Brian Adair

Isolation of Porcine Circovirus-like Viruses from Pigs with a Wasting Disease in the USA and Europe:

Samples of lung, liver, kidney, pancreas, spleen, and lymph node from pigs with postweaning multisystemic wasting syndrome from California (USA) and samples of mesenteric lymph nodes from similarly diseased pigs from Brittany (France) were examined by light microscopy, in situ hybridization (ISH), and/or virus isolation. Whole genomic probes for porcine circovirus (PCV) and chicken anemia virus (CAV) were used for ISH. Tissue homogenate supernatants were inoculated onto PK/15 cells for virus isolation, and the presence of viral antigen and viral particles was verified by indirect immunofluorescence, ISH, and electron microscopy. Histologic examination of lung from pigs from California revealed interstitial pneumonia, alveolar epithelial hyperplasia, and basophilic nuclear and cytoplasmic inclusions in mononuclear cell infiltrates and various pulmonary epithelial cells. Granulomatous lymphadenitis with syncytial cells typified the lesions seen in the pigs from France. PCV-like nucleic acid was detected by ISH in lung, pancreas, lymph node, kidney, and liver in pigs from California. Positive signal was also obtained in lymph node sections from pigs from France. Probes for CAV were consistently negative. PK/15 cell cultures inoculated with lung preparations from diseased California pigs and mesenteric lymph node preparations from pigs from France had positive fluorescence by indirect staining for PCV using pooled polyclonal pig sera and hyperimmune rabbit serum and had variable staining with a panel of 7 monoclonal antibodies specific for cell culture contaminant PCV. PCV-like nucleic acid was also detected by ISH in cell cultures. Cytopathic effect was not observed Electron microscopic examination of inoculated cell cultures revealed 17-nm viral particles morphologically consistent with PCV No other virus particles were observed. Although genomic analysis for the definitive identification of these viral isolates remains to be done, the evidence provided strongly suggests that these tissue isolates are closely related to, although antigenically distinct from, the original PCV cell culture contaminant.

Reproduction of postweaning multisystemic wasting syndrome in pigs experimentally inoculated with a Swedish porcine circovirus 2 isolate

In recent years, porcine circovirus type 2 (PCV2)—associated postweaning multisystemic wasting syndrome (PMWS) has been reported worldwide. However, to date, PMWS has not been reported in Sweden despite the demonstration of serum antibodies to a PCV2-like virus in Swedish pigs. This communication reports the experimental reproduction of clinical PMWS after inoculation of colostrum-deprived (CD) pigs, derived from a Northern Ireland herd, with an isolate of PCV2 virus recovered from a clinically normal Swedish pig that was necropsied in 1993. The clinical disease and histological lesions observed in CD pigs inoculated with this virus were indistinguishable from those observed in previous studies on CD pigs inoculated with a PCV2 virus isolate recovered from pigs with PMWS. These results highlight the disease potential of PCV2 isolated from regions apparently free of PMWS and suggest that the status of the host and its environment is an important factor in the development of clinical PMWS.

Immunogenicity of bovine parainfluenza type 3 virus proteins encapsulated in nanoparticle vaccines, following intranasal administration to mice

Stimulation of long lasting, protective immunity to respiratory viruses is often difficult to achieve with conventional respiratory vaccines. Polymeric nanoparticles, incorporating viral proteins have been shown to offer sustained release of antigen, with consequent prolongued stimulation of the respiratory immune system. In this paper the efficacy of two nanoparticle vaccines (poly-lactide-co-glycolide, PLGA; polymethylmethacrylate, PMMA), incorporating proteins of bovine parainfluenza type 3 virus (BPI-3) was investigated. As a preliminary to experiments in calves, it was considered essential to demonstrate immunogenicity of the experimental vaccine in mice. Mice immunised with PLGA nanoparticles, containing BPI-3 proteins, developed higher levels of virus-specific antibody than mice immunised with the PMMA vaccine or with soluble viral proteins alone. Immunoblotting using serum from the vaccinated mice, demonstrated strong reactions against the major BPI-3 proteins.

Molecular Basis of the Attenuation Exhibited by Molecularly Cloned Highly Passaged Chicken Anemia Virus Isolates

ABSTRACT Chimeric virus experiments indicated that the pathogenicity and monoclonal antibody reactivity differences between two molecularly cloned, highly passaged chicken anemia virus isolates could be attributed to the VP1 amino acid change at residue 89. The introduction of this change into a pathogenic cloned low-passage isolate was not sufficient to cause attenuation.

Distribution of cytopathic and noncytopathic bovine viral diarrhea virus antigens in tissues of calves following acute experimental infection

The distribution of cytopathic and noncytopathic biotypes of bovine viral diarrhea virus (BVDV) in the tissues of colostrum-fed and colostrum-deprived calves was investigated. Colostrum-fed (group A) and colostrum-deprived (group B) calves were experimentally infected with the BVDV isolate 80/1, which contains both BVDV biotypes. Colostrum-deprived calves were also experimentally infected with a noncytopathic BVDV (group C) or with a cytopathic BVDV (group D) cloned from the 80/1 isolate. All calves were sequentially euthanized, and a wide range of tissue samples were processed for immunofluorescent and virus isolation studies. In group A, consistent immunofluorescent staining for BVDV was detected in vascular smooth muscle of numerous blood vessels in the tissues examined, mainly at 11 and 13 days postinoculation. A predominance of samples containing cytopathic BVDV was observed in the calves of this group, following virus isolation studies. Both cytopathic and noncytopathic BVDV were detected/recovered from a larger range of specimens in the calves in group B than from the calves in group A. In the calves in all the experimental groups, large amounts of BVDV antigen were detected mainly in tissue samples from the lymphoid and gastrointestinal systems, whereas only minimal amounts of BVDV were detected in the respiratory tract. Abundant noncytopathic BVDV antigen was also detected in pituitary gland and in Langerhans islets in pancreases of colostrum-deprived calves infected with the cloned noncytopathic BVDV. Noncytopathic BVDV was isolated from a wider range of tissues from calves in group C than in the colostrum-deprived calves infected with both BVDV biotypes. A cytopathic BVDV was isolated/detected in retropharyngeal, mesenteric, and abomasal lymph nodes and in thymus of 2 calves in group C. Cytopathic BVDV was detected/isolated mainly from mesenteric lymph nodes and Peyers patches of the calves in group D.

Antigen-specific IgA and IgG responses in calves inoculated intranasally with ovalbumin encapsulated in poly(DL-lactide-co-glycolide) microspheres

The immunogenicity of proteins encapsulated in poly(DL-lactide-co-glycolide) (PLG) microspheres has not been investigated to any extent in large animal models. In this study, IgG and IgA responses to ovalbumin (OVA), encapsulated in microspheres was investigated following intranasal inoculation into calves. Scanning electron microscopy and flow cytometric analysis demonstrated a uniform microsphere population with a diameter of < 2.5 micrometers. Ovalbumin was released steadily from particles stored in PBS almost in a linear fashion, and after 4 weeks many particles showed cracks and fissures in their surface structure. Following intranasal inoculation of calves with different doses of encapsulated antigen, mean levels of ovalbumin-specific IgA were observed to increase steadily but significant differences in IgA levels (from the pre-inoculation level) were only observed following a second intranasal inoculation. With 0.5 and 1.0mg doses of antigen, ovalbumin-specific IgG was also detected in serum. Ovalbumin-specific IgA persisted in nasal secretions for a considerable period of time and were still detectable in four out of seven animals, 6 months after inoculation.

Immunogenetic responses in calves to intranasal delivery of bovine respiratory syncytial virus (BRSV) epitopes encapsulated in poly (DL-lactide-co-glycolide) microparticles

Bovine respiratory syncytial virus (BRSV) is the principal aetiological agent of the bovine respiratory disease complex. A BRSV subunit vaccine candidate consisting of two synthetic peptides representing putative protective epitopes on BRSV surface glycoproteins in soluble form or encapsulated in poly(lactide-co-glycolide) (PLG) microparticles were prepared. Calves (10 weeks old) with diminishing levels of BRSV-specific maternal antibody were intranasally administered a single dose of the different peptide formulations. Peptide-specific local immune responses (nasal secretion IgA), but not systemic humoral (serum IgG) or cellular responses (serum IFN-γ), were generated by all forms of peptide. There was a significant reduction in occurrence of respiratory disease in the animals inoculated with all peptide formulations compared to animals given PBS alone. Furthermore no adverse effects were observed in any of the animals post vaccination. These results suggest that intranasal immunisation with the peptide subunit vaccine does induce an as yet unidentified protective immune response.

Local and systemic immune responses in mice to intranasal delivery of peptides representing bovine respiratory syncytial virus epitopes encapsulated in poly (dl-lactide-co-glycolide) microparticles

The potential of a microparticulate vaccine delivery system in eliciting a specific mucosal antibody response in the respiratory tract of mice was evaluated. Two vaccine candidate peptides representing epitopes from the G attachment and F fusion antigens from bovine respiratory syncytial virus (BRSV) were encapsulated into poly(DL-lactide co-glycolide) biodegradable microparticles. The encapsulation process did not denature the entrapped peptides as verified by detection of peptide-specific antibodies in mucosal secretions by ELISA using peptide as antigen. Following intranasal immunisation, the encapsulated peptides induced stronger upper and lower respiratory tract specific-IgA responses, respectively, than the soluble peptide forms. Moreover, a strong peptide-specific cell-mediated immune response was measured in splenocytes in vitro from the mice inoculated with the encapsulated peptides compared to their soluble form alone indicating that migration of primed T cells had taken place from the site of mucosal stimulation in the upper respiratory tract to the spleen. These results act as a foundation for vaccine efficacy studies in large animal BRSV challenge models.