Detection and differentiation of chicken anemia virus isolates by using the polymerase chain reaction

Detection of chicken chapparvovirus 2 in chickens with hemorrhagic hepatitis in Japan

Chicken chaphamaparvovirus causes diarrheal symptoms and can be detected in fecal samples. This study reports the detection of chicken chapparvovirus 2 in debilitated chickens with hemorrhagic hepatitis at a broiler farm in Japan. After euthanasia and necropsy, liver hemorrhage was observed. Nuclear inclusion bodies in the hepatocytes were identified using histological analysis. High-throughput sequencing analysis using RNA from livers of three affected chickens revealed infection by chicken chapparvovirus 2 and chicken anemia virus. Polymerase chain reaction analysis showed that all three chickens were positive for chicken chapparvovirus 2, and only one was positive for both chicken chapparvovirus 2 and chicken anemia virus. In conclusion, chicken chapparvovirus 2 causes infection in chickens in Japan and might be involved in hemorrhagic hepatitis.

A new rapid and sensitive method for detecting chicken infectious anemia virus

Since the chicken infectious anemia virus (CIAV) was discovered in 1979, which has been reported as an economically significant and immunosuppressive poultry disease in the world. A novel clinical detection method for the prevention and control of CIAV in the poultry sector is urgently needed. Here, we established a real-time recombinase-aided amplification assay (RAA) for CIAV on-site with a rapid, highly sensitive, strongly specific, low-cost, and simple operational molecular diagnosis detection method. The primers and probe were developed using the CIAV VP2 gene sequence, which has a 117-bp specific band. This assay, which could be carried out at 41°C and completed in 30 min without cross-reactivity with other viruses, had the lowest detection limit of 10 copies of CIAV DNA molecules per reaction. Furthermore, the kappa value of this assay was 0.947, the sensitivity was 93.33%, and the specificity was 100% when compared to the real-time quantitative polymerase chain reaction assay (real-time qPCR). These results indicate that using a real-time RAA assay to detect CIAV on-site could be beneficial. In the future, the real-time RAA test may be a regular assay for the prevention and control of CIAV, as well as help the reduction of economic losses in the poultry business.

Molecular Detection of a Novel Fowl Adenovirus Serotype-4 (FadV-4) from an Outbreak of Hepatitis Hydropericardium Syndrome in Commercial Broiler Chickens in Egypt

Hepatitis hydropericardium syndrome (HHS) is an acute infectious disease caused by fowl adenovirus serotype-4 (FAdV-4), which mainly affects broilers aged 4-5 wk. During the winter of January 2021, a 32-day-old broiler flock (Cobb-500) suffered from unusually high mortality (15%) in the Alexandria Governorate, Egypt. The chickens showed depression, ruffled feathers, and greenish diarrhea besides the typical pathologic features of suspected HHS involving flabby hearts, accumulation of a straw-colored fluid in the pericardial sacs, and pale, enlarged hemorrhagic and friable livers with necrotic foci. The kidneys exhibited edema with uric acid depositions. Histopathologic examination of bird livers naturally infected with HHS showed multifocal areas of necrosis, vascular changes, and basophilic intranuclear inclusion bodies (INIB) in the hepatocytes. Molecular identification of the causative agent was accomplished by PCR and sequence analysis of the hyper-variable regions of loop 1 of the hexon gene of fowl aviadenovirus. A pathogenic strain of the novel genotype-4 (FAdV-4) was demonstrated, closely similar to the Israeli strain IS/1905/2019, with an identity of 98%. This is the first report to identify FADV-4 in Egypt, prompting further studies to elucidate its epidemiologic role in all poultry sectors and associated economic losses to provide insights to its control and prevention.

A primary occurrence of inclusion body hepatitis in absence of predisposing agents in commercial broilers in Iran: a case report

BACKGROUND

Fowl adenoviruses (FAdVs) associated with certain clinical diseases including inclusion body hepatitis (IBH) have become of considerable importance in the poultry industry. Currently, an increasing number of IBH outbreaks in different parts of Iranian poultry industries is a growing concern. Infectious bursal disease virus (IBDV) or chicken infectious anemia virus (CIAV) have historically been incriminated as predisposing factors for FAdVs to cause IBH. Furthermore, some have speculated whether IBDV vaccine strains impact on IBH clinical manifestation. The present report assesses the potential predisposing role of IBDV, CIAV, and infectious bursal disease) IBD( vaccine strains for FAdVs in the course of an IBH occurrence in the field.

CASE DESCRIPTION

90000 day-old broiler chickens with the same parent source were housed, at 4 day-interval, in two commercial farms in Shiraz, Iran. Increased mortality with lesions of hepatitis, suggestive of IBH, started in the primitive farm right after blind prescription of IBD vaccine at the age of 12-days-old. Consequently, IBD vaccination was postponed for the apparently healthy chickens of the other farm in which chickens were monitored for the occurrence of IBH afterwards. Laboratory examination was followed by histopathology and polymerase chain reaction (PCR) on liver, cloacal bursa, and thymus samples to determine the involvement of FAdV, IBDV, and CIAV in the occurrence of the disease.

FINDINGS/TREATMENT AND OUTCOME

No evidence was found to support the predisposing role of neither IBD vaccination nor IBDV/CIAV infection in this IBH occurrence. The results also demonstrated a primary role of the FAdV-11 as a causal agent of the IBH occurrence.

CONCLUSION

The findings suggest that certain FAdVs are pathogenic enough to primarily induce IBH in young broilers.

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.

Loop-mediated isothermal amplification assay for detection of four immunosuppressive viruses in chicken

Loop-mediated isothermal amplification (LAMP) methods to detect chicken infectious anemia virus (CIAV), reticuloendotheliosis virus (REV), and Marek's disease virus (MDV), and a reverse transcription (RT)-LAMP assay to detect infectious bursal disease virus (IBDV), were developed. The CIAV-LAMP, REV-LAMP, MDV-LAMP, and IBDV-RT-LAMP methods were performed using four sets of six primers targeting the VP1 gene of CIAV, the gp90 gene of REV, the Meq gene of MDV, and the VP2 gene of IBDV. The results (a change in color) were observed visually. The methods showed high specificity and sensitivity. The detection limits were 50 genomic copies of CIAV, 16 genomic copies of REV, 20 genomic copies of MDV, and 250 genomic copies of IBDV. When used to test clinical samples, the results of the LAMP assays were in 100% agreement with a previously described PCR. Therefore, the LAMP assays are simple, rapid, highly sensitive, and specific methods for detecting four immune-suppressive viruses.

Transcriptomic Profiling of Virus-Host Cell Interactions following Chicken Anaemia Virus (CAV) Infection in an In Vivo Model

Chicken Anaemia Virus (CAV) is an economically important virus that targets lymphoid and erythroblastoid progenitor cells leading to immunosuppression. This study aimed to investigate the interplay between viral infection and the host's immune response to better understand the pathways that lead to CAV-induced immunosuppression. To mimic vertical transmission of CAV in the absence of maternally-derived antibody, day-old chicks were infected and their responses measured at various time-points post-infection by qRT-PCR and gene expression microarrays. The kinetics of mRNA expression levels of signature cytokines of innate and adaptive immune responses were determined by qRT-PCR. The global gene expression profiles of mock-infected (control) and CAV-infected chickens at 14 dpi were also compared using a chicken immune-related 5K microarray. Although in the thymus there was evidence of induction of an innate immune response following CAV infection, this was limited in magnitude. There was little evidence of a Th1 adaptive immune response in any lymphoid tissue, as would normally be expected in response to viral infection. Most cytokines associated with Th1, Th2 or Treg subsets were down-regulated, except IL-2, IL-13, IL-10 and IFNγ, which were all up-regulated in thymus and bone marrow. From the microarray studies, genes that exhibited significant (greater than 1.5-fold, false discovery rate <0.05) changes in expression in thymus and bone marrow on CAV infection were mainly associated with T-cell receptor signalling, immune response, transcriptional regulation, intracellular signalling and regulation of apoptosis. Expression levels of a number of adaptor proteins, such as src-like adaptor protein (SLA), a negative regulator of T-cell receptor signalling and the transcription factor Special AT-rich Binding Protein 1 (SATB1), were significantly down-regulated by CAV infection, suggesting potential roles for these genes as regulators of viral infection or cell defence. These results extend our understanding of CAV-induced immunosuppression and suggest a global immune dysregulation following CAV infection.

Tribasic copper chloride toxicosis in commercial broiler chicks

Two broiler chicken houses containing 17,500 chicks each experienced an extreme elevation in chick mortality beginning on day 3 after placement. Clinical signs observed upon farm visit included numerous small chicks for their age; depressed, lethargic, and comatose chicks; and chicks huddling near feed pans and under heaters. Necropsied chicks were markedly pale and had atrophy of the thymus and bursa, swollen and edematous proventriculus, erosions in the koilin and in the proventricular-ventricular junction, pale kidneys, and yellowish to brownish-orange liver often with linear pale areas. The chicks had watery blood and hematocrits measured from 9.5% to 18%. Chicken infectious anemia was initially suspected based on the clinical signs and gross lesions. Histopathology revealed multifocal acute hepatic degeneration and necrosis with golden-brown pigment in the cytoplasm of hepatocytes and Kupffer cells, moderate to severe koilin degeneration and fragmentation, multifocal mild to moderate proventricular necrosis, mild to moderate necrosis and loss of enterocytes, blunting of small intestinal villi, lymphoid depletion in the thymus and bursa, erythrophagocytosis in the liver and spleen, and acute renal tubular degeneration and necrosis. Special stains revealed mild to abundant accumulation of copper pigment in the cytoplasm of hepatocytes and iron pigment in the cytoplasm of Kupffer cells. Feed analysis revealed 2140 to 2393 parts per million of copper in the starter ration, and heavy metal analysis detected markedly elevated copper levels in formalin-fixed samples of the liver. Excessive amounts of tribasic copper chloride in the starter ration caused copper toxicosis in these chicks. Similar clinical signs and lesions were reproduced when the suspect feed was used in an experimental pen trial.

Molecular characterization of chicken anemia virus circulating in chicken flocks in egypt

Introduction. Although many previous studies reported detection of chicken anemia virus (CAV) in Egypt since 1990, genomic characterization of this circulating CAV has not been published. In the present study, four nucleotide sequences of detected CAV were genetically characterized. Methods. These nucleotide sequences were obtained from commercial chicken flocks in two different locations of Egypt during 2010. The target region for sequencing was 675 bp nucleotide of partial coding region of VP1 protein. The nucleotide and deduced amino acid sequences of the detected CAV were aligned and compared to worldwide CAV isolates including commonly used vaccine strains. Phylogenetic analysis of these sequences was also carried out. Results. Our results showed that all the Egyptian CAV sequences were grouped in one group with viruses from diverse geographic regions. This group is characterized by amino acids profile ⁷⁵I, ⁹⁷L, ¹³⁹Q, and ¹⁴⁴Q in VP1. The phylogenetic and amino acid analyses of deduced amino acid indicated that the detected CAV sequences differ from CAV vaccine strains. Conclusion. This is the first report that describes molecular characterization of circulating CAV in Egypt. The study showed that the detected CAV, in Egypt are field viruses and unrelated to vaccine strains.

Fowl adenovirus Group I as a causal agent of inclusion body hepatitis/hydropericardium syndrome (IBH/HPS) outbreak in brazilian broiler flocks

Commercial broiler flocks from a farm located in the State of São Paulo, Brazil, presented diarrhea, depression, increased mortality and poor weight gain. Upon post-mortem examination, classical signs of Inclusion Body Hepatitis/Hydropericardium Syndrome (IBH/HPS) were observed, including enlarged pale yellow-colored livers and straw-colored liquid in the pericardial sac. In addition, gross lesions were also observed in the kidneys, pancreas, thymus, intestines and gallbladder. Samples of these organs were analyzed by PCR for the detection of the hexon gene of the Fowl Adenovirus (FAdVs) Group I. The results were positive for both flocks (A and B) assayed by PCR. The macroscopic lesions associated with the detection of FAdV Group I by PCR in several of these affected organs allowed for the identification of IBH/HPS. In fact, this is the first report in Brazil of IBH/HPS in broilers, which identifies FAdVs group I as a causal agent of the disease. These findings may contribute to the worldwide epidemiology of the adenovirus-mediated hepatitis/hydropericardium syndrome.

Interactions ofPlasmodium juxtanucleareand chicken anaemia virus: establishing a model

The pathogensPlasmodium juxtanucleareand chicken anaemia virus (CAV) are easily transmitted and potentially harmful to chickens. In this study, we established an experimental model to investigate the effects of avian malaria caused byP. juxtanuclearein white leghorn specific-pathogen-free (SPF) chicks previously immunosuppressed with CAV. Parasitaemia, haematological variables and clinical and pathological parameters were determined in four different experimental groups: chicks coinfected by CAV andP. juxtanuclearestrain (Coinfected group), chicks exclusively infected by CAV (CAV group) orP. juxtanucleare(Malaria group) and uninfected chicks (Control group). Our data demonstrated thatP. juxtanucleareparasitaemia was significantly higher in the Coinfected group. Furthermore, haematological parameters, including the RBC, haematocrit and haemoglobin concentration were significantly reduced in coinfected chicks. In agreement with the changes observed in haematological features, the mortality among coinfected chicks was higher compared with animals with single infections. Clinical analysis indicated moderate changes related to different organs size (bursa of Fabricius, heart and liver) in coinfected birds. The experimental coinfection of SPF chickens withP. juxtanucleareand CAV may represent a research tool for the study of avian malaria after CAV immunosuppression, enabling measurement of the impacts caused by different pathogens during malarial infection.

Epidemiological investigation of outbreaks of fowl adenovirus infection in commercial chickens in Korea

In total, 39 clinical cases of fowl adenoviruses (FAdV) infection in chickens (28 broiler, 7 native, and 4 layer chickens) between 2007 and 2010 in Korea were investigated. The FAdV types 4, 8b, and 11 comprised 18, 9, and 12 clinical cases, respectively. All FAdV type 4 cases showed clinical hydropericardium (HPS) lesions as well as inclusion body hepatitis (IBH), whereas all FAdV types 8b and 11 cases exhibited IBH lesions without HPS. All 3 types were detected in broiler (9-30 d old) and layer chickens (23-112 d old), whereas most native chickens (14-65 d old) were affected only by FAdV type 4. Infectious bursal disease virus and chicken infectious anemia virus were complications in 51.3% of FAdV cases, with mortalities of 55% to <0.1%. Chicken infectious anemia virus was detected in all native chicken cases. These results indicate that preventive measures against FAdV infection and immunosuppressive diseases on poultry farms should be implemented.

Viral diagnostics: will new technology save the day?

Technology for infectious agent detection continues to evolve, particularly molecular methods that first emerged in the mid-1970s. The goals of new technology in diagnostics, whether in humans or in animals, including poultry, are to achieve the highest sensitivity and specificity possible to accurately identify the infection status of an individual or flock in the shortest time possible. Ease of use, low cost and increased information from a single test (e.g. multiplexing) are also critical areas frequently targeted for improvement. New tests and modifications of current tests are reported often, and diagnostic tests are now commonly developed by commercial companies. As one would expect, most advances in diagnostic technology are applied first to human health, and then may be adapted to animal health if practical. In the present review the trends and novel innovative technologies in primarily viral diagnostics are reviewed and the practicality of these methods and application for poultry health are discussed briefly. Also, influenza will seem to be over-represented in viral diagnostics since it is frequently used as a proof-of-concept target for novel technology due to its importance for animal and public health. Finally, the review is intended to be a brief survey of some of the innovative diagnostic technologies reported in recent years. It is not entirely comprehensive of all technology and the author makes no claims or endorsements of any of the technology or products mentioned.

Quantification of chicken anaemia virus by competitive polymerase chain reaction

A quantitative method for chicken anaemia virus (CAV) was developed using competitive polymerase chain reaction (PCR). Competitive template was constructed by deletion of 33 nucleotides from a wildtype DNA clone of CAV. Quantification of CAV DNA molecules by the competitive PCR was rapid and highly reproducible when compared with conventional infectivity titration methods. The ratios of the viral DNA molecules and infectivity titres in MDCC-MSB1 cells varied between 1.3 and 3.55 log(10) among several isolates, suggesting the existence of different infection efficiencies to MDCC-MSB1 cells by isolates. The competitive PCR will be useful for studying CAV infection in vivo and/or in vitro.

Development and characterization of a potential diagnostic monoclonal antibody against capsid protein VP1 of the chicken anemia virus

Chicken anemia virus (CAV) is an important viral pathogen that causes anemia and severe immunodeficiency syndrome in chickens worldwide. In this study, a potential diagnostic monoclonal antibody against the CAV VP1 protein was developed which can precisely recognize the CAV antigen for diagnostic and virus recovery purposes. The VP1 gene of CAV encoding the N-terminus-deleted VP1 protein, VP1Nd129, was cloned into an Escherichia (E.) coli expression vector. After isopropyl-β-D-thiogalactopyronoside induction, VP1Nd129 protein was shown to be successfully expressed in the E. coli. By performing an enzyme-linked immunoabsorbent assay using two coating antigens, purified VP1Nd129 and CAV-infected liver tissue lysate, E3 monoclonal antibody (mAb) was found to have higher reactivity against VP1 protein than the other positive clones according to the result of limiting dilution method from 64 clones. Using immunohistochemistry, the presence of the VP1-specific mAb, E3, was confirmed using CAV-infected liver and thymus tissues as positive-infected samples. Additionally, CAV particle purification was also performed using an immunoaffinity column containing E3 mAb. The monoclonal E3 mAb developed in this study will not only be very useful for detecting CAV infection and performing histopathology studies of infected chickens, but may also be used to purify CAV particles in the future.

Production and diagnostic application of a purified, E. coli-expressed, serological-specific chicken anaemia virus antigen VP3

The aim of this study was to evaluate the production of chicken anaemia virus VP3 protein in different Escherichia coli strains and to address the diagnostic application of purified E. coli-expressed VP3 protein for the detection of chicken anaemia virus (CAV) infection and the development of an ELISA kit. Three E. coli strains, BL21, BL21 codonplus RP and BL21 pLysS, each harbouring a VP3 protein expressing plasmid, were investigated after induction to produce recombinant VP3 protein. After isopropyl-β-D-thiogalactoside (IPTG) induction, VP3 protein was successfully expressed in all three E. coli strains. The BL21 pLysS strain gave the best performance in terms of protein productivity and growth profile. In addition, the optimal culture temperature and IPTG concentration were found to be 0.25 mM and 20 °C, respectively. Using Ni-NTA-purified VP3 protein as an ELISA coating antigen, the purified VP3 was shown to be highly antigenic and able to discriminate sera from chickens infected with CAV from those that were uninfected during an evaluation of CAV infection serodiagnosis. A VP3-based ELISA demonstrated 100% (6/6 x 100%) specificity and sensitivities of 91.3% (21/23 x 100%) and 82.6% (19/23 x 100%) using cut-off values of the mean plus 2 SD and the mean plus 3 SD, respectively.

An Optimized Polymerase Chain Reaction Assay to Identify Avian Virus Vaccine Contamination with Chicken Anemia Virus

The use of embryonating chicken eggs in preparation of avian virus vaccines is the principle cause for contamination with Chicken anemia virus (CAV). Identification of CAV in contaminated vaccines relies on the expensive, tedious, and time-consuming practice of virus isolation in lymphoblastoid cell lines. The experience of the last 2 decades indicates that polymerase chain reaction is extending to replace most of the classic methods for detection of infectious agents. In the present report, a simple, rapid, and accurate polymerase chain reaction method for detection of CAV in poultry vaccines is described. Oligonucleotide primers homologous to highly conserved sequences of the VP1 gene were used to amplify a fragment of 676 bp. The developed assay was specific for detecting CAV from different sources, with no cross reactivity with many avian viruses. No inter- and intra-assay variations were observed. The analytical sensitivity of the test was high enough to detect 5 TCID50 (50% tissue culture infective dose) of the virus per reaction; however, different factors related to the vaccine matrix showed considerable effects on the detection limit. In conclusion, this method may represent a suitable alternative to virus isolation for identification of CAV contamination of poultry virus vaccines.

Development and evaluation of a loop-mediated isothermal amplification assay for rapid detection of chicken anaemia virus

AIM

Chicken anaemia virus (CAV) causes an economically important viral disease in chickens worldwide. The main aim of this study was to establish a rapid, sensitive and specific loop-mediated isothermal amplification (LAMP) assay for detecting CAV infection.

METHODS AND RESULTS

A set of four specific LAMP primers were designed based on the nucleotide sequence of the CAV VP2 gene, which encodes a nonstructural protein. These were used for the amplification of a specific target region of the VP2 gene. LAMP amplicons were successfully amplified and detected by DNA electrophoresis and by direct naked eye SYBR Green I visualization. A sensitivity test systematically demonstrated that the LAMP assay was superior to a conventional PCR assay with a minimum concentration limit of 100 fg compared to 10 ng for the conventional PCR. The specificity of the LAMP assay for CAV detection is consistent with conventional PCR. Using this established LAMP assay, infected and uninfected clinical samples obtained from an experimental farm were fully verified.

CONCLUSIONS

A novel nucleic acid-based approach of LAMP assay was successfully developed for detecting CAV infection.

SIGNIFICANCE AND IMPACT OF THE STUDY

In this study, these results indicate that the developed LAMP assay herein for CAV detection is a time-effective, simple, sensitive and specific test that can be used as an alternative approach in the future for large-scaled diagnosis on the farm of CAV infection.

Pathogenicity and growth characteristics of selected infectious laryngotracheitis virus strains from the United States

In a recent study, several US infectious laryngotracheitis virus (ILTV) strains and field isolates were genotyped by polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) into nine different genotypes. All of the commercial poultry isolates were identified within genotypes IV, V, and VI. Based on the PCR-RFLP, Group IV isolates were characterized as genetically identical to the chicken embryo origin (CEO) vaccines, Group V as genetically closely related to the CEO vaccines, and Group VI as genetically different to the vaccine strains. The objective of this study was to determine the pathogenicity and growth characteristics of six ILTV commercial poultry isolates as compared with the CEO vaccine. Two isolates representative of PCR-RFLP Groups IV, V, and VI were selected. Differences in disease severity, viral tissue distribution in chickens, and plaque formation ability in cell culture were observed among viral genotypes IV, V, and VI, and between V-A and V-B isolates. Mild respiratory clinical signs were produced by IV-A, IV-B and the CEO vaccine, while VI-A and VI-B isolates produced severe respiratory signs and severe depression, and during the peak of clinical signs both isolates were re-isolated from the conjunctiva, sinus, trachea and thymus. Similarly to Group VI isolates, V-A and V-B produced severe respiratory signs, depression, and were re-isolated from conjunctiva, sinus, and trachea; on cell culture, both isolates produced significant larger plaques than any of the other isolates analysed. Overall, differences in pathogenicity and growth characteristics were observed among genetically closely related US ILTV isolates; however, complete genomes will be necessary to identify molecular determinants linked to the pathogenic viral phenotypes.

Avian proteomics: advances, challenges and new technologies

Proteomics is defined as an analysis of the full complement of proteins of a cell or tissue under given conditions. Avian proteomics, or more specifically chicken proteomics, has focussed on the study of individual tissues and organs of interest to specific researchers. Researchers have looked at skeletal muscle and growth, and embryonic development and have performed initial studies in avian disease. Traditional proteomics involves identifying and cataloguing proteins in a cell and identifying relative changes in populations between two or more states, be that physiological or disease-induced states. Recent advances in proteomic technologies have included absolute quantification, proteome simplification and the ability to determine the turnover of individual proteins in a global context. This review discusses the current developments in this relatively new field, new technologies and how they may be applied to biological questions, and the challenges faced by researchers in this ever-expanding and exciting field.

Genome sequencing analysis of Brazilian chicken anemia virus isolates that lack MSB-1 cell culture tropism

Specific amino acid (aa) substitutions in VP1, VP2 and VP3 genes were reported as a distinctive feature of the American CIA-1 strain, characterized as having a variable rate of growth and tropism for different MSB-1 cell sublines [Renshaw RW, Soiné C, Weinkle T, O'Connell PH, Ohashi K, Watson S, et al. A hypervariable region in VP1 of chicken anemia virus mediates rate of spread and cell tropism in tissue culture. J Virol 1996;70(12):8872-8]. DNA sequencing of 878 nucleotides from twelve Brazilian CAV, eight of which tested for in vitro isolation in three different sources of MDCC-MSB1 cell line and identified as lacking capacity to propagate in any of these cells, were compared to sequence data available for CAV strains propagated or not in cell culture. Alignment of the deduced aa resulted in a lack of singled out amino acid substitutions in the partial genomic sequences of Brazilian isolates that would entirely contrast them to viruses propagated in MSB-1 cells, indicating that the combined VP1, VP2 and VP3 substitutions observed may not entirely account as sole determinants of CAV isolation and propagation in MDCC-MSB-1 cells.

Characterization and Phylogenetic Analysis of Brazilian Chicken Anaemia Virus

Chicken anaemia virus (CAV) was detected by a Nested-PCR assay in field samples from different regions of Brazil. The 539 bp amplified fragments of vp1 gene from 44 field samples were sequenced and 10 new nucleotide sequences of CAV were observed. These sequences were phylogenetically analysed by Mega2 using neighbour joining distance methods with 1000 bootstrap replications. Phylogenetic analysis did not show correlation between CAV pathology pattern and genetic groups. The 10 nucleotide sequences of the Brazilian samples were also analysed together with 30 sequences of CAV strains previously described from other countries. The genetic variability observed was not related to the geographical distribution. Amino acid substitutions were detected at 9 positions of the Brazilian sequences and two of them had not been observed before, (65)R replacing the Q residue and (98)F replacing Y residue.

Biological and molecular characterization of chicken anaemia virus isolates of Indian origin

In the present study, four chicken anaemia virus (CAV) isolates (CAV-A, -B, -E and -P) recovered from different geographical regions of India were characterized. CAV genome of 1,766 bp nucleotide region containing the complete coding region of VP2 and VP3 proteins, and partial coding region of VP1 protein were sequenced. The nucleotide and deduced amino acid sequence of the Indian CAV isolates were aligned and compared with CAV isolates of European, Asian, American and Australian origin. Phylogenetic analysis of the Indian CAV isolates were also carried out based on the nucleotide and deduced amino acid sequences. The results indicated that Indian isolates were genetically evolved from different parts of the world. Indian isolate, CAV-A was found closely related to European Cux-1 strain, CAV-B and -P were closely related to Bangladesh BD-3 strain and CAV-E was closely related to Australian 704 strain. The pathogenicity of the four CAV isolates was studied in day-old specific pathogen free (SPF) chicks. Day-old SPF chicks (n=50) were divided into five groups comprised of 10 chicks in each group. Group 1 was kept as control and groups 2-5 were infected with each CAV isolate separately. The chicks were infected at a dose rate of 1 ml cell culture fluid (10(4.5)TCID(50)/0.1 ml) per bird intramuscularly. The clinical signs, mortality and packed cell volume (PCV) and body weight gain were recorded on 5, 10 and 15 days post-infection. At 15th day, all the birds were sacrificed and various organs, viz., thymus, bone marrow, spleen, liver and bursa were examined for gross and microscopic changes. The pathogenicity study indicated that all the CAVs except CAV-B were able to produce clinical disease and immunosuppression in young chicks whereas the isolate CAV-B produced no clinical disease but only induced immunosuppression, which was revealed by microscopic examination of the lymphoid organs. The study showed valuable information on molecular epidemiological status of CAV isolates prevalent in India for the first time.

Development of a multiplex PCR for detection of avian adenovirus, avian reovirus, infectious bursal disease virus, and chicken anemia virus

A multiplex polymerase chain reaction (mPCR) was developed and optimized for the simultaneous detection and differentiation of avian reovirus (ARV), avian adenovirus group I (AAV-I), infectious bursal disease virus (IBDV), and chicken anemia virus (CAV). Four sets of specific oligonucleotide primers were used in this test for ARV, AAV-I, IBDV, and CAV. The mPCR DNA products were visualized by gel electrophoresis and consisted of fragments of 365 bp for IBDV, 421 bp for AAV-I, 532 bp for ARV, and 676 bp for CAV. The mPCR assay developed in this study was found to be sensitive and specific. Detection of PCR-amplified DNA products was 100 pg for both CAV and IBDV, and 10pg for both ARV and AAV-I and this mPCR did not amplify nucleic acids from the other avian pathogens tested. The mPCR demonstrated similar sensitivity in tests using experimental fecal cloacal swab specimens that were spiked with ARV, AAV-1, IBDV, and CAV, and taken from specific pathogen free (SPF) chickens. This mPCR detected and differentiated various combinations of RNA/DNA templates from ARV, AAV-I, CAV, and IBDV without reduction of amplification from feces.

A VP3/VP1 gene polymerase chain reaction assay for detection of chicken anemia virus in broiler samples

A PCR assay was designed for amplification of the highly conserved VP3 gene and a 5' region of the VP1 gene, for the diagnosis of CAV in organ samples of broiler flocks suspected of chicken infectious anemia. A comparison of the VP3/VP1 PCR with in vivo virus isolation revealed 100% agreement of the results, with 13 positive and 3 negative samples in both assays, indicating that the VP3/VP1 PCR is a specific diagnostic method. Tissues from additional 24 broiler chicken flocks, with CAV-like lesions and clinical history were then tested only by the VP3/VP1 PCR and a reference PCR with published primers for the VP1 gene. Nineteen samples resulted positive and one negative in both PCR, while another 4 samples were positive only in the VP3/VP1 PCR. These results indicate that the VP3/VP1 PCR is a sensitive, specific diagnostic test, suitable as an alternative to the expensive and time consuming in vivo virus isolation method, specially considering the difficult diagnosis of CAV strains not readily adaptable to MSB-1 cell culture.

Isolation and Preliminary Characterization of Chicken Anemia Virus from Chickens in Nigeria

Chicken anemia virus (CAV) was isolated for the first time from the Nigerian chicken population. The virus was recovered from necropsied birds from broiler and pullet flocks that suffered disease outbreaks tentatively diagnosed as infectious bursal disease. A sensitive polymerase chain reaction (PCR) assay detected CAV DNA in tissues of necropsied birds. Restriction endonuclease analysis performed with the 733-bp PCR product and the Cfo I enzyme indicated at least two different CAVs were circulating among the Nigerian chicken population. Four isolates were obtained from pooled liver and thymus tissues using the MDCC-MSB1 cell line. These isolates were found to be antigenically closely related to the Cuxhaven-1 (Cux-1) reference strain of CAV when reacted with four monoclonal antibodies prepared against the Cux-1 virus. One of the isolates (isolate A) induced thymus atrophy, bone marrow aplasia, and low hematocrit values when inoculated into 1-day-old specific-pathogen-free chickens. These findings not only demonstrate that CAV is present in Nigeria, but they also likely represent the first cell culture isolation of the virus in Africa.

Role of viral load in the pathogenesis of chicken anemia virus

The pathogenesis of strain 3711 of the chicken anemia virus (CAV), propagated in chickens, and two preparations of strain 3711 that had been adapted to grow to high titre in cells of the MDCC-MSB1 line were studied in chicken embryos and/or chickens. Highest viral loads in infected chickens, as measured by a microplate DNA-hybridization assay, were detected in the thymus, clotted blood and pancreas, and the lowest in the duodenum. The CAV DNA copy number in the organs of chicken embryos was significantly lower than in chickens. Route of infection was an important determinant of the course of disease in chickens, with clinical signs appearing earlier in birds infected by the intramuscular than those infected by the oral route; there was a direct relationship between viral load in particular organs and the extent of clinical signs. No reduction in the pathogenicity for chickens was noted for strain 3711 after 65 or 129 passages in the MDCC-MSB1 cell line.

Real-time quantitative PCR-based serum neutralization test for detection and titration of neutralizing antibodies to chicken anemia virus

Detection and titration of chicken anemia virus (CAV)-neutralizing antibodies has relied on tedious, time-consuming passaging of infected cells, or subjective recognition of cytopathic effect in individual cells, because CAV replicates in culture only in lymphoblastoid cell lines, and thus generates no plaques. This paper describes a rapid method, in which CAV genomes in infected cells are quantitated by qPCR 3-4 days postinfection (p.i.), without passaging cells. Three sera, weakly positive with a commercial CAV ELISA kit, from broiler chickens immunized with a commercial CAV vaccine, were used to develop the assay. Virus neutralization titers of these sera were determined using two different CAV-susceptible cell lines (MDCC-MSB1 and MDCC-CU147) by the conventional method of passaging cells infected with 10,000 TCID(50) CAV per well, and by qPCR-based methods using cells infected with 100 or 10,000 TCID(50) per well in 24-well or 96-well plates. The method was also adapted to conventional PCR. The positive sera exhibited virus neutralization activity at dilutions ranging from 1:10 to 1:320 by the various assays. Although virus neutralization titers differed somewhat depending on the assay conditions used, the relative order of the titers of the three positive sera was the same for all assays. The qPCR-based assays are as sensitive and more rapid for detection of neutralizing antibody than the conventional assay based on passaging infected cells, and more sensitive for detection of low-level CAV antibodies than a commercial blocking ELISA.

Detection of chicken anaemia virus DNA from formalin-fixed tissues by polymerase chain reaction

Chicken anaemia virus (CAV) DNA was detectable from various samples such as cell-free virus, infected MDCC-MSB1 cells, unfixed liver homogenates, formalin-fixed liver homogenate or formalin-fixed paraffin-embedded (FFPE) tissues from experimental or field infected chicks using PCR assay. The detection limit of the first PCR assay was 1 infected cell or 10(-1.5) TCID50 of cell-free virus (strain A2). The nested PCR assay increased the sensitivity 10- or 100-fold. CAV DNA was detectable in the other 14 Japanese strains isolated from 1976 to 1994 by the PCR assay. All the amplified products were digested with BglII, HindIII, PstI and SacI. These results suggest that the region amplified was highly conserved among the strains. The nested PCR assay was very sensitive. However, CAV DNA was detectable in most field samples using the first PCR assay. Therefore, the nested PCR assay may not always be necessary. In contrast, the nested PCR assay was necessary to detect CAV DNA in FFPE tissues or formalin-fixed material. Use of the PCR assay in CAV DNA detection from FFPE tissues may be most valuable in diagnosis of diseases caused by or associated with CAV, because it allows detection of both microscopic lesions and CAV DNA.

Gordon Memorial Lecture. Chicken anaemia virus--a glimpse of the future?

This paper uses background information about chicken anaemia virus as a guide to how the study and control of virus diseases of poultry may develop in the future. It is predicted that "new' viruses will be discovered in poultry, many of which will be difficult to grow in vitro and whose pathogenicity may appear uncertain. When new diseases/syndromes arise in the future, it should be a priority activity to define their pathology. The limitations of currently available virus diagnostic methods are highlighted. The possibility of vaccinating against economically important subclinical disease is discussed, as is the use of recently developed technologies in differentiating virus strains and in developing new vaccines.

A hypervariable region in VP1 of chicken infectious anemia virus mediates rate of spread and cell tropism in tissue culture

Chicken infectious anemia virus (CIAV) is a unique infectious agent with an amino acid composition that has been found to be remarkably conserved even in isolates from different parts of the world. We have characterized field isolates of CIAV which vary significantly in terms of their abilities to replicate in culture, demonstrating a biological difference between isolates. Two sublines of MDCC-MSB1 cells that differ in their abilities to support CIAV were identified. In the MSB1(S) subline the CIA-1 isolate of CIAV was found to be less cytopathogenic than the prototype Cux-1(C) isolate; the MSB1(L) subline, which supports Cux-1(C) replication, was found to be nonpermissive for CIA-1. Alignments of the VP1 sequences of previously examined isolates with those of the field isolates CIA-1 and L-028 and the culture-adapted ConnB isolate revealed a previously unreported hypervariable region spanning amino acid positions 139 to 151. Chimeras of Cux-1(C) and CIA-1 were constructed to examine the potential for this region to affect cytopathogenicity. Transfer of a 316-bp region of Cux-1(C) open reading frame 1 into CIA-1 produced a virus with a cytopathogenic profile typical of Cux-1(C), indicating that one or both of the amino acid differences at positions 139 and 144 affect the rate of replication or the spread of infection. Transfection experiments with additional chimeras indicated that the inability of CIA-1 to replicate in MSB1(L) cells is mediated by a larger region of the genome which contains the hypervariable region in addition to upstream amino acid differences. Analysis of chimeras excluding the entire region of open reading frame 1 suggested the presence of a secondary mediator in the progression of infection in culture that was localized to a region containing a single nucleotide difference which results in amino acid differences in both VP2 (V-153) and the nuclear localization signal of VP3 (C-118). Immunofluorescence assays indicated an increased cytoplasmic distribution of VP3 and a general lack of VP3-associated apoptotic bodies in infections of CIA-1 and chimeras containing V-153 or C-118, as opposed to a primarily nuclear distribution and association with well-formed apoptotic bodies in Cux-1(C)-infected cells.

Investigation of the transfection capability of cloned tandemly-repeated chicken anaemia virus DNA fragments

Chicken anaemia virus (CAV) is an icosahedral virus, 25 nm in diameter, which, on the basis of its circular single-stranded DNA genome, has recently been classified in the family, Circoviridae. We have investigated whether infectious, monomeric CAV DNA from recombinant plasmids containing tandemly-repeated CAV replicative form (RF) DNAs, following transfection, was generated by homologous recombination or a replicational release mechanism involving rolling circle replication (RCR) of DNA. Experiments designed to locate the virus strand origin of RCR and/or sites of recombination were performed by sequence analyses of hybrid viruses generated after transfection with cloned tandemly-repeated RFs specified by the sequence-distinct Cux-1 and 26P4 isolates. Positive transfection results obtained from 2 recombinant plasmid constructs were shown to have resulted from homologous recombination occurring at different sites within the RF sequence. Three of 5 hybrid viruses analysed were "circularised" within the same 105 bp sequence, that contains four 19bp repeats and with which promoter/enhancer activity has been associated. This region may represent a novel origin or recombination hot-spot within the CAV genome. A distinctive cruciform-loop structure within the non-coding region was shown to contain an S1 nuclease-sensitive site, detected in CAV RF and in recombinant plasmids containing RF inserts.

A single chicken anemia virus protein induces apoptosis

Chicken anemia virus (CAV) causes cytopathogenic effects in chicken thymocytes and cultured transformed mononuclear cells via apoptosis. Early after infection of chicken mononuclear cells, the CAV-encoded protein VP3 exhibits a finely granular distribution within the nucleus. At a later stage after infection, VP3 forms aggregates. At this point, the cell becomes apoptotic and the cellular DNA is fragmented and condensed. By immunogold electron microscopy VP3 was shown to be associated with apoptotic structures. In vitro, expression of VP3 induced apoptosis in chicken lymphoblastoid T cells and myeloid cells, which are susceptible to CAV infection, but not in chicken embryo fibroblasts, which are not susceptible to CAV. Expression of a C-terminally truncated VP3 induced much less pronounced apoptosis in the chicken lymphoblastoid T cells.

Application of the polymerase chain reaction (PCR) in veterinary diagnostic virology

The polymerase chain reaction has become an important diagnostic tool for the veterinary virologist. Conventional methods for detecting viral diseases can be laborious or ineffective. In many cases PCR can provide a rapid and accurate test. In this article we explain the basic principles of PCR and supply a reference list of its uses in diagnostic veterinary virology.