(A) In vitro TNF-α treatment decreased SLBP expression. CEM cells were treated with TNF-α (30 ng/ml). At 24 and 48 hours after treatment, SLBP protein and RNA levels were reduced by approximately 40% as quantified by Western blot (left panel) and RT-PCR (right panel), respectively. ACTB was used as the loading control (n = 3 biologic replicates). Student’s t test; *P < 0.05; error bars represent ± SD. (B) Treatment of CEM cells by TNF-α with subsequent HIV-1 infection led to significantly higher (~4-fold) levels of viral unspliced RNA in comparison with untreated cells or those simultaneously treated with an SLBP expression vector (TNF-α+SLBP). Note that superphysiologic expression of SLBP significantly decreased the HIV-1 enabling activity of TNF-α by 30% (n = 3 biologic replicates). One-way ANOVA with post hoc Tukey’s test; *P < 0.05, **P < 0.01; error bars represent ± SD. (C) Plasma levels of TNF-α in the original cohorts (n = 27) were quantified by ELISA and were significantly elevated in the high-VL group. Mann-Whitney test; *P < 0.05; error bars represent ± SEM. (D) The number of study subjects was expanded to include HIV-1–uninfected individuals (n = 23), those on suppressive antiretroviral therapy (ART) (n = 20), and additional individuals with VL less than 2,000 (n = 21) and VL greater than 10,000 (n = 26). Intracellular SLBP expression was approximately 40% higher (*P < 0.05) in the low-VL versus the high-VL group. SLBP protein levels in PBMCs were quantified by ELISA for each subject. One-way ANOVA with post hoc Tukey’s test; *P < 0.05; error bars represent ± SEM. (E) A proposed TNF-α/SLBP circuit that impacts HIV-1 integration and transcription. TNF-α induced by proinflammatory stimuli decreases cellular SLBP levels, leading to enhanced HIV-1 integration and proviral transcription via an SLBP-mediated increase in viral and HMGA1 promoter accessibility.