The forms which Cpn can take on in it's life cycle.

Expert close to Vanderbilt work describes throrough Cpn treatment.

Submitted by Jim K on Mon, 2005-09-12 23:59

What follows is an interview with a physician who has significant expertise in treating Cpn who has closely followed the Vanderbilt research over the years. He has garnered a lot of clinical experience, and his insights provide a lot of information both for patients and physicians who are looking to treat for Cpn. He prefers to remain anonymous. We’ll call him Dr. A for this interview. Testing for Cpn JimK- So what about serological testing for Cpn? Dr. A-Testing for Cpn is only useful if you get a positive result. Because Cpn is an intracellular pathogen, PCR testing may be negative unless infected cells containing the DNA of the organism are directly tested. That is a problem for any PCR or antigen forms of testing. Serological testing has two problems. The first is that by middle age, most people have been exposed to Cpn and will have IgG titers against this organism. If you are exposed and have a positive titer, then you most likely have a persistent infection somewhere, but this infection may not be causing symptoms. Thus, a positive serological test cannot distinguish asymptomatic persons from symptomatic persons. The second problem is that even persons with culture-proven Cpn in their coronary arteries only had a 35% positive rate by serological testing in a study done in Germany. The most sensitive test appears to be reverse transcriptase PCR testing for messenger RNA produced by infected cells. This testing, for example, showed 18.5% of blood donors to have messenger RNA from Cpn in their peripheral blood mononuclear cells.   JIMK- So there’s no easy way to test for the intracellular phase of Cpn? Dr. A- It’s very difficult to test for the intracellular phase because the organism isn’t readily available to be tested unless you have infected cells to be tested. Testing for messenger RNA from infected cells appears to be the most sensitive method. However, this method is not commercially available. JIMK- So PCR is just the most sensitive test for detecting DNA or RNA floating around in the serum or tissues. Dr. A- If you test for antibodies you are testing for the response of the patient. If you test with PCR you are testing for DNA or RNA from the actual organism. JIMK- You have said that they are useful if they are positive, but not particularly useful if they are negative. Dr. A- Right JIMK- That’s when you might decide to do an empirical course of treatment or something? Dr. A- Exactly. Empirical Diagnosis JIMK- When you make a medical judgment on that, is it based on the disease? Are there also sets of symptoms you might be looking at? In David Wheldon’s web site, he refers to history of respiratory illness. Are there other useful indicators? Dr. A- The problem is that there are no symptoms that will hone in specifically on chronic Cpn infection. So if you have a suspicion, based on symptoms or the disease process, you begin with serology. And if you have positive serology then you may feel you have something to treat. If you don’t have positive serology and you are still convinced that Cpn is causing infection, then my approach would be to try a combination antibiotic protocol empirically, and if the patient has the side effects seen with the so-called “die-off” effect, such as those David Wheldon has described in his WebSite (Ed: these reactions typical of endotoxaemia include fever, chills, sweating, and muscle pains, coryza, widespread arthralgia and myalgia, and temporary worsening of neurological symptoms) then they may well have a Cpn infection. Once you treat for Cpn infection, all these side effects eventually go away! JIMK- What about Borrellia that creates similar side affects when treated with metronidazole? Any way to distinguish based on symptoms? I suggested to one person that porphyria might be a distinguishing factor, any others?) Dr. A- Metronidazole shouldn’t cause these effects, as it has no activity against Borrellia. It is probably killing Cpn. (Ed. Actually, this is not accurate. Dr. A does not treat Borrellia and was at this time unfamiliar with the way Flagyl is active against the cystic form of Borrellia- see Brorson & Brorson 2004, 1999. In I have been told that some Lyme doctors are using Wheldon's protocol as a primary Lyme Disease treatment. It is true that co-infection of Lyme and Cpn may be an unsuspected complication). Length of Treatment JIMK- I’ll tell you, it seems it can take quite a while… Dr. A- It can take years, much as the initial treatment for tuberculosis did. It’s just like treating tuberculosis in that it takes many months to years of combination therapy. JIMK- It Seems like people respond faster or slower. Dr. A- People respond at different rates, which probably has to do with how much Cpn they have, what tissues are infected, and how good their immune system is. JIMK- Supposedly, you’re recovering your immune system function over time from disinfecting the monocytes and macrophages. It seems, just from being on it myself for 10-11 months that different tissues get reached at different times. Also, that different agents reach different tissues. When I added amoxicillin to the doxy/zith/tinadazole I got a big flare up in body areas I had not had pain in for a while. It surprised me how much additional effect I had, since I’d been on antibiotics so long. That’s one of the questions I had. The different protocols use different combinations of antibiotics. Do you find different effectiveness in different antibiotics, or is it more a practical matter of what’s available? Dr. A- I think there are differences in tissue penetration, as well as a lot of other factors that aren’t yet clear. Choice of antibiotics JIMK Do you just tend to have a preference starting with certain antibiotic with a patient? Dr. A- I’m pretty pragmatic and generally use the least expensive and safest antibiotics. I start them on: doxycyccline (Dr. A will attend to patient reaction and have them work up to 100mg twice a day over longer or shorter period, depending on tolerance with any of these medicines), and then I add azithromycin 250 mg working up to once per day Monday/Wednesday/Friday, I work up to 500 mg twice a day for metronidazole. I’ll finally add 300 mg twice a day of Rifamcin to that. But I may start out working up to 500 mg twice a day of amoxicillin rather than doxycycline. JIMK you start out with that because it’s the easiest on the patient? Dr. A- It’s cheap, safe, and tolerated the best. Then after a month or two add the azithromycin Monday/Wednesday/Friday for a month, then the doxycycline, see how they do on all three. I’ve generally added the metronidazole into this and see how they do. I wouldn’t mind pulsing it as David Wheldon does in his protocol (Ed. This is a reference to the Wheldon protocol’s method of pulsing the metronidazole for 5 days every 3 weeks). By pulsing, you can give them time to recover from the side effects. JIMK- But it sounds like you used to give the metronidazole as a constant, then? Dr. A- Yes, that’s generally how I proceed. JIMK- That’s one drug, the metronidazole, that I had the hardest time tolerating. Dr. A- You think that one’s tough, wait until you get to the Rifamcin! JIMK- That’s one my doctor isn’t real enthused about giving me (the Rifamcin). Not sure exactly why. Dr. A- Well, most physicians aren’t familiar with it unless they’ve treated TB. JIMK- Do you think the Rifamcin is a necessary one for this protocol? Dr. A- Let me tell you what Rifamcin specifically does. When chlamydial EB’s germinate and transform into the RB’s, which is the replicating form, the first enzyme out of the EB’s is DNA-dependent-RNA-polymerase that Rifamcin specifically blocks. EB’s are like spore-like infectious form of Cpn. The cryptic form is also different to treat; it is metabolizing but is not replicating (Ed. The cryptic form is what the metronidazole is directed at, since it is metabolizing but in an anaerobic mode. Our expert is noting here that the EB’s are not metabolizing nor replicating, therefore are not affected by antibiotics that interfere either with bacterial metabolism or with bacterial replication. They are effected only by disulphide reducing agents, like amoxicillin, which breaks the disulphide latice bonds of the EB cell membrane). If you have a large EB load you’re going to keep getting cells reinfected. If you stop them before they start, that’s much better than letting them get started and then trying to kill them. JIMK- So doxy/zith is inhibiting the replicating form? Dr. A- Yes. Remember, you are trying to formulate a combination therapy that attacks all of the potential forms of Cpn. And so, N-formyl-penicillamine, which amoxicillin is metabolized to in the body, destroys the EB. It is these spore-like, non-replicating, EB’s, which invade your body’s cells and once inside transform into RB’s capable of replicating. In this transformation the first enzyme employed is DNA-dependent-RNA-polymerase, which allow this transformation. If they are in the RB replicating form, then azithromycin and doxycycline will interfere with that. If they are in cryptic form then metronidazole goes after that. If they are EB’s the amoxicillin takes care of that. If they are transforming from EB’s to RB’s, where they are particularly vulnerable, Rifamcin takes care of that. It takes a lot of different antibiotics because there are lots of different life forms. Otherwise it just goes from one life form to the next. JIMK- So, adding the Rifamcin is to be as complete as possible? Dr. A- It is hard to say if you can get by without the amoxicillan, or the Rifamcin. I suspect that you can in younger healthy persons. I tend to think that they are especially important for those who have been sick for a long time, and likely have a lot of EB’s looking for homes. I want to destroy these EB’s (amoxicillin) or if they are finding homes I want to short-circuit them (Rifamcin). The transformation from EB to RB is where they are particularly vulnerable. JIMK- That is really important information to get out there. Especially for those of us who have, indeed, been sick with this for a long time. I knew when I added the amoxicillin to the Wheldon protocol that I was killing something additional. And it was so clearly, highly inflammatory too; by the amount of pain and inflammation I had in reaction to it. Dr. A- You probably have a high EB load. Those were probably Elementary Bodies that you were destroying. By the way, you can use penicilamine directly, but that’s a very scary drug. JIMK- And that tends to dump a big load of the endotoxin when they get popped? Dr. A- That and a lot of other antigens. The response to the antigens is somewhat dependent on your body’s immune system. JIMK- So you’re getting a cytokine reaction. Dr. A- Yes. JIMK- Do you find tinidazole as effective as metronidazole? Dr. A- I don’t see why it wouldn’t be. It’s just been recently approved in the US, so I have no experience with it, or what they are charging for it! JIMK- I find I tolerate it much better than metronidazole. I got so sick on that, which I believe is more a drug side effect than a kill effect. Dr. A- Well, I wouldn’t necessarily see it that way. My experience is that people who don’t have any Cpn organisms can tolerate metronidazole without any side effects. You’re talking to someone who has had patients taking metronidazole as a post treatment preventative for a number of years without side effects. JIMK- So your bet then would be that I got sick from the metronidazole because it was killing cryptic Cpn, not because of drug side effects (Ed. which would suggest that tinidazole is not as potent in this as metronidazole). Dr. A- There are two explanations as to why you are tolerating tinidazole better. One is that you just knocked down enough of your Cpn load with the earlier metronidazole pulses. And people have done that; they say they can’t tolerate the metronidazole and then after a time they can. The other is that you were getting better penetration with the metronidazole than with the tinidazole. JIMK- So it may be that the tinidazole is not quite as strong, so it may be a good way to gear up over time to the metronidazole. Dr. A- Yes, but if you were to try metronidazole for a couple weeks and you didn’t get any side effects, then you probably don’t have much Cpn. Brain Fog JIMK- You see brain fog a lot in Cpn patients; do you see this as CNS involvement or more as an effect of endotoxin? Dr. A- It is most likely a combination of endotoxins, porphyrins, and cytokines. It may largely be porphyrins for the simple reason that reactions from porphyrins last longer than those from cytokines and there’s no fever. And you know you are better when…? JIMK- So that’s the kind of “gold standard” test: that you can take metronidazole and not get hammered? Dr. A- And Rifamcin. Rifamcin has deep tissue penetration too. So if you can tolerate the metronidazole and then I challenge you with Rifamcin and you tolerate that as well, you have very few Cpn left. I periodically challenge patients with a short course containing metronidazole and Rifamcin to see if they continue to be cleared of Cpn. JIMK- The complete challenge. The more I understand, the more I appreciate how tough a bug this is, and long it takes to get it, how complex it is, and all the tissues you need to penetrate to get there. Dr. A- Not only the tissue penetration, but also both the organism and your cells have active efflux pumping mechanisms to pump out the antibiotic. You have to work against these natural mechanisms to keep adequate concentrations in the cells. Rifamcin tends to inhibit these efflux pumps. I also use another drug, Quercetin, a bioflavonoid that also acts as a cell efflux inhibiter. It works on a different efflux pump than Rifamcin. It’s, also active against Chlamydia on it’s own. JIMK- Plus Quercetin is also an anti-inflammatory and free radical quencher. Dr. A- But the antichlamydial effect may be more important than it’s anti-inflammatory effect. JIMK- How much Quercetin do you use a day—I tend to take three caps with the bromelain. Dr. A- I tend to use 2 caps a day containing 500 mg of Quercetin along with vitamin C. Differences in treating different diseases? JIMK- Do you see differences in treatment based on disease entity, or more on the person. Dr. A- That’s hard to say. My generalization is that: the longer the person’s been sick and the sicker the person has been, the more problematic the therapy is going to be. In addition, the older the person is, the more likely that they’ve had a Cpn load building for a long time without knowing it. Their ability to tolerate treatment can be low, both from the high Cpn load, and from an aging immune system. On the other hand, I know of a young patient who had a very strong family history of cardiac disease. For this reason, his doctor placed him on the regimen. He had very few reactions. He was in his early 30’s. JIMK- He had some reactions, which let you know that he had some Cpn building. Dr. A- Yes. JIMK- I know in my family there’s both cardiac disease and Alzheimer’s, and another sibling has fibromyalgia. So there may be a common link genetically that is more about the susceptibility to Cpn. Dr. A- AOE4 probably has a place in Cardiac disease, Alzheimer’s and MS. I’ve observed that the recent memory problems that come with brain fog for patients can really lift once the Chlamydia is gone, even in those 50 or more. Porphyria JIMK- On the porphyrin stuff- do you think the porphyrin testing is worthwhile, or do you just assume it and treat for it anyway when you are treating for Cpn? Dr. A- The trouble is that you really have to test for the fat soluble porphyrins to get the best data, and that involves a 24-hour stool test, and you have to freeze that sample and so on. You need a 24-hour urine to look for water-soluble porphyrins. There is a poor man’s way to check for porphyrins. It seems that if you have porphyrins, you will have an increased hemoglobin level, on the high end of normal on most CBC’s. JIMK- when I was first treated I was very low on iron, which I understand is heavily used by chlamydial metabolism. Would that make a problem for using hemoglobin’s as an indicator of porphyrins? Dr. A- Initially, low iron would mask the increased hemoglobin you would expect with porphyrins. Once your iron levels are normal, it would no longer mask the elevated hemoglobin. But in general, a high-normal hemoglobin and high-normal hematocrit are both good indicators of porphyrins. JIMK- I can’t tell you how unusual it is to speak to a physician who sees it his or her job to actually investigate and reason out what’s going on in a patient, rather than look to see which already-known-box to put them in. I spoke to David Wheldon about that and he said, “Yes, I know, if I’d listened to those doctors I would be a widower now.” Kind of put home the point.  

Chlamydia pneumoniae infection of brain cells: an in vitro study

Submitted by mrhodes40 on Thu, 2007-07-19 10:46

Neurobiol Aging. 2007 Apr;28(4):524-32. Epub 2006 Apr 18.
Chlamydia pneumoniae infection of brain cells: an in vitro study.Boelen E, Steinbusch HW, van der Ven AJ, Grauls G, Bruggeman CA, Stassen FR.
Department of Medical Microbiology, CARIM (Cardiovascular Research Institute Maastricht), Maastricht University, Maastricht, The Netherlands.

Chlamydia pneumoniae directly interferes with HIF-1alpha stabilization in human host cells

Submitted by mrhodes40 on Sat, 2007-05-12 19:29

Chlamydia pneumoniae directly interferes with HIF-1alpha stabilization in human host cells.

Rupp J, et al

 Institute of Medical Microbiology and Hygiene, Center for Structural and Cell Biology in Medicine, University of Luebeck, 23538 Luebeck, Germany.

Essential Observations by Dr. Charles Stratton on Chlamydia Pneumoniae Infection and Disease

Submitted by Jim K on Tue, 2006-09-12 16:57

I am very excited to present the following article that summarizes Dr. Stratton's recent observations on Chlamydia pneumoniae infection. Putting it together has contributed greatly to my own understanding of Cpn as well as to my appreciation of Dr. Stratton's generosity with his time, and his great depth of knowledge of this area. Thanks to him for his contribution. Jim K Recent observations by Dr Recent observations by Dr. Charles Stratton on Chlamydia Pneumoniae (Cpn) Infection

Macrophage antioxidant enzymes regulate Chlamydia pneumoniae chronicity: Evidence of the effect of redox balance on host-pathoge

Submitted by mrhodes40 on Wed, 2006-06-07 13:14

Immunobiology. 2006;211(5):325-39. Epub 2006 Apr 18. Related Articles, Links

Macrophage antioxidant enzymes regulate Chlamydia pneumoniae chronicity: Evidence of the effect of redox balance on host-pathogen relationship.

Azenabor AA, Muili K, Akoachere JF, Chaudhry A.

Department of Health Sciences, University of Wisconsin, Enderis Hall, Room 469, 2400 E. Hartford Avenue, Milwaukee, WI 53211, USA.

Latency, chronicity and recurrent nature are the features of Chlamydia pneumoniae biology which play a central role in the course and outcome of C. pneumoniae-host interaction. Since redox status is directly an indicator of inflammatory response via molecular signaling mechanisms, we decided to study the regulatory role of macrophage cellular redox balance on the molecular indices of C. pneumoniae chronicity. We examined GSH-GSSG status, the activities of antioxidant enzymes (SOD, GPx and gamma-GCS), along with their protein and gene expression, the MOMP and cHSP-60 protein and gene expression, and the consequence of redox balance on the establishment of productive infection in macrophages. Results showed that C. pneumoniae caused changes in GSH-GSSG levels, antioxidant enzymes activity, mRNA gene and protein expression in macrophages. The relevance of this to the state and status of C. pneumoniae in macrophages was assessed by inhibitor induced attenuation of antioxidant enzymes and there was evidence that, while SOD attenuation did not significantly affect MOMP and cHSP-60 gene and protein expression, gamma-GCS attenuation increased cHSP-60 gene and protein expression. The increase in molecular evidence of chronic forms of C. pneumoniae (cHSP-60) was consistent with decrease in normal forms of C. pneumoniae. These findings reflect the importance of redox balance modulation on the outcome of C. pneumoniae infection in macrophages, a significant process in the pathogenesis of chlamydial diseases.

Chlamydia pneumoniae infection of brain cells

Submitted by Jim K on Sun, 2006-04-23 09:10

This pre-publication abstract is a remarkable piece of laboratory work. It strengthens the case for Cpn infection especially in MS and Alzheimer's, and other brain diseases. The two findings I've underlined which seem to have espeical importance is (1) the sensitivity of neuronal cells to infection, as big producers of EB's, and their particular sensitivity to necrosis (tissue death); and (2) the finding in microglial cells that they resist active replicating infection but appear to be potential reservoirs for persistant Cpn.

  Neurobiol Aging. 2006 Apr 16; [Epub ahead of print] Chlamydia pneumoniae infection of brain cells: An in vitro study.Boelen E, Steinbusch HW, van der Ven AJ, Grauls G, Bruggeman CA, Stassen FR.Department of Medical Microbiology, CARIM (Cardiovascular Research Institute Maastricht), Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands; Department of Cellular Neuroscience, EURON (European Graduate School of Neurosciences), Maastricht University, PO Box 616, 6200 MD Maastricht, The Netherlands.Inspired by the suggested associations between neurological diseases and infections, we determined the susceptibility of brain cells to Chlamydia pneumoniae (Cpn). Murine astrocyte (C8D1A), neuronal (NB41A3) and microglial (BV-2) cell lines were inoculated with Cpn. Infection was established by immunofluorescence and real-time PCR at various time points. Productive infection was assessed by transferring medium of infected cells to a detection layer. Finally, apoptosis and necrosis post-infection was determined. Our data demonstrate that the neuronal cell line is highly sensitive to Cpn, produces viable progeny and is prone to die after infection by necrosis. Cpn tropism was similar in an astrocyte cell line, apart from the higher production of extracellular Cpn and less pronounced necrosis. In contrast, the microglial cell line is highly resistant to Cpn as the immunohistochemical signs almost completely disappeared after 24h. Nevertheless, significant Cpn DNA amounts could be detected, suggesting Cpn persistence. Low viable progeny and hardly any necrotic microglial cells were observed. Further research is warranted to determine whether these cell types show the same sensitivity to Cpn in an in vivo setting.PMID: 16621171 [PubMed - as supplied by publisher]

Dr. Stratton Answers Some Questions:

Submitted by Jim K on Mon, 2006-01-30 22:13

In some recent correspondance with Dr. Stratton at Vanderbilt University, he kindly answered some of the questions which had formed as I've understood more about the combination antibiotic protocol and about Cpn. From the patient's perspective I wanted to correlate some observations about treatment reactions with his deeper understanding about the biology of the Cpn. I'll list the questions I put to him, and then his generous response below.1.  In an earlier correspondance you had mentioned pulsing the INH band metronidazole together.         * Why do that rather than take it continuously?        * My understanding is that INH is one of the anti-replicatives, and the point is to use these continuously to drive the bug into the cryptic phase where it will be obliterated by the flagyl/tini. Does INH act differently than the other antireplicatives?        * I also understood that we use a dual abx to prevent developing resistance. Why can we use INH alone without developing resistance? 

Expression and localization of type III secretion-related proteins of Chlamydia pneumoniae.

Submitted by mrhodes40 on Sat, 2005-12-31 18:39

What follows is a study sent to us by Dr Wheldon. Below I have pasted his comment about it...Marie
Med Microbiol Immunol (Berl). 2004 Nov;193(4):163-71. Epub 2003 Oct 31.

Expression and localization of type III secretion-related proteins of Chlamydia pneumoniae.

Lugert R, Kuhns M, Polch T, Gross U.

Department of Bacteriology, University of Gottingen, Kreuzbergring 57, 37075 Gottingen, Germany.

The entire developmental cycle of the obligate intracellular bacteria Chlamydia pneumoniae takes place within the inclusion body. As many gram negative bacteria, Chlamydia possess a type III-secretion system (TTSS), which allows them to target effector molecules into the host cell. The expression and localization of several proteins constituting the TTSS apparatus and of proteins supposed to be secreted by the TTSS have been investigated. For the TTSS-constituting proteins, we selected representatives such as YscN (ATPase), LcrE (putative "lid" of the TTSS) and LcrH1 (postulated to be a chaperone). Furthermore, we focused on the putative effector proteins IncA, IncB, IncC, Cpn0809 and Cpn1020. Expression of these proteins was detected by reverse transcriptase-PCR followed by immunoblot analysis using antisera that were generated against the corresponding recombinant proteins. Thereby, expression could be detected on the RNA and/or protein level. Intracellular localization of proteins under investigation was determined by immunofluorescence assays using the respective antisera. YscN was shown to be distributed equally throughout the inclusion body, whereas LcrE gave a more prominent staining of the inclusion membrane. IncA was detected mainly on the membrane of the inclusion body, whereas IncB and IncC were shown to be located within the inclusion. Immunofluorescence assays with antisera raised against Cpn0809 and Cpn1020 showed completely different labeling. Signals corresponding to Cpn0809 and Cpn1020 were distributed within the host cell rather than inside the inclusions. Taken together, the different localization patterns of the effector proteins indicate differences in function and interplay with the host cell.

Family Practice news article Persistence

Submitted by mrhodes40 on Mon, 2005-11-21 11:49

And Persistent Chlamydia - Brief Article
Family Pratice News, Nov 1, 2000
Found Here

Persistent chlamydia infection was identified in seven women with three or more recurrences over a 2- to 5-year time span, in a 10-year retrospective analysis of STD clinic samples.

Four of the women harbored the same genotype of Chlamydia trachomatis over the entire recurrence period, and the other three women had genotypes that mutated slightly, possibly due to drug therapy (J. Infect. Dis. 182[3]:909-16, 2000).

Cultures taken between flare-ups tested negative, but C. trachomatis DNA was detected in 59% of samples in the seven women vs. 14% in reinfected patients. Class C serovars were more likely to be implicated in the persisting strains.

Tryptophan depletion as a mechanism of gamma interferon-mediated chlamydial persistence

Submitted by mrhodes40 on Sun, 2005-11-20 12:12

Abstract found Here
Previous studies have shown that the immune-regulated cytokine gamma interferon (IFN-gamma) activates host cells to restrict intracellular growth of the bacterial pathogen Chlamydia trachomatis by induction of the tryptophan-catabolizing enzyme indoleamine 2,3-dioxygenase (IDO). Recently, subinhibitory levels of IFN-gamma were used to generate an in vitro persistent chlamydial infection characterized by large aberrant, noninfectious reticulate bodies from which infectious progeny could be recovered following the removal of IFN-gamma. Studies were done to determine if the mechanism functioning to induce chlamydiae to enter a persistent state in the presence of low levels of IFN-gamma was similar to that reported to inhibit chlamydial growth. Host cells treated with levels of IFN-gamma required to induce persistence were assessed for IDO activity by high-performance liquid chromatography analysis of tryptophan and its catabolic products. Substantial tryptophan catabolism was detected in acid-soluble cellular pools, indicating that the intracellular availability of this essential amino acid was limited under these conditions. In addition, a mutant cell line responsive to IFN-gamma but deficient in IDO activity was shown to support C. trachomatis growth, but aberrant organisms were not induced in response to IFN-gamma treatment. Analyses of infected cells cultured in medium with incremental levels of exogenous tryptophan indicated that persistent growth was induced by reducing the amount of this essential amino acid. These studies confirmed that nutrient deprivation by IDO-mediated tryptophan catabolism was the mechanism by which IFN-gamma mediates persistent growth of C. trachomatis.