Chronic oral toxicity of 3-nitro-1,2,4-triazol-5-one (NTO) in rats.

To evaluate the effects of chronic exposure to 3-nitro-1,2,4-triazol-5-one (nitrotriazolone, NTO), male and female rats were given ad libitum access to NTO in drinking water at concentrations of 0, 36, 110, 360, 1100, and 3600 mg/L for one year. NTO did not affect body weight, body weight gain, or food consumption in either sex. No treatment-related effects were observed in clinical chemistry and hematology parameters at the 6 month or one year sampling. At both the interim and final sampling, males and females from the 3600 mg/L group produced smaller volumes of urine that was darker, more concentrated, and contained more bilirubin than the controls. Total and motile sperm counts were not affected by NTO treatment. Absolute and relative organ weights did not differ between control and NTO treated groups for either sex. Spontaneous age-related neoplasms occurred in controls and NTO groups at rates consistent with published historic controls. NTO was generally non-toxic in females at the doses tested. Toxicity in males was limited to testicular toxicity as demonstrated in previous studies. Chronic exposure did not result in testicular toxicity at lower doses and the toxicity observed only in the high dose group in this study is less severe than that observed in shorter exposures of previous studies, suggesting differences may be associated with influences of study design on kinetics. A Benchmark Dose (BMD) of 1604 mg/L (76 mg/kg-day) and a Benchmark Dose Lower Bound (BMDL10) of 921 mg/L (44 mg/kg-day) were determined for chronic effects of NTO in male rats.

Neuromuscular anomalies following oral exposure to 3-nitro-1,2,4-triazol-5-one (NTO) in a one-generation study with Japanese quail (Coturnix japonica).

Substances used as explosives in munitions by the military often result in environmental releases through manufacturing, testing, training, and combat activities. The toxicity of 3-nitro-1,2,4-triazol-5-one (nitrotriazolone or NTO) was evaluated following oral exposure in Japanese quail (Coturnix japonica) to determine if environmental releases result in unacceptable risks to avian populations. In an acute test at the limit dose (2000 mg/kg), one female was ataxic, exhibited tremors, and showed signs of neurological toxicity approximately 24 h after dosing. In a subsequent one-generation study, parental generation (F0) birds were exposed orally to 1000, 500, 100, or 20mg/kg-day NTO suspended in corn oil. After 5 consecutive days of dosing, 2-week-old birds receiving 1000 mg/kg-day displayed ataxia, convulsions, backward arching of the neck (opisthotonos), and alternated between prostrate inactivity and ataxic wing activity. Birds in the 500 mg/kg-day group exhibited neuromuscular anomalies after 17 days exposure. Ultimately, all of the 1000 mg/kg-day birds and all but one of the 500 mg/kg-day birds met euthanasia criteria and were humanely euthanized prior to behavioral and reproductive evaluation. As such, first-generation (F1) birds were exposed to 100 or 20 mg/kg-day NTO. Mild neuromuscular anomalies occurred in 10% of F1 birds from the 100 mg/kg-day group, but not in birds from 20 mg/kg-day or controls in either generation. Vacuolization of cerebellum and/or the brainstem was observed on histopathologic examination in a dose-dependent manner. Therefore, brain vacuoles and neuromuscular anomalies were identified as critical endpoints in this study. A mean Benchmark Dose (BMD) for brain vacuoles of 62 mg/kg-day was derived for male and female F0-generation quail, which corresponded to a Benchmark Dose Low (BMDL10) of 35 mg/kg-day.

Efficacy of favipiravir (T-705) in nonhuman primates infected with Ebola virus or Marburg virus.

Favipiravir is a broad-spectrum antiviral agent that has demonstrated efficacy against Ebola virus (EBOV) in rodents. However, there are no published reports of favipiravir efficacy for filovirus infection of nonhuman primates (NHPs). Here we evaluated the pharmacokinetic profile of favipiravir in NHPs, as well as in vivo efficacy against two filoviruses, EBOV and Marburg virus (MARV). While no survival benefit was observed in two studies employing once- or twice-daily oral dosing of favipiravir during EBOV infection of NHPs, an antiviral effect was observed in terms of extended time-to-death and reduced levels of viral RNA. However, oral dosing in biosafety level-4 (BSL-4) presents logistical and technical challenges, and repeated anesthesia events may potentially worsen survival outcome in animals. For the third study of treatment of MARV infection, we therefore made use of catheters, jackets, and tethers for intravenous (IV) dosing and blood collection, which minimized the requirement for repeated anesthesia events. When MARV infection was treated with IV favipiravir, five of six animals (83%) survived infection, while all untreated NHPs succumbed. An accompanying report presents the results of favipiravir treatment of EBOV infection in mice.

Accurate virus quantitation using a Scanning Transmission Electron Microscopy (STEM) detector in a scanning electron microscope.

A method for accurate quantitation of virus particles has long been sought, but a perfect method still eludes the scientific community. Electron Microscopy (EM) quantitation is a valuable technique because it provides direct morphology information and counts of all viral particles, whether or not they are infectious. In the past, EM negative stain quantitation methods have been cited as inaccurate, non-reproducible, and with detection limits that were too high to be useful. To improve accuracy and reproducibility, we have developed a method termed Scanning Transmission Electron Microscopy - Virus Quantitation (STEM-VQ), which simplifies sample preparation and uses a high throughput STEM detector in a Scanning Electron Microscope (SEM) coupled with commercially available software. In this paper, we demonstrate STEM-VQ with an alphavirus stock preparation to present the method's accuracy and reproducibility, including a comparison of STEM-VQ to viral plaque assay and the ViroCyt Virus Counter.

Identification and pathological characterization of persistent asymptomatic Ebola virus infection in rhesus monkeys.

Ebola virus (EBOV) persistence in asymptomatic humans and Ebola virus disease (EVD) sequelae have emerged as significant public health concerns since the 2013-2016 EVD outbreak in Western Africa. Until now, studying how EBOV disseminates into and persists in immune-privileged sites was impossible due to the absence of a suitable animal model. Here, we detect persistent EBOV replication coinciding with systematic inflammatory responses in otherwise asymptomatic rhesus monkeys that had survived infection in the absence of or after treatment with candidate medical countermeasures. We document progressive EBOV dissemination into the eyes, brain and testes through vascular structures, similar to observations in humans. We identify CD68+ cells (macrophages/monocytes) as the cryptic EBOV reservoir cells in the vitreous humour and its immediately adjacent tissue, in the tubular lumina of the epididymides, and in foci of histiocytic inflammation in the brain, but not in organs typically affected during acute infection. In conclusion, our data suggest that persistent EBOV infection in rhesus monkeys could serve as a model for persistent EBOV infection in humans, and we demonstrate that promising candidate medical countermeasures may not completely clear EBOV infection. A rhesus monkey model may lay the foundation to study EVD sequelae and to develop therapies to abolish EBOV persistence.