Serologic rebounds after one-year-long treatment for congenital toxoplasmosis

In vitro activity of the interaction between taxifolin (dihydroquercetin) and pyrimethamine against Toxoplasma gondii

Toxoplasmosis is one of the most neglected zoonotic foodborne parasitic diseases that cause public health and socioeconomic concern worldwide. The current drugs used for the treatment of toxoplasmosis have been identified to have clinical limitations. Hence, new drugs are urgently needed to eradicate T.gondii infections globally. Here, an in vitro anti-Toxoplasma gondii activity of taxifolin (dihydroquercetin) and dihydrofolate inhibitor (pyrimethamine) alone and in combination with a fixed concentration of pyrimethamine were investigated against the rapidly proliferating T.gondii RH strain at 48 hr using colorimetric assay. Pyrimethamine showed the highest anti-T. gondii activity with IC_50P of 0.84 μg/ml (p > .05), respectively. The combination of pyrimethamine with dihydroquercetin gave a significant inhibitory activity against tachyzoites in in vitro with IC_50p of 1.39 μg/ml (p < .05). The IC_50p ranges obtained for the individual and the combination of taxifolin with pyrimethamine inhibition of parasite growth were not cytotoxic to the infected HFF and Hek-293 cell lines used. These compounds combination should be investigated further using in vivo model of toxoplasmosis.

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.

Risk factors for retinochoroiditis during the first 2 years of life in infants with treated congenital toxoplasmosis

BACKGROUND

Retinochoroiditis is the main complication of congenital toxoplasmosis. Its risk factors have rarely been investigated and were the object of this study.

METHODS

A retrospective study was conducted on 300 infants with congenital toxoplasmosis born between July 1, 1996 and December 31, 2002 and treated with pyrimethamine and sulfonamide for at least 12 months. Results of eye tests were collected up to 24 months. Risk factors associated with first retinochoroiditis were identified by univariate then multivariate analyses (Cox model).

RESULTS

One hundred forty-nine boys and 151 girls were included. Maternal infection dated from the first trimester in 34 cases, the second in 97 cases, and the last in 169 cases. At birth, 22 infants had cerebral calcifications. During the first 2 years of life, first retinochoroiditis was diagnosed in 36 infants (12%). In multivariate analysis, 3 factors were significantly associated with first retinochoroiditis before the age of 2 years: a delay of >8 weeks between maternal seroconversion and first treatment [hazard ratio, 2.54; 95% confidence interval (CI), 1.14-5.65], female gender (hazard ratio, 2.02; 95% CI, 1.01-4.1), and cerebral calcifications at birth (hazard ratio, 4.3; 95% CI, 1.9-10). There was no correlation between gestational age at the time of maternal infection and risk for retinochoroiditis.

CONCLUSIONS

A delay of >8 weeks between maternal seroconversion and the beginning of treatment, female gender, and especially cerebral calcifications are risk factors for retinochoroiditis during the first 2 years of life in infants treated for congenital toxoplasmosis.

Nanomolar cationic dendrimeric sulfadiazine as potential antitoxoplasmic agent

The high doses of sulfadiazine (SDZ), used in synergistic combination with pyrimethamine, are mainly responsible for severe side effects and discontinuation of toxoplasmosis treatments. In the search for new strategies that improve the efficacy of treatments with reduced doses of SDZ, we have determined the performance of cationic G4 (DG4) and anionic G4.5 (DG4.5) poly(amidoamine) (PAMAM) dendrimers to act as SDZ nanocarriers. Both dendrimers could efficiently load SDZ (SDZ-DG4 and SDZ-DG4.5) up to a ratio of 30 molecules SDZ per dendrimer molecule. The MTT assay on Vero and J774 cells showed no cytotoxicity for DG4.5 and its SDZ complex incubated between 0.03 and 33 microM of dendrimer concentration. On the other hand, DG4 and its SDZ complex resulted cytotoxic when incubated at dendrimer concentrations higher than 3.3 microM. Finally, complexes and empty dendrimers were in vitro tested against Vero cells infected with RH strain of Toxoplasma gondii along 4h of treatment. For SDZ-DG4.5 and DG4.5 to cause an infection decrease between 25 and 40%, respectively, a dendrimer concentration of 33 microM was required; however, SDZ-DG4 produced the highest infection decrease of 60% at 0.03 microM. These preliminary results, achieved with nanomolar doses of SDZ-DG4 as unique active principle, point to this complex as a suitable potential candidate for antitoxoplasmic therapy.

[Treatment of subclinical congenital toxoplasmosis by sulfadiazine and pyrimethamine continuously during 1 year: apropos of 46 cases]

In France, most of children suffering from congenital toxoplasmosis have an infraclinic or moderate type at birth. This study aimed at evaluating, on the mid term, tolerance and results of postnatal treatment previously given in severe toxoplasmosis.

METHODS

A retrospective study considered 46 children with a mild or moderate congenital toxoplasmosis treated over 12 months with sulfadiazine-pyrimethamine and treatment was completed since three months.

RESULTS

Five children suffered from a lesion of chorioretinitis during treatment and two after. After a mean follow-up of 27.1 months, ten children (21.7% 95%CI [12.1-35.9]) had at least one ocular injury. Specific IgG titers and immune load were diminished to become almost non-existent at the end of the year of treatment (respectively p < 10(-5) and p = 0.0005). No thrombocytopenia was observed. Twenty-three children (50%) had at least one episode of neutropenia < 1000/mm3, 14 had only one, nine presented two or more installment. None was followed by an infection.

CONCLUSION

This therapeutic pathway is more demanding but shorter than those usually offered when associating pyrimethamine-sulfadiazine. Yet, it does give identical result on the mid term. Longer follow-up is needed to appreciate. Active molecule on cysts should be introduced.

Strategy for diagnosis of congenital toxoplasmosis: evaluation of methods comparing mothers and newborns and standard methods for postnatal detection of immunoglobulin G, M, and A antibodies

In a study involving 14 laboratories supported by the European Community Biomed 2 program, we evaluated immunologic methods for the postnatal diagnosis of congenital toxoplasmosis (CT). Among babies born to mothers who seroconverted to positivity for toxoplasmosis during pregnancy, we analyzed 55 babies with CT on the basis of persistent anti-Toxoplasma immunoglobulin G (IgG) at 1 year of life and 50 control babies without anti-Toxoplasma IgG at 1 year of life in the absence of curative treatment with pyrimethamine-sulfonamides. We tested in-house methods such as the enzyme-linked immunofiltration assay (ELIFA) or Immunoblotting (IB) for the detection of IgG or IgM; these methods allowed comparison of the immunologic profiles of the mothers and the infants. We compared ELIFA and IB with a commercial enzyme immunoassay (EIA) or in-house immunosorbent agglutination assay (ISAGA) for the detection of IgM or IgA. The performances of combinations of methods were also assessed. A cumulative sensitivity of 98% during a 1-year follow-up was obtained with the ELIFA plus ISAGA combination. Only one case of CT was missed by the ELIFA plus ISAGA combination, whereas three cases were missed by the IB plus ISAGA combination, even though 48% of patients with CT were treated with pyrimethamine-sulfonamides, which are known to inhibit antibody neosynthesis. A similar performance was obtained with either ELIFA or IB in combination with EIA. The difference in performance between ELIFA plus ISAGA and IB plus ISAGA was not statistically significant (P = 0.31), and we conclude that both combinations of tests can be used for the diagnosis of CT in newborns.