Analysis of IgG subclasses (IgG1 and IgG3) to recombinant SAG2A protein from Toxoplasma gondii in sequential serum samples from patients with toxoplasmosis

Abstract

The kinetics of the humoral immune response was evaluated using the recombinant SAG2A protein comparatively to soluble Toxoplasma antigen (STAg) by ELISA in sequential serum samples of patients with toxoplasmosis up to 12 months of illness onset. The follow up of IgM and IgA levels to STAg showed a gradual decrease, with the majority of patients (88%) seropositive for IgM up to 12 months of infection, whereas IgA seropositivity was relatively low (78%) compared to IgM (100%) in the first 3 months of infection. The follow up of IgG and IgG1 antibodies showed a similar increasing profile for both SAG2A and STAg, with slightly higher seropositivity for STAg. The kinetics of IgG3 to STAg was similar to that of IgG1, contrasting with the kinetics of IgG3 to SAG2A that showed high levels up to 6 months of infection, with continuous decreasing over the time. Higher IgG3 seropositivity to SAG2A than STAg was also observed in the initial phases of infection. A higher IgG3/IgG1 ratio for SAG2A than STAg was detected in the first 3 months of infection, with decreasing profile over the time. The associations of IgG3/IgG1 ratio>1.0 with positive IgM or IgA antibodies were predominantly found in the first 3 months of infection, whereas associations of IgG3/IgG1 ratio<1.0 with positive IgM or negative IgA antibodies were mostly observed from 3 to 12 months of infection. In conclusion, our results demonstrate a differential kinetics of IgG3 antibodies to SAG2A and STAg in patients with toxoplasmosis up to 12 months of infection. Also, the IgG3/IgG1 ratio to SAG2A in association with classical serological markers of acute phase could be potential tools to distinguish early acute from convalescent phases of Toxoplasma gondii infection.

SAG2A protein from Toxoplasma gondii interacts with both innate and adaptive immune compartments of infected hosts

“…Our present work locates a previously predicted B cell linear epitope [18] within this predicted IUP domain of SAG2A, which corroborates with our previous studies on immunodominance of the protein and its potential as an acute phase marker for the diagnosis of human toxoplasmosis [32,33,54]. In addition, we show here that recombinant SAG2A was able to specifically detect T. gondii -induced antibodies in experimental and natural infections eliminating potential serological cross-reactivity with closely related N. caninum , a long-lived setback within the veterinary field [55-57].…”

“…ELISA and Western blotting protocols using recombinant SAG2A (rSAG2A) were performed for the detection of IgG antibodies present in serum samples of experimentally infected mice and naturally infected goats to T. gondii and N. caninum , as previously described [32,33]. Antibody titers were expressed as ELISA index (EI), according to the following formula: EI = OD sample/OD cut off, as described elsewhere [34].…”

What do anti‐Toxoplasma gondii IgA and IgG subclasses in human saliva indicate?

“…antibodies, IgA, IgG subclasses, saliva, Toxoplasma gondii Some years ago, specific abs of several IgG subclasses were studied using serum samples from patients with acquired infections. [17][18][19] The main finding was that IgG1 abs were predominant and longlasting. More recently, we and other groups have found that specific serum IgG subclasses are useful to confirm congenital infection and may be associated with clinical problems in the newborns.…”

Seroepidemiology ofToxoplasmain a coastal region of Haiti: multiplex bead assay detection of immunoglobulin G antibodies that recognize the SAG2A antigen

“…IgG ELISAs using recombinant SAG2A were recently shown to be sensitive (95%) and specific (100%) compared to the crude Toxoplasma antigen ELISA (23, 24). In this work, we demonstrate that a bead coupled with recombinant SAG2A protein can be incorporated into our neglected tropical disease (NTD) MBA panel and used to determine Toxoplasma seroprevalence.…”