Antiretroviral drug therapy does not reduce neuroinflammation in an HIV-1 infection brain organoid model

BACKGROUND: HIV-1-associated neurocognitive impairment (HIV-1-NCI) is marked by ongoing and chronic neuroinflammation with loss and decline in neuronal function even when antiretroviral drug therapy (ART) successfully suppresses viral replication. Microglia, the primary reservoirs of HIV-1 in the central nervous system (CNS), play a significant role in maintaining this neuroinflammatory state. However, understanding how chronic neuroinflammation is generated and sustained by HIV-1, or impacted by ART, is difficult due to limited access to human CNS tissue. METHODS: We generated an in vitro model of admixed hematopoietic progenitor cell (HPC) derived microglia embedded into embryonic stem cell (ESC) derived Brain Organoids (BO). Microglia were infected with HIV-1 prior to co-culture. Infected microglia were co-cultured with brain organoids BOs to infiltrate the BOs and establish a model for HIV-1 infection, "HIV-1 M-BO". HIV-1 M-BOs were treated with ART for variable directions. HIV-1 infection was monitored with p24 ELISA and by digital droplet PCR (ddPCR). Inflammation was measured by cytokine or p-NF-kB levels using multiplex ELISA, flow cytometry and confocal microscopy. RESULTS: HIV-1 infected microglia could be co-cultured with BOs to create a model for "brain" HIV-1 infection. Although HIV-1 infected microglia were the initial source of pro-inflammatory cytokines, astrocytes, neurons and neural stem cells also had increased p-NF-kB levels, along with elevated CCL2 levels in the supernatant of HIV-1 M-BOs compared to Uninfected M-BOs. ART suppressed the virus to levels below the limit of detection but did not decrease neuroinflammation. CONCLUSIONS: These findings indicate that HIV-1 infected microglia are pro-inflammatory. Although ART significantly suppressed HIV-1 levels, neuronal inflammation persisted in ART-treated HIV-1 M-BOs. Together, these findings indicate that HIV-1 infection of microglia infiltrated into BOs provides a robust in vitro model to understand the impact of HIV-1 and ART on neuroinflammation.