Concomitant bedaquiline and delamanid therapy in patients with drug-resistant extra-pulmonary tuberculosis in Mumbai, India.

Background: World Health Organization suggests concurrent bedaquiline-delamanid (BDQ-DLM) as part of individualised regimens for eligible patients with pulmonary drug-resistant tuberculosis (DR-TB); however, data for patients with drug-resistant extrapulmonary tuberculosis (EPTB) is extremely limited. This study documents the treatment outcomes and adverse events associated with concurrent BDQ-DLM-based regimens in patients with drug-resistant EPTB at a Médecins Sans Frontières clinic in Mumbai, India. Methods: Retrospective cohort study based on routinely collected programmatic data. Individualised regimens were based on drug-susceptibility testing and previous drug exposure. Drug-resistant EPTB patients initiated on regimens containing concurrent BDQ and DLM from April 2016 to October 2019 were included. Patients who completed treatment were followed up at 12 months. Results: Of 17 patients, median age was 23 years (IQR = 21-30 years) and 12/17 (71 %) were female. Pre-extensively drug-resistant tuberculosis and extensively drug-resistant TB was reported in 13/17 (76.4 %) and 2/17 (11.7 %) patients respectively. Microbiological reports were unavailable for two patients with central nervous system TB. Lymph node TB was the commonest form of EPTB in 9/17 (53 %) of patients. Median duration of treatment was 18.9 months. At least one grade three or four severe adverse event (SAE) was reported by 13/17 (76.4 %) patients. Thirteen (76.4 %) patients had favourable outcomes. None of the patients relapsed or died in the one-year period of post-treatment follow-up. Conclusion: Concurrent BDQ-DLM-based regimens in drug-resistant EPTB were effective and associated with manageable adverse events.

Correction: Ambulatory management of pre- and extensively drug resistant tuberculosis patients with imipenem delivered through port-a-cath: A mixed methods study on treatment outcomes and challenges.

[This corrects the article DOI: 10.1371/journal.pone.0234651.].

Absence of lenadogene nolparvovec DNA in a brain tumor biopsy from a patient in the REVERSE clinical study, a case report.

BACKGROUND: Leber Hereditary Optic Neuropathy (LHON) is a rare, maternally-inherited mitochondrial disease that primarily affects retinal ganglion cells (RGCs) and their axons in the optic nerve, leading to irreversible, bilateral severe vision loss. Lenadogene nolparvovec gene therapy was developed as a treatment for patients with vision loss from LHON caused by the most prevalent m.11778G > A mitochondrial DNA point mutation in the MT-ND4 gene. Lenadogene nolparvovec is a replication-defective recombinant adeno-associated virus vector 2 serotype 2 (AAV2/2), encoding the human wild-type MT-ND4 protein. Lenadogene nolparvovec was administered by intravitreal injection (IVT) in LHON patients harboring the m.11778G > A ND4 mutation in a clinical development program including one phase 1/2 study (REVEAL), three phase 3 pivotal studies (REVERSE, RESCUE, REFLECT), and one long-term follow-up study (RESTORE, the follow-up of REVERSE and RESCUE patients). CASE PRESENTATION: A 67-year-old woman with MT-ND4 LHON, included in the REVERSE clinical study, received a unilateral IVT of lenadogene nolparvovec in the right eye and a sham injection in the left eye in May 2016, 11.4 months and 8.8 months after vision loss in her right and left eyes, respectively. The patient had a normal brain magnetic resonance imaging with contrast at the time of diagnosis of LHON. Two years after treatment administration, BCVA had improved in both eyes. The product was well tolerated with mild and resolutive anterior chamber inflammation in the treated eye. In May 2019, the patient was diagnosed with a right temporal lobe glioblastoma, IDH-wildtype, World Health Organization grade 4, based on histological analysis of a tumor excision. The brain tumor was assessed for the presence of vector DNA by using a sensitive validated qPCR assay targeting the ND4 sequence of the vector. CONCLUSION: ND4 DNA was not detected (below 15.625 copies/µg of genomic DNA) in DNA extracted from the brain tumor, while a housekeeping gene DNA was detected at high levels. Taken together, this data shows the absence of detection of lenadogene nolparvovec in a brain tumor (glioblastoma) of a treated patient in the REVERSE clinical trial 3 years after gene therapy administration, supporting the long-term favorable safety of lenadogene nolparvovec.

Carcinogenicity Evaluation of Baclofen in TgrasH2 Mice.

Baclofen is a γ-aminobutyric acid-B receptor agonist used for control of spastic muscle activity and as a treatment for alcohol abuse. The review of the nonclinical database suggested a data gap for potential carcinogenicity following long-term use. Regulatory requirements for pharmaceutical safety testing of cancer-causing potential have historically included 2-year rodent studies in rats and mice. The availability of transgenic models with greater specificity and sensitivity to carcinogens provides safety testing alternatives that align with the 3Rs. The carcinogenicity of baclofen was evaluated in CB6F1-TgrasH2 transgenic mice following daily oral administration at 45, 90, and 180 mg/kg/d for 26 weeks, preceded by a 2-week drug-conditioning period. There were no treatment-related palpable masses or neoplastic findings, and survival rates were not affected by the baclofen treatment. In conclusion, baclofen was considered as noncarcinogenic in CB6F1-TgrasH2 mice, which is consistent with results previously obtained in a 2-year rat study.

Biodistribution of intravitreal lenadogene nolparvovec gene therapy in nonhuman primates.

Lenadogene nolparvovec (Lumevoq) gene therapy was developed to treat Leber hereditary optic neuropathy (LHON) caused by the m.11778G > A in MT-ND4 that affects complex I of the mitochondrial respiratory chain. Lenadogene nolparvovec is a replication-defective, single-stranded DNA recombinant adeno-associated virus vector 2 serotype 2, containing a codon-optimized complementary DNA encoding the human wild-type MT-ND4 subunit protein. Lenadogene nolparvovec was administered by unilateral intravitreal injection in MT-ND4 LHON patients in two randomized, double-masked, and sham-controlled phase III clinical trials (REVERSE and RESCUE), resulting in bilateral improvement of visual acuity. These and other earlier results suggest that lenadogene nolparvovec may travel from the treated to the untreated eye. To investigate this possibility further, lenadogene nolparvovec was unilaterally injected into the vitreous body of the right eye of healthy, nonhuman primates. Viral vector DNA was quantifiable in all eye and optic nerve tissues of the injected eye and was detected at lower levels in some tissues of the contralateral, noninjected eye, and optic projections, at 3 and 6 months after injection. The results suggest that lenadogene nolparvovec transfers from the injected to the noninjected eye, thus providing a potential explanation for the bilateral improvement of visual function observed in the LHON patients.

One Step Forward: Successful End-of-Treatment Outcomes of Patients With Drug-Resistant Tuberculosis Who Received Concomitant Bedaquiline and Delamanid in Mumbai, India.

BACKGROUND: The Médecins Sans Frontières Clinic in Mumbai, India, has been providing concomitant bedaquiline (BDQ) and delamanid (DLM) in treatment regimen for patients with drug-resistant tuberculosis (DR-TB) and limited therapeutic options, referred from other healthcare institutions, since 2016. The study documents the end-of-treatment outcomes, culture-conversion rates, and serious adverse events (SAEs) during treatment. METHODS: This was a retrospective cohort study based on routinely collected program data. In clinic, treatment regimens are designed based on culture drug sensitivity test patterns and previous drug exposures, and are provided for 20-22 months. BDQ and DLM are extended beyond 24 weeks as off-label use. Patients who initiated DR-TB treatment including BDQ and DLM (concomitantly for at least 4 weeks) during February 2016-February 2018 were included. RESULTS: Of the 70 patients included, the median age was 25 (interquartile range [IQR], 22-32) years and 56% were females. All except 1 were fluoroquinolone resistant. The median duration of exposure to BDQ and DLM was 77 (IQR, 43-96) weeks. Thirty-nine episodes of SAEs were reported among 30 (43%) patients, including 5 instances of QTc prolongation, assessed as possibly related to BDQ and/or DLM. The majority (69%) had culture conversion before 24 weeks of treatment. In 61 (87%), use of BDQ and DLM was extended beyond 24 weeks. Successful end-of-treatment outcomes were reported in 49 (70%) patients. CONCLUSIONS: The successful treatment outcomes of this cohort show that regimens including concomitant BDQ and DLM for longer than 24 weeks are effective and can be safely administered on an ambulatory basis. National TB programs globally should scale up access to life-saving DR-TB regimens with new drugs.

Weight of evidence and human relevance evaluation of the benfluralin mode of action in rodents (Part I): Liver carcinogenesis.

Benfluralin, an herbicide of the dinitroaniline class used in weed control, was first registered in the United States in 1970. Increased incidence of liver tumors was observed in the 2 year dietary carcinogenicity studies. A review of the toxicology database provides evidence that the mode of action (MOA) of benfluralin responsible for hepatocellular adenoma and carcinoma in rodents depends on activation of the constitutive androstane (CAR)/pregnane X (PXR) receptors, that triggers enzyme induction and altered gene expression leading to hepatocyte proliferation. After prolonged exposures at high dose levels, altered hepatic foci and liver tumors are observed. This hepatocarcinogenic MOA has been described in rodents following long-term dietary exposures to other CAR/PXR activator chemicals, such as phenobarbital, and is generally considered as non-relevant in humans due to differences between human and rodent responses. We analyzed the existing and newly acquired toxicology data to establish that the hepatocarcinogenic MOA of benfluralin in rodents includes the same key events previously described in the rodent MOA of phenobarbital. A weight of evidence approach was taken to establish temporal and dose-related concordance of the causal key events supporting the conclusion that rodent liver carcinogenicity of benfluralin is unlikely to be relevant for human cancer risk.

Weight of Evidence and Human Relevance Evaluation of the Benfluralin Mode of Action in Rats (Part II): Thyroid carcinogenesis.

Benfluralin is an herbicide of the dinitroaniline class used to control grasses and weeds. In a 2 year dietary study in rats, benfluralin increased incidences of thyroid follicular adenoma and carcinoma at high dietary concentrations (≥2500 ppm). The benfluralin toxicology database suggests the mode of action (MOA) is initiated by induction of liver metabolizing enzymes, particularly thyroid hormone specific UGTs, a major pathway for T4 clearance in rats. As reported with phenobarbital, this effect triggers negative feedback regulation, increasing thyroid stimulating hormone (TSH) release into circulating blood. When sustained over time, this leads to thyroid changes such as follicular hypertrophy, hyperplasia and thyroid follicular tumors with chronic exposures. The described MOA was previously established in rat studies with various chemical activators of xenobiotic receptors in the liver. It is generally considered as non-relevant in humans, due to differences between humans and rats in T4 turnover and susceptibility to this carcinogenic MOA. A structured methodology based on the IPCS/MOA/Human Relevance framework was used in the evaluation of available benfluralin data, and the conclusion was determined that the carcinogenic potential of benfluralin in the thyroid is not relevant in humans.

Ambulatory management of pre- and extensively drug resistant tuberculosis patients with imipenem delivered through port-a-cath: A mixed methods study on treatment outcomes and challenges.

BACKGROUND: Imipenem, an intravenous antibiotic is recommended for use in drug resistant tuberculosis (DR-TB) when an effective regimen with combination of other second line drugs is not possible. Though the treatment success rates with carbapenems are promising, the twice daily injection of Imipenem usually requires patients to be hospitalized. The Médecins Sans Frontières independent clinic in Mumbai, India implemented ambulatory and home based management of patients receiving Imipenem through the use of port-a-cath. OBJECTIVE: We aimed to describe the adverse events and treatment outcomes of ambulatory pre- and XDR-TB patients initiated on imipenem through port-a-cath between January 2015 and June 2018 and to explore the challenges with this regimen as perceived by healthcare providers and patients. METHODS: A convergent mixed methods study with quantitative (longitudinal descriptive study using the routine data) and qualitative (descriptive study) part conducted concurrently. For the quantitative component, all XDR-TB and pre-XDR-TB initiated on imipenem containing regimen during January 2015-June 2018 were included. For qualitative component, interviews were carried out including patients who initiated on imipenem (n = 5) and healthcare providers (n = 7) involved in providing treatment. Treatment outcomes, culture conversion and adverse events during treatment were described. Thematic analysis was carried out for qualitative component. RESULTS: Of the 70 patients included, the mean age was 28.1 (standard deviation: 11.2) years and 36 (51.4%) were females. Fifty one (72.9%) had XDR-TB. All patients were resistant to fluoroquinilone, levofloxacin. Vomiting was reported by 55 (78.6%) patients and at least one episode of QTC prolongation (more than 500 msec by Fredrecia method) was detected in 25 (35.7%). Port-a-cath block and infection was seen in 11 (15.7%) and 20 (28.6%) patients respectively. Favourable outcomes were seen in 43 (61.4%) patients. Mortality was seen in 22 (31.4%) patients, 2 (2.9%) were lost-to-follow-up and 3 (4.3%) were declared as treatment failure. The overarching theme of the qualitative analysis was: Challenges in delivering Imipenem via port-a-cath device in ambulatory care. Major challenges identified were difficulties in adhering to drug dose timelines, vomiting, restricted mobility due to port-a-cath, paucity of infection control and space constraints at patients' home for optimal care. CONCLUSION: Administration of imipenem was feasible through port-a-cath. Though outcomes with ambulatory based imipenem containing regimens were promising, there were several challenges in providing care. The feasibility of infusion at day care facilities needs to explored to overcome challenges in infusion at patients home.

Routine viral load monitoring and enhanced adherence counselling at a public ART centre in Mumbai, India.

BACKGROUND: Routine viral-load (VL) measurements along with enhanced adherence counselling (EAC) are recommended to achieve virological suppression among people living with HIV/AIDS (PLHA) on anti-retroviral therapy (ART). The Mumbai Districts AIDS Control Society along with Médecins Sans Frontières has provided routine VL measurements and EAC to PLHA on ART at King Edward Memorial (KEM) hospital, Mumbai since October-2016. This study aims to describe the initial VL results and impact of EAC on viral suppression and factors associated with initial viral non-suppression among patients with an initial detectable VL, in a cohort of patients tested between October-2016 and September-2018. METHODS: This is a descriptive study of PLHA on ART who received VL testing and EAC during October-2016 to September-2018. Log-binomial regression was used to identify factors associated with a high VL. RESULTS: Among 3849 PLHA who underwent VL testing, 1603(42%) were female and median age was 42 years (IQR:35-48). Majority were referred for routine testing (3432(89%)) and clinical/immunological failure (233(6%)). Overall, 3402(88%) PLHA had suppressed VL at initial testing. Among 3432 tested for routine monitoring, 3141(92%) had VL suppressed. Of 291 with VL>1000c/ml, 253(87%) received EAC and after repeat VL, 70(28%) had VL<1000c/ml. Among 233 referred for clinical/immunological failure, 122(52%) had VL>1000c/ml and 109 have been switched to second-line ART. CD4 count<500 (aOR-5.0[95%CI 3.8-6.5]), on ART for<5 years (aOR-1.5[1.1-2.0]) and age<15 years (aOR-5.2[3.0-8.9]) were associated with an initial VL>1000c/ml. Factors associated with follow-up VL suppression included EAC (p<0.05) and being on second-line ART (p<0.05). CONCLUSION: Results from a routine VL program in public sector in India were encouraging and in line with UNAIDS 90-90-90 targets. Routine VL monitoring along with EAC resulted in early switch to alternative optimised regimens while also preventing unnecessary switches. Along with the vital scale up of routine VL monitoring, implementation of enhanced adherence strategies for patients with detectable viral load should be ensured.

Yield of Systematic Longitudinal Screening of Household Contacts of Pre-Extensively Drug Resistant (PreXDR) and Extensively Drug Resistant (XDR) Tuberculosis Patients in Mumbai, India.

While risk of tuberculosis (TB) is high among household contacts (HHCs) of pre-extensively drug resistant (pre-XDR) TB and XDR-TB, data on yield of systematic longitudinal screening are lacking. We aim to describe the yield of systematic longitudinal TB contact tracing among HHCs of patients with pre-XDR-TB and XDR-TB. At the Médecins Sans Frontières (MSF) clinic, Mumbai, India a cohort comprising 518 HHCs of 109 pre-XDR and XDR index cases was enrolled between January 2016 and June 2018. Regular HHC follow-ups were done till one year post treatment of index cases. Of 518 HHCs, 23 had TB (21 on TB treatment and two newly diagnosed) at the time of first visit. Of the rest, 19% HHCs had no follow-ups. Fourteen (3.5%) TB cases were identified among 400 HHCs; incidence rate: 2072/100,000 person-years (95% CI: 1227-3499). The overall yield of household contact tracing was 3% (16/518). Of 14 who were diagnosed with TB during follow-up, six had drug susceptible TB (DSTB); six had pre-XDR-TB and one had XDR-TB. Five of fourteen cases had resistance patterns concordant with their index case. In view of the high incidence of TB among HHCs of pre-XDR and XDR-TB cases, follow-up of HHCs for at least the duration of index cases' treatment should be considered.

Interspecies Comparison of Control Data From Embryo-Fetal Development Studies in Sprague-Dawley Rats, New Zealand White Rabbits, and Göttingen Minipigs.

Species-dependent differences in relative incidence of spontaneous variations and malformations should be considered in the assessment of the translational value of reproductive and developmental safety assessments. The objective of this evaluation was to compare litter parameters and the frequency of external, visceral, and skeletal malformations and variations across species in the Sprague-Dawley rat, New Zealand White rabbit, and Göttingen minipig and to determine whether notable differences exist. Pregnant female rats (n = 824), rabbits (n = 540), and minipigs (n = 70) from vehicle control groups were included in the analysis, equating to 10,749 rat, 5,073 rabbit, and 378 pig fetuses collected at term by cesarean delivery. Preimplantation loss was more frequent than postimplantation loss in the rat and rabbit, whereas the opposite was observed in the minipig. Several external and visceral malformations and variations such as domed head, bent tail, abdominal edema, and anal atresia were observed in all 3 species. Visceral malformations of the heart and major blood vessels were remarkably more frequent in the minipig and rabbit, respectively; ventricular and atrium septum defects were observed in 1.9% and 2.1%, respectively, for the minipig fetuses, whereas they were observed in equal or less than 0.02% among the rat and rabbit fetuses evaluated in this study. Understanding species-dependent differences in spontaneous variations and malformations can be useful for the interpretation of embryo-fetal development study results. The current analysis identified relevant differences between commonly used species in reproductive toxicology with potential implications for data assessment.

Perspectives From the 12th Annual Minipig Research Forum: Early Inclusion of the Minipig in Safety Assessment Species Selection Should be the Standard Approach.

Over the last decade, the minipig has been established as a species which can be used in biomedical research, including drug development safety assessment. There are no mandatory regulatory guidelines regarding species selection strategy for safety assessment; hence, choice is at the discretion of companies responsible for drug development. A survey of member companies by IQ DruSafe (2016) highlighted inconsistent and low use of the minipig. At the 12th Annual Minipig Research Forum in 2018, presentations and a workshop examined current practices and considered if the minipig could be utilized more from earliest drug development stages. Despite the agreed utility of scientific data and validity of the minipig, especially for small molecules, each company has its own approach in nonrodent species selection, without consistent rationale. The overall objective should be to ensure the most appropriate species is selected and is scientifically based, with the minipig systematically included from early screening stages.

A human relevance investigation of PPARα-mediated key events in the hepatocarcinogenic mode of action of propaquizafop in rats.

Propaquizafop is an herbicide with demonstrated hepatocarcinogenic activity in rodents. A rodent-specific mode of action (MOA) in the liver via activation of peroxisome proliferator-activated receptor α (PPARα) has been postulated based on existing data. Experience with PPARα-inducing pharmaceuticals indicates a lack of human relevance of this MOA. The objective of the present investigation was to evaluate the dependency of early key events leading to liver tumors on PPARα activation in wildtype (WT) compared to PPARα-knockout (KO) rats following 2 weeks exposure to 75, 500 and 1000 ppm propaquizafop in the diet. In WT rats, both WY-14643 (50 mg/kg bw/day) and propaquizafop (dose-dependently) induced marked increases in liver weights, correlating with liver enlargement and hepatocellular hypertrophy, along with increased CYP4A and acyl-CoA oxidase mRNA expression and enzyme activities versus controls, while in KO rats liver weight was mildly increased only at the high dose with minimal microscopic correlates and without any changes in liver peroxisomal or CYP4A activities. In addition, BrdU labeling resulted in higher numbers and density of positive hepatocytes versus controls in WT but not in KO rats, indicating increased mitotic activity and cell proliferation only in WT rats, thus confirming the PPARα-dependency of the biochemical and histological changes in the liver. Based on an assessment of the results of this investigation, together with existing propaquizafop data according to the MOA-Human Relevance Framework, we conclude that liver tumors observed in rodents after dietary administration of propaquizafop do not pose a relevant health risk to humans.

QT interval correction for drug-induced changes in body temperature during integrated cardiovascular safety assessment in regulatory toxicology studies in dogs: A case study.

INTRODUCTION: Cardiovascular safety assessment requires accurate evaluation of QT interval, which depends on the length of the cardiac cycle and also on core body temperature (BT). Increases in QT interval duration have been shown to be associated with decreases in BT in dogs. METHODS: An example of altered QT interval duration associated with changes in body temperature observed during a 4-week regulatory toxicology study in dogs is presented. Four groups of Beagle dogs received the vehicle or test item once on Day 1, followed by a 4-week observation period. Electrocardiogram (ECG) parameters were continuously recorded on Days 1 and 26 by jacketed external telemetry (JET). Core body temperature (BT) was measured with a conventional rectal thermometer at appropriate time-points during the Day 1 recording period. RESULTS: Decreased BT was observed approximately 2h after treatment on Day 1, along with increased QT interval duration corrected according to the Van de Water formula (QTcV), but the effect was no longer observed after correction for changes in BT [QTcVcT=QTcV-14(37.5-BT)] according to the Van der Linde formula. No significant changes in QTcV were reported at the end of the observation period, on Day 26. DISCUSSION: The present study demonstrates that core body (rectal) temperature can easily be monitored at appropriate time-points during JET recording in regulatory toxicology studies in dogs, in order to correct QT interval duration values for treatment-related changes in BT. The successful application of the Van der Linde formula to correct QTc prolongation for changes in BT was demonstrated.

Folpet-induced short term cytotoxic and proliferative changes in the mouse duodenum.

Folpet, an agricultural fungicide, induces tumors in the mouse gastrointestinal tract, primarily in the duodenum. Bioassays show a threshold for tumors at ~1000 ppm dietary administration. We investigated the early histologic changes to the mouse duodenum in mice fed a diet containing 6000 ppm folpet for 28 days. Reversibility of folpet-induced changes was evaluated after treatment for 28 days and a recovery period of 17 days. Macroscopic changes in the cecum (dilatation) and duodenum (roughening) were evident by day 7, continued through day 28, then returned to normal by recovery day 17. The duodenal mucosa also appeared to be thickened. Macroscopic changes to the forestomach were also evident as a rough surface or depressions; they also decreased in incidence and severity in the recovery animals. Histologic changes of the duodenum (crypt cell hyperplasia, villous hypertrophy, numerous intraepithelial lymphocytes, and elongation of epithelial columnar cells) were evident in all treated mice by day 7 and continued and increased in severity through 28 days of administration. The incidence and severity of these findings was reduced on recovery day 17, indicating reversibility. Histologic changes (epithelial hyperplasia and hyperkeratosis) of the non-glandular squamous epithelium in the forestomach occurred later than the changes to the duodenum. The incidence and severity of these changes also lessened by recovery day 17. These early histologic changes support a non-DNA reactive mode of action for folpet carcinogenicity in mice involving the key events of mucosal cytotoxicity with consequent regenerative proliferation. Exposures that are not sufficient to produce cytotoxicity would also not lead to tumor formation.

Carcinogenic mode of action of folpet in mice and evaluation of its relevance to humans.

A framework has been evolving for evaluation of mode of action (MOA) of rodent toxicity and carcinogenicity findings and their relevance to humans. Folpet produces duodenal glandular tumors in mice, but is not carcinogenic in rats. A wealth of information is available regarding folpet's mode of action, providing an excellent example of how this tumor can be evaluated using this framework. Folpet reacts with thiol groups, and is rapidly hydrolyzed at pH 7. Both reactions produce thiophosgene that reacts with thiols and other functional groups. Folpet is not genotoxic in vivo. At sufficiently high, prolonged dietary doses, folpet irritates the mouse duodenum, resulting in cytotoxicity with consequent regenerative proliferation and ultimately tumor development. Forestomach lesions secondary to cytotoxicity are also induced. Dogs have stomachs similar to humans and show no evidence of gastrointestinal toxicity or tumor formation at exposure levels at least as high as rodents. The data support a MOA in mice involving cytotoxicity and regenerative proliferation. Based on MOA analysis and assessment of human relevance, folpet, like captan, another trichloromethylthio-related fungicide with similar toxic and carcinogenic effects, is not likely to be a human carcinogen at dose levels that do not cause cytotoxicity and regenerative proliferation.

Genetic toxicology of folpet and captan.

Folpet and captan are fungicides whose genotoxicity depends on their chemical reaction with thiols. Multiple mutagenicity tests have been conducted on these compounds due to their positive activity in vitro and their association with gastrointestinal tumors in mice. A review of the collective data shows that these compounds have in vitro mutagenic activity but are not genotoxic in vivo. This dichotomy is primarily due to the rapid degradation of folpet and captan in the presence of thiol-rich matrices typically found in vivo. Genotoxicity has not been found in the duodenum, the mouse tumor target tissue. It is concluded that folpet like captan presents an unlikely risk of genotoxic effects in humans.

Effects of diesel exhaust particles and carbon black on induction of dust mite allergy in brown norway rats.

Particulate matter (PM) components of air pollution have been associated with mortality and health risks in susceptible populations including asthmatics. More than a decade of PM research has demonstrated that these effects do not occur indiscriminately and are related to particle size, surface area, and chemical composition. Experimental evidence in rodents indicates that inhaled or instilled diesel exhaust particles (DEPs) increase lung injury, inflammation, and allergic airway responses, and that ultra-fine carbon black (UFCB) particles cause more pulmonary inflammation than fine carbon black (FCB) particles in a dose-dependent manner. Our preliminary work determined that a dose of 100 mug of FCB, UFCB, or DEPs (NIST SRM 2975) was sufficient to enhance pulmonary inflammation in Brown Norway (BN) rats 24 hours after intratracheal (IT) instillation of the particles. In the current investigation, we sought to compare, on a mass basis, the effects of a 100 mug dose of these particles on allergic sensitization to house dust mite (HDM) antigen. Immediate airway responses (IAR) to HDM challenge and a battery of proinflammatory, allergic, and acute injury responses in the lung were then measured two and seven days post-challenge. DEPs exposure increased 8 of 10 responses including IAR and levels of IL-4, IL-13, TNFalpha, total protein, cysteinyl leukotrienes, and eosinophils in bronchoalveolar lavage fluid (BALF). UFCB and FCB significantly enhanced 4 of 10 and 2 of 10 of these responses compared to saline, respectively. Among other responses that were not statistically elevated with particle treatment, mean values for FCB were higher than for UFCB. Particles administered prior to challenge rather than prior to sensitization did not significantly enhance any of these responses above levels of saline controls. We conclude that on a mass basis, DEPs had the greatest potential to enhance allergic induction, indicating that chemical composition is more important than particle size in determining potency for this health effect.