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Infective Larvae (infective + larva)
Selected AbstractsTransmission dynamics of lymphatic filariasis: vector-specific density dependence in the development of Wuchereria bancrofti infective larvae in mosquitoesMEDICAL AND VETERINARY ENTOMOLOGY, Issue 3 2006L. C. SNOW Abstract The principles of meta-analysis developed in a previous study were extended to investigate the process of Wuchereria bancrofti (Cobbold) (Filarioidea: Onchocercidae) infection in mosquito (Diptera: Culicidae) hosts, focusing specifically on the functional forms and strength of density dependence in the development of ingested microfilariae (mf) to infective (third instar) larvae (L3). Mathematical models describing observed mf,L3 functional responses for each of the major three parasite-transmitting vector genera, Aedes, Culex and Anopheles mosquitoes, were fitted to paired mf,L3 data collated from all available studies in the published literature. Model parameters were estimated and compared by deriving and applying a data synthetic framework, based on applying a non-linear weighted regression model for fitting mathematical models to multistudy data. The results confirm previous findings of the existence of significant between-genera differences in the mf,L3 development relationship, particularly with regard to the occurrence of limitation in Culex mosquitoes and facilitation in Aedes and Anopheles mosquitoes. New and unexpected findings regarding L3 development from ingested mf were discovered as follows: (1) for Culex, overcompensation in L3 development at higher intensities of mf (or a peaked mf,L3 functional response) was detected; (2) for Aedes mosquitoes, facilitation (with an apparent asymptotic constraint on L3 development at high mf densities) was shown to be the major process governing L3 development, and (3) for Anopheles, a stronger facilitation type of response with no apparent saturation in L3 development appears to govern L3 output from ingested mf. These results yield major new insights regarding filarial vector infection dynamics and their potential impacts on parasite control, and demonstrate the efficacy of employing a data synthetic approach to reveal and estimate parasitic infection processes in host populations. [source] Characterization of IgE responses in a rodent model of filariasis and the allergenic potential of filarial antigens using an in vitro assayPARASITE IMMUNOLOGY, Issue 1 2003Susanne Hartmann SUMMARY Filarial infections are characterized by high IgE antibody responses. So far, it is not clear whether IgE antibodies are involved in protection, pathology or both. We established a bioassay to detect reactive IgE antibodies in jirds infected with the filaria Acanthocheilonema viteae. Sera of A. viteae -infected jirds were used to sensitize rat basophil leukaemia (RBL) cells and degranulation was stimulated by addition of antigens of A. viteae. Reactive IgE responses were detected from 2 weeks post infection (p.i.) and throughout the A. viteae infection. Male antigen triggered the strongest mediator release, followed by female worms, infective larvae (L3) and microfilariae. Separation of male and female antigen indicated that several antigens of both genders are potent allergens. In particular, one male specific allergen of about 550 kDa induced strongest degranulation of RBL cells. In addition, mediator release stimulated by antigen fractions of about 15 kDa was due to filarial cystatin. In conclusion, we describe a convenient in vitro assay to examine IgE mediated responses in jirds. A sex specific filarial protein with high allergenic potential is identified and cystatin is established as a potent allergen of A. viteae. [source] Cellular responses to Loa loa experimental infection in mandrills (Mandrillus sphinx) vaccinated with irradiated infective larvaePARASITE IMMUNOLOGY, Issue 4 2000Ungeheuer In order to shed light on the mechanisms of antifilarial protective immunity, we investigated the course of experimental loaiosis after vaccination in a nonhuman primate host, Mandrillus sphinx. Six vaccinated (V) mandrills received 50 irradiated L3 while six nonvaccinated (NV) received saline solution on days ,60, ,30 and ,15. All animals were challenged with 100 intact L3 (day 0). Parasitological and immunological status were followed for 9 months. Vaccination delayed the appearance and mean peak of microfilaraemia. Five mandrills (Mf,) were never microfilaraemic (one V mandrill) or microfilaraemic on only one occasion (2 V and 2 NV), the other seven having stable microfilaraemia (Mf+). The cytokine response of peripheral blood mononuclear cells to L3 (L3 Ag) was Th2 dominated, while microfilariae (Mf Ag) elicited a Th0-like response. During vaccination, Th2 cytokine production significantly increased in V mandrills against L3 Ag, as well as Mf Ag, whereas Th1 cytokines decreased. On day 60 postinoculation, cellular proliferation was higher in V mandrills in response to L3 and Mf Ags and PHA-L mitogen. At the end of prepatency (on day 130), mandrills with delayed appearance of microfilaraemia exhibited a high, transient IL-2 and IL-4 secretion in response to L3 Ag. Finally, high anti-Mf Th2 cytokine levels characterized Mf,mandrills not only during prepatency, but also (for IL-5) before immunization. However, the presence of a balanced Th1 anti-L3 response during prepatency in the amicrofilaraemic mandrill suggests its importance in protective immunity. Taken together, our data suggest that Th2 cells and also Th1 components of the antifilarial response, especially to larval antigen, may contribute to parasite elimination. [source] Crystallization and preliminary X-ray analysis of Na-SAA-2 from the human hookworm parasite Necator americanusACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 2 2010Oluwatoyin A. Asojo Human hookworms are among the most pathogenic soil-transmitted helminths. These parasitic nematodes have co-evolved with the host and are able to maintain a high worm burden for decades without killing the human host. However, it is possible to develop vaccines against laboratory-challenge hookworm infections using either irradiated third-state infective larvae (L3) or enzymes from the adult parasites. In an effort to control hookworm infection globally, the Human Hookworm Vaccine Initiative, a product-development partnership with the Sabin Vaccine Institute to develop new control tools including vaccines, has identified a battery of protein antigens, including surface-associated antigens (SAAs) from L3. SAA proteins are characterized by a 13,kDa conserved domain of unknown function. SAA proteins are found on the surface of infective L3 stages (and some adult stages) of different nematode parasites, suggesting that they may play important roles in these organisms. The atomic structures and function of SAA proteins remain undetermined and in an effort to remedy this situation recombinant Na-SAA-2 from the most prevalent human hookworm parasite Necator americanus has been expressed, purified and crystallized. Useful X-ray data have been collected to 2.3,Å resolution from a crystal that belonged to the monoclinic space group C2 with unit-cell parameters a = 73.88, b = 35.58, c = 42.75,Å, , = 116.1°. [source] Immunoprophylactic evaluation of a 37-kDa Brugia malayi recombinant antigen in lymphatic filariasisCLINICAL MICROBIOLOGY AND INFECTION, Issue 4 2006P. Dabir Abstract The Brugia malayi filarial antigens recognised preferentially by sera from an endemic normal population are considered to be potential vaccine candidates. By immunoscreening the cDNA library of the infective L3 stage of B. malayi with pooled endemic normal sera, a cDNA clone Bm-SL3 was identified. Analysis of sera from different patient groups with the rBm-SL3 protein showed it to be highly reactive with endemic normal sera compared to its reactivity with microfilaraemic and non-endemic normal sera. The immunoprotective efficacy of the rBm-SL3 antigen against B. malayi filarial infection was evaluated in susceptible host jirds (gerbils) (Meriones unguiculatus). Jirds immunised with the rBm-SL3 antigen showed 68% cytotoxicity against microfilariae and 67,69% cytotoxicity against infective larvae in in-vitro antibody-dependent cellular cytotoxicity assays and in-situ micropore chamber methods. Analysis of IgG subclasses against Bm-SL3 revealed a significant increase in IgG1 and IgG2 antibodies in endemic normal sera compared with other groups. Lymphocyte proliferation to Bm-SL3 was significantly higher in the endemic normal group compared with that in clinical and microfilarial carriers (p < 0.001). Significantly enhanced levels of IFN-, in the culture supernatant of peripheral blood mononuclear cells of endemic normal sera after stimulation with Bm-SL3 suggest that the cellular response in this group may have a Th1 bias. [source] | ||||||||||