As of 2016, roughly 18.2 million of the approximately 36.9 million people living with AIDS globally were receiving combined antiretroviral therapy (cART). In spite of decades of research and development of this complex drug regimen, which is highly effective in preventing new infection, cells that are already infected with integrated HIV-1 genome are still able to produce viral RNAs and proteins. We have recently found that the viral RNA products (both coding and noncoding) are present in the extracellular vesicles such as exosomes, and can elicit detrimental effects in recipient cells including immune activation, specifically of macrophages and microglia contributing to HIV-1-associated neurocognitive disorders (HAND). Although the advent of cART has led to a decrease in the most severe HAND phenotype, HIV-associated dementia (HAD), the overall prevalence of HAND remains the same as the percentage of those with the less severe phenotype, Asymptomatic neurocognitive impairment (ANI), has increased. Furthermore, those with ANI have an increased propensity to develop the severe phenotype (HAD). Currently, there is no available treatment to prevent or hinder HAND in chronically infected patients which represents a gap of knowledge within the field of HIV-1 research. The long-term goal of this proposal to mitigate immune deregulation associated with HIV-1 pathogenesis, specifically within the CNS. The short-term goals include elucidating the consequences of autophagy inhibition in cART-treated cells, the release of cell-associated viral RNA through exosomes and exploring the effect of these exosomes on the recipient cells. Our preliminary data suggests that despite the use of antiretroviral therapy, viral RNAs, specifically non-coding RNAs such as trans-activating response (TAR) RNA and a recently discovered TAR-gag, are released from infected cells and cause immune dysfunction in the recipient cells. This is in line with findings that the autophagy pathway is generally blocked in HIV-1 infected cells resulting in increased levels of exosomal release. Additional data indicates that exosomal TAR RNA can activate NF-?B pathway through TLR3 activation, decrease apoptosis in uninfected cells, and increase susceptibility of recipient cells to infection. We hypothesize that HIV-1 utilizes host proteins and pathways to selectively package, viral, non-coding RNAs into exosomes and these exosomes activate the innate immune response and cause dysfunction in recipient neurons. The expected outcome of these studies is to decipher how antiretroviral treatment and autophagy inhibition cause an accumulation of cell-associated non-coding RNAs and proteins which are then selectively packaged into exosomes, how the release and composition of those exosomes can be regulated with specific inhibitors. Furthermore, these studies will determine the RNA-containing exosomal effect on nave recipient neurons pertaining to immune activation and cell death. Our studies will elucidate the potential exosomal contributions to HAND via inflammation in the CNS.
Currently there are no FDA-approved transcription inhibitors for the treatment of HIV-1, which allows the virus to continue low-level replication with an accumulation of cell-associated viral RNA, which is unable to be processed and degraded due to inhibition of the autophagy pathway. To alleviate the infected cell's burden, these viral products are incorporated into exosomes which can contribute to HIV-1 pathogenesis, particularly in the CNS. We propose to investigate the mechanism by which viral products are selectively incorporated into exosomes via manipulation of the autophagy and exosomal biogenesis pathways and elucidate the effect of the released exosomes of recipient cells, specifically neurons.
