Extended Preclinical Safety, Efficacy and Stability Testing of a Live-attenuated Chikungunya Vaccine Candidate

<div><p>We recently described a new, live-attenuated vaccine candidate for chikungunya (CHIK) fever, CHIKV/IRES. This vaccine was shown to be well attenuated, immunogenic and efficacious in protecting against CHIK virus (CHIKV) challenge of mice and nonhuman primates. To further evaluate its preclinical safety, we compared CHIKV/IRES distribution and viral loads in interferon-α/β receptor-incompetent A129 mice to another CHIK vaccine candidate, 181/clone25, which proved highly immunogenic but mildly reactive in human Phase I/II clinical trials. Compared to wild-type CHIK virus, (wt-CHIKV), both vaccines generated lower viral loads in a wide variety of tissues and organs, including the brain and leg muscle, but CHIKV/IRES exhibited marked restrictions in dissemination and viral loads compared to 181/clone25, and was never found outside the blood, spleen and muscle. Unlike wt-CHIKV, which caused disrupted splenic architecture and hepatic lesions, histopathological lesions were not observed in animals infected with either vaccine strain. To examine the stability of attenuation, both vaccines were passaged 5 times intracranially in infant A129 mice, then assessed for changes in virulence by comparing parental and passaged viruses for footpad swelling, weight stability and survival after subcutaneous infection. Whereas strain 181/clone25 p5 underwent a significant increase in virulence as measured by weight loss (from <10% to >30%) and mortality (from 0 to 100%), CHIKV/IRES underwent no detectible change in any measure of virulence (no significant weight loss and no mortality). These data indicate greater nonclinical safety of the CHIKV/IRES vaccine candidate compared to 181/clone25, further supporting its eligibility for human testing.</p></div

A. Weight change, B. Footpad swelling, and; C. Survival of 6-7-week-old A129 mice inoculated intradermally in the footpad with 10⁴ PFU of wt CHIKV, parent vaccine strains, or 5^th intracranial passage vaccine strains from in duplicate, serial passage series (A and B).

<p>Statistical analysis for panels A and B was performed with one-way ANOVA. Single asterisks indicate p<0.05. Double asterisks indicate p<0.001. Statistical analysis for panel 8C was completed by Kaplan Meier.</p

Representative leg muscle histopathologic lesions in A129 mice 14 days after infection with 10⁴ PFU of the 181/clone25 or CHIKV/IRES vaccine candidate strains or PBS delivered in the footpad.

<p>Green arrows indicate cellular infiltrate and moderate myositis.</p

Mean viral loads in A129 mice after infection with 10⁴ PFU of wild-type CHIKV, or the 181/clone25 or CHIKV/IRES vaccine candidate strains delivered in the footpad.

<p>The limit of detection of the plaque assays was 60 PFU/g or ml. Data were analyzed by one-way ANOVA with a Bonferroni post hoc test for pairwise comparisons.</p

Consensus substitutions acquired by the 181/clone25 vaccine strain during serial mouse passages.

<p>Consensus substitutions acquired by the 181/clone25 vaccine strain during serial mouse passages.</p

Mortality in 10-week-old A129 mice after infection in the footpad with 10⁴ PFU of wt-CHIKV or wt-CHIKV/FfLuc.

<p>Statistical analysis was performed by Kaplan Meier.</p

Representative histopathologic liver lesions in A129 mice after infection with 10⁴ PFU of wild-type CHIKV, or the 181/clone25 or CHIKV/IRES vaccine candidate strains delivered in the footpad.

<p>Images for CHIKV/IRES, 181/clone25 and PBS are from 3 days post-infection. Green arrows indicate hepatic lesions.</p

"Submergence" of Western equine encephalitis virus: Evidence of positive selection argues against genetic drift and fitness reductions.

Understanding the circumstances under which arboviruses emerge is critical for the development of targeted control and prevention strategies. This is highlighted by the emergence of chikungunya and Zika viruses in the New World. However, to comprehensively understand the ways in which viruses emerge and persist, factors influencing reductions in virus activity must also be understood. Western equine encephalitis virus (WEEV), which declined during the late 20th century in apparent enzootic circulation as well as equine and human disease incidence, provides a unique case study on how reductions in virus activity can be understood by studying evolutionary trends and mechanisms. Previously, we showed using phylogenetics that during this period of decline, six amino acid residues appeared to be positively selected. To assess more directly the effect of these mutations, we utilized reverse genetics and competition fitness assays in the enzootic host and vector (house sparrows and Culex tarsalis mosquitoes). We observed that the mutations contemporary with reductions in WEEV circulation and disease that were non-conserved with respect to amino acid properties had a positive effect on enzootic fitness. We also assessed the effects of these mutations on virulence in the Syrian-Golden hamster model in relation to a general trend of increased virulence in older isolates. However, no change effect on virulence was observed based on these mutations. Thus, while WEEV apparently underwent positive selection for infection of enzootic hosts, residues associated with mammalian virulence were likely eliminated from the population by genetic drift or negative selection. These findings suggest that ecologic factors rather than fitness for natural transmission likely caused decreased levels of enzootic WEEV circulation during the late 20th century

Environmental Stewardship at the Savannah River Site: Generations of Success -13212

ABSTRACT Approximately sixty years ago, the Savannah River Site (SRS) was built to produce nuclear materials. SRS production operations impacted air, soil, groundwater, ecology, and the local environment. Throughout its history, SRS has addressed these contamination issues directly and has maintained a commitment to environmental stewardship. The Site boasts many environmental firsts. Notably, SRS was the first major Department of Energy (DOE) facility to perform a baseline ecological assessment. This pioneering effort, by Ruth Patrick and the Philadelphia Academy of Sciences, was performed during SRS planning and construction in the early 1950s. This unique early generation of work set the stage for subsequent efforts. Since that time, the scientists and engineers at SRS proactively identified environmental problems and developed and implemented effective and efficient environmental management and remediation solutions. This second generation, spanning the 1980s through the 2000s, is exemplified by numerous large and small cleanup actions to address metals and radionuclides, solvents and hydrocarbons, facility and area decommissioning, and ecological restoration. Recently, a third generation of environmental management was initiated as part of Enterprise SRS. This initiative to &quot;Develop and Deploy Next Generation Cleanup Technologies&quot; formalizes and organizes the major technology matching, development, and implementation processes associated with historical SRS cleanup success as a resource to support future environmental management missions throughout DOE. The four elements of the current, third generation, effort relate to: 1) transition from active to passive cleanup, 2) in situ decommissioning of large nuclear facilities, 3) new long term monitoring paradigms, and 4) a major case study related to support for recovery and restoration of the Japanese Fukushima-Daiichi nuclear power plant and surrounding environment