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Dans le cadre de leur module « Analyse scientifique », les étudiants du Master 2 « Immunothérapies et Bio-ingénierie » de Sorbonne Université, ont pris la plume pour partager avec les lecteurs de m/s quelques uns des faits marquants de la littérature 2018 dans le domaine de l’immunologie. Les travaux présentés ici nous rappellent l’importance des études mécanistiques portant sur les grandes fonctions des composants du système immunitaire (lymphocytes T CD8+ cytotoxiques, lymphocytes T auxiliaires, lymphocytes T régulateurs, etc.) pour mieux comprendre la pathogenèse de certaines maladies et pour optimiser les stratégies thérapeutiques existantes. Cette année, deux brèves s’intéressent aux immunothérapies fondées sur l’utilisation d’anticorps dirigés contre des points de contrôle immunitaire : comment prédire la réponse clinique des patients à ces traitements grâce à des techniques de bioinformatique et de modélisation ? Comment améliorer leur efficacité en ciblant des facteurs de régulation épigénétique ? Une troisième brève apporte un éclairage sur les raisons expliquant pourquoi certains patients infectés par le virus du VIH et traités avec des anti-viraux ne parviennent pas à récupérer un taux normal de lymphocytes T CD4+. Enfin, une dernière brève s’intéresse, dans un modèle de diabète de type I, à une population particulière de lymphocytes T CD8+ cytotoxiques qui régulent d’autres lymphocytes T autoréactifs et limitent ainsi la réaction inflammatoire dans les organes. Bonne lecture !

ClpP and ClpC are subunits of the Clp ATP-dependent protease, which is ubiquitous among prokaryotic and eukaryotic organisms. The role of these proteins in stress tolerance, stationary-phase adaptive responses, and virulence in many bacterial species has been demonstrated. Based on the amino acid sequences of the Bacillus subtilis clpC and clpP genes, we identified one clpC gene and two clpP genes (designated clpP1 and clpP2 ) in Bacillus thuringiensis. Predicted proteins ClpP1 and ClpP2 have approximately 88 and 67% amino acid sequence identity with ClpP of B. subtilis , respectively. Inactivation of clpC in B. thuringiensis impaired sporulation efficiency. The clpP1 and clpP2 mutants were both slightly susceptible to salt stress, whereas disruption of clpP2 negatively affected sporulation and abolished motility. Virulence of the clp mutants was assessed by injecting bacteria into the hemocoel of Bombyx mori larvae. The clpP1 mutant displayed attenuated virulence, which appeared to be related to its inability to grow at low temperature (25°C), suggesting an essential role for ClpP1 in tolerance of low temperature. Microscopic examination of clpP1 mutant cells grown at 25°C showed altered bacterial division, with cells remaining attached after septum formation. Analysis of lacZ transcriptional fusions showed that clpP1 was expressed at 25 and 37°C during the entire growth cycle. In contrast, clpP2 was expressed at 37°C but not at 25°C, suggesting that ClpP2 cannot compensate for the absence of ClpP1 in the clpP1 mutant cells at low temperature. Our study demonstrates that ClpP1 and ClpP2 control distinct cellular regulatory pathways in B. thuringiensis .

Trichogramma brassicae Bezdenko is used throughout Europe as an effective biological control agent against the European corn borer (Ostrinia nubilalis Hubner). However, in certain climatic regions, the biological control exerted by this parasitoid is less effective. High temperatures inside the released capsules are suspected to have a negative influence on the parasitoids. To simulate these adverse conditions, we applied heat shocks (35°C and 44°C) for 6 hours to pupae ofTrichogramma brassicae at two periods: white pupae and melanized pupae. The results showed the susceptibility of both the white pupae and melanized pupae, especially at 44°C. At this temperature, the adults (G0 generation) derived from pupae treated at any age showed reduced longevity and fecundity. Moreover, those descended from treated melanized pupae showed an emergence rate lower than that of the control. These effects reduced to half and more the parasitic efficiency of the G0 generation. For the progeny (G1 generation), we observed a decrease of the female ratio: 38% for the progeny of adults derived from treated melanized pupae; 88% for the progeny of those derived from treated white pupae. In that condition, the G1 generation, almost totally male, could not have any parasitic activity.

Summary In order to explain and predict yield losses caused by European corn borer larvae, Ostrinia nubilalis Hbn. (Lepidoptera: Pyralidae), a mechanistic model was proposed to describe cavity appearance, their lengthwise extension, and their within-plant distribution. It integrates main dynamical processes of larvae: mortality, development and within-plant distribution. After its estimation and test under field conditions in 1988 and 1989, its validation, based upon X-ray photographs, is presented. This method allows cavity appearance and lengthwise extension to be followed without damaging the plants. This study confirms the relevance of the damage model and the rate of cavity lengthwise extension estimated with it.

In the presence of an extract of Ostrinia nubilalis or Mamestra brassicae eggs, female Trichogramma brassicae exhibited increased rates of upwind locomotion in the tubes of a linear olfactometer. GC and GC-MS analyses of O. nubilalis and M. brassicae egg extracts revealed the presence of fatty acids, their ethyl esters, and various hydrocarbons. Exposing the wasps to a mixture of the five main saturated hydrocarbons (heneicosane, tricosane, pentacosane, heptacosane and nonacosane) increased the upwind progression in the olfactometer. Single hydrocarbons elicited reduced or no activity. Ethyl palmitate and palmitic acid were also effective in increasing upwind locomotion. Z11-14: Ac, the main component of the female sex pheromone of O. nubilalis was inactive, regardless of its concentration. It is concluded that various compounds present on the surface of the O. nubilalis egg masses may play a role in the orientation of T. brassicae to its host. Resume En presence d'un extrait superficiel d'oeufs d'Ostrinia nubilalis, ou de Mamestra brassicae, les femelles du parasitoide Trichogramma brassicae presentent une tendance accrue a la remontee du tube dans un olfactometre lineaire. L'analyse des extraits d'oeufs par chromatographie en phase gazeuse couplee a la spectrometrie de masse revele la presence d'acides gras, de leurs esters ethyliques, et de divers hydrocarbures. Un melange des principaux hydrocarbures satures (heneicosane, tricosane, pentacosane, heptacosane et nonacosane) declenche egalement une remontee plus rapide et plus importante du tube. Chacun de ces hydrocarbures pris isolement presente une activite nulle ou reduite. D'autres constituants des extraits, l'acide palmitique et son ester ethylique, presentent egalement une certaine activite. En revanche, le Z11-14: Ac, constituant majoritaire de la pheromone sexuelle d'O. nubilalis, est inactif, quelle que soit la dose utilisee. En conclusion, divers constituants presents a la surface des oeufs de la pyrale du mais modifient le comportement locomoteur de femelles de T. maidis et pourraient done jouer un role dans l'orientation de ce parasitoide vers son hote.

Volatile chemicals emanating from the different developmental stages of Ostrinia nubilalis Hübner (Lepidoptera, Pyralidae) increase the mobility of Trichogramma brassicae Bezdenko (Hymenoptera, Trichogrammatidae) in a linear airflow olfactometer. In this paper, we have demonstrated that airborne chemicals from egg masses and virgin females during calling activity stimulate an intensive search behavior byTrichogramma females. On the other hand, emanations from mated females with extruded abdominal tips do not incite the parasitoid''s movement. For the moment we cannot elucidate, with these bioassays, the real role of these kairomones as attractants, guides, stimulants, or retainers.

Summary The European Corn Borer (ECB), Ostrinia nubilalis Hbn. (Lepidoptera: Pyralidae), is a major pest of maize in many countries. Yield losses caused by larvae of this insect depend mainly on the extent of cavity damage, the timing of tunnelling, and their within-plant distribution. To describe these factors, a mechanistic model of cavity appearance is proposed here. It takes into account the main biological processes which determine damage. These are the development, mortality and within-plant distribution of the ECB larvae. The model has been estimated and tested on field data collected at INRA-Versailles in France. Model fittings showed that (i) creation and lengthwise extension rates of cavities per larva depend on location and instar of the larvae, and that (ii) only instars 4 and 5 make cavities. This model described, with a high precision level, the appearance and lengthwise extension of cavities over time and their within-plant distribution for two maize varieties, several infestation dates and levels, and various climatic sequences.

Standard statistical analyses of distributions of individuals from contingency tables are generally invalid if the individuals are not distributed independently of each other. In this paper, we discuss a method of testing hypotheses about classification category occupancy rates for overdispersed population or for population whose individuals are distributed by groups rather than lonely. These methods are based on population redistribution simulations and provide valid, exact and powerful tests in situations for which classical methods are not appropriate. Illustrations are given from the European Corn Borer eggs data.

summary Two techniques for collection of water-soluble substances, particularly carbohydrates, from the leaf surfaces (phylloplane) of maize (Zea mays L.) were compared in order to explain the oviposition preference of the European corn borer. By dipping the leaves in water, smaller amounts of substances were obtained than by spraying water. The total amounts of three sugars (glucose, fructose and sucrose) collected from maize phylloplane ranged from 0.6 to 3.6 mg m−2 of leaf surface. The quantities of these substances varied with the variety of maize, with leaf position, and with the part of the leaf. Sugar ratios on the phylloplane were quite different from those observed within the leaf.

Topical applications of the non-steroidal ecdysone mimic, RH-5849, as expected, initiated a premature moult in last larval instar of the European corn borer, Ostrinia nubilalis . However, RH-5849 induced a perfect supernumerary larval moult in diapause and non-diapause larvae when the application was performed very early in the instar. The compound induced larval-pupal intermediates and normal pupae if it was applied after 2 days in the last instar of non-diapause larvae and after 5–6 days in diapause larvae. The occurrence of larval-pupal moults and normal pupae demonstrated the onset of pupal commitment of the diapause larvae. Moulting to normal pupae was greatly improved by a double topical application of 1 μg RH-5849 onto diapause larvae. Although the rate of normal pupation was rather low, the ecdysone mimic could break the larval diapause of the European corn borer and produce normal pupae. From these results, the endocrine control of diapause induction is discussed.

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* ... suite auteurs (tous EXT): Stäubli, A.; Tuset, J.J.; Vainio, A.; Van de Veire, M.; Viggiani, G.; Vinuela, E.; Vogt, H.

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Ceratosolen silvestrianus and C. arabicus are two species of agaonine fig wasps that co-occur in the figs of Ficus sur in West Africa. Our work in the Ivory Coast shows that both are active pollinators, and that they may be found together in the same syconia. In our study area, C. silvestrianus is much more abundant than C. flabellatus. We found no competitive effect for oviposition sites on C. silvestrianus, and hypothesize that habitat preferences allow the coexistence of two sympatric active pollinators in the same Ficus host in the Ivory Coast. RESUMEN En Afrique de I'Ouest, deux especes d'hymenopteres Agaoninae, Ceratosolen silvestrianus et C. flabellatus, sont associees aFicus sur Notre etude en Core d'Ivoire a montre que toutes dew pollinisent activement, et peuvent se developper ensemble au sein d'une meme figue. Dans notre lieu de recolte, C. silvestrianus est bien plus abondant que C. fibellatus. Nous n'avons pas mis en evidence pour C. silvestrianus, de cout liea la competition avec C. flabellatus. La presence de deux pollinisateurs actifs sur un meme site pourrait etre due a I'existence d'une mosaique d'habitats differents, abritant chacun preferentiellement une des deux especes.

Summary Vectoring ability of four aphid clones, Rp-M and Rp-R26 of Rhopalosiphum padi and Sa-R1 and Sa-V of Sitobion avenae, to transmit barley yellow dwarf (PAV, MAV and RPV) luteoviruses (BYDV) was compared in controlled conditions. Significant differences between highly efficient vectors (HEV), Rp-M and Sa-Rl, and poorly efficient vectors (PEV), Rp-R26 and Sa-V, were found in transmission of their specific viruses with acquisition and inoculation access periods (AAP, IAP) of 5 days. BYD-RPV was occasionally transmitted by both clones of S. avenae. None of 150 tested apterous adults of the Rp-R26 transmitted BYD-MAV, while 10% of transmission was observed from those of the Rp-M in a parallel test. An improved ELISA and immuno-PCR were adapted to test for viruses in aphids. The results obtained by the improved ELISA indicated there was a good correlation between virus detection in single aphids of HEV clones after a 5 day AAP and virus transmission by them. In contrast, the percentages of virus-carrying aphids of PEV clones were generally higher than those of their transmission rates. BYD-MAV and BYD-RPV were also detected by the improved ELISA in single aphids of their PEV clones, with the exception of BYD-RPV in those of Sa-V. However, after a 2-day IAP, the improved ELISA in most cases failed to detect these viruses in single aphids of PEV clones. Detection by immuno-PCR demonstrated that all three viruses could be acquired and retained by the aphids of both HEV and PEV clones. But, as visualised from electrophoretic bands, after the 2-day IAP the amplified products from aphid extracts of PEV clones were reduced. The detection in a batch of nine aphids by the improved ELISA revealed that virus content in PEV clones decreased more rapidly than that in HEV clones during transmission. Thus, the difference in transmission efficiency of the aphid clones within species was not caused by an inability to acquire virus, but was determined by variation in vectoring ability between them. This was due to differences in ability to prevent the passage of virions from haemocoel to salivary duct and/or different capacities for the retention of BYDV.

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Les pullulations de pucerons des céréales (Sitobion avenae F) de 1973 à 1975 en Europe de l’Ouest ont poussé à l’installation d’un réseau de pièges à succion (Agraphid), à l’instar du réseau britannique. Depuis, si les aphides ont pris de plus en plus de place dans les préoccupations des agriculteurs, c’est surtout parce qu’ils transportent et inoculent des virus dommageables à de nombreuses cultures. En dehors des pucerons, on trouve sur poacées des cicadelles, vectrices elles aussi de viroses. Comme les formes ailées des pucerons, les cicadelles adultes font partie du plancton aérien, et dans le piège de l’Inra-Versailles, on a noté les captures de certaines espèces majeures, dont le delphacidé Javesella pellucida Fall et le cicadellidé Psammotettix alienus Fall, vecteur du virus du nanisme du blé qui a causé récemment d’importants dégâts en France. La présence de ces cicadelles dans les prises du réseau de pièges peut permettre une meilleure appréciation des risques viraux dans les semis d’automne des céréales., As a large number of cereal aphids (Sitobion avenae Fabr) were found between 1973 and 1975, a network of suction traps (Agraphid) was constructed in western Europe to survey cereal aphids, following the example of the network in Britain. Farmers have since paid more attention to the damage caused by aphids, which carry and transmit viruses to cultivated plants. Besides aphids, leaf- and plant-hoppers are also found as virus vectors on Poaceae. Adult leaf- and plant-hoppers made up part of the winged aphid population caught by the suction trap in Versailles (INRA). The major species caught were Javesella pellucida and Psammotettix alienus from 1989 to 1994; the latter is an important vector of wheat dwarf virus (WDV). Since WDV has caused economically important losses of cereal in France during recent years, the capture of P alienus may be used to estimate the risk of primary infection of WDV in autumn-sown cereals.

National audience; As a large number of cereal aphids (Sitobion avenae Fabr) were found between 1973 and 1975, a network of suction traps (Agraphid) was constructed in western Europe to survey cereal aphids, following the example of the network in Britain. Farmers have since paid more attention to the damage caused by aphids, which carry and transmit viruses to cultivated plants. Besides aphids, leaf- and plant-hoppers are also found as virus vectors on Poaceae. Adult leaf- and plant-hoppers made up part of the winged aphid population caught by the suction trap in Versailles (INRA). The major species caught were Javesella pellucida and Psammotettix alienus from 1989 to 1994; the latter is an important vector of wheat dwarf virus (WDV). Since WDV has caused economically important losses of cereal in France during recent years, the capture of P alienus may be used to estimate the risk of primary infection of WDV in autumn-sown cereals.; Les pullulations de pucerons des céréales (Sitobion avenae F) de 1973 à 1975 en Europe de l’Ouest ont poussé à l’installation d’un réseau de pièges à succion (Agraphid), à l’instar du réseau britannique. Depuis, si les aphides ont pris de plus en plus de place dans les préoccupations des agriculteurs, c’est surtout parce qu’ils transportent et inoculent des virus dommageables à de nombreuses cultures. En dehors des pucerons, on trouve sur poacées des cicadelles, vectrices elles aussi de viroses. Comme les formes ailées des pucerons, les cicadelles adultes font partie du plancton aérien, et dans le piège de l’Inra-Versailles, on a noté les captures de certaines espèces majeures, dont le delphacidé Javesella pellucida Fall et le cicadellidé Psammotettix alienus Fall, vecteur du virus du nanisme du blé qui a causé récemment d’importants dégâts en France. La présence de ces cicadelles dans les prises du réseau de pièges peut permettre une meilleure appréciation des risques viraux dans les semis d’automne des céréales.

*INRA de Colmar , laboratoire de zoologie

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chap. 17

INRA, Centre de Versailles

chap. 18

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Taking into account the limits of previous models proposed to predict European corn borer, Ostrinia nubilalis (Hubner) infestation time, complementary research in physiology, population dynamic, and modeling was used to propose a mechanistic model to describe this phenomenon. Diapause is the main process that determines infestation time in this pest. Recent work on diapause has demonstrated the heterogeneity of this development phase. This model describes the first phase of the diapause process, wing disk development. The model proposed consists of two parts; the first component takes into account the influence of temperature as a nonlinear function and the second (normal distributions) represents the variability in development time among a population for each stage. This model has been estimated by maximum likelihood from laboratory data obtained with a destructive sampling under three variable sinusoidal temperature regimes 9–21, 12–34, and 18–42°C with a photoperiod of 12:12 (L:D) hallowing diapause induction. This unique model describes the development under these different temperature ranges with a 2% precision (0.5 d) and has been validated under field conditions. The development of populations ending their development before winter is correctly represented (10% precision). The model is not adapted to describe the population ending their development after winter. The estimated model correctly predicts diapause development for temperatures above 4°C. This report presents novel data in modeling research and demontrates a convincing correlation between laboratory and field collected data.

The side effects of 5 insecticides, 8 fungicides and 6 herbicides on 24 species of beneficial organisms were tested by members of the Working Group «Pesticides and Beneficial Organisms» of the International Organization for Biological Control (IOBC), West Palaearctic Regional Section (WPRS). The tests were conducted by 24 members in 11 countries according to internationally approved guidelines.