Influence of enriched environment on viral encephalitis outcomes: behavioral and neuropathological changes in albino Swiss mice.
An enriched environment has previously been described as enhancing natural killer cell activity of recognizing and killing virally infected cells. However, the effects of environmental enrichment on behavioral changes in relation to virus clearance and the neuropathology of encephalitis have not been studied in detail. We tested the hypothesis that environmental enrichment leads to less CNS neuroinvasion and/or more rapid viral clearance in association with T cells without neuronal damage. Stereology-based estimates of activated microglia perineuronal nets and neurons in CA3 were correlated with behavioral changes in the Piry rhabdovirus model of encephalitis in the albino Swiss mouse. Two-month-old female mice maintained in impoverished (IE) or enriched environments (EE) for 3 months were behaviorally tested. After the tests, an equal volume of Piry virus (IEPy, EEPy)-infected or normal brain homogenates were nasally instilled. Eight days post-instillation (dpi), when behavioral changes became apparent, brains were fixed and processed to detect viral antigens, activated microglia, perineuronal nets, and T lymphocytes by immuno- or histochemical reactions. At 20 or 40 dpi, the remaining animals were behaviorally tested and processed for the same markers. In IEPy mice, burrowing activity decreased and recovered earlier (8-10 dpi) than open field (20-40 dpi) but remained unaltered in the EEPy group. EEPy mice presented higher T-cell infiltration, less CNS cell infection by the virus and/or faster virus clearance, less microgliosis, and less damage to the extracellular matrix than IEPy. In both EEPy and IEPy animals, CA3 neuronal number remained unaltered. The results suggest that an enriched environment promotes a more effective immune response to clear CNS virus and not at the cost of CNS damage.
Universidade Federal do Pará, Instituto de Ciências Biológicas, Laboratório de Investigações em Neurodegeneração e Infecção, Hospital Universitário João de Barros Barreto, Belém, Brazil.
Aline Andrade
AA
de Sousa
Renata
R
Reis
João
J
Bento-Torres
Nonata
N
Trévia
Nara Alves de Almeida
NA
Lins
Aline
A
Passos
Zaire
Z
Santos
José Antonio Picanço
JA
Diniz
Pedro Fernando da Costa
PF
Vasconcelos
Colm
C
Cunningham
Victor Hugh
VH
Perry
Cristovam Wanderley Picanço
CW
Diniz
D000818:Animals; D001522:Behavior, Animal; D002490:Central Nervous System / Q000276:immunology / Q000473:pathology / Q000821:virology*; D018792:Encephalitis, Viral / Q000276:immunology* / Q000473:pathology / Q000821:virology; D005260:Female; D051379:Mice; D017628:Microglia / Q000378:metabolism*; D009474:Neurons; D012209:Rhabdoviridae; D018353:Rhabdoviridae Infections / Q000276:immunology* / Q000473:pathology; D013601:T-Lymphocytes / Q000276:immunology / Q000821:virology; D016896:Treatment Outcome
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