Comparative pathogenesis of peste des petits ruminants virus strains of difference virulence

Abstract

Peste des petits ruminants (PPR) is an acute disease of small ruminants caused by a morbillivirus. Clinical observation of the disease in the field revealed that several species of small ruminants are affected to varying degrees. This difference in disease-related effects could depend either on the host or on the virulence of the virus strain. A previous study highlighted the difference in virulence between two strains of PPRV used to infect Saanen goats. For this breed, PPRV Morocco 2008 strain (MA08) was highly virulent while PPRV Côte d’Ivoire 1989 (IC89) strain induced mild disease. Experimental studies generally based on healthy and young animals do not permit exploration of the natural variability of the host susceptibility to PPRV. Therefore, building on the previous study on Saanen goats, the current study focussed on this breed of goat and used commercially available animals with an unknown history of infection with other pathogens. Results confirmed the previous disease pattern for PPRV IC89 and MA08 strains. Viral RNA detection, macroscopic and histological lesions were stronger for the highly virulent MA08 strain. We show here for the first time that viral RNA can be detected in the tissues of vaccinated animals. Viral RNA was also detected for the first time in serum samples, which is in agreement with the role of circulating immune cells in transporting the virus into host target organs. Thus, this study provides insight into the pathogenesis of strains of different virulence of PPRV and will help to better understand the onset of the disease.

Pathogenesis of wild-type- and vaccine-based recombinant peste des petits ruminants virus (PPRV) expressing EGFP in experimentally infected domestic goats

“…Transient lymphopaenia is induced by infection of immune cells via its receptor CD150 (SLAM). Previously, PPRV-specific RNA has been detected in whole blood, WBC or serum of experimentally inoculated goats that mostly peaked at the end of the first week post-inoculation [17,18,20,21,25]. In our study, we quantified the percentage of infected lymphocytes based on the expression of EGFP and confirmed peak infection at 7-8 dpi.…”

“…However, an early induction of PPRV-specific antibodies at the end of the first week post-infection does not necessarily prevent the animals from dying after a PPRV infection [16]. We measured an early humoral response in both study groups; the response was slightly faster in rPPRV/Tbilisi-EGFP-inoculated animals as compared to vaccine virus-inoculated animals, confirming observations of a faster and stronger immune response in animals that have been inoculated with a more virulent PPRV strain than with a less severe or vaccine strain [16,25]. In contrast, Rajak et al observed a delayed onset of PPRV-specific and bystander antibodies in goats experiencing severe clinical symptoms, suggesting that the immune system may be impaired during PPRV infection [15].…”

“…We and others used body temperature and overall clinical signs as a measure for severity of disease [19,21,22,25,26]. PPR symptoms can range from mild to severe and a PPR infection is often lethal.…”

“…Despite its recognized importance, little is known about the pathogenesis of virulent PPRV strains. In the last 20 years, a number of studies have evaluated PPRV isolates in diverse goat or sheep species, using various routes of inoculation and different timings [4,[15][16][17][18][19][20][21][22][23][24][25][26]. Those suggest that disease severity is linked to the PPRV strain [25,26].…”

“…In the last 20 years, a number of studies have evaluated PPRV isolates in diverse goat or sheep species, using various routes of inoculation and different timings [4,[15][16][17][18][19][20][21][22][23][24][25][26]. Those suggest that disease severity is linked to the PPRV strain [25,26]. Moreover, PPR disease seems more severe in goats than in sheep, and more severe in young animals.…”