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. 2023 Apr 10;11(4):825.
doi: 10.3390/vaccines11040825.

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

Joan Pujols  1   2   3 , Elena Blázquez  1   4 , Joaquim Segalés  2   3   5 , Fernando Rodríguez  1   2   3 , Chia-Yu Chang  1   2   3 , Jordi Argilaguet  1   2   3 , Laia Bosch-Camós  1   2   3 , Rosa Rosell  2   6 , Lola Pailler-García  1   2   3 , Boris Gavrilov  7 , Joy Campbell  8 , Javier Polo  4   8
Affiliations

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

Joan Pujols et al. Vaccines (Basel). .

Abstract

This study aimed to evaluate the effects of feeding spray-dried porcine plasma (SDPP) on the protection afforded by the BA71∆CD2 African swine fever virus (ASFV) vaccine prototype. Two groups of pigs acclimated to diets without or with 8% SDPP were intranasally inoculated with 105 plaque-forming units (PFU) of live attenuated ASFV strain BA71∆CD2 and, three weeks later, left in direct contact with pigs infected with the pandemic Georgia 2007/01 ASFV strain. During the post-exposure (pe) period, 2/6 from the conventional diet group showed a transient peak rectal temperature >40.5 °C before day 20 pe, and some tissue samples collected at 20 d pe from 5/6 were PCR+ for ASFV, albeit showing Ct values much higher than Trojan pigs. Interestingly, the SDPP group did not show fever, neither PCR+ in blood nor rectal swab at any time pe, and none of the postmortem collected tissue samples were PCR+ for ASFV. Differential serum cytokine profiles among groups at vaccination, and a higher number of ASFV-specific IFNϒ-secreting T cells in pigs fed with SDPP soon after the Georgia 2007/01 encounter, confirmed the relevance of Th1-like responses in ASF protection. We believe that our result shows that nutritional interventions might contribute to improving future ASF vaccination strategies.

Keywords: ASFV; African swine fever; challenge; nutritional intervention; spray-dried porcine plasma; vaccine.

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Conflict of interest statement

The authors have read the journal’s policy, and the authors of this manuscript have the following competing interests: E.B. and J.P. (Javier Polo) are employed by APC Europe, S.L.U. Granollers, Spain; J.C. and J.P. (Javier Polo) are employed by APC LLC, Ankney, US. Both companies manufacture and sell spray-dried animal plasma; B.G. is employed by Huvepharma, Sofia, Bulgaria, a company that develops and commercializes vaccines for animal health. However, the companies had no role in the design of the study, in the collection, analysis, or interpretation of data, in the writing of the manuscript, or in the decision to publish the results. C.-Y.C., F.R., J.A., L.B.-C., J.P. (Joan Pujols), J.S., R.R., and L.P. declare no conflict of interest. This does not alter the authors’ adherence to all journal policies on sharing data and materials.

Figures

Figure 1
Figure 1
Schematic representation of the study design. Abbreviations: BSL3 = biosafety level 3; NS = Nasal swab; RS= rectal swab; pv = post-vaccination; pe = post-exposure; d = day; PBMCs = peripheral blood mononuclear cells.
Figure 2
Figure 2
Rectal temperature recorded individually after Georgia 2007/01 exposure of pigs intranasally inoculated with 105 PFU of BA71∆CD2. Data from pigs fed (A) the SDPP diet (SDPP1-7 pigs) or (B) the conventional diet (C1–C7 pigs). T1–T8 (dashed lines): Trojan pigs used for the direct contact challenge. In red color, animals that died before the end of the study.
Figure 3
Figure 3
Ct values obtained by qPCR using blood, nasal and rectal swabs from individual animals at different times post-Georgia 2007/01 exposure (pe). Data from pigs fed (A) the SDPP diet (SDPP1-7 pigs) or (B) the conventional diet (C1–C7 pigs). The higher the Ct values, the lower the ASFV load, with Ct values > 35 being considered negative (cut-off of the technique). Tables in orange show the average Ct values obtained in samples from Trojan pigs. Animals in red color died before the end of the experiment.
Figure 4
Figure 4
Ct values obtained by qPCR from different tissue samples of individual animals at the end of post-Georgia 2007/01 exposure (d20pe). Data from pigs (A) fed the SDPP diet (SDPP1-7 pigs) or (B) the conventional diet (C1–C7 pigs). The higher the Ct values, the lower the ASFV load, with Ct values > 35 being considered negative (cut-off of the technique). Tables in orange show the average Ct values obtained in samples from Trojan pigs. Animals in red color died before the end of the experiment. Abbreviations: Sub LN = Submaxillary lymph nodes; Retro LN = Retropharyngeal lymph nodes; Gastro LN = Gastro-hepatic lymph nodes.
Figure 5
Figure 5
ASFV-specific immune responses analyzed in BA71∆CD2-vaccinated pigs before and after Georgia 2007/01 challenge. ASFV-IgG (A) and IgA (B) antibodies from sera quantified by ELISA. Average values for SDPP-fed pigs (SDPP1-7) are shown as dashed lines, while solid lines represent average values for pigs fed the conventional diet (C1–C7). Standard deviation values are shown. (C) Number of ASFV-specific IFNγ-secreting T cells found at d9pe by ELISPOT in PBMCs upon in vitro stimulation with either the pandemic Georgia 2007/01 (white boxes) or the BA71∆CD2 vaccine (black boxes). * = p < 0.05; # = p < 0.1.
Figure 6
Figure 6
Serum concentrations of several cytokines quantified by Luminex after 24 days of diet acclimation (before immunization). * = p < 0.05; # = p < 0.1.
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