The standardization of 5 immunoassays for anti-Toxoplasma immunoglobulin G(IgG)

Seroprevalence and age-related susceptibility of TORCH infections in childbearing age women: A 5-year cross-sectional retrospective study and a literature review

BACKGROUND

Serodiagnosis of TORCH infections should be performed in pre-pregnancy and reproductive-age women to prevent vertical transmission. Herein, we conducted a 5-year cross-sectional retrospective study in childbearing age women to provide prevalence data. Also, stratifying the cohort into three age groups, we identified those most susceptible to acute TORCH infections.

METHODS

Between 2019 and 2023, serum samples from 2286 childbearing age women attending the "R. Dulbecco" University Hospital of Catanzaro were collected. Screening for TORCH pathogens, such as: Toxoplasma gondii (TOX), Cytomegalovirus (CMV), Rubella Virus (RUB), Parvovirus B19 (ParvoB19), Herpes Simplex Virus types 1 and 2 (HSV1, HSV2) and Treponema pallidum was carried out using serological tests. Chemiluminescent immunoassay was performed to detect TOX, CMV and ParvoB19 Immunoglobulin M (IgM) and Immunoglobulin G (IgG) antibodies, while Enzyme Linked Fluorescent Assay was performed to detect RUB IgM and IgG antibodies and CMV and TOX IgG Avidity. Enzyme Linked Immunosorbent Assay was performed to detect HSV1 IgG, HSV2 IgG, HSV1/2 IgM, T. pallidum total antibodies and RUB IgG Avidity. Binomial logistic regression models were developed to compare seroprevalence rates among different age groups.

RESULTS

The highest immunological protection was observed for RUB infection (87 %), probably associated with vaccination practice, followed by HSV1 and CMV (82 % and 63 %). The 16-25 year age group results as the most susceptible to acute infections as demonstrated by odds of CMV IgM positivity (primary infection) which decreased with age.

CONCLUSIONS

The TORCH serological screening program should be implemented in women before pregnancy to formulate strategies for serological screening of childbearing age women and guiding clinicians in making decisions.

The Potential Contribution of ABO, Lewis and Secretor Histo-Blood Group Carbohydrates in Infection by Toxoplasma gondii

The glycosyltransferases encoded by genes from the human ABO, Lewis, and Secretor histo-blood group systems synthesize part of the carbohydrate antigens in hematopoietic and non-hematopoietic tissues. The combined action of these glycosyltransferases strongly influences cell, tissue, mucosa, and exocrine secretion carbohydrate phenotypes, including those serving as habitat for mutualistic and pathogenic microorganisms. A set of reports investigated associations between Toxoplasma gondii infection and the ABO histo-blood group system, but the results are contradictory. As T. gondii uses the gastrointestinal tract as a route for infection, and in this organ, the expression of ABO, Lewis, and Secretor histo-blood group carbohydrates occurs, it is reasonable to suppose some biological relationship between them. This text reviewed association studies published in recent decades focusing on the potential contribution of the ABO, Lewis, and Secretor histo-blood group carbohydrates and infection by T. gondii.

Anti-Toxoplasma IgG assays: What performances for what purpose? A systematic review

Chronic infection with Toxoplasma gondii is attested by the detection of specific anti-Toxoplasma IgG. A wide panel of serologic methods is currently marketed, and the most suitable method should be chosen according to the laboratory resources and the screened population. This systematic review of evaluation studies aimed at establishing an overview of the performances, i.e. sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of marketed anti-Toxoplasma IgG assays, and discussing their technical characteristics to guide further choice for routine diagnostic use. According to PRISMA guidelines, the search performed in PubMed and Web of Science databases recovered 826 studies, of which 17 were ultimately included. Twenty commercial anti-Toxoplasma IgG assays were evaluated, in comparison with an accepted reference method. Most of them were enzyme-immunoassays (EIAs, n = 12), followed by agglutination tests (n = 4), immunochromatographic tests (n = 3), and a Western-Blot assay (WB, n = 1). The mean sensitivity of IgG assays ranged from 89.7% to 100% for standard titers and from 13.4% to 99.2% for low IgG titers. A few studies pointed out the ability of some methods, especially WB to detect IgG early after primary infection. The specificity of IgG assays was generally high, ranging from 91.3% to 100%; and higher than 99% for most EIA assays. The PPV was not a discriminant indicator among methods, whereas significant disparities (87.5%-100%) were reported among NPVs, a key-parameter assessing the ability to definitively rule out a Toxoplasma infection in patients at-risk for opportunistic infections.