A peptide originated from Toxoplasma gondii microneme 8 displaying serological evidence to differentiate recent from chronic human infection

IgM Antibody Detection as a Diagnostic Marker for Acute Toxoplasmosis: Current Status of Studies and Main Limitations

Accurate dating of Toxoplasma gondii infection is essential for effective clinical management, particularly in pregnant women and immunocompromised individuals, where distinguishing acute from chronic infection informs treatment decisions. Serological detection of IgM antibodies is a key tool in diagnosing recent toxoplasmosis; however, its reliability is compromised by persistent IgM responses, cross-reactivity, and assay variability. While IgM lacks sufficient specificity to serve as a standalone marker of acute infection, it remains an important component of serological panels. This review summarizes current IgM detection methods and explores advancements aimed at improving diagnostic accuracy with a focus on recombinant antigens, which have emerged as promising alternatives to traditional Toxoplasma lysate antigen-based immunoassays. This paper also explores alternative methods of differentiating chronic and acute toxoplasmosis and outlines key areas for future research.

A Structural In Silico Analysis of Novel Epitopes from Toxoplasma gondii Proteins for the Serodiagnosis of Toxoplasmosis

Toxoplasmosis is a widely spread zoonosis worldwide, considered one of the most important parasitic infections that affect global public health, and usually, it is not correctly diagnosed. Serological tests for the diagnosis of Toxoplasma gondii infection have limitations in differentiating acute from chronic infection, which is important to determine the appropriate clinical management and treatment, mainly in pregnant women and immunocompromised individuals infected by this parasite. The present study aimed to characterize immunogenic epitopes from T. gondii immunodominant antigens, as SAG1(SRS29B), SAG2A (SRS34A), GRA1, GRA2, GRA3, GRA5, GRA6, GRA7, MAG1, BSR4, and CCp5A, by investigating if these parasite components might emerge as alternatives to improve the diagnosis of toxoplasmosis. A detailed comparative in silico analysis was used for this purpose. Once the protein sequences were retrieved from the ToxoDB database, different parameters were calculated, including physicochemical characteristics, accessibility values, and antigenicity. Multiple sequence alignment, 3D structures modeling, and the validation of 3D structures were also performed among all 11 peptides. Considering the results from the combination of all parameters analyzed, it can be hypothesized that the linear epitopes from SAG1, GRA3, and BSR4 proteins were found to be stable and hydrophilic, with a significant antigenicity score, and accessibility on the protein surface. Also, these three selected peptides were able to detect anti-T. gondii antibodies in serum samples from pigs infected by tachyzoites, when compared with control serum samples, obtained from the same naïve animals and tested by ELISA, demonstrating remarkable difference in terms of reactivity. Taken together, as our study addresses a critical challenge in the serodiagnosis of toxoplasmosis, particularly in gestational and congenital infections, where false-positive and false-negative results often arise from the use of native or recombinant antigens of T. gondii, our findings highlight the potential of synthetic peptides derived from novel epitopes of this parasite as alternative tools for the development of more accurate immunodiagnostic assays for toxoplasmosis.

The quality and characteristics of bovine sperm are compromised by Toxoplasma gondii antigens, impacting in in vitro bull fertility

Studies in various species have demonstrated different results on the effects of T. gondii infection on sperm quality. It has also been demonstrated that in some stages of the disease, there is elimination of cellular debris or even the intact parasite in the semen. The present work aimed to evaluate the in vitro effects of the presence of soluble T. gondii antigens in bovine semen on sperm integrity. The spermatozoa were treated with T. gondii antigens in double serial dilutions classified as high, medium and low doses (8, 4, 2 µg/ml) in "TALP-Sperm" and "TALP-Fert" media. The results showed that T. gondii antigens affect sperm motility and mitochondrial activity, and cause changes in sperm chromatin integrity, as well as damage to the sperm membrane and acrosome. Finally, spermatozoa treated with T. gondii antigens were evaluated in the in vitro production of embryos (IVEP). The use of semen contaminated with antigens in IVEP routines did not lead to a decrease in the fertilization of oocytes, as sperm undergo selection before in vitro fertilization, which eliminates the most altered sperm. However, early embryonic development was affected, probably by structural changes that were not eliminated in the selection process. The results demonstrated that the presence of soluble T. gondii antigens in bovine semen alters sperm integrity and vital characteristics for the fertilization process and embryonic development and therefore causes fertility problems in males.