Feeding Spray-Dried Porcine Plasma to Pigs Reduces African Swine Fever Virus Load in Infected Pigs and Delays Virus Transmission. Study 1

Abstract

The objective of this study was to evaluate the potential benefits of feeding spray-dried porcine plasma (SDPP) to pigs infected with African swine fever virus (ASFV). Two groups of twelve weaned pigs each were fed with CONVENTIONAL or 8% SDPP enriched diets. Two pigs (trojans)/group) were injected intramuscularly with the pandemic ASFV (Georgia 2007/01) and comingled with the rest of the pigs (1:5 trojan:naïve ratio) to simulate a natural route of transmission. Trojans developed ASF and died within the first week after inoculation but contact pigs did not develop ASF, viremia or seroconversion. Therefore, three more trojans per group were introduced to optimize the ASFV transmission (1:2 trojan:naïve ratio). Blood, nasal and rectal swabs were weekly harvested and at end of the study, ASFV-target organs collected. After the second exposure, rectal temperature of conventionally fed contact pigs increased >40.5˚C while fever was delayed in the SDPP contact pigs. Additionally, PCR Ct values in blood, secretions and tissue samples were significantly lower (P<0.05) for CONVENTIONAL compared to SDPP contact pigs. Under these study conditions, contact exposed pigs fed SDPP had delayed ASFV transmission and reduced virus load, likely by enhanced specific T-cell priming after the first ASFV-exposure.

Feeding Spray-Dried Porcine Plasma to Pigs Improves the Protection Afforded by The African Swine Fever Virus (ASFV) BA71∆CD2 Vaccine Prototype Against Experimental Challenge with The Pandemic ASFV. Study 2.

“…The fact that virusspecific T-cells recognize both the BA71∆CD2 vaccine and the pandemic virus, confirms the induction of T-cells capable to recognize genotypes I and II, currently circulating in China [2]. These results and the corresponding peak of serum TNFα early after Georgia 2007/01 exposure of SDPP fed pigs is consistent with the relevance of vaccine induced IFNγ+TNFα+ polyfunctional memory Th1-cells in ASFV protection [14] and in delayed transmission of ASFV in SDPP fed pigs [20]. Also in this line, the peak of the Th1 cytokine IL12 [32] in plasma at 7dpv also suggest the SDPP-driven enhancement of the vaccineinduced Th1 response.…”

“…For this study, 24 4-week-old Landrace x Large White male pigs were used. Pigs were randomly divided into two separate groups at IRTA-Monells, animal facility and acclimated to their assigned diet (Table 1), as described by Blazquez et al [20].…”

“…Although the modes of action of SDP are not completely known, it has been shown to modulate the efficiency of the immune system [19]. Based on the demonstrated capability of SDPP feeding to accelerate the induction of specific Th1-like responses and to delay experimental ASFV transmission and disease progression [20] (back-to-back submitted manuscript), the objective of this study was to evaluate the effects of feeding SDPP on the protection afforded by the BA71∆CD2 vaccine prototype.…”