The immunogenicity of P97 adhesin repeat region R1 (P97R1) of Mycoplasma hyopneumoniae, an important pathogenesis-associated region of P97, was evaluated in mice as a mucosal vaccine. Mice were immunized orally with attenuated Salmonella typhimurium aroA strain CS332 harbouring a eukaryotic or prokaryotic expression vector encoding P97R1. Local and systemic immune responses were analysed by ELISA on mouse sera, lung washes and splenocyte supernatants following splenocyte stimulation with specific antigens in vitro. Although no P97R1-specific antibody responses were detected in serum and lung washes, significant gamma interferon was produced by P97R1-stimulated splenocytes from mice immunized orally with S. typhimurium aroA harbouring either expression system, indicating induction of a cell-mediated immune response. These results suggested that live bacterial vectors carrying DNA vaccines or expressing heterologous antigens preferentially induce a Th1 response. Surprisingly, however, mice immunized with the vaccine carrier S. typhimurium aroA CS332 induced serum IgG, but not mucosal IgA, against P97R1 or S. typhimurium aroA CS332 whole-cell lysate, emphasizing the importance of assessing the suitability of attenuated S. typhimurium antigen-carrier delivery vectors in the mouse model prior to their evaluation as potential vaccines in the target species, which in this instance was pigs. INTRODUCTIONPorcine enzootic pneumonia (PEP) caused by Mycoplasma hyopneumoniae is a chronic, non-fatal respiratory disease. It affects pigs of all ages, resulting in slow growth and reduced feed efficiency, and causes significant economical losses in the pig industry worldwide (Sheldrake et al., 1991;Thacker et al., 1998). PEP is often followed by secondary infections by Porcine reproductive and respiratory syndrome virus and opportunistic bacterial pathogens (Calsamiglia et al., 1999;Sheldrake et al., 1991;Thacker et al., 1998Thacker et al., , 1999. As current market vaccines (bacterins prepared by chemical inactivation of whole-cell M. hyopneumoniae) do not protect pigs completely from establishment of M. hyopneumoniae infection and/or secondary infection (Kristensen et al., 1981;Maes et al., 1999;Murphy et al., 1993; Pallares et al., 2000;Thacker et al., 1998), development of an improved vaccine is desirable. P97 adhesin has probably been the most-studied and bestdefined potential protective antigen of M. hyopneumoniae since it was identified as an important adhesin responsible for the adherence of M. hyopneumoniae to respiratory ciliated epithelial cells in swine (Zhang et al., 1995). Furthermore, a repeat region of P97 called R1 (P97R1) has been identified as containing both cilium-and antibodybinding sites (Hsu & Minion, 1998;Hsu et al., 1997) and has been reported to function independently from other P97 regions (Minion et al., 2000). P97R1 has been shown to induce significant P97R1-specific serum IgG titres in both mice and pigs (Chen et al., 2001), indicating that it is immunogenic. However, the immunogenicity of P97R1 has...
A comprehensive genetic analysis of 60 Mycoplasma sp. bovine group 7 isolates from different geographic origins and epidemiological settings is presented. Twenty-four isolates were recovered from the joints of calves during sporadic episodes of polyarthritis in geographically distinct regions of Queensland and New South Wales, Australia, including two clones of the type strain PG5O. A further three Australian isolates were also recovered from the tympanic bulla, retropharyngeal lymph node and the lung and another three isolates had unconfirmed histories. Six isolates originated from Germany, Portugal, Nigeria, and France. Twenty-four epidemiologically related isolates of Mycoplasma sp. bovine group 7 were recovered from multiple tissue sites and body fluids of infected calves with polyarthritis, mastitic milk, and from the stomach contents, lung and liver from aborted foetuses in three large, centrally managed dairy herds in New South Wales, Australia. Restriction endonuclease analysis (REA) of genomic DNA differentiated 29 Cfol profiles among these 60 isolates and grouped all 24 epidemiologically related isolates in a defined pattern showing a clonal origin. Three isolates of this clonal cluster were recovered from mastitic milk and the synovial exudate of clinically-affected calves and appeared sporadically for periods up to 18 months after the initial outbreak of polyarthritis indicating a persistent, close association of the organism with cattle in these herds. The Cfol profile representative of the clonal cluster was distinguishable from profiles of isolates recovered from multiple, unrelated cases of polyarthritis in Queensland and New South Wales and from other countries. All 24 isolates from the clonal cluster possessed a plasmid (pBG7AU) with a molecular size of 1022 bp. DNA sequence analysis of pBG7AU identified two open reading frames sharing 81 and 99% DNA sequence similarity with hypothetical replication control proteins A and B respectively, previously described in plasmid pADB201 isolated from M. mycoides subspecies mycoides. Other isolates of bovine group 7, epidemiologically unrelated to the clonal cluster, including two clones of the type strain PG5O, possessed a similar-sized plasmid. These data confirm that Mycoplasma sp. bovine group 7 is capable of migrating to, and multiplying within, different tissue sites within a single animal and among different animals within a herd.
Abstract. In 2003, a steer carcass was condemned at a Central Queensland abattoir because of metastatic tumors. In addition, a granulomatous lesion was found in the mediastinal lymph node. Histological examination showed this to be a pyogranuloma, typically associated with Rhodococcus or the Nocardia/Streptomyces group. However, in this case, the only etiological agent was an acid-fast bacillus, which would normally be associated with a more fibrous lesion. A number of nucleic acid-based techniques were used, and the isolate was identified as Mycobacterium asiaticum. This organism is a rarely encountered opportunistic pathogen of humans, associated with subtropical climates. This is the first report of this organism causing infection in cattle. The similarities between this case and cases of human disease are discussed.
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