19 marzo 2019

Non-lysosomal Activation in Macrophages of Atlantic Salmon (Salmo salar) After Infection With Piscirickettsia salmonis.

DOI : 10.3389/fimmu.2019.00434

Jorge Valdés, Sebastián Reyes

Piscirickettsia salmonis is a facultative intracellular pathogen and etiological

agent of the systemic disease salmonid rickettsial septicemia. It has been

suggested that P. salmonis is able to survive in host macrophages, localized

within a vacuole like-compartment which prevents lysosomal degradation. However,

the relevant aspects of the pathogenesis of P. salmonis as the host modulation

that allow its intracellular survival have been poorly characterized. In this

study, we evaluated the role of lysosomes in the response to P. salmonis

infection in macrophage-enriched cell cultures established from Atlantic salmon

head kidneys. Bacterial infection was confirmed using confocal microscopy. A

gentamicin protection assay was performed to recover intracellular bacteria and

the 16S rDNA copy number was quantified through quantitative polymerase chain

reaction in order to determine the replication of P. salmonis within

macrophages. Lysosomal activity in Atlantic salmon macrophage-enriched cell

cultures infected with P. salmonis was evaluated by analyzing the lysosomal pH

and proteolytic ability through confocal microscopy. The results showed that P.

salmonis can survive ≥120 h in Atlantic salmon macrophage-enriched cell

cultures, accompanied by an increase in the detection of the 16S rDNA copy

number/cell. The latter finding suggests that P. salmonis also replicates in

Atlantic salmon macrophage-enriched cell cultures. Moreover, this bacterial

survival and replication appears to be favored by a perturbation of the

lysosomal degradation system. We observed a modulation in the total number of

lysosomes and lysosomal acidification following infection with P. salmonis.

Collectively, the results of this study showed that infection of Atlantic salmon

macrophages with P. salmonis induced limited lysosomal response which may be

associated with host immune evasion mechanisms of P. salmonis that have not been

previously reported.

Investigadores Participantes del Centro

Biocomputing and Applied Genomics Laboratory

Doctor en Biotecnología, Universidad Andrés Bello, Chile.


Immunogenomics Laboratory

Doctor en Microbiología, Universidad de Santiago, Chile.



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