BRUCELLA ABORTUS INDUCES NEURONAL DEATH THROUGH ACTIVATION OF MICROGLIA

RODRIGUEZ ANA M; MIRAGLIA M CRUZ; COSTA OLIVEIRA SERGIO; BARRIONUEVO PAULA; SILVA COSTA FRANCO MIRIAM; JANCIC CAROLINA; DELPINO M VICTORIA; GIAMBARTOLOMEI GH

Congreso; 42. LXI Reunión Anual de la Sociedad Argentina de Inmunología (SAI). 4-7 Noviembre 2013.; 2013

Central nervous system invasion by bacteria of the genus Brucella results in an inflammatory disorder called neurobrucellosis. B. abortus infects astrocytes and microglia, eliciting the production of pro-inflammatory cytokines which in turn induce glial apoptosis. The aim of this study was to determine the mechanisms of neuronal death induced by B. abortus. We evaluated the direct role of the bacterium on neurons and the effect that infected glial cell could have on them. For this, murine neurons were cultured alone or co-cultured with microglial cells (primary culture or the BV-2 cell line) in the presence or not of B. abortus. The viability of neurons was determined by microscopy and the secretion of cytokines by ELISA. Both, confocal microscopy using a GFP-B. abortus (multiplicity of infection (MOI) 100) and determination of bacterial load (MOI 1000, 500 and 50) demonstrated that B. abortus was unable to infect neurons or induce their death. Neurons were unable to secrete IL-6 and TNF-α in response to B. abortus (p>0.05 with respect to untreated cells). Yet, when neurons were co-cultured with microglia the number of viable neurons significantly decreased as a function of the number of microglia present in the culture (ratio neuron: microglia 1:20, 1:4, 1:2 and 1:1; p<0.05) and the amount of heat-killed B. abortus (106, 107, 108 and 109 CFU/ml; p<0,05). This phenomenon was observed with primary microglia or BV-2 cells. Thus, although B. abortus was unable to directly induce neuronal death, the bacterium was able to kill neurons by activation of microglia, the macrophages of the central nervous system. These results describe part pf the mechanisms whereby B. abortus could induce neuronal death in neurobrucellosis.