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Tsetse immune system maturation requires the presence of obligate symbionts in larvae.

Weiss BL, Wang J, Aksoy S - PLoS Biol. (2011)

Bottom Line: Adults that lack Wigglesworthia during larval development exhibit exceptionally compromised cellular and humoral immune responses following microbial challenge, including reduced expression of genes that encode antimicrobial peptides (cecropin and attacin), hemocyte-mediated processes (thioester-containing proteins 2 and 4 and prophenoloxidase), and signal-mediating molecules (inducible nitric oxide synthase).Furthermore, Gmm(Wgm-) adults harbor a reduced population of sessile and circulating hemocytes, a phenomenon that likely results from a significant decrease in larval expression of serpent and lozenge, both of which are associated with the process of early hemocyte differentiation.Our results demonstrate that Wigglesworthia must be present during the development of immature progeny in order for the immune system to function properly in adult tsetse.

View Article: PubMed Central - PubMed

Affiliation: Department of Epidemiology and Public Health, Division of Epidemiology of Microbial Diseases, Yale University School of Medicine, New Haven, Connecticut, United States of America. brian.weiss@yale.edu

ABSTRACT
Beneficial microbial symbionts serve important functions within their hosts, including dietary supplementation and maintenance of immune system homeostasis. Little is known about the mechanisms that enable these bacteria to induce specific host phenotypes during development and into adulthood. Here we used the tsetse fly, Glossina morsitans, and its obligate mutualist, Wigglesworthia glossinidia, to investigate the co-evolutionary adaptations that influence the development of host physiological processes. Wigglesworthia is maternally transmitted to tsetse's intrauterine larvae through milk gland secretions. We can produce flies that lack Wigglesworthia (Gmm(Wgm-) yet retain their other symbiotic microbes. Such offspring give rise to adults that exhibit a largely normal phenotype, with the exception being that they are reproductively sterile. Our results indicate that when reared under normal environmental conditions Gmm(Wgm-) adults are also immuno-compromised and highly susceptible to hemocoelic E. coli infections while age-matched wild-type individuals are refractory. Adults that lack Wigglesworthia during larval development exhibit exceptionally compromised cellular and humoral immune responses following microbial challenge, including reduced expression of genes that encode antimicrobial peptides (cecropin and attacin), hemocyte-mediated processes (thioester-containing proteins 2 and 4 and prophenoloxidase), and signal-mediating molecules (inducible nitric oxide synthase). Furthermore, Gmm(Wgm-) adults harbor a reduced population of sessile and circulating hemocytes, a phenomenon that likely results from a significant decrease in larval expression of serpent and lozenge, both of which are associated with the process of early hemocyte differentiation. Our results demonstrate that Wigglesworthia must be present during the development of immature progeny in order for the immune system to function properly in adult tsetse. This phenomenon provides evidence of yet another important physiological adaptation that further anchors the obligate symbiosis between tsetse and Wigglesworthia.

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Host survival correlates with symbiont status following septic infectionwith E. coli K12.(A) The effects of age and symbiont status on the survival of tsetse followingsystemic infection with E. coli K12. Mature adultGmmWgm- flies were significantly moresusceptible to infection with 106 CFU of E. colithan were their wild-type counterparts (bottom and middle panels;p<0.001). (B)GmmWT/Wgm− fliesharbored Wigglesworthia during immature development but lackedthe bacteria as mature adults. (C)GmmWT/Wgm− adults wereinfected with tetracycline resistant E. coli 1 d after theirlast antibiotic-supplemented blood meal. Unlike their counterparts that lackedWigglesworthia throughout immature development,GmmWT/Wgm− was able tosurvive infection with E. coli. No significant difference insurvival was observed between mature adult GmmWTversus GmmWT/Wgm− adultsinfected with 106 CFU of E. coli (Figure 1A middle panel andFigure 1C;p  = 0.07). (D) RelativeSodalis and Wolbachia densities in40-d-old GmmWT andGmmWgm− adults(n  = 5 of each) were normalizedagainst host β-tubulin copy number. (E) Analysis ofbacterial 16s rRNA clone libraries indicates thatGmmWT larvae harboredWigglesworthia, Sodalis, andWolbachia, while their counterparts from ampicillin treatedfemales harbored only Sodalis and Wolbachia.No other bacteria were identified from either fly line. (F) Average number(±SEM) of recE. colipIL per tsetse strainover time (n  = 3 individuals per strainper time point) following septic infection with 103 CFU of bacteria.Values shown in red represent lethal infections.
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pbio-1000619-g001: Host survival correlates with symbiont status following septic infectionwith E. coli K12.(A) The effects of age and symbiont status on the survival of tsetse followingsystemic infection with E. coli K12. Mature adultGmmWgm- flies were significantly moresusceptible to infection with 106 CFU of E. colithan were their wild-type counterparts (bottom and middle panels;p<0.001). (B)GmmWT/Wgm− fliesharbored Wigglesworthia during immature development but lackedthe bacteria as mature adults. (C)GmmWT/Wgm− adults wereinfected with tetracycline resistant E. coli 1 d after theirlast antibiotic-supplemented blood meal. Unlike their counterparts that lackedWigglesworthia throughout immature development,GmmWT/Wgm− was able tosurvive infection with E. coli. No significant difference insurvival was observed between mature adult GmmWTversus GmmWT/Wgm− adultsinfected with 106 CFU of E. coli (Figure 1A middle panel andFigure 1C;p  = 0.07). (D) RelativeSodalis and Wolbachia densities in40-d-old GmmWT andGmmWgm− adults(n  = 5 of each) were normalizedagainst host β-tubulin copy number. (E) Analysis ofbacterial 16s rRNA clone libraries indicates thatGmmWT larvae harboredWigglesworthia, Sodalis, andWolbachia, while their counterparts from ampicillin treatedfemales harbored only Sodalis and Wolbachia.No other bacteria were identified from either fly line. (F) Average number(±SEM) of recE. colipIL per tsetse strainover time (n  = 3 individuals per strainper time point) following septic infection with 103 CFU of bacteria.Values shown in red represent lethal infections.

Mentions: Insects are normally capable of mounting an immune response that combats infectionwith various groups of bacteria. Interestingly, in comparison toDrosophila, tsetse flies are uniquely susceptible to septicinfection with 103 colony-forming units (CFU) of normally non-pathogenicEscherichia coli (E. coli) K12 [15]. In the presentstudy we further investigated tsetse's unique susceptibility to E.coli infection by subjecting wild-type(GmmWT) and adults from two age groups to hemocoelicinfections with varying quantities of E. coli K12. Three-day-oldGmmWT individuals (flies from this age group arehereafter referred to as “young”) were highly susceptible to thistreatment, as 103 CFU resulted in the death of all flies by 8 dpost-infection (dpi; Figure1A, top graph). In contrast, 77% and 55% of 8-d-old WTindividuals (flies 8 d old and older are hereafter referred to as“mature”) survived for 14 dpi with 103 and 106 CFUof E. coli K12, respectively (Figure 1A, middle graph).


Tsetse immune system maturation requires the presence of obligate symbionts in larvae.

Weiss BL, Wang J, Aksoy S - PLoS Biol. (2011)

Host survival correlates with symbiont status following septic infectionwith E. coli K12.(A) The effects of age and symbiont status on the survival of tsetse followingsystemic infection with E. coli K12. Mature adultGmmWgm- flies were significantly moresusceptible to infection with 106 CFU of E. colithan were their wild-type counterparts (bottom and middle panels;p<0.001). (B)GmmWT/Wgm− fliesharbored Wigglesworthia during immature development but lackedthe bacteria as mature adults. (C)GmmWT/Wgm− adults wereinfected with tetracycline resistant E. coli 1 d after theirlast antibiotic-supplemented blood meal. Unlike their counterparts that lackedWigglesworthia throughout immature development,GmmWT/Wgm− was able tosurvive infection with E. coli. No significant difference insurvival was observed between mature adult GmmWTversus GmmWT/Wgm− adultsinfected with 106 CFU of E. coli (Figure 1A middle panel andFigure 1C;p  = 0.07). (D) RelativeSodalis and Wolbachia densities in40-d-old GmmWT andGmmWgm− adults(n  = 5 of each) were normalizedagainst host β-tubulin copy number. (E) Analysis ofbacterial 16s rRNA clone libraries indicates thatGmmWT larvae harboredWigglesworthia, Sodalis, andWolbachia, while their counterparts from ampicillin treatedfemales harbored only Sodalis and Wolbachia.No other bacteria were identified from either fly line. (F) Average number(±SEM) of recE. colipIL per tsetse strainover time (n  = 3 individuals per strainper time point) following septic infection with 103 CFU of bacteria.Values shown in red represent lethal infections.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3104962&req=5

pbio-1000619-g001: Host survival correlates with symbiont status following septic infectionwith E. coli K12.(A) The effects of age and symbiont status on the survival of tsetse followingsystemic infection with E. coli K12. Mature adultGmmWgm- flies were significantly moresusceptible to infection with 106 CFU of E. colithan were their wild-type counterparts (bottom and middle panels;p<0.001). (B)GmmWT/Wgm− fliesharbored Wigglesworthia during immature development but lackedthe bacteria as mature adults. (C)GmmWT/Wgm− adults wereinfected with tetracycline resistant E. coli 1 d after theirlast antibiotic-supplemented blood meal. Unlike their counterparts that lackedWigglesworthia throughout immature development,GmmWT/Wgm− was able tosurvive infection with E. coli. No significant difference insurvival was observed between mature adult GmmWTversus GmmWT/Wgm− adultsinfected with 106 CFU of E. coli (Figure 1A middle panel andFigure 1C;p  = 0.07). (D) RelativeSodalis and Wolbachia densities in40-d-old GmmWT andGmmWgm− adults(n  = 5 of each) were normalizedagainst host β-tubulin copy number. (E) Analysis ofbacterial 16s rRNA clone libraries indicates thatGmmWT larvae harboredWigglesworthia, Sodalis, andWolbachia, while their counterparts from ampicillin treatedfemales harbored only Sodalis and Wolbachia.No other bacteria were identified from either fly line. (F) Average number(±SEM) of recE. colipIL per tsetse strainover time (n  = 3 individuals per strainper time point) following septic infection with 103 CFU of bacteria.Values shown in red represent lethal infections.
Mentions: Insects are normally capable of mounting an immune response that combats infectionwith various groups of bacteria. Interestingly, in comparison toDrosophila, tsetse flies are uniquely susceptible to septicinfection with 103 colony-forming units (CFU) of normally non-pathogenicEscherichia coli (E. coli) K12 [15]. In the presentstudy we further investigated tsetse's unique susceptibility to E.coli infection by subjecting wild-type(GmmWT) and adults from two age groups to hemocoelicinfections with varying quantities of E. coli K12. Three-day-oldGmmWT individuals (flies from this age group arehereafter referred to as “young”) were highly susceptible to thistreatment, as 103 CFU resulted in the death of all flies by 8 dpost-infection (dpi; Figure1A, top graph). In contrast, 77% and 55% of 8-d-old WTindividuals (flies 8 d old and older are hereafter referred to as“mature”) survived for 14 dpi with 103 and 106 CFUof E. coli K12, respectively (Figure 1A, middle graph).

Bottom Line: Adults that lack Wigglesworthia during larval development exhibit exceptionally compromised cellular and humoral immune responses following microbial challenge, including reduced expression of genes that encode antimicrobial peptides (cecropin and attacin), hemocyte-mediated processes (thioester-containing proteins 2 and 4 and prophenoloxidase), and signal-mediating molecules (inducible nitric oxide synthase).Furthermore, Gmm(Wgm-) adults harbor a reduced population of sessile and circulating hemocytes, a phenomenon that likely results from a significant decrease in larval expression of serpent and lozenge, both of which are associated with the process of early hemocyte differentiation.Our results demonstrate that Wigglesworthia must be present during the development of immature progeny in order for the immune system to function properly in adult tsetse.

View Article: PubMed Central - PubMed

Affiliation: Department of Epidemiology and Public Health, Division of Epidemiology of Microbial Diseases, Yale University School of Medicine, New Haven, Connecticut, United States of America. brian.weiss@yale.edu

ABSTRACT
Beneficial microbial symbionts serve important functions within their hosts, including dietary supplementation and maintenance of immune system homeostasis. Little is known about the mechanisms that enable these bacteria to induce specific host phenotypes during development and into adulthood. Here we used the tsetse fly, Glossina morsitans, and its obligate mutualist, Wigglesworthia glossinidia, to investigate the co-evolutionary adaptations that influence the development of host physiological processes. Wigglesworthia is maternally transmitted to tsetse's intrauterine larvae through milk gland secretions. We can produce flies that lack Wigglesworthia (Gmm(Wgm-) yet retain their other symbiotic microbes. Such offspring give rise to adults that exhibit a largely normal phenotype, with the exception being that they are reproductively sterile. Our results indicate that when reared under normal environmental conditions Gmm(Wgm-) adults are also immuno-compromised and highly susceptible to hemocoelic E. coli infections while age-matched wild-type individuals are refractory. Adults that lack Wigglesworthia during larval development exhibit exceptionally compromised cellular and humoral immune responses following microbial challenge, including reduced expression of genes that encode antimicrobial peptides (cecropin and attacin), hemocyte-mediated processes (thioester-containing proteins 2 and 4 and prophenoloxidase), and signal-mediating molecules (inducible nitric oxide synthase). Furthermore, Gmm(Wgm-) adults harbor a reduced population of sessile and circulating hemocytes, a phenomenon that likely results from a significant decrease in larval expression of serpent and lozenge, both of which are associated with the process of early hemocyte differentiation. Our results demonstrate that Wigglesworthia must be present during the development of immature progeny in order for the immune system to function properly in adult tsetse. This phenomenon provides evidence of yet another important physiological adaptation that further anchors the obligate symbiosis between tsetse and Wigglesworthia.

Show MeSH
Related in: MedlinePlus