RESUMEN
One of the most characteristic pathological changes in cats that have succumbed to feline infectious peritonitis (FIP) is a multifocal granulomatous phlebitis. Although it is now well established that leukocyte extravasation elicits the inflammation typically associated with FIP lesions, relatively few studies have aimed at elucidating this key pathogenic event. The upregulation of adhesion molecules on the endothelium is a prerequisite for stable leukocyte-endothelial cell (EC) adhesion that necessarily precedes leukocyte diapedesis. Therefore, the present work focused on the expression of the EC adhesion molecules and possible triggers of EC activation during the development of FIP. Immunofluorescence analysis revealed that the endothelial expression of P-selectin, E-selectin, intercellular adhesion molecule 1 (ICAM-1) and vascular cell adhesion molecule 1 (VCAM-1) was elevated in veins close to granulomatous infiltrates in the renal cortex of FIP patients compared to non-infiltrated regions and specimens from healthy cats. Next, we showed that feline venous ECs become activated when exposed to supernatant from feline infectious peritonitis virus (FIPV)-infected monocytes, as indicated by increased adhesion molecule expression. Active viral replication seemed to be required to induce the EC-stimulating activity in monocytes. Finally, adhesion assays revealed an increased adhesion of naive monocytes to ECs treated with supernatant from FIPV-infected monocytes. Taken together, our results strongly indicate that FIPV activates ECs to increase monocyte adhesion by an indirect route, in which proinflammatory factors released from virus-infected monocytes act as key intermediates.
Asunto(s)
Moléculas de Adhesión Celular/genética , Coronavirus Felino/fisiología , Células Endoteliales/virología , Peritonitis Infecciosa Felina/virología , Corteza Renal/virología , Monocitos/virología , Animales , Gatos , Adhesión Celular , Moléculas de Adhesión Celular/inmunología , Células Cultivadas , Coronavirus Felino/genética , Selectina E/genética , Selectina E/inmunología , Células Endoteliales/citología , Células Endoteliales/inmunología , Peritonitis Infecciosa Felina/genética , Peritonitis Infecciosa Felina/inmunología , Peritonitis Infecciosa Felina/fisiopatología , Molécula 1 de Adhesión Intercelular/genética , Molécula 1 de Adhesión Intercelular/inmunología , Corteza Renal/citología , Corteza Renal/inmunología , Monocitos/inmunología , Selectina-P/genética , Selectina-P/inmunología , Regulación hacia Arriba , Molécula 1 de Adhesión Celular Vascular/genética , Molécula 1 de Adhesión Celular Vascular/inmunologíaRESUMEN
Human African trypanosomiasis or sleeping sickness, caused by the protozoan parasite Trypanosoma brucei, is characterized by the manipulation of the host's immune response to ensure parasite invasion and persistence. Uncovering key molecules that support parasite establishment is a prerequisite to interfere with this process. We identified Q586B2 as a T. brucei protein that induces IL-10 in myeloid cells, which promotes parasite infection invasiveness. Q586B2 is expressed during all T. brucei life stages and is conserved in all Trypanosomatidae. Deleting the Q586B2-encoding Tb927.6.4140 gene in T. brucei results in a decreased peak parasitemia and prolonged survival, without affecting parasite fitness in vitro, yet promoting short stumpy differentiation in vivo. Accordingly, neutralization of Q586B2 with newly generated nanobodies could hamper myeloid-derived IL-10 production and reduce parasitemia. In addition, immunization with Q586B2 delays mortality upon a challenge with various trypanosomes, including Trypanosoma cruzi. Collectively, we uncovered a conserved protein playing an important regulatory role in Trypanosomatid infection establishment.