Piyapat Pongnarin

Activation of Indoleamine 2,3-Dioxygenase in Patients with Scrub Typhus and Its Role in Growth Restriction of Orientia tsutsugamushi

Background Our earlier genome-wide expression study revealed up-regulation of a tryptophan-catabolizing enzyme, indoleamine 2,3-dioxygenase (IDO1), in patients with scrub typhus. This gene has been previously reported to have anti-microbial activity in a variety of infectious diseases; therefore, we aimed to prove whether it is also involved in host defense against Orientia tsutsugamushi (OT) infection. Methodology/Principal Findings Using LC-MS, we observed an increased ratio of serum L-kynurenine to serum L-tryptophan in patients with scrub typhus, which suggests an active catalytic function of this enzyme upon the illness. To evaluate the effect of IDO1 activation on OT infection, a human macrophage-like cell line THP-1 was used as a study model. Although transcription of IDO1 was induced by OT infection, its functional activity was not significantly enhanced unless the cells were pretreated with IFN-γ, a potent inducer of IDO1. When the degree of infection was evaluated by quantitative real-time PCR, the relative number of OT 47 kDa gene per host genes, or infection index, was markedly reduced by IFN-γ treatment as compared to the untreated cultures at five days post-infection. Inhibition of IDO1 activity in IFN-γ treated cultures by 1-methyl-L-tryptophan, a competitive inhibitor of IDO1, resulted in partial restoration of infection index; while excessive supplementation of L-tryptophan in IFN-γ treated cultures raised the index to an even higher level than that of the untreated ones. Altogether, these data implied that IDO1 was partly involved in restriction of OT growth caused by IFN-γ through deprivation of tryptophan. Conclusions/Significance Activation of IDO1 appeared to be a defensive mechanism downstream of IFN-γ that limited intracellular expansion of OT via tryptophan depletion. Our work provided not only the first link of in vivo activation of IDO1 and IFN-γ-mediated protection against OT infection but also highlighted the promise of this multifaceted gene in scrub typhus research.

Association of Nevirapine Levels with Rash or Hepatotoxicity Among HIV-Infected Thai Women.

Background: We performed a nested case-control study of Thai women prescribed nevirapine-based antiretroviral therapy (ART) to determine if development of rash or hepatotoxicity during the first 24 weeks of treatment is associated with plasma nevirapine concentrations. Method: From May 2005-January 2007, we enrolled 217 women initiating nevirapine-based ART in Thailand. Cases (n = 54) were women who during the first 24 weeks of treatment with nevirapine developed rash (any grade, n = 42) or hepatotoxicity (≥grade 2, n = 22, [10 had both]). Controls were the next enrolled woman who was confirmed not to meet the case definition during the first 24 weeks. Nevirapine concentrations after the two week lead-in dose of 200 mg once daily were compared between cases and controls by Wilcoxon rank-sum tests. Results: We found no difference in Week 2 pre-dose nevirapine concentrations: cases median = 3,528 ng/mL (n = 24), controls median = 3,150ng/mL (n = 30), p = 0.5. Cases had higher post-dose nevirapine concentrations (median = 6,150 ng/mL, n = 21) than controls (median = 4,746 ng/mL, n = 20, p = 0.02). When limited to cases who developed a rash at Week 2, we found no differences in the pre-dose (median = 3,270 ng/mL, n = 12, p = 0.9) or post-dose nevirapine concentration (median = 5,443 ng/mL, n = 9, p = 0.4) compared with controls. Conclusions: We cannot conclude definitively that nevirapine concentrations at two weeks of therapy are associated with rash or hepatotoxicity. It is unlikely that therapeutic drug monitoring at that time will improve identification of patients at risk for rash or hepatotoxicity.

Prevalence and risk factors for chloroquine maculopathy and role of plasma chloroquine and desethylchloroquine concentrations in predicting chloroquine maculopathy.

To determine the prevalence and to identify the risk factors of chloroquine maculopathy (CM), and to evaluate the association of plasma chloroquine (CQ) and desethylchloroquine (DCQ) levels and CM.

A randomized, open-label, 2-period, crossover bioequivalence study of two oral formulations of 75 mg oseltamivir in healthy Thai volunteers.

AIM Oseltamivir, an ester prodrug of its active carboxylate metabolite, is an effective neuraminidase inhibitor used to treat influenza A and B virus infections. The purpose of this study was to compare the bioavailability of two 75 mg oral formulations of oseltamivir: a generic drug, GOP-A-Flu (test, Government Pharmaceutical Organization, Thailand) and Tamiflu (reference, Hoffmann-La Roche Ltd., Nutley, NJ, USA) in healthy volunteers. SUBJECTS AND METHODS A single-dose, randomized, 2-sequence, crossover study was conducted in 24 healthy Thai volunteers. Each volunteer received a 75 mg capsule of the reference or test drugs under fasting conditions. Blood samples were collected before dosing and at various time points up to 48 hours after dosing and analyzed for plasma oseltamivir and oseltamivir carboxylate concentrations. The pharmacokinetic parameters including Cmax, AUC0-t, AUC0-infinity, tmax and t1/2 were analyzed using the non-compartmental method. Drug safety was assessed. RESULTS 23 volunteers completed both treatment periods. The geometric mean ratios (test/reference) between the two formulations of oseltamivir were 96.83% (90% CI, 76.85 - 123.15%) for Cmax 103.66% (86.44 - 113.56%) for AUC0-t, and 103.98% (86.44 - 113.56%) for AUC0-infinity. Those of oseltamivir carboxylate were 102.17% (90% CI, 90.90 - 109.10%) for Cmax, 103.95% (90.90 - 109.10%) for AUC0-t, and 103.95% (90.92 - 109.08%) for AUC0-infinity. No significant difference of the tmax of oseltamivir and oseltamivir carboxylate between the two formulations was detected (p > 0.05). Both formulations were well-tolerated. CONCLUSION Although the Cmax of oseltamivir was the only parameter not entirely within the equivalence criteria, the two capsule formulations were considered bioequivalent in terms of rate and extent of absorption regarding its active carboxylate metabolite.