Robust Control of a Brain-Persisting Parasite through MHC I Presentation by Infected Neurons

Control of CNS pathogens by CD8 T cells is key to avoid fatal neuroinflammation. Yet, the modalities of MHC I presentation in the brain are poorly understood. Here, we analyze the antigen presentation mechanisms underlying CD8 T cell-mediated control of the Toxoplasma gondii parasite in the CNS. We show that MHC I presentation of an efficiently processed model antigen (GRA6-OVA), even when not expressed in the bradyzoite stage, reduces cyst burden and dampens encephalitis in C57BL/6 mice. Antigen presentation assays with infected primary neurons reveal a correlation between lower MHC I presentation of tachyzoite antigens by neurons and poor parasite control in vivo. Using conditional MHC I-deficient mice, we find that neuronal MHC I presentation is required for robust restriction of T. gondii in the CNS during chronic phase, showing the importance of MHC I presentation by CNS neurons in the control of a prevalent brain pathogen.

Microbial diversity in smoked salmon examined by a culture-independent molecular approach--a preliminary study

Microbial biodiversity in sliced vacuum-packed cold smoked salmon was investigated using culture-independent molecular biology techniques. Sliced smoked salmon was stored for 25 days after being packed at 4 degrees C. DNA was extracted from sliced vacuum-packed cold smoked salmon. PCR DNA amplification were carried out using universal eubacterial primers corresponding to Escherichia coli 16S rRNA gene. 16S rRNA genes were amplified, cloned in E. coli and compared using Amplification Ribosomal DNA Restriction Analysis (ARDRA). 106 clones were studied and classified into 13 Operational Taxonomic Units (OTUs). Sequences obtained to describe those 13 OTUs were compared to GenBank data. They indicated the presence of Vibrio species. Enterobacteraceae and also marine psychrophilic clones related to Alteromonas macleodii, which were not encountered within cultures, but no Gram-positive species have been obtained. Those results indicate that bias in description of microbial diversity may be encountred in both molecular and cultural techniques.