Human toxoplasmosis: a comparative evaluation of the diagnostic potential of recombinant Toxoplasma gondii ROP5 and ROP18 antigens

Abstract

Toxoplasmosis is one of the most common parasitic diseases worldwide and it poses a serious challenge regarding prevention, diagnosis and therapy. The commonly used diagnostic methods are mostly based on the detection of specific antibodies in sera. Since they are not always accurate enough and do not allow precise definition of the phase of the Toxoplasma gondii infection, there is an urgent need to find specific molecular markers of acute or chronic infection stages. This study provides a comparative assessment of recombinant ROP5 and ROP18 T. gondii proteins in the serodiagnosis of human toxoplasmosis. We found that both ROP5 and ROP18 proteins allowed the detection of specific IgM and IgG antibodies with a relatively low sensitivity; however, ROP18 IgM ELISA proved to be more sensitive than the SAG1 assay. This study also points to a relatively weak potential of the corresponding native ROP5 and ROP18 kinases in the generation of a strong antibody response in humans.

Serological and molecular rapid diagnostic tests for Toxoplasma infection in humans and animals

“…In the past two decades, several Toxoplasma recombinant antigens have been cloned and expressed in E. coli or yeast for use as diagnostic reagents for human and animal infections. They include antigens from the parasite surface (SAGs), matrix (MAGs), dense granule (GRAs), rhoptry (ROPs), and microneme (MICs) [43][44][45][46][47][48][49][50]. Four of the recombinant antigens (SAG1, SAG2, GRA3, and GRA6) expressed in E. coli have been used in an RDT to detect infection in cats.…”

Enzyme-Linked Aptamer Assay (ELAA) for Detection of Toxoplasma ROP18 Protein in Human Serum

“…The ROP18 protein has been described as one of the major virulence factors of T. gondii , involved in the regulation of the host innate immune response, promoting the survival and replication of the parasite (Saeij et al, 2006; Taylor et al, 2006). IgM and IgG antibodies have been identified against the ROP18 (Gatkowska et al, 2015) or against peptides derived from it (Sánchez et al, 2014), which indicates that the immune system recognizes the protein. However, until now, the presence of the protein in serum from individuals with toxoplasmosis has not been reported and it is unknown if its presence could be related to the clinical manifestation of the disease.…”

“…Previous studies indicate that ROP18 is secreted by the rhoptry organelles inside the host cell during the process of parasite invasion and later it is located in the membrane of the parasitophorous vacuole (Saeij et al, 2006; Hunter and Sibley, 2012). However, it is possible to suggest that the parasite secretes a certain amount of the ROP18 protein before entering to the host cell and it also could explain the presence of IgM and IgG antibodies in mouse and human serum that recognize specifically the ROP18 protein (Gatkowska et al, 2015; Grzybowski et al, 2015). Additionally, it could be assumed that the ROP18 protein is secreted once the parasite has been established within the host cell.…”

“…Furthermore, there is a report that demonstrates the presence of virulent alleles that code for ROP18 in humans with ocular toxoplasmosis in Colombia, who presents a more severe inflammatory reaction in the eye (Sánchez et al, 2014). Currently, there is only one study that indicates the presence of specific IgM and IgG antibodies against ROP18 in sera from humans with toxoplasmosis (Gatkowska et al, 2015). However, there are not any reported methods that allow the direct detection of this protein in human serum.…”

Toxoplasma gondii: Deeper understanding of epidemiology, virulence and pathophysiology enhances diagnosis and informs vaccine design

“…Shared by all apicomplexan invasive stages, ROPs are essential to parasite propagation (Dubremetz, 2007). ROP5 and ROP18 proteins of T. gondii are specific for anti-IgM and anti-IgG to diagnose human toxoplasmosis (Grzybowski et al, 2015). Amplification by PCR of specific nucleic acid sequences from body fluid and tissue samples has been used successfully to diagnose congenital (Bessières et al, 2009), ocular (Gomez et al, 2019), cerebral and disseminated toxoplasmosis (Rasti et al, 2012).…”