Bacteria-instructed B cells cross-prime naïve CD8+ T cells triggering effective cytotoxic responses

In addition to triggering humoral responses, conventional B cells have been described in vitro to cross-present exogenous antigens activating naïve CD8⁺ T cells. Nevertheless, the way B cells capture these exogenous antigens and the physiological roles of B cell-mediated cross-presentation remain poorly explored. Here, we show that B cells capture bacteria by trans-phagocytosis from previously infected dendritic cells (DC) when they are in close contact. Bacterial encounter "instructs" the B cells to acquire antigen cross-presentation abilities, in a process that involves autophagy. Bacteria-instructed B cells, henceforth referred to as BacB cells, rapidly degrade phagocytosed bacteria, process bacterial antigens and cross-prime naïve CD8⁺ T cells which differentiate into specific cytotoxic cells that efficiently control bacterial infections. Moreover, a proof-of-concept experiment shows that BacB cells that have captured bacteria expressing tumor antigens could be useful as novel cellular immunotherapies against cancer.

[Herpes simplex virus bronchopneumonitis in patient with acute respiratory failure after surgery]

Herpes simplex virus bronchopneumonitis is a clinical entity described in critically ill patients and classically associated to immunosuppression. Recent reports have shown a higher frequency of virus detection from samples obtained by bronchoalveolar lavage of immunocompetent critically ill patients undergoing mechanical ventilation. This fact suggests its role as an independent pathogenic substrate. We report the case of a female patient who was admitted after an elective surgery of rectal tumor with suspected bronchoaspiration during anesthetic induction. The patient presented persistent fever despite broad spectrum antibiotic treatment. All cultures were negative for bacterial growth. The chest X-ray did not show opacifities. Prolonged mechanical ventilation with repeated failures to wean made it mandatory to perform percutaneous tracheostomy. A fibrobronchoscopy with bronchoalveolar lavage, performed previously, showed positive result for herpes simplex virus (PCR and specific nuclear inclusions in cells). Thus, treatment was initiated with acyclovir, with clinical improvement and weaning from mechanical ventilation.