EcoHIV infection of mice establishes latent viral reservoirs in T cells and active viral reservoirs in macrophages that are sufficient for induction of neurocognitive impairment

Abstract

Suppression of HIV replication by antiretroviral therapy (ART) or host immunity can prevent AIDS but not other HIV-associated conditions including neurocognitive impairment (HIV-NCI). Pathogenesis in HIV-suppressed individuals has been attributed to reservoirs of latent-inducible virus in resting CD4+ T cells. Macrophages are persistently infected with HIV but their role as HIV reservoirs in vivo has not been fully explored. Here we show that infection of conventional mice with chimeric HIV, EcoHIV, reproduces physiological conditions for development of disease in people on ART including immunocompetence, stable suppression of HIV replication, persistence of integrated, replication-competent HIV in T cells and macrophages, and manifestation of learning and memory deficits in behavioral tests, termed here murine HIV-NCI. EcoHIV established latent reservoirs in CD4+ T lymphocytes in chronically-infected mice but could be induced by epigenetic modulators ex vivo and in mice. In contrast, macrophages expressed EcoHIV constitutively in mice for up to 16 months; murine leukemia virus (MLV), the donor of gp80 envelope in EcoHIV, did not infect macrophages. Both EcoHIV and MLV were found in brain tissue of infected mice but only EcoHIV induced NCI. Murine HIV-NCI was prevented by antiretroviral prophylaxis but once established neither persistent EcoHIV infection in mice nor NCI could be reversed by long-acting antiretroviral therapy. EcoHIV-infected, athymic mice were more permissive to virus replication in macrophages than were wild-type mice, suffered cognitive dysfunction, as well as increased numbers of monocytes and macrophages infiltrating the brain. Our results suggest an important role of HIV expressing macrophages in HIV neuropathogenesis in hosts with suppressed HIV replication.

Prevention and treatment of HIV infection and cognitive disease in mice by innate immune responses

“…We reported that prophylaxis with antiretrovirals prevented EcoHIV infection and the development of HIV–NCI in mice ( Gu et al, 2018 ). To test whether virus inhibited by poly I:C retains the ability to cause disease, the experiment shown in Fig.…”

“…EcoHIV infects CD4 positive T cells and F4/80 positive macrophages systemically as well as brain microglia. After an early peak its replication is controlled, at least in part, by adaptive immune responses but chronically infected mice maintain some virus expression in macrophages and demonstrate impaired learning analogous to HIV-infected people on effective antiretroviral treatment ( Potash et al, 2005 ; Gu et al, 2018 ; Kelschenbach et al, 2019 ). The continued expression of HIV proteins in EcoHIV infected mice has allowed evaluation of vaccines to prevent infection and drugs to treat infection (Hadas et al, 2007; Im et al, 2011 ; Liu et al, 2018 ; Roshorm et al, 2009 , 2012 ; Saini et al, 2007 ; Tomusange et al, 2016a , 2016b ) and the persistence of HIV-associated neurocognitive impairment (HIV–NCI) in this model has allowed studies of some of the routes to pathogenesis and NCI treatment ( He et al, 2014 ; Kelschenbach et al, 2019 ; Bertrand et al, 2019 ; Jones et al, 2016 ; Kim et al, 2019 ; Nedelcovych et al, 2017 , 2019 ; Olson et al, 2018 ).…”

Selective peroxisome proliferator‐activated receptor‐gamma modulator, INT131 exhibits anti‐inflammatory effects in an EcoHIV mouse model

“…33 The EcoHIV model captures many aspects of HAND, for example, infection of T cells, macrophages and microglia, mucosal transmission of virus, normal CD4:CD8 ratio, a partially functional immune system, inflammatory responses in the brain, microgliosis, and neurocognitive impairment. 60,61 Numerous reports, including work from our laboratory, support the notion that this mouse model can be used as a versatile tool for characterizing potential anti-inflammatory therapeutics. 41,53,62 In this study, we utilized primary cultures of mouse glial cells exposed to EcoHIV which resulted in a significant increase in several inflammatory markers (ie, TNFα, IL-1β, IL-6, C3, CCL2, CCL3, and CXCL10) that have previously been reported to be implicated in the context of HAND.…”

Potential pharmacological approaches for the treatment of HIV-1 associated neurocognitive disorders

“…EcoHIV Detectable viral load in the brain, neuroinflammation, loss of MAP-2 and synapsin II staining [179,337] Impaired working and spatial memory [179,181,182] Non-rodent animal models SIV infected macaques Depletion of CD4+ cells, detectable viral load in the brain, neuroinflammation, neuronal loss [162] Impaired performance in tasks assessing memory, fine/ general motor skills, motivation, reaction time, spatial working memory [338] FIV infected cats Encephalopathy, reduced peripherical and motor neuron conductance [206,207] Aggression, loss of socialization, gait changes [206,207] mice developed age-specific memory deficits and the model helped to delineate cellular pathways involved in gp120 mediated neurotoxicity [167,168]. Similarly, a Tat transgenic mouse model was also developed where Tat is expressed under the control of a doxycycline-dependent GFAP promoter, allowing for these mice to develop Tat-dependent brain pathologies such as astrogliosis, infiltration of monocytes/T-cells and premature death [169].…”

“…This chimeric virus replaces gp120 with the murine leukemia virus gp80, facilitating entry into mouse cells [ 174 ]. Several studies have shown that mice infected with this chimeric strain display stable pro-virus in T-cells and macrophages, mucosal transmission of virus, normal CD4:CD8 ratios, a partially functional immune system and neurocognitive impairment [ 175 , 176 ]. Our group along with others has demonstrated that intracranial (IC) administration of EcoHIV at a dose of 1x10 6 pg p24 directly into the caudate putamen results in increased levels of several inflammatory genes [ 177 – 179 ].…”