Does latent Toxoplasma infection have a protective effect against developing multiple sclerosis? Evidence from an updated meta-analysis

Chlamydia pneumonia infection and risk of multiple sclerosis: A meta-analysis

BACKGROUND

The role of infectious agents, including Chlamydia pneumoniae (Cpn), in the development of multiple sclerosis (MS), is still a matter of major contention.

OBJECTIVE

This meta-analysis study aimed to assess the actual involvement of Cpn in MS development.

METHODS

We undertook a search of international scientific databases to identify eligible studies. We used a random-effects meta-analysis model (REM) to generate the pooled odds ratio (OR) and 95% confidence intervals (CIs). Heterogeneity was calculated using the I2 statistic. Sensitivity and subgroup analyses were applied to assess the effects of study characteristics and socio-demographic variables on the pooled OR.

RESULTS

We identified 37 studies comprising 51 datasets that satisfied the inclusion criteria. Considering diagnostic methods for Cpn, 26 and 25 datasets used PCR- and serological-based methods, respectively. In PCR-based datasets, REM showed a significant positive association between Cpn infection and the development of MS (OR, 5.29; 95% CI, 3.12-8.97), while a non-significant positive association was achieved in serological-based datasets (OR, 1.34; 95% CI, 0.88-2.03). In subgroup analyses on PCR-based datasets, results were significant for both CSF (OR, 5.70) and serum (OR, 4.84) samples; both healthy (OR, 16.11) and hospital-based (OR, 2.88) controls; and both moderate (OR, 5.14) and high (OR, 5.48) quality studies. In serological-based datasets, only those that used CSF samples yielded significant results (OR, 3.41).

CONCLUSIONS

Our findings verify the significant positive relationship between Cpn infection and MS. We advocate prospective cohort studies with lifelong follow-ups and also experimental studies to better understand the role of Cpn in MS development.

Helicobacter pylori infection and risk of multiple sclerosis: An updated meta-analysis

BACKGROUND

There is considerable controversy around the question as to whether Helicobacter pylori (H. pylori) infection has a protective or causative role in the development of multiple sclerosis (MS). This study evaluated published information to assess the association between H. pylori infection and MS.

METHODS

We conducted a comprehensive systematic review of relevant observational studies in international databases. A random-effects model was used to calculate pooled odds ratio (OR) and 95% confidence interval (CI). I² statistic was used to assess the between-study heterogeneity. Subgroup and meta-regression analyses were applied to identify the source of heterogeneity.

RESULTS

In total, 22 studies (25 datasets) were eligible for the meta-analysis: 17 datasets had prevalence data and eight datasets had data on the mean titer of anti-H. pylori IgG. The pooled prevalence of H. pylori was 44.1% (908/2606) in the MS patients and 46.1% (1016/2200) in the controls, indicating a non-significant protective effect of H. pylori on MS (OR, 0.82; 95%CI, 0.58-1.17). In the subgroup analysis, studies that used ELISA yielded a significant protective association (OR, 0.59; 95%CI, 0.46-0.77), while a positive non-significant association (OR, 1.33; 95%CI, 0.83-2.15) was found from studies that used other serological methods; interestingly, a significant positive association (OR, 6.64; 95%CI, 2.40-13.76) was found from studies that used histological methods to detect H. pylori infection.

CONCLUSIONS

Our findings do not support the hypothesis that H. pylori infection represents a protective factor against the development of MS; however, the results varied depending on the diagnostic method(s). Particularly, a significant positive association was identified when studies introduced results based on histological examination, suggesting that active H. pylori infection might be a risk factor for development of MS. Thus, further studies are needed utilizing accurate diagnostic methods to elucidate the association between active H. pylori infection and MS.