Dynamics of infection and competition between two strains of Trypanosoma brucei bruceiin the tsetse fly observed using fluorescent markers
Tóm tắt
Genetic exchange occurs between Trypanosoma brucei strains during the complex developmental cycle in the tsetse vector, probably within the salivary glands. Successful mating will depend on the dynamics of co-infection with multiple strains, particularly if intraspecific competition occurs. We have previously used T. brucei expressing green fluorescent protein to study parasite development in the vector, enabling even one trypanosome to be visualized. Here we have used two different trypanosome strains transfected with either green or red fluorescent proteins to study the dynamics of co-infection directly in the tsetse fly. The majority of infected flies had both trypanosome strains present in the midgut, but the relative proportion of red and green trypanosome strains varied considerably between flies and between different sections of the midgut in individual flies. Colonization of the paired salivary glands revealed greater variability than for midguts, as each gland could be infected with red and/or green trypanosome strains in variable proportions. Salivary glands with a mixed infection appeared to have a higher density of trypanosomes than glands containing a single strain. Comparison of the numbers of red and green trypanosomes in the proventriculus, salivary exudate and glands from individual flies showed no correlation between the composition of the trypanosome population of the proventriculus and foregut and that of the salivary glands. For each compartment examined (midgut, foregut, salivary glands), there was a significantly higher proportion of mixed infections than expected, assuming the null hypothesis that the development of each trypanosome strain is independent. Both the trypanosome strains used were fully capable of infecting tsetse, but the probabilities of infection with each strain were not independent, there being a significantly higher proportion of mixed infections than expected in each of three compartments examined: midgut, proventriculus and salivary glands. Hence there was no evidence of competition between trypanosome strains, but instead co-infection was frequent. Infection rates in co-infected flies were no different to those found routinely in flies infected with a single strain, ruling out the possibility that one strain enhanced infection with the other. We infer that each fly is either permissive or non-permissive of trypanosome infection with at least 3 sequential checkpoints imposed by the midgut, proventriculus and salivary glands. Salivary glands containing both trypanosome strains appeared to contain more trypanosomes than singly-infected glands, suggesting that lack of competition enhances the likelihood of genetic exchange.
Tài liệu tham khảo
Lewis EA, Langridge WP: Developmental forms of Trypanosoma brucei in the "saliva" of Glossina pallidipes and G. austeni. Ann Trop Med Parasitol. 1947, 41: 6-13.
Van den Abbeele J, Claes Y, Van Bockstaele D, Le Ray D, Coosemans M: Trypanosoma brucei spp. development in the tsetse fly: characterization of the post-mesocyclic stages in the foregut and proboscis. Parasitology. 1999, 118: 469-478. 10.1017/S0031182099004217.
Aksoy S, Gibson W, Lehane MJ: Interactions between tsetse and trypanosomes with implications for the control of trypanosomiasis. Adv Parasitol. 2003, 53: 1-83.
Sharma R, Peacock L, Gluenz E, Ferris V, Gull K, Gibson W, Carrington M: Asymmetric division during the developmental cycle of Trypanosoma brucei. In preparation. 2007
Malele I, Craske L, Knight C, Ferris V, Njiru Z, Hamilton P, Lehane S, Lehane M, Gibson W: Identification of new trypanosome species from wild tsetse flies in Tanzania. Infection, Genetics and Evolution. 2003, 3: 271-279. 10.1016/S1567-1348(03)00090-X.
Adams ER, Malele II, Msangi AR, Gibson WC: Trypanosome identification in wild tsetse populations in Tanzania using generic primers to amplify the ribosomal RNA ITS-1 region . Acta Trop. 2006, 100: 103-109. 10.1016/j.actatropica.2006.10.002.
Letch CA: A mixed population of Trypanozoon in Glossina palpalis palpalis from Ivory Coast. Trans R Soc Trop Med Hyg. 1984, 78: 627-630. 10.1016/0035-9203(84)90223-2.
MacLeod A, Turner CMR, Tait A: A high level of mixed Trypanosoma brucei infections in tsetse flies detected by three hypervariable minisatellites. Mol Biochem Parasitol. 1999, 102: 237-248. 10.1016/S0166-6851(99)00101-2.
Gibson W, Ferris V: Sequential infection of tsetse flies with Trypanosoma congolense and T. brucei. Acta Trop. 1992, 50: 345-352. 10.1016/0001-706X(92)90070-E.
Kubi C, Van den Abbeele J, Dorny P, Coosemans M, Marcotty T, Van den Bossche P: Ability of trypanosome-infected tsetse flies (Diptera : Glossinidae) to acquire an infection with a second trypanosome species. J Med Entomol. 2005, 42: 1035-1038. 10.1603/0022-2585(2005)042[1035:AOTTFD]2.0.CO;2.
Jenni L, Marti S, Schweizer J, Betschart B, Lepage RWF, Wells JM, Tait A, Paindavoine P, Pays E, Steinert M: Hybrid formation between African trypanosomes during cyclical transmission. Nature. 1986, 322: 173-175. 10.1038/322173a0.
Gibson W, Stevens J: Genetic exchange in the Trypanosomatidae. Adv Parasitol. 1999, 43: 1-46.
Bingle LEH, Eastlake JL, Bailey M, Gibson WC: A novel GFP approach for the analysis of genetic exchange in trypanosomes allowing the in situ detection of mating events. Microbiology-Sgm. 2001, 147: 3231-3240.
Gibson W, Bailey M: The development of Trypanosoma brucei in the tsetse fly midgut observed using green fluorescent trypanosomes. Kinetoplastid Biol Dis. 2003, 2 (1): 1-10.1186/1475-9292-2-1.
Guevara P, Dias M, Rojas A, Crisante G, Abreu-Blanco MT, Umezara E, Vazquez M, Levin M, Anez N, Ramirez JL: Expression of fluorescent genes in Trypanosoma cruzi and Trypanosoma rangeli (Kinetoplastida : Trypanosomatidae) its application to parasite-vector biology. J Med Entomol. 2005, 42 (1): 48-56. 10.1603/0022-2585(2005)042[0048:EOFGIT]2.0.CO;2.
Balmer O, Tostado C: New fluorescence markers to distinguish co-infecting Trypanosoma brucei strains in experimental multiple infections. Acta Trop. 2006, 97: 94-101. 10.1016/j.actatropica.2005.09.002.
Haenni S, Renggli CK, Fragoso CM, Oberle M, Roditi I: The procyclin-associated genes of Trypanosoma brucei are not essential for cyclical transmission by tsetse. Mol Biochem Parasitol. 2006, 150: 144-156. 10.1016/j.molbiopara.2006.07.005.
Inman CF, Rees LEN, Barker E, Haverson K, Stokes CR, Bailey M: Validation of computer-assisted, pixel-based analysis of multiple-colour immunofluorescence histology. J Immunol Methods. 2005, 302: 156-167. 10.1016/j.jim.2005.05.005.
Gibson W, Peacock L, Ferris V, Williams K, Bailey M: Analysis of a cross between green and red fluorescent trypanosomes. Biochem Soc Trans. 2006, 34: 557-559. 10.1042/BST0340557.
Elliot SL, Adler FR, Sabelis MW: How virulent should a parasite be to its vector?. Ecology. 2003, 84: 2568-2574. 10.1890/02-8013.
Hao ZR, Kasumba I, Lehane MJ, Gibson WC, Kwon J, Aksoy S: Tsetse immune responses and trypanosome transmission: Implications for the development of tsetse-based strategies to reduce trypanosomiasis. Proc Natl Acad Sci U S A. 2001, 98: 12648-12653. 10.1073/pnas.221363798.
Hu CY, Aksoy S: Innate immune responses regulate trypanosome parasite infection of the tsetse fly Glossina morsitans morsitans. Mol Microbiol. 2006, 60: 1194-1204. 10.1111/j.1365-2958.2006.05180.x.
Abubakar LU, Bulimo WD, Mulaa FJ, Osir EO: Molecular characterization of a tsetse fly midgut proteolytic lectin that mediates differentiation of African trypanosomes. Insect Biochem Mol Biol. 2006, 36: 344-352. 10.1016/j.ibmb.2006.01.010.
Hao ZG, Kasumba I, Aksoy S: Proventriculus (cardia) plays a crucial role in immunity in tsetse fly (Diptera : Glossinidiae). Insect Biochem Mol Biol. 2003, 33: 1155-1164. 10.1016/j.ibmb.2003.07.001.
Van den Bossche P, De Deken R, Brandt J, Geerts S, Geysen D, Berkvens D: The transmission of mixed Trypanosoma brucei brucei/T. congolense infections by tsetse (Glossina morsitans morsitans). Vet Parasitol. 2004, 119: 147-153. 10.1016/j.vetpar.2003.11.008.
Maudlin I: Transmission of African Trypanosomiasis: Interactions among tsetse immune system, symbionts and parasites. Adv Dis Vector Res. 1991, 7: 117-148.
Kabayo JP: The nature of the nutritional importance of serum-albumin to Glossina morsitans. J Insect Physiol. 1982, 28: 917-923. 10.1016/0022-1910(82)90107-X.
Galun R, Margalit J: Adenine nucleotides as feeding stimulants of tsetse fly Glossina austeni Newst. Nature. 1969, 222 (5193): 583-584. 10.1038/222583a0.
Peacock L, Ferris V, Bailey M, Gibson W: Multiple effects of the lectin-inhibitory sugars D-glucosamine and N-acetyl-glucosamine on tsetse-trypanosome interactions. Parasitology. 2006, 132: 651-658. 10.1017/S0031182005009571.
Gibson WC, Fase-Fowler F, Borst P: Further analysis of intraspecific variation in Trypanosoma brucei using restriction site polymorphisms in the maxi-circle of kinetoplast DNA. Mol Biochem Parasitol. 1985, 15: 21-36. 10.1016/0166-6851(85)90026-X.
Gibson WC, Marshall TFC, Godfrey DG: Numerical analysis of enzyme polymorphism: a new approach to the epidemiology and taxonomy of trypanosomes of the subgenus Trypanozoon. Adv Parasitol. 1980, 18: 175-246.
Campbell RE, Tour O, Palmer AE, Steinbach PA, Baird GS, Zacharias DA, Tsien RY: A monomeric red fluorescent protein. Proc Natl Acad Sci U S A. 2002, 99: 7877-7882. 10.1073/pnas.082243699.
Image J. [http://rsb.info.nih.gov/ij/]
Chi squared calculator. Last accessed Dec 2006, [http://www.georgetown.edu/faculty/ballc/webtools/web_chi.html]