AO Oluwasola1, JA Otegbayo2, SO Ola2, HO Ebili1, AO Afolabi3 and GN Odaibo4
- Department of Pathology, University College Hospital, Ibadan, Nigeria.
- Department of Medicine, University College Hospital, Ibadan, Nigeria.
- Department of Surgery, University College Hospital, Ibadan, Nigeria.
- Department of Virology, University College Hospital, Ibadan, Nigeria.
Abstract
Background: The sero prevalence of anti-H. pylori IgA antibodies has been reported to vary among populations and in relation to strains of Helicobacter
pylori bacterium. However, there has been conflicting reports on the association between IgA serological status and the histological variables of chronic gastritis. This study was therefore conducted to clarify this relationship.
Method: Using an ELISA based commercial kit, anti-H. pylori IgA antibody tests were performed on 65 dyspeptic patients and 65 age- and sex-matched controls. The gastric biopsies of these patients were also examined histologically for the degrees of inflammation, activity, intestinal metaplasia and atrophy. The CagA status of the patients had been determined previously.
Results: There was an anti-H. pylori IgA antibody prevalence of 67.7% in dyspeptics and 56.9% in non-dyspeptic individuals. No correlations were observed between serumH. pylori IgA antibody and the graded parameters of chronic gastritis in dyspeptic patients, although twice more patients with mild gastric inflammation were found among IgA positive than among IgA negative patients. However, a statistically significant relationship was established between serum IgA positivity and the CagA status of the patients (p = 0.028).
Conclusion: The seroprevalence of anti-H. pylori IgA antibody is high in our environment. Serum IgA status may be associated with milder degrees of gastritis in our patients but a larger cohort of patients is needed to confirm this. There seems to be a good agreement between serum IgA and CagA statuses among dyspeptic patients.
Correspondence:
Dr. A.O Oluwasola,
Department of Pathology,
College of Medicine,
University of Ibadan,
PMB 5116, Ibadan,
Nigeria
Introduction
It is now established that Helicobacter pylori (H. pylori), which is believed to be the commonest bacterial infection of man, is the major causative agent of chronic gastritis.1 This chronic inflammation of gastric mucosa which is histologically characterized by mucosal infiltration by plasma cells has been associated with detectable levels of specific anti-H. pylori antibodies of the IgA and IgG classes.2 Helicobacter pylori infection is usually lifelong, especially in untreated individuals, and eventually results in atrophic changes, gastric ulcers and cancers.3 Specific antibodies of the IgA class are usually detected in about two-thirds of patients with raised IgG levels, and in a further 2-7% of IgG-negative patients.4
The IgA sero-prevalence of Helicobacter pylori is highly variable from population to population. From available literature, it appears the anti-H. pylori antibody sero seroprevalence is higher in developing countries than in developed countries.5 This is because H. pylori infection is associated with low socioeconomic status and low standards of hygiene that more often characterize the developing than the developed countries.6
Soluble cellular antigens such as urease and heat shock protein,7-10 a vacuolating cytotoxin,11,12 and, more recently, a 128-kDa protein (CagA) associated with cytotoxin production13 have been suggested as possible inducers of an inflammatory reaction in the gastric mucosa14,15 and could explain how bacteria living in the mucus layer can produce histological lesions in the full thickness of the mucosa.3 In addition, it has been suggested that intensity and specificity of the mucosal immune response may correlate with the level of tissue inflammation.16
It has been established that subjects seropositive for CagA protein more often have IgA antibody than CagA negative subjects.17-21 Even though H. pylori stimulate both local and systemic antibody responses, the role of IgA antibody with respect to bacterial colonization and gastric inflammation is still controversial.
Following detailed search of the English literature, it seems that this is the first study in Nigeria and possibly in sub-Saharan Africa to have evaluated the association between anti-H. pylori IgA and histological parameters of chronic gastritis as most sero-prevalence studies on H. pylori in Nigeria focused on IgG levels.22-26 We therefore investigated the anti-H. pylori IgA serology in chronic gastritis by determining the sero-prevalence of H. pylori IgA antibody in dyspeptics and in the general population and the relationship between anti- H. pylori IgA antibody positivity and the histological variables in chronic gastritis. We also evaluated if the presence of serum H. pylori IgA antibody is associated more often with serum cag-A positive subjects than with cag-A negative ones.
MATERIALS AND METHODS
This was a prospective study of 64 consecutive adult patients with dyspeptic symptoms who underwent endoscopy at the Gastrointestinal and Liver Unit of the University College Hospital, Ibadan, Nigeria.
The patients who were previously treated for H. pylori infection or who had received antibiotics, proton pump inhibitors or bismuth compounds in the preceding 4 weeks were excluded. Base line bio data were obtained. Oesophago-gastro-duodenoscopy (OGD) was performed on all the participants using Olympus (GFIXQ20) or Pentax (FG29W) forwardviewing Oesophago-gastro-duodenoscope. A minimum of two gastric antral mucosal biopsies were taken from each patient for histology.
The two endoscopic biopsies were fixed in 10% formaldehyde and transferred to the histopathology laboratory of the hospital for processing. Four micron thick paraffin sections were stained with routine Haematoxylin and Eosin for the diagnosis of chronic gastritis. Sections were examined microscopically for the histological changes of gastritis and two of the histological variables (degree of chronic inflammation and activity) were graded based on the revised Sydney System,27 while the mucosal atrophy and intestinal metaplasia were graded as either present or absent.
Five millilitres of venous blood was collected from all the recruited patients and 64 randomly selected ageand sex-matched controls for IgA serology testing. Serological analysis was performed in the serological unit of the Department of Virology of the institution. The presence/ absence of serum anti-H. pylori IgA antibodies to H. pylori immunodominant antigens was determined by Enzyme Linked Immune-Sorbent Assay (ELISA) [ (Dia.Pro Diagnostic Bioprobes srl Milano Italy] and the results were recorded as either positive or negative. The CagA status of the same set of patients and controls had been determined previously with a similar commercial ELISA kit.
Data were analysed using Statistical Package for Social Sciences, version16.0 (SPSS Inc. Chicago Illinois). Results were presented as means ± standard deviation for quantitative variables and number (percentages) for qualitative variables. Categorical variables were compared with Pearson’s Chi-square. Significant Pvalue was taken as <0.05.
The study was conducted in compliance with the guidelines of the Helsinki declaration on biomedical research in human subjects. Informed consent was obtained and the confidentiality of the patients’ identity and personal health information was maintained.