The innate immune system recognizes nucleic acids during infection or tissue damage; however, the mechanisms of intracellular recognition of DNA have not been fully elucidated. Here we show that intracellular administration of double-stranded B-form DNA (B-DNA) triggered antiviral responses including production of type I interferons and chemokines independently of Toll-like receptors or the helicase RIG-I. B-DNA activated transcription factor IRF3 and the promoter of the gene encoding interferon-beta through a signaling pathway that required the kinases TBK1 and IKKi, whereas there was substantial activation of transcription factor NF-kappaB independent of both TBK and IKKi. IPS-1, an adaptor molecule linking RIG-I and TBK1, was involved in B-DNA-induced activation of interferon-beta and NF-kappaB. B-DNA signaling by this pathway conferred resistance to viral infection in a way dependent on both TBK1 and IKKi. These results suggest that both TBK1 and IKKi are required for innate immune activation by B-DNA, which might be important in antiviral innate immunity and other DNA-associated immune disorders.

Modified vaccinia Ankara (MVA), a highly attenuated vaccinia virus strain that has been safety tested in humans, was evaluated for use as an expression vector. MVA has multiple genomic deletions and is severely host cell restricted: it grows well in avian cells but is unable to multiply in human and most other mammalian cells tested. Nevertheless, we found that replication of viral DNA appeared normal and that both early and late viral proteins were synthesized in human cells. Proteolytic processing of viral structural proteins was inhibited, however, and only immature virus particles were detected by electron microscopy. We constructed an insertion plasmid with the Eschenchia coli lacZ gene under the control of the vaccinia virus late promoter P11, flanked by sequences of MVA DNA, to allow homologous recombination at the site of a naturally occurring 3500-base-pair deletion within the MVA genome. MVA recombinants were isolated and propagated in permissive avian cells and shown to express the enzyme 3-galactosidase upon infection of nonpermissive human cells. The amount of enzyme made was similar to that produced by a recombinant of vaccinia virus strain Western Reserve, which also had the lacZ gene under control of the P11 promoter, but multiplied to high titers. Since recombinant gene expression is unimpaired in nonpermissive human cells, MVA may serve as a highly efficient and exceptionally safe vector.The eradication of smallpox was achieved through immunization with live vaccinia virus (1). Presently, vaccinia virus is used extensively as a gene expression vector and is under evaluation as a recombinant vaccine (2). Because vaccinia virus is infectious for humans, its use in the laboratory has been affected by safety concerns and regulations (3, 4). For general vector applications, health risks would be lessened by the adoption of a highly attenuated vaccinia virus strain. Several such strains were developed for use as safer smallpox vaccines (1). We chose to examine the potential of the modified vaccinia Ankara (MVA) strain as an expression vector because of its extreme attenuation. MVA was derived from vaccinia virus strain Ankara, referred to here as the wild-type virus (WT), by over 570 serial passages in chicken embryo fibroblast cells (CEF) (5). The resulting MVA strain lost the capacity to productively infect mammalian cells and suffered six major deletions of DNA totaling 31,000 base pairs (bp), including at least two host-range genes (refs. 6 and 7; G.S., unpublished data). When tested in a variety ofanimal species, MVA was proven to be avirulent even in immunosuppressed animals. Most importantly, there is clinical experience using MVA for primary vaccination of over 120,000 humans against smallpox. During extensive field studies, including high risk patients, no side effects were associated with the use of the MVA vaccine (5,8,9 10847The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordanc...

We previously demonstrated that a specialized subset of immature myeloid cells migrate to lymphoid organs as a result of tumor growth or immune stress, where they suppress B and T cell responses to Ags. Although NO was required for suppression of mitogen activation of T cells by myeloid suppressor cells (MSC), it was not required for suppression of allogenic responses. In this study, we describe a novel mechanism used by MSC to block T cell proliferation and CTL generation in response to alloantigen, which is mediated by the enzyme arginase 1 (Arg1). We show that Arg1 increases superoxide production in myeloid cells through a pathway that likely utilizes the reductase domain of inducible NO synthase (iNOS), and that superoxide is required for Arg1-dependent suppression of T cell function. Arg1 is induced by IL-4 in freshly isolated MSC or cloned MSC lines, and is therefore up-regulated by activated Th2, but not Th1, cells. In contrast, iNOS is induced by IFN-γ and Th1 cells. Because Arg1 and iNOS share l-arginine as a common substrate, our results indicate that l-arginine metabolism in myeloid cells is a potential target for selective intervention in reversing myeloid-induced dysfunction in tumor-bearing hosts.

Coronaviruses in the Middle East Middle East respiratory syndrome coronavirus (MERS-CoV) causes severe acute respiratory illness and kills about a third of people infected. The virus is common in dromedary camels, which can be a source of human infections. In a survey for MERSCoV in over 1300 Saudi Arabian camels, Sabir et al. found that dromedaries share three coronavirus species with humans. Diverse MERS lineages in camels have caused human infections, which suggests that transfer among host species occurs quite easily. Haagmans et al. made a MERS-CoV vaccine for use in camels, using poxvirus as a vehicle. The vaccine significantly reduced virus excretion, which should help reduce the potential for transmission to humans, and conferred cross-immunity to camelpox infections. Science , this issue p. 81 , p. 77