The 10th International Conference on Human Chlamydial Infections.

Introduction: Traditionally the international conference on human chlamydial infections alternates, every four years, between the American and European continents. Antalya, on the southern Turkish coast, is in Asia Minor. Nevertheless, once one had worked out how to get there in competition with all those sun worshipping holiday makers, this was a welcome change of venue. It reflects both the global impact of chlamydial infections and the increasingly global scientific contribution to chlamydial research. Attendance (198 participants from 22 countries) was slightly down, presumably in the aftermath of September 11th., but the venue and organisation were superb. Thanks for this must go to the local organising committee, in particular to Professor Demir Seter and Drs Deniz Gokengin and Ali Agacfidan. Chlamydiologists also owe a particular debt to Professor Julius Schachter and his indefatigable team in San Francisco for their crucial and again evident role in promoting and gaining sponsorship for this conference series.

All papers submitted to the conference were reviewed by a scientific review committee. They did an excellent job of ensuring that the standard was extremely high, perhaps with one exception. One of their more difficult jobs was deciding whether a paper submitted to the conference entitled  "www.chlamydiae.com an information resource for chlamydial researchers and health care professionals: a progress report", clearly not a research paper, was suitable. I am grateful that they took a broad view of this! With the aid of chlamydiae.com T-shirts, I don't think there was anyone who did not know the url of this website by the end of the conference.

This 10th conference, in contrast to its 1998 predecessor in Napa Valley, reflected a period of consolidation rather than breakthrough. There was nothing comparable to the breakthrough represented by the advent of the first whole genomic sequence for C. trachomatis; that first genomic sequencing project gave us unprecedented insight into what, hitherto, in the absence of the usual genetic tools, had been almost a complete unknown. With chlamydial  genomic sequencing projects proliferating, we have perhaps begun to take the insights of genome sequencing for granted although I personally eagerly await the first Parachlamydia genome sequence. Chlamydial transcriptomics and proteomics are still in their infancy but can be expected to provide important insights into the chlamydial developmental cycle and possibly immune evasion. At Antalya as the details emerged it became evident just how sophisticated this bug is.

Given the overall excellence of the conference, it is invidious and no doubt arbitrary to select any particular paper. However, here goes!

Evolution and genomics: The opening paper by Rick Stephens (San Francisco) on chlamydial evolution "A billion years and counting" was highly enjoyable. This was an excellent, thought provoking but provocative paper in substantial agreement with the Moulder paper on this site and current views on other intracellular pathogens such as Buchnera. The eukaryotic divergence probably occurred about 2 billion years ago. The presence of some 26 plant-related eukaryotic gene sequences in the chlamydial genome probably indicates that the original free-living protochlamydiae interacted extensively with eukaryotic protozoans. The more than 92% similarity between the C. pneumoniae and C. trachomatis genome suggests that in contrast to free living prokaryotes, chlamydiae have been characterised by genetic isolation and accumulation of point mutations rather than wholesale genetic exchange and recombination as for E. coli / Salmonella. There has been gene loss / duplication rather than gene gains and relatively long periods of time without significant phenotypic change. This suggests that the intracellular habitat is a protected rather than hostile environment, characterised by weak selective pressures. In the absence of recombination [but note there is evidence for recombination in MOMP] there has been an increased fixation of mildly deleterious mutations. Rick stated that in E. coli only one nucleotide mutation in 20 leads to an amino acid change, whereas in Buchnera the figure is one in four and for Chlamydia 1.5:1. The result is substantial accumulated degradation in protein function which may be compensated in part by increased chaperonin (e.g. hsp60) to compensate for damaged proteins. Since the evolution of chlamydiae is substantially different from that of free living bacteria, Rick believes the usual rules of species and genus differentiation as used in the new taxonomy are not appropriate. He argued that rRNA sequence differences overestimate for chlamydiae the time of divergence and phylogenetic separation. Chlamydial divergence to different hosts was placed at roughly 100 million years ago following the dinosaur extinction. It was suggested that LGV diverged with the availability of new primate hosts. Divergence of the genital and ocular strains of C. trachomatis probably occurred in early humanoids. Of course much of this is inevitably speculative and this site will be pleased to post views on this on the discussion forum. 

Sarah Garner (Southampton) described the first bacteriophage known to infect C. pecorum. Although this was similar to other chlamydial Microviridae, it is fascinating that so far these bacteriophages have been restricted to the genus Chlamydophila. It was evident at the meeting that there was increasing interest in chlamydial bacteriophages, both because they are potential vectors for chlamydial gene manipulation and because they may be telling us something about the evolution of the Chlamydiaceae.

Cell Biology: Daniel Rockey (Oregon) presented a superb overview of the nature of chlamydial interactions with the host cell. I confess though that I am still a mite confused about chlamydial induced apoptosis and its significance. This is one area where I find it hard to reconcile all the data.

Priscilla Wyrick (East Tennessee) presented evidence that protein disulphide isomerase, a component of the oestrogen receptor complex, becomes associated with C. trachomatis serovar E attachment to human endometrial cells. While it is still early days, this might explain why chlamydial attachment to endometrial cells is enhanced by oestrogen and opens up a number of other possibilities which are experimentally verifiable.

Coombes and Mahoney (Hamilton) presented an excellent paper characterizing some of the signalling cascades which appear to be associated with chlamydial invasion and not just attachment. There is much further detail to be revealed here. In similar vein in another excellent paper, Marci Scidmore (Cornell) showed that IncG interacts with the 14-3-3beta eukaryotic signal transduction protein to alter MAPK signal transduction. 14-3-3 proteins may play a key role in intracellular chlamydial survival, for example by preventing degradation or dephosphorylation of IncG or by assembling signalling molecules at the inclusion membrane.

Toni Darville (Arkansas) investigated whether membrane glycosaminoglycans might be used as chemical condoms to prevent chlamydial infection of urogenital epithelia. Given the high concentrations apparently needed, I think I'll stay with latex.

Prevention: Strategies to control human urogenital infections with C. trachomatis seem to be shifting towards community-based, rather than clinic-based, methods. This shift in priorities has been made possible by the excellent performance of the newer nucleic acid based diagnostic tests and the use of non invasive home sampling. Particularly innovative in my view has been the work of Lars Ostergaard and colleagues (Aarhus) but there were several other good papers in this area.   Kevin Fenton (London) eloquently presented important results on the prevalence of chlamydial infection in the UK from a national survey of sexual attitudes and lifestyles. Chlamydia are now being taken very seriously by the department of health in the UK, as a parliamentary debate reproduced elsewhere on this web site will show. Of course sexual behaviour underlies the spread of sexually transmitted infection. A fascinating paper was presented on behalf of Rachel Kachur (CDC Atlanta) indicating that people meeting sexual partners through internet chat rooms as a group have high risk sexual behaviours.

Treatment:  A useful review by Geoff Ridgway (London) on antibiotic resistance in human chlamydial isolates seemed to conclude  that this is a matter for concern but not yet a critical clinical problem (see antibiotic resistance) although widespread antibiotic resistance in C. suis in pigs indicates the need for vigilance. Julius Schachter (San Francisco) pointed out that many patients apparently failing antibiotic do respond if given another course of the same antibiotic, suggesting that compliance is a big issue. There was some interest apparent in the newer quinolones for antichlamydial therapy, but little evidence of any major breakthrough in treatment comparable to the advent of azithromycin.

Diagnostics: Julius Schachter presented the opening overview. Apparently, since 1997 the number of diagnostics tests performed for C. trachomatis in California has dropped by 9%. Furthermore only 22% of the tests performed were nucleic acid amplification based tests, with 60% being relatively insensitive probe-based hybridisation tests. Sensitivities of the current generation of nucleic acid amplification based tests were approaching the limits of the ability to test specificity. There had been much focus on  specimen inhibitors of amplification as a problem, but in his view, with appropriate storage methods, this was not a big problem. Nevertheless there was still a need to sort out what was the ideal specimen for a particular condition; no single specimen achieved 100% diagnostic sensitivity. Recently there had undoubtedly been manufacturing problems with some of the nucleic acid amplification based tests. An answer to this might be to set up independent "sentinel" reference laboratories. There was then a discussion on the problem caused by strong positive tests on urine which became negative on repeat testing. Julius believed that some specimens may not be stable to recommended storage conditions. It should also be remembered that most research evaluation studies of tests were performed under relatively ideal conditions compared to those of a busy routine diagnostic laboratory.

PCR studies on C. pneumoniae have hitherto been bedevilled by the variability of in-house assays. However Abbott laboratories now had a commercially produced C. pneumoniae PCR assay available for research use only. An interesting multi-centre comparison of this new Abbott LCx^® PCR with various C. pneumoniae in-house PCRs was described by Max Chernesky (Hamilton) who reported that the Abbott PCR was superior to the 'home brew' tests studied.  Investigators wishing to collaborate with Abbott in using the test for research purposes should contact the company direct.

Commercial nucleic acid amplification tests are moving towards multiple pathogen targets and greater simplicity. Papers from Angelika Stary (Vienna) and Dennis Ferrero (San Joaquin) indicated that the new Gen-Probe APTIMA Combo 2 assay for C. trachomatis and N. gonorrhoeae is the most sensitive of all the nucleic acid amplification-based methods, highly effective and FDA-approved for screening  urine and suitable for other non-invasive specimens. In Europe the chlamydial APTIMA CT test is likely to be of particular interest, and Martha Bott (Gen-Probe) indicated that this particular test might additionally include a confirmation assay targeted against a different rRNA sequence.

An interesting paper by Jeanne Moncada (San Francisco) indicated that the volume of urine recommended by the manufacturers for tests using nucleic acid amplification methods is not necessarily the optimal volume. Given that only 31% of females were able to pass less than 30 ml of urine into a container despite specific request, there was a light hearted discussion of the real practical difficulties faced by women in providing such samples. It appeared that men felt more smug about their abilities in this respect!

In the research arena the vogue is quantitative pcr. Petra Apfalter (Vienna) gave an impressive paper on real time quantitative pcr for C. pneumoniae which indicated there might be real advantages in this approach.

Trachoma: Approximately ten per cent of the worlds population live in areas where trachoma is prevalent and are thus at risk of blindness (see trachoma). Chuck Knirsch (Pfizer, New York) described the work of the international trachoma initiative. This is a public private partnership, between Pfizer Inc., (who have generously contributed over one million treatments with their antibiotic azithromycin) the Edna McConnell Clark Foundation, WHO and others. The initiative has practically demonstrated that its SAFE strategy works in preventing trachoma, but substantial efforts will be needed to sustain the effects. A relevant cautionary note was struck by Sheila West  (Baltimore & Tanzania) who primarily attributed trachoma re-emergence in areas which had had mass trachoma treatment to population mobility leading to acquisition of infection from outside the community. Quantitative PCR methods are being applied in trachoma field studies. Robin Bailey (London and Gambia) reported that active disease, particularly TI (intense trachoma) is, not surprisingly, associated with high copy number. Lack of access to latrines was associated with an independent risk of high bacterial load and fly-eye contacts played a key role. Identifying efficient targeting strategies for control programs without microbiological testing is a problem. However fly control reduced the prevalence of trachoma in 0-7 year old children in Gambian villages by 52%. A paper by Solomon (London) showed that in Tanzania conjunctival infection is often associated with chlamydial infection of nasal exudate. Whether respiratory droplet infection is important in trachoma spread warrants further research.

Immunology: After the disappointments of the MOMP vaccines of the 80s and 90s, there seems to be new interest in the possibility of a chlamydial vaccine. This has undoubtedly been triggered by the convergence of new genome-based screening strategies involving DNA vaccines together with general agreement of the key importance of the Th1 response for protection but somewhat less understanding of the role that such responses might also play in immunopathology. Joseph Igietseme  (Atlanta) presented a memorable overview of the field and will shortly be providing a new review for this site. To this reviewer's mind no startling advances in vaccine research were presented at the conference; it was more a question of consolidating present understanding. Veterinarians are taking a major interest in this field and Bernhard Kaltenboek (Alabama) reported some promising results on chlamydial induced cattle infertility with a C. abortus (I assume) DNA-based, multi-gene vaccine.

Structure and Proteomics: Some memorable papers in this field were presented by Gunna Christiansen, Svend Birkelund and colleagues from Aarhus in Denmark. There was further information about the pmp proteins and their diversity, but I was disappointed that the function of these proteins is still largely unclear. Agnes Szczepek (Berlin) presented interesting localisation studies on the CPAF, the chlamydial protease-like activity factor described by Zhong, which appears to be directed against the mammalian transcription factors that regulate MHC class I and II. Jim Mahoney (Hamilton) presented eloquent studies on the role of protein kinases following chlamydial entry and suggested that the C. trachomatis pkn5 gene might encode a type III secreted effector protein. Proteomics is a new chlamydial science but, together with micro-array and transcriptional analysis is well poised to examine questions related to the nature of chlamydial persistence.

Molecular Biology: Peter Timms (Brisbane) presented a clear overview followed by an interesting paper on the control of chlamydial gene expression by different sigma factors with their possible consensus sequences. Microarray techniques were being used by  Robert Belland (Hamilton Montana) to examine chlamydial gene expression in the presence and absence of gamma interferon as a model of persistent infection and by Tracey Nicholson (Berkeley) to look at changes in gene expression following penicillin-induced persistence. Jane Raulston (E. Tennessee) outlined some relatives of the E. coli ferric uptake regulator in C. trachomatis. These studies, essentially descriptive at this time, are likely to lead to new insights into the nature of chlamydial persistence, its interaction with the host immune response and the regulation of iron uptake.

C. pneumoniae. As this site has documented, there is much circumstantial evidence suggesting that Chlamydophila pneumoniae may play a role in atherosclerosis and an alarmingly large number of other chronic diseases, but proof, due to the nature of the problem,  is hard to come by. Chuck Knirsch (Pfizer, New York) described the findings of the azithromycin intervention trial for heart disease on approximately 7,000 subjects, from which Pfizer, as reported in the news section of this site, have now withdrawn. Although the overall results were statistically insignificant, it appears that in some subsections of the trial, e.g. for men, there was evidence of marginal effect. These trial results clearly need to be examined very carefully with an open mind when the full report is published. Perhaps the expectation that one might be able to ablate late, serious heart disease with antibiotics was unrealistic. This does not preclude the possibility that antibiotics might have a beneficial effect if given early enough and in a suitably sustained manner. Fortunately a large NIH trial is due to report next year and hopefully might clarify what is a reasonable expectation in this field. The fate of this whole active field of endeavour meanwhile hangs in the balance.

Conclusions:  The most important aspect of any scientific conference is the meetings and friendships which take place outside the main arena. The warmth and and quiet efficiency of our Turkish hosts unobtrusively ensured that from this conference many new flowers of knowledge and understanding of the chlamydiae will grow.  I took home impressions of a friendly people, an ancient land, studded with monuments of the past and, in the present, great scenic beauty. I will not forget a performance of Verdi's "Nabucco" in the ancient amphitheatre at Aspendos. This was an excellent conference, greatly stimulating to all who took part. Any serious ideas for a possible venue for the next international chlamydia conference in this series in 2006 will be welcomed by Julius Schachter and the organising committee.

I have missed out many important papers; your contributions re the conference are welcome on the discussion forum.

Reference

[MEW] August 2002