Diagnostic Value of a Rec-ELISA Using Toxoplasma gondii Recombinant SporoSAG, BAG1, and GRA1 Proteins in Murine Models Infected Orally with Tissue Cysts and Oocysts

Abstract

Toxoplasma gondii causes congenital toxoplasmosis in newborns resulting with fetal anomalies. Determining the initiation time of infection is very important for pregnant women and current serological assays have drawbacks in distinguishing the recently acute toxoplasmosis. Diagnosis of recently acute infection may be improved by using stage specific antigens in serological assays. In the present study, the diagnostic value of sporozoite specific SporoSAG, bradyzoite specific BAG1 proteins and GRA1 protein expressed by all forms of the parasite have been evaluated ELISA using sera systematically collected from mice administered orally with tissue cyst and oocysts. The anti-SporoSAG IgM antibodies in sera obtained from mice infected with oocysts peaked significantly at days 1, 10, and 15 (P<0.01). The anti-BAG1 IgM antibodies in sera obtained from mice infected with tissue cysts peaked significantly at days 15, 40, and 120 (P<0.05). The anti-GRA1 IgM antibodies in sera obtained from mice infected with oocysts peaked significantly at days 2, 10, and 40 (P<0.01). The anti-GRA1 IgM antibodies in sera obtained from mice infected with tissue cysts peaked significantly only at day 40 (P<0.05). The anti-SporoSAG, anti-BAG1, and anti-GRA1 IgG titers of mice showed significant increases at day 40 (P<0.05) and decrement started for only anti-GRA1 IgG at day 120. The presence of anti-SporoSAG IgM and IgG antibodies can be interpreted as recently acute infection between days 10–40 because IgM decreases at day 40. Similarly, presence of anti-BAG1 IgM and absence of IgG can be evaluated as a recently acute infection that occurred 40 days before because IgG peaks at day 40. A peak in anti-GRA1 antibody level at first testing and reduction in consecutive sample can be considered as an infection approximately around day 40 or prior. Overall, recombinant SporoSAG, BAG1 and GRA1 proteins can be accepted as valuable diagnostic markers of recently acute toxoplasmosis.

CCp5A Protein from Toxoplasma gondii as a Serological Marker of Oocyst-driven Infections in Humans and Domestic Animals

“…As noticed for the kinetics of IgG antibodies in pigs infected with oocysts, the kinetics of anti-CCp5A IgM production in mice showed an early peak of reactivity, at day 15 post-infection. In agreement with our results, a previous study assessing the kinetics of mouse IgM antibodies against a recombinant protein from T. gondii sporozoites (SporoSAG), showed a peak of reactivity from 10 to 15 days post-infection in mice infected with oocysts ( Doskaya et al, 2014 ), reinforcing the hypothesis that the use of proteins expressed exclusively by oocysts/sporozoites is critical to identify the early phase of oocyst-driven T. gondii infection.…”

“…The search for specific proteins from T. gondii oocysts/sporozoites has been investigated since the 80s ( Kasper and Ware, 1985 ; Kasper, 1989 ), but only recently oocyst/sporozoite-specific proteins have been characterized with potential use in vaccine design and diagnosis ( Radke et al, 2004 ; Possenti et al, 2010 ; Boyer et al, 2011 ; Hill et al, 2011 ; Doskaya et al, 2014 ). In the present study, it was investigated the serologic application of T. gondii polypeptides specific from oocysts/sporozoites by using reference serum samples from animals (chickens, pigs, and mouse) and humans, in order to determine which parasite stage was involved in the infection.…”

Discovery of new Toxoplasma gondii antigenic proteins using a high throughput protein microarray approach screening sera of murine model infected orally with oocysts and tissue cysts

“…The other problem is that an efficient vaccine that can protect pregnant women against toxoplasmosis does not exist. Current diagnostic antigens that are used to develop diagnostic assays or vaccine candidate antigens are almost always selected randomly and/or based on biological properties such as being a surface protein, having a role in pathogenesis, or high immunogenicity [ 12 , 13 ]. In this new era of advanced technology, methods to select antigens should specifically take advantage of recent advances such as in silico analysis and novel in vitro and in vivo immunoscreens for the generation of new antigens.…”

Expression and characterisation of a Sarcoptes scabiei protein tyrosine kinase as a potential antigen for scabies diagnosis

“…Given that there are no effective tools for harvesting crude allergen proteins, purified recombinant allergens are increasingly being used as serological diagnostic agents 37 . For instance, hydatid disease, coenurosis, nematodes and protozoa can be diagnosed using recombinant allergen-based methods 38 , 39 . Additionally, the total IgG responses to S. scabiei can be observed in severely infested individuals.…”