A mouse model of haemoplasma infection, in vitro cultivation of haemoplasmas and steps towards better diagnosis of and vaccination against haemoplasmosis

Abstract

The absence of a mouse model and successful in vitro cultivation systems for haemoplasmas have been a major hindrance in their research, impacting our understanding of haemoplasma pathobiology and delaying diagnostic means and vaccination strategies.
Rodent haemoplasmas were sourced from wild-caught field mice (Apodemus spp.) and 16S rRNA gene sequences used for identification and phylogenetic classification within the haemotropic Mycoplasma species. Novel rodent haemoplasmas were successfully passaged into immunocompetent, SPF Wistar rats and C57BL/6 mice. Haemoplasma-species specific quantitative polymerase chain reaction (qPCR) assays were developed for Mycoplasma haemomuris and Eperythrozoon coccoides and duplexed with an internal control qPCR to monitor infection in mice. Infection kinetics, partial protection from re-infection with the same isolate of M. haemomuris, and a lack of cross-protection resulting from previous E. coccoides-infection were described. Additionally, M. haemomuris was shown to induce anaemia during primary infection of mice.
To assess the use of M. haemomuris-induced haemoplasmosis of mice as a surrogate model for feline infection with Mycoplasma haemofelis, a cytokine signature of naïve infection and protection from re-infection was identified using a bead-based cytokine immunoassay. Principal component analysis identified a Th-17-driven immune response during naïve infection.
Using the mouse model of haemoplasma infection to generate viable M. haemomuris organisms, in vitro cultivation was attempted in liquid culture and mice used to assess in vitro survival of M. haemomuris by inoculating infected culture media into naïve mice and subsequent monitoring for infection by qPCR. Mycoplasma haemomuris remained viable for 8 consecutive days of in vitro cultivation and replenishment of culture media with fresh mouse blood resulted in in vitro growth of M. haemomuris for four consecutive days.
The newly established mouse model of haemoplasma infection and first ever successful in vitro cultivation of a haemoplasma will help further haemoplasma research in a range of veterinary relevant species.

Date of Award	23 Jan 2020
Original language	English
Awarding Institution	University of Bristol
Supervisor	Christopher Helps (Supervisor), Mick Bailey (Supervisor), Severine Tasker (Supervisor), Darryl J Hill (Supervisor) & Toby G Knowles (Supervisor)