In situ hybridization for detection of chicken anaemia virus in peripheral blood smears

Pathological and virological analysis of concurrent disease of chicken anemia virus infection and infectious bronchitis in Japanese native chicks

A concurrent infection of chicken anemia virus (CAV) and infectious bronchitis virus (IBV) was detected in Japanese native chicks in 2017, in which a high mortality rate (97.7%) was recorded in a small flock of 130 chicks exhibiting poor growth. Histological examination revealed that the affected chicks exhibited two different pathological entities: one was severe hematopoietic and lymphocytic depletion with abnormally large cells containing intranuclear inclusion bodies of CAV, whereas the other was renal tubular necrosis due to IBV infection. Immunohistochemistry detected CAV antigens in the bone marrow, liver, and spleen as well as IBV antigens in the kidneys, trachea, and air sacs. CAV was isolated from the liver sample of the chicks, and the isolated strain was designated as CAV/Japan/HS1/17. A phylogenetic analysis of the CAV VP1 gene revealed that CAV/Japan/HS1/17 is genetically similar to Chinese strains collected from 2014 to 2016. An experimental infection was performed using CAV/Japan/HS1/17 and specific-pathogen-free chicks to determine the pathogenicity of CAV/Japan/HS1/17. The isolate caused 100% anemia and 70% mortality to chicks inoculated at one day old, 80% of chicks inoculated at seven days old also developed anemia, and 10% died from CAV infection. These results suggest that the unusually high mortality in Japanese native chicks can be attributed to dual infection with both CAV and IBV. The results of the experimental infection suggest that CAV/Japan/HS1/17 has a pathogenic potential to specific-pathogen-free chicks and a relatively higher pathogenicity than previous Japanese CAV strains.

Detection of two different mRNAs in a single section by dual in situ hybridization: a comparison between colorimetric and fluorescent detection

We have compared the performance of two methods designed to simultaneously detect two different mRNAs within a single brain section by dual ISH. Specific mRNA riboprobes labeled with biotin and digoxigenin were simultaneously hybridized and visualized using either brightfield or fluorescence microscopy. For brightfield visualization, the biotin-labeled riboprobe was detected with a peroxidase chromogen, whereas, an alkaline phosphatase substrate was used for the detection of the digoxigenin-labeled riboprobe. Dual fluorescent ISH involved the detection of the biotin-labeled riboprobe with an Alexa((R))488-conjugated streptavidin followed by the visualization of the digoxigenin-labeled riboprobe with the red fluorescent substrate HNPP. The dual ISH protocols presented here offer sensitive methods to detect the expression of two mRNAs of interest, with both colorimetric and fluorescent ISH each having its strengths and limitations. For example, dual colorimetric ISH has proven to be particularly useful to study the distribution of two mRNAs in different brain nuclei, whereas, dual fluorescent ISH has provided better results when studying the co-localization of two different mRNAs in single neurons. The comprehensive step-by-step procedure is presented, together with a troubleshooting section in which the advantages and limitations of these procedures are reviewed in depth. Moreover, alternative protocols for dual ISH were also compared to those presented here.

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.

Competitive DNA hybridization in microtitre plates for chicken anaemia virus

Unlabelled chicken anaemia virus (CAV) DNA probe, produced by PCR, was immobilized onto nitrocellulose discs that then were fitted into microtitre plate wells in order to develop a competitive, non-radioactive hybridization test for detection of CAV. The discs were hybridized with either DNA extracts of buffy coats or dilutions of CAV DNA (for standard curves), followed by hybridization with biotin-labelled CAV DNA probe in excess of the immobilized, capture probe. Thus, CAV from sample DNA extracts and standard DNA preparations competed with the biotin-labelled CAV DNA probe for the immobilized, capture probe, decreasing subsequent colour development by an avidin-biotin-alkaline phosphatase detection system. Standard curves were log linear from 5-100 ng viral DNA with r(2)> or =0.91. Tests were considered positive at 2 SD less than mean absorbence of samples from uninfected chickens, and ranged from 52 to 108 microm viral DNA or 2 to 4.2x10(10)virions microg(-1)buffy coat DNA. Blood samples from chickens infected and not infected with CAV at one day of age were tested for evidence of infection until 28 days of age by viral isolation, competitive hybridization in microtitre plates, dot-blots, enzyme-linked immunosorbent assay (ELISA), and in situ hybridization on blood smears. None of the tests was positive for uninfected chickens. Viral isolation from buffy coats, though expensive and lengthy, was the most sensitive method. It detected virus in buffy coat from each infected chicken, while competitive hybridization detected 72% of infected chickens, in situ hybridization 69%, dot-blots 67%, and ELISA 36%. Sensitivity of competitive hybridization was 0.78, and its specificity was 1.00. Three chickens must be sampled from an infected flock for a 90% chance of detecting a positive chicken at the 0.025 one-tailed level of significance, assuming 100% prevalence.

Persistent infection with chicken anaemia virus and some effects of highly virulent infectious bursal disease virus infection on its persistency

Chicken anaemia virus (CAV) infectivity and the effect of highly virulent infectious bursal disease virus (hv IBDV) infection on CAV's infectivity were examined in chickens inoculated with CAV or inoculated dually with CAV and hv IBDV. Five chickens inoculated dually with hv IBDV at 35 days old and then with CAV at 40 days old exhibited no clinical signs of disease, but showed atrophic bursae of Fabricius when necropsied 4 weeks later. Upon examining the chickens at 7 days postinoculation (dpi) with CAV, it was found that hv IBDV infection had inhibited production of virus neutralising (VN) antibody to CAV, and that it was possible to recover CAV from plasma of these chickens. Although VN antibody to CAV appeared after 14 dpi, CAV was recovered from blood cells (BC s) at high titres ranging from 10(2.5)to 10(5.5)TCID(50)/0.1 ml, 7 to 28 dpi in IBDV -induced immunosuppressed chickens. In addition, CAV was sporadically recovered, using rectal swabs, from the dually inoculated chickens at low titers, ranging from 10(1.0)to 10(2. 0)TCID(50)/0.1 ml). In contrast, although CAV was recovered from BC s in most of the chickens inoculated with CAV alone, the titers were lower (10(1.0)to 10(2.5)TCID(50)/0.1 ml). No CAV was detected from the rectal swabs of these chickens. The results of virus recovery were confirmed by polymerase chain reaction. This study first examined the persistency of CAV in BC s and the effective enhancement of primary CAV infection as a result of immunosuppression caused by hv IBDV infection.