Evidence that the mechanism of gene exchange in Trypanosoma brucei involves meiosis and syngamy

Parasitology ◽  
1990 ◽  
Vol 101 (3) ◽  
pp. 377-386 ◽  
Author(s):  
C. M. R. Turner ◽  
J. Sternberg ◽  
N. Buchanan ◽  
E. Smith ◽  
G. Hide ◽  
...  
Keyword(s):  
Trypanosoma Brucei ◽  
Preliminary Analysis ◽  
Genetic System ◽  
Genetic Exchange ◽  
Tsetse Flies ◽  
Gene Exchange ◽  
Glossina Morsitans ◽  
Length Polymorphisms ◽  
Allelic Segregation ◽  
Hybrid Clones

SUMMARYAll pairwise combinations of three cloned stocks of Trypanosoma brucei (STIB 247L, STIB 386AA and TREU 927/4) were co-transmitted through tsetse flies (Glossina morsitans) and screened for the production of hybrid trypanosomes. Clones of metacyclic and bloodstream trypanosomes from flies harbouring mature infections containing hybrid trypanosomes were established and screened for several isoenzyme and restriction fragment length polymorphisms. For each of the three combinations of parents, some progeny clones were observed to be of a phenotype and genotype indicating that genetic exchange had occurred during development of the trypanosomes in flies. These hybrid clones shared three salient features: (1) where the parents were homozygous variants the progeny were heterozygous, (2) where one of the parents was heterozygous, allelic segregation was observed and (3) the progeny clones were shown to be recombinant when two or more markers for which one of the parents was heterozygous were examined. These results are consistent with the progeny being an F1 in a diploid mendelian genetic system involving meiosis and syngamy. Our observations show that all possible combinations of the three stocks may undergo genetic exchange. A marker analysis of a series of clones each derived from single metacyclic trypanosomes showed that individual flies transmit a mixture of trypanosome genotypes corresponding to F1 progeny and to parental types, indicating that genetic exchange was a non-obligatory event in the life-cycle of the trypanosome. In addition, a preliminary analysis of the phenotype of procyclic stage trypanosomes derived from flies infected with two stocks, indicates that genetic exchange is unlikely to occur at this stage.

Infection of post-teneral tsetse flies (Glossina morsitans morsitans and Glossina morsitans centralis) with Trypanosoma brucei brucei

1988 ◽  
Vol 66 (6) ◽  
pp. 1289-1292 ◽  
Author(s):  
R. H. Gooding
Keyword(s):  
Trypanosoma Brucei ◽  
Significant Proportion ◽  
Glossina Morsitans Morsitans ◽  
Tsetse Flies ◽  
Glossina Morsitans ◽  
Trypanosoma Brucei Brucei ◽  
Male And Female ◽  
Glossina Morsitans Centralis

A significant proportion of post-teneral male Glossina morsitans morsitans Westwood and post-teneral male and female Glossina morsitans centralis Machado develop mature infections of Trypanosoma brucei brucei Plimmer and Bradford without being starved before feeding upon infected rabbits.

Antigenic variation in cyclically transmitted Trypanosoma brucei. Variable antigen type composition of metacyclic trypanosome populations from the salivary glands of Glossina morsitans

Parasitology ◽  
1981 ◽  
Vol 83 (3) ◽  
pp. 595-607 ◽  
Author(s):  
S. L. Hajduk ◽  
Cathy R. Cameron ◽  
J. D. Barry ◽  
K. Vickerman
Keyword(s):  
Salivary Glands ◽  
Trypanosoma Brucei ◽  
Indirect Immunofluorescence ◽  
Antigenic Variation ◽  
Tsetse Flies ◽  
Glossina Morsitans ◽  
Type Composition ◽  
Variable Antigen ◽  
Monospecific Antisera

SUMMARYTsetse flies (Glossina morsitans) were fed on the blood of mice containing any one of 5 variable antigen types (VATs) of Trypanosoma brucei AnTAR 1 serodeme. The VATs of the metacyclic trypanosomes subsequently detected in the flies' saliva probes were investigated using monospecific antisera to AnTAR 1 VATs in indirect immunofluorescence and trypanolysis reactions; these sera included 3 raised against AnTats 1.6, 1.30 and 1.45, previously identified as components of the metacyclic population (M-VATs), and against the 5 VATs originally ingested by the flies. The percentage of metacyclics reacting with a particular M-VAT antiserum remained more or less constant (AnTat 1.6, 6·0–8·3%; AnTat 1.30, 13·7–18·2%; AnTat 1.45, 2·0–8·0%), regardless of the age of the fly or the ingested VAT. As these 3 VATs accounted for no more than 30% of the metacyclic population, the existence of at least one more VAT is envisaged. The ingested VAT could not be detected among the AnTAR 1 metacyclic trypanosomes.

The effects of genetic exchange on variable antigen expression in Trypanosoma brucei

Parasitology ◽  
1991 ◽  
Vol 103 (3) ◽  
pp. 379-386 ◽  
Author(s):  
C. M. R. Turner ◽  
N. Aslam ◽  
E. Smith ◽  
N. Buchanan ◽  
A. Tait
Keyword(s):  
Trypanosoma Brucei ◽  
Antigen Expression ◽  
Genetic Exchange ◽  
Direct Immunofluorescence ◽  
Tsetse Flies ◽  
Double Labelling ◽  
Hybrid Progeny ◽  
Parental Stock ◽  
Variable Antigen ◽  
Antibody Specificities

The inheritance of variant surface antigens in Trypanosoma brucei has been determined by identifying variable antigen types (VATs) in each of two cloned parental stocks and then examining the presence and abundance of these VATs in hybrid progeny produced when these stocks undergo genetic exchange during co-transmission through tsetse flies. Nine VATs have been identified from the repertoire of the parental stock STIB 247L and 5 VATs have been identified from the parental stock STIB 386AA; the identified VATs were exclusive to each stock. Their inheritance was elucidated using two assays. In the first, repertoire antisera (RAS) containing antibody specificities to many different VATs were raised in rabbits to the 2 parental stocks and 6 progeny clones. The presence of VAT-specific antibodies in these RAS was then determined by antibody-dependent complement-mediated lysis. In the second assay, the 2 parental stocks and 4 hybrid progeny clones were each independently transmitted through tsetse flies and VATs observed using VAT-specific antisera in indirect immunofluorescence of metacyclic trypanosomes and in bloodstream forms of fly-bitten mice. The results from both assays showed that (1) both metacyclic- and bloodstream-VATs were inherited into the progeny, (2) each hybrid progeny clone contained some VATs from both parents, (3) hybrids did not express all the VATs from either parent, (4) there was little apparent pattern as to which VATs had been inherited and which had not and (5) the VAT repertoires of the hybrid progeny appeared to be larger than those of the parents. In addition, two results indicated that control of VAT expression remains unaltered after genetic exchange. Firstly, the immunofluorescence results showed that VATs present in hybrid trypanosomes were expressed at the same stage during an infection and at approximately the same prevalence as in the parent. Secondly, a double-labelling experiment using direct immunofluorescence indicated that individual hybrid trypanosomes did not generally simultaneously express more than one VAT. Taken together, these results demonstrate that recombinant VAT repertoires are created when trypanosomes undergo genetic exchange and that genetic exchange is a mechanism whereby the generation of new serodemes can occur.

Analysis of a genetic cross between Trypanosoma brucei rhodesiense and T. b. brucei

Parasitology ◽  
1989 ◽  
Vol 99 (3) ◽  
pp. 391-402 ◽  
Author(s):  
W. C. Gibson
Keyword(s):  
Nuclear Dna ◽  
Genetic Material ◽  
West African ◽  
Genetic Exchange ◽  
Dna Polymorphisms ◽  
Tsetse Flies ◽  
Trypanosoma Brucei Rhodesiense ◽  
Nuclear Markers ◽  
Genetic Cross ◽  
Hybrid Clones

SummaryTwo trypanosome clones, representing East and West African homozygotes at 2 isoenzyme loci (T. b. rhodesiense MHOM/ZM/74/58 [CLONE B] and T. b. brucei MSUS/CI/78/TSW 196 [CLONE A]), were cotransmitted through tsetse flies and the resulting trypanosome populations checked for the presence of non-parental karyotypes by pulsed-field gel electrophoresis. Ten clones isolated from these populations proved to have 5 different recombinant genotypes by analysis of nuclear and kinetoplast DNA (kDNA) polymorphisms. It is inferred that genetic exchange occurred between the 2 trypanosome clones in the fly, as previously reported for 2 other T. brucei spp. clones by Jenni and colleagues. For the most part, the hybrid clones shared many characteristics with both parents and their genotypes were consistent with segregation and reassortment of parental alleles. The least amount of genetic material exchanged was kDNA alone. Regarding the mechanism of genetic exchange, several hybrid clones had identical and unique nuclear DNA polymorphisms, but different kDNA type. Assuming that the same reassortment of nuclear markers is unlikely to occur by chance, these clones most probably arose from a predecessor carrying both types of kDNA.

Antigenic variation in cyclically transmitted Trypanosoma brucei. Variable antigen type composition of the first parasitaemia in mice bitten by trypanosome-infected Glossina morsitans

Parasitology ◽  
1981 ◽  
Vol 83 (3) ◽  
pp. 609-621 ◽  
Author(s):  
S. L. Hajduk ◽  
K. Vickerman
Keyword(s):  
Salivary Glands ◽  
Trypanosoma Brucei ◽  
Antigenic Variation ◽  
Tsetse Flies ◽  
Glossina Morsitans ◽  
Type Composition ◽  
X Irradiation ◽  
Variable Antigen ◽  
Monospecific Antisera ◽  
Cyclical Transmission

SUMMARYTsetse flies were infected with 5 different variable antigen types (VATs) or with a mixture of VATs of the AnTAR 1 serodeme of Trypanosoma brucei. Metacyclic forms from the salivary glands of infected flies were used to initiate infections in mice. Immunofluorescence and trypanolysis reactions employing 24 monospecific antisera were used to analyse the VATs present in the mice following cyclical transmission. Regardless of the VAT used to infect tsetse flies, the first VATs detectable in the bloodstream were those previously identified as metacyclic VATs (M-VATs). These were present until at least 5 days after infection, at which time lytic antibodies against at least 2 of the M-VATs were detectable in the blood of infected mice. In mice immunosuppressed by X-irradiation the M-VATs were detectable in the bloodstream for longer periods, but the percentage of the population labelled with anti-metacyclic sera showed a decrease on day 5 as in non-irradiated animals. The VAT ingested by the tsetse was always detectable early during the first parasitaemia following cyclical transmission and was usually the first VAT detected after the M-VATs. Neutralization of selected M-VATs before infecting mice resulted in elimination of the neutralized M-VAT from the first parasitaemia but had no effect on the expression of other VATs in the early infection.

scholarly journals The population genetics of Trypanosoma brucei and the origin of human infectivity

2001 ◽  
Vol 356 (1411) ◽  
pp. 1035-1044 ◽  
Author(s):  
Annette MacLeod ◽  
Andy Tait ◽  
C. Michel R. Turner
Keyword(s):  
Trypanosoma Brucei ◽  
Genetic Relationships ◽  
Genetic Exchange ◽  
Sub Saharan Africa ◽  
Tsetse Flies ◽  
Implicit Assumption ◽  
Mixed Genotype ◽  
Disease Biology ◽  
Zoonotic Parasite ◽  
Sub Saharan

The African trypanosome, Trypanosoma brucei , is a zoonotic parasite transmitted by tsetse flies. Two of the three subspecies, T. brucei gambiense and T.b. rhodesiense , cause sleeping sickness in humans whereas the third subspecies, T.b. brucei , is not infective to humans. We propose that the key to understanding genetic relationships within this species is the analysis of gene flow to determine the importance of genetic exchange within populations and the relatedness of populations. T.brucei parasites undergo genetic exchange when present in infections of mixed genotypes in tsetse flies in the laboratory, although this is not an obligatory process. Infections of mixed genotype are surprisingly common in field isolates from tsetse flies such that there is opportunity for genetic exchange to occur. Population genetic analyses, taking into account geographical and host species of origin, show that genetic exchange occurs sufficiently frequently in the field to be an important determinant of genetic diversity, except where particular clones have acquired the ability to infect humans. Thus, T. brucei populations have an ‘epidemic’ genetic structure, but the better-characterized human-infective populations have a ‘clonal’ structure. Remarkably, the ability to infect humans appears to have arisen on multiple occasions in different geographical locations in sub-Saharan Africa. Our data indicate that the classical subspecies terminology for T. brucei is genetically inappropriate. It is an implicit assumption in most infectious disease biology that when a zoonotic pathogen acquires the capability to infect humans, it does so once and then spreads through the human population from that single-source event. For at least one major pathogen in tropical medicine, T. brucei , this assumption is invalid.

Aircraft Applications of Insecticides in East Africa. IV.—The Application of Coarse Aerosols in Savannah Woodland containing the Tsetse Flies Glossina morsitans and G. swynnertoni

1953 ◽  
Vol 44 (4) ◽  
pp. 627-640 ◽  
Author(s):  
K. S. Hocking ◽  
H. C. M. Parr ◽  
D. Yeo ◽  
D. Anstey
Keyword(s):  
East Africa ◽  
Meteorological Conditions ◽  
The Other ◽  
Tsetse Flies ◽  
Small Populations ◽  
Central Province ◽  
Glossina Morsitans ◽  
Short Period ◽  
Savannah Woodland ◽  
Mass Median

Attempts have been made to eradicate the tsetse flies G. morsitans and G. swynnertoni from two blocks of savannah woodland situated in the Central Province of Tanganyika.The insecticides were applied from aircraft. Coarse aerosols were used, with mass median diameters of approximately 90 microns; droplet diameters varied from 4 microns to 250 microns approximately.Eight applications of insecticides were made at intervals of two weeks. Each application was carried out at a nominal dosage of 0·25 gallons per acre, which was equivalent to 0·20 1b. per acre of the p, p'isomer of DDT or 0·03 lb. per acre of the γ isomer of BHC.In the area treated with DDT it is possible that both species of flies were eradicated for a short period, but small populations were re-established there by immigrant flies. In the other block the reduction was not so great, but it is not considered that this was due to a lesser effectiveness of the BHC, but to a combination of circumstances that led to less effective applications.Some general observations are made upon the use of aircraft for this sort of work, particularly in connection with the effect of meteorological conditions.

Turbulent plumes of heat, moist heat, and carbon dioxide elicit upwind anemotaxis in tsetse flies Glossina morsitans morsitans Westwood (Diptera: Glossinidae)

2002 ◽  
Vol 80 (7) ◽  
pp. 1149-1155 ◽  
Author(s):  
W G Evans ◽  
R H Gooding
Keyword(s):  
Carbon Dioxide ◽  
Wind Tunnel ◽  
Relative Humidity ◽  
Glossina Morsitans Morsitans ◽  
Tsetse Flies ◽  
Glossina Morsitans ◽  
Low Velocity ◽  
Upwind Flight ◽  
Moist Heat ◽  
Heated Air

The roles and interactions of turbulent plumes of heat, moist heat, and carbon dioxide in mediating upwind flight of adult tsetse flies (Glossina morsitans morsitans Westwood) were investigated using a wind tunnel in a constant-environment chamber. Heat fluctuations in the plume that were detected by a thermocouple and displayed as oscilloscope traces allowed direct visualization of the structures of the plumes. Significantly more flies flew upwind when exposed to plumes of (i) carbon dioxide (0.0051% above background) and air (58% relative humidity) compared with air alone; (ii) carbon dioxide and heated air (35% relative humidity and temperature fluctuating up to 0.09°C above background) compared with carbon dioxide and air; and (iii) carbon dioxide and moist (82% relative humidity) heated air (temperature fluctuating up to 0.05°C above background) compared with carbon dioxide and heated air. However, there were no significant differences in upwind flight of flies exposed to plumes of (i) air compared with humidified air (65% relative humidity); (ii) carbon dioxide and heated air compared with heated air alone; and (iii) carbon dioxide and moist heated air compared with moist heated air alone. Recorded temperature fluctuations in heat plumes transported downwind from a tethered steer in a pasture showed patterns similar to those produced in the wind-tunnel plumes. These results suggest that host emissions of carbon dioxide alone and combined heat and moisture carried downwind by low-velocity winds elicit upwind anemotaxis in tsetse flies, which distinguish these emissions from a background of lower atmospheric levels.

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