Inflammation in HIV infection is predictive of non-AIDS morbidity and death, higher set point plasma virus load and virus acquisition; thus, therapeutic agents are in development to reduce its causes and consequences. However, inflammation may simultaneously confer both detrimental and beneficial effects. This dichotomy is particularly applicable to type I interferons (IFN-I) which, while contributing to innate control of infection, also provide target cells for the virus during acute infection, impair CD4 T-cell recovery, and are associated with disease progression. Here we manipulated IFN-I signalling in rhesus macaques (Macaca mulatta) during simian immunodeficiency virus (SIV) transmission and acute infection with two complementary in vivo interventions. We show that blockade of the IFN-I receptor caused reduced antiviral gene expression, increased SIV reservoir size and accelerated CD4 T-cell depletion with progression to AIDS despite decreased T-cell activation. In contrast, IFN-α2a administration initially upregulated expression of antiviral genes and prevented systemic infection. However, continued IFN-α2a treatment induced IFN-I desensitization and decreased antiviral gene expression, enabling infection with increased SIV reservoir size and accelerated CD4 T-cell loss. Thus, the timing of IFN-induced innate responses in acute SIV infection profoundly affects overall disease course and outweighs the detrimental consequences of increased immune activation. Yet, the clinical consequences of manipulation of IFN signalling are difficult to predict in vivo and therapeutic interventions in human studies should be approached with caution.
[Show abstract][Hide abstract] ABSTRACT: Type I interferons (IFNs), including various IFN-α isoforms and IFN-β, are a family of homologous, multifunctional cytokines. IFNs activate different cellular responses by binding to a common receptor that consists of two subunits, IFNAR1 and IFNAR2. In addition to stimulating antiviral responses, they also inhibit cell proliferation and modulate other immune responses. We characterized various IFNs, including a mutant IFN-α2 (IFN-1ant) that bound tightly to IFNAR2 but had markedly reduced binding to IFNAR1. Whereas IFN-1ant stimulated antiviral activity in a range of cell lines, it failed to elicit immunomodulatory and antiproliferative activities. The antiviral activities of the various IFNs tested depended on a set of IFN-sensitive genes (the "robust" genes) that were controlled by canonical IFN response elements and responded at low concentrations of IFNs. Conversely, these elements were not found in the promoters of genes required for the antiproliferative responses of IFNs (the "tunable" genes). The extent of expression of tunable genes was cell type-specific and correlated with the magnitude of the antiproliferative effects of the various IFNs. Although IFN-1ant induced the expression of robust genes similarly in five different cell lines, its antiviral activity was virus- and cell type-specific. Our findings suggest that IFN-1ant may be a therapeutic candidate for the treatment of specific viral infections without inducing the immunomodulatory and antiproliferative functions of wild-type IFN.
[Show abstract][Hide abstract] ABSTRACT: IFNβ is a common therapeutic option to treat multiple sclerosis (MS). It is unique amongst the family of type I IFNs in that it binds to the interferon receptors with high affinity, conferring exceptional biological properties. We have previously reported the generation of an interferon superagonist (dubbed YNSα8) that is built on the backbone of a low affinity IFNα, but modified to exhibit higher receptor affinity than even for IFNβ. Here, YNSα8 was fused with a 600-residue hydrophilic, unstructured N-terminal polypeptide chain comprising Proline, Alanine and Serine (PAS) in order to prolong its plasma half-life via "PASylation". PAS-YNSα8 exhibited a 10-fold increased half-life in both pharmacodynamic and pharmacokinetic assays in a transgenic mouse model harboring the human receptors, notably without any detectable loss in biological potency or bioavailability. This long-life superagonist conferred significantly improved protection from MOG35-55-induced experimental autoimmune encephalomyelitis (EAE) compared to IFNβ, despite being injected with a 4-fold less frequency and at an overall 16-fold lower dosage. These data were corroborated by FACS measurements showing a decrease of CD11b+ve / CD45hi myeloid lineage cells detectable in the central nervous system (CNS), as well as a decrease in IBA+ve cells in spinal cord sections determined by immunohistochemistry for PAS-YNSα8 treated animals. Importantly, PAS-IFNα8 did not induce antibodies upon repeated administration, and its biological efficacy remained unchanged after 21 days of treatment. A striking correlation between increased levels of CD274 (PD-L1) transcripts from spleen-derived CD4+ cells and improved EAE clinical response was observed, indicating that at least in this mouse model of MS, CD274 may serve as a biomarker to predict effectiveness of IFN therapy to treat this complex disease.
[Show abstract][Hide abstract] ABSTRACT: Using whole-blood transcriptional profiling, we investigated differences in the host response to vaccination and challenge in a rhesus macaque AIDS vaccine trial. Samples were collected from animals prior to and after vaccination with live irradiated vaccine cells secreting the modified endoplasmic reticulum chaperone gp96-Ig loaded with simian immunodeficiency virus (SIV) peptides, either alone or in combination with a SIV-gp120 protein boost. Additional samples were collected following multiple low-dose rectal challenge with SIVmac251. Animals in the boosted group had a 73% reduced risk of infection. Surprisingly, few changes in gene expression were observed during the vaccination phase. Focusing on post-challenge comparisons, in particular for protected animals, we identified a host response signature of protection comprised of strong interferon signaling after the first challenge, which then largely abated after further challenges. We also identified a host response signature, comprised of early macrophage-mediated inflammatory responses, in animals with undetectable viral load five days after the first challenge, but which had unusually high viral titers after subsequent challenges. Statistical analysis showed that prime-boost vaccination significantly lowered the probability of infection in a time-consistent manner throughout several challenges. Given that humoral responses in the prime-boost group were highly significant pre-challenge correlates of protection, the strong innate signaling after the first challenge suggests that interferon signaling could possibly enhance vaccine-induced antibody responses and is an important contributor to protection from infection during repeated low-dose exposure to SIV.
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