NATURE BIOTECHNOLOGY VOL 18 JUNE 2000 http://biotech.nature.com 585

IN BRIEF

RESEARCH NEWS

Soluble receptor against lupus?

A soluble form of a receptor for a cytokine that activates B cells iseffective for inhibiting the development of autoimmune disease ina mouse model of systemic lupus erythematosus (SLE), accordingto a study recently published in Nature (404, 995–999, 2000). Theresults validate a genomic screening approach for identifying pro-tein ligands and may open a promising avenue to treating humanautoimmune diseases. Researchers at ZymoGenetics (Seattle,WA) first showed that the cytokine (zTNF4), a member of thetumor necrosis factor (TNF) ligand family, causes SLE-like symp-toms in mice when overexpressed. They then identified TACI, areceptor for zTNF4, by screening a cDNA expression library pre-pared from B cells with a labeled form of the cytokine. Reasoningthat the TACI–zTNF4 interaction could be of potential therapeu-tic value, the researchers then set about creating a soluble form ofTACI and tested it in the mouse SLE model. The treatment inhibit-ed the development of proteinuria in the animals and prolongedtheir survival. Although the results are promising, the researchers acknowledge that morework must be done to determine the possible side effects of inhibiting B-cell activation withTACI. “We are currently testing the effects of TACI treatment on the development of a normalimmune system and during a primary and secondary immune response,” says Jane Gross, acompany scientist and lead author on the paper. AD

Surrogate β-cells

New work indicates that the liver can beinduced to serve as a surrogate for the pan-creas, with a little help from the PDX-1 gene.By injecting mice with an adenoviral vectorcontaining the gene encoding PDX-1, a home-odomain protein involved in the developmentand differentiation of pancreatic cells, a groupof researchers from Israel has succeeded inconverting a subpopulation of liver cells to apancreatic β-cell phenotype. Following aden-oviral treatment, about 60% of the mice livercells started synthesizing PDX-1, with a 25-fold increase in insulin expression, 59% ofwhich was fully processed functional protein.In an experimental model of diabetes in whichhyperglycemia was induced by the chemicalstreptozotocin, the researchers found that onlythose mice treated with the PDX-1 gene wereable to survive and ameliorate glucose dysreg-ulation. It is not yet clear whether the surro-gate β-cells can respond normally to fluctua-tions in glucose or whether, like β-cells, theythemselves will become targeted by autoim-mune processes. But according to Axel Kahn, adiabetes researcher at INSERM (Paris), theresults “could constitute a breakthrough in theprospects of therapy for type I diabetes,”

High-affinity TCRs

Using an in vitro evolution technique,researchers at the University of Chicago(Chicago, IL) and the University of Illinois(Urbana, IL) have developed T-cell receptor(TCR) proteins with an extremely high affini-ty for a target peptide–MHC ligand. Besidesdemonstrating that there is no intrinsic struc-tural block to generating high-affinity TCRs,the findings could have implications for avariety of clinical applications. The approach,described in Proc. Natl. Acad. Sci. USA (97,5387–5392, 2000), relies on the surfaceexpression and display of mutant single-chainTCRs in a library of yeast cells. By selectingTCRs that bound to a model nine-residueantigen (QL9) from this pool, the researcherswere able to avoid the selective pressures thatappear to limit TCR affinity in vivo. The teamwas able to isolate TCRs with an affinity forQL9–MHC 100-fold higher than naturallyoccurring TCRs. A soluble form of the high-affinity TCR can detect peptide–MHC com-plexes on antigen-presenting cells, suggestingthat the artificially generated TCRs could tar-get these complexes therapeutically. “I see noreason why one couldn’t perform immuno-histology with these reagents in the same wayone does with monoclonal antibodies,” saysDavid Kranz, senior author on the paper. AD

Vaccinia’s interactions

A comprehensive two-hybrid analysis hasidentified 28 previously unknown interactionsamong the proteins encoded by the vacciniavirus genome (Proc. Natl. Acad. Sci. USA, 97,4879–4884, 2000). Vaccinia has been a usefultool in medicine and biotechnology, from itsearly use as the smallpox vaccine to its currentuses to manufacture recombinant proteinsand as a vector for recombinant vaccinesagainst cancer and infectious disease. Usingthe array-based format developed by StanFields’s laboratory at the University ofWashington in Seattle (Nature, 403, 623–627,2000), Steven McCraith and coworkers havesystematically tested each of the 70,000 possi-ble pairwise combinations of the virus’s 266putative protein-coding genes for the ability tointeract in the two-hybrid assay. Althoughconfirmation of the validity of these new inter-actions will be necessary, several new leadshave been uncovered in the quest to gain a bet-ter understanding of vaccinia replication. Fora subset of proteins, however, neither sequencehomology searches nor two-hybrid analysishas revealed any information as to their func-tion. “Developing the next generation of tech-nologies to approach this type of problem willbe one of the future challenges in the arena ofgenomic analysis,” states McCraith. RF

Cold fusion for eggs

Novel methods of membrane fusion may helpwomen who have fertility problems due toeggs that contain defective cytoplasm. Thetechniques, a new method of mechanicallyinduced membrane fusion in human oocytesand a previously described chemical fusionmethod, were developed by a collaboration ofresearchers from France, Spain, and Italy andessentially involve transferring the nucleus of adefective egg into a donor egg (Hum. Reprod.,15, 1149–1154, 2000). Most cell fusion tech-niques used in mammalian cloning employelectrofusion, which cannot be used forhuman oocytes because it activates them. Inthe current study, the team used a modifiedchemical polyethylene glycol method to essen-tially “glue” together two zona pellucida-freehuman eggs, one of which was enucleated. Italso used a mechanical method performed bymaking a hole in the zona and then manipu-lating the eggs together using a micropipette.

The authors say the intracytoplasmic sperminjection (ICSI) technique “will probably bethe optimal way of fertilizing the reconstruct-ed oocytes.” The technique also has potentialfor use in therapeutic cloning. JG

Shown: Kidney sections; G = glomeruli

Research News Briefs written by Alan Dove,Robert Frederickson, Julie Grisham, andAndrew Marshall.

which currently affects up to 14 million peopleworldwide. The findings are reported in Nat.Med. (6, 568–572, 2000). AM

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