Through the Looking-Glass: Psychoneuroimmunology and the Microbiome-Gut-Brain Axis in the Modern Antiretroviral Therapy Era

Tryptophan-Kynurenine Pathway Activation and Cognition in Virally Suppressed Women With HIV

BACKGROUND

Immune and cognitive dysfunction persists even in virally suppressed women with HIV (VS-WWH). Since inflammation and HIV proteins induce the enzyme indoleamine 2,3-dioxygenase (IDO), converting tryptophan (T) to kynurenine (K) while producing downstream neurotoxic metabolites, we investigated IDO activation (KT ratio) in relation to cognition in VS-WWH and demographically similar women without HIV (WWoH).

METHODS

Ninety-nine VS-WWH on stable antiretroviral therapy and 102 WWoH (median age 52 vs 54 years; 73% vs 74% Black, respectively) from the New York and Chicago sites of the Women's Interagency HIV Study (WIHS) completed a neuropsychological test battery assessing motor function, processing speed, attention/working memory, verbal fluency, verbal learning and memory, and executive function and had plasma measured for tryptophan-kynurenine metabolites through liquid chromatography-tandem mass spectrometry and monocyte-derived [soluble cluster of differentiation-14 (sCD14), soluble cluster of differentiation-163 (sCD163), monocyte chemoattractant protein-1 (MCP-1)] plus general inflammatory markers [tumor necrosis factor alpha-2 receptor (TNF-R2), high-sensitivity C-reactive protein, high-sensitivity interleukin-6] through enzyme-linked immunosorbent assays between 2017 and 2020.

RESULTS

VS-WWH had a higher KT ratio (P < 0.01) and higher sCD14 levels (P < 0.05) compared with WWoH. Higher sCD163 was associated with higher KT ratio (R = 0.29, P < 0.01) and worse fine motor function in VS-WWH; after adjusting for sCD163 and sCD14 in multivariable regressions, higher KT ratio remained significantly associated with impaired fine motor function in VS-WWH only (standardized β = -0.29, P < 0.05). IDO activation was not associated with cognition in WWoH.

CONCLUSIONS

IDO activation (K:T) was associated with worse fine motor control in VS-WWH independent of measured systemic inflammation. Further studies investigating biological mechanisms linking IDO activation to fine motor function among VS-WWH are warranted.

Overamped: Stimulant Use and HIV Pathogenesis

PURPOSE OF REVIEW

In the era of HIV treatment as prevention (TasP), more clarity is needed regarding whether people with HIV who use stimulants (i.e., methamphetamine, powder cocaine, and crack cocaine) display elevated HIV viral load and greater immune dysregulation.

RECENT FINDINGS

Although rates of viral suppression have improved in the TasP era, stimulant use was independently associated with elevated viral load in 23 of 28 studies included in our review. In the 12 studies examining other HIV disease markers, there was preliminary evidence for stimulant-associated alterations in gut-immune dysfunction and cellular immunity despite effective HIV treatment. Studies generally focused on documenting the direct associations of stimulant use with biomarkers of HIV pathogenesis without placing these in the context of social determinants of health. Stimulant use is a key barrier to optimizing the effectiveness of TasP. Elucidating the microbiome-gut-brain axis pathways whereby stimulants alter neuroimmune functioning could identify viable targets for pharmacotherapies for stimulant use disorders. Examining interpersonal, neighborhood, and structural determinants that could modify the associations of stimulant use with biomarkers of HIV pathogenesis is critical to guiding the development of comprehensive, multi-level interventions.

HIV-1-Host Interaction in Gut-Associated Lymphoid Tissue (GALT): Effects on Local Environment and Comorbidities

HIV-1 replication in the gastrointestinal (GI) tract causes severe CD4+ T-cell depletion and disruption of the protective epithelial barrier in the intestinal mucosa, causing microbial translocation, the main driver of inflammation and immune activation, even in people living with HIV (PLWH) taking antiretroviral drug therapy. The higher levels of HIV DNA in the gut compared to the blood highlight the importance of the gut as a viral reservoir. CD4+ T-cell subsets in the gut differ in phenotypic characteristics and differentiation status from the ones in other tissues or in peripheral blood, and little is still known about the mechanisms by which the persistence of HIV is maintained at this anatomical site. This review aims to describe the interaction with key subsets of CD4+ T cells in the intestinal mucosa targeted by HIV-1 and the role of gut microbiome and its metabolites in HIV-associated systemic inflammation and immune activation that are crucial in the pathogenesis of HIV infection and related comorbidities.

The Interaction of HIV With Mental Health in the Modern Antiretroviral Therapy Era

ABSTRACT

People with HIV (PWH) receiving effective antiretroviral therapy (ART) continue to display residual immune dysregulation that amplifies the risk for neuropsychiatric comorbidities. At the same time, PWH commonly experience intersectional stigma and other psychosocial stressors that are linked to neuroendocrine stress responses, potentiate residual immune dysregulation, and alter other biobehavioral processes relevant to health outcomes. This special issue of Psychosomatic Medicine seeks to advance our understanding of the intersection of HIV with mental health in the modern ART era. Several articles cover topics related to the prevalence and treatment of psychiatric comorbidities among PWH such as depression, suicidality, and substance use disorders. Other articles delineate biobehavioral mechanisms relevant to mental health in PWH such as inflammation, immune activation, neuroendocrine signaling, cellular aging, the microbiome-gut-brain axis, and neurobehavioral processes. Collectively, the articles in this special issue highlight the continued importance of biobehavioral and neurobehavioral mental health research in the modern ART era.