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. Chicken anemia virus (CAV) transiently causes severe anemia due to destruction of erythroblastoid cells and immunodeficiency due to depletion of cortical thymocytes in young chickens (10, 38). Jeurissen et al. (11) have provided evidence that the observed depletion of the thymocytes occurs via CAV-induced apoptosis. Apoptosis is considered to be a physiological process of cell depletion that is part of the homeostatic regulation of normal tissues (5). CAV in addition to several other viruses, such as human immunodeficiency virus type 1 (2) and parvovirus B19 (19), seems to use apoptosis to exert its cytopathogenic effect. CAV is a small virus with a diameter of about 23 nm and contains a circular single-stranded DNA of 2.3 kb (27). CAV multiplies via a circular double-stranded DNA replicative intermediate, which was recently cloned (18, 21). The cloned CAV genome was proven to be representative for CAV isolates collected worldwide (23, 29). A polycistronic polyadenylated mRNA (22) which comprises three overlapping open reading frames encoding proteins VP1 (51.6 kDa), VP2 (24.0 kDa), and VP3 (13.6 kDa) is transcribed from the CAV

Circoviruses are small, nonenveloped icosahedral animal viruses characterized by circular singlestranded DNA genomes. Their genomes are the smallest possessed by animal viruses. Infections with circoviruses, which can lead to economically important diseases, frequently result in virus-induced damage to lymphoid tissue and immunosuppression. Within the family Circoviridae, different genera are distinguished by differences in genomic organization. Thus, Chicken anemia virus is in the genus Gyrovirus, while porcine circoviruses and Beak and feather disease virus belong to the genus Circovirus. Little is known about the structures of circoviruses. Accordingly, we investigated the structures of these three viruses with a view to determining whether they are related. Three-dimensional maps computed from electron micrographs showed that all three viruses have a T‫1؍‬ organization with capsids formed from 60 subunits. Porcine circovirus type 2 and beak and feather disease virus show similar capsid structures with flat pentameric morphological units, whereas chicken anemia virus has stikingly different protruding pentagonal trumpet-shaped units. It thus appears that the structures of viruses in the same genus are related but that those of viruses in different genera are unrelated.

No common antigenic determinants and no DNA sequence homologies were detected when three animal viruses, chicken anaemia agent (CAA), porcine circovirus (PCV), and psittacine beak and feather disease virus (PBFDV), all of which possess circular single-stranded DNA genomes, were compared. Negative contrast electron microscopy showed that PCV and PBFDV particles were 30% smaller than CAA particles and lacked the surface structure of CAA.

SUMMARYDuring investigations into an outbreak of respiratory distress in broilers chicks, a small round virus was isolated following inoculation into chicken embryos. The isolate, designated 612, was identified as an enterovirus-like virus on the basis of its size and morphology, resistance to chloroform and to treatment at pH 3.0, and intracytoplasmic replication in cell culture. The virus produced a partial cytopathic effect following inoculation into chick embryo kidney cell cultures and viral antigens could be detected by immunostaining. The preferred culture method for 612 virus was by inoculation onto the CAM of chick embryos. Cross-immunofluorescence indicated that the virus is not antigenically related to five previously identified chicken enterovirus/enterovirus-like virus serogroups. Following experimental inoculation of 1-day-old male broilers a number of which had maternal antibody to 612, growth retardation ranging from 9.6 to 20.4% was detected. Serological studies demonstrated antibody to 612 virus was widespread in commercial chicken flocks in N. Ireland.

Summary Aims:  The aim of this work was to investigate the germination and inactivation of spores of Bacillus species in buffer and milk subjected to high pressure (HP) and nisin. Methods and Results:  Spores of Bacillus subtilis and Bacillus cereus suspended in milk or buffer were treated at 100 or 500 MPa at 40°C with or without 500 IU ml−1 of nisin. Treatment at 500 MPa resulted in high levels of germination (4 log units) of B. subtilis spores in both milk and buffer; this increased to >6 logs by applying a second cycle of pressure. Viability of B. subtilis spores in milk and buffer was reduced by 2·5 logs by cycled HP, while the addition of nisin (500 IU ml−1) prior to HP treatment resulted in log reductions of 5·7 and 5·9 in phosphate buffered saline and milk, respectively. Physical damage of spores of B. subtilis following HP was apparent using scanning electron microscopy. Treating four strains of B. cereus at 500 MPa for 5 min twice at 40°C in the presence of 500 IU ml−1 nisin proved less effective at inactivating the spores of these isolates compared with B. subtilis and some strain‐to‐strain variability was observed. Conclusions:  Although high levels of germination of Bacillus spores could be achieved by combining HP and nisin, complete inactivation was not achieved using the aforementioned treatments. Significance and Impact of the Study:  Combinations of HP treatment and nisin may be an appealing alternative to heat pasteurization of milk.