Immune responses, larvae

Another interesting observation is that several species of filarial nematodes have been shown to express chitinase (Fuhrman, 1995). Indeed the chitinase of A. viteae infective stage larvae (L3) is the main target of the protective humoral immune response when jirds are vaccinated with irradiated attenuated L3s (Adam et al., 1996 see also Chapter 10). It remains to be established whether there is an interaction between the parasite s oligo-chitin A-glycans and chitinase and whether such an interaction has a role to play in parasite-host interaction. 

Since 2002, on-line nanoscale LC-ESI-MS/MS was used for the analysis of the peptidome of. Drosophila samples. This combination greatly improves the sensitivity of detection. Starting from only 50 larval Drosophila CNS, 28 peptides were isolated and sequenced in an on-line quadrupole time-of-flight mass spectrometer [27]. Later, two-dimensional capillary LC-ESI-MS/MS has enhanced the coverage of this peptidomics analysis with the identification of twenty additional peptides [31]. The CNS extract has been first fractionated onto a strong cation-exchange column then onto a reversed-phase column before ESI-MS/MS analysis. Recently this approach has been applied to Drosophila larvae hemolymph to identify new peptides induced by a septic injury [22]. Most of the identified molecules correspond to truncated forms or propeptides of known AMPs and DIMs [15,20,21], but two previously unknown peptide precursors, potentially involved in the innate immune response, have been also detected by this way. 

Jenkins SJ, Hewitson JP, Jenkins GR. Modulation of the host s immune response by schistosome larvae. Parasite Immunol 2005 27 385-393. 

Du Pasquier, L, Ontogeny of the immune response in animals having less than one million lymphocytes the larvae of the toad Alytes ohstetricans. Immunology 19, 353-362 (1970). 

To determine what cells make the immune-specific RNA we inoculated mid-third instar Drosophila larvae with bacteria and six hours later dissected them into fat bodies and fat body-free carcass. Total RNA was collected, separated by electrophoresis, transfered to nitrocellulose, and probed with labelled Pool 1 oligonucleotide. The results showed (Fig. 5) that intact inoculated larvae accumulate the immune-specific transcript while intact control larvae do not. The tissue dissection experiment showed that fat body cells of inoculated larvae contain transcripts homologous to the immune-specific probe, but the carcass does not. We conclude that fat body cells in Drosophila larvae accumulate a transcript that has homology to sarcotoxin when they have been inoculated with bacteria. We are currently cloning the responsible immune gene. 

Initial anti-insect vaccine studies often yielded contradictory results 131). Crude antigen extracts wctc used and variable responses to immunization would be expected 14). This situation is similar to early efforts to induce anti-tick immunity with whole tick or tissue extracts 127). Fortunately, there is continued interest in vaccines against hematophagous insects and myiasis larvae, and promising results are being obtained 155, 24, 156,157,158,159, 160). 

Myiasis is the invasion of tissues or open body cavities by fly, dipteran, larvae. Myiasis can be caused by fly larvae of many different species. Vaccine based control of myiasis is very appealing. Fly larvae can reside in direct contact with elements of the host immune system for months. Not unexpectedly, natural infections do not generally induce inflammatory responses 190) or host iimnunity to re-infestation 191). The most extensively studied causes of myiasis are the warble flies, Hypoderma bovis and Hypoderma lineatum, and the sheep blowfly, Lucilia cuprina 24). 

Immunization induced protection must take into account the ability of L. cuprina to counteract host immunity. Excretory/secretory products of larvae reduce antibody responses 203) and secreted larval enzymes degrade C3 204) and IgG 205). 

Ivermectin (Fig. 25.18) is used to treat onchocerciasis, which is a disease caused by a nematode which is transmitted via the bite of a black fly. The bite injects the larvae under the skin of the host where they mature into adults in nodules, thus evading the host s immune system. The adults mate and produce larvae which are responsible for the strong inflammatory response of the host which causes acute dermatitis, and if the larvae migrate into the cornea of the eye this causes blindness - river blindness. ... 

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