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Currently, real-world data on doravirine are scarce. In a national prospective cohort, we assessed the effectiveness and tolerability of switching to doravirine-based antiretroviral therapy (ART) in people with HIV.

The aim of the present study was to determine the in-vitro susceptibility of Toxoplasma gondii to dihydrofolate reductase inhibitors and sulphonamides alone, and in combination. It was found that pyrimethamine had the most potent anti-Toxoplasma activity, while sulphadiazine, sulphamethoxazole and sulphametrole were approximately equally effective, but only at a high concentration. The 50% inhibitory concentration of sulphamethoxazole was determined using different fixed concentrations of pyrimethamine or trimethoprim. It was found that a ten-fold increment of the concentration of pyrimethamine, reduced the IC50 of sulphamethoxazole 1000 times. The influence of trimethoprim on the IC50 of sulphamethoxazole was less concentration dependent. Addition of dihydrofolate or tetrahydrofolate did not influence the IC50 of pyrimethamine. In conclusion, the present dose recommendations for sulphonamides, when combined with pyrimethamine, may be unnecessarily high. There may be a justification for dose reduction of sulphonamides in order to prevent side effects.

The effectiveness of spiramycin for the treatment of rhesus monkey fetuses congenitally infected with Toxoplasma gondii was studied. Eight monkeys were infected at day 90 of pregnancy. This is comparable to the second trimester of organogenetic development in humans. Transmission of infection was found prenatally in five of the eight monkeys by detection of the parasite in the amniotic fluid. Treatment with spiramycin (20 mg/kg/day in two intermittent doses given intravenously) was started as soon as fetal infection was proven and was continued until birth. Nine to 14 days after initiation of treatment, the parasite was still detectable in amniotic fluid samples from four of these five cases. However, the parasite was detected only by PCR and not by mouse inoculation. T. gondii was also detected only by PCR in the placenta of one monkey that delivered prematurely. This monkey received spiramycin treatment for only 2 weeks. In the four monkeys that received treatment for about 7 weeks, the parasite was not present at birth in the placenta nor in amniotic fluid or neonatal organs. Spiramycin accumulates mainly in maternal tissues. Although concentrations in neonatal tissue were found to be 5 to 28 times higher than the corresponding concentrations in neonatal serum, the concentrations in neonatal tissue were still 11 to 16 times lower than those found in the mothers. However, no spiramycin was found in the fetal brains. Early treatment with spiramycin may prevent transmission of infection to the fetus but most probably cannot interrupt an existing brain infection, which is the most severe outcome of congenital toxoplasmosis in humans.

Transplacental transfer of spiramycin was investigated in a rhesus monkey model to study whether the antibiotic reaches therapeutic levels in the fetus. Spiramycin concentrations were measured by bioassay and high-performance liquid chromatography. Pharmacokinetic parameters were determined for bioactive spiramycin as measured by the bioassay. Pharmacokinetic pilot studies showed that spiramycin distribution follows a two-compartment model in rhesus monkeys. Following a single intravenous dose of 50 or 250 mg, dose-dependent kinetics were observed. At a dose of 50 mg, 10% of the dose was excreted unchanged in the urine. At the higher dose of 250 mg, an oliguric effect was observed. Spiramycin concentrations in fetal serum were measured over time while the maternal concentration was maintained at a constant level. During a 5-h experiment, a maximum fetal-maternal serum ratio of 0.27 was found. In three fetuses, concentrations in serum and tissue were measured following intravenous administration of 50 mg of spiramycin twice daily to the mother for at least 7 days. The fetal-maternal serum ratios were found to be 0.4 to 0.58 after intravenous administration of the final dose of 50 mg to the mother. It appeared that spiramycin accumulated in the soft tissues, especially in the liver and spleen, of both the mother and the fetus. The concentration in placental tissue appeared to be 10 to 20 times that of the concentration in fetal serum. The concentration of spiramycin in amniotic fluid was about five times higher than the concentration in fetal serum. Another important observation was that absolutely no spiramycin was found in the brain.

The diagnosis of toxoplasmosis in congenitally infected children or in immunocompromised patients can be difficult; serology is not reliable, and the diagnosis must be based on the combination of symptomatology and the direct demonstration of the parasite in clinical specimens by microscopy, antigen detection, or inoculation of samples into mice or tissue cultures. These techniques are either insensitive or time-consuming. To determine the value of the polymerase chain reaction (PCR) for the diagnosis of Toxoplasma gondii infections, we compared this technique with conventional detection techniques, such as microscopy, tissue culturing, and mouse inoculation. We were able to detect T. gondii by PCR in clinical specimens and tissue samples that were obtained postmortem from a bone marrow recipient with cerebral toxoplasmosis and from three congenitally infected children. The presence of T. gondii was demonstrated in brain tissue, cerebrospinal fluid, the heart, and skeletal muscle tested fresh or after fixation in Formalin. In only one sample was T. gondii isolated by mouse inoculation but not detected by PCR. Because it is a sensitive, relatively rapid, and specific method and because it can be applied to a variety of different clinical samples, PCR can be considered a valuable additional tool for the identification of T. gondii infections.

1-Naphthaleneacetic acid (1-NAA), required for in vitro flower bud formation, was taken up by pedicel explants of tobacco (Nicotiana tabacumL.) in large amounts and rapidly metabolized into various conjugates. These conjugates have been tentatively identified in four thin-layer Chromatographic systems using authentic standards as references. The major metabolite formed during the first hours of culture comigrated with 1-NAA-glucoside (1-NAGlu). From the 6th hour on, most 1-NAA had been converted into a yet unidentified metabolite. 1-NAglu was an intermediate in the formation of this metabolite. After 24 h, 1-NAA-aspartate (1-NAAsp) became the second major metabolite. The increase in 1-NAAsp formation was induced by 1-NAA. The inactive analog 2-naphthaleneacetic acid (2-NAA) was metabolized similar to 1-NAA, but was unable to increase the formation of the aspartate conjugate. When explants were fed labeled 1-NAGlu, 1-NAAsp or the major unidentified metabolite, radioactivity became associated with free 1-NAA and all major conjugates, indicating interconversion of conjugates and breakdown to free 1-NAA. A regulatory role of conjugation in maintaining a particular level of free 1-NAA in the tissue is proposed herein.

The efficacy of the combination of pyrimethamine and sulfadiazine for the treatment of congenital Toxoplasma gondii infection in rhesus monkeys was studied. The dosage regimen for pyrimethamine and sulfadiazine was established by pharmacokinetic studies in two monkeys. Those studies showed that the distributions of both drugs followed a one-compartment model. The serum elimination half-lives were found to be 5.2 h for sulfadiazine and 44.4 h for pyrimethamine. Sulfadiazine reached a maximum concentration in serum of 58.7 micrograms/ml, whereas a maximum concentration in serum of 0.22 micrograms/ml was found for pyrimethamine. Ten monkeys were infected intravenously with T. gondii at day 90 of pregnancy, which is comparable to the second trimester of organogenetic development in humans. Treatment was administered to six monkeys, in whose fetuses infection was diagnosed antenatally. From the moment that fetal infection was proven, the monkeys were treated throughout pregnancy with 1 mg of pyrimethamine per kg of body weight per day and 50 mg of sulfadiazine per kg of body weight per day orally. The therapy was supplemented with 3.5 mg of folinic acid once a week. No toxic side effects were found with this drug regimen. The parasite was no longer detectable in the next consecutive amniotic fluid sample, taken 10 to 13 days after treatment was started. Furthermore, T. gondii was also not found in the neonate at birth. The parasite was still present at birth in three of four untreated fetuses that served as controls. Both drugs crossed the placenta very well. Concentrations in fetal serum varied from 0.05 to 0.14 micrograms/ml for pyrimethamine and from 1.0 to 5.4 micrograms/ml for sulfadiazine. In addition, pyrimethamine was found to accumulate in the brain tissue, with concentrations being three to four times higher than the corresponding concentrations in serum. Thirty percent of the sulfadiazine was found to reach the brain tissue when compared with the corresponding serum concentration. when administered early after the onset of infection, the combination of pyrimethamine and sulfadiazine was clearly effective in reducing the number of parasites in the fetus to undetectable levels.

Sulfadiazine and the metabolites N4-acetyl-sulfadiazine, 4-OH-sulfadiazine, 5-OH-sulfadiazine, 5-OH-glucuronide-sulfadiazine, and 5-OH-sulfate-sulfadiazine were tested separately and in combination with pyrimethamine for the inhibitory activity on Toxoplasma gondii growth in vitro. Except for N4-acetyl-sulfadiazine, all sulfa compounds possessed anti-Toxoplasma activity. The addition of 0.05 micrograms of pyrimethamine per ml, a concentration which in itself is not inhibitory, potentiated the microbial activity of sulfadiazine and its metabolites 100 fold.

To investigate whether the polymerase chain reaction (PCR) on the BI gene of Toxoplasma gondii could contribute to the diagnosis of cerebral toxoplasmosis in patients with AIDS, we retrospectively tested CSF samples from 20 patients with AIDS suspected of having cerebral toxoplasmosis for the presence of T. gondii. Suspicion of cerebral toxoplasmosis was based on accepted criteria. Nine patients with AIDS with IgG antibodies to T. gondii but who were not suspected of having cerebral toxoplasmosis and four patients with AIDS seronegative for T. gondii served as negative control patients. T. gondii was demonstrated by PCR in the CSF from 13 of the 20 patients with AIDS suspected of having cerebral toxoplasmosis but was not demonstrated in the CSF samples from the nine control patients seropositive for T. gondii and the four control patients seronegative for T. gondii. The data were statistically evaluated. This study shows the value of PCR for the detection of T. gondii in CSF for the diagnosis of cerebral toxoplasmosis in patients with AIDS.