HIV-Mediated Up-Regulation of Invariant Chain (CD74/MIF Receptor) Contributes to Generalized Immune Activation

YANINA GHIGLIONE; ANA MARÍA RODRIGUEZ; CRISTIAN DE CANDIA; L.LENG; R.BUCALA; M. SHINDLER; CAROBENE,M; F.BENAROCH; H. SALOMÓN; GABRIELA TURK

Boston

Congreso; CROI; 2011

Background: HIV-1 Nef up-regulates the invariant chain (Ii chain) on the surface of infected cells in vitro. Cell surface Ii chain (known as CD74) also serves as a receptor for the pro-inflammatory cytokine MIF (macrophage migration inhibitory factor), which is detected at high concentrations in the plasma of HIV-infected subjects. Nevertheless, the relationship between Ii chain/CD74 up-regulation in antigen presenting cells (APCs), and the subsequent mechanisms that follow engagement of CD74 by MIF have not been explored. Thus, we hypothesized that MIF-Ii chain interaction on HIV-infected APCs leads to increased pro-inflammatory cytokine levels and lymphocyte trans-activation. Methods: Monocyte-derived macrophages (MDMs) from healthy donors were infected with HIV-1 WT and a Nef deleted viral mutant (Nef), and then treated with MIF at day seven post-infection. CD74 up-regulation was monitored on infected MIF-treated MDMs by flow cytometry. In MDM culture supernatants, IL-6, IL-8 and IL-10 cytokine levels were measured by ELISA. Also, autologous lymphocytes were cultured with MDM culture supernatants and activation markers, HLA-DR and CD38, were analyzed by flow cytometry at day four. Analysis was performed using GraphPad Software. Results: IL-6 and IL-8 cytokine levels were increased in supernatants from NefWT-infected MDMs in a MIF dependent manner, compared to Nef-infected MDM cultures. In contrast, this effect could not be observed for the anti-inflammatory cytokine IL-10. Moreover, these supernatants induced higher activation of CD4+ T cells. Higher percentage of CD4+ T cells expressing the activation markers CD38 and HLA-DR was observed after a four-day lymphocyte culture with NefWT-infected MDM supernatants when compared to Nef-infected MDM supernatants. Pre-treatment of MDMs with anti-CD74 mAb BU-45, before addition of MIF, abrogated the effects observed on cytokine levels and lymphocyte activation. This indicates that by blocking CD74, the MIF effect is reverted. Conclusions: Data presented here support the hypothesis that an interaction between the cell surface expressed form of the Ii chain, CD74, and MIF could contribute to generate a pro-inflammatory environment in a Nef-dependent manner. These results support the idea that Nef-mediated up-regulation of Ii chain plays a relevant role in HIV immunopathogenesis, both by blocking HIV specific HLA-II antigen presentation and promoting generalized immune activation by MIF-interaction.