Cyclical transmission of Trypanosoma brucei gambiense in Glossina palpalis gambiensis displays great differences among field isolates

Six sets of teneral Glossina palpalis gambiensis (Diptera: Glossinidae) were fed on mice infected with six different isolates of Thpanosoma brucei gambiense (each mouse was infected with one of the isolates), previously isolated from patients in the sleeping sickness focus of Bonon, Cote d'Ivoire and in Makoua, Congo. All the tsetse flies were dissected 42 days post-infection and midgut and salivary glands were examined for trypanosomes by microscopical examination. No infection was observed with the reference stock whereas each of the five recently isolated trypanosome isolates was able to infect tsetse flies, with rates of infection varying between 9.7 and 18.2% depending on the isolate. Three isolates displayed only immature infections with 9.7, 17.3 and 18% of the flies showing trypanosomes in their midgut. One isolate gave both immature (12.1%) and mature infections (6.1%). Finally, the last isolate involved only mature infections in 9.7% of the Glossina species examined. These substantial differences in the cyclical transmission of T b. gambiense in the same fly species could have important implications for the epidemiology of the transmission of Human African Trypanosomiasis

Serodiagnosis of bovine trypanosomosis based on HSP70/BiP inhibition ELISA

Animal trypanosomosis is a serious constraint to livestock productivity in tropical and subtropical countries. The pathogenic trypanosomes in bovidae are Trypanosoma congolense, T. vivax, T. brucei and T. evansi. Current serological tests to detect trypanosome infections are based on the use of whole trypanosome lysates; their potential is limited by antigen instability, lack of reproducibility and lack of test specificity due to the antibody's long persistence after treatment. The development of new tests based on recombinant technology that could be standardized and applied on a large scale at low cost would be very helpful. The major invariant antigen recognized by T. congolense infected cattle belongs to the heat shock protein (HSP) 70 family and is closely related to mammalian Immunoglobulin Binding Protein (BiP). To improve the initial ELISA based on a recombinant fragment of HSP70/BiP, we developed an inhibition ELISA using an anti-BiP monoclonal antibody and a full-length fusion protein expressed in E. coli. Here we report on the development of the test and provide an initial assessment of its performance using sets of sera from experimental infections and from naturally infected cattle maintained in tsetse infested areas of Africa. The HSP70/BIP-based inhibition ELISA shows a good sensitivity in cattle experimentally infected with T. congolense, with an improved sensitivity in secondary infections. One major advantage, particularly for its further application in national laboratories, is that one single set of reagents and one single procedure are sufficient to apply on different mammalian host species infected with different trypanosome species

Monitoring the pleomorphism of Trypanosoma brucei gambiense isolates in mouse : impact on its transmissibility to Glossina palpalis gambiensis

Substantial differences have been observed between the cyclical transmission of three Trypanosoma brucei gambiense field isolates in Glossina palpalis gambiensis (Ravel et al., 2006). Differences in the pleomorphism of these isolates in rodent used to provide the infective feed to Glossina, could explain such results, since stumpy forms are preadapted for differentiation to procyclic forms when taken up in a tsetse bloodmeal. To assess this possibility, mice were immunosuppressed and inoculated intraperitoneally with the three isolates (six mice for each trypanosome isolate); then parasitaemia and pleomorphism were determined daily for each mouse. The three T. b. gambiense isolates induced different infection patterns in mouse. The parasitaemia peak was rapidly reached for all the isolates and maintained until mice death for two isolates, while the third isolate rapidly showed a failing phase followed by a second parasitaemia plateau. The proportion of the stumpy forms varied from 15% to 70% over the duration of the experiment and according to the isolate. One isolate, which displayed the highest proportion of stumpy forms and reached the stumpy peak at the onset of the failing phase of parasitaemia, was used to study the relationship between the proportion of stumpy forms and transmissibility to tsetse fly. The results indicated that the transmissibility of trypanosomes was not correlated to the proportion of non-dividing stumpy forms

Nod factor-independent nodulation in Aeschynomene evenia required the common plant-microbe symbiotic toolkit

Nitrogen fixation in the legume-rhizobium symbiosis is a crucial area of research for more sustainable agriculture. Our knowledge of the plant cascade in response to the perception of bacterial Nod factors has increased in recent years. However, the discovery that Nod factors are not involved in the Aeschynomene-Bradyrhizobium spp. interaction suggests that alternative molecular dialogues may exist in the legume family. We evaluated the conservation of the signaling pathway common to other endosymbioses using three candidate genes: Ca2+/Calmodulin-Dependent Kinase (CCaMK), which plays a central role in cross signaling between nodule organogenesis and infection processes; and Symbiosis Receptor Kinase (SYMRK) and Histidine Kinase1 (HK1), which act upstream and downstream of CCaMK, respectively. We showed that CCaMK, SYMRK, and HK1 are required for efficient nodulation in Aeschynomene evenia. Our results demonstrate that CCaMK and SYMRK are recruited in Nod factor-independent symbiosis and, hence, may be conserved in all vascular plant endosymbioses described so far

Presence of multiple non-B subtypes and divergent subtype B strains of HIV-1 in individuals infected after overseas deployment

Objective : to identify the genetic subtypes and characteristics of HIV-1 strains from individuals infected after overseas deployment. Sixty-one HIV-1-positive individuals detected between 1986 and 1995 in the French army were included in the study. For each patient, the year and country of HIV infection are known. Genetic subtypes of HIV-1 were determined using the heteroduplex mobility assay (HMA) using ED5/ED12 as outer and ES7/ES8 as inner primers. Strains were further characterized by sequencing and phylogenetic analysis of the C2-V3 region. The aminoacid sequences corresponding to the V3 region were aligned on the basis of the subtyping results and were then compared to the consensus V3 sequences of the corresponding subtypes. Among the 61 patients studied, nine became infected in France, and 52 were HIV-negative before overseas deployment but HIV-positive at their return. The majority (n = 43) deployed in Africa and a limited number of patients deployed in Asia (Cambodia, n = 5) or South America (Guyana, n = 4). The nine individuals who were not deployed overseas were all infected with subtype B strains. The majority the other patients were infected with non-B strains ; eight subtype A, 20 subtype B, 16 subtype C, one subtype D, six subtype E and one subtype F. Five of the six subtype E strains were contracted in Cambodia and one in Djibouti, and all subtype C strains were from Djibouti. Phylogenetic analysis revealed a large diversity among the different strains introduced into France. Analysis of the aminoacid sequences of the V3 loop revealed the introduction of uncommon V3-loop patterns. In the group of HIV-1-infected individuals that we studied and who were deployed overseas, 63.4% were infected with non-B strains. In addition the subtype A, B, and C viruses in this population were very heterogeneous. (Résumé d'auteur

Trypanosoma brucei brucei induces alteration in the head proteome of the tsetse fly vector Glossina palpalis gambiensis

Parasitic manipulations of host behaviour are known from a wide range of host-parasite associations. However, the understanding of these phenomena is far from complete and detailed investigation of their proximate causes is needed. Many studies report behavioural modifications, such as altered feeding rates in tsetse fly (Glossina) infected with the mature transmissible stage (i.e. metacyclic) of the trypanosomes. Here, bidimensional (2D) gel electrophoresis and mass spectrometry were employed to analyse and compare the head proteome between four Glossina palpalis gambiensis categories (uninfected, refractory, mature infection, immature infection). Twenty-four protein spots specifically present or absent in the head of metacyclic-infected flies were observed. These protein spots were subsequently identified and functionally classified as glycolitic, neurotransmiter synthesis, signalling, molecular chaperone and transcriptional regulation proteins. Our results indicate altered energy metabolism in the head of metacyclic-infected tsetse flies. Some of the proteins identified, such as casein kinase 2 and jun kinase have previously been shown to play critical roles in apoptosis in insect neurones. In addition, we found two pyridoxal-dependent decarboxylases (dopa decarboxylase and alpha methyldopa hypersensitive protein), suggesting a modification of serotonin and/or dopamine in the brain of metacyclic-infected tsetse flies. Our data pave the way for future investigation of the alteration of the glossina central nervous system during infection by trypanosomes