Anti-Toxoplasma gondii Antibodies in European Residents: A Systematic Review and Meta-Analysis of Studies Published between 2000 and 2020

Toxoplasmosis has a major impact on animal and public health. Information regarding the seroprevalence of human Toxoplasma gondii infections from a European perspective has not yet been compiled to date. Thus, the present review summarized available resident data from the period 2000-2020. The overall seroprevalence of anti-T. gondii IgG was 32.1%, with great variability between countries (n = 30). The subgroup analysis identified different pooled prevalence data depending on the geographic area (p < 0.0001), target population (p = 0.0147), and serological diagnosis assays used (p = 0.0059). A high heterogeneity (I2 = 100%, p < 0.001; Q = 3.5e+05, d.f. = 135, p < 0.001) and degree of publication bias (Egger's test = 6.14, p < 0.001) were observed among the 134 studies considered. The occurrence of anti-T. gondii IgM, which was reported in 64.7% of studies, reached a pooled seroprevalence of 0.6%. In addition, among the eight main risk factors identified, "contact with soil", "consumption of undercooked beef", and "intake of unwashed vegetables" were the most significantly associated with infections. The fact that one-third of the European population has been exposed to T. gondii justifies extra efforts to harmonize surveillance systems and develop additional risk-factor analyses based on detailed source attribution assessment.

Toxoplasma gondii protects from IgE sensitization and induces Th1/Th2 immune profile

Toxoplasma gondii (T gondii) infection has been associated with protection against allergy and autoimmune diseases. We investigated the effects of T gondii infection on cytokine and antibody responses in atopic and nonatopic Brazilian subjects. We have measured in whole-blood cultures, Th1 (IFN-γ and IL-12), Th2 (IL-5) and regulatory cytokine IL-10 in blood cells unstimulated and stimulated with pokeweed mitogen or T gondii soluble tachyzoites antigen (STAg) or Dermatophagoides pteronyssinus antigen. A significant negative association was found between high levels of anti-dust mite IgE and T gondii seropositivity (OR = 0.46; 95%CI = 0.25-0.85). STAg stimulation induced a mixed profile of Th1 and Th2 cytokines (IFN-γ, IL-12 and IL-5) in Tg-positive atopic individuals compared with Tg-negative atopic individuals (P < .0001, P = .033 and P = .003, respectively). In contrast, IL-10 production was not different between these groups. No association was found between T gondii infection and asthma. We hypothesized that the protective effect on atopy might be related to the strong Th1 immune response to T gondii found on the seropositive subjects. From our knowledge, this is the first study to investigate the association between atopy and T gondii infection in Brazilian subjects, analysing the cellular immune responses.

Regulatory cells induced by acute toxoplasmosis prevent the development of allergic lung inflammation

The increased prevalence of allergies in developed countries has been attributed to a reduction of some infections. Supporting epidemiological studies, we previously showed that both acute and chronic Toxoplasma gondii infection can diminish allergic airway inflammation in BALB/c mice. The mechanisms involved when sensitization occurs during acute phase would be related to the strong Th1 response induced by the parasite. Here, we further investigated the mechanisms involved in T. gondii allergy protection in mice sensitized during acute T. gondii infection. Adoptive transference assays and ex vivo co-cultures experiments showed that not only thoracic lymph node cells from infected and sensitized mice but also from non-sensitized infected animals diminished both allergic lung inflammation and the proliferation of effector T cells from allergic mice. This ability was found to be contact-independent and correlated with high levels of CD4(+)FoxP3(+) cells. IL-10 would not be involved in allergy suppression since IL-10-deficient mice behaved similar to wild type mice. Our results extend earlier work and show that, in addition to immune deviation, acute T. gondii infection can suppress allergic airway inflammation through immune suppression.

Positive associations between infections of Toxoplasma gondii and seropositivity with Anisakis simplex in human patients suffering from chronic urticaria

Toxoplasma gondii is a food-borne and orofecal microorganism which produces chronic infection, and attempts have been made to prove its negative association with atopy in the context of the hygiene hypothesis. Anisakis simplex is a fish parasite associated with chronic urticaria (CU) in endemic regions. We analysed the relationship between both infectious agents in CU. We included 42 patients with chronic urticaria (18 patients with CU associated with A. simplex sensitization and 24 not sensitized CU patients). Patients were assessed for atopy by a skin prick test (SPT) against common aeroallergens and for respiratory symptoms. Anisakis simplex sensitization was assessed by SPT and specific IgE by CAP fluoro-enzyme immunoassay (CAP-FEIA). Anti-T. gondii IgG levels were measured by enzyme-linked immunosorbent assay (ELISA). CU patients were analysed with respect to T. gondii seropositivity, A. simplex sensitization, atopy and immigrant status. The seroprevalence of T. gondii was 40.5% in CU patients and 42.1% in the control group. Immigrants were more frequently infected by T. gondii (41.2% versus 12%; P =0.036). Anti-T. gondii IgG antibodies were associated with past A. simplex parasitism (odds ratio 6.73; P =0.03) and independently with atopic sensitization (odds ratio 5.85; P =0.04). In CU patients, T. gondii has no protective effect on atopic sensitization or A. simplex sensitization.

The association between foodborne and orofecal pathogens and allergic sensitisation -- EuroPrevall study

BACKGROUND

An inverse association between markers of exposure to foodborne and orofecal pathogens and allergic sensitization has been reported. However, the findings of epidemiological studies have not been consistent. This study investigated the relationship between antibodies to hepatitis A, Toxoplasma gondii and salmonella and allergic sensitization to food and aeroallergens in children from different geographical areas.

METHODS

Specific IgE and/or skin prick testing against food and aeroallergens were measured in children from 6 to 12 years of age residing in Greece, the Netherlands, China, India and Russia. Seropositivity to the three pathogens was measured, and data on potential confounders were collected using questionnaire.

RESULTS

Data from 800 children (126 from Athens; 248 from Utrecht; 110 from Hong Kong; 119 from urban Tomsk; and 197 from rural Tomsk) could be analysed. The highest percentage of positive serology to salmonella was found in Hong Kong (46.4%), to T. gondii in urban Tomsk (13.4%) and to hepatitis A in Athens (71.2%). Although not significant, T. gondii seropositivity tends to be negatively associated, and hepatitis A seropositivity tends to be positively associated with allergic sensitization.

CONCLUSION

Inconsistent associations were observed between allergic sensitization to food and aeroallergens and markers of exposure to two common foodborne pathogens. The association with T. gondii tends to be negative, consistent with the 'hygiene hypothesis', but the association with hepatitis A tends to be positive. Taken together, there is no clear evidence that past exposure to foodborne and orofecal pathogens protects against allergic sensitization to food or aeroallergens.

Phadiatop Seropositivity in Schizophrenia Patients and Controls: A Preliminary Study

There is a dearth of information on the association of atopy with schizophrenia. The few available studies used population-based registers to classify the atopy status of the patients but this strategy is not reliable. This study measured seropositivity with a multiallergen screen of allergen specific IgE antibodies in schizophrenia patients versus healthy controls. A subset of 66 schizophrenia patients and 34 healthy controls were randomly selected from a large comparative study of schizophrenia patients and controls. The Phadiatop multi-allergen screen was performed on sera from all the participants to assess their atopic status. Logistic regression was used to calculate the odds ratio for the association of schizophrenia with Phadiatop seropositivity as a measure of atopy. The prevalence of Phadiatop seropositivity was significantly lower (χ² 4.59, p = 0.032) and there was a reduced odds ratio for atopy in schizophrenia patients relative to controls (OR 0.40; 95% CI 0.17 to 0.94, p = 0.036). Though limited by a relatively small sample size and potentially confounded by anti-psychotic medications, this study suggests that the prevalence of atopy is lower in patients with schizophrenia. Replicating these results in larger samples could add to our growing understanding of immunological implications in mental illness.

Antibody and cytokine responses to house dust mite allergens and Toxoplasma gondii antigens in atopic and non-atopic Brazilian subjects

According to hygiene hypothesis, a lower exposure to infection is associated with increased prevalence of allergic diseases. This study aimed to investigate the association between atopy and Toxoplasma gondii (Tg) infection by analyzing the antibody and cytokine responses to house dust mite allergens and T. gondii antigens in Brazilian subjects. A total of 275 individuals were assessed and divided into atopics (n=129) and non-atopics (n=146) based on markers of allergy (positive skin prick test and ELISA-IgE to mite allergens) or Tg-seropositive (n=116) and Tg-seronegative (n=159) groups according to infection markers (positive ELISA-IgG to T. gondii). Tg-seropositive individuals presented lower allergenic sensitization (37%) to mite allergens than Tg-seronegative subjects (54%). A significant association was found between atopy and negative serology to T. gondii (OR: 2.0; 95% CI: 1.23-3.26; P<0.05). Proliferative responses and cytokine production after antigenic stimulation showed predominant synthesis of Th1-cytokines as IFN-gamma in Tg-seropositive patients, whether atopics or non-atopics. Conversely, Th2-cytokines as IL-5 prevailed in atopics compared to non-atopics, regardless the seropositivity to T. gondii. Levels of IL-10, IL-13, IL-17, and TGF-beta were not able to discriminate the groups. Hence, a negative association between atopy and infection by T. gondii was demonstrated for the first time in Brazilian subjects, focusing on the antibody and cytokine responses and indicating that the immunomodulation induced by the parasite may play a protective role in the development of allergic diseases.