Mycobacterium ulcerans: An emerging disease

FIS 99 Abstracts

INVITED SPEAKERS ABSTRACTS

A 7

1.1DNA VACCINESDr Jeffrev B. Ulmer, Chiron Corporation, Emeryville, USAThe efficacv of DNA vaccines in oreclinical animal models has beenwell documented (for review see Donnelly et al., Annu. Rev.Immunol. 15, 617, 1997). However, the magnitude of immuneresponses induced in primates is generally lower than that in smallanimals, and the amount of DNA required for effectiveimmunization of primates is much higher (mg versus mcg). Inaddition, several phase I human clinical studies have beenconducted with little or no immune responses reported. Therefore,the potency of DNA vaccines must be increased to enable thistechnology for successful human application. Means by which thiscould be accomplished include increasing antigen expression orDNA adjuvanticity through manipulation of the plasmid, facilitatingtransfection of cells in situ via DNA delivery systems, andcoadministration of adjuvants to modulate or enhance the immuneresponses induced. A key to taking rational approaches in theseareas will be a greater understanding of the mode of action of DNAvaccines, such as the mechanism of CTL priming and theidentification of the rate-limiting steps to effective transfection ofcells in vivo.With regard to CTL priming, we and others have established thatAPCs are required for induction of CTL responses induced by DNAvaccines (Fu et al., Mol. Med. 3, 362, 1997). However, it is not yetknown whether this is a function of antigen expression within oracquisition of antigen by these cells. We have shown that cross-priming can occur from muscle cells to APCs in vivo (Doe et al.,PNAS 93, 8578, 1996; Ulmer et al., Immunol. 89, 59, 1996), andthis transfer involves soluble antigen, and does not require cell tocell contact or MHC class I molecules. These data indicate thatefforts to facilitate cross-priming and to target APCs for transfectionshould be pursued. With regard to DNA distribution and traffickingin situ, we have used modified DNA plasmids that allowvisualization of the plasmid itself as well as the expressed proteins.We have found that, while detectable expression of the plasmid wasobserved only in muscle cells, most of the plasmid was internalizedby macrophages in the muscle compartment where the plasmid wasrapidly degraded within the lysosomes. Therefore, efforts designedto bypass or facilitate delivery of plasmid DNA out of thisdegradative compartment and into the nucleus of these cells maytake advantage of their antigen presenting capabilities.1.2PREPARING FOR THE NEXT INFLUENZA PANDEMICProfessor John S. Oxford, St Bartholomews and The RoyalLondon School of Medicine and Dentistry, LondonWorld wide outbreaks of influenza A pandemics occur infrequentlyand within living history have caused serious mortality andmorbidity in 1889, 1918, 1957 (H2N2) and 1968 (H3N2). Theseemerging viruses may originate in chickens or pigs. Although theH2N2 and H3N2 oandemics aDDeaIXd to start in Asia. and althoughmore recently H9’ and H5 a&n influenza A viruses have causedproblems in Hong Kong, it is nevertheless possible that pandemicscould appear first in other places of the world. With colleaguesR.Webster, R. Daniels and J.J. Skehel we joined a group ofCanadian and Norwegian scientists to investigate six coal minerswho died of so-called Spanish influenza in 1918. This is the fourthattempted exhumation of influenza victims and we wish now toextend this work to the preceding pandemic in 1889.The objective of the study is to identify nucleotide sequences whichcorrelate with virulence. Two new anti-neuraminidase drugsRalenza and Tamiflu have been developed recently, which togetherwith amantadine and sub unit vaccines would be expected toabrogate any future pandemic. However, pandemic planning is nowproceeding rather urgently in all countries of the world withencouragement from WHO.

1.6MYCOBACTERIUM ULCERANS: AN EMERGINGDISEASEDr Mark Evans, LondonMycobacterium ulcerans infection (Buruli ulcer, BU) is anemerging disease [W.H.O.] and 12,000 cases reported in the last10 years in West Africa is considered a gross underestimate. BUis the third commonest mycobacterial infection affecting man. Itis the only mycobacterium to release a toxin, characterised as alipid polyketide, which causes fat necrosis, localimmunosuppression and large disfiguring skin ulcers. Severecontractures and disability result. It invariably occurs in riverineiswampy areas, but its mode of transmission is still unknown.Believed to enter the body through skin abrasions, M. ulceranshas been found by PCR in water samples from Ghana andAustralia and from the water bug in Ghana. The disease starts asa small painless nodule which progresses by subcutaneousnecrosis to extensive ulceration. Excision at the early nodularstage is usually curative.Clinical data from 926 Ghanaian BU patients will be presented. Ina DGH, in the endemic area, 70% beds in August 1998 wereoccupied by BU patients. High occupancy was because of latepresentation and massive ulcers, extensive surgery, skin graftingand complications (such as SCC). I established an outreach villageproject [ongoing] with the aim of 1) Health education to promoterecognition of early lesions; we produced a colour video andposters 2) Prevention of the severe later stages of BU by excisionof early nodules 3) Laboratory analysis of the nodules includinghistology and quantification of M. ulcerans 4) Reducing overallcosts; Cost/Benefit analysis will be presented 5) Assessment ofrecurrence rate 6) Analysis of predisposing/ influencing factorsincluding BCGi HLA susceptibility/ HIV infection. 7) Training oflocal health care workersOver 375 clinical samples from different stages of BU werecollected for laboratory analysis, mainly bacterial culture andhistology. These results will be presented including recurrence.PCR analysis was undertaken from both clinical and watersamples [n>150] and the first reported detection of M. ulcerans inwater [subsequently found to be in a water bug] was made inGhana [by Professor F. Portaels] from this district. Serumsamples [n = 228 from 78 subjects] were collected for antibodyresponses to specified epitopes at different stages of disease.DNA has been extracted from blood samples [n=88] for HLAanalysis. T lymphocyte responses from BU and TB patients afterstimulation with Burulin and PPD were examined. Results will bepresented.Treatment at present is predominantly surgical. We conducted apilot study using topical phenytoin [libroblast proliferation] as acheap and easily applicable alternative for small areas ofulceration. We investigated sensitivity in vitro of M. ulcerans toanti-mycobacterial agents in order to develop an effectivetreatment regime.Satellite imaging revealed an unusual red colouration along theOffin river upstream of endemic villages. Using GIS, Pterocarpussantalinus trees were identified; not used for any building ormedicinal purposes, they exude an acidic sap. Studies concerningpH of water near endemic BU areas have shown acidic pH. Otheraffected areas in Ghana (and other affected countries) are beinginvestigated.This is a collaborative project between School of Medical Sciences,University of Science and Technology, Kumasi and Ministry ofHealth, Ghana and St. George’s Hosp Med Schl, London,sponsored by The Wellcome Trust. Funding also from the Dutchand Japanese Embassies, Accra, Ghana