A Babesia bovis 225-kilodalton spherical-body protein: localization to the cytoplasmic face of infected erythrocytes after merozoite invasion.

A 225-kDa Babesia bovis protein occurs on the cytoplasmic side of infected-erythrocyte membranes. Here it is demonstrated that the 225-kDa protein localizes to spherical-body organelles of merozoites. Organelles consistent in size and shape with spherical bodies were isolated between 1.17 and 1.21 g/cm(3) in a sucrose density gradient. Organelles consistent with rhoptries and micronemes were also present in fractions from 1.17 to 1.19 g/cm(3). Antisera generated by immunizing mice with the fraction (1.20 to 1.21 g/cm(3)) most enriched for spherical bodies reacted predominantly with spherical bodies in B. bovis merozoites. A monoclonal antibody generated from this immunization (70/97.14) recognized an epitope that occurs in the repeat region of the 225-kDa protein (now referred to as SBP2). Monoclonal antibody 70/97.14 bound to merozoite spherical bodies, vesicles in infected-host cytoplasm, and the cytoplasmic face of the infected-erythrocyte membrane. These results indicate that spherical-body proteins become associated with the host membrane via transport through the erythrocyte cytoplasm after intracellular invasion.     

Multiple lethal effects induced by a benzimidazole anthelmintic in the anterior intestine of the nematode Haemonchus contortus

A mechanism of benzimidazole efficacy against parasitic nematodes is postulated to involve inhibition of intestinal secretory vesicle transport via depolymerization of microtubules. We show that fenbendazole (FBZ) treatment of lambs causes pathology localized to the anterior intestine in the parasitic nematode Haemonchus contortus. The pathology included gross disintegration of the anterior intestine, DNA fragmentation in anterior intestinal nuclei with characteristics of an apoptosis-like process, and inhibition of host erythrocyte digestion. These lethal effects were associated with inhibited transport of apical secretory vesicles in the anterior intestine, and then generalized dispersal of these vesicles contents throughout the intestinal cytoplasm and worm body. Cytoplasmic accumulation of secretory vesicles and undigested erythrocytes preceded DNA fragmentation and vesicle content dispersal. Both DNA fragmentation and vesicle content dispersal were detected in disintegrated intestine and intestine that had not yet undergone disintegration. These pathologic effects in the anterior intestine appear sufficient to explain the efficacy of FBZ against adult H. contortus. The results implicate mechanisms in the anterior intestine that govern dispersal of apical secretory vesicle contents, DNA fragmentation and tissue disintegration as effectors of this pathology.     

Strain variation of Babesia bovis merozoite surface-exposed epitopes.

Babesia bovis merozoites are exposed to antibodies during the extraerythrocytic phase, and surface polypeptides bearing exposed epitopes are possible immunogens. Monoclonal antibodies reactive with the merozoite surface bind either immunodominant epitopes expressed diffusely on the merozoite surface or, alternatively, epitopes expressed in a polar pattern. Epitopes expressed diffusely on the immunodominant 42- and 44-kDa merozoite polypeptides were not conserved among strains from geographically diverse regions. In contrast, epitopes expressed in a polar pattern on the merozoite surface were conserved among nine strains and clones. Identification of variables and conserved epitopes provides a basis for defining antigenic variation and cross-protective immunity.     

A 13-year molecular epidemiological analysis of tuberculosis in San Francisco.

BACKGROUND: We examined the molecular epidemiology of tuberculosis (TB) in San Francisco during a 13-year period encompassing the peak of TB resurgence and subsequent decline to historic low levels. OBJECTIVE: To compare rates of TB caused either by rapid progression of recent Mycobacterium tuberculosis infection or by reactivation of latent infection. METHODS: All TB cases reported from 1991 to 2003 were included. Genotyping was performed to identify clustered cases. RESULTS: The annual TB case rate decreased significantly from 50.8 to 28.8 cases/100000 persons from 1992 to 1999 (P < 0.0001). After 1999, no significant decrease was observed for the population as a whole or in any subgroup examined. Similarly, the rate of clustered cases decreased significantly from 1992 to 1999 (11.4 to 3.1 cases/100000, P < 0.0001). Although the rate of non-clustered cases also declined significantly (25.6 to 17.6 cases/100,000, P < 0.0001), there was a disproportionate reduction in clustered cases (94.7% vs. 50.8%, P < 0.0001). Neither clustered nor non-clustered cases decreased significantly after 1999. CONCLUSIONS: TB case rates reached a plateau despite ongoing application of control measures implemented in 1993. These data suggest that intensification of measures designed to identify and treat persons with latent TB infection will be necessary to further reduce TB incidence.     

Abomasal lymph node responses to Haemonchus contortus intestinal antigens established in kid goats by infection or immunization with intestinal antigens

Immune responses to Haemonchus contortus intestinal antigens were evaluated using abomasal lymph node (ALN) lymphocytes from kid goats protected against challenge infection by immunization with parasite intestinal antigen, and from kids that were challenged after immunization with ovalbumin. ALN lymphocytes from the intestinal antigen-immunized group produced significantly higher antibody levels against intestinal antigens than the ovalbumin group, supporting the theory that immunization contributed to that ALN response. In contrast, intestinal lysates and membrane enriched preparations from intestinal cells stimulated significant proliferation of ALN lymphocytes in both groups. The proliferation was antigen-dependent, since intestinal antigens failed to stimulate proliferation in ALN lymphocytes from unimmunized and uninfected kids. For both the intestinal antigen and ovalbumin immunized groups, CD4+ T lymphocytes predominated in ALN lymphocytes that were stimulated to proliferate by intestinal antigens. The results indicate that H. contortus infection alone can induce ALN lymphocyte responses to intestinal antigens. In contrast to ALN lymphocyte responses, serum antibody against intestinal antigens was generally low to undetectable in ovalbumin-immunized kids following infection. Abomasal mucus from an H. contortus infected lamb was probed with a monoclonal antibody that binds to a periodate sensitive determinant on numerous H. contortus intestinal membrane and secreted proteins. Numerous bands of reactivity were detected, indicating that multiple parasite intestinal antigens were released into abomasal mucus during infection. The results, challenge the general concept that H. contortus intestinal antigens are 'hidden' from the host immune system during an infection. On the contrary, parasite intestinal proteins may be relatively abundant antigens presented to the host during infection. In addition, ALN T lymphocytes appear to provide a more sensitive measure than serum antibody to detect presentation of these antigens to the host immune system.     

Noninvasive ventilation for acute respiratory failure

Noninvasive ventilation refers to any form of ventilatory support applied without the use of an endotracheal tube. It offers the potential to provide primary treatment for acute respiratory failure while avoiding complications associated with mechanical ventilation with endotracheal intubation. Noninvasive ventilation has been most commonly studied in hypercapnic respiratory failure. A review of randomized, controlled studies shows mixed results and methodologic limitations affect the interpretation of current evidence. Patient selection is clearly the most important issue in considering noninvasive ventilation for acute respiratory failure. Unfortunately, patients who benefit from noninvasive ventilation represent only a minority of the total group with any one disease, and thus it is difficult to make broad conclusions concerning applicability of this treatment modality. Future studies are needed to focus on determining the specific patient populations who will benefit the most, evaluating the optimal ventilatory mode and mask for providing noninvasive ventilation, and clarifying its impact on clinical outcomes. This revised version was published online in July 2006 with corrections to the Cover Date.