and trade material and utilities forweapons of mass destruction.

This year, the Norval-Young award was jointly won by Michel deGarine-Wichatitsky from CIRAD-EMVT, Montpellier, France with hispaper entitled ‘Assessing infection riskby vectors: spatial and temporal distri-bution of African ticks’ and ReginaldValdez from USDA Animal DiseaseResearch Unit, WA, USA with his paperentitled ‘An in vivo model to investigatelymphocyte-mediated immunity duringacute hemoparasitic infections: use of a

monoclonal antibody to selectively de-plete CD41 T cells from thymecto-mised calves’.

AcknowledgementsThe setting for this 5th biennial conference ofThe Society for Tropical Veterinary Medicinewas the Hilton Resort and Marina; in the hotand steamy atmosphere of Key West in June(12–16), delegates from over 35 countrieshad ample opportunity to discuss and arguewith each other over a dry martini or mar-garita while the sun set over the beautifulFlorida Keys. Articles from the conference areto be published in a special edition of the

Annals of the New York Academy of Sciencesdue to be published early in 2000. On a per-sonal note, I very much enjoyed the confer-ence with its wide ranging agenda which,thanks to the superb local organization byPaul Gibbs and Beth Miller-Tipton (Universityof Florida), allowed for much exchange ofideas and opinions on how to prioritize ourtechnological, educational and political skillsto make an impact on disease control.

Elisabeth Innes is at the Moredun ResearchInstitute, Pentland Science Park, Edinburgh, UKEH26 0PH. Tel: +44 131 445 5111, Fax: +44131 445 6111, e-mail: innel@mri.sari.ac.uk

428 Parasitology Today, vol. 15, no. 11, 19990169-4758/99/$ – see front matter © 1999 Elsevier Science Ltd. All rights reserved. PII: S0169-4758(99)01543-4

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Beverly, MA, USA Jan/Feb 1999

How could scientists working on thepathogenesis of filarial diseases, spe-ciation and parthenogenesis in insects,sex-ratio deviations in crustaceans, pestcontrol, and the evolution of bacterialgenomes be united? How could a com-mon research project attract the inter-est of these scientists? How could parasitology be made even more multi-disciplinary? Two workshops organizedby New England Biolabs Inc. (Beverly,MA, USA) provide a simple answer tothese questions: studying the genomesof Wolbachia endosymbionts.

What is Wolbachia?

During the first meeting held in Beverly (January 1999), introductionsto the biology of Wolbachia were pre-sented by John Werren (University ofRochester, NY, USA), Scott O’Neill(Yale University, New Haven, CT,USA) and Claudio Bandi (University ofMilano, Italy). The implications of study-ing the Wolbachia genome from filarialnematodes were discussed by DavidGuiliano (University of Edinburgh, UK).Key points are presented below.

Wolbachia is a group of obligate intra-cellular bacteria that are widespread inarthropods. Important insect pests anddisease vectors have been found toharbour Wolbachia1–3. Wolbachia is also

present in filarial nematodes; most ofthe species so far examined areinfected by these bacteria4. [See alsoM. Taylor and A. Hoerauf, this issue.]

Wolbachia is maternally transmittedto offspring in both arthropods andfilarial nematodes. For a bacterium thatis transmitted through females, inducingsex-ratio biases towards females canenhance its own transmission. Partheno-genesis (eg. in wasps), death of maleembryos (eg. in a ladybird) and femi-nization of genetic males (ie. in isopodcrustaceans) are three different waysby which Wolbachia causes sex-ratiodeviations in arthropods. A further kindof reproductive alteration resulting fromWolbachia infection in arthropods iscytoplasmic incompatibility (CI). CI is anincompatibility between sperm frominfected males and eggs from unin-fected females. CI has obvious potentialimplications for speciation. A Wolbachiastrain (the ‘popcorn’ strain) that is inva-sive and pathogenic to fruitflies has alsobeen described5.

In filarial nematodes, the phylogenyof Wolbachia endosymbionts is congru-ent with the phylogeny of the hostworms. In addition, in infected speciesall specimens examined have beenshown to harbour the bacterium.These phylogenetic patterns suggest along coevolutionary history and recip-rocal coadaptation between filarialworms and their wolbachiae. Further-more, treatments with the bacteriostatic

drug tetracycline have been shown toinhibit reproduction and developmentin filarial nematodes harbouring Wol-bachia6–8. Thus, there is an overall con-sistency of data supporting the possi-bility that Wolbachia is necessary to thehost nematode.

Why Sequence WolbachiaGenomes?

Wolbachia is a group of closelyrelated bacteria that can induce differ-ent phenotypic effects on their inverte-brate hosts: from the ‘popcorn disease’of fruitflies to a possible beneficialeffect in filarial nematodes, and fromparthenogenesis in wasps to femini-zation of genetic males in crustaceans.Studying and comparing the genomesof these bacteria could thus shed lightnot only on how Wolbachia determinesthese different phenotypes, but also onthe basic biology of sex determination,reproductive isolation, bacterial patho-genesis and mutualistic symbiosis. Butthere are further reasons to investigateWolbachia genomes. First, the mol-ecular mechanisms that Wolbachia usesto manipulate host reproduction couldbe exploited to control insect pestsand disease vectors. Second, Wolbachiacould provide a set of molecular targets for the diagnosis and control of filarial diseases and for aiding in-vestigations into the pathogenesis ofthese diseases.

Wolbachia Genomes and the Many Faces of Symbiosis

C. Bandi, B. Slatko and S.L. O’Neill

More Intracellular Symbionts

The second meeting (February 1999)was opened by four presentations.Kostas Bourtzis (Institute of MolecularBiology and Biotechnology, Heraklion,Greece) informed participants onEuropean initiatives to sequence thegenome of Wolbachia. An update on theBuchnera aphidicola Genome Projectwas presented by Hajime Ishikawa(University of Tokyo, Japan). Buchneraaphidicola is an obligate intracellularsymbiont of aphids and is thought tohave coevolved with these insect hostsduring the past 200 million years9. Se-quencing the genome of B. aphidicola isexpected to provide new insights intogenomic evolution in intracellular bac-teria. Peter Fischer (Bernhard NochtInstitute for Tropical Medicine, Hamburg,Germany) gave an update on Wolbachiain filarial nematodes, while Mark Blaxter(University of Edinburgh, UK) pre-sented the state-of-the-art in genomestudies on Wolbachia from the filariaBrugia malayi. According to Blaxter, thebacterial artificial chromosome (BAC)library of B. malayi comprises a smallproportion of inserts derived fromWolbachia. Hybridization and endsequencing has so far allowed the assem-bly of BAC inserts that cover about33–50% of the Wolbachia genome.Further analyses on this BAC librarymight allow recovery of the wholegenome10,11. This would provide a strat-egy for sequencing the genome of Wol-bachia from B. malayi without the needfor bacterial purification (see below).

The Wolbachia Genome Consortium

The second meeting aimed: (1) to ascertain which Wolbachia genomesshould be sequenced; (2) to discussthe strategies that might be used tosequence these genomes; and (3) tocreate a ‘collaboration network’ in thisresearch area.

Four groups of Wolbachia (A–D)have been described4. There was gen-eral agreement about sequencing thegenome of Wolbachia from the filaria B. malayi, a representative of group D.Choosing other genomes led to discus-sion between supporters of differ-ent approaches: (1) sequencing thegenomes of closely related wolbachiaethat induce different phenotypes; or (2)sequencing the genomes of distantlyrelated wolbachiae (i.e. representativesof groups A and B that are found inarthropods). The final consensus wasto follow the second approach.

As highlighted by Scott O’Neill, HenkBraig (University of Wales, Bangor, UK)and Timothy Karr (University of Chicago,IL, USA), procedures are available topurify Wolbachia from insect tissues.These methods might allow recoveryof pure Wolbachia DNA that could beused to produce a genomic library suit-able for ‘shotgun’ sequencing. Thissequencing approach involves randomsequencing in which thousands ofclones are sequenced to produce over-lapping fragments that cover the lengthof the target genome. The methodsused to purify Wolbachia from insectscould be adapted to filarial nematodes,thus allowing the application of theshotgun approach to their wolbachiae.The shotgun approach has alreadybeen used to sequence the genome ofRickettsia prowazekii12, an intracellularbacterium related to Wolbachia.

One of the main outcomes of the meeting was the establishment ofthe Wolbachia Genome Consortium. Thegoal of this consortium will be to providean organizational structure for scientificinteractions and collaborations focusedon investigating the genome of Wolbachia.A third meeting (Wolbachia 2000) isscheduled for June 2000 in Crete.

References1 Werren, J.H. (1997) Annu. Rev. Entomol. 42,

587–6092 O’Neill, S.L. et al. (1997) Influential Passengers,

Oxford University Press3 Rigaud, T. (1999) Trends Ecol. Evol. 14,

212–2134 Bandi, C. et al. (1998) Proc. R. Soc. London Ser.

B 265, 2407–24135 Min, K.T. and Benzer, S. (1997) Proc. Natl. Acad.

Sci. U. S. A. 94, 10792–107966 Bandi, C. et al. (1999) Int. J. Parasitol. 29,

357–3647 Hoerauf, A. et al. (1999) J. Clin. Invest. 103,

11–188 McCall, J.W. et al. (1999) Ital. J. Zool. 66, 7–109 Baumann, P. et al. (1998) Am. Soc. Microbiol.

News 64, 203–20910 Blaxter, M.L. et al. (1999) Parasitology 118,

S39–S5111 The Filarial Genome Project (1999) Parasitol.

Today 15, 219–22412 Andersson, S.G. et al. (1998) Nature 396,

133–140

Claudio Bandi is at the Istituto di PatologiaGenerale Veterinaria, Università di Milano, ViaCeloria 10, 20133 Milano, Italy. Barton Slatkois at New England Biolabs Inc., Beverly, MA01915-5599, USA. Scott L. O’Neill is at theDepartment of Epidemiology and PublicHealth, Yale University School of Medicine,New Haven, CT 06520, USA. Tel: +39 0226680443, Fax: +39 02 2364470, e-mail: claudio.bandi@unimi.it

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News

Websites of Interest

Malaria Foundation International This has opened a CommunicationCenter for malaria-related job opportunities (postings searchable by keyword) at http://www.malaria.org.

On-line medical dictionary? A good one exists at http://www.graylab.ac.uk/omd/index.html

Programme Against African Trypanosomiasis Information SystemThe PAAT-IS Resource Inventory has tsetse and trypanosomiasis information for 37 African countries athttp://www.fao.org/paat/html/ri.htm.

Research and Training in Tropical Diseases See the new TDR websiteat http://www.who.int/tdr

History of malaria, its control and public policy Intended as a sourceof information for those interested in these subjects, this lively websitealso has links to literature on malaria vectors and on bednets andincludes an account of the debate about DDT, including contributions tothe malaria discussion group and extracts from the press. Start athttp://www.angelfire.com/ma/laria/sitemap.html

The Society of Nematologists The Biological Control Committee has awebsite at http://sacs.cpes.peachnet.edu/nemabc which has nice picturesof the natural enemies of nematodes.