Certain RNA molecules, called ribozymes, possess enzymatic, self-cleaving activity. The cleavage reaction is catalytic and no energy source is required. Ribozymes of the "hammerhead" motif were identified in plant RNA pathogens. These ribozymes possess unique secondary (and possibly tertiary) structures critical for their cleavage ability. The present study shows precise cleavage of human immunodeficiency virus type 1 (HIV-1) sequences in a cell-free system by hammerhead ribozymes. In addition to the cell-free studies, human cells stably expressing a hammerhead ribozyme targeted to HIV-1 gag transcripts have been constructed. When these cells were challenged with HIV-1, a substantial reduction in the level of HIV-1 gag RNA relative to that in nonribozyme-expressing cells, was observed. The reduction in gag RNA was reflected in a reduction in antigen p24 levels. These results suggest the feasibility of developing ribozymes as therapeutic agents against human pathogens such as HIV-1.

Small interfering RNAs (siRNA) are potent reagents for directed post-transcriptional gene silencing and a major new genetic tool for investigating mammalian cells. When synthetic siRNAs are used for gene silencing, the costs can be substantial because of variations in siRNA efficacies. An alternative to chemically synthesized siRNAs are siRNAs produced by bacteriophage T7 RNA polymerase. We found that siRNAs synthesized from the T7 RNA polymerase system can trigger a potent induction of interferon alpha and beta in a variety of cell lines. Surprisingly, we also found very potent induction of interferon alpha and beta by short single-stranded RNAs (ssRNAs) transcribed with T3, T7 and Sp6 RNA polymerases. Analyses of the potential mediators of this response revealed that the initiating 5' triphosphate is required for interferon induction. We describe here an improved method for T7 siRNA synthesis that alleviates the interferon response while maintaining full efficacy of the siRNAs.

STING is an endoplasmic reticulum (ER) signaling adaptor that is essential for the type I Interferon response to DNA pathogens. Aberrant activation of STING is linked to the pathology of autoimmune and autoinflammatory diseases. The rate-limiting step for the activation of STING is its translocation from the ER to the ER–Golgi intermediate compartment. Here we found that deficiency in the Ca 2+ sensor STIM1 caused spontaneous activation of STING and enhanced expression of type I interferons under resting conditions in mice and a patient suffering from combined immunodeficiency. Mechanistically, STIM1 associated with STING to retain it in the ER membrane, and co-expression of full-length or a STING-interacting fragment of STIM1 suppressed the function of dominant STING mutants that cause autoinflammatory diseases. Furthermore, deficiency in STIM1 strongly enhanced the expression of type I interferons after viral infection and prevented the lethality of infection with a DNA virus in vivo. This work delineates a STIM1–STING circuit that maintains the resting state of the STING pathway.

The gut commensal Bacteroides fragilis or its capsular polysaccharide A (PSA) can prevent various peripheral and CNS sterile inflammatory disorders. Fatal herpes simplex encephalitis (HSE) results from immune pathology caused by uncontrolled invasion of the brainstem by inflammatory monocytes and neutrophils. Here we assess the immunomodulatory potential of PSA in HSE by infecting PSA or PBS treated 129S6 mice with HSV1, followed by delayed Acyclovir (ACV) treatment as often occurs in the clinical setting. Only PSA-treated mice survived, with dramatically reduced brainstem inflammation and altered cytokine and chemokine profiles. Importantly, PSA binding by B cells is essential for induction of regulatory CD4 + and CD8 + T cells secreting IL-10 to control innate inflammatory responses, consistent with the lack of PSA mediated protection in Rag −/− , B cell- and IL-10-deficient mice. Our data reveal the translational potential of PSA as an immunomodulatory symbiosis factor to orchestrate robust protective anti-inflammatory responses during viral infections.

Key Points miR-142 is an essential regulator of lymphocyte ontogenesis and is required for the generation of humoral and cellular immunity in mice. miR-142-3p regulates B-cell homeostasis by controlling expression of BAFF-R.

Herpes simplex virus type 1 (HSV-1) infections are widespread in developed countries, with estimates of seropositivity exceeding 50% (54). Primary infections in immunocompetent individuals are usually mild or even asymptomatic and result in lifelong latent infections in sensory ganglia and the central nervous system (CNS) (5). Reactivated HSV-1 can result in recurrent diseases of mucous membranes (e.g., gingivostomatitis and herpes labialis) and herpes keratitis, an immunopathological disease that is a leading cause of blindness (39). Also, HSV-1 is the most common cause of fatal, sporadic encephalitis in immunocompetent individuals (40, 56). Improvements in diagnosis and antiviral drug treatment have dramatically reduced the morbidity and mortality of HSV-1 encephalitis (HSE) (55), although some patients fail to respond or subsequently suffer neurological relapses after completing a standard treatment course (18,55).Clinical and animal model studies have clearly demonstrated the importance of genetic makeup in resistance to a broad range of infectious agents (15,41). In regard to HSV-1, C57BL/6 (B6) and related B10 mouse strains are resistant, while other strains, such A/J, BALB/c, 129S6 (129), and DBA/ 2J, are susceptible to fatal infections (21,23,25). In these animal models, mortality results from CNS infection. In prior studies, we defined the herpes resistance locus (Hrl) on mouse chromosome 6 as a major determinant of resistance (22, 25); however, ongoing studies indicate that resistance to HSE is genetically very complex, involving multiple interacting loci, with tumor necrosis factor playing a critical role (26) (unpublished results). The mechanism by which HSV-1 CNS infection causes death has not been defined. Counterintuitively, necropsy virus titers of nervous system tissues do not correlate with mouse resistance or susceptibility genotype (25,26). These and other observations have led to the suggestion that variation of the host inflammatory response may play a major role in determining HSV fatality. Intense inflammatory responses in CNS tissues in a mouse model of HSE have been reported, with tumor necrosis factor and macrophage chemoattractant protein 1 being expressed prominently (43). Also, in vitro and in vivo studies have shown that human and mouse microglia nonproductively infected with HSV-1 express a variety of proinflammatory cytokines and chemokines, consistent with their involvement in

HSV-1 is the leading cause of sporadic encephalitis in humans. HSV infection of susceptible 129S6 mice results in fatal encephalitis (HSE) caused by massive inflammatory brainstem lesions comprising monocytes and neutrophils. During infection with pathogenic microorganisms or autoimmune disease, IgGs induce proinflammatory responses and recruit innate effector cells. In contrast, high dose intravenous immunoglobulins (IVIG) are an effective treatment for various autoimmune and inflammatory diseases because of potent anti-inflammatory effects stemming in part from sialylated IgGs (sIgG) present at 1–3% in IVIG. We investigated the ability of IVIG to prevent fatal HSE when given 24 h post infection. We discovered a novel anti-inflammatory pathway mediated by low-dose IVIG that protected 129S6 mice from fatal HSE by modulating CNS inflammation independently of HSV specific antibodies or sIgG. IVIG suppressed CNS infiltration by pathogenic CD11b+ Ly6Chigh monocytes and inhibited their spontaneous degranulation in vitro. FcγRIIb expression was required for IVIG mediated suppression of CNS infiltration by CD45+ Ly6Clow monocytes but not for inhibiting development of Ly6Chigh monocytes. IVIG increased accumulation of T cells in the CNS, and the non-sIgG fraction induced a dramatic expansion of FoxP3+ CD4+ T regulatory cells (Tregs) and FoxP3− ICOS+ CD4+ T cells in peripheral lymphoid organs. Tregs purified from HSV infected IVIG treated, but not control, mice protected adoptively transferred mice from fatal HSE. IL-10, produced by the ICOS+ CD4+ T cells that accumulated in the CNS of IVIG treated, but not control mice, was essential for induction of protective anti-inflammatory responses. Our results significantly enhance understanding of IVIG's anti-inflammatory and immunomodulatory capabilities by revealing a novel sIgG independent anti-inflammatory pathway responsible for induction of regulatory T cells that secrete the immunosuppressive cytokine IL-10 and further reveal the therapeutic potential of IVIG for treating viral induced inflammatory diseases.

RNA interference is a powerful tool for target-specific knockdown of gene expression. The triggers for this process are duplex small interfering RNAs (siRNAs) of 21-25 nt with 2-bp 3' overhangs produced in cells by the RNase III family member Dicer. We have observed that short RNAs that are long enough to serve as Dicer substrates (D-siRNA) can often evoke more potent RNA interference than the corresponding 21-nt siRNAs; this is probably a consequence of the physical handoff of the Dicer-produced siRNAs to the RNA-induced silencing complex. Here we describe the design parameters for D-siRNAs and a protocol for in vitro and in vivo intraperitoneal delivery of D-siRNAs and siRNAs to macrophages. siRNA delivery and transfection and analysis of macrophages in vivo can be accomplished within 36 h.