Table 2 ELISA screening of candidate peptides identified by NGPD as being enriched against IgY from Salmonella infected chickens compared to from animals vaccinated with an attenuated vaccine.

From: Mapping B-cell responses to Salmonella enterica serovars Typhimurium and Enteritidis in chickens for the discrimination of infected from vaccinated animals

Peptide sequencea

In silico assessmentb

ELISA assessment

AUC of ROCc

sensitivityd

specificityd

AEGEFQNLQIRHRT

8/10

1

94

100

AEGEFTQTKRNMSW

5/10

0.997

77

100

CPSTLRQPCSCG

5/10

1

80

100

AEGEFLPKHKQNGG

4/10

1

54

100

AEGEFFAASCTRQL

4/10

0.938

91

100

CSIFQYTALQCG

4/10

1

40

100

AEGEFTAARSNHQP

4/10

1

89

100

AEGEFAQNSHLYPQ

4/10

0.966

69

100

AEGEFLSTMARSRS

4/10

0.981

74

100

CQTAVPSFMVCG

4/10

0.903

66

100

CIALQQVCGLCG

4/10

0.894

34

100

CPTRVIQPKPCG

4/10

0.984

71

100

Control peptide

—

0.588

—

—

  1. aResidues coded for by a stop codon were replaced by a Q in the synthesised peptide. Flanking cysteine residues for constrained peptides are underlined.
  2. bNumber of IgY samples that the peptide was very highly enriched against/total number of IgY samples: very high enrichment was defined using a Z score cut-off of ≥8.0.
  3. cROC curves were produced for the recognition of peptides with IgY from a training set of samples: infected (n = 8 for S. Typhimurium and n = 9 for S. Enteritidis) and vaccinated (n = 10) chickens, AUC values are listed, for all peptides the associated p values were <0.001. The control peptide associated p value was 0.451.
  4. dSensitivity and specificity values were calculated from data for IgY binding to each peptide from infected (n = 16 for S. Typhimurium and 19 for S. Enteritidis) and vaccinated (n = 20) chickens using cut-off values for each peptide calculated as the mean ELISA signal for the vaccinate samples in the training set (10 vaccinates used in the panning steps) plus 5SD. Sensitivity was calculated as the % of infected chickens that gave signals above the cut-off value and the specificity is the % of vaccinates that gave signals below the cut-off value.
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