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

Diagnostic tests for toxoplasmosis are based on serological techniques due to their high sensitivity. Some IgG subclasses are related to clinical outcome in the congenital form. In this work, we determined the levels of IgG, IgA, IgG1, IgG2, IgG3 and IgG4 anti-Toxoplasma gondii antibodies in paired saliva and serum samples from 91 women by indirect ELISA using a crude extract of the RH strain. The levels of IgA, IgG2, IgG3 and IgG4 antibodies and, to a lesser extent, IgG1 did not correlate between saliva and serum, that is, most cases that were positive for one Ig class in a sample were negative or very low in the other, and vice versa. We also observed that most samples of saliva that were positive for one IgG subclass were also positive for at least 2 of the other 3; this contrasted with findings in serum, wherein each person was positive almost exclusively for one subclass, as demonstrated before by us and other researchers. Although these findings are disappointing for the use in diagnosis, the richer response in saliva might indicate local exposure to T. gondii antigens without systemic infection; thus, saliva might be reflecting a local (protective?) response against this protozoan.

Congenital toxoplasmosis: candidate host immune genes relevant for vertical transmission and pathogenesis.

Toxoplasma gondii infects a variety of vertebrate hosts, including humans. Transplacental passage of the parasite leads to congenital toxoplasmosis. A primary infection during the first weeks of gestation causes vertical transmission at low rate, although it causes major damage to the embryo. Transmission frequency increases to near 80% by the end of pregnancy, but the proportion of ill newborns is low. For transmission and pathogenesis, the parasite genetics is certainly important. Several host innate and adaptative immune response genes are induced during infection in adults, which control the rapidly replicating tachyzoite. The T helper 1 (Th1) response is protective, although it has to be modulated to avoid inflammatory damage. Paradoxical observations on this response pattern in congenital toxoplasmosis have been reported, as it may be protective or deleterious, inducing sterile abortion or favoring parasite transplacental passage. Regarding pregnancy, an early Th1 microenvironment is important for control of infectious diseases and successful implantation, although it has to be regulated to support trophoblast survival. Polymorphism of genes involved in these parallel phenomena, such as Toll-like receptors (TLRs), adhesins, cytokines, chemokines or their receptors, immunoglobulins or Fc receptors (FcRs), might be important in susceptibility for T. gondii vertical transmission, abortion or fetal pathology. In this study some examples are presented and discussed.

Toxoplasmosis in pregnancy: determination of IgM, IgG and avidity in filter paper-embedded blood.

OBJECTIVE: To detect immunoglobulin M (IgM) anti-Toxoplasma gondii antibodies and determine immunoglobulin G (IgG) titer and avidity in filter paper-embedded blood (FPEB) samples of pregnant women. STUDY DESIGN: A total of 100 FPEB samples of pregnant women (30 positive and 70 negative) were analyzed for anti-T. gondii-specific IgM antibodies. Eleven and nine pairs of serum and FPEB samples were used to standardize IgG titration and avidity, respectively. Then, the correlation of avidity results was determined with 23 serum/FPEB pairs from IgG-positive cases. RESULT: IgM detection in FPEB was 92% sensitive and 100% specific. The titration of IgG antibodies in FPEB correlated with that of serum (r >or=0.9). Significant difference in avidity between the acute and the undetermined/chronic cases was observed in both samples. As expected, no correlation was found between IgM levels and avidity. CONCLUSION: The FPEB is useful to infer infection phase, and thus to speed clinical decisions in congenital toxoplasmosis management.

Congenital and acquired toxoplasmosis: diversity and role of antibodies in different compartments of the host.

The apicomplexan parasite Toxoplasma gondii is remarkable in several aspects, since it is a protozoan that infects most nucleated cells in many warm-blooded animals, worldwide. Although the cellular immune response against T. gondii is critical for infection control, antibodies may either enhance or block protective mechanisms, and even mediate immunological damage, directly or indirectly. Since cytokines regulate the class/subclass switch, antibodies may also be the biomarkers of protective or pathological cellular immune events. There is a scientific and clinical interest in the presence of natural and autoreactive antibodies, as well as in the 'chronic' immunoglobulin M (IgM) response and the post-treatment 'rebound'. Another interesting aspect is compartmentalization; certain immunoglobulins may uniquely be found in specific host fluids. Local synthesis has been demonstrated, but antibodies may also traverse several cell layers, like the blood-brain and haemato-ocular barriers, and the placenta. In some instances, Fc receptors (FcRs) facilitate transport and may even have a concentrator effect, which can be related to resistance or pathology. These aspects of the humoral response against T. gondii are reviewed in the present paper.