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Identification of cryptic Anopheles mosquito species by molecular protein profiling.

Müller P, Pflüger V, Wittwer M, Ziegler D, Chandre F, Simard F, Lengeler C - PLoS ONE (2013)

Bottom Line: The approach also classifies specimens from different laboratory colonies; hence proving also very promising for its use in colony authentication as part of quality assurance in laboratory studies.While being exceptionally accurate and robust, MALDI-TOF MS has several advantages over other typing methods, including simple sample preparation and short processing time.As the method does not require DNA sequence information, data can also be reviewed at any later stage for diagnostic or functional patterns without the need for re-designing and re-processing biological material.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Services and Diagnostic, Swiss Tropical and Public Health Institute, Basel, Switzerland. pie.mueller@unibas.ch

ABSTRACT
Vector control is the mainstay of malaria control programmes. Successful vector control profoundly relies on accurate information on the target mosquito populations in order to choose the most appropriate intervention for a given mosquito species and to monitor its impact. An impediment to identify mosquito species is the existence of morphologically identical sibling species that play different roles in the transmission of pathogens and parasites. Currently PCR diagnostics are used to distinguish between sibling species. PCR based methods are, however, expensive, time-consuming and their development requires a priori DNA sequence information. Here, we evaluated an inexpensive molecular proteomics approach for Anopheles species: matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). MALDI-TOF MS is a well developed protein profiling tool for the identification of microorganisms but so far has received little attention as a diagnostic tool in entomology. We measured MS spectra from specimens of 32 laboratory colonies and 2 field populations representing 12 Anopheles species including the A. gambiae species complex. An important step in the study was the advancement and implementation of a bioinformatics approach improving the resolution over previously applied cluster analysis. Borrowing tools for linear discriminant analysis from genomics, MALDI-TOF MS accurately identified taxonomically closely related mosquito species, including the separation between the M and S molecular forms of A. gambiae sensu stricto. The approach also classifies specimens from different laboratory colonies; hence proving also very promising for its use in colony authentication as part of quality assurance in laboratory studies. While being exceptionally accurate and robust, MALDI-TOF MS has several advantages over other typing methods, including simple sample preparation and short processing time. As the method does not require DNA sequence information, data can also be reviewed at any later stage for diagnostic or functional patterns without the need for re-designing and re-processing biological material.

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Model selection and cross-validation to distinguish molecular M and S forms in Anopheles gambiae sensu stricto (Model 2).(A) Error rate of the cross-validation plotted as a function of the number of the ranked peaks included in the SDA Model 2 that classifies M and S molecular forms among A. gambiae s.s. The peaks were ranked according to the correlation-adjusted t-scores (CAT scores). The vertical, red line shows 31 chosen peaks for the SDA model. (B) The 31 peaks listed on the left were selected on the basis of the smallest number of peaks still providing the lowest error rate shown in (A) and were ranked according to their CAT scores (Table S3). The length and direction of the horizontal blue bars represents the CAT scores of the centroid versus the pooled mean and shows the influence of a particular peak in differentiating between the two molecular forms. M: A. gambiae s.s. molecular M form; S: A. gambiae s.s. molecular S form.
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pone-0057486-g005: Model selection and cross-validation to distinguish molecular M and S forms in Anopheles gambiae sensu stricto (Model 2).(A) Error rate of the cross-validation plotted as a function of the number of the ranked peaks included in the SDA Model 2 that classifies M and S molecular forms among A. gambiae s.s. The peaks were ranked according to the correlation-adjusted t-scores (CAT scores). The vertical, red line shows 31 chosen peaks for the SDA model. (B) The 31 peaks listed on the left were selected on the basis of the smallest number of peaks still providing the lowest error rate shown in (A) and were ranked according to their CAT scores (Table S3). The length and direction of the horizontal blue bars represents the CAT scores of the centroid versus the pooled mean and shows the influence of a particular peak in differentiating between the two molecular forms. M: A. gambiae s.s. molecular M form; S: A. gambiae s.s. molecular S form.

Mentions: Remarkably, by using the SDA approach it was possible to come up with a SDA model (Model 2) that allows for discriminating between the M and S molecular forms of A. gambiae s.s. (Figure 5 and Table S3). Among the 11 laboratory colonies (8 S and 3 M form colonies; Table 2) 50 out of 55 (91%) individuals that were not used to build the model were still correctly identified as either M or S form with 31 peaks in the model (Table S1).


Identification of cryptic Anopheles mosquito species by molecular protein profiling.

Müller P, Pflüger V, Wittwer M, Ziegler D, Chandre F, Simard F, Lengeler C - PLoS ONE (2013)

Model selection and cross-validation to distinguish molecular M and S forms in Anopheles gambiae sensu stricto (Model 2).(A) Error rate of the cross-validation plotted as a function of the number of the ranked peaks included in the SDA Model 2 that classifies M and S molecular forms among A. gambiae s.s. The peaks were ranked according to the correlation-adjusted t-scores (CAT scores). The vertical, red line shows 31 chosen peaks for the SDA model. (B) The 31 peaks listed on the left were selected on the basis of the smallest number of peaks still providing the lowest error rate shown in (A) and were ranked according to their CAT scores (Table S3). The length and direction of the horizontal blue bars represents the CAT scores of the centroid versus the pooled mean and shows the influence of a particular peak in differentiating between the two molecular forms. M: A. gambiae s.s. molecular M form; S: A. gambiae s.s. molecular S form.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3585343&req=5

pone-0057486-g005: Model selection and cross-validation to distinguish molecular M and S forms in Anopheles gambiae sensu stricto (Model 2).(A) Error rate of the cross-validation plotted as a function of the number of the ranked peaks included in the SDA Model 2 that classifies M and S molecular forms among A. gambiae s.s. The peaks were ranked according to the correlation-adjusted t-scores (CAT scores). The vertical, red line shows 31 chosen peaks for the SDA model. (B) The 31 peaks listed on the left were selected on the basis of the smallest number of peaks still providing the lowest error rate shown in (A) and were ranked according to their CAT scores (Table S3). The length and direction of the horizontal blue bars represents the CAT scores of the centroid versus the pooled mean and shows the influence of a particular peak in differentiating between the two molecular forms. M: A. gambiae s.s. molecular M form; S: A. gambiae s.s. molecular S form.
Mentions: Remarkably, by using the SDA approach it was possible to come up with a SDA model (Model 2) that allows for discriminating between the M and S molecular forms of A. gambiae s.s. (Figure 5 and Table S3). Among the 11 laboratory colonies (8 S and 3 M form colonies; Table 2) 50 out of 55 (91%) individuals that were not used to build the model were still correctly identified as either M or S form with 31 peaks in the model (Table S1).

Bottom Line: The approach also classifies specimens from different laboratory colonies; hence proving also very promising for its use in colony authentication as part of quality assurance in laboratory studies.While being exceptionally accurate and robust, MALDI-TOF MS has several advantages over other typing methods, including simple sample preparation and short processing time.As the method does not require DNA sequence information, data can also be reviewed at any later stage for diagnostic or functional patterns without the need for re-designing and re-processing biological material.

View Article: PubMed Central - PubMed

Affiliation: Department of Medical Services and Diagnostic, Swiss Tropical and Public Health Institute, Basel, Switzerland. pie.mueller@unibas.ch

ABSTRACT
Vector control is the mainstay of malaria control programmes. Successful vector control profoundly relies on accurate information on the target mosquito populations in order to choose the most appropriate intervention for a given mosquito species and to monitor its impact. An impediment to identify mosquito species is the existence of morphologically identical sibling species that play different roles in the transmission of pathogens and parasites. Currently PCR diagnostics are used to distinguish between sibling species. PCR based methods are, however, expensive, time-consuming and their development requires a priori DNA sequence information. Here, we evaluated an inexpensive molecular proteomics approach for Anopheles species: matrix assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). MALDI-TOF MS is a well developed protein profiling tool for the identification of microorganisms but so far has received little attention as a diagnostic tool in entomology. We measured MS spectra from specimens of 32 laboratory colonies and 2 field populations representing 12 Anopheles species including the A. gambiae species complex. An important step in the study was the advancement and implementation of a bioinformatics approach improving the resolution over previously applied cluster analysis. Borrowing tools for linear discriminant analysis from genomics, MALDI-TOF MS accurately identified taxonomically closely related mosquito species, including the separation between the M and S molecular forms of A. gambiae sensu stricto. The approach also classifies specimens from different laboratory colonies; hence proving also very promising for its use in colony authentication as part of quality assurance in laboratory studies. While being exceptionally accurate and robust, MALDI-TOF MS has several advantages over other typing methods, including simple sample preparation and short processing time. As the method does not require DNA sequence information, data can also be reviewed at any later stage for diagnostic or functional patterns without the need for re-designing and re-processing biological material.

Show MeSH
Related in: MedlinePlus