Programme Hospitalier Recherche Clinique, Institut Pasteur, Inserm, French Public Health Agency.

Figure 1 Cytological appearance of trichomonad cells in stool culture (case 1). (A) Merthiolateiodine-formalin-and (B) RAL555-stained smears showing numerous trichomonad cells (arrows). Note the round shape of the micro-organisms. Typical microtubular cytoskeletal structures of trichomonads including flagella and axostyleepelta complex are not visible. Bar¼15 mm.Details have been removed from these case descriptions to ensure anonymity. The editors and reviewers have seen the detailed information available and are satisfied that the information backs up the case the authors are making.

A new Tetratrichomonas species was identified by molecular and phylogenetic approaches in the pleural fluid from a patient with encysted empyema leading to dyspnea. This observation raised the questions of the real prevalence of pulmonary trichomonosis in humans, the zoonotic potential of trichomonads, and the existence of human-host-adapted strains. CASE REPORTA 40-year-old woman was admitted to the emergency unit with a bacterial infection and a history of fever, fatigue, vomiting, and respiratory distress for 2 weeks before admission. On physical examination, the patient was irritable with dyspnea. Her vital signs were as follows: temperature, 39.2°C; blood pressure, 168/81 mm Hg; heart rate, 110 beats/min; respiration, 30 breaths/min. A chest X-ray followed by a computed tomography scan revealed encysted empyema of the right lung with a large pleural effusion (Fig. 1A). Foul-smelling and purulent pleural fluid was removed from the right chest cavity by thoracentesis. Examination of the pleural fluid showed numerous motile and flagellated protozoa, which were provisionally identified as trichomonads by their morphological characteristics, including form, size, and motility. These flagellates were not cultured, and their identification was confirmed by microscopic examination of May-Grünwald-Giemsa-and Merthiolateiodine-Formalin (MIF)-stained smears (Fig. 1B). Moreover, this pleural fluid was used for subsequent molecular characterization of these protozoa. Bacteriological cultures of the fluid yielded gram-positive cocci. On day 2, a chest tube was inserted for drainage of the right pleura and fibrinolytic therapy with urokinase, and mechanical ventilation was instituted. Pleural fluid was drained and was positive for Streptococcus constellatus and Streptococcus gordonii, both anaerobic and aerobic bacteria, and the anaerobic bacterium Prevotella sp. in addition to the trichomonad species mentioned above. Antibiotherapy with amoxicillin (amoxicilline) was continued, and treatment with metronidazole (Flagyl) was started. On day 10, the patient suffered from diarrhea with the emergence of Clostridium difficile. Hence, the use of metronidazole was delayed and the patient was treated with vancomycin per os in addition to amoxicillin. On day 18, a follow-up chest computed tomography scan showed partial clearing of the pleural effusion. Consequently, the patient did not require further surgical cleaning of the pleural cavity. On day 24, the patient was successfully weaned from the ventilator, and by day 26, her general health condition had improved and she presented neither fever nor dyspnea.In order to identify the trichomonad species involved in this case report, DNA was extracted from pleural fluid using the High Pure PCR template preparation kit (Roche Applied Science, Mannheim, Germany) according to the manufacturer's protocol. In a first step, the internal transcribed spacer 1 (ITS1)-5.8S rRNA-ITS2 region was amplified as described previously (6, 12). PCR was carried out with a 50-l volume according to the st...

2264 The alpha4 beta1 integrin (VLA-4) exert a critical role on hematopoiesis by confining hematopoietic stem cells (HSC) and progenitor cells (HPC) within the niche. Previous preclinical studies have pointed out this role showing that HPCs can be mobilized by in vivo administration of a blocking anti-VLA-4 antibody (Ab) (Papayannopoulou et al, 1993). Very recently, two papers (Bonig et al, 2008; Zohren et al, 2008) have shown that such Ab exhibits a similar effect in humans for one month after treatment by natalizumab. In the present study, we have investigated long-term hematopoietic effects (up to 23 months) of repeated infusions of natalizumab in patients treated for multiple sclerosis (n=22). Seven patients have been explored sequentially (every month for one year) and 15 have been studied punctually (6 before and 9 after one year of treatment). We found that peripheral blood leukocytosis was consistently increased for one year in relation to lymphocytes, particularly to B lineage (by 3-fold). In parallel, an increase of circulating HPCs (CD34+ cells and total CFU) was observed and appeared more pronounced with levels above baseline values in all the patients studied (by 6-fold) while no increase of circulating mesenchymal stromal cells (CFU-F) was found. The increase was noted for both lymphoid (T and B lineages) and myeloid (granulo-monocyte, erythroid, and megakaryocyte) committed progenitor cells but also for primitive HPC (CD34+CD38- cells and CAFC). This effect was still found at long-term (up to two years of treatment) for both committed and primitive HPC. In conclusion, the HPC mobilizing effect of chronic administration of anti-VLA-4 Ab in humans involves all types of HPCs (lymphoid and myeloid, committed and primitive ones) and is not exhausted with time. Disclosures: No relevant conflicts of interest to declare.