV genomes that may provide valuable data to map the evolutionary history and facilitate preventive measures of CAVs.

Genomic Characterization of CIAV Detected in Contaminated Attenuated NDV Vaccine: Epidemiological Evidence of Source and Vertical Transmission From SPF Chicken Embryos in China

Live attenuated vaccines have been extensively used to prevent infectious disease in poultry flocks. Freedom from exogenous virus is a high priority for any veterinary vaccines. Recently, attenuated Newcastle disease virus (NDV) vaccines were detected to be contaminated with chicken infectious anemia virus (CIAV) in a routine screening for exogenous viruses. To investigate the possible source of the contamination, we conducted virological tests on a specific-pathogen-free (SPF) layer breeder flock that provide the raw materials for vaccines in this manufacturer. Firstly, CIAV antibodies in serum and egg yolks samples of the SPF laying hens were detected by ELISA assays. The results showed that CIAV antibodies in serum and egg yolks were 62% positive and 57% positive, respectively. Then, DNA was extracted from the NDV vaccines and SPF chicken embryonated eggs, and detected by molecular virology assays. The results showed that three assays for pathogens in embryonated eggs had similar positive rates (35.8%). And the sequences of CIAV from SPF embryos and NDV vaccines consisted of 2,298 nucleotides (nt) with 100% homology. The new full-length genome of CIAV was designated SDSPF2020 (Genbank accession number: MW660821). Data showed SDSPF2020 had the sequence similarities of 95.8–99.6% with reference strains, and shared the highest homology with the Chinese strain HLJ15125. These results strongly suggested that exogenous CIAV contamination is most likely caused by wild virus infection in SPF flocks and vertical transmission to chicken embryos. Collectively, this study illustrated that vertical transmission of CIAV from a SPF layer breeder flock to embryos was a non-neglible way for exogenous virus contamination in vaccine production.

Genomic Characteristics of a Chicken Infectious Anemia Virus in Contaminated Attenuated Vaccine

Chicken infectious anemia virus (CIAV) can be transmitted by contaminated live vaccines, and causes huge economic losses. This study evaluated the contamination status of CIAV in 24 batches of vaccines by recombinase-aided amplification assay (RAA), fluorescence quantitative PCR and dot blot assay, and then found a contaminated attenuated vaccine. The whole genome of the CIAV contaminant was then sequenced and named JS2020-PFV (Genbank accession number: MW234428, 2296bp). It showed 94.5 to 99.9% identities with reference strains and shared the closest evolution relationship with AB1K strain which was isolated from a chicken farm in Turkey. All of these suggested that the use of CIAV contaminated live vaccine may be one of the reason for its epidemic in poultry.

Genomic Sequence and Pathogenicity of the Chicken Anemia Virus Isolated From Chicken in Yunnan Province, China

Chicken anemia virus (CAV), which has been reported in many countries, causes severe anemia and immunosuppression in chickens. In this study, a CAV strain YN04 belonging to genotype A was first identified from infected chickens in Yunnan province, China. Moreover, the animal infection experiments further confirmed that the strain YN04 is a highly pathogenic strain, which can cause 86.67% mortality in chickens in the infection group. The mean death time of infected chickens was 13.1 days post infection (dpi). CAV infection induced severe anemia with significant decrease in packed cell volume (PCV), and serious atrophy and lesion of thymus and bursa with high viral load at 14 dpi. Besides, CAV infection caused a sharp decrease in chicken body weight and immune organ indices including the ratio of thymus or bursa to body weight at 21 dpi, which displayed the potential immunosuppression state at this stage. These findings enrich the epidemiological data on CAV and may provide information for preventing its further spread in Yunnan province, China.

Molecular Epidemiology and Pathogenic Characterization of Novel Chicken Infectious Anemia Viruses in Henan Province of China

Chicken infectious anemia (CIA) is an immunosuppressive disease caused by the chicken infectious anemia virus (CIAV) resulting in heavy economic losses once an outbreak is established. This study conducted a systematic analysis of the epidemiology and pathology of CIA in Henan province, China. A total of 437 clinical tissue samples and 120 poultry disease-related live attenuated vaccines were collected during 2017–2020; of which 45 were positive for CIAV nucleic acid, with a positive rate of 8.08%. Our results showed that genome sequence similarity among a total of 12 CIAV isolates was high, and ranged from 97.1 to 99.3%, and their similarity to the vaccine strains Cux-1 and Del-Ros ranged from 97.8 to 98.6%. However, There were mutations in the locus of the major capsid proteins VP1, VP2, and VP3 among all isolates. The subsequent sequence analysis indicated that the isolates of HN-4 and HN-8 showed genetic recombination and follow up animal experiments revealed that HN-4 might be a pathogenic strain. Our results reveal that both field infection and non-CIAV vaccines contamination promote the epidemiology of CIAV in China and some dominant epidemic viruses have undergone recombination and evolution. This study provides important information to help with the prevention and control of CIAV in the poultry industry.

Genomic Characterization of Chicken Anemia Virus in Broilers in Shandong Province, China, 2020–2021

Chicken infectious anemia (CIA), caused by chicken anemia virus (CAV), is an immunosuppressive disease characterized by growth retardation, aplastic anemia, lymphoid depletion, and immunodepression in young chickens. In this study, 33 CAV strains were isolated from broilers in Shandong Province during 2020–2021. Phylogenetic analysis of full-length genome sequences showed that most CAV strains isolated in this study were scattered across different branches, but mainly clustered in two genotypes, indicating a certain regional characteristic. Analysis of VP1 protein identified several amino acid substitutions which were relevant with the virulence and virus spread efficiency. Interestingly, four putative DNA recombination events were detected in the genomes of novel isolated CAV strains. In summary, this study demonstrated a genomic diversity of CAV in broilers isolated in Shandong Province during 2020–2021, and provided information for the further study of CAV molecular epidemiology and viral evolution.

Whole genome analysis and molecular characterization of chicken infectious anemia virus from an outbreak in a layer flock reveals circulation of genogroup IIIb in South India

The complete genome (2298 nucleotides) of the economically important and immunosuppressive, chicken infectious anemia virus (CAV), from a disease outbreak in a layer flock is discussed. This is the first report of a complete genome sequence of CAV from India. The phylogenetic analyses grouped this isolate with CAV genogroup IIIb based on both complete genome and capsid protein (VP1) sequences. The analyses further revealed the presence of CAV genogroups II, IIIa and IIIb in India. The VP1 sequence identity ranged between 84.4 to 99.3% with that of the Indian isolates and carried a unique substitution at position 447 (serine instead of threonine). Two novel amino acid substitutions were observed at position 52 of VP1 (serine instead of proline) and at position 26 of VP2 (asparagine instead of serine). Sequence analyses of VP1, VP2 and VP3 suggested that the isolate could be attenuated. Comparison with CAV variants, isolated from mammalian species, showed similarities in the numbers of certain transcription factor binding sites in the non-coding regions. Recombination analysis detected no recombination events in this isolate. Further investigations are needed to understand the implications of the unique features of this isolate on viral virulence.

Molecular characterization of chicken anemia virus in Guangxi Province, southern China, from 2018 to 2020

Background

Chicken anemia virus (CAV) causes chicken infectious anemia, which results in immunosuppression; the virus has spread widely in chicken flocks in China.

Objectives

The aim of this study was to understand recent CAV genetic evolution in chicken flocks in Guangxi Province, southern China.

Methods

In total, 350 liver samples were collected from eight commercial broiler chicken farms in Guangxi Province in southern China from 2018 to 2020. CAV was detected by conventional PCR, and twenty CAV complete genomes were amplified and used for the phylogenetic analysis and recombination analysis.

Results

The overall CAV-positive rate was 17.1%. The genetic analysis revealed that 84 CAVs were distributed in groups A, B, C (subgroups C1-C3) and D. In total, 30 of 47 Chinese CAV sequences from 2005-2020 belong to subgroup C3, including 15 CAVs from this study. There were some specific mutation sites among the intergenotypes in the VP1 protein. The amino acids at position 394Q in the VP1 protein of 20 CAV strains were consistent with the characteristics of a highly pathogenic strain. GX1904B was a putative recombinant.

Conclusions

Subgroup C3 was the dominant genotype in Guangxi Province from 2018–2020. The 20 CAV strains in this study might be virulent according to the amino acid residue analysis. These data help improve our understanding of the epidemiological trends of CAV in southern China.

Occurrence of Chicken Infectious Anemia Virus in Industrial and Backyard Tunisian Broilers: Preliminary Results

Chicken infectious anemia virus (CIAV) is an economically important and widely distributed immunosuppressive agent in chickens. This study performed an epidemiological investigation on CIAV circulation in 195 Tunisian broilers, belonging to 13 lots from five industrial farms and in one rural farm. Fifteen animals were detected positive by a VP1 nested PCR. The amplicons were molecularly characterised by complete genome sequencing. All positive samples obtained in this study were from the rural farm, whereas the industrial farms sampled were negative. Nucleotide and amino acid sequence analyses showed a high degree of similarity among the sequences obtained, suggesting the circulation of a single CIAV strain in the positive lot. Phylogenetic analysis based on the CIAV VP1 nucleotide sequence and/or the complete genome showed that the sequences obtained in this study clustered with CIAV strains previously detected in Tunisia, Italy and Egypt, belonging to genogroup II. Our results highlight the need for constant CIAV surveillance in backyard chicken production.

Synergistic pathogenesis of chicken infectious anemia virus and J subgroup of avian leukosis virus

As important immunosuppressive viruses, chicken infectious anemia virus (CIAV) and subgroup J avian leukosis virus (ALV-J) have caused huge economic losses to the poultry industry globally. Recently, the co-infection of CIAV and ALV-J frequently occurred in the domestic chicken flocks in China. However, the synergistic pathogenesis of CIAV and ALV-J has not been fully investigated. Here, a co-infection study was performed to further understand the potential synergistic pathogenesis of CIAV and ALV-J. In vitro study showed that CIAV could promote the replication of ALV-J in HD11 cells, but ALV-J could not increase the replication of CIAV. Chicken infection study showed both CIAV and ALV-J with synergistic effects caused significant body weight loss to the infected chickens. Although ALV-J had no effect on CIAV viral shedding and tissue load, CIAV did significantly increase ALV-J viremia, viral shedding and tissue load in the co-infection group. Moreover, both CIAV and ALV-J could significantly inhibit the humoral immunity to H9N2 influenza virus and serotype 4 fowl adenovirus (FAdV-4). All these data demonstrate the synergistic pathogenesis for the co-infection of CIAV and ALV-J, and highlight the positive effect of CIAV on the pathogenesis of ALV-J.

Isolation and Molecular Characteristics of a CIAV Isolate From Pigeons, China

Chicken infectious anemia virus (CIAV) mainly infects chickens and causes immunosuppression. In this study, a CIAV isolate, designated as Pigeon-CIAV-1906, was efficiently isolated from two sick pigeons by inoculating the samples into MSB1 cells. The genome of Pigeon-CIAV-1906 was amplified by PCR and analyzed. The genome size of Pigeon-CIAV-1906 was 2,298 bp with the highest homology (99.5%) to Jilin strain (JL14023) and the lowest homology (91.5%) to Brazil strain (KY024579), which phylogenetically clustered into Group A. Notably, several amino acids such as 139K and 394Q related with high virulence were found in the VP1 of Pigeon-CIAV-1906. The isolation of Pigeon-CIAV-1906 and its molecular characteristics provide evidence for the cross-transmission of CIAV from chicken to pigeon and give novel insights into the molecular epidemiology of CIAV.

Genetic Heterogeneity among Chicken Infectious Anemia Viruses Detected in Italian Fowl

Chicken infectious anemia virus (CIAV) is a pathogen of chickens associated with immunosuppression and with a disease named chicken infectious anemia. The present survey reports an epidemiological study on CIAV distribution in Italian broiler, broiler breeder and backyard chicken flocks. Twenty-five strains were detected by a specifically developed nested PCR protocol, and molecularly characterized by partial VP1 gene or complete genome sequencing. Viral DNA amplification was successfully obtained from non-invasive samples such as feathers and environmental dust. Sequence and phylogenetic analysis showed the circulation of field or potentially vaccine-derived strains with heterogeneous sequences clustered into genogroups II, IIIa, and IIIb. Marker genome positions, reported to be correlated with CIAV virulence, were evaluated in field strains. In conclusion, this is the first survey focused on the molecular characteristics of Italian CIAVs, which have proved to be highly heterogeneous, implementing at the same time a distribution map of field viruses worldwide.

Molecular evolution and pathogenicity of chicken anemia virus isolates in China

Chicken infectious anemia (CIA), caused by chicken anemia virus (CAV), is an important immunosuppressive disease that seriously threatens the global poultry industry. Here, we isolated and identified 30 new CAV strains from CAV-positive flocks. The VP1 genes of these strains were sequenced and analyzed at the nucleotide and amino acid levels and were found to have very similar nucleotide sequences (> 97% identity); however, they showed 93.9-100.0% sequence identity to the VP1 genes of 55 reference strains. Furthermore, alignment of the deduced amino acid sequences revealed some unique mutations. Phylogenetic analysis indicated the division of VP1 amino acid sequences into two groups (A and B) and four subgroups (A1, A2, A3 and A4). Interestingly, 22 of the newly isolated strains and some Asian reference strains belonged to the A1 group, whereas the remaining eight new isolates belonged to the A3 group. To evaluate the pathogenicity of the epidemic CAV strains from China, the representative strains CAV-JL16/8901 and CAV-HeN19/3001 and the reference strain Cux-1 were selected for animal experiments. Chickens infected with the isolates and reference strain all showed thymus atrophy and bone marrow yellowing. The mortality rates for CAV-JL16/8901, CAV-HeN19/3001, and the reference strain was 30%, 20%, and 0%, respectively, indicating that the epidemic strains pose a more serious threat to chickens. We not only analyzed the molecular evolution of the epidemic strains but also showed for the first time that the epidemic strains in China are more pathogenic than reference strain Cux-1. Effective measures should be established to prevent the spread of CIA in China.

Epidemiology, molecular characterization, and recombination analysis of chicken anemia virus in Guangdong province, China

Chicken anemia virus (CAV) causes severe anemia and immunosuppression in young chickens and a compromised immune response in older birds, resulting in great economic losses to the poultry industry worldwide. Here, we report the molecular epidemiology and characterization of CAV circulating in poultry in Guangdong province, China. Ninety-one of 277 chickens collected from 2016 to 2017 were CAV positive. Full-genome sequencing revealed the presence of eight separate strains. Phylogenetic analysis based on the genome sequences obtained in this study and related sequences available in the GenBank database showed that all of the CAV isolates exhibit a close relationship to each other and belong to the same genotypic group. Putative recombination events were also detected in the genomes of the newly isolated CAVs. Collectively, our findings underscore the importance of CAV surveillance and provide information that will lead to a better understanding of the evolution of CAV.

Chicken infectious anaemia virus infections in chickens in northern Vietnam: epidemiological features and genetic characterization of the causative agent

Since the first report of chicken infectious anaemia virus (CIAV) in Vietnam in 2013, there have not been many studies focused on the detection of CIAV or the molecular characteristics of the virus. This study attempted to investigate the presence of CIAV in northern Vietnam by molecular-based methods. Regarding the spatial distribution of CIAV, the PCR-based results showed that CIAV was detected in 47 out of 64 farms (73.4%) and in all 10 investigated provinces. Of the 119 samples assayed by PCR, 74 (62.2%) tested positive for CIAV DNA. By arranging the samples into different categories, it was found that CIAV was detected at high rates (above 50%) based on all 4 evaluated criteria as follows: production type of chicken, housing system, flock size and age group. Different housing systems were significantly associated with the detection rates of CIAV (P = 0.003). By genetic analyses, all of the Vietnamese CIAVs were found to (i) lack substitutions related to attenuation substitutions, (ii) group separately from vaccine-like CIAVs and (iii) belong to genogroups G2 and G3 of CIAV. Because of the wide distribution of CIAV and because the virus was confirmed not to be vaccine-like viruses, it is suggested that further studies be conducted on the clinical form of chicken infectious anaemia, as well as the immunosuppressive effect of CIAV on chickens in Vietnam.RESEARCH HIGHLIGHTS Wide distribution of chicken infectious anaemia virus (CIAV) in northern Vietnam.Vietnamese CIAVs belong to genogroups G2 and G3 of CIAV.

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.

Cross-species transmission of poultry pathogens in backyard farms: ducks as carriers of chicken viruses

In backyard farms of Lao People's Democratic Republic, mixed-species rearing of poultry is a breeding-ground for cross-species transmission. Here, the epidemiology of viruses circulating among backyard poultry in Vientiane Province was assessed to guide future control strategies. Oral/tracheal and cloacal swabs, collected from 605 poultry (308 ducks, 297 chickens) between 2011 and 2015, were screened by PCR for Newcastle disease virus (NDV), coronavirus (CoV) and chicken anaemia virus (CAV). Chicken sera were screened for anti-NDV antibodies by ELISA. Statistical and phylogenetic analyses revealed transmission patterns and relationships. Closely related strains co-circulated in chickens and ducks. While CoV RNA was detected in oral/tracheal swabs of 9.3% of the chickens and 2.4% of the ducks, rates were higher in faecal swabs of both species (27.3% and 48.2%). RNA of infectious bronchitis virus (IBV) and duck CoV was found in faecal swabs of chickens (19.7% and 7.1%) and ducks (4.1% and 44.1%). Moreover, DNA of the generally chicken-specific CAV was detected in oral/tracheal swabs of chickens (18.1%) and, sporadically, of ducks (2.4%). Despite serological evidence of NDV circulation or vaccination (86.9%), NDV RNA was not detected. We found a high prevalence and indication for cross-species transmission of different CoV strains in backyard poultry. Interestingly, ducks served as biological, or at least mechanical, carriers of viral strains closely related not only to IBV, but also to CAV. Bird containment and poultry species separation could be first steps to avoid cross-species transmission and emergence of novel strains with broad host range and enhanced pathogenicity. RESEARCH HIGHLIGHTS High rates of avian viruses were detected by PCR in backyard poultry from Lao PDR. Diverse coronavirus and chicken anemia virus strains co-circulated. Phylogenetic analyses suggested virus transmission between chickens and ducks. Serological evidence of Newcastle disease was found, but viral RNA was not detected.

Chicken anemia virus in northern Vietnam: molecular characterization reveals multiple genotypes and evidence of recombination

Chicken anemia virus (CAV) has a ubiquitous and worldwide distribution in the chicken production industry. Our group previously reported a high seroprevalence of CAV in chickens from northern Vietnam. In the present study, tissue samples collected from a total of 330 broiler and breeder commercial chickens in eleven provinces of northern Vietnam were tested for CAV infection. All samples were collected from clinically suspected flocks and diseased birds. The CAV genome was detected in 157 out of 330 (47.58%) chicken samples by real-time PCR. The rate of CAV genome detection in young chickens at 2-3 weeks of age (61.43%), which had not been previously reported in Vietnam, was significantly higher than that in older chickens at 4-11 (44.83%) and 12-28 (35.71%) weeks of age. For nine representative CAV strains from broiler chickens, analysis of the entire protein-coding region of the viral genome was conducted. Phylogenetic analysis of the VP1 gene indicated that the CAVs circulating in northern Vietnam were divided into three distinct genotypes: II, III, and V. Only one of the nine Vietnamese CAV strains clustered with a vaccine strain (Del-Ros), whereas the other eight strains did not cluster with any vaccine strains. Among the three genotypes, genotype III was most widely found in northern Vietnam and this included three sub-genotypes (IIIa, IIIb, and IIIc). The Vietnamese CAV strains were closely related to the Chinese, Taiwanese, and USA strains. One strain was defined to be of genotype V, which is a newly reported CAV genotype. Moreover, recombination analysis suggests that this novel genotype V was generated by recombination between genotype II and sub-genotype IIIc.

Identification of nuclear localization signal and nuclear export signal of VP1 from the chicken anemia virus and effects on VP2 shuttling in cells

BACKGROUND

VP1 of the chicken anemia virus (CAV) is a structural protein that is required for virus encapsulation. VP1 proteins are present both in the nucleus and cytoplasm; however, the functional nuclear localization signal (NLS) and nuclear export signal (NES) of VP1 are still unknown. This study aimed to characterize the NLS and NES motifs of VP1 using bioinformatics methods and multiple-site fragment deletions, and investigate shuttling of VP2 from nucleus to cytoplasm by co-transfection with VP1.

METHODS

Two putative NLS motifs were predicted by the WoLF PSORT and NLStradamus programs from the amino acid sequence of VP1. Three NES motifs of VP1 were predicted by the NetNES 1.1 Server and ELM server programs. All mutants were created by multiple-site fragment deletion mutagenesis. VP1 and VP2 were co-expressed in cells using plasmid transfection.

RESULTS

A functional NLS motif was identified at amino acid residues 3 to 10 (RRARRPRG) of VP1. Critical amino acids 3 to 10 were significantly involved in nuclear import in cells and were evaluated using systematic deletion mutagenesis. Three NES motifs of VP1 were predicted by the NetNES 1.1 Server and ELM server programs. A functional NES was identified at amino acid residues 375 to 388 (ELDTNFFTLYVAQ). Leptomycin B (LMB) treatment demonstrated that VP1 export from nucleus to cytoplasm occurred through a chromosome region maintenance 1 (CRM1)-dependent pathway. With co-expression of VP1 and VP2 in cells, we observed that VP1 may transport VP2 from nucleus to cytoplasm.

CONCLUSION

Our data showed that VP1 of CAV contained functional NLS and NES motifs that modulated nuclear import and export through a CRM1-dependent pathway. Further, VP1 may play a role in the transport of VP2 from nucleus to cytoplasm.

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.

Molecular characterization of chicken infectious anemia virus from contaminated live-virus vaccines

The aim of this study was to investigate possible causes of the pervasiveness of chicken infectious anemia virus (CIAV) infection in chickens in recent years in China. A total of 14 batches of live-virus vaccines were examined using PCR to detect CIAV contamination, of which only 2 samples (a Newcastle disease vaccine and a fowl pox vaccine) tested positive for CIAV. These Newcastle and fowl pox vaccines were then inoculated into 1-day-old specific-pathogen-free chickens. Serum samples were collected from chickens infected with the PCR-positive vaccines, and these tested positive for CIAV-specific antibodies as tested using ELISA. In addition, DNA samples isolated from the serum samples also tested positive by PCR. The results indicated that the samples were contaminated with CIAV and identified 2 exogenous CIAV strains, designated CIAV-N22 and CIAV-F10, in the respective samples. The full genome sequences of these novel CIAV strains were sequenced and analyzed. Phylogenetic tree analysis indicated that the CIAV-F10 strain might represent a recombinant viral strain arising from the parental CIAV strains JQ690762 and KJ728816. Overall, the results suggested that vaccination with CIAV-contaminated vaccines contributed to the prevalence and spread of CIAV infection in chickens. Furthermore, the CIAV contaminant was likely subsequently transmitted to commercial chickens through congenital transmission. Our findings therefore highlight the need for more extensive screening of live-virus vaccines for poultry in China to reduce the threat of contamination with exogenous viruses.

Full genome sequences of chicken anemia virus demonstrate mutations associated with pathogenicity in two different field isolates in Egypt

Chicken anemia virus (CAV) is an important pathogen associated with immunosuppression in chicken. In this study, out of samples collected from 115 commercial poultry farms, 12 samples were CAV positive by PCR. Partial sequence and phylogenetic analysis of VP1 gene revealed that the detected viruses were clustered to genotype I (n = 3) and genotype II (n = 9). Motifs of both low (E144) and high pathogenic strains (T89, I125, Q141) were found in the three viruses of genotype I. Whereas genotype II viruses demonstrated the characteristic motifs of highly pathogenic strains (I75, T89, I125, Q141, and Q144). Three isolates representative of both genotypes (CAV/CA1, CAV/GZ1 and CAV/SK4) were selected for full genome sequencing and results revealed that the VP2 gene had two substitutions at V153 and E 175, while VP3 gene had only one substitution at C118. To evaluate virus pathogenicity, two isolates from each genotype (CAV/SK4 of genotype I and CAV/CA1 of genotype II) were intramuscularly inoculated in two groups of one-day-old specific pathogen free chicks. Eighteen days post inoculation, PCR detected CAV in 75 and 90% of chicks in group I and II; respectively. Mortalities in inoculated chicks were 5 and 20% and packed cell volume values were 0.21 and 0.19; respectively. CAV/CA1 and CAV/SK4 isolates showed pathogenic evidences at the level of genetic (Q141 and 394Q) with variable degree of virulence. In conclusion, the study reports the circulation of at least two genotypes of CAV among chicken population with mutation associated with pathogenicity.

Epidemiology and molecular characterization of chicken anaemia virus from commercial and native chickens in Taiwan

Chicken infectious anaemia (CIA) is a disease with a highly economic impact in the poultry industry. The infected chickens are characterized by aplastic anaemia and extreme immunosuppression, followed by the increased susceptibility to secondary infectious pathogens and suboptimal immune responses for vaccination. Commercially available CIA vaccines are routinely used in the breeders in Taiwan to protect their progeny with maternal-derived antibodies. However, CIA cases still occur in the field and little is known about the genetic characteristics of Taiwanese chicken anaemia viruses (CAVs). In this study, CAV DNA was detected in 72 of 137 flocks collected during 2010-2015. Among the PCR-positive samples, the coding regions of 51 CAVs were sequenced. Phylogenetic analysis of the VP1 gene revealed that, although most of Taiwanese CAVs belonged to genotypes II and III, some isolates were clustered into a novel genotype (genotype IV). Moreover, a Taiwanese isolate in this novel genotype IV appeared to be derived from a recombination event between genotypes II and III viruses. Five Taiwanese CAV isolates were highly similar to the vaccine strains, 26P4 or Del-Ros. Taken together, these results indicate that the sequences of CAVs in Taiwan are variable, and inter-genotypic recombination had occurred between viruses of different genotypes. Moreover, vaccine-like strains might induce clinical signs of CIA in chickens. Our findings could be useful for understanding the evolution of CAVs and development of a better control strategy for CIA.

Genomic Characterization of Recent Chicken Anemia Virus Isolates in China

Chicken anemia virus (CAV) causes diseases in young chickens, which include increased pathogenicity of secondary infectious agents, generalized lymphoid depletion, and immunodepression. In the present study, we have identified 22 CAV strains isolated from several commercial chicken farms in Northern China during 2014–2015. In addition, two CAVs were also isolated from stray mouse and dog feces, respectively. To our knowledge, this is the first report of identification of CAV from mouse and dog feces. Phylogenetic analysis of 121 full-length CAV genome sequences showed that all available CAV could be classified into eight lineages, supported by phylogenetic trees estimated using different methods. Furthermore, the 24 novel CAV sequences scattered across different branches, lack of clear spatio-temporal distribution characterization. Analysis of the 450 amino acids of VP1 protein identified 33 amino acid substitutions that were specific for CAVs from northern China. Putative gene recombination events were also detected in the genomes of newly isolated CAVs. In particular, a putative recombinant event was detected in the CAV-Dog genome with high statistical support. In summary, we established a robust classification system for CAV, revealed additional genomic diversity of CAV, and therefore, warranted additional efforts to explore CAV genomics and epidemiology.

Assessing the efficacy of an inactivated chicken anemia virus vaccine

BACKGROUND

Chicken anemia virus (CAV) is an immunosuppressive virus that causes chicken infectious anemia (CIA) which is a highly contagious avian disease. CAV causes major economic losses in the poultry industry worldwide. The current CAV vaccine is a live attenuated strain administered in the drinking water that risks horizontal infection of other chickens. The purpose of this study was to develop a novel vaccine against CAV that can be administered safely using a highly pathogenic isolate inactivated with β-propiolactone hydrolysis that would protect chicks from CAV.

METHODS

Hens were vaccinated twice intramuscularly with a novel CAV GD-G-12 inactivated vaccine and the humoral immune responses of the hens and offspring were monitored by ELISA. A heterologous intramuscular challenge using the CAV strain GD-E-12 was conducted in the chicks hatched from vaccinated or unvaccinated hens.

RESULTS

The vaccine strain, GD-G-12, was shown to be highly pathogenic prior to inactivation evidenced by thymic atrophy and bleeding, and weight loss. The inactivated vaccine was considered safe and showed no signs of pathogenicity. High titers of CAV specific antibodies were detected in the vaccinated hens and in their chicks, indicating vertical transfer of maternal antibodies. Furthermore, the chicks hatched from vaccinated hens were resistant to a heterologous CAV challenge and showed no signs of weight loss and thymic atrophy and bleeding.

CONCLUSION

Our studies are proof of principle that inactivated GD-G-12 might be a novel vaccine candidate to prevent CAV infection, and highlight the utility of using an inactivated virus for this vaccine.

Novel Gyroviruses, including Chicken Anaemia Virus, in Clinical and Chicken Samples from South Africa

Introduction. Chicken anaemia virus, CAV, was until recently the only member of the Gyrovirus genus. 6 novel gyroviruses, AGV2, HGyV1, and GyV3-6, have since been discovered in human and chicken samples. Methods. PCR amplification of the VP2 gene was used to detect AGV2/HGyV1, GyV3, and CAV in a range of clinical samples including stool, respiratory, CSF, and HIV-positive plasma. Screening of fresh local chicken meat was also performed. Results. AGV2/HGyV1 or GyV3 was detected in stools from healthy children (17/49, 34.7%) and patients with diarrhoea (22/149, 14.8%). 1.2% (3/246) nasopharyngeal respiratory samples were positive. No AGV2/HGyV1 or GyV3 was detected in nasal swabs from wheezing patients, in CSF from patients with meningitis, and in HIVpositive plasma. CAV was found in 51% (25/49) of stools from healthy children and 16% (24/149) in diarrhoea samples. Screening of 28 chicken samples showed a higher prevalence of gyrovirus (20/28, 71%) compared to CAV (1/28, 3.6%). Phylogenetic analysis of the CAV VP1 gene showed South African sequences clustering with Brazilian isolates from genotypes D2 and A2. Conclusion. Novel gyroviruses, including CAV, are present in the South African population with diarrhoea and respiratory illness as well as in healthy children. Their presence suggests an origin from chicken meat consumption.

Identification of a chicken anemia virus variant-related gyrovirus in stray cats in china, 2012

The chicken anemia virus (CAV), is a known member of the genus Gyrovirus and was first isolated from chickens in Japan in 1979. Some reports have also demonstrated that CAV can be identified in human stool specimens. In this study, a variant of CAV was detected using PCR with CAV-based primers in fecal samples of stray cats. The genome of CAV variant was sequenced and the results suggest that it could be a recombinant viral strain from parental CAV strains JQ690762 and AF311900. Recombination is an important evolutionary mechanism that contributes to genetic diversification. These findings indicate that CAV variant might have originated from CAV-infected chickens. The epidemiology and pathogenesis of this novel virus remains to be elucidated. This study underscores the importance of CAV surveillance and it presents the first evidence suggesting the possibility of CAV homologous recombination in cat.

Phylogenetic and molecular characterization of chicken anemia virus in southern China from 2011 to 2012

Chicken anemia virus (CAV) is an important pathogen that causes severe immunosuppression in young chickens. We have characterized 13 CAVs isolated from different commercial farms in southern China between 2011 and 2012. We discovered 92 variable residues compared to 37 other CAV complete genome sequences from other parts of the world listed in GenBank; these residues have not been previously observed. All of the Chinese CAV genomes that were characterized in this study had a glutamine at position 394, a hallmark of highly pathogenic CAVs. We also discovered that intra-group genetic recombination plays a role in generating genetic diversity in natural populations of CAV. The GD-J-12 isolate was a possible recombinant between GD-C-12 and GD-M-12 in the genomic region that encompassed both the coding and non-coding regions.

Phylogenetic analysis and genetic characterization of chicken anemia virus isolates from Cambodia

Three chicken anemia viruses (CAV) were detected by PCR during screening of field samples from village chickens collected in Cambodia in 2011/2012. Nearly full-length VP1 viral structural protein genes (nt 1-1,293) from the 3 CAV were sequenced and characterized. Phylogenetic analysis revealed that all 3 of the Cambodian CAV were clustered with CAV strains belonging to genotype II and were most closely related to CAV strains from Guangdong province, China. On the amino acid level, major substitutions were observed at 12 residues in the VP1 protein (positions 22, 75, 97, 125, 139, 144, 254, 287, 290, 370, 376, and 413) when compared with published reference CAV strains. In motifs associated with virulence, all Cambodian CAV had virulence-associated motifs composed of 75I, 89T, 125I, 139Q, 141Q, 144Q, and 394Q, which are commonly found in highly virulent genotype II viruses and some genotype III viruses. This is the first report of CAV isolated from village chickens in Southeast Asia as well as Cambodia.

Complete genome sequence analysis of a recent chicken anemia virus isolate and comparison with a chicken anemia virus isolate from human fecal samples in China

A new isolate of chicken anemia virus (CAV) was designated GD-1-12. GD-1-12 was isolated from a 12-day-old commercial broiler in Guangdong province, China, in 2012. The GD-1-12 CAV caused high mortality, severe anemia, thymic atrophy, and subcutaneous hemorrhage in commercial broilers. Here, we report the complete genome sequence of GD-1-12 CAV and comparison with the complete genome sequence of another CAV that was isolated from human fecal samples in China (GenBank accession no. JQ690762). The genomes of the two CAV isolates shared high homology, although a deletion was identified by comparison. The findings from this study provide additional insights into the molecular characteristics of the CAV genomes and should advance knowledge for continuous monitoring and, perhaps, preventing the spread of the virus in chickens as well as in humans.

Analysis of chicken anemia virus genome: evidence of intersubtype recombination

Background

Chicken anemia virus (CAV) is the causative agent of chicken infectious anemia. CAV putative intergenotypic recombinants have been reported previously. This fact is based on the previous classification of CAV sequences into three genotypes. However, it is unknown whether intersubtype recombination occurs between the recently reported four CAV genotypes and five subtypes of genome sequences.

Results

Phylogenetic analysis, together with a variety of computational recombination detection algorithms, was used to investigate CAV approximately full genomes. Statistically significant evidence of intersubtype recombination was detected in the parent-like and two putative CAV recombinant sequences. This event was shown to occur between CAV subgroup A1 and A2 sequences in the phylogenetic trees.

Conclusions

We revealed that intersubtype recombination in CAV genome sequences played a role in generating genetic diversity within the natural population of CAV.

Gallus Heat shock cognate protein 70, a novel binding partner of Apoptin

Background

Chicken anemia virus (CAV) infection of newly hatched chickens induces generalized lymphoid atrophy and causes immunosuppressive. VP3, also known as Apoptin, is non-structural protein of CAV. Apoptin specifically induces apoptosis in transformed or tumor cells but not in normal cells. In particular, there are no known cellular homologues of Apoptin hindering genetic approaches to elucidate its cellular function. Although a number of Apoptin-interacting molecules have been identified, the molecular mechanism underlying Apoptin's action is still poorly understood. To learn more about the molecular mechanism of Apoptin's action, we searched for Apoptin associated proteins.

Results

Using yeast two-hybrid and colony-life filter approaches we got five positive yeast clones. Through sequencing and BLASTed against NCBI, one of the clones was confirmed containing Gallus heat shock cognate protein 70 (Hsc70). Hsc70 gene was clone into pRK5-Flag plasmid, coimmunoprecipitation assay show both exogenous Hsc70 and endogenous Hsc70 can interact with Apoptin. Truncated Apoptin expression plasmids were made and coimmunoprecipitation were performed, the results show the binding domain of Apoptin with Hsc70 is located between amino acids 30-60. Truncated expression plasmids of Hsc70 were also constructed and coimmunoprecipitation were performed, the results show the peptide-binding and variable domains of Hsc70 are responsible for the binding to Apoptin. Confocal assays were performed and results show that under physiological condition Hsc70 is predominantly distributed in cytoplasm, whereas Hsc70 is translocated into the nuclei and colocalized with Apoptin in the presence of Apoptin in DF-1 cell. Functional studies show that Apoptin markedly down-regulate the mRNA level of RelA/p65 in DF-1 cell. To explore the effect of Hsc70 on Apoptin-mediated RelA/p65 gene expression, we have searched two Hsc70 RNAi sequences, and found that all of them dramatically inhibited the expression of endogenous Hsc70, with the #2 Hsc70 RNAi sequence being the most effective. Knockdown of Hsc70 show Apoptin-inhibited RelA/p65 expression was abolished. Our data demonstrate that Hsc70 is responsible for the down-regulation of Apoptin induced RelA/p65 gene expression.

Conclusion

We identified Gallus Hsc70 as an Apoptin binding protein and showed the translocation of Hsc70 into the nuclei of DF-1 cells treated with Apoptin. Hsc70 regulates RelA/p65 gene expression induced by Apoptin.

Molecular epidemiology of chicken anemia virus in commercial farms in China

Background

Chicken anemia virus (CAV) is the causative agent of chicken infectious anemia (CIA). A high prevalence of CAV has been reported in China. However, VP1 sequences of Chinese isolates show no clear genotype clustering or correlation with geographic origin. Therefore, the present study aimed to detect and characterize CAV isolates from China based on sequence and phylogenetic analysis of the VP1, VP2 and VP3 genes.

Results

Of 460 spleen samples tested by PCR, 47 (10.22%) were found to be positive for CAV. A total of 25 CAV, approximately full genomes, from different commercial farms were characterized. Phylogenetic analysis of the Chinese CAV sequences together with strains from different countries resulted in four distinct groups (A-D) with significant high bootstrap values. The Chinese viral sequences were located as four different clusters within groups A and D. All the Chinese CAV genomes characterized in this study had glutamine (Q) at amino acid position 394, which indicated that all are highly pathogenic. Mutations associated with attenuation and weaker reactivity with monoclonal antibody 2A9 were absent in the Chinese sequences.

Conclusions

We revealed that CAV prevalence was lower than that reported previously in commercial farms in China. We also showed four distinct sequence groups (A-D), and genetic variability in local CAV sequences that could be divided into four groups based on phylogenetic analysis.

Intragenomic rearrangement in TT viruses: a possible role in the pathogenesis of disease

A role for the ubiquitous Torque teno (TT) viruses in the pathogenesis of disease has not been resolved. In vivo and in vitro intragenomic rearrangement of TT virus genomes has been demonstrated. Replication in cell culture of a subviral molecule (411 bp) occurs through oligomerisation of RNA transcripts. Although the functions of the respective TT viral genes, as well as the newly formed genes in the rearranged subviral molecules, are largely unknown, certain similarities to genes of plant viruses of the family Geminiviridae will be described. A degree of similarity to certain cellular genes poses the question as to a role of molecular mimicry in the pathogenesis of autoimmune disease and diabetes.

Chicken anemia virus

Chicken anemia virus (CAV), the only member of the genus Gyrovirus of the Circoviridae, is a ubiquitous pathogen of chickens and has a worldwide distribution. CAV shares some similarities with Torque teno virus (TTV) and Torque teno mini virus (TTMV) such as coding for a protein inducing apoptosis and a protein with a dual-specificity phosphatase. In contrast to TTV, the genome of CAV is highly conserved. Another important difference is that CAV can be isolated in cell culture. CAV produces a single polycistronic messenger RNA (mRNA), which is translated into three proteins. The promoter-enhancer region has four direct repeats resembling estrogen response elements. Transcription is enhanced by estrogen and repressed by at least two other transcription factors, one of which is COUP-TF1. A remarkable feature of CAV is that the virus can remain latent in gonadal tissues in the presence or absence of virus-neutralizing antibodies. In contrast to TTV, CAV can cause clinical disease and subclinical immunosuppression especially affecting CD8+ T lymphocytes. Clinical disease is associated with infection in newly hatched chicks lacking maternal antibodies or older chickens with a compromised humoral immune response.

Relationship of Torque teno virus to chicken anemia virus

This chapter examines the correlation between Torque teno virus (TTV) and chicken anemia virus (CAV). Each has a circular single-stranded (ss)DNA genome with every one of its known open reading frames (ORF) on its antigenomic strand. This structure is distinct from those of circoviruses. The genomic sizes of TTV and CAV are different, 3.8 kb and 2.3 kb, respectively. While the spectrum of the TTV genome is enormously diverse, that of the CAV genome is quite narrow. Although a 36-nt stretch near the replication origin of TA278 TTV possesses more than 80% similarity to that of CAV, the sequence of the other genomic regions does not exhibit a significant similarity. Nevertheless, the relative allocation of ORFs on each frame in these viruses mimics each other. Three or more messenger RNA (mRNAs) are generated by transcription in both of them. The structural protein with the replicase domain is coded for by frame 1 in each virus, and a nonstructural protein with a phosphatase domain is coded for by frame 2. A protein on frame 3 in each virus induces apoptosis in transformed cells. Recently, we confirmed that apoptin is necessary for the replication of CAV. TTV has been proposed to constitute a new family, Anelloviridae. Considering these similarities and dissimilarities between CAV and TTV, it seems more reasonable to place CAV, the only member of genus Gyrovirus, into Anelloviridae together with TTV, or into a new independent family.

Replication of chicken anemia virus (CAV) requires apoptin and is complemented by VP3 of human torque teno virus (TTV)

To test requirement for apoptin in the replication of chicken anemia virus (CAV), an apoptin-knockout clone, pCAV/Ap(-), was constructed. DNA replication was completely abolished in cells transfected with replicative form of CAV/Ap(-). A reverse mutant competent in apoptin production regained the full level of DNA replication. DNA replication and virus-like particle (VLP) production of CAV/Ap(-) was fully complemented by supplementation of the wild-type apoptin. The virus yield of a point mutant, CAV/ApT(108)I, was 1/40 that of the wild type, even though its DNA replication level was full. The infectious titer of CAV was fully complemented by supplementing apoptin. Progeny virus was free from reverse mutation for T(108)I. To localize the domain within apoptin molecule inevitable for CAV replication, apoptin-mutant expressing plasmids, pAp1, pAp2, pAp3, and pAp4, were constructed by deleting amino acids 10-36, 31-59, 59-88 and 80-112, respectively. While Ap1 and Ap2 were preferentially localized in nuclei, Ap3 and Ap4 were mainly present in cytoplasm. Although complementation capacity of Ap3 and Ap4 was 1/10 of the wild type, neither of them completely lost its activity. VP3 of TTV did fully complement the DNA replication and VLP of CAV/Ap(-). These data suggest that apoptin is inevitable not only for DNA replication but also VLP of CAV. The common feature of apoptin and TTV-VP3 presented another evidence for close relatedness of CAV and TTV.

Unraveling the puzzle of human anellovirus infections by comparison with avian infections with the chicken anemia virus

Current clinical studies on human annelloviruses infections are directed towards finding an associated disease. In this review we have emphasized the many similarities between human anellovirus and avian circoviruses and the cell and tissue types infected by these pathogens. We have done this in order to explore whether knowledge acquired from natural and experimental avian infections could reflect and be extrapolated to the less well-characterized human annellovirus infections. The knowledge gained from the avian system may provide suggestions for decoding the enigmatic human anellovirus infections, and finding the specific disease or diseases caused by these human anellovirus infections. Each additional parallelism between chicken anemia virus (CAV) and Torque teno virus (TTV) further strengthens this premise. As we have seen information from human infections can also be used to better understand avian infections as well. Increased attention must be focused on the "hidden" or unrecognized, seemingly asymptomatic effects of circovirus and anellovirus infections. Understanding the facilitating effect of these infections on disease progression caused by other pathogens may help to explain differences in outcome of complicated poultry and human diseases. The final course of a pathogenic infection is determined by variations in the state of health of the host before, during and after contact with a pathogen, in addition to the phenotype of the pathogen and host. The health burden of circoviridae and anellovirus infections may be underestimated, due to lack of awareness of the need to search past the predominant clinical effect of identified pathogens and look for modulation of cellular-based immunity caused by co-infecting circoviruses, and by analogy, human anneloviruses.

Identification of chicken anemia virus putative intergenotype recombinants

Chicken anemia virus (CAV), the only member of the genus Gyrovirus in the family Circoviridae is the pathogen of chicken infectious anemia. It is unknown whether homologous recombination happens between CAV strains. In order to gain insight into this matter, we have performed a phylogenetic analysis of full-length CAV strains isolated to detect possible recombination events. Two putative recombinants, SD24, SD22 and the putative parental-like strains were identified with the use of SimPlot program. The two mosaic CAV consist of a novel genotype in the phylogenetic tree. It suggests that homologous recombinant plays roles in generating genetic diversity in natural populations of CAV.