The shedding of Coxiella burnetii in bovine, caprine, and ovine milk was measured using PCR, in 3 herds for each species, the bulk tank milk samples of which were positive at the time of their selection. Milk samples of 95 cows, 120 goats, and 90 ewes were sampled over 16 wk, as was the bulk tank milk. The shedding of C. burnetii in vaginal mucus and feces was checked at the beginning of the experiment and 2 mo later. The clinical signs in the selected herds as well as the duration and the shedding routes differed among the 3 species. The cows were asymptomatic and shed C. burnetii almost exclusively in milk. In one of the caprine herds, abortions due to C. burnetii were reported. The goats excreted the bacteria mainly in milk. In contrast, the ewes, which came from flocks with abortions due to Q fever (C. burnetii infection), shed the bacteria mostly in feces and in vaginal mucus. This could explain why human outbreaks of Q fever are more often related to ovine flocks than to bovine herds. These excretions did not seem more frequent when the samples were taken close to parturition. The samples were taken from 0 to 421 d after parturition in bovine herds and from 5 to 119 d and 11 to 238 d after parturition in the caprine and ovine herds, respectively. The shedding in milk was sometimes intermittent, and several animals shed the bacteria but were negative by ELISA: 80% of the ewes were seronegative, underscoring the lack of sensitivity of the ELISA tests available for veterinary diagnosis. The detection of antibodies in milk seems more sensitive than it is in serum.

SummaryEscherichia coli is the leading cause of urinary tract infections, but the mechanisms governing renal colonization by this bacterium remain poorly understood. We investigated the ability of 13 E. coli strains isolated from the urine of patients with pyelonephritis and cystitis and normal stools to invade collecting duct cells, which constitute the first epithelium encountered by bacteria ascending from the bladder. The AL511 clinical isolate adhered to mouse collecting duct mpkCCD cl4 cells, used as a model of renal cell invasion, and was able to enter and persist within these cells. Previous studies have shown that bacterial flagella play an important role in host urinary tract colonization, but the role of flagella in the interaction of E. coli with renal epithelial cells remains unclear. An analysis of the ability of E. coli AL511 mutants to invade renal cells showed that flagellin played a key role in bacterial entry. Both flagellum filament assembly and the motor proteins MotA and MotB appeared to be required for E. coli AL511 uptake into collecting duct cells. These findings indicate that pyelonephritis-associated E. coli strains may invade renal collecting duct cells and that flagellin may act as an invasin in this process.

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-Mice were intramuscularly immunized with a dnaK-encoding DNA plasmid. The protective effect of DNA immunization against Chlamydophila abortus infection was studied in pregnant and non-pregnant mice models. In non-pregnant mice, the dnaK vaccine induced a specific humoral response with the predominant IgG2a isotype, which failed to have in vitro neutralizing properties. No delayed-type hypersensitivity reaction was observed and the spleens of dnaK vaccinated-mice were not protected against C. abortus challenge. In pregnant mice, the dnaK vaccine induced a non-specific partial protection from abortion. This may be due to the immunogenic properties of the CpG motifs of bacterial DNA present in the vaccinal plasmid backbone. Nevertheless, spleens of dnaK vaccinated-pregnant mice were not protected. DNA immunization / Chlamydophila abortus / DnaK / Hsp70Résumé -Évaluation de la protection induite par vaccination ADN avec un plasmide codant pour dnaK contre une épreuve par Chlamydophila abortus chez des souris gestantes ou nongestantes. Des souris ont été immunisées par l'injection intramusculaire d'un plasmide codant pour la protéine DnaK. L'effet protecteur de la vaccination ADN contre une infection par Chlamydophila abortus a été évalué dans des modèles de souris gestantes ou non-gestantes. La vaccination ADN avec le gène dnaK induit une réponse humorale spécifique chez les souris non-gestantes avec une prédo-minance d'IgG2a qui n'ont pas présenté d'activité neutralisante in vitro. Aucune réaction d'hypersensibilité retardée n'a été observée et les rates des souris vaccinées avec le vaccin ADN-dnaK n'ont pas été protégées contre l'infection par C. abortus. Chez les souris gestantes, le vaccin ADN-dnaK ré-duit partiellement et de façon non spécifique les avortements. Les îlots CpG de l'ADN bactérien, connus pour leur propriétés immunogéniques, pourraient être responsables de cet effet protecteur non spécifique. Cependant, aucune élimination des bactéries n'a été observée dans les rates des souris gestantes.vaccination ADN / Chlamydophila abortus / DnaK / Hsp70 313 Vet. Res. 33 (2002) 313-326

The protective effect of DNA vaccination with the gene encoding the major outer-membrane protein (MOMP) of Chlamydophila abortus has been studied in non-pregnant and pregnant mouse models after chlamydial challenge. OF1 outbred mice were vaccinated intramuscularly three times every 3 weeks, mated and challenged with C. abortus 2 weeks after the last injection of DNA. In nonpregnant mice, the MOMP DNA vaccine elicited a specific humoral response with predominantly IgG2a antibodies, suggesting a Th1-type immune response. The induced antibodies showed no in vitro neutralizing effect on C. abortus infectivity. Moreover, immunization with the momp gene showed no reduction in the mean splenic bacterial counts of non-pregnant or pregnant mice or in the mean placental bacterial counts of pregnant mice after the C. abortus challenge. Nevertheless, the MOMP DNA immunization induced a non-specific and partial protection in fetuses against challenge. INTRODUCTIONOne of the most common causes of considerable loss in breeding is the abortion of goats and sheep induced by the intracellular obligate bacterium Chlamydophila abortus (Chlamydia psittaci serotype 1) (Papp & Shewen, 1996). Furthermore, these bacteria present a zoonotic risk to pregnant women, since several cases of human chlamydial abortion have been reported (Buxton, 1986). A live attenuated vaccine is currently used in small ruminants (Rodolakis, 1983). This vaccine is effective and safe but does not allow the detection of infected animals in vaccinated flocks.The predominant component and immunodominant antigen of the Chlamydiaceae surface membrane, the 40 kDa major outer-membrane protein (MOMP), presents four surface-exposed variable domains (VDI-VDIV) flanked by five conserved regions and exhibits an oligomeric form, probably trimeric, that functions as a porin (De Sa, 1996). In a murine model of C. abortus infection, protective immunity can be conferred by antibodies (Buzoni-Gatel et al., 1990) and, more particularly, by the passive transfer of specific antibodies to the 110 kDa oligomeric MOMP (De Sa et al., 1995), so MOMP has been considered as the most likely vaccine candidate against C. abortus infections. Native MOMP (Pal et al., 1997;Tan et al., 1990), recombinant MOMP (Tuffrey et al., 1992), synthetic MOMP peptides and live recombinant vectors (Murdin et al., 1995) expressing momp genes from members of the Chlamydiaceae have been evaluated in different animal models. Limited immunity and protection were generated in animals when the vaccinal approaches attempted to preserve the conformational structure of MOMP. Nevertheless, most trials were unsuccessful. A recent study showed that protective immunity against a Chlamydia trachomatis genital challenge was induced with a vaccine based on the MOMP associated with lipophilic immune response-stimulating complexes (Igietseme & Murdin, 2000).DNA vaccination represents an exciting means to induce specific immunity to a single antigen and, consequently, fits in the marker vaccine family (van Oirschot et al., 19...