Butyrate administration is not sufficient to improve immune reconstitution in antiretroviral-treated SIV-infected macaques

Dual role for microbial short-chain fatty acids in modifying SIV disease trajectory following anti-α4β7 antibody administration

BACKGROUND

Human Immunodeficiency Virus (HIV)/Simian Immunodeficiency Virus (SIV) infection is associated with significant gut damage, similar to that observed in patients with inflammatory bowel disease (IBD). This pathology includes loss of epithelial integrity, microbial translocation, dysbiosis, and resultant chronic immune activation. Additionally, the levels of all-trans-retinoic acid (atRA) are dramatically attenuated. Data on the therapeutic use of anti-α4β7 antibodies has shown promise in patients with ulcerative colitis and Crohn's disease. Recent evidence has suggested that the microbiome and short-chain fatty acid (SCFA) metabolites it generates may be critical for anti-α4β7 efficacy and maintaining intestinal homeostasis.

MATERIALS AND METHODS

To determine whether the microbiome contributes to gut homeostasis after anti-α4β7 antibody administered to SIV-infected rhesus macaques, faecal SCFA concentrations were determined, 16S rRNA sequencing was performed, plasma viral loads were determined, plasma retinoids were measured longitudinally, and gut retinoid synthesis/response gene expression was quantified.

RESULTS

Our results suggest that anti-α4β7 antibody facilitates the return of retinoid metabolism to baseline levels after SIV infection. Furthermore, faecal SCFAs were shown to be associated with retinoid synthesis gene expression and rebound viral loads after therapy interruption.

CONCLUSIONS

Taken together, these data demonstrate the therapeutic advantages of anti-α4β7 antibody administration during HIV/SIV infection and that the efficacy of anti-α4β7 antibody may depend on microbiome composition and SCFA generation.

Regulation of Immune Homeostasis, Inflammation, and HIV Persistence by the Microbiome, Short-Chain Fatty Acids, and Bile Acids

Despite antiretroviral therapy (ART), people living with human immunodeficiency virus (HIV) (PLWH) continue to experience chronic inflammation and immune dysfunction, which drives the persistence of latent HIV and prevalence of clinical comorbidities. Elucidating the mechanisms that lead to suboptimal immunity is necessary for developing therapeutics that improve the quality of life of PLWH. Although previous studies have found associations between gut dysbiosis and immune dysfunction, the cellular/molecular cascades implicated in the manifestation of aberrant immune responses downstream of microbial perturbations in PLWH are incompletely understood. Recent literature has highlighted that two abundant metabolite families, short-chain fatty acids (SCFAs) and bile acids (BAs), play a crucial role in shaping immunity. These metabolites can be produced and/or modified by bacterial species that make up the gut microbiota and may serve as the causal link between changes to the gut microbiome, chronic inflammation, and immune dysfunction in PLWH. In this review, we discuss our current understanding of the role of the microbiome on HIV acquisition and latent HIV persistence despite ART. Further, we describe cellular/molecular cascades downstream of SCFAs and BAs that drive innate or adaptive immune responses responsible for promoting latent HIV persistence in PLWH. This knowledge can be used to advance HIV cure efforts.

2-Hydroxypropyl-β-Cyclodextrin Treatment Induces Modest Immune Activation in Healthy Rhesus Macaques

Experimental simian immunodeficiency virus (SIV) infection of Asian macaques is an excellent model for HIV disease progression and therapeutic development. Recent coformulations of nucleoside analogs and an integrase inhibitor have been used for parenteral antiretroviral (ARV) administration in SIV-infected macaques, successfully resulting in undetectable plasma SIV RNA. In a cohort of SIVmac239-infected macaques, we recently observed that administration of coformulated ARVs resulted in an unexpected increase in plasma levels of soluble CD14 (sCD14), associated with stimulation of myeloid cells. We hypothesized that the coformulation solubilizing agent Kleptose (2-hydroxypropyl-β-cyclodextrin [HPβCD]) may induce inflammation with myeloid cell activation and the release of sCD14. Herein, we stimulated peripheral blood mononuclear cells (PBMCs) from healthy macaques with HPβCD from different commercial sources and evaluated inflammatory cytokine production in vitro. Treatment of PBMCs resulted in increased sCD14 release and myeloid cell interleukin-1β (IL-1β) production-with stimulation varying significantly by HPβCD source-and destabilized lymphocyte CCR5 surface expression. We further treated healthy macaques with Kleptose alone. In vivo, we observed modestly increased myeloid cell activation in response to Kleptose treatment without significant perturbation of the immunological transcriptome or epigenome. Our results demonstrate a need for vehicle-only controls and highlight immunological perturbations that can occur when using HPβCD in pharmaceutical coformulations. IMPORTANCE SIV infection of nonhuman primates is the principal model system for assessing HIV disease progression and therapeutic development. HPβCD has recently been incorporated as a solubilizing agent in coformulations of ARVs in SIV-infected nonhuman primates. Although HPβCD has historically been considered inert, recent findings suggest that HPβCD may contribute to inflammation. Herein, we investigate the contribution of HPβCD to healthy macaque inflammation in vitro and in vivo. We observe that HPβCD causes an induction of sCD14 and IL-1β from myeloid cells in vitro and demonstrate that HPβCD stimulatory capacity varies by commercial source. In vivo, we observe modest myeloid cell activation in blood and bronchoalveolar lavage specimens absent systemic immune activation. From our findings, it is unclear whether HPβCD stimulation may improve or diminish immune reconstitution in ARV-treated lentiviral infections. Our results demonstrate a need for vehicle-only controls and highlight immunological perturbations that can occur when using HPβCD in pharmaceutical coformulations.