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

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.

Decrypting the Origin and Pathogenesis in Pregnant Ewes of a New Ovine Pestivirus Closely Related to Classical Swine Fever Virus

“…The high capacity to generate trans-placental transmission, as well as the replication rate detected in the OVPV-infected animals from the present study, suggest that this isolate may be of moderate virulence [37,38]. However, further studies will provide insight into the virulence of OVPV in lambs, taking into account that young animals are highly susceptible to Pestivirus infections [11,39].…”

Serodynamic Analysis of the Piglets Born from Sows Vaccinated with Modified Live Vaccine or E2 Subunit Vaccine for Classical Swine Fever

“…A low CD4/CD8 ratio has been observed in the peripheral blood mononuclear cells of infected fetuses and piglets challenged with either high- or low-virulence CSFV strains. A low CD4/CD8 ratio indicates dysregulation of the immune response [ 3 ]. During CSFV infection, the clinical signs mainly depend on the ages of pigs and the virulence of the viral strains.…”

“…Transplacental transmission of CSFV occurred before the onset of the antibody response when sows were challenged with either high- or low-virulence CSFV strains. Therefore, rapid and solid immunity after sow vaccination is required for the prevention of congenital viral persistence [ 3 ]. In Taiwan, CSFV MLV has been used since the 1950s and proven to be sufficiently protective.…”

Classical Swine Fever: A Truly Classical Swine Disease

“…At this difficult period, Pathogens has the timely honor to present a Special Issue on Classical Swine Fever collecting 14 publications. Readers can find that perhaps few swine diseases have such a comparable ancient history as CSF [ 1 ], and few have such a versatile capability in affecting so many body systems [ 1 ] via horizontal [ 2 , 3 ] as well as vertical [ 4 , 5 ] transmissions. And few have so many clinical forms expressed, ranging from acute to chronic, atypical to congenital, etc.…”

“…And few have so many clinical forms expressed, ranging from acute to chronic, atypical to congenital, etc. [ 1 , 4 ].…”