Although it is sympatric with tsetse flies, Stomoxys calcitrans is not a biological vector of trypanosomes. It is known that haemolymph (HL) and midgut reservoir zone (RH) lectins regulate parasitic infections in some dipteran insects. Agglutinins (lectins) were detected in HL and RH from unfed stable flies (maximum titre 2-6). Increased haemagglutination activity resulted post-feeding (maximum titre 2- 16 - 2- 18). Optimum titres varied according to agglutinogen type and mammalian blood source. Rabbit erythrocytes produced the highest haemagglutination titres followed by human group B, human group 0, horse, human group A, human group AB and sheep. Stomoxys haemagglutination activity was found to be 1.5 - 2.5 times stronger than that of Glossina. Whole blood-fed flies produced the highest titre (2-18), compared to glucose-fed insects, against rabbit erythrocytes. Anti-Trypanosoma brucei brucei titres ranged from 2-6 - 2-7 in both tissues. Similar results were obtained with Leishmania hertigi and Crithidia!asciculata. Purification of the samples was performed in order to draw conclusions with confidence regarding the physico-chemical properties of the agglutinins (lectins) and in order to determine the molecular weight of the agglutinins. Protein contents ofHL and RH samples of flies aged < 12 hours to 3 days were determined. They were 25 - 28 mg/ml and 6.4 mg/ml respectively. Protein contents increased with age reaching 32 mg/ml for HL and 7.2 mg/ml for RH at day 14 post-emergence (p.e.). The contents then started to decrease reaching 22 mg/ml for HL and 5.6 mg/ml for RIi at day 28 p.e. Purified lectins constitute 4.3% of the total protein contents in RH samples (having molecular weights of 26,302 Da, 16,218 Da and 14,028 Da) and, approximately twice, 9.47% of the total protein contents, in HL samples (having similar molecular weights of 28,300 Da, 16,218 Da and 14,600 Da). HL and RH anti-parasite and anti-erythrocyte agglutinins (lectins) were basic glycoproteins in nature, calcium ion dependent for activity, heat labile, freeze-thaw sensitive and required slightly acid to alkaline pH conditions for optimum agglutination. Lectins were specific for galactosyl and glucosyl moieties. In vivo sugar inhibition of RH lectin activity resulted in three-fold increased S. calcitrans mortalities post- T.b. brucei infection, compared to the controls, suggesting a lectin parasite-killing function. However, sugar inhibition of lectins did not lead to transformation of trypanosomes to procyclic forms or to infection of the fly.

No description available.

No description available.

Abstract In social insects a major cost of social life is the high number of pathogens found in large societies and the greater likelihood of transmission of pathogens among closely related individuals. The aim of this thesis was to investigate the effect of high pathogen pressure on the molecular evolution of genes involved in the innate immune system in social insects. In addition, the transmission dynamics of the intracellular bacteria Wolbachia in wood ants was examined. By comparing DNA sequences from diverse species of ants and honeybees it was shown that the immune genes in hymenopteran social insects have evolved rapidly. However, by using codon-based likelihood models of evolution positive selection was detected in only two ant genes. This may reflect behaviourally based colony-level defences that can reduce selective pressure on the immune genes. The transmission modes of Wolbachia were studied by comparing DNA sequence variation of the bacteria with that of the host ants. First, it was found that all the studied ants carry Wolbachia. Second, Wolbachia have been transmitted both vertically from mother to offspring and horizontally between individuals of the same as well as of different species. / Tiivistelmä Yhteiskuntahyönteisten (muurahaiset, ampiaiset, mehiläiset ja termiitit) ekologisen menestyksen kääntöpuolena on ollut jatkuva riesa taudinaiheuttajista, joita suurissa yhteisöissä tavataan runsaammin kuin yksittäin elävissä eliöissä. Taudinaiheuttajien tuoman paineen myötä yhteiskuntahyönteisille on kehittynyt käyttäytymiseen perustuvia puolustusmekanismeja täydentämään kaikille monisoluisille eliöille yhteistä synnynnäistä, fysiologista immuniteettia. Nämä puolustusmekanismit ovat todiste siitä, että taudeilla on ollut suuri merkitys yhteiskuntahyönteisten käyttäytymisen evoluutiossa. Toisaalta taudinaiheuttajien vaikutuksista synnynnäiseen immuunipuolustukseen tiedetään hyvin vähän. Väitöstutkimuksen ensisijainen kohde oli taudinaiheuttajien merkitys yhteiskuntahyönteisten synnynnäisen immuunipuolustuksen evoluutiossa. Tutkimuksessa tarkasteltiin, miten immuunijärjestelmän geenit ovat ajan mittaan muuttuneet. Tulokset osoittivat että muutoksia, jotka johtavat proteiinien aminohappojen vaihtumiseen on tapahtunut tiuhempaan tahtiin muurahaisilla ja mehiläisillä kuin yksittäin elävällä banaanikärpäsellä. Merkkejä erityisen voimakkaasta luonnonvalinnasta löydettiin kuitenkin yllättävän pienestä määrästä geenejä. Tämä voi johtua siitä, että käyttäytymiseen perustuvat puolustusmekanismit lieventävät taudinaiheuttajien vaikutusta synnynnäiseen immuunipuolustukseen. Väitöstutkimukseen sisältyi myös hyönteisten solunsisäisen bakteerin, Wolbachian, siirtymismekanismien kartoitus kekomuurahaisilla. Wolbachia on loinen, joka siirtyy yleensä äidiltä jälkeläisille munasolussa. Leviäminen voi tapahtua myös horisontaalisesti lajitoverien ja jopa eri lajien edustajien kesken. Geenisekvensseihin perustuvassa tutkimuksessa kaikista muurahaisista löytyi Wolbachia-bakteereja, ja samasta yksilöstä saattoi löytyä useaa eri bakteerikantaa. Koska muurahaislajien väliset geneettiset erot olivat paljon suurempia kuin erot niissä elävien bakteerien välillä, voitiin päätellä että bakteerien pääasiallinen leviämistapa tutkituilla muurahaisilla on ollut horisontaalinen.

<p>Medonosna pčela (Apis mellifera&nbsp; Linnaeus, 1758) je &scaron;iroko rasprostranjena vrsta iz grupe socijalnih insekata, glavni opra&scaron;ivač mnogih divljih biljaka i poljoprivrednih kultura. Pored njene primarne uloge u opra&scaron;ivanju, koristi se i za dobijanje pčelinjih proizvoda, pre svega meda, voska&nbsp; i propolisa,&nbsp; čime se dodatno nagla&scaron;ava njen privredni značaj. Uzimajući u obzir značaj medonosne pčele, a sa druge strane aktuelan problem pada broja kolonija, postoji potreba za razumevanje uzroka&nbsp; i&nbsp; procenu&nbsp; rizika koji leže u osnovi ovog kompleksnog problema. Stoga, istraživanja u ovoj doktorskoj disertaciji obuhvataju praćenje biohemijskih i fiziolo&scaron;kih parametara kod medonosne pčele kao pokazatelja stanja pčelinjih zajednica tokom letnjeg i zimskog perioda&nbsp; na stani&scaron;tima sa različitim antropogenim uticajem.&nbsp; U prvoj fazi istraživanja su izvedeni akutni laboratorijski testovi izlaganja&nbsp; medonosne pčele&nbsp; subletalnim dozama pesticida, tiakloprida i klotianidina, a dobijeni rezultati su&nbsp; ukazali&nbsp; na naru&scaron;enu neurotransmisiju, na izmene u aktivnosti antioksidativnih enzima i redoks statusa u ćeliji, kao i na imunosupresiju.&nbsp; U drugoj fazi istraživanja su analizirane kolonije&nbsp; medonosne pčele sa različitih lokaliteta&nbsp; na području AP Vojvodine, sa primenom stacionarnog i migratornog tipa pčelarenja, tokom letnjeg i zimskog perioda, a dobijeni rezultati su ukazali&nbsp; na značajne razlike&nbsp; u biohemijskom odgovoru medonosne pčele u zavisnosti od starosti pčela, sezone godine i tipa pčelinjaka. Na osnovu rezultata prethodne dve faze istraživanja, izvr&scaron;en&nbsp; je&nbsp; odabir uzoraka, kao i izbor parametara za&nbsp; treću fazu&nbsp; istraživanja,&nbsp; gde&nbsp; je praćeno stanje medonosne pčele&nbsp; iz stacionalnih pčelinjih zajednica, tokom letnjeg&nbsp; aktivnog perioda, kao i početkom&nbsp; i&nbsp; krajem&nbsp; zimskog perioda&nbsp; mirovanja pčela, sa tri lokaliteta u Republici Srbiji sa različitim stepenom urbanizacije i industrijalizacije: Beograd kao urbano, Susek kao ruralno i Zajača kao industrijsko područje. Dobijeni rezultati su ukazali na&nbsp; značajne razlike u zavisnosti od sezone&nbsp; godine, kao i&nbsp; lokaliteta sa različitim antropogenim uticajem.&nbsp; Zimske pčele, krajem perioda mirovanja&nbsp; u odnosu na početak mirovanja,&nbsp; karakteri&scaron;e vi&scaron;i&nbsp; nivo antioksidativne za&scaron;tite, udružen sa&nbsp; visokim&nbsp; stepenom&nbsp; oksidativnih o&scaron;tećenja, zatim&nbsp; bolja imunokompetencija, kao i niske energetske rezerve u masnom telu.&nbsp; Sezonskim povećanjem temperatura tokom godine povećava se sadržaj zasićenih, dok se smanjuje udeo nezasićenih masnih kiselina, gde se oleinska 18:1(9) kiselina izdvaja kao dominantna komponenta u ukupnom sadržaju masnih kiselina masnog tela&nbsp; pčela&nbsp; sa sve tri lokacije, tokom sva tri perioda.&nbsp; Niži nivo ukupnih ugljovodonika je jo&scaron; jedna fiziolo&scaron;ka karakteristika zimskih pčela. Takođe, zapažene su promene&nbsp; i&nbsp; u neurotransmisiji holinergičkog tipa tokom sezone, sa vi&scaron;im aktivnostima acetilholinesteraze kod pčela krajem zime i tokom leta.&nbsp; Metabolomičkom analizom hemolimfe pčela je&nbsp; identifikovano&nbsp; 125 metabolita, uključenih u 36 metaboličkih puteva, gde se kao biomarkeri od značaja za razlikovanje letnjih i zimskih pčela izdvajaju&nbsp; metaboliti u metabolizmu glicerolipida i aminokiseline glicin, cistein, glutamin, fenilalanin, prolin i lizin.&nbsp; Poređenjem dobijenih rezultata između različitih lokaliteta,&nbsp; pčele iz Beograda se izdvajaju sa nižim nivoom oksidativnog stresa,&nbsp; nižim aktivnostimaacetilholinesteraze, kao i fenol oksidaze i glukoza oksidaze, ključnih enzima u imunom odgovoru pčela. Pčele iz Suseka su se izdvojile sa najvećom masom masnog tela, &scaron;to ukazuje na dobre nutritivne i energetske rezerve u pčelama tokom zime i leta, dok se Beograd izdvaja sa značajno vi&scaron;im udelom nezasićenih masnih kiselina&nbsp; u masnom telu pčela.&nbsp; Takođe su zabeležene razlike u relativnoj zastupljenosti&nbsp; n-alkana u pčelama sa različitih lokaliteta, te je u Beogradu najzastupljeniji nonakozan&nbsp; (C29), dok je heptakozan (C27) najzastupljeniji u uzorcima pčela iz Suseka i Zajače.&nbsp; Analizom sadržaja metala u pčelama, pergi i medu, zapažamo da svaku sredinu karakteri&scaron;e specifičan profil zagađenja,&nbsp; kao i da je u medu znatno niža koncentracija svih analiziranih metala.&nbsp; Dobijeni rezultati pružaju dobru osnovu za dalja ispitivanja biolo&scaron;kog odgovora medonosne pčele, u pogledu uticaja faktora okruženja, a time i dalje definisanje odgovarajućih mera za&scaron;tite pčelinjih zajednica.</p> / <p>The&nbsp; honey&nbsp; bee&nbsp; (Apis&nbsp; mellifera&nbsp; Linnaeus,&nbsp; 1758)&nbsp; is&nbsp; a&sbquo;widespread&nbsp; social&nbsp; insect&nbsp; species&nbsp; and&nbsp; the&nbsp; main pollinator of various wild plants and agricultural crops.In addition to its primary role in pollination, the honey bee&nbsp; is&nbsp; also&nbsp; used&nbsp; for&nbsp; obtaining&nbsp; honeybee&nbsp; products, mostly honey, wax, and propolis, with a significant role in&nbsp; the&nbsp; economy.&nbsp; Number&nbsp; of&nbsp; honey&nbsp; bee&nbsp; colonies&nbsp; is declining,&nbsp; thus&nbsp; necessitating&nbsp; the&nbsp; assessment&nbsp; of underlying&nbsp; reasons&nbsp; and&nbsp; risks.&nbsp; Therefore,&nbsp; in&nbsp; this doctoral&nbsp; dissertation,&nbsp; biochemical&nbsp; and&nbsp; physiological parameters&nbsp; in&nbsp; the&nbsp; honey&nbsp; bee&nbsp; were&nbsp; monitored&nbsp; as indicators&nbsp; of&nbsp; the&nbsp; colonies&rsquo;&nbsp; condition&nbsp; during&nbsp; the summer&nbsp; and&nbsp; winter&nbsp; period&nbsp; in&nbsp; habitats&nbsp; with&nbsp; different anthropogenic&nbsp; impacts.&nbsp; In&nbsp; the&nbsp; first&nbsp; phase&nbsp; of&nbsp; the research,&nbsp; acute laboratory tests of honey bee exposure to&nbsp; sublethal&nbsp; doses&nbsp; of&nbsp; pesticides&nbsp; (thiacloprid&nbsp; and clothianidin)&nbsp; were performed and the obtained results indicated&nbsp; impaired&nbsp; neurotransmission,&nbsp; changes&nbsp; in&nbsp; the activity of antioxidant enzymes, and redox status in the cell,&nbsp; as&nbsp; well&nbsp; as&nbsp; immunosuppression.&nbsp; In&nbsp; the&nbsp; second phase&nbsp; of&nbsp; the&nbsp; research,&nbsp; honey&nbsp; bee&nbsp; colonies&nbsp; from different&nbsp; localities&nbsp; in&nbsp; the&nbsp; area&nbsp; of&nbsp; AP&nbsp; Vojvodina&nbsp; were analyzed,&nbsp; using&nbsp; the&nbsp; stationary&nbsp; and&nbsp; migratory&nbsp; types&nbsp; of beekeeping, during the summer and winter period, and the obtained results indicated significant differences in the&nbsp; biochemical response of the honey bee depending on the age of the bees, the season of the year, and the type of apiary. Based on the results of the previous two phases&nbsp; of&nbsp; the&nbsp; research,&nbsp; the&nbsp; selection&nbsp; of&nbsp; samples&nbsp; was performed,&nbsp; as&nbsp; well&nbsp; as&nbsp; the&nbsp; selection&nbsp; of&nbsp; parameters&nbsp; for analysis within the third phase of the research, where the&nbsp; condition&nbsp; of&nbsp; honey&nbsp; bees&nbsp; from&nbsp; stationary&nbsp; bee communities was monitored during the summer active period,&nbsp; as&nbsp; well&nbsp; as&nbsp; the&nbsp; beginning&nbsp; and&nbsp; end&nbsp; of&nbsp; winter dormancy of bees, from three localities in the Republic of&nbsp; Serbia&nbsp; with&nbsp; different&nbsp; degrees&nbsp; of&nbsp; urbanization&nbsp; and industrialization: Belgrade as urban, Susek as rural and<br />Zajaca&nbsp; as&nbsp; industrial&nbsp; area.&nbsp; The&nbsp; obtained&nbsp; results indicated&nbsp; significant&nbsp; differences&nbsp; depending&nbsp; on&nbsp; the season&nbsp; of&nbsp; the&nbsp; year,&nbsp; as&nbsp; well&nbsp; as&nbsp; the&nbsp; location&nbsp; with different&nbsp; anthropogenic&nbsp; influence.&nbsp; Older&nbsp; winter&nbsp; bees are&nbsp; characterized&nbsp; by&nbsp; a&nbsp; higher&nbsp; level&nbsp; of&nbsp; antioxidant protection,&nbsp; associated&nbsp; with&nbsp; a&nbsp; high&nbsp; degree&nbsp; of&nbsp; oxidative damage,&nbsp; better&nbsp; immunocompetence,&nbsp; as&nbsp; well&nbsp; as&nbsp; lowenergy reserves in the fat body. The seasonal increase in&nbsp; the&nbsp; temperature&nbsp; during&nbsp; the&nbsp; year&nbsp; increases&nbsp; the content&nbsp; of&nbsp; saturated&nbsp; while&nbsp; decreasing&nbsp; the&nbsp; ratio&nbsp; of unsaturated&nbsp; fatty&nbsp; acids,&nbsp; where&nbsp; oleic&nbsp; 18:1(9)&nbsp; acid stands&nbsp; out&nbsp; as&nbsp; the&nbsp; dominant&nbsp; component&nbsp; in&nbsp; the&nbsp; total fatty&nbsp; acid&nbsp; content&nbsp; of&nbsp; bee&nbsp; body&nbsp; fat&nbsp; from&nbsp; all&nbsp; three locations,&nbsp; during&nbsp; all&nbsp; three&nbsp; periods.&nbsp; The&nbsp; lower&nbsp; level&nbsp; of total&nbsp; hydrocarbons&nbsp; is&nbsp; another&nbsp; physiological characteristic&nbsp; of&nbsp; winter&nbsp; bees.&nbsp; Also,&nbsp; changes&nbsp; in cholinergic&nbsp; neurotransmission&nbsp; were&nbsp; observed&nbsp; during the&nbsp; season,&nbsp; with&nbsp; higher&nbsp; acetylcholinesterase&nbsp; activities in&nbsp; bees&nbsp; in&nbsp; late&nbsp; winter&nbsp; and&nbsp; summer.&nbsp; Metabolomic analysis of bee hemolymph identified 125 metabolites,included in 36 metabolic pathways, where metabolites in&nbsp; the&nbsp; metabolism&nbsp; of&nbsp; glycerolipids&nbsp; and&nbsp; amino&nbsp; acids glycine,&nbsp; cysteine,&nbsp; glutamine,&nbsp; phenylalanine,&nbsp; proline, and&nbsp; lysine&nbsp; stand&nbsp; out&nbsp; as&nbsp; biomarkers&nbsp; of&nbsp; importance&nbsp; for distinguishing summer and winter bees. By&nbsp; comparing the obtained results between different localities, honey bees&nbsp; from&nbsp; Belgrade&nbsp; stand&nbsp; out&nbsp; with&nbsp; lower&nbsp; levels&nbsp; of oxidative&nbsp; stress,&nbsp; lower&nbsp; activities&nbsp; of acetylcholinesterase&nbsp; as&nbsp; well&nbsp; as&nbsp; phenoloxidase&nbsp; and glucose oxidase, key enzymes in the immune response of&nbsp; bees.&nbsp; The&nbsp; honey&nbsp; bees&nbsp; from&nbsp; Susek&nbsp; had&nbsp; the&nbsp; largest mass of the fat body, which indicates good nutritional and&nbsp; energy&nbsp; reserves&nbsp; in&nbsp; bees&nbsp;&nbsp; during&nbsp; winter&nbsp; and summer,&nbsp; while&nbsp; the&nbsp; honey&nbsp; bees&nbsp; from&nbsp; Belgrade&nbsp; were shown&nbsp; to&nbsp; have&nbsp; a&nbsp; significantly&nbsp; higher&nbsp; ratio&nbsp; of unsaturated&nbsp; fatty&nbsp; acids&nbsp; in&nbsp; the&nbsp; fat&nbsp; body&nbsp; of&nbsp; bees&nbsp; during the&nbsp; year.&nbsp; There&nbsp; were&nbsp; also&nbsp; differences&nbsp; in&nbsp; the&nbsp; relative prevalence&nbsp; of&nbsp; n-alkanes&nbsp; in&nbsp; honey&nbsp; bees&nbsp; from&nbsp; different localities, nonacosane (C29) being the most common in Belgrade, while heptacosane (C27) is most prevalent in honey&nbsp; bee&nbsp; samples&nbsp; from&nbsp; Susek&nbsp; and&nbsp; Zajaca.&nbsp; By analyzing the metal content in honey bees, perga, and honey,&nbsp; it&nbsp; was&nbsp; noted&nbsp; that&nbsp; each&nbsp; environment&nbsp; is characterized by a specific pollution profile, as well as that the concentration of all analyzed metals in honey is significantly lower compared to samples of bees and perga.&nbsp; The&nbsp; obtained&nbsp; results&nbsp; provide&nbsp; a&nbsp; good&nbsp; basis&nbsp; for further studies of the biological response of&nbsp; the honey bee,&nbsp; in&nbsp; terms&nbsp; of&nbsp; the&nbsp; influence&nbsp; of&nbsp; the&nbsp; environmental factors,&nbsp; enabling&nbsp; further&nbsp; defining&nbsp; of&nbsp; appropriate measures for the protection of honey bee colonies.</p>

The variation in the insect immune system is an important regulator of insect populations and the pathogens they carry. A central component of insect immunity is melanin, whose production creates cytotoxic intermediates that help to protect against a broad spectrum of pathogens. Melanin is also used in insect cuticle where it helps to improve thermoregulation and desiccation resistance, with insects having less melanized cuticles in warmer and more humid environments. Considering that cuticle melanin and immune melanin are formed by near identical biochemical pathways, they are pleiotropically linked (that is, one or more linked genes influence multiple traits). This has lead to the cuticle-dependent immune investment (CDII) hypothesis, which states that adaptive responses in the cuticle can lead to non-adaptive changes in immunity and could lead to an increase in transmission of insect vectored pathogens in warming climates, due to a weaker defense against the pathogen. However, the impact of CDII on cuticle melanin and immunity, as well as infection prevalence and intensity, under seasonal conditions in the field is still unclear. In this project, we study a population of Asian citrus psyllids, Diaphorina citri, in the field over four seasons. Diaphorina citri vectors a Gram-negative bacteria, Candidatus Liberbacter asiaticus (CLas), that is responsible for Huanglongbing, aka citrus greening disease, which has cost the Florida citrus industry several billion dollars. We assess pathogen load of CLas by quantitative PCR, and assess levels of phenoloxidase activity in the insect hemolymph to measure insect immune function. We assess levels of cuticle melanin. Our results show a significant correlation between temperature, cuticle melanin, and immune function. However, the affect of seasonality on infection prevalence and intensity remains unclear. THE EFFECT OF CLIMATE ON PHYSIOLOGY AND IMMUNE FUNCTION IN THE ASIAN CITRUS PSYLLID, DIAPHORINA CITRI

Aedes aegypti mosquitoes, vectors for many human diseases, begin life as larvae developing in water, potentially exposed to runoff with herbicides and pesticides. This study serves as a novel investigation into the transstadial effects of exposure to Roundup on A. aegypti life history, immunity, and stress response and aims to account for these effects in an R0 model for vectorborne disease transmission. Prior work has shown that Roundup negatively affects mosquito life history. I hypothesized that larval exposure to the maximum sublethal dose of Roundup (7189µg/L) would negatively impact A. aegypti life history, immunity (candidate gene approach), and stress response (heat shock protein expression and fluctuating asymmetry). No significant differences were found for survival from the larval to adult stages, body size, size or shape fluctuating asymmetry, or sex ratio. However, the Roundup treatment group developed significantly slower for both time to pupation and to adult eclosion (both p < 0.0001). Adult immune gene expression showed no difference between groups, but the larval immune genes Dome (JAK-STAT pathway) and Spatzle (TOLL pathway) were downregulated in the Roundup treatment (p=0.0383 and p=0.0035, respectively), suggesting the larvae have reduced immunity. This study suggests that Roundup may have off-target effects on A. aegypti mosquitoes that are unaccounted for by current models, and these effects may potentially alter disease transmission to human hosts.

The Gram-negative bacterium Photorhabdus luminescens is a pathogen of insects. It is able to secrete a variety of toxins and effectors against its host in order to escape its immune defences. The model insect Manduca sexta is able to mount a variety of humoral and cellular responses against pathogen attack. Ultimately these prove ineffective against P. luminescens. The pre-treatment of M. sexta with Escherichia coli provides protection against the pathogenesis of P. luminescens. Here, I use RNA interference and Fluorescence-assisted cell sorting techniques to investigate interactions between pathogen and host to further elucidate the roles of various host factors in mounting the immune response. I also investigate the nutrient requirements of the bacteria for pathogenesis. I show data that peptidoglycan recognition protein (PGRP) is essential for the up-regulation of antimicrobial peptides, an important immune defence. I also show that P. luminescens has a requirement for two types of iron during pathogenesis of M. sexta. And lastly I show that P. luminescens is able to avoid phagocytosis, another important immune defence.

Le transfert trans-générationnel d’immunité (TTGI) est défini comme étant une élévation de l’immunocompétence de la descendance suite à la rencontre des femelles avec un organisme pathogène. Le TTGI est un phénomène bien connu chez les vertébrés, chez lesquels il se réalise par le transfert d’anticorps de la mère au jeune. Il n’a été décrit que récemment chez les invertébrés, chez lesquels le support de sa transmission est encore inconnu. Le TTGI apporte un bénéfice aux descendants lorsqu’ils rencontrent l’infection vécue par la mère, dans quel cas l’élévation de leur immunocompétence a un effet protecteur. Cependant, au-delà de ce bénéfice, plusieurs indices suggèrent que le TTGI est un phénomène coûteux pour les organismes. L’évolution du TTGI ne sera permise chez une espèce que lorsque les bénéfices qu’il représente en termes de protection des descendants surpasseront les coûts qu’il représente pour eux en termes de fitness. Ainsi, l’étude de ses coûts et de ses bénéfices nous renseigne sur les pressions de sélection qui ont conduit à son évolution chez les invertébrés. Au cours de cette thèse, j’ai associé l’expression du TTGI chez un insecte avec un certain nombre de coûts, tant pour les femelles qui le réalisent que pour les descendants qui l’expriment. Pour ce faire, j’ai utilisé comme organisme modèle le ver de farine, Tenebrio molitor. Dans le premier chapitre, nous avons stimulé le système immunitaire des femelles adultes de T. molitor avec un immunogène non pathogène, et étudié divers aspects de la transmission d’activité antibactérienne aux œufs qui en résultait. Cela nous a permis de voir que la transmission d’activité antibactérienne interne aux œufs commençait deux jours après la stimulation du système immunitaire des femelles et cessait après dix jours. Enfin, nous avons pu mettre en évidence un coût pour les femelles à la protection de leurs œufs, en termes de fécondité. Dans le second chapitre, nous stimulé le système immunitaire avec trois microorganismes différents tués par la chaleur, et exposé leurs jeunes larves à des microorganismes vivants. Nous n’avons pas réussi à mettre en évidence d’effet protecteur du TTGI sur les jeunes larves de T. molitor. Il s’avère cependant que l’exposition des jeunes larves à un champignon entomopathogène réduit le délai avant leur seconde mue larvaire. Dans le troisième chapitre, nous avons stimulé soit le système immunitaire des femelles, soit celui des mâles de T. molitor avec un immunogène non pathogène, et observé différents paramètres de l’immunité de leurs descendants adultes. Cela nous a permis de mettre en évidence que le TTGI d’origine maternelle et paternelle n’affecte pas les mêmes effecteurs immunitaires chez les descendants, et que le TTGI d’origine maternelle comportait un coût pour eux en termes de temps de développement. Ces coûts au TTGI suggèrent qu’il n’est pas seulement une conséquence de la stimulation du système immunitaire des femelles de la génération parentale, mais qu’il est bien un mécanisme qui a été sélectionné du fait des bénéfices qu’il représente pour les organismes dans certaines conditions écologiques / Trans-generational immune priming (TGIP) is defined as the plastic enhancement of offspring's immunocompetence following an immune challenge of the females of the parental generation. In vertebrates, this phenomenon is well described, and is achieved by the maternal transfer of antibodies. In invertebrates however, it has only recently been described. Since invertebrates do not possess antibodies, the mechanism of this transmission remains unknown. If the offspring is exposed to the maternal infection, an elevated immunocompetence can help it cope better with it. Nonetheless, apart from this benefit, several cues indicate that the TGIP bears some fitness costs for individuals. The evolution of TGIP will be favoured when its benefits outweigh its fitness costs. Thus, studying its costs and benefits can lead us to a better understanding of the selection pressures that lead to its evolution in invertebrates. During my thesis, I associated the occurrence of TGIP in an insect, the mealworm beetle Tenebrio molitor, to several fitness costs for the females transmitting it as well as for the offspring receiving it.In the first chapter, we stimulated the adult female's immune system with a non pathogenic immunogene, and studied several aspects of the subsequent transfer of antibacterial activity to the eggs. We saw that the transmission of antibacterial activity inside the eggs started two days after the immune challenge, and stopped at ten. Then, we highlighted a cost for the females on their fecundity to this transmission.In the second chapter, we stimulated the immune system of the females with three different heat-killed microorganisms, and exposed their larval progeny to living microorganisms. We did not see any benefit of the TGIP on the young larvae of T. molitor. However, we saw that the exposure of young larvae to an entomopathogenic fungus decreased the time-lap between the two first larval moults.In the third chapter, we stimulated the immune system of either the adult females or the males of T. molitor, and we observed several immune parameters in their adult offspring. This allowed us to see that maternally and paternally-derived TGIP affected different immune effectors in the adult offspring, and that maternally-derived TGIP bear a cost on the developmental time of the offspring.These fitness costs to the TGIP suggest that it is not just a side-effect of the immune reaction of the females, but rather an investment that has been selected because of the benefits it represents for the offspring in certain ecological conditions

>Magister Scientiae - MSc / Tsetse flies (Glossina spp) are vectors of African trypanosome (Trypanosoma spp) parasites, causative agents of Human African trypanosomiasis (sleeping sickness) and Nagana in livestock. Research suggests that tsetse fly immunity factors are key determinants in the success and failure of infection and the maturation process of parasites. An analysis of tsetse fly immunity factors is limited by the paucity of genomic data for Glossina spp. Nevertheless, completely sequenced and assembled genomes of Drosophila melanogaster, Anopheles gambiae and Aedes aegypti provide an opportunity to characterize protein families in species such as Glossina by using a comparative genomics approach. In this study we characterize thioester-containing proteins (TEPs), a sub-family of immunity-related proteins, in Glossina by leveraging the EST data for G.morsitans and the genomic resources of D. melanogaster, A. gambiae as well as A.aegypti.A total of 17 TEPs corresponding to Drosophila (four TEPs), Anopheles (eleven TEPs) and Aedes aegypti (two TEPs) were collected from published data supplemented with Genbank searches. In the absence of genome data for G. morsitans, 124 000 G.morsitans ESTs were clustered and assembled into 18 413 transcripts (contigs and singletons). Five Glossina contigs (Gmcn1115, Gmcn1116, Gmcn2398, Gmcn2281 and Gmcn4297) were identified as putative TEPs by BLAST searches. Phylogenetic analyses were conducted to determine the relationship of collected TEP proteins.Gmcn1115 clustered with DmtepI and DmtepII while Gmcn2398 is placed in a separate branch, suggesting that it is specific to G. morsitans.The TEPs are highly conserved within D. melanogaster as reflected in the conservation of the thioester domain, while only two and one TEPs in A. gambiae and A. aegypti thioester domain show conservation of the thioester domain suggesting that these proteins are subjected to high levels of selection. Despite the absence of a sequenced genome for G. morsitans, at least two putative TEPs where identified from EST data.