Reviewer's report
Title:Higher Frequency of cagA EPIYA-C Phosphorylation Sites in H. pylori
Strains from First-degree Relatives of Gastric Cancer Patients
Version: 2Date:24 May 2012
Reviewer: Richard Harry Argent
Reviewer's report:
This study examined the prevalence of H. pylori and associated virulence factors
(VacA, CagA) in relatives of gastric cancer patients from Brazil. The authors
conclude that more virulent strains of H. pylori colonise relatives of gastric cancer
patients.
MAJOR REVISIONS
1) This paper fails to cite, or compare, the article of Argent et al. (2008) Clin
Cancer Res 14, 2227-35, that previously looked at relatives of gastric cancer
patients from Scotland, that also examined whether H. pylori strains from
first-degree relatives of gastric cancer were the same, and whether they had
evolved with vacA and cagA. This article also examined associations with
hypochlorhydria. The penultimate paragraph of the Introduction is therefore
incorrect!
2) Results - all strains of H. pylori possess vacA, so why are the data for 6 strains
missing from Table 3? Did only those strains possessing s2m2 vacA lack cagA?
No i-region typing, particularly of s1m2 vacA was performed. Is the frequency of
vacA mosaicism distribution significant - data would suggest not - a Chi-squared
analysis of data in Table 3 is not significant.
3) Results - the deduced amino acid sequences of the cagA variable regions
should be shown. Additionally, the presence of cagA does not necessarily
indicate the presence of a functional pathogenicity island, so some caution is
required when interpreting the data.
4) Results - Table 4 - how many s1m1 vacA strains also possessed more than
one EPIYA-C motif? How does this alter the significance between groups? I am
unclear how the multivariate analysis was performed, but, from point (2) above I
would expect that the vacA data to be non-significant (as in the univariate
analysis).
MINOR REVISIONS
5) Table 1 seems fairly redundant, and could just be included in the text of the
Methods.
6) Figure 1 - without the corresponding nucleotide sequencing data, the
interpretation of the bands is pure conjecture.
7) Results - final section - the data for these statements should be provided!
8) Introduction - "gram" should be written as "Gram"; "aminoacid" should be
written as "amino acid"; "(MALT)" should be deleted as abbreviation never used
again; paragraph 3, line 7 - don't think "peptides" is correct; paragraph 4, line 4 -
CagA can possess more than 3 EPIYA-C motifs.
9) Methods - vacA and cagA detection - Tx30a possesses a s2m2 VacA, so lines
7-8 are incorrect.
10) Methods - amplification of cagA VR section - pH of Tris used should be
stated, and presumably 1.0 units of Taq were used.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: Yes, but I do not feel adequately qualified to assess the
statistics.
Declaration of competing interests:
I declare that I have no competing interests
Reviewer's report
Title:Higher Frequency of cagA EPIYA-C Phosphorylation Sites in H. pylori
Strains from First-degree Relatives of Gastric Cancer Patients
Version: 2Date:24 May 2012
Reviewer: Richard Harry Argent
Reviewer's report:
This study examined the prevalence of H. pylori and associated virulence factors
(VacA, CagA) in relatives of gastric cancer patients from Brazil. The authors
conclude that more virulent strains of H. pylori colonise relatives of gastric cancer
patients.
MAJOR REVISIONS
1) This paper fails to cite, or compare, the article of Argent et al. (2008) Clin
Cancer Res 14, 2227-35, that previously looked at relatives of gastric cancer
patients from Scotland, that also examined whether H. pylori strains from
first-degree relatives of gastric cancer were the same, and whether they had
evolved with vacA and cagA. This article also examined associations with
hypochlorhydria. The penultimate paragraph of the Introduction is therefore
incorrect!
2) Results - all strains of H. pylori possess vacA, so why are the data for 6 strains
missing from Table 3? Did only those strains possessing s2m2 vacA lack cagA?
No i-region typing, particularly of s1m2 vacA was performed. Is the frequency of
vacA mosaicism distribution significant - data would suggest not - a Chi-squared
analysis of data in Table 3 is not significant.
3) Results - the deduced amino acid sequences of the cagA variable regions
should be shown. Additionally, the presence of cagA does not necessarily
indicate the presence of a functional pathogenicity island, so some caution is
required when interpreting the data.
4) Results - Table 4 - how many s1m1 vacA strains also possessed more than
one EPIYA-C motif? How does this alter the significance between groups? I am
unclear how the multivariate analysis was performed, but, from point (2) above I
would expect that the vacA data to be non-significant (as in the univariate
analysis).
MINOR REVISIONS
5) Table 1 seems fairly redundant, and could just be included in the text of the
Methods.
6) Figure 1 - without the corresponding nucleotide sequencing data, the
interpretation of the bands is pure conjecture.
7) Results - final section - the data for these statements should be provided!
8) Introduction - "gram" should be written as "Gram"; "aminoacid" should be
written as "amino acid"; "(MALT)" should be deleted as abbreviation never used
again; paragraph 3, line 7 - don't think "peptides" is correct; paragraph 4, line 4 -
CagA can possess more than 3 EPIYA-C motifs.
9) Methods - vacA and cagA detection - Tx30a possesses a s2m2 VacA, so lines
7-8 are incorrect.
10) Methods - amplification of cagA VR section - pH of Tris used should be
stated, and presumably 1.0 units of Taq were used.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: Yes, but I do not feel adequately qualified to assess the
statistics.
Declaration of competing interests:
I declare that I have no competing interests
Please review this paper.
user
Reviewer's report
Title:Higher Frequency of cagA EPIYA-C Phosphorylation Sites in H. pylori
Strains from First-degree Relatives of Gastric Cancer Patients
Version: 2Date:24 May 2012
Reviewer: Richard Harry Argent
Reviewer's report:
This study examined the prevalence of H. pylori and associated virulence factors
(VacA, CagA) in relatives of gastric cancer patients from Brazil. The authors
conclude that more virulent strains of H. pylori colonise relatives of gastric cancer
patients.
MAJOR REVISIONS
1) This paper fails to cite, or compare, the article of Argent et al. (2008) Clin
Cancer Res 14, 2227-35, that previously looked at relatives of gastric cancer
patients from Scotland, that also examined whether H. pylori strains from
first-degree relatives of gastric cancer were the same, and whether they had
evolved with vacA and cagA. This article also examined associations with
hypochlorhydria. The penultimate paragraph of the Introduction is therefore
incorrect!
2) Results - all strains of H. pylori possess vacA, so why are the data for 6 strains
missing from Table 3? Did only those strains possessing s2m2 vacA lack cagA?
No i-region typing, particularly of s1m2 vacA was performed. Is the frequency of
vacA mosaicism distribution significant - data would suggest not - a Chi-squared
analysis of data in Table 3 is not significant.
3) Results - the deduced amino acid sequences of the cagA variable regions
should be shown. Additionally, the presence of cagA does not necessarily
indicate the presence of a functional pathogenicity island, so some caution is
required when interpreting the data.
4) Results - Table 4 - how many s1m1 vacA strains also possessed more than
one EPIYA-C motif? How does this alter the significance between groups? I am
unclear how the multivariate analysis was performed, but, from point (2) above I
would expect that the vacA data to be non-significant (as in the univariate
analysis).
MINOR REVISIONS
5) Table 1 seems fairly redundant, and could just be included in the text of the
Methods.
6) Figure 1 - without the corresponding nucleotide sequencing data, the
interpretation of the bands is pure conjecture.
7) Results - final section - the data for these statements should be provided!
8) Introduction - "gram" should be written as "Gram"; "aminoacid" should be
written as "amino acid"; "(MALT)" should be deleted as abbreviation never used
again; paragraph 3, line 7 - don't think "peptides" is correct; paragraph 4, line 4 -
CagA can possess more than 3 EPIYA-C motifs.
9) Methods - vacA and cagA detection - Tx30a possesses a s2m2 VacA, so lines
7-8 are incorrect.
10) Methods - amplification of cagA VR section - pH of Tris used should be
stated, and presumably 1.0 units of Taq were used.
Level of interest: An article whose findings are important to those with closely
related research interests
Quality of written English: Acceptable
Statistical review: Yes, but I do not feel adequately qualified to assess the
statistics.
Declaration of competing interests:
I declare that I have no competing interests
assistant