Papel dos receptores de quimiocina CCR2 e CCR5 na patogênese da infecção pelo vírus Chikungunya

Abstract

Chikungunya fever (CHIKF) is a viral disease that has the etiological agent known as Chikungunya virus (CHIKV) and it is transmitted mainly by the mosquitoes of the Aedes genus. The disease caused by the CHIKV shows signs and symptoms similar to other arboviral diseases that have clinical significance, such as the dengue fever. However, the main pathognomonic factor that differs CHIKF from other arboviral diseases is the debilitating and persistent arthralgia that can last for months or even years and the mechanisms involved in the pathogenesis of CHIKV-induced arthralgia are poorly understood. Recently, during standardization of the experimental model of CHIKV infection done in our laboratory, we observed that the inoculation of CHIKV on wild type mice (WT) induced several signs and symptoms associated with the infection that is normally seen in humans, such as the articular hypernociception and expressive increase of some chemokines related to the recruitment of macrophages and lymphocytes. Thereby, the aim of this work was to study the role of the chemokine type CC receptors (CCR2 and CCR5) in the pathogenesis of CHIKV in vitro and in vivo infection. To do so, WT mice of the C57BL/6 lineage were used along with and knockouts for CCR2 (CCR2-/- ) and CCR5 (CCR5-/- ) receptors. The expression profile of these receptors in different cell types, as well as their binding chemokines (CCL2, CCL3, CCL4 and CCL5), in addition to several clinical and inflammatory parameters normally associated with the disease in humans, were evaluated. Flow cytometry analyses showed increased expression of CCR2 and CCR5 receptors after the CHIKV infection predominantly in macrophages (F4/80+ cells) and lymphocytes (CD3+ ). On the WT mice, several signs of the disease along with inflammation were observed, such as: lymphopenia, increased CCL2, CCL3, CCL4 and CCCL5 chemokines and recovery of the viral load in several tissues, in addition to tissue damage and prolonged articular hypernociception. However, in the absence of the CCR2 and CCR5 receptors, the inflammation was more exacerbated, since in these groups a higher level of chemokines was found, as well as an increased neutrophil infiltrate and prolonged tissue damage in CCR2- /- mice. In the CCR5-/- mice, in addition to the mentioned findings, a higher viral recovery was also observed in initial post-infection time. However, the hypernociception observed in the groups of knockout animals happened only in the initial time with respect to the CCR2-/- , or nonexistent, in the CCR5-/- mice. In vitro studies also demonstrated that the virus was able to infect macrophages derived from WT mice and knockouts to the CCR2 and CCR5 receptors, but without toxicity to the cells. Interestingly, cells derived from CCR2-/- or CCR5-/- mice showed lower recovered viral load. As a final point, this work reinforces the importance of macrophages and lymphocytes in the control of the disease caused by CHIKV, since they are the main cells affected by the absence of the CCR2 and CCR5 receptors, besides demonstrating that the receptors studied seem to be important in the assembly of the appropriate immune response for fighting the virus and resolving the inflammation process. These receptors also interfere directly or indirectly in mechanisms associated with the hypernociception induced by the CHIKV infection.