Increasing evidence indicates that the expression of the human immunodeficiency virus-1 (HIV-1) Nef protein significantly influences the activation state of the host cell. Here we report that Nef specifically activates STAT3 in primary human monocyte-derived macrophages (MDM). This was demonstrated by both single-cycle infection experiments driven by Vesicular Stomatitis virus glycoprotein (VSV-G) pseudotyped HIV-1 and treatment with exogenous recombinant Nef. The analysis of the effects of Nef mutants revealed that domains of the C-terminal flexible loop interacting with the cell endocytotic machinery are involved in the STAT3 activation. In particular, our data suggest that the Nef-dependent STAT3 activation relies on the targeting of Nef to the late endosome/lysosome compartment. In addition, we found that Nef activates STAT3 through a mechanism mediated by the release of soluble factor(s), including MIP-1alpha, that requires de novo protein synthesis but appears independent from the activation of src tyrosine kinases. The results presented here support the idea that the first intervention of Nef in the intracellular signaling of monocyte-macrophages could generate, by means of the release of soluble factor(s), a secondary wave of activation that could be of a potential pathogenetic significance.

Herpes simplex viruses (HSV) infect human and murine dendritic cells (DCs) and interfere with their immunostimulatory functions in culture. HSV-2 infection increases human immunodeficiency virus (HIV) spread in patients, and DCs also promote HIV infection. We have studied these topics in rhesus macaque monocyte-derived DCs (moDCs) to set the stage for future studies of these issues in animals. We provide the first evidence that IntroductionDendritic cells (DCs) are involved in innate and adaptive immunity. [1][2][3][4][5] DCs survey for pathogens to which they respond innately while also processing pathogens and presenting antigenic determinants to induce adaptive immune responses. DCs need to be activated or matured to stimulate potent adaptive immunity. 6 Maturation involves the up-regulation of molecules on the DC surface and secretion of cytokines and chemokines that encourage the DC-T cell interactions needed to elicit strong immunity. Many pathogens trigger these pathways, modifying DC functions to encourage effective immune activation and clearance of infection. [7][8][9][10] Yet, other pathogens like immunodeficiency viruses (human [HIV] and simian [SIV]) [11][12][13][14][15] and herpes simplex viruses (HSV) [16][17][18] exploit DC biology to facilitate infection and elicit immune responses incapable of preventing or eradicating infection. Moreover, there is a strong correlation between genital HSV (HSV-2) infection and the probability of acquiring HIV. 19 Understanding how this might be orchestrated at the DC level is central to developing strategies to prevent DC-driven HIV spread. 12 Primary HSV-2 infection, occurring at the mucosal surfaces, is typically followed by the establishment of latency in the sacral root ganglia. 20 Neutralizing antibodies (Abs) and antiviral CD4 ϩ and CD8 ϩ T cells are induced, 20 which ultimately restrict virus replication at local sites to resolve (primary and reactivated) lesions. 21,22 DCs likely play a key role by orchestrating responses to HSV, 21,23-25 although low-level productive infection of DCs might also contribute to virus spread. 18 HSV infection of human monocytederived DCs (moDCs) is cytopathic 23,26,27 and results in the down-modulation of several surface markers involved in the activation of T cells. [16][17][18] While this would result in mediocre anti-HSV immunity allowing the establishment of HSV infection (but not preventing infection), it must be sufficient to clear virus upon reactivation. 24,25 Herpetic lesions also comprise activated leukocyte infiltrates and enable direct blood contact, providing mechanisms for increased HIV spread. It is possible that HSV-2 infection of immature DCs additionally alters innate DC responses and compromises the ability of DCs to elicit potent adaptive responses to other pathogens, thereby further exacerbating HIV infection.The initial step toward dissecting this biology in a relevant animal model was to validate HSV-2 infection of macaque DCs. Supported by National Institutes of Health (NIH) grants R01 AI040877 an...