Microbicides 2004 Microbicides 200428-31 March 2004, Hilton London MetropoleThe conference42 million men, women and children worldwide were living with HIV by the end of December 2002 (source: UNAIDS), including five million newly-infected during that year alone. Another 45 million people will become infected between 2002 and 2010, unless the current transmission rates can be vastly reduced. Of the 42 million, 29.4 million live in sub-Saharan Africa and 58% of them are women. Not only are women more susceptible to HIV infection, many are powerless to insist on the use of condoms or other methods of protecting themselves. In this context, and with the knowledge that an effective HIV vaccine is unlikely to be available for several years, the need for an effective topical microbicide grows ever more urgent. 2004 should prove to be a landmark year in the field of microbicide development as the first Phase III trials of novel products are due to start – the next step along the road to making a microbicide available to the millions worldwide in desperate need of protection.The aims of the Microbicides 2004 conference are to:Report novel or innovative work in the microbicides fieldProvide updates on recent microbicides research, divided into three tracks: basic science, clinical science, and behavioural science (including public health and the microbicide marketplace)Provide a forum for the discussion of new developments in microbicide research including ethical, clinical, behavioural and methodological issuesPresent opportunities for knowledge-sharing between microbicide researchers, public-health workers and advocacy organisations.There will be an opening ceremony on the evening of Sunday 28 March at which politicians, policy makers and the international media are expected. The conference will run for a full three days, each of which will contain:Scientific overviews and presentations with plenary sessions, invited lecturers and presentations of original researchWorkshops to review issues unique to microbicides such as trial design and outcome measures, and ethical issues in the clinical trials of microbicidesPoster sessions. Focus on LondonFollowing the successful Microbicides conferences in Washington in 2000 and Antwerp in 2002, March 2004 sees the focus move to London.The venue is the Hilton Metropole Hotel, two minutes by taxi from Paddington station and the Heathrow Express, with a journey time from the airport of 15 minutes. The hotel is in walking distance of Hyde Park and London’s main shopping streets, and close to Imperial College. Accommodation will be available at the venue and other hotels in the vicinity.London in March offers a variety of diversions for out-of-conference relaxation, including sight-seeing and shopping; the arts and the theatre; and pubs, clubs and restaurants to suit every taste. Conference staff will be on hand to help delegates plan their spare time.To book your place or find out more information, e-mail info@microbicides2004.org.uk or telephone the Event Office on +44 (0) 20 7720 4411
Oral: invited speaker Oral: Track A Oral: Track B Oral: Track C Poster: Track A Poster: Track B Poster: Track C Abstract only Authors

02698 MC 1220 AS KNOCKING OUT NNRTI TO PREVENT SEXUAL TRANSMISSION OF HIV

Musiu Chiara*,
Maga G.^, Loddo R.§ and La Colla P.§
*University of Cagliari-Idenix Cooperative Laboratory, Italy; ^Istituto Di Genetica Molecolare, Cnr, I-27100, Pavia; §Dept of Biomedical Sciences and Technologies, University of Cagliari, Italy.

Background. Although progress has been made in post-infection treatment strategies for HIV-infected individuals, the development of effective topical microbicides to control sexual HIV transmission has lagged behind. However, microbicides are urgently needed because it has become increasingly clear that viral loads in vaginal mucosa and seminal fluid are strictly related to HIV transmission rates. Since non-nucleoside reverse transcriptase inhibitors (NNRTIs) are among the agents proposed as microbicides, following up the report of the virucidal activity of UC781 and L737,126, we comparatively evaluated the capability of the latter, of other NNRTIs used in the clinic and of MC-1220 to irreversibly knock out the HIV infection in vitro.

Methods. Long-term assays were set up to discriminate between virustatic and virucidal activities of NNRTIs. Compared to standard assays, our experimental conditions were characterized by: i) the use of a 20 to 40 fold higher m.o.i, ii) culture splitting conditions which avoid losing infected cells, iii) evaluation of HIV-1 multiplication up to day 40 post infection (p.i.), iv) testing of virucidal activity at every 4-day interval by recording cell viability, presence of syncytia, p24 levels, infectious virus yield, presence of viral DNA or RNA sequences.

Results. Following a chronic treatment started immediately after infection, MC-1220 and L-737,126 are the most potent NNRTIs (1 mM) in irreversibly knocking out the HIV-1 multiplication, followed by UC-781, Efavirenz (4 mM) and Nevirapine (20 mM). Following up a treatment limited to the first 4 hrs p.i., MC-1220 is the most potent (11 mM) knocking out drug, followed by UC-781 (50 mM). On the contrary, Nevirapine, Efavirenz and L-737,126 are totally ineffective (>100 mM). Following up a treatment limited to the 2 hr infection period (see graph on the left), only MC-1220 (11 mM) irreversibly knocks out the HIV multiplication, whereas UC-781, Nevirapine, Efavirenz and L-737,126 are ineffective in preventing the viral breakthrough at concentrations as high as 100 mM. Following up a 4 hour treatment before infection (see graph on the right), MC-1220 (11 mM) and UC-781 (50 mM) are both capable of irreversibly knocking out the HIV-1 multiplication in the absence of extracellular drug. Viceversa, Nevirapine, Efavirenz and L-737,126 are inactive at concentrations as high as 100 mM. It is worth noting that MC-1220 is not cytotoxic following up a 40-day long-term treatment at concentrations up to 200 mM. Moreover, MC-1220 lacks inhibitory activity against vaginal commensals, such as Candida spp. and Lactobacillus spp.

Enzyme kinetic assays with the HIV-1 reverse transcriptase (RT) show that MC-1220 is the best tight-binding inhibitor with a Koff = 8x10-5 s-1. Last but not least, the dissociation rate of MC-1220 is unusually low when compared to the other tight-binding NNRTIs.

Conclusion. MC-1220 may have considerable promise as a virucidal agent to prevent mucosal HIV transmission.

Chiara Musiu
*University of Cagliari-Idenix Cooperative Laboratory, Cittadella Universitaria di Monserrato, S.S. 554, Km 4,500, 09042 Monserrato (CA) Italy
(Telephone) 070/6754147 (Fax) 0706754210 (E-mail) musiu@unica.it