RESUMO
Human monocytic ehrlichiosis, an emerging tick-borne disease, is caused by Ehrlichia chaffeensis. Infections with the pathogen are also common in the canine host. Our previous studies demonstrated that functional disruption within the E. chaffeensis phage head-to-tail connector protein gene results in bacterial attenuation, creating a modified live attenuated vaccine (MLAV). The MLAV confers protective immunity against intravenous and tick transmission challenges one month following vaccination. In this study, we evaluated the duration of MLAV protection. Dogs vaccinated with the MLAV were challenged with wild-type E. chaffeensis via intravenous infection at 4-, 8-, and 12-months post-vaccination. Immunized dogs rapidly cleared the wild-type pathogen infection and tested positive for bacteremia less frequently than unvaccinated controls. While immune responses varied among dogs, vaccinees consistently mounted IgG and CD4+ T-cell responses specific to E. chaffeensis throughout the assessment period. Our findings demonstrate that MLAV-mediated immune protection persists for at least one year against wild-type bacterial infection, marking a major advancement in combating this serious tick-borne disease. The data presented here serve as the foundation for further studies, elucidating the molecular mechanisms underlying virulence and vaccine development and aiding in preventing the diseases caused by E. chaffeensis and other tick-borne rickettsial pathogens.
RESUMO
Introduction: The applications of fumigation and the challenges that high-containment facilities face in achieving effective large volume decontamination are well understood. The Biosecurity Research Institute at Kansas State University sought to evaluate a novel system within their biosafety level 3 (BSL-3) and animal biosafety level 3 agriculture (ABSL-3Ag) facility. Methods: The system chosen for this study is the CURIS® Hybrid Hydrogen PeroxideTM (HHPTM) system, comprising a mobile 36-pound (16 kg) device delivering a proprietary 7% hydrogen peroxide (H2O2) solution. To examine the system's efficacy in multiple laboratory settings, two BSL-3 laboratories (2,281 [65 m3] and 4,668 ft3 [132 m3]) with dropped ceiling interstitial spaces and an ABSL-3Ag necropsy suite (44,212 ft3 [1,252 m3]) with 21-foot (6.4 m) ceilings were selected. Biological indicators (BIs) of Geobacillus stearothermophilus (1.7 × 106 organisms) on steel spore carriers and H2O2 chemical indicators (CIs) were used to provide validation. Results: After cycle optimization, the smaller laboratory had a total of 60 BIs over two treatments that demonstrated a greater than 6-log reduction of bacterial spores. The larger laboratory (192 BIs) and the necropsy suite (206 BIs) had no BIs positive for spore growth when incubated at 60°C for 24 h per manufacturer's specifications. Conclusion: Overall successful results through multiple components of this study demonstrate that the HHP device, paired with the pulsed 7% H2O2 solution, achieved efficacy regardless of variables in laboratory size and layout. Perceived challenges such as 21-ft (6.4 m) ceiling heights, active equipment, and difficult to access ceiling interstitial spaces proved unfounded. Given the successful sterilization of all challenged BIs, the HHP system presents a useful alternative for high level decontamination within BSL-3 and ABSL-3Ag facilities.