Abstract
We have reported that short-term stimulation of primary human monocyte-derived macrophages (MDM) with interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α), i.e. M1 polarization, leads to a significant containment of virus replication. Here we show that M1-MDM restimulation with these cytokines 7 days after infection (M12 MDM) promoted an increased restriction of HIV-1 replication characterized by very low levels of virus production near to undetectable levels. In comparison to control and M1-MDM that were not restimulated, M12 MDM showed a stronger reduction of both total and integrated HIV DNA as well as of viral mRNA expression. M12 MDM were characterized by an upregulated expression of restriction factors acting at the level of reverse transcription (RT), including apolipoprotein B mRNA editing enzyme, catalytic polypeptide-like 3A (APOBEC3A) and APOBEC3G, but not SAM domain and HD domain-containing protein 1 (SAMHD1). M12 MDM also showed an increased expression of Class II Transactivator (CIITA) and Tripartite Motif22 (TRIM22), two negative regulators of proviral transcription, whereas expression and phosphorylation of transcriptional inducers of HIV-1, such as nuclear factor kB (NF-kB) and signal transducer and activator of transcription 1 (STAT1), were not impaired in these cells. The almost quiescent state of the infection in M12 MDM was promptly reversed by coculture with mitogen-stimulated leukocytes or cell incubation with their filtered culture supernatant. M12 MDM harbored replication-competent HIV-1 as virus spreading following cell stimulation was fully prevented by the RT inhibitor lamivudine/3TC. Selective reactivation of proviral expression in M12 MDM, but not in control or in M1-MDM that were not restimulated, was confirmed in cells infected with single round Vesicular Stomatitis Virus-G-pseudotyped HIV-1. Thus, M12 MDM represent an in vitro model of reversible, almost quiescent HIV-1 infection of primary human macrophages that could be further exploited for “Cure” related investigations.
Highlights
We have reported that short-term stimulation of primary human monocyte-derived macrophages (MDM) with interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α), i.e. M1 polarization, leads to a significant containment of virus replication
Having described that M1 polarization of primary human MDM leads to a reduction of human immunodeficiency virus type-1 (HIV-1) replicative capacity[21,22], we have investigated the consequences of reexposing M1-MDM that were infected 7 days earlier by the R5 HIV-1Bal strain to the same cytokines (Fig. 1A), an experimental condition further referred to as “M12 MDM”
We have further investigated our previous observation that short-term stimulation of human MDM with pro-inflammatory cytokines (IFN-γ and TNF-α), i.e. M1 polarization, before infection induces a partial restriction of HIV-1 replication
Summary
We have reported that short-term stimulation of primary human monocyte-derived macrophages (MDM) with interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α), i.e. M1 polarization, leads to a significant containment of virus replication. No depletion of circulating monocytes or tissue-associated macrophages is usually seen in infected individuals whereas in vitro infection of primary human monocyte-derived macrophages (MDM) does not lead to a significant cytopathicity and cell death[8,9] Both in vivo and in vitro macrophage infections are characterized by the active accumulation of mature virions in subcellular compartments generated as invaginations of the plasma membrane nowadays referred to as virus-containing compartments (VCC)[9,10], a feature not observed in CD4+ T cells. The hypothesis that, in addition to CD4+ T cells, macrophages could be prominent contributors to the cART-resistant reservoir of infectious proviruses has been further supported by the recent evidence that mice with severe combined immunodeficiency (SCID) reconstituted with human myeloid cells in the absence of CD4+ T cells can undergo both acute and chronic HIV-1 infection with establishment of an inducible HIV-1 reservoir, at least in some animals[20]
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