HIV Compartmentalization in the CNS and Its Impact in Treatment Outcomes and Cure Strategies

Characterization of HIV variants from paired Cerebrospinal fluid and Plasma samples in primary microglia and CD4+ T-cells

Despite antiretroviral therapy (ART), HIV persistence in the central nervous system (CNS) continues to cause a range of cognitive impairments in people living with HIV (PLWH). Upon disease progression, transmigrating CCR5-using T-cell tropic viruses are hypothesized to evolve into macrophage-tropic viruses in the CNS that can efficiently infect low CD4-expressing cells, such as microglia. We examined HIV-1 RNA concentration, co-receptor usage, and CSF compartmentalization in paired CSF and blood samples from 19 adults not on treatment. Full-length envelope CSF- and plasma-derived reporter viruses were generated from 3 subjects and phenotypically characterized in human primary CD4+ T-cells and primary microglia. Median HIV RNA levels were higher in plasma than in CSF (5.01 vs. 4.12 log10 cp/mL; p = 0.004), and coreceptor usage was mostly concordant for CCR5 across the paired samples (n = 17). Genetically compartmentalized CSF viral populations were detected in 2 subjects, one with and one without neurological symptoms. All viral clones could replicate in T-cells (R5 T cell-tropic). In addition, 3 CSF and 1 plasma patient-derived viral clones also had the capacity to replicate in microglia/macrophages and, therefore have an intermediate macrophage tropic phenotype. Overall, with this study, we demonstrate that in a subset of PLWH, plasma-derived viruses undergo genetic and phenotypic evolution within the CNS, indicating viral infection and replication in CNS cells. It remains to be studied whether the intermediate macrophage-tropic phenotype observed in primary microglia represents a midpoint in the evolution towards a macrophage-tropic phenotype that can efficiently replicate in microglial cells and propagate viral infection in the CNS.

Learning from cerebrospinal fluid drug-resistant HIV escape-associated encephalitis: a case report

BACKGROUND

In the era of antiretroviral therapy (ART), central nervous system (CNS) complications in patients with human immunodeficiency virus (HIV) infection are sometimes associated with cerebrospinal fluid (CSF) viral escape. Here, we reported a case of persistent CNS viral escape with recurrent symptomatic encephalitis, which had ultimate stabilization achieved by a combination of ART adjustment and corticosteroids.

CASE PRESENTATION

A 27-year-old man with HIV infection complained of recurrent headaches during the last year. His magnetic resonance imaging (MRI) presented diffused bilateral white matter lesions, and laboratory tests confirmed elevated CSF protein level, lymphocytic pleocytosis, and detectable CSF HIV RNA (774 copies/mL). Plasma HIV RNA was well suppressed with tenofovir, lamivudine, and lopinavir/ritonavir. Prednisone 60 mg once daily was initiated to reduce intracranial inflammation, followed by a good clinical response, with CSF HIV RNA still detectable (31.1 copies/mL). During the gradual tapering of prednisone, his headache relapsed, and booming viral loads were detected in both CSF (4580 copies/mL) and plasma (340 copies/mL) with consistent drug-resistant mutations. Thereupon, prednisone was resumed and the ART regimen was switched to zidovudine, lamivudine, and dolutegravir according to drug resistance tests. Persistent clinical recovery of symptoms, neuroimaging, and laboratory abnormalities were observed in the follow-up visits.

CONCLUSION

CSF and plasma HIV RNA and further drug resistance tests should be monitored in HIV-infected patients with neurologic symptoms, as opportunistic infections or tumors can be ruled out. ART optimization using a sensitive regimen may be crucial for addressing CSF viral escape and the related encephalitis.

HIV Tissue Reservoirs: Current Advances in Research

Acquired immunodeficiency syndrome (AIDS), caused by the human immunodeficiency virus (HIV), has become a heavy burden of disease and an important public health problem in the world. Although current antiretroviral therapy (ART) is effective at suppressing the virus in the blood, HIV still remains in two different types of reservoirs-the latently infected cells (represented by CD4⁺ T cells) and the tissues containing those cells, which may block access to ART, HIV-neutralizing antibodies and latency-reversing agents. The latter is the focus of our review, as blood viral load drops below detectable levels after ART, a deeper and more systematic understanding of the HIV tissue reservoirs is imperative. In this review, we take the lymphoid system (including lymph nodes, gut-associated lymphoid tissue, spleen and bone marrow), nervous system, respiratory system, reproductive system (divided into male and female), urinary system as the order, focusing on the particularity and importance of each tissue in HIV infection, the infection target cell types of each tissue, the specific infection situation of each tissue quantified by HIV DNA or HIV RNA and the evidence of compartmentalization and pharmacokinetics. In summary, we found that the present state of HIV in different tissues has both similarities and differences. In the future, the therapeutic principle we need to follow is to respect the discrepancy on the basis of grasping the commonality. The measures taken to completely eliminate the virus in the whole body cannot be generalized. It is necessary to formulate personalized treatment strategies according to the different characteristics of the HIV in the various tissues, so as to realize the prospect of curing AIDS as soon as possible.

The potential role of HIV-1 latency in promoting neuroinflammation and HIV-1-associated neurocognitive disorder

Despite potent suppression of HIV-1 viral replication in the central nervous system (CNS) by antiretroviral therapy (ART), between 15% and 60% of HIV-1-infected patients receiving ART exhibit neuroinflammation and symptoms of HIV-1-associated neurocognitive disorder (HAND) - a significant unmet challenge. We propose that the emergence of HIV-1 from latency in microglia underlies both neuroinflammation in the CNS and the progression of HAND. Recent molecular studies of cellular silencing mechanisms of HIV-1 in microglia show that HIV-1 latency can be reversed both by proinflammatory cytokines and by signals from damaged neurons, potentially creating intermittent cycles of HIV-1 reactivation and silencing in the brain. We posit that anti-inflammatory agents that also block HIV-1 reactivation, such as nuclear receptor agonists, might provide new putative therapeutic avenues for the treatment of HAND.