Foetal Immune Response Activation and High Replication Rate during Generation of Classical Swine Fever Congenital Infection.

José Alejandro Bohórquez,Sara Muñoz-González,Marta Pérez-Simó,Rosa Rosell,Mariano Domingo,Iván Muñoz,Llilianne Ganges,Liani Coronado

doi:10.3390/pathogens9040285

Abstract

Classical swine fever virus (CSFV) induces trans-placental transmission and congenital viral persistence; however, the available information is not updated. Three groups of sows were infected at mid-gestation with either a high, moderate or low virulence CSFV strains. Foetuses from sows infected with high or low virulence strain were obtained before delivery and piglets from sows infected with the moderate virulence strain were studied for 32 days after birth. The low virulence strain generated lower CSFV RNA load and the lowest proportion of trans-placental transmission. Severe lesions and mummifications were observed in foetuses infected with the high virulence strain. Sows infected with the moderately virulence strain showed stillbirths and mummifications, one of them delivered live piglets, all CSFV persistently infected. Efficient trans-placental transmission was detected in sows infected with the high and moderate virulence strain. The trans-placental transmission occurred before the onset of antibody response, which started at 14 days after infection in these sows and was influenced by replication efficacy of the infecting strain. Fast and solid immunity after sow vaccination is required for prevention of congenital viral persistence. An increase in the CD8+ T-cell subset and IFN-alpha response was found in viremic foetuses, or in those that showed higher viral replication in tissue, showing the CSFV recognition capacity by the foetal immune system after trans-placental infection.

Highlights

Classical swine fever virus (CSFV) is one of the most relevant viruses in the Pestivirus genus, being the causative agent of classical swine fever (CSF), a highly impactful disease for the porcine industry worldwide [1]
Clinical Evaluation of Sows Infected with Pinar del Rio (PdR) vs. Margarita CSFV Strains
In the first experiment, aiming to determine the capacity of CSFV strains of different virulence levels to induce trans-placental infection, two groups of pregnant sows were inoculated with CSFV at 74 days of gestation

Summary

Introduction

Classical swine fever virus (CSFV) is one of the most relevant viruses in the Pestivirus genus, being the causative agent of classical swine fever (CSF), a highly impactful disease for the porcine industry worldwide [1]. Pathogens 2020, 9, 285 sows occurs between 50 and 90 days of gestation [1,2,3,4,5] Piglets that develop this form of infection are born infected, showing high viral replication and shedding in the absence of specific antibody response [3,4,7]. This type of viral persistence has been explained by the immunotolerance mechanism, due to a lack of CSFV recognition by the immature immune system of the foetus [5].

Objectives

Methods

Results

Conclusion