Mice compromised by a burn wound injury and subjected to a fatal infection with Pseudomonas aeruginosa were administered a single dose of a Pseudomonas aeruginosa phage cocktail consisting of three different P. aeruginosa phages by three different routes: the intramuscular (i.m.), subcutaneous (s.c.), or intraperitoneal (i.p.) route. The results of these studies indicated that a single dose of the P. aeruginosa phage cocktail could significantly decrease the mortality of thermally injured, P. aeruginosa-infected mice (from 6% survival without treatment to 22 to 87% survival with treatment) and that the route of administration was particularly important to the efficacy of the treatment, with the i.p. route providing the most significant (87%) protection. The pharmacokinetics of phage delivery to the blood, spleen, and liver suggested that the phages administered by the i.p. route were delivered at a higher dose, were delivered earlier, and were delivered for a more sustained period of time than the phages administered by the i.m. or s.c. route, which may explain the differences in the efficacies of these three different routes of administration.Pseudomonas aeruginosa plays a prominent role as an etiological agent of serious infections in patients with burn wounds. Acute burn wounds cause a breach in the protective skin barrier and suppress the immune system, rendering the patients highly susceptible to bacterial infection. P. aeruginosa colonization of severe burn wounds and its rapid proliferation within the damaged tissues often lead to disseminated infections, resulting in bacteremia and septic shock (8,20) and high rates of mortality and morbidity. Treatment of such infections is confounded by the innate and acquired resistance of P. aeruginosa to many antimicrobials (8,15). It has been estimated that at least 50% of all deaths caused by burns are the result of infection (8), and untreatable infections have become a tragically frequent occurrence in patients infected with P. aeruginosa (9). Hence, the development of new therapeutic and prophylactic strategies for the control of bacterial infection in patients with burn wounds is needed.An alternative or supplement to antibiotic therapy, which is currently being reexamined, is the use of bacterial viruses (phage/bacteriophage) to target bacterial infections, i.e., phage therapy (13, 16-18, 22, 29, 30-32). Soothill examined the ability of bacteriophage to prevent the rejection of skin grafts of experimentally infected guinea pigs (27). His findings demonstrated that the phage-treated grafts were protected in six of seven cases, while untreated grafts failed uniformly, suggesting that phage might be useful for the prevention of P. aeruginosa infections in patients with burn wounds. However, while multiple studies have demonstrated the benefits of phage therapy for a variety of bacterial infections in animal model systems (3-7, 10, 14, 19, 23-26, 33-35), little documentation exists with regard to the treatment of burn wound infections (2). In the study described ...

Infection with the parasitic nematode Trichinella spiralis is initiated when the L1 larva invades host intestinal epithelial cells. Monoclonal antibodies specific for glycans on the larval surface and secreted glycoproteins protect the intestine against infection. Protective antibodies recognize tyvelose which caps the target glycan. In this study, we used an in vitro model of invasion to further examine the mechanism(s) by which tyvelosespecific antibodies protect epithelial cells against T. spiralis. Using cell lines that vary in susceptibility to invasion, we confirmed and clarified the results of our in vivo studies by documenting three modes of interference: exclusion of larvae from cells, encumbrance of larvae as they migrated within epithelial monolayers, and inhibition of parasite development. Excluded larvae bear cephalic caps (C. S. McVay et al., Infect. Immun. 66:1941-1945, 1998) of immune complexes that may physically block invasion or may interfere with sensory reception. Monovalent Fab fragments prepared from a tyvelose-specific antibody also excluded larvae from cells, demonstrating that antibody binding can inhibit the parasite in the absence of antigen aggregation and cap formation. In contrast, encumbered larvae caused extensive damage to the monolayer yet were not successful in establishing a niche, as reflected by their failure to molt. These results show that antibodies to tyvelose exhibit multiple modes of inhibitory activity, further implicating tyvelose-bearing glycoproteins as mediators of invasion and niche establishment by T. spiralis.The parasitic nematode Trichinella spiralis has a wide host range which includes humans and over 100 other vertebrate species (10). T. spiralis infection is acquired by ingestion of muscle tissue containing L1 larvae. Enzymes in the acidic environment of the stomach free larvae from tissue, allowing them to initiate infection by invading columnar epithelial cells in the small intestine. Here, they rapidly undergo four molts, grow, and reproduce (10). Larval and adult stages localize to the crypt-villus junction, where they migrate in what appear to be epithelial syncytia (21,22). Establishment of T. spiralis in this intestinal habitat is crucial for successful completion of the life cycle.Although it has been known for many years that T. spiralis invades gut epithelium, the host-parasite relationship at this site is poorly understood. Our approach in investigating this relationship is based on the premise that the study of an effective host immune defense against a pathogen can reveal insights into the mechanisms of parasitism deployed by the agent. We have shown that niche establishment by T. spiralis is prevented in the rat by antibodies which are specific for L1 larval glycoproteins (1, 3). So-called rapid expulsion eliminates up to 100% of an oral dose of L1 larvae within hours of challenge (4, 9, 13, 15). Protective antibodies are specific for tyvelose (3,6-dideoxy-D-arabinohexose) which caps the antennae of tri-and tetra-antennary glycans shared by ...

No abstract

Trichinella spiralis is an obligate parasite of animals that has an unusual intracellular life cycle. Investigation of parasitism at the cellular and molecular levels has been challenging because of a shortage of tools for in vitro cultivation of T. spiralis. We have found that T. spiralis larvae molt, ecdyse, develop to adulthood, and reproduce when they are inoculated onto cultured intestinal epithelial cells. Initially, larvae invade and migrate through cells in a monolayer (T. ManWarren, L. Gagliardo, J. Geyer, C. McVay, S. Pearce-Kelling, and J. Appleton, Infect. Immun. 65:4806-4812, 1997). During prolonged culture in Caco-2 epithelial cells, L1 larvae molted and ecdysed with efficiencies as high as 50%. Molting and ecdysis in vitro required entry of the parasite into cells; conditions that prevented entry into cells also prevented ecdysis. When larvae were inoculated at a low density and cultured for 5 to 9 days, as many as 50% of the larvae developed to adult stages. Low numbers of mature male worms with copulatory appendages were observed in these cultures. The majority of worms that survived for five or more days were unfertilized females. Low-density cultures supported development of female worms with embryos at rates of 4 to 5%. These results show that the intestinal life cycle of T. spiralis can be supported entirely by host epithelial cells. Our model should allow more detailed investigation of intracellular parasitism by T. spiralis.