PubMed Health⌕ Search

Biomedical subjects

P M Bartley

Publications and source records attributed to P M Bartley.

5 recordsLinked to original sources
PubMed2006

Long-term passage of tachyzoites in tissue culture can attenuate virulence of Neospora caninum in vivo.

To determine whether prolonged in vitro passage would result in attenuation of virulence in vivo, Neospora caninum tachyzoites were passaged for different lengths of time in vitro and compared for their ability to cause disease in mice. Groups of Balb/c mice were inoculated intraperitoneally with 5 x 10(6) or 1 x 10(7) of low-passage or high-passage N. caninum tachyzoites. The mice were monitored for changes in their demeanour and body weight, and were culled when severe clinical symptoms of murine neosporosis were observed. Mice inoculated with the high-passage parasites survived longer (P<0.05), and showed fewer clinical symptoms of murine neosporosis, compared to the mice receiving the low-passage parasites. The parasite was detected in the brains of inoculated mice using immunohistochemistry and ITS1 PCR. Tissue cysts containing parasites were seen in mice inoculated with both low-passage and high-passage parasites. When the in vitro growth rates of the parasites were compared, the high-passage parasites initially multiplied more rapidly (P<0.001) than the low-passage parasites, suggesting that the high-passage parasites had become more adapted to tissue culture. These results would suggest that it is possible to attenuate the virulence of N. caninum tachyzoites in mice through prolonged in vitro passage.

Animals↗
PubMedDate not supplied

Maternal and fetal immune responses of cattle inoculated with Neospora caninum at mid-gestation.

The humoral and cell-mediated immune responses of pregnant cattle and their fetuses were examined at intervals after infection with Neospora caninum tachyzoites at mid-gestation (day 140). All cattle seroconverted and interferon gamma was detected in supernatants of peripheral blood mononuclear cells stimulated with specific antigen. At day 14 post-inoculation (pi), specific cell proliferation responses were detected in the lymph node draining the site of inoculation and in the uterine lymph node. The peak response was recorded in the majority of maternal lymph nodes by day 28 pi and cells from the maternal retropharyngeal lymph node, which in part drains the central nervous system, showed no specific activity to N. caninum until day 42 pi. This changing pattern of immune responsiveness may reflect parasite invasion and development within different host tissues. Fetal lymph node cells showed mitogen responsiveness from day 14 pi (day 154 of gestation) and also showed N. caninum-specific cell proliferation and interferon-gamma responses by day 28 pi (day 168 of gestation). At day 42 pi, specific cell-mediated immune responses were not apparent; however, N. caninum-specific fetal IgG and IgM antibodies were detected.

Animals↗
PubMedDate not supplied

Characterization of the immune response in the placenta of cattle experimentally infected with Neospora caninum in early gestation.

A serial examination of three groups of cattle infected intravenously (iv) (Group 1, n=8) or subcutaneously (sc) (Group 2, n=8) with live Neospora caninum tachyzoites or with VERO cells (Group 3, n=8) at 70 days' gestation was carried out and the nature of the inflammatory responses in the placenta and the presence of parasite antigen were analysed. Immune cells expressing CD3, CD4, CD8, gamma delta (gammadelta) T-cell receptors (TCR), CD79alpha cytoplasmic (cy) (B cells) and NKp46 [natural killer (NK) cells] antigens were identified immunohistochemically and cells expressing mRNA for interferon-gamma (IFN-gamma) were labelled by in-situ hybridization. Intravenous inoculation caused mortality in all fetuses from 28 days post-inoculation (dpi) onwards. Subcutaneous inoculation caused mortality in 50% of the animals by 28dpi. Pathological changes in the placenta consisted of necrosis of fetal placental villi, necrosis and inflammation in adjacent areas of the maternal septum and inflammation at the base of the maternal caruncle. The inflammatory infiltrate consisted mainly of CD3(+) lymphocytes, dominated by CD4(+) and gammadelta TCR(+) cells, with CD8(+) cells present to a lesser extent. The results from the control group indicated fewer NK cells than those occurring in the placenta of human beings or mice. Infiltration of CD4(+) cells and NKp46(+) cells was observed in the caruncular base and septa 14 days after infection, whereas infiltration of gammadelta TCR(+) cells was observed from 28 dpi onwards. To our knowledge this is the first report on the presence and distribution of NK cells in the bovine placenta. Maternal inflammatory cells expressing mRNA for IFN-gamma were identified in animals inoculated with parasites iv or sc at 14 and 28 dpi, respectively. In the sc-inoculated dams with live fetuses at 28, 42 and 56dpi, there was no evidence of parasite antigen, infiltration of immune cells or production of IFN-gamma, suggesting that the parasite had not reached the placenta. The exact cause of fetal death was not established. Tissue destruction by the parasite may have occurred; in addition, there may have been a T helper 1 (Th-1) immune response to the neospora infection at the materno-fetal interface, resulting in infiltrations of CD4T cells, gammadelta T cells and NK cells and the subsequent production of IFN-gamma. It is possible that a pro-inflammatory Th-1 response early in gestation protects the dam by eliminating the parasite; however, it may lead to destruction of the placental tissues themselves and thus be incompatible with fetal survival.

Animals↗
PubMedDate not supplied

The pathogenesis of neosporosis in pregnant cattle: inoculation at mid-gestation.

To investigate the pathogenesis of bovine neosporosis, 14 pregnant cattle were each inoculated subcutaneously with either 10(7) or 5 x 10(8) Neospora caninum (strain NC1) tachyzoites at 140 days' gestation. Serial necropsies were then carried out over an 8-week period. In the placenta, Neospora DNA and histopathological changes were observed in samples taken 14 days post-inoculation (dpi), with focal necrosis of maternal caruncular septa and fetal placental villi, serum leakage, and a maternal and fetal inflammatory response. At subsequent samplings, pathological changes in the placenta showed signs of resolution. No parasitaemia was detected in the dams in the two weeks following inoculation. In the fetus, Neospora DNA was detected at 14 dpi, and histopathological changes in the fetal central nervous system at 28 and 42 dpi consisted of small foci of necrosis and inflammation. Resolution of placental lesions during the experiment indicated that the disease was being controlled, and fetal infection, although established, did not appear to be progressing to a fatal outcome. The two doses of tachyzoites produced similar results, but the higher dose elicited earlier and more extensive lesions in the placenta and fetus. Control animals remained negative for all parameters recorded. It is concluded that in bovine neosporosis the placenta plays a central role in the pathogenesis and epidemiology of the infection, and that while primary tissue destruction by the parasite may endanger the fetus, the maternal and fetal inflammatory responses may also be damaging.

Animals↗