Dysregulation of Toll-Like Receptor 7 Compromises Innate and Adaptive T Cell Responses and Host Resistance to an Attenuated West Nile Virus Infection in Old Mice.

UNLABELLED: The elderly are known to have enhanced susceptibility to infections and an impaired capacity to respond to vaccination. West Nile virus (WNV), a mosquito-borne flavivirus, has induced severe neurological symptoms, mostly in the elderly population. No vaccines are available for human use. Recent work showed that an attenuated WNV, a nonstructural (NS) 4B-P38G mutant, induced no lethality but strong immune responses in young (6- to 10-week-old) mice. While studying protective efficacy, we found unexpectedly that old (21- to 22-month) mice were susceptible to WNV NS4B-P38G mutant infection but were protected from subsequent lethal wild-type WNV challenge. Compared to responses in young mice, the NS4B-P38G mutant triggered higher inflammatory cytokine and interleukin-10 (IL-10) production, a delayed γδ T cell expansion, and lower antibody and WNV-specific T cell responses in old mice. Toll-like receptor 7 (TLR7) is expressed on multiple types of cells. Impaired TLR7 signaling in old mice led to dendritic cell (DC) antigen-presenting function compromise and a reduced γδ T cell and regulatory T cell (Treg) expansion during NS4B-P38G mutant infection. R848, a TLR7 agonist, decreased host vulnerability in NS4B-P38G-infected old mice by enhancing γδ T cell and Treg expansion and the antigen-presenting capacity of DCs, thereby promoting T cell responses. In summary, our results suggest that dysregulation of TLR7 partially contributes to impaired innate and adaptive T cell responses and an enhanced vulnerability in old mice during WNV NS4B-P38G mutant infection. R848 increases the safety and efficacy during immunization of old mice with the WNV NS4B-P38G mutant. IMPORTANCE: The elderly are known to have enhanced susceptibility to infections and an impaired capacity to respond to vaccination. West Nile virus (WNV), an emerging mosquito-borne flavivirus, has induced severe neurological symptoms more frequently in the elderly population. No vaccines are available for human use. Here, we used an aged mouse model to investigate the protective efficacy of an attenuated WNV, the nonstructural 4B-P38G mutant, which was previously shown to induce no lethality but strong immune responses in young adult mice. Studies that contribute to a mechanistic understanding of immune defects in the elderly will allow the development of strategies to improve responses to infectious diseases and to increase vaccine efficacy and safety in aging individuals.

A review of genetic methods and models for analysis of coronavirus-induced severe pneumonitis.

Coronaviruses (CoVs) have been studied for over 60 years, but have only recently gained notoriety as deadly human pathogens with the emergence of severe respiratory syndrome CoV and Middle East respiratory syndrome virus. The rapid emergence of these viruses has demonstrated the need for good models to study severe CoV respiratory infection and pathogenesis. There are, currently, different methods and models for the study of CoV disease. The available genetic methods for the study and evaluation of CoV genetics are reviewed here. There are several animal models, both mouse and alternative animals, for the study of severe CoV respiratory disease that have been examined, each with different pros and cons relative to the actual pathogenesis of the disease in humans. A current limitation of these models is that no animal model perfectly recapitulates the disease seen in humans. Through the review and analysis of the available disease models, investigators can employ the most appropriate available model to study various aspects of CoV pathogenesis and evaluate possible antiviral treatments that may potentially be successful in future treatment and prevention of severe CoV respiratory infections.

Real-time telomerase assay of less-invasively collected esophageal cell samples.

Genomic and proteomic efforts have discovered a complex list of biomarkers that identify human disease, stratify risk of disease within populations, and monitor drug or therapy responses for treatment. Attention is needed to characterize these biomarkers and to develop high-throughput technologies to evaluate their accuracy and precision. Telomerase activity is correlated with tumor progression, indicating cells that express telomerase possess aggressive clinical behavior and that telomerase activity could be a clinically important cancer biomarker. Traditionally, the detection of cancer has involved invasive procedures to procure samples. There is a need for less invasive approaches suitable for population- and clinic-based assays for cancer early detection. Esophageal balloon cytology (EBC) is a low-invasive screening technique, which samples superficial epithelial cells from the esophagus. Since telomerase activity is absent in superficial cells of normal esophageal squamous epithelium but is often present in superficial cells from dysplastic lesions and ESCCs, measuring telomerase activity in EBC samples may be a good way to screen for these lesions. The development of rapid real-time telomerase activity assays raises the possibility of extending such screening to high-risk populations. In this study, we evaluate the feasibility of using rapid Real-Time Telomerase Repeat Amplification Protocol (RTTRAP) for the analysis of NIST telomerase candidate reference material and esophageal clinical samples. The telomerase activity of eight EBC samples was also measured by capillary electrophoresis of RTTRAP products, RApidTRAP, and hTERT mRNA RT-PCR assays. These findings demonstrate the feasibility of using the RTTRAP assay in EBC samples and suggest that individuals from high-risk populations can be screened for telomerase activity.

Lessons from the Murine Models of West Nile Virus Infection.

West Nile virus (WNV), a mosquito-borne, single positive-stranded RNA virus, has been the leading cause of arboviral encephalitis in the U.S. and other parts of the world over the past decade. Up to 50 % of WNV convalescent patients were reported to have long-term neurological sequelae or chronic kidney diseases. However, there are neither antiviral drugs nor vaccines available for humans. The underlying mechanism of the long-term sequelae is not clearly understood either. Animal models have been an effective tool to investigate viral pathogenesis and host immunity in humans. Here, we will review several commonly used murine models of WNV infection.