Use of IgG in Oral Fluid To Monitor Infants with Suspected Congenital Toxoplasmosis

Abstract

Infants born to mothers who seroconverted for toxoplasmosis during pregnancy are at risk of sequelae. In the case of a negative work-up at birth, congenital infection can be ruled out only by monitoring the disappearance of maternal immunoglobulin G (IgG) transmitted through the placenta, which can be achieved by regular blood sampling during the first year. To alleviate the discomfort of this follow-up, we developed an indirect enzyme-linked immunosorbent assay to detect specific IgG diffusing passively from the blood through the gingival epithelium by collecting oral fluid on microsponges. To assess the feasibility of the test, 212 patients were first enrolled. Levels of specific IgG in oral fluid were significantly higher in seropositive (n ‫؍‬ 195) than in seronegative (n ‫؍‬ 17) patients (mean optical densities, 1.145 ؎ 0.99 versus 0.092 ؎ 0.127; P < 0.0001). In a population of 93 patients <15 months of age born to mothers who displayed toxoplasmic infection during pregnancy, 70 were free of congenital infection and were followed up until their serology turned negative, and 23 were congenitally infected. The same patterns of IgG were observed in the oral fluid and sera in each group. Using a cutoff of 0.04 (optical density value), the sensitivity and specificity of the test were 67.9% and 80.3%, respectively, and the probability of not having a congenital infection when the test on oral fluid was negative was 99%. Although the performance of the test needs to be improved, oral fluid sampling appears to be a promising tool for monitoring infants with suspected congenital toxoplasmosis.

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

“…Previous reports have shown that anti‐ T. gondii IgG, IgM and IgA abs are present in saliva. In some studies, the salivary IgA and IgG levels reflect those in serum, but they show low sensitivity and specificity values, as in the present study . To our knowledge, searches of anti‐ T. gondii IgG subclasses have not been performed in saliva.…”

“…In some studies, the salivary IgA and IgG levels reflect those in serum, but they show low sensitivity and specificity values, as in the present study. [10][11][12][13][14][15][16] To our knowledge, searches of anti-T. gondii IgG subclasses have not been performed in saliva. We hoped they could help diagnose or suggest prognosis, but we found a rather different panorama, as they performed badly, mainly because most positive cases for specific IgG2, IgG3 and IgG4 abs in saliva were negative in serum and did not correlate to IgG abs either; thus, they exhibited very low diagnostic parameters.…”

“…Different methods have been adapted for the detection of toxoplasmosis infection phase, for confirmation of congenital infection and even to monitor the effectiveness of treatment . As saliva samples are more accessible and their collection is less invasive than serum, several studies have focused on the detection of IgG, IgM or IgA abs in this oral fluid, those being the IgG abs with a better diagnostic performance …”

Laboratory Diagnosis of Congenital Toxoplasmosis

“…The interferon gamma released after T-cell stimulation by T. gondii antigens has be proven to be useful for the diagnosis of congenital toxoplasmosis, but it is currently not commercially available ( 27 ). Detection and follow-up of Toxoplasma IgG in oral fluid have also been used to monitor infants with suspected congenital toxoplasmosis, and it is a promising diagnostic tool ( 28 ). In addition, brain imaging studies and retinal exams can also exhibit findings that are highly suggestive of the disease, and in the absence of alternative etiologies and proper clinical context, they can be diagnostic ( Table 1 ).…”

“…The use of platforms with multiplex capacities can address cost, with the additional benefit that they may be extended to other infections. In addition, the feasibility of testing for antibodies in body compartments beyond serum, such as whole blood and saliva, can address cost and patient convenience ( 28 ). Lastly, public health authorities and national policies should address the need to fund and protect reference centers of excellence for the diagnosis and management of congenital infections since these infections may not be seen commonly in individual practices or medical centers but are a source of major morbidity and mortality to the fetus and to newborns.…”