Vaccines for Conservation: Plague, Prairie Dogs & Black-Footed Ferrets as a Case Study

Gene drives gaining speed

Gene drives are selfish genetic elements that are transmitted to progeny at super-Mendelian (>50%) frequencies. Recently developed CRISPR-Cas9-based gene-drive systems are highly efficient in laboratory settings, offering the potential to reduce the prevalence of vector-borne diseases, crop pests and non-native invasive species. However, concerns have been raised regarding the potential unintended impacts of gene-drive systems. This Review summarizes the phenomenal progress in this field, focusing on optimal design features for full-drive elements (drives with linked Cas9 and guide RNA components) that either suppress target mosquito populations or modify them to prevent pathogen transmission, allelic drives for updating genetic elements, mitigating strategies including trans-complementing split-drives and genetic neutralizing elements, and the adaptation of drive technology to other organisms. These scientific advances, combined with ethical and social considerations, will facilitate the transparent and responsible advancement of these technologies towards field implementation.

Plague vaccines: new developments in an ongoing search

As the reality of pandemic threats challenges humanity, exemplified during the ongoing SARS-CoV-2 infections, the development of vaccines targeting these etiological agents of disease has become increasingly critical. Of paramount concern are novel and reemerging pathogens that could trigger such events, including the plague bacterium Yersinia pestis. Y. pestis is responsible for more human deaths than any other known pathogen and exists globally in endemic regions of the world, including the four corners region and Northern California in the USA. Recent cases have been scattered throughout the world, including China and the USA, with serious outbreaks in Madagascar during 2008, 2013-2014, and, most recently, 2017-2018. This review will focus on recent advances in plague vaccine development, a seemingly necessary endeavor, as there is no Food and Drug Administration-licensed vaccine available for human distribution in western nations, and that antibiotic-resistant strains are recovered clinically or intentionally developed. Progress and recent development involving subunit, live-attenuated, and nucleic acid-based plague vaccine candidates will be discussed in this review. KEY POINTS: • Plague vaccine development remains elusive yet critical. • DNA, animal, and live-attenuated vaccine candidates gain traction.

Assessing the immunogenicity of an inactivated monovalent vaccine in the endangered African wild dog (Lycaon pictus)

Captive held African wild dogs (Lycaon pictus) were vaccinated with a commercially available inactivated canine parvovirus (CPV) vaccine licensed for use in domestic dogs. Serological responses were recorded by testing for viral antibodies with the haemagglutination inhibition test (HAI) following a vaccination schedule involving two initial inoculations a month apart and an annual booster. Vaccines were delivered by hand injection or remotely (i.e. by dart). All naïve dogs vaccinated with Parvac® did seroconvert as determined by canine antibody titres ≥ 1:80 in one or more samples collected after inoculation. Duration of immunity (DOI) within the first year persisted for approximately 98 days only. To enable greater immunological protection revaccination should occur more frequently than once in a calendar year. No significant differences in the seroprotection rate were observed when comparing route of administration.