Compartmentalized gene expression of toll-like receptors 2, 4 and 9 in the brain and peripheral lymphoid organs during canine visceral leishmaniasis

Visceral leishmaniasis is an important parasitic disease that affects humans and animals. The response against the protozoan involves the interaction of both innate and adaptive branches of the immune system, and an important immune sensor is represented by the toll-like receptor (TLR) family. Here, we investigated the pattern of TLR-2, TLR-4 and TLR-9 gene expression in different compartments (brain, choroid plexus, spleen and lymph node) of dogs naturally infected with Leishmania infantum. Gene expression of the TLRs varied according to the compartment evaluated. In the brain, there was only an upregulation of TLR-2, whereas in the choroid plexus, TLR-2 and TLR-9 were both upregulated. Further, the peripheral lymphoid organs (spleen and lymph nodes) showed increased TLR-2 and TLR-4 expression. This study provides the first insight about TLR expression in the central nervous system of infected dogs, and gives additional evidence of the compartmentalization of the immune response during visceral leishmaniasis.