Advances in immunology

A lethal model of Leptospira infection in hamster nasal mucosa

Leptospirosis is a fatal zoonosis caused by contact between skin or a mucosal surface and contaminated soil or water. Hamsters were infected by intraperitoneal injection fto establish experimental leptospirosis, which is not a natural route of infection. There are no reports of nasal mucosal infection in hamsters. In this study, infection of the nasal mucosa was performed to establish a model of natural infection. Both methods of infection can cause lethal models with similar symptoms in the later stages of infection, such as weight loss, blood concentration, increased neutrophils (GRAN), and decreased lymphocytes (LYM) in the blood, severe organ damage and liver function obstruction. The burden of Leptospira in the organs and blood was lower in the mucosal inoculation groups at 1 day after infection. However, mucosal infection induced a higher Leptospira burden in urine than intraperitoneal infection in the late stages of infection. After nasal mucosal infection, antibody levels were higher and lasted longer. These results indicated that the route of nasal mucosal infection is a good choice for studying leptospirosis in hamsters.

Changes in behaviour, cortisol and lymphocyte types during isolation and group confinement of sheep

This experiment compared changes in complex behaviour patterns, adrenal corticosteroid secretion and the numbers of various types of lymphocytes in sheep that were subjected to the stress of confinement. Grazing Merino ewes (n=80 in five replicated experiments) were confined either in groups of four per pen or in total isolation from other sheep. The percentage of CD4+ lymphocytes increased while the percentage of CD8+ lymphocytes decreased over the experimental period. This result was more pronounced in isolated sheep than in grouped sheep. The increase in CD4:CD8 was greater for isolated sheep than for grouped sheep and greater for 2 week sheep than for 3 week sheep. The percentage of CD5+ cells also increased, less so in isolated than in grouped animals. Interpreting these changes as a recovery of immune competence following introduction of a stressor, it is apparent that isolation impaired immune system recovery more severely than group confinement. Physiological and behavioural adaptation over the period were characterized by a decline in the adrenocortical response, resumption of the normal pattern of flocking behaviour and a reduction in motor activity during the test. These findings add to the evidence pointing to the possible correspondence between critical features of the psychoneural, neuroendocrine and immune systems.