Vesicular Stomatitis Virus Elicits Early Transcriptome Response in Culicoides sonorensis Cells

Viruses that are transmitted by arthropods, or arboviruses, have evolved to successfully navigate both the invertebrate and vertebrate hosts, including their immune systems. Biting midges transmit several arboviruses including vesicular stomatitis virus (VSV). To study the interaction between VSV and midges, we characterized the transcriptomic responses of VSV-infected and mock-infected Culicoides sonorensis cells at 1, 8, 24, and 96 h post inoculation (HPI). The transcriptomic response of VSV-infected cells at 1 HPI was significant, but by 8 HPI there were no detectable differences between the transcriptome profiles of VSV-infected and mock-infected cells. Several genes involved in immunity were upregulated (ATG2B and TRAF4) or downregulated (SMAD6 and TOLL7) in VSV-treated cells at 1 HPI. These results indicate that VSV infection in midge cells produces an early immune response that quickly wanes, giving insight into in vivo C. sonorensis VSV tolerance that may underlie their permissiveness as vectors for this virus.

Of Murines and Humans: Modeling Persistent Powassan Disease in C57BL/6 Mice

Powassan infection is caused by two closely related, tick-transmitted viruses of the genus Flavivirus (family Flaviviridae): Powassan virus lineage I (POWV) and lineage II (known as deer tick virus [DTV]). Infection is typically asymptomatic or mild but can progress to neuroinvasive disease. Approximately 10% of neuroinvasive cases are fatal, and half of the survivors experience long-term neurological sequelae. Understanding how these viruses cause long-term symptoms as well as the possible role of viral persistence is important for developing therapies. We intraperitoneally inoculated 6-week-old C57BL/6 mice (50% female) with 103 focus-forming units (FFU) DTV and assayed for infectious virus, viral RNA, and inflammation during acute infection and 21, 56, and 84 days postinfection (dpi). Although most mice (86%) were viremic 3 dpi, only 21% of the mice were symptomatic and 83% recovered. Infectious virus was detected only in the brains of mice sampled during the acute infection. Viral RNA was detected in the brain until 84 dpi, but the magnitude decreased over time. Meningitis and encephalitis were visible in acute mice and from mice sampled at 21 dpi. Inflammation was observed until 56 dpi in the brain and 84 dpi in the spinal cord, albeit at low levels. These results suggest that the long-term neurological symptoms associated with Powassan disease are likely caused by lingering viral RNA and chronic inflammation in the central nervous system rather than by a persistent, active viral infection. The C57BL/6 model of persistent Powassan mimics illness in humans and can be used to study the mechanisms of chronic disease. IMPORTANCE Half of Powassan infection survivors experience long-term, mild to severe neurological symptoms. The progression from acute to chronic Powassan disease is not well understood, severely limiting treatment and prevention options. Infection of C57BL/6 mice with DTV mimics clinical disease in humans, and the mice exhibit CNS inflammation and viral RNA persistence until at least 86 dpi, while infectious virus is undetectable after 12 dpi. These findings suggest that the long-term neurological symptoms of chronic Powassan disease are in part due the persistence of viral RNA and the corresponding long-term inflammation of the brain and spinal cord. Our work demonstrates that C57BL/6 mice can be used to study the pathogenesis of chronic Powassan disease.

Prescription opioid use during pregnancy and risk for preterm birth or term low birthweight

OBJECTIVE

Examine the relationship between prescription opioid analgesic use during pregnancy and preterm birth or term low birthweight.

DESIGN, SETTING, AND PARTICIPANTS

We analyzed data from the National Birth Defects Prevention Study, a US multisite, population-based study, for births from 1997 to 2011. We defined exposure as self-reported prescription opioid use between one month before conception and the end of pregnancy, and we dichotomized opioid use duration by ≤7 days and >7 days.

MAIN OUTCOME MEASURES

We examined the association between opioid use and preterm birth (defined as gestational age <37 weeks) and term low birthweight (defined as <2500 g at gestational age ≥37 weeks).

RESULTS

Among 10,491 singleton mother/infant pairs, 470 (4.5 percent) reported opioid use. Among women reporting opioid use, 236 (50 percent) used opioids for > 7 days; codeine (170, 36 percent) and hydrocodone (163, 35 percent) were the most commonly reported opioids. Opioid use was associated with slightly increased risk for preterm birth [adjusted odds ratio, 1.4; 95 percent confidence interval, 1.0, 1.9], particularly with hydrocodone [1.6; 1.0, 2.6], meperidine [2.5; 1.2, 5.2], or morphine [3.0; 1.5, 6.1] use for any duration; however, opioid use was not significantly associated with term low birthweight.

CONCLUSIONS

Preterm birth occurred more frequently among infants of women reporting prescription opioid use during pregnancy. However, we could not determine if these risks relate to the drug or to indications for use. Patients who use opioids during pregnancy should be counseled by their practitioners about this and other potential risks associated with opioid use in pregnancy.

Evolution of resistance to fluoroquinolones by dengue virus serotype 4 provides insight into mechanism of action and consequences for viral fitness

Drugs against flaviviruses such as dengue (DENV) and Zika (ZIKV) virus are urgently needed. We previously demonstrated that three fluoroquinolones, ciprofloxacin, enoxacin, and difloxacin, suppress replication of six flaviviruses. To investigate the barrier to resistance and mechanism(s) of action of these drugs, DENV-4 was passaged in triplicate in HEK-293 cells in the presence or absence of each drug. Resistance to ciprofloxacin was detected by the seventh passage and to difloxacin by the tenth, whereas resistance to enoxacin did not occur within ten passages. Two putative resistance-conferring mutations were detected in the envelope gene of ciprofloxacin and difloxacin-resistant DENV-4. In the absence of ciprofloxacin, ciprofloxacin-resistant viruses sustained a significantly higher viral titer than control viruses in HEK-293 and HuH-7 cells and resistant viruses were more stable than control viruses at 37 °C. These results suggest that the mechanism of action of ciprofloxacin and difloxacin involves interference with virus binding or entry.

Old Drugs with New Tricks: Efficacy of Fluoroquinolones to Suppress Replication of Flaviviruses

Repurposing FDA-approved compounds could provide the fastest route to alleviate the burden of disease caused by flaviviruses. In this study, three fluoroquinolones, enoxacin, difloxacin and ciprofloxacin, curtailed replication of flaviviruses Zika (ZIKV), dengue (DENV), Langat (LGTV) and Modoc (MODV) in HEK-293 cells at low micromolar concentrations. Time-of-addition assays suggested that enoxacin suppressed ZIKV replication at an intermediate step in the virus life cycle, whereas ciprofloxacin and difloxacin had a wider window of efficacy. A129 mice infected with 1 × 10⁵ plaque-forming units (pfu) ZIKV FSS13025 (n = 20) or phosphate buffered saline (PBS) (n = 11) on day 0 and treated with enoxacin at 10 mg/kg or 15 mg/kg or diluent orally twice daily on days 1–5 did not differ in weight change or virus titer in serum or brain. However, mice treated with enoxacin showed a significant, five-fold decrease in ZIKV titer in testes relative to controls. Mice infected with 1 × 10² pfu ZIKV (n = 13) or PBS (n = 13) on day 0 and treated with 15 mg/kg oral enoxacin or diluent twice daily pre-treatment and days 1–5 post-treatment also did not differ in weight and viral load in the serum, brain, and liver, but mice treated with enoxacin showed a significant, 2.5-fold decrease in ZIKV titer in testes relative to controls. ZIKV can be sexually transmitted, so reduction of titer in the testes by enoxacin should be further investigated.

Modifying connectivity to promote state change reversal: the importance of geomorphic context and plant-soil feedbacks

Alternative states maintained by feedbacks are notoriously difficult, if not impossible, to reverse. Although positive interactions that modify soil conditions may have the greatest potential to alter self-reinforcing feedbacks, the conditions leading to these state change reversals have not been resolved. In a 9-yr study, we modified horizontal connectivity of resources by wind or water on different geomorphic surfaces in an attempt to alter plant-soil feedbacks and shift woody-plant-dominated states back toward perennial grass dominance. Modifying connectivity resulted in an increase in litter cover regardless of the vector of transport (wind, water) followed by an increase in perennial grass cover 2 yr later. Modifying connectivity was most effective on sandy soils where wind is the dominant vector, and least effective on gravelly soils on stable surfaces with low sediment movement by water. We found that grass cover was related to precipitation in the first 5 yr of our study, and plant-soil feedbacks developed following 6 yr of modified connectivity to overwhelm effects of precipitation on sandy, wind-blown soils. These feedbacks persisted through time under variable annual rainfall. On alluvial soils, either plant-soil feedbacks developed after 7 yr that were not persistent (active soils) or did not develop (stable soils). This novel approach has application to drylands globally where desertified lands have suffered losses in ecosystem services, and to other ecosystems where connectivity-mediated feedbacks modified at fine scales can be expected to impact plant recovery and state change reversals at larger scales, in particular for wind-impacted sites.