Comparison of vestipitant with ondansetron for the treatment of breakthrough postoperative nausea and vomiting after failed prophylaxis with ondansetron.

BACKGROUND: Postoperative nausea and vomiting (PONV) is common; ondansetron is often used as prophylaxis or for breakthrough episodes. Vestipitant is a neurokinin 1 (NK-1) receptor antagonist that is effective for prophylaxis, but its efficacy for treating established PONV is unknown. This study was performed to evaluate the efficacy and safety of vestipitant, compared with ondansetron for the treatment of breakthrough PONV in patients who had already received prophylactic ondansetron before surgery. METHODS: A multicentre, randomized, single-blind (sponsor-open), parallel group study. Of 527 surgical patients, 130 (25%) had breakthrough PONV and were equally randomized to one of six i.v. doses of vestipitant (4-36 mg) or ondansetron 4 mg. The primary endpoint was the rate of patients exhibiting complete response, defined as no emesis and no further rescue medication from 10 min after infusion up to 24 h after surgery or hospital discharge. RESULTS: All doses of vestipitant were non-inferior to ondansetron in treating PONV after failed prophylaxis with ondansetron. However, vestipitant was superior to ondansetron in decreasing episodes of postoperative emesis and retching. The complete response rate analysis using Bayesian model averaging indicated that no vestipitant dose was superior to ondansetron. Nausea numerical rating scale scores and the times-to-PONV or discharge were similar between the vestipitant and ondansetron treatment groups. CONCLUSIONS: Although overall efficacy was non-inferior between vestipitant and ondansetron, the rate of emesis was lower with vestipitant. These data suggest that vestipitant may be a useful agent for the management of PONV, similar to other NK-1 antagonists. CLINICAL TRIAL REGISTRATION: NCT01507194.

Strongyloides stercoralis host-adapted third-stage larvae are the target of eosinophil-associated immune-mediated killing in mice.

Host-adapted, transformed, Strongyloides stercoralis third-stage larvae (L3+) were previously found to be antigenically different from free-living, infective, third-stage larvae (L3). These antigenic differences were reproduced by transformation of free-living larvae in tissue culture medium at 37 C over 24 hr. Transformed L3 of both derivations were given as challenge infections in diffusion chambers to naive mice and mice immunized with S. stercoralis L3. Within 12 hr, the challenge infections were killed regardless of whether the L3+ were generated in vitro or in vivo. Eosinophils, previously found to be important in the immune response to S. stercoralis larvae, were recruited into the L3+ microenvironment within 12 hr of challenge infection in immune mice, which supports the previously proposed mechanisms of S. stercoralis larval killing. Thus, S. stercoralis L3+ appear to be targets of the immune response in mice instead of being involved in immune evasion.

Chronicity in Strongyloides stercoralis infections: dichotomy of the protective immune response to infective and autoinfective larvae in a mouse model.

Strongyloidiasis is an intestinal disease that can last for decades due to the occurrence of autoinfective larvae (L3a) in an infected person, which contribute to the maintenance of the population of adult worms in the intestine. The goal of the present study was to determine if L3a are susceptible to the protective immunity that targets the infective stage of the worm, the third-stage larvae (L3). Mice immunized and challenged with Strongyloides stercoralis L3 kill more than 90% of challenge larvae contained within diffusion chambers. The L3 do not remain antigenically static in mice, however, but undergo some degree of antigenic change before they are killed, becoming host-activated larvae (L3+). The L3/L3+ are killed in this model system by the combined effects of both parasite-specific IgM and eosinophils. Mice immunized with L3 were able to kill L3/L3+, but did not kill L3a, in challenge infections. Eosinophils were, however, present in diffusion chambers containing L3a, and IgM bound to the surface of L3a. We hypothesized that differential IgM recognition of soluble L3a, L3, and L3+ antigens is the reason why the immune response generated against L3 could not kill L3a. Many common antigens on L3, L3+, and L3a were recognized by serum from mice immunized with L3, as determined by immunoblotting. However, several unique L3, L3+, and L3a antigens were also recognized by immune serum, thus indicating that antigen recognition with IgM antibodies is different between the L3, L3+, and L3a stages. This difference in antigen recognition could explain why L3a are able to evade the immune response that targets L3/L3+ in chronically infected hosts.

Strongyloides stercoralis: eosinophil-dependent immune-mediated killing of third stage larvae in BALB/cByJ mice.

Challenge worm survival was significantly reduced when BALB/cByJ mice were vaccinated against Strongyloides stercoralis infective third stage larvae (L3) regardless of whether the challenge infections consisted of systemically migrating L3 or L3 implanted in diffusion chambers. The only cell type that increased in number in diffusion chambers in immunized mice, 1 week after booster immunizations, was the eosinophil, and maximal levels of eosinophils were coincident with parasite killing. Mice were treated with mAb to eliminate IL-5 or granulocytes to assess the role that eosinophils play in larval killing. Treated animals showed no decrease in immunity when challenge infections consisted of systemically migrating L3 administered 3 weeks after booster immunizations. Eosinophil numbers in immunized mice decreased to control levels when measured 3 weeks post-booster immunization, both in diffusion chambers and in the peripheral blood, whereas they were elevated at 1 week after booster immunizations. Direct contact between host cells and L3 was, however, still required for larval killing in immunized hosts 3 weeks after booster immunizations. Elimination of eosinophils by treatment with mAb to IL-5 or granulocytes significantly reduced protective immunity, when L3 were implanted in diffusion chambers at 1 and 3 weeks post-booster. However, as systemically migrating L3 were still killed in immunized, eosinophil-depleted animals, other cell types may play a role in larval destruction. Two human eosinophil granule products were found to be toxic for host-adapted L3+, but had no effect on infective L3, indicating that host-adapted larvae are possible targets for eosinophil-mediated destruction of third stage larvae. These findings suggest that inactivation of eosinophils by mAb treatment abolishes protective immunity to L3 contained within diffusion chambers and that small numbers of eosinophils are sufficient for immune-mediated killing of S. stercoralis L3.

Strongyloides stercoralis: role of antibody and complement in immunity to the third stage of larvae in BALB/cByJ mice.

Mice immunized against Strongyloides stercoralis L3 were shown to kill greater than 90% of challenge larvae contained within diffusion chambers. The objective of the present study was to identify the host components responsible for immunity. Serum from unprotected, control mice and protected, immune mice in doses of 25-500 microliters was transferred into naive mice at the same time and location as larval challenge. Transfer of as little as 50 microliters of immune serum was able to confer protective immunity. The serum-transferred immunity was ablated by excluding cells from the larval microenvironment or by depleting granulocytes through monoclonal antibody treatment in the recipient mice. Specific antibody isotypes were isolated using protein G and isotype-specific affinity columns. The resulting transfer experiments identified IgM as the isotype responsible for protective immunity to S. stercoralis L3. Antibody binding studies in vivo were performed and only IgM bound to the surface of infective L3 and host-derived L3 (L3+) in immune animals. Elevated levels of C3 were also found bound to the surface of L3/L3+ in immune mice. Cobra venom factor treatment of immunized mice to deplete complement completely eliminated C3 binding to the surface of L3/L3+ and ablated immunity. Therefore, IgM, complement, and granulocytes are necessary for immune elimination of S. stercoralis L3/L3+. Identification of antigens recognized by IgM may help select possible vaccine candidates.

Structural and molecular specificity of antibody responses in mice immune to third stage larvae of Onchocerca volvulus.

Immunization of mice with irradiated Onchocerca volvulus infective stage larvae (L3) has been demonstrated to confer protection against challenge infections with these larvae. Additionally, cytokine level measurements and cytokine depletion studies have shown that both IL-4 and IL-5 are important in generating a protective immune response against O. volvulus challenge infections, thus suggesting a dependency of protective immunity on IgG1, IgE and/or eosinophils. In the present study, we examined the humoral responses of immunized mice to O. volvulus L3 antigens. ELISA measurements of total serum antibody levels indicated that IgE was the only antibody isotype elevated in mice immunized with O. volvulus L3. IgM from immunized mice was the only isotype that recognized surface antigens on intact O. volvulus L3. IgG1, IgG3, IgE and IgA recognized internal parasite antigens on O. volvulus L3 frozen sections. Western blot analysis of L3 proteins showed that in serum from mice immunized with O. volvulus L3 IgG1, IgG2a/2b, IgA, and IgE, as well as IgM, recognized unique L3 proteins. Antibodies in serum from L3 immunized mice were able to detect O. volvulus adult antigens in a pattern similar to the recognition found in O. volvulus L3. Some L3 antigens were shared by adults, while other antigens were L3 specific. The ELISA, immunohistochemistry and Western blot findings thus demonstrate a complex pattern of antigen recognition of parasite antigens by antibodies found in mice immune to the L3 of O. volvulus.

Strongyloides stercoralis: protective immunity to third-stage larvae inBALB/cByJ mice.

A murine model system was developed to study the induction and mechanism of protective immunity to L3 of Strongyloides stercoralis. L3 were implanted in BALB/cByJ mice in diffusion chambers constructed with 0.1- or 2.0-microns-pore-size membranes. Parasites survived equally well regardless or membrane type for 7 days, after which larval survival decreased in diffusion chambers constructed with 2.0-microns-pore-size membranes, which allowed host cells to enter. Survival of S. stercoralis L3 in diffusion chambers implanted in mice was assayed after immunization with live, heat-killed, and homogenized L3. Optimal immunization was achieved with 10,000 live L3, whereby immunized mice eliminated 97% of the larvae either contained within diffusion chambers or free within the tissues of the mouse by 24 hr postinfection. Sera from immunized mice had elevated levels of IgG1, IgM, and IgA parasitic-specific antibody; IgM was the only antibody isotype that recognized surface antigens of L3. Larvae were not killed in immunized mice if contact between host cells and the parasites was prevented. In the peripheral blood and diffusion chamber fluid of immunized mice, eosinophil levels were significantly higher when compared to the levels found in control mice. The rodent model developed in the present study has thus demonstrated that virtually complete immunity can be induced to the L3 of S. stercoralis and that larval killing was found to be associated with the presence of both specific antibody and eosinophils.

Genetically engineered bacteria to identify and produce anti-viral agents.

We have prepared a strain of Escherichia coli that expresses both the HIV protease and a Tet protein which has been modified to contain the HIV protease recognition sequence. When the protease is expressed, the bacteria will not grow in the presence of tetracycline. However, when the protease is inhibited the bacteria can grow in tetracycline containing media (Block and Grafstrom 1990). We have selected spontaneously arising Tet resistant mutants and have screened them for those that could be producing an inhibitor of HIV protease. The problems in the construction of this strain and the characterization of the various Tetr mutants are discussed.