Estudo in vitro dos mecanismos da neuroinvasão e neurodisseminação do HIV

Currently it is observed that individuals infected by the human immunodeficiency virus (HIV), even under antiretroviral therapy, present comorbidities such as dementia. The understanding of the mechanisms of HIV infection and dissemination in the Central Nervous System (CNS), could clarify the development of these comorbidities in which neuronal degeneration occurs, designated as a HIV-associated neurocognitive disorders (HAND). The neuroinvasion mechanism is not yet clearly defined, but among the proposed mechanisms the most accepted is the Trojan Horse Hypothesis. This mechanism propose that HIV infects monocytes and CD4+ T lymphocytes present in peripheral blood and crosses the blood brain barrier (BBB), a permeable membrane essential in maintaining CNS homeotase, without being detected, in the form of provirus integrated into the genome of these cells. Once in the CNS, HIV can infect several cells, including perivascular macrophages, microglia and astrocytes. Some studies describe that these cells can be considered viral reservoirs because they allow the integration of the viral genome into the cell genome and, in more advanced stages of the infection, allow the spread of the virus in the CNS. The spread of HIV in the CNS will occur through viral proteins and host inflammatory mediators (cytokines and chemokines), associated with neuronal toxicity and consequent cognitive decline, released by infected cells. To contribute to the clarification of this issue, it is essential to understand how to influence the communication and interaction between monocytes, CD4+ T lymphocytes, perivascular macrophages, microglia, astrocytes and neuronal cells. Therefore, in the present work, infectiousness tests were performed between CNS cells, keeping the culture of donor cells and target cells in contact, or separated by a membrane (transwell system). Infectiousness assays were also performed by exposure of microglia and astrocytes to secretomes produced by CD4+ T lymphocytes, macrophages, microglia and astrocytes infected with different primary isolates of HIV-1 and HIV-2. In general, the results showed that infected cells do not behave in the same way for all primary strains, regardless of the type of HIV. In addition, they also demonstrated that HIV could infect microglia and astrocytes regardless of the absence or low expression of the CD4 receptor. Regarding astrocytes, their role as reservoirs of infection is suggested. The infectiousness assays between microglia and astrocytes show that neurodissemination is favored by cell contact, regardless of the strain used. However it was observed that separation of cells by membrane is not preventing infection, and there are situations in which the infection is favored. The infectiousness assays of microglia and astrocytes exposed to different secretomes, in the presence and absence of entry inhibitors, suggest that the infection may be mediated by viral particles and/or by components present in the secretomes produced by the different cell populations. Considering the results obtained, the next step will be to analyze the components of the secretomes that showed RT activity in the presence of entry inhibitors.