Cystic forms (also called spheroplasts or starvation forms) and their ability to reconvert into normal motile spirochetes have already been demonstrated in the Borrelia burgdorferi sensu lato complex. The aim of this study was to determine whether motile B. garinii could develop from cystic forms, not only in vitro but also in vivo, in cyst-inoculated mice. The cysts prepared in distilled water were able to reconvert into normal motile spirochetes at any time during in vitro experiments, lasting one month, even after freeze-thawing of the cysts. Motile spirochetes were successfully isolated from 2 out of 15 mice inoculated intraperitoneally with cystic forms, showing the infectivity of the cysts. The demonstrated capacity of the cysts to reconvert into motile spirochetes in vivo and their surprising resistance to adverse environmental conditions should lead to further studies on the role and function of these forms in Lyme disease.

The expression of the CD69 antigen on CD4 T lymphocytes after in vitro stimulation with purified protein derivative (2 tuberculin units) was used to evaluate the tuberculin reactivities of 52 individuals from four experimental groups: Mycobacterium bovis BCG-vaccinated healthy individuals with a negative tuberculin skin test (TST) result (group A), BCG-vaccinated healthy individuals with a positive TST result (group B), patients with active tuberculosis (TB) before treatment (group C), and individuals with clinically inactive TB who had previously completed a prescribed course of chemotherapy (group D). The expression of CD69 on CD4 T lymphocytes was significantly higher in patients with active TB (16.2% ؎ 7.3%), individuals with clinically inactive TB (10.5% ؎ 7.4%), and healthy individuals with a positive TST result (15.5% ؎ 7.2%) than in healthy individuals with a negative TST result (3.8% ؎ 4.3%) (P < 0.005). We confirmed the correlation between CD69 antigen expression on T lymphocytes after stimulation with tuberculin and the TST induration diameter (Spearman rho ‫؍‬ 0.783; P < 0.001), an assay for gamma interferon (the Quantiferon-TB assay; Spearman rho ‫؍‬ 0.613; P < 0.001), and the lymphocyte BLAST transformation test (Spearman rho ‫؍‬ 0.537; P < 0.001). Our results demonstrate the usefulness of the determination of CD69 on CD4 T lymphocytes after in vitro stimulation with tuberculin as a rapid indicator of immune sensitization against Mycobacterium tuberculosis.The fast, early, and accurate diagnosis of Mycobacterium tuberculosis infection is a very important element of global health measures for the control of tuberculosis (TB). The identification of individuals with latent M. tuberculosis infection (LTBI) who will benefit from treatment is crucial to the goal of TB elimination (1, 2). Since the immune response to mycobacterial infection is predominantly cellular (11), assessment of whether a patient's T cells have been exposed to and sensitized by antigens specific to M. tuberculosis provides an approach to diagnosis (4). Delayed-type hypersensitivity skin testing by the tuberculin skin test (TST) with purified protein derivate (PPD) is the standard method of screening for TB and has been a convenient, cost-effective method for assessment of the cell-mediated immune response to a tuberculin. Although TST has been the "gold standard" for diagnostic screening and the detection of new or asymptomatic TB, it has a number of drawbacks, including the need for a return visit to allow reading of the results, problems with interpretation of the test results due to cross-reactivity with other mycobacterial species, the booster effect, false-negative results due to intercurrent immunosuppression, and the variability inherent in its application and reading (16). In addition, it is imprecise and can give only a partial assessment of the interrelationships among M. tuberculosis, host macrophages, and the surrounding cellular components of the immune system, particularly CD4 T lymphocytes (5, 22). Different types of...