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. 2022 Jan 31;22(1):110.
doi: 10.1186/s12879-022-07088-w.

Development of a new serotyping ELISA for Toxoplasma gondii type II, type III and Africa 1 lineages using in silico peptide discovery methods, well categorized feline and human outbreak serum samples

Hüseyin Can  1   2 , Ayşegül Aksoy Gökmen  3 , Mert Döşkaya  4   5 , Sedef Erkunt Alak  6 , Aysu Değirmenci Döşkaya  4   5 , Muhammet Karakavuk  4   7 , Ahmet Efe Köseoğlu  6 , Tuğba Karakavuk  8 , Ceren Gül  8 , Mervenur Güvendi  6 , Aytül Gül  9 , Adnan Yüksel Gürüz  4   5 , Selçuk Kaya  3 , Aurélien Mercier  10   11 , Cemal Ün  6   4
Affiliations

Development of a new serotyping ELISA for Toxoplasma gondii type II, type III and Africa 1 lineages using in silico peptide discovery methods, well categorized feline and human outbreak serum samples

Hüseyin Can et al. BMC Infect Dis. .

Abstract

Background: Discovery of new Toxoplasma gondii serotyping epitopes is important due to reports showing the influence of genotype on the severity of toxoplasmosis. In Turkey, genotypes belonging to type II, type III and Africa 1 lineages were mainly detected. The present study focused on to find out epitopes with high discriminative capacity to serotype these genotypes using well characterized strains isolated from Turkey.

Methods: To meet this objective, GRA6 and GRA7 genes were sequenced from strains belonging to the type II, III and Africa 1 lineages, and B cell epitopes inside these sequences were predicted by Bcepred and additional docking analysis was performed with B cell receptor. Based on these analyses, 22 peptides harboring lineage specific epitopes were synthesized. Then, the serotyping potency of these peptides was tested using peptide ELISA and well categorized serum samples collected from stray cats infected with genotypes of the different lineages type II (n:9), III (n:1) and Africa 1 (n:1). As a result of peptide-ELISA, a serotyping schema was constructed with peptides that show high discriminative capacity and this assay was validated by sera collected from humans after an outbreak (n:30) and mother/newborn pair sera (n:3). Later, the validated serotyping schema was used to serotype a larger group of human (n:38) and cat (n:24) sera.

Results: Among 22 peptides, GRA6II/c, GRA7III/d, and GRA6 Africa 1/b epitopes have shown discriminative capacity. During the validation of peptide-ELISA, the serotype of toxoplasmosis outbreak and mother/newborn cases were detected to be serotype II. Moreover, the analyses in a larger group showed that serotype II was prevalent in humans and stray cats.

Conclusions: Overall, the results showed that the serotyping schema could be successfully used to serotype T. gondii infections caused by type II, III and Africa 1 genotype.

Keywords: GRA6; GRA7; Genotyping; Peptide ELISA; Serotyping; Toxoplasmosis.

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Conflict of interest statement

The authors declare that they have no competing interests.

Figures

Fig. 1
Fig. 1
Docking results of epitopes derived from GRA 6 protein with variable region of heavy chain of B cell receptor. Blue color represents heavy chain; Red color represents light chain; Yellow color represents epitope. Yellow arrow shows epitope that was not correctly dock to variable region of heavy chain of B cell receptor
Fig. 2
Fig. 2
Docking results of epitopes derived from GRA 7 protein with variable region of heavy chain of B cell receptor. Blue color represents heavy chain; Red color represents light chain; Yellow color represents epitope. Yellow arrow shows epitope that was not correctly docked to variable region of heavy chain of B cell receptor
Fig. 3
Fig. 3
Peptide-ELISA results showing the serotyping capacity. Cut off value was calculated by ROC analysis using negative cat serum samples (n:9). The significant results obtained from each epitope are shown by star. Horizontal dotted lines show cut off values
Fig. 4
Fig. 4
Simple illustration of serotyping schema
See this image and copyright information in PMC

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