Animal models in HIV cure research

The CD8+ T Cell Noncytotoxic Antiviral Responses

The CD8+ T cell noncytotoxic antiviral response (CNAR) was discovered during studies of asymptomatic HIV-infected subjects more than 30 years ago. In contrast to CD8+ T cell cytotoxic lymphocyte (CTL) activity, CNAR suppresses HIV replication without target cell killing. This activity has characteristics of innate immunity: it acts on all retroviruses and thus is neither epitope specific nor HLA restricted. The HIV-associated CNAR does not affect other virus families. It is mediated, at least in part, by a CD8+ T cell antiviral factor (CAF) that blocks HIV transcription. A variety of assays used to measure CNAR/CAF and the effects on other retrovirus infections are described. Notably, CD8+ T cell noncytotoxic antiviral responses have now been observed with other virus families but are mediated by different cytokines. Characterizing the protein structure of CAF has been challenging despite many biologic, immunologic, and molecular studies. It represents a low-abundance protein that may be identified by future next-generation sequencing approaches. Since CNAR/CAF is a natural noncytotoxic activity, it could provide promising strategies for HIV/AIDS therapy, cure, and prevention.

Impacts of HIV Cure Interventions on Viral Reservoirs in Tissues

HIV reservoirs persist in infected individuals despite combination antiretroviral therapy and can be identified in secondary lymphoid tissues, in intestinal tissues, in the central nervous system as well as in blood. Clinical trials have begun to explore effects of small molecule interventions to perturb the latent viral infection, but only limited information is available regarding the impacts of HIV cure-related clinical interventions on viral reservoirs found in tissues. Of the 14 HIV cure-related clinical trials since 2012 that have evaluated the effects of small molecule interventions in vivo, four trials have examined the impacts of the interventions in peripheral blood as well as other tissues that harbor persistent HIV. The additional tissues examined include cerebral spinal fluid, intestines and lymph nodes. We provide a comparison contrast analyses of the data across anatomical compartments tested in these studies to reveal where peripheral blood analyses reflect outcomes in other tissues as well as where the data reveal differences between tissue outcomes. We also summarize the current knowledge on these topics and highlight key open questions that need to be addressed experimentally to move the HIV cure research field closer to the development of an intervention strategy capable of eliciting long-term antiretroviral free remission of HIV disease.

Modulatory Effects of Nicotine on neuroHIV/neuroAIDS

Nicotine, one of the key active ingredients in tobacco smoke, exerts its effects via binding to nicotinic acetylcholine receptors (nAChRs). Although both negative and positive pharmacological effects of nicotine have been shown in numerous animals and human studies, its interaction with human immunodeficiency virus-1 (HIV-1) have not been fully elucidated. Even though combined anti-retroviral therapy (cART) limits the progression of HIV-1 to acquired immune deficiency syndrome (AIDS), HIV-associated neurocognitive disorders (HAND) remain prevalent. There is thus a compelling need to enhance our understanding of HAND-related neurologic dysfunction. Some biochemical pathways and physiological dysfunctions have been found to be shared by HAND and Alzheimer's (AD) or Parkinson's (PD) diseases, and nicotine may exert the same neuroprotection in HAND that has been observed in both AD and PD. In the past dozen years, various potential therapeutic effects of nicotine such as neuroprotection have been revealed in both in vivo and in vitro studies, including using HIV-1 transgenic (HIV-1Tg) rat model, which mimics HIV-infected patients receiving cART. In the current review, we describe recent progress in the prevalence of HIV/AIDS with and without cigarette smoking, some animal models for studying neural dysfunction associated with HIV-1 infection, elucidating the modulatory effects of cigarette smoking/nicotine on HIV/AIDS, the anti-inflammatory effects of nicotine, and the neuroprotective effects observed in HIV-1Tg rat model. Taken together, these findings suggest the following: although tobacco smoking does cause deleterious effects in both health and disease conditions such as HIV infection, nicotine, the significant component of tobacco smoke, has been shown to possess some neuroprotective effects in HIV patients, possible via its anti-inflammatory activities. It is therefore necessary to study nicotine's dual effects on neuroHIV/neuroAIDS in hope of better defining the potential medical uses of nicotine or its analogues, and to make them available in a purer and less dangerous form.

Mechanisms of CD8+ T cell-mediated suppression of HIV/SIV replication

In this article, we summarize the role of CD8⁺ T cells during natural and antiretroviral therapy (ART)-treated HIV and SIV infections, discuss the mechanisms responsible for their suppressive activity, and review the rationale for CD8⁺ T cell-based HIV cure strategies. Evidence suggests that CD8⁺ T cells are involved in the control of virus replication during HIV and SIV infections. During early HIV infection, the cytolytic activity of CD8⁺ T cells is responsible for control of viremia. However, it has been proposed that CD8⁺ T cells also use non-cytolytic mechanisms to control SIV infection. More recently, CD8⁺ T cells were shown to be required to fully suppress virus production in ART-treated SIV-infected macaques, suggesting that CD8⁺ T cells are involved in the control of virus transcription in latently infected cells that persist under ART. A better understanding of the complex antiviral activities of CD8⁺ T cells during HIV/SIV infection will pave the way for immune interventions aimed at harnessing these functions to target the HIV reservoir.