Interferon-α Subtypes in an Ex Vivo Model of Acute HIV-1 Infection: Expression, Potency and Effector Mechanisms

Abstract

HIV-1 is transmitted primarily across mucosal surfaces and rapidly spreads within the intestinal mucosa during acute infection. The type I interferons (IFNs) likely serve as a first line of defense, but the relative expression and antiviral properties of the 12 IFNα subtypes against HIV-1 infection of mucosal tissues remain unknown. Here, we evaluated the expression of all IFNα subtypes in HIV-1-exposed plasmacytoid dendritic cells by next-generation sequencing. We then determined the relative antiviral potency of each IFNα subtype ex vivo using the human intestinal Lamina Propria Aggregate Culture model. IFNα subtype transcripts from the centromeric half of the IFNA gene complex were highly expressed in pDCs following HIV-1 exposure. There was an inverse relationship between IFNA subtype expression and potency. IFNα8, IFNα6 and IFNα14 were the most potent in restricting HIV-1 infection. IFNα2, the clinically-approved subtype, and IFNα1 were both highly expressed but exhibited relatively weak antiviral activity. The relative potencies correlated with binding affinity to the type I IFN receptor and the induction levels of HIV-1 restriction factors Mx2 and Tetherin/BST-2 but not APOBEC3G, F and D. However, despite the lack of APOBEC3 transcriptional induction, the higher relative potency of IFNα8 and IFNα14 correlated with stronger inhibition of virion infectivity, which is linked to deaminase-independent APOBEC3 restriction activity. By contrast, both potent (IFNα8) and weak (IFNα1) subtypes significantly induced HIV-1 GG-to-AG hypermutation. The results unravel non-redundant functions of the IFNα subtypes against HIV-1 infection, with strong implications for HIV-1 mucosal immunity, viral evolution and IFNα-based functional cure strategies.

Interferon Alpha Subtype-Specific Suppression of HIV-1 InfectionIn Vivo

“…Human gut LPMCs from 6 different donors (each in duplicate) were obtained following tissue disaggregation and collagenase digestion (43,44). The LPMCs were spinoculated with HIV-1 BaL at 10 ng p24/10 6 cells (AIDS Research Reagent Program; catalog number 4984) and resuspended in different IFN-␣2 or IFN-␣14 concentrations, and the percentage of p24 ϩ cells in the CD3 ϩ CD8 Ϫ cell fraction was evaluated at 4 days postinfection (dpi) by flow cytometry, as previously described (14). The recombinant IFN-␣2 and IFN-␣14 proteins were purchased from PBL Assay Science (catalog number 11002-1).…”

“…A recent in vitro study using human gut LPMCs showed that the antiviral effects of different IFN-␣ subtypes on HIV-1 suppression were not equal (14). To assess and confirm the best IFN-␣ subtypes to follow up with experiments in humanized mice, we conducted an in vitro screening assay.…”

“…Furthermore, murine herpesvirus or influenza virus infections were controlled by different subtypes than those inhibiting FV (9)(10)(11)(12)(13). Recent in vitro work demonstrated not only differential relative expression of IFN-␣ subtypes in human plasmacytoid dendritic cells (pDCs) after human immunodeficiency virus type 1 (HIV-1) exposure, but also variable HIV-1 antiviral potencies of IFN-␣ subtypes in gut lamina propria mononuclear cell (LPMC) cultures (14). Thus, effective antiviral therapy with IFN-␣ is quite specific to both the IFN-␣ subtype and the virus.…”

“…In vitro studies with pDCs, which are the primary producers of IFN-␣, indicated that the predominant IFN-␣ subtypes produced by pDCs in response to HIV-1 (IFN-␣1, -2, and -5) have only weak anti-HIV-1 activities (14). Thus, HIV-1 predominantly induces IFN-␣ subtypes that are ineffective against HIV-1 in vitro.…”

“…Thus, HIV-1 predominantly induces IFN-␣ subtypes that are ineffective against HIV-1 in vitro. Analyses of IFN-␣ subtype profiles from peripheral blood mononuclear cells (PBMCs) collected from HIV-1-infected patients during different stages of disease also revealed that some of the subtypes shown to be most potent against HIV-1 in vitro are not produced until latestage disease, when the immune system may be too damaged to respond effectively (14,19). Thus, it is possible that the IFN-␣ subtypes most protective against HIV-1 are not induced in a timely manner and that therapeutic delivery of a more efficacious subtype(s) may be beneficial.…”