To study the innate immune response produced specifically within the developing CNS, avoiding the influence of the immune system, employ viral infection model induced by intracerebral inoculation of dengue virus in neonatal mice. Eight newborn mice two
days old of the species Mus musculus and Swiss albino variety were inoculated intracerebrally with brain homogenate infected with Flavivirus species (DENV3 genotype III). Another group of animals was used as control (uninfected) and inoculated with an equal volume of non-infectious brain homogenate and maintained under the same conditions of those infected. After 7 days after infection the mice were sacrificed and patients have had their brains processed for immunostaining of astrocytes and microglia. We quantified the glial and astrocitic immune response in the stratum lacunosum molecular (Lac Mol), radiatum (Rad) and pyramidale (Pir) of hippocampus and in the stratum molecular of dentate gyrus (DGMol) using the optical ractionator to estimate the number of microglias and astrocytes in the hippocampus of infected and control animals. Intense reactive astrocytosis and microglial activation were associated with clinical signs of meningoencephalitis in neonate subjects. Although the number of activated microglia to be higher in infected than in control subjects in the GDMol (Inf:738,95 } 83,07 vs Cont: 232,73 } 70,38; p = 0,0035), Rad (Inf: 392,49 } 44,13 vs Cont:
62,76 } 15,86; p = 0,0004) the number of total microglias (activated or not) was different only in the stratum radiatum (Inf: 6.187,49 } 291,62; Cont: 4.011,89 } 509,73;p = 0,01). On the other hand the total number of astrocytes was higher in control than in infected subjects only in the DGMol (Inf: 8.720,17 } 903,11; Cont: 13.023,13 }1.192,14; p = 0,02). Taken together the results suggest that the immune innate response in neonate mice after encephalitis induced by DENV3 genotype III is associated with a higher increase in the activated microglias than astrocytes in a regional and laminardependent fashion. The patophysiology implications of these events remain to be investigated.
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