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Pathogenicity of Leishmania donovani is associated with the high expression of a group low molecular weight proteins.

Mitra P - Trop Parasitol (2015 Jul-Dec)

Bottom Line: It has been proposed that the loss of pathogenicity is associated with the gradual disappearance of selective parasite proteins.We observed a gradual and significant downregulation of expression of a group of low molecular weight proteins (LMW, molecular weight 20-30 kDa) which are associated with loss of pathogenicity.Therefore, our data strongly support the hypothesis that the loss of pathogenicity of L. donovani is associated with a change in antigenic profile, but not due the selective deletion of pathogenic clones.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacy, University of Queensland, Woolloongabba, QLD 4122, Australia.

ABSTRACT

Background: With few exceptions, members of the Leishmania donovani complex such as L. donovani, L. infantum and L. chagashi are the etiological agents of visceral leishmaniasis or kala-azar. Promastigotes of Leishmania spp. lose their Pathogenicity; the ability to establish infection in a susceptible host, after prolonged culture. The molecular basis of this evolution of pathogenic to nonpathogenic culture has not been very well understood. It has been proposed that the loss of pathogenicity is associated with the gradual disappearance of selective parasite proteins. An alternative hypothesis is that during prolonged culture, the pathogenic clonal population of the parasite is deleted from the mixed population due to their selection pressure. This clonal deletion is proposed to be responsible for the emergence of the nonpathogenic population.

Study methodology and results: We have a done a series of two-dimensional polyacrylamide gel electrophoresis followed by western blot experiments to study the antigenic profile of few L. donovani isolates of Indian origin. We observed a gradual and significant downregulation of expression of a group of low molecular weight proteins (LMW, molecular weight 20-30 kDa) which are associated with loss of pathogenicity. These proteins are recognized only by antiserum raised against the whole cell extract of one of the pathogenic Indian L. donovani isolates, Ag83, and remained undetected by antiserum raised against the nonpathogenic AG83 isolates. These LMW proteins were also present in the nonpathogenic extract in very low levels and remained undetected by the virulent serum, indicating a phenomenon of simultaneous downregulation of the expression and altered immunogenicity. LMW proteins were universally expressed in all early passage Indian isolate we tested and also detected in two clones obtained from pathogenic parasite culture. The antigenic patterns of none of the eight clones obtained from nonpathogenic culture were not exactly similar with the pathogenic clones.

Conclusion: Therefore, our data strongly support the hypothesis that the loss of pathogenicity of L. donovani is associated with a change in antigenic profile, but not due the selective deletion of pathogenic clones.

No MeSH data available.


Related in: MedlinePlus

All Leishmania donovani Indian isolates express low molecular weight proteins besides maintaining noticeable antigenic diversity. All Indian isolates of Leishmania donovani promastigotes extracts were analyzed by two-dimensional polyacrylamide gel electrophoresis followed by immunoblot experiment with virulent serum. AG83 (a), GE1 (b), GE2 (c), RS (d) and SL (5e) express low molecular weight enclosed by square. Isolate specific immunoreactive proteins, such as in GE1 and SL, are also marked by arrows outside the square
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Figure 7: All Leishmania donovani Indian isolates express low molecular weight proteins besides maintaining noticeable antigenic diversity. All Indian isolates of Leishmania donovani promastigotes extracts were analyzed by two-dimensional polyacrylamide gel electrophoresis followed by immunoblot experiment with virulent serum. AG83 (a), GE1 (b), GE2 (c), RS (d) and SL (5e) express low molecular weight enclosed by square. Isolate specific immunoreactive proteins, such as in GE1 and SL, are also marked by arrows outside the square

Mentions: Antigenic diversity in parasites such as Leishmania is a very well established phenomenon. In one of the recent demonstrations, Forgber et al. showed a distinct diversity among the immunoreactive L. donovani proteins isolated from several endemic zones of a particular region of India.[13] The GE1 and GE2 isolates were obtained in one of the endemic zones in India (Bihar), and RS and SL were isolated from patients from another distinct endemic zone in India (Kolkata). We were also interested to check the expression of this LMW immunoreactive parasite proteins among the isolates collected from several endemic areas. Therefore, besides AG83, we analyzed immunoreactive protein profiles of pathogenic promastigote isolates such as GE1, GE2, RS, and SL using the virulent and avirulent serum. An overall similarity in immunoreactive protein profile were observed among the L. donovani isolates generated by the virulent serum as depicted in Figure 5a-e. Few extra cross reactive proteins are also detected in GE2 [Figure 5c] and SL [Figure 5e] isolates (marked by arrow) indicating the antigenic diversity among the isolates. However, besides this antigenic diversity, the LMW proteins (enclosed by the box) are expressed by all L. donovani isolates tested. In order to confirm their pathogenic promastigote specific expression, GE1, GE2, and SL isolate extracts were analyzed by 2D-PAGE-immunoblot experiments using avirulent antiserum. As it has been observed previously for AG83 isolates, these LMW proteins were not detected by this antiserum. It is also important to note that majority of the immunoreactive proteins of pathogenic isolates show a very weak recognition by avirulent serum [Figure 6]. Therefore, we conclude that: (i) Antigenic polymorphism exists among the Indian L. donovani isolates; (ii) a significant change is observed in immunoreactivity of pathogenic and nonpathogenic proteins; and (iii) among the immunoreactive proteins a group of LMW proteins with conserved antigenicity is expressed ubiquitously in all L. donovani isolates of Indian origin.


Pathogenicity of Leishmania donovani is associated with the high expression of a group low molecular weight proteins.

Mitra P - Trop Parasitol (2015 Jul-Dec)

All Leishmania donovani Indian isolates express low molecular weight proteins besides maintaining noticeable antigenic diversity. All Indian isolates of Leishmania donovani promastigotes extracts were analyzed by two-dimensional polyacrylamide gel electrophoresis followed by immunoblot experiment with virulent serum. AG83 (a), GE1 (b), GE2 (c), RS (d) and SL (5e) express low molecular weight enclosed by square. Isolate specific immunoreactive proteins, such as in GE1 and SL, are also marked by arrows outside the square
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4557149&req=5

Figure 7: All Leishmania donovani Indian isolates express low molecular weight proteins besides maintaining noticeable antigenic diversity. All Indian isolates of Leishmania donovani promastigotes extracts were analyzed by two-dimensional polyacrylamide gel electrophoresis followed by immunoblot experiment with virulent serum. AG83 (a), GE1 (b), GE2 (c), RS (d) and SL (5e) express low molecular weight enclosed by square. Isolate specific immunoreactive proteins, such as in GE1 and SL, are also marked by arrows outside the square
Mentions: Antigenic diversity in parasites such as Leishmania is a very well established phenomenon. In one of the recent demonstrations, Forgber et al. showed a distinct diversity among the immunoreactive L. donovani proteins isolated from several endemic zones of a particular region of India.[13] The GE1 and GE2 isolates were obtained in one of the endemic zones in India (Bihar), and RS and SL were isolated from patients from another distinct endemic zone in India (Kolkata). We were also interested to check the expression of this LMW immunoreactive parasite proteins among the isolates collected from several endemic areas. Therefore, besides AG83, we analyzed immunoreactive protein profiles of pathogenic promastigote isolates such as GE1, GE2, RS, and SL using the virulent and avirulent serum. An overall similarity in immunoreactive protein profile were observed among the L. donovani isolates generated by the virulent serum as depicted in Figure 5a-e. Few extra cross reactive proteins are also detected in GE2 [Figure 5c] and SL [Figure 5e] isolates (marked by arrow) indicating the antigenic diversity among the isolates. However, besides this antigenic diversity, the LMW proteins (enclosed by the box) are expressed by all L. donovani isolates tested. In order to confirm their pathogenic promastigote specific expression, GE1, GE2, and SL isolate extracts were analyzed by 2D-PAGE-immunoblot experiments using avirulent antiserum. As it has been observed previously for AG83 isolates, these LMW proteins were not detected by this antiserum. It is also important to note that majority of the immunoreactive proteins of pathogenic isolates show a very weak recognition by avirulent serum [Figure 6]. Therefore, we conclude that: (i) Antigenic polymorphism exists among the Indian L. donovani isolates; (ii) a significant change is observed in immunoreactivity of pathogenic and nonpathogenic proteins; and (iii) among the immunoreactive proteins a group of LMW proteins with conserved antigenicity is expressed ubiquitously in all L. donovani isolates of Indian origin.

Bottom Line: It has been proposed that the loss of pathogenicity is associated with the gradual disappearance of selective parasite proteins.We observed a gradual and significant downregulation of expression of a group of low molecular weight proteins (LMW, molecular weight 20-30 kDa) which are associated with loss of pathogenicity.Therefore, our data strongly support the hypothesis that the loss of pathogenicity of L. donovani is associated with a change in antigenic profile, but not due the selective deletion of pathogenic clones.

View Article: PubMed Central - PubMed

Affiliation: Department of Pharmacy, University of Queensland, Woolloongabba, QLD 4122, Australia.

ABSTRACT

Background: With few exceptions, members of the Leishmania donovani complex such as L. donovani, L. infantum and L. chagashi are the etiological agents of visceral leishmaniasis or kala-azar. Promastigotes of Leishmania spp. lose their Pathogenicity; the ability to establish infection in a susceptible host, after prolonged culture. The molecular basis of this evolution of pathogenic to nonpathogenic culture has not been very well understood. It has been proposed that the loss of pathogenicity is associated with the gradual disappearance of selective parasite proteins. An alternative hypothesis is that during prolonged culture, the pathogenic clonal population of the parasite is deleted from the mixed population due to their selection pressure. This clonal deletion is proposed to be responsible for the emergence of the nonpathogenic population.

Study methodology and results: We have a done a series of two-dimensional polyacrylamide gel electrophoresis followed by western blot experiments to study the antigenic profile of few L. donovani isolates of Indian origin. We observed a gradual and significant downregulation of expression of a group of low molecular weight proteins (LMW, molecular weight 20-30 kDa) which are associated with loss of pathogenicity. These proteins are recognized only by antiserum raised against the whole cell extract of one of the pathogenic Indian L. donovani isolates, Ag83, and remained undetected by antiserum raised against the nonpathogenic AG83 isolates. These LMW proteins were also present in the nonpathogenic extract in very low levels and remained undetected by the virulent serum, indicating a phenomenon of simultaneous downregulation of the expression and altered immunogenicity. LMW proteins were universally expressed in all early passage Indian isolate we tested and also detected in two clones obtained from pathogenic parasite culture. The antigenic patterns of none of the eight clones obtained from nonpathogenic culture were not exactly similar with the pathogenic clones.

Conclusion: Therefore, our data strongly support the hypothesis that the loss of pathogenicity of L. donovani is associated with a change in antigenic profile, but not due the selective deletion of pathogenic clones.

No MeSH data available.


Related in: MedlinePlus