Neither Hippurate-negative <Emphasis Type="Italic">Brachyspira pilosicoli</Emphasis> nor <Emphasis Type="Italic">Brachyspira pilosicoli</Emphasis> Type Strain Caused Diarrhoea in Early-weaned Pigs by Experimental Infection

A hippurate-negative biovariant of Brachyspira pilosicoli (B. pilosicoli ^hipp-) is occasionally isolated in diarrhoeic pigs in Finland, often concomitantly with hippurate-positive B. pilosicoli or Lawsonia intracellularis. We studied pathogenicity of B. pilosicoli ^hipp- with special attention paid to avoiding co-infection with other enteric pathogens. Pigs were weaned and moved to barrier facilities at the age of 11 days. At 46 days, 8 pigs were inoculated with B. pilosicoli ^hipp- strain Br1622, 8 pigs were inoculated with B. pilosicoli type strain P43/6/78 and 7 pigs were sham-inoculated. No signs of spirochaetal diarrhoea were detected; only one pig, inoculated with P43/6/78, had soft faeces from day 9 to 10 post inoculation. The pigs were necropsied between days 7 and 23 after inoculation. Live pigs were culture-negative for Brachyspira spp., but B. pilosicoli ^hipp- was reisolated from necropsy samples of two pigs. The lesions on large colons were minor and did not significantly differ between the three trial groups. In silver-stained sections, invasive spirochaetes were detected in colonic mucosae of several pigs in all groups. Fluorescent in situ hybridisation for genus Brachyspira, B. pilosicoli and strain Br1622 was negative. However, in situ detection for members of the genus Leptospira was positive for spirochaete-like bacteria in the colonic epithelium of several pigs in both infected groups as well as in the control group. L. intracellularis, Salmonella spp., Yersinia spp. and intestinal parasites were not detected. The failure of B. pilosicoli strains to cause diarrhoea is discussed with respect to infectivity of the challenge strains, absence of certain intestinal pathogens and feed and management factors.     

CD20, CD3, and CD40 ligand microclusters segregate three-dimensionally in vivo at B-cell-T-cell immunological synapses after viral immunity in primate brain

The clearance of virally infected cells from the brain is mediated by T cells that engage antigen-presenting cells to form supramolecular activation clusters at the immunological synapse. However, after clearance, the T cells persist at the infection site and remain activated locally. In the present work the long-term interactions of immune cells in brains of monkeys were imaged in situ 9 months after the viral inoculation. After viral immunity, the persistent infiltration of T cells and B cells was observed at the infection sites. T cells showed evidence of T-cell receptor signaling as a result of contacts with B cells. Three-dimensional analysis of B-cell-T-cell synapses showed clusters of CD3 in T cells and the segregation of CD20 in B cells, involving the recruitment of CD40 ligand at the interface. These results demonstrate that immunological synapses between B cells and T cells forming three-dimensional microclusters occur in vivo in the central nervous system and suggest that these interactions may be involved in the lymphocyte activation after viral immunity at the original infection site.