Construction and in vitro characterisation of virus-vectored immunocontraceptive candidates derived from felid alphaherpesvirus 1.

There is a pressing need for effective feral cat management globally due to overabundant feline populations, disease transmission and their destructive impact on biodiversity. Virus-vectored immunocontraception (VVIC) is an attractive method for cat population management. Virus-vectored immunocontraceptives could be self-disseminating through horizontal transmission of the VVIC in feral cat populations, or they may be modified to act as non-transmissible vaccine-type immunocontraceptives for delivery to individual cats. These later constructs may be particularly attractive for use in owned (pet) cats and stray cats but could also be used for feral cats that are caught, vaccinated, and released. Here, we report the construction of three felid alphaherpesvirus 1 (FHV-1) derived immunocontraceptive candidates containing genes that encode for feline zona pellucida subunit 3 (ZP3) and gonadotropin-releasing hormone (GnRH). Two of the vaccine candidates were engineered to include disruptions to the thymidine kinase viral virulence gene to reduce the ability of the vaccines to be horizontally transmitted. Analysis of in vitro growth characteristics and protein expression are reported, and their potential for use as a population management tool for cats is discussed.

Use of feline herpesvirus as a vaccine vector offers alternative applications for feline health.

Herpesviruses are attractive vaccine vector candidates due to their large double stranded DNA genome and latency characteristics. Within the scope of veterinary vaccines, herpesvirus-vectored vaccines have been well studied and commercially available vectored vaccines are used to help prevent diseases in different animal species. Felid alphaherpesvirus 1 (FHV-1) has been characterised as a vector candidate to protect against a range of feline pathogens. In this review we highlight the methods used to construct FHV-1 based vaccines and their outcomes, while also proposing alternative uses for FHV-1 as a viral vector.

A wAlbB Wolbachia Transinfection Displays Stable Phenotypic Effects across Divergent Aedes aegypti Mosquito Backgrounds.

Aedes mosquitoes harboring intracellular Wolbachia bacteria are being released in arbovirus and mosquito control programs. With releases taking place around the world, understanding the contribution of host variation to Wolbachia phenotype is crucial. We generated a Wolbachia transinfection (wAlbBQ) in Aedes aegypti and performed backcrossing to introduce the infection into Australian or Malaysian nuclear backgrounds. Whole Wolbachia genome sequencing shows that the wAlbBQ transinfection is nearly identical to the reference wAlbB genome, suggesting few changes since the infection was first introduced to A. aegypti over 15 years ago. However, these sequences were distinct from other available wAlbB genome sequences, highlighting the potential diversity of wAlbB in natural Aedes albopictus populations. Phenotypic comparisons demonstrate the effects of wAlbB infection on egg hatching and nuclear background on fecundity and body size but no interactions between wAlbB infection and nuclear background for any trait. The wAlbB infection was stable at high temperatures and showed perfect maternal transmission and cytoplasmic incompatibility regardless of the host background. Our results demonstrate the stability of wAlbB across host backgrounds and point to its long-term effectiveness for controlling arbovirus transmission and mosquito populations. IMPORTANCEWolbachia bacteria are being used to control the transmission of dengue virus and other arboviruses by mosquitoes. For Wolbachia release programs to be effective globally, Wolbachia infections must be stable across mosquito populations from different locations. In this study, we transferred Wolbachia (strain wAlbB) to Aedes aegypti mosquitoes with an Australian genotype and introduced the infection to Malaysian mosquitoes through backcrossing. We found that the phenotypic effects of Wolbachia are stable across both mosquito backgrounds. We sequenced the genome of wAlbB and found very few genetic changes despite spending over 15 years in a novel mosquito host. Our results suggest that the effects of Wolbachia infections are likely to remain stable across time and host genotype.

Effects of Alternative Blood Sources on Wolbachia Infected Aedes aegypti Females within and across Generations.

Wolbachia bacteria have been identified as a tool for reducing the transmission of arboviruses transmitted by Aedes aegypti. Research groups around the world are now mass rearing Wolbachia-infected Ae. aegypti for deliberate release. We investigated the fitness impact of a crucial element of mass rearing: the blood meal required by female Ae. aegypti to lay eggs. Although Ae. aegypti almost exclusively feed on human blood, it is often difficult to use human blood in disease-endemic settings. When females were fed on sheep or pig blood rather than human blood, egg hatch rates decreased in all three lines tested (uninfected, or infected by wMel, or wAlbB Wolbachia). This finding was particularly pronounced when fed on sheep blood, although fecundity was not affected. Some of these effects persisted after an additional generation on human blood. Attempts to keep populations on sheep and pig blood sources only partly succeeded, suggesting that strong adaptation is required to develop a stably infected line on an alternative blood source. There was a decrease in Wolbachia density when Ae. aegypti were fed on non-human blood sources. Density increased in lines kept for multiple generations on the alternate sources but was still reduced relative to lines kept on human blood. These findings suggest that sheep and pig blood will entail a cost when used for maintaining Wolbachia-infected Ae. aegypti. These costs should be taken into account when planning mass release programs.