The Binding Subunit of Pertussis Toxin Inhibits HIV Replication in Human Macrophages and Virus Expression in Chronically Infected Promonocytic U1 Cells

Abstract

We have recently shown that the binding subunit of pertussis toxin (PTX-B) inhibits the entry and replication of macrophage-tropic (R5) HIV-1 strains in activated primary T lymphocytes. Furthermore, PTX-B suppressed the replication of T cell-tropic (X4) viruses at a postentry level in the same cells. In this study we demonstrate that PTX-B profoundly impairs entry and replication of the HIV-1ADA (R5), as well as of HIV pseudotyped with either murine leukemia virus or vesicular stomatitis virus envelopes, in primary monocyte-derived macrophages. In addition, PTX-B strongly inhibited X4 HIV-1 replication in U937 promonocytic cells and virus expression in the U937-derived chronically infected U1 cell line stimulated with cytokines such as TNF-α and IL-6. Of interest, TNF-α-mediated activation of the cellular transcription factor NF-κB was unaffected by PTX-B. Therefore, PTX-B may represent a novel and potent inhibitor of HIV-1 replication to be tested for efficacy in infected individuals. In support of this proposition, a genetically modified mutant of PTX (PT-9K/129G), which is safely administered for prevention of Bordetella pertussis infection, showed an in vitro anti-HIV profile superimposable to that of PTX-B.

Inhibition of intra‐ and extra‐cellular Tat function and HIV expression by pertussis toxin B‐oligomer

“…It interferes with entry of R5-dependent HIV-1 by uncoupling R5 from CD4 [20]. Also, it interferes with post-entry events in the HIV life cycle [20,22]. In this regard, its anti-HIV effect has been linked to inhibition of NF-kB activation [23].…”

“…Since PTX-B does not prevent cellular uptake of extracellular Tat, it is conceivable that it may not curtail its antigenic expression and the consequent adaptive immune response. Of interest is the fact that all the PTX-B inhibitory effects, including the anti-HIV activity [22], have been fully reproduced with the genetically modified holotoxin PTX, PT-9K/129G [22], approved for human use as a component of a vaccine against B. pertussis infection [33]. Accordingly, PT-9K/ 129G retains its "pleiotropic" capacity to block the transactivating activity of Tat either when it acts as an exogenous molecule or when it is endogenously produced by the cell, as occurs in HL3T1 and U1 cells, respectively.…”

“…The genetically modified holotoxin PTX, PT-9K/129G [22] was approved for human use as a component of a vaccine against B. pertussis infection [33]. We then evaluated its effect on Tat-transactivating activity.…”

“…U1 cells were transfected with the plasmid pcDNA1/Tat using the hypotonic DEAE-dextran method [22]. Viral expression was measured by either Mg 2+ -dependent HIV-1 RT activity [22] or levels of expression of Gag p24 [44] in cell culture supernatants.…”

“…PTX-B inhibits entry of R5-dependent HIV-1 in T cells and macrophages and post-entry steps of both R5-and X4-dependent HIV-1 life cycle in primary T cells [20,21], monocyte-derived macrophages (MDM) [22], as well as viral expression in chronically infected MDM [21,22] and cytokine-stimulated U1 cells [22,23]. PTX-B also inhibits Tat-driven transactivation in T lymphoid Jurkat cells [21], and stimulates anti-HIV specific cytotoxic T lymphocyte responses [24].…”