HIV infection in humans and simian immunodeficiency virus (SIV) infection in macaques result in encephalitis in approximately one-quarter of infected individuals and is characterized by infiltration of the brain with infected and activated macrophages. 1-(2-chlorphenyl)-N-methyl-N-(1-methylpropyl)-3-isoquinoline-carboxamide (PK11195) is a ligand specific for the peripheral benzodiazepine receptor abundant on macrophages and is expressed in low levels in the noninfected brain. We hypothesized that positron-emission tomography (PET) with the carbon-11–labeled, R-enantiomer form of PK11195 ([11C](R)-PK11195) could image brain macrophages and hence the development of encephalitis in vivo. [11C](R)-PK11195 binding was assessed in the brain using PET in 11 SIV infected macaques, six of which showed increased binding in vivo. Postmortem examination of the brain in these six macaques demonstrated encephalitis, while macaques that did not show an increase in [11C](R)-PK11195 binding did not develop SIV encephalitis. Brain tissue from SIV encephalitic macaques also showed increased [3H](R)-PK11195 binding compared with binding in nonencephalitic macaques. Increased PK11195 binding in vivo and in postmortem brain tissue correlated with abundance of macrophages but not astrocytes. Our results suggest that PET [11C](R)-PK11195 imaging can detect the presence of macrophages in SIV encephalitis in vivo and may be useful to predict the development of HIV encephalitis and in studies of the pathogenesis and treatment of HIV dementia.
Sriram Venneti, Brian J. Lopresti, Guoji Wang, Stephanie J. Bissel, Chester A. Mathis, Carolyn C. Meltzer, Fernando Boada, Saverio Capuano III, Geraldine J. Kress, Denise K. Davis, James Ruszkiewicz, Ian J. Reynolds, Michael Murphey-Corb, Anita M. Trichel, Stephen R. Wisniewski, Clayton A. Wiley
Transcutaneous immunization (TCI), the application of vaccines on the skin, induces robust systemic and mucosal antibodies in animal models and in humans. The means by which mucosal immune responses to vaccine antigens are elicited by TCI has not been well characterized. We examined the effect of TCI with an HIV peptide vaccine on the induction of mucosal and systemic CTL responses and protective immunity against mucosal challenge with live virus in mice. Robust HIV-specific CTL responses in the spleen and in the gut mucosa were detected after TCI. The responses were dependent upon the addition of an adjuvant and resulted in protection against mucosal challenge with recombinant vaccinia virus encoding HIV gp160. Although it is clear that adjuvant-activated DCs migrated mainly to draining lymph nodes, coculture with specific T cells and flow cytometry studies with DCs isolated from Peyer’s patches after TCI suggested that activated DCs carrying skin-derived antigen also migrated from the skin to immune-inductive sites in gut mucosa and presented antigen directly to resident lymphocytes. These results and previous clinical trial results support the observation that TCI is a safe and effective strategy for inducing strong mucosal antibody and CTL responses.
Igor M. Belyakov, Scott A. Hammond, Jeffrey D. Ahlers, Gregory M. Glenn, Jay A. Berzofsky
In vivo blockade of CD28 and CD40 T cell costimulation pathways during acute simian immunodeficiency virus (SIV) infection of rhesus macaques was performed to assess the relative contributions of CD4+ T cells, CD8+ T cells, and Ab responses in modulating SIV replication and disease progression. Transient administration of CTLA4-Ig and anti–CD40L mAb to SIV-infected rhesus macaques resulted in dramatic inhibition of the generation of both SIV-specific cellular and humoral immune responses. Acute levels of proliferating CD8+ T cells were associated with early control of SIV viremia but did not predict ensuing set point viremia or survival. The level of in vivo CD4+ T cell proliferation during acute SIV infection correlated with concomitant peak levels of SIV plasma viremia, whereas measures of in vivo CD4+ T cell proliferation that extended into chronic infection correlated with lower SIV viral load and increased survival. These results suggest that proliferating CD4+ T cells function both as sources of virus production and as antiviral effectors and that increased levels of CD4+ T cell proliferation during SIV infections reflect antigen-driven antiviral responses rather than a compensatory homeostatic response. These results highlight the interrelated actions of CD4+ and CD8+ T cell responses in vivo that modulate SIV replication and pathogenesis.
David A. Garber, Guido Silvestri, Ashley P. Barry, Andrew Fedanov, Natalia Kozyr, Harold McClure, David C. Montefiori, Christian P. Larsen, John D. Altman, Silvija I. Staprans, Mark B. Feinberg
Protease inhibitors decrease the viral load in HIV patients, however the patients develop hypertriglyceridemia, hypercholesterolemia, and atherosclerosis. It has been assumed that protease inhibitor–dependent increases in atherosclerosis are secondary to the dyslipidemia. Incubation of THP-1 cells or human PBMCs with protease inhibitors caused upregulation of CD36 and the accumulation of cholesteryl esters. The use of CD36-blocking antibodies, a CD36 morpholino, and monocytes isolated from CD36 null mice demonstrated that protease inhibitor–induced increases in cholesteryl esters were dependent on CD36 upregulation. These data led to the hypothesis that protease inhibitors induce foam cell formation and consequently atherosclerosis by upregulating CD36 and cholesteryl ester accumulation independent of dyslipidemia. Studies with LDL receptor null mice demonstrated that low doses of protease inhibitors induce an increase in the level of CD36 and cholesteryl ester in peritoneal macrophages and the development of atherosclerosis without altering plasma lipids. Furthermore, the lack of CD36 protected the animals from protease inhibitor–induced atherosclerosis. Finally, ritonavir increased PPAR-γ and CD36 mRNA levels in a PKC- and PPAR-γ–dependent manner. We conclude that protease inhibitors contribute to the formation of atherosclerosis by promoting the upregulation of CD36 and the subsequent accumulation of sterol in macrophages.
James Dressman, Jeanie Kincer, Sergey V. Matveev, Ling Guo, Richard N. Greenberg, Theresa Guerin, David Meade, Xiang-An Li, Weifei Zhu, Annette Uittenbogaard, Melinda E. Wilson, Eric J. Smart
Timothy W. Schacker, Phuong L. Nguyen, Gregory J. Beilman, Steven Wolinsky, Matthew Larson, Cavan Reilly, Ashley T. Haase