Search

Venezuelan, western, and eastern equine encephalitis virus (VEEV, WEEV, and EEEV) cause a febrile illness that may result in fatal neurological disease in humans and equines. Human infections are typically from mosquito bites, although cases from respiratory exposure in laboratory accidents have been documented. In addition to natural mosquito-borne infection, the potential biothreat inherent in the ability to disseminate these viruses via the respiratory route has driven the development of antiviral drugs for this route of exposure. To address this gap, we tested the prophylactic administration of a novel brain-penetrant, antiviral, BDGR-49, against a lethal intranasal challenge of VEEV, WEEV, or EEEV in BALB/c mouse model. BDGR-49 conferred 100% protection with 6 mg kg -1 twice per day for 6 days for VEEV, but not EEEV or WEEV. By 8 days post-infection (dpi), infectious virus, viral RNA, and viral antigen in the brain of BDGR-49-treated mice were significantly reduced. Brains of VEEV TrD-infected, BDGR-49-treated mice showed a significant reduction in the expression of genes associated with inflammation ( IFNB1 , TNF , IL6 , and CCL5 ) and cell death ( CASP4 , GSDMD , PYCARD , and ZBP1 ). At dpi 14, histopathology showed that neuronal lesions and inflammatory cell infiltrates were essentially absent, and viral antigen was not detected in the brains of VEEV TrD-infected, BDGR-49-treated mice. In summary, although BDGR-49 treatment showed significant promise for the treatment of mice exposed intranasally to VEEV, the more rapid and efficient entry of EEEV and WEEV by this route into the central nervous system will require additional optimization of the dosing regimen.IMPORTANCEProphylactic and therapeutic treatment of viruses that cause encephalitis requires fast-acting drugs that rapidly penetrate the blood-brain barrier. Currently, clinicians have only a limited set of antivirals for the treatment of neurotropic infections such as herpesviruses or HIV-1, and none for alphaviruses, and treatment outcomes remain poor. New medical countermeasures will address the gap in treatment of viral encephalitis such as those caused by the neurotropic alphaviruses and others.

Venezuelan equine encephalitis virus (VEEV) causes a febrile illness that can progress to neurological disease with the possibility of death in human cases. The evaluation and optimization of therapeutics that target brain infections demands knowledge of the host's response to VEEV, the dynamics of infection, and the potential for within-host evolution of the virus. We hypothesized that selective pressures during infection of the brain may differ temporally and spatially and so we investigated the dynamics of the host response, viral transcript levels, and genetic variation of VEEV TC-83 in eight areas of the brain in mice over 7 days post-infection (dpi). Viral replication increased throughout the brain until 5-6 dpi and decreased thereafter with neurons as the main site of viral replication. Low levels of genetic diversity were noted on 1 dpi and were followed by an expansion in the genetic diversity of VEEV and nonsynonymous (Ns) mutations that peaked by 5 dpi. The pro-inflammatory response and the influx of immune cells mirrored the levels of virus and correlated with substantial damage to neurons by 5 dpi and increased activation of microglial cells and astrocytes. The prevalence and dynamics of Ns mutations suggest that the VEEV is under selection within the brain and that progressive neuroinflammation may play a role in acting as a selective pressure. IMPORTANCE Treatment of encephalitis in humans caused by Venezuelan equine encephalitis virus (VEEV) from natural or aerosol exposure is not available, and hence, there is a great interest to address this gap. In contrast to natural infections, therapeutic treatment of infections from aerosol exposure will require fast-acting drugs that rapidly penetrate the blood-brain barrier, engage sites of infection in the brain and mitigate the emergence of drug resistance. Therefore, it is important to understand not only VEEV pathogenesis, but the trafficking of the viral population within the brain, the potential for within-host evolution of the virus, and how VEEV might evolve resistance., Competing Interests: The authors declare no conflict of interest.

Mycobacterium tuberculosis SigF is homologous to stress response and sporulation sigma factors in many bacteria. Consistent with a possible role in mycobacterial survival under stress conditions, M. tuberculosis sigF is strongly induced within cultured human macrophages and upon nutrient starvation, and SigF has been implicated in M. tuberculosis entry into stationary phase. On the other hand, SigF appears to contribute to the immune pathology of tuberculosis (TB), and a sigF-deficient mutant has altered cell membrane properties. Using an M. tuberculosis sigF deletion mutant, we show here that sigF is not required for bacillary survival under nutrient starvation conditions and within activated murine macrophages or for extracellular persistence in an in vivo granuloma model of latent TB infection. Using a chemically inducible recombinant strain to conditionally overexpress sigF, we did not observe arrest or retardation of growth in exponentially growing cultures or reduced susceptibility to rifampin and isoniazid. Consistent with our hypothesis that SigF may mediate TB immunopathogenesis by altering cell membrane properties, we found that overexpression of sigF resulted in the differential regulation of many cell wall-associated proteins, including members of the MmpL, PE, and PPE families, several of which have been shown to influence host-pathogen interactions. The most highly upregulated gene by quantitative reverse transcription-PCR at all time points following sigF induction was Rv3301c (phoY1), which encodes a probable transcriptional regulatory protein homologous to PhoU proteins involved in regulation of phosphate uptake. Using in vitro transcription analysis, we show that SigF directly regulates phoY1, whose proposed promoter sequence is GGATTG-N(16)-GGGTAT.