Intestinal microbiota influences susceptibility to African swine fever

Faecal microbiota transplantation from African warthog to pig improved protection against an attenuated strain of African swine fever virus (ASFV), coinciding with a potent stimulation of mucosal immunity in transplanted animals. This is the conclusion of a study led by researchers from the Centre de Recerca en Sanitat Animal (CReSA) from the Institut de Recerca i Tecnologia Agroalimentàries (IRTA), with researchers from the Barcelona Zoo Biological Bank and the Department of Animal Health and Anatomy of the Autonomous University of Barcelona (UAB), and other national and international collaborators.

The results have been published in Scientific Reports and form part of Jinya Zhang’s doctoral thesis, led by researchers Flor Correa and Fernando Rodríguez, from IRTA-CReSA, and Jorge Martínez, a UAB researcher at the IRTA-CReSA.

The researchers found an increase in secretory immunoglobulins (IgA) in pigs transplanted with warthog faeces, compared to that observed in non-transplanted control animals or animals transplanted with pig faeces. These IgAs produced by plasma cells originally resident in mucous membranes play a key role not only in mucosal immunity but also in the regulation of innate and adaptive immunity, which could explain protection against infection by an attenuated strain of ASFV. IgAs can promote the expression of IFN-γ through a mechanism mediated by TNF-α, cytokines known to play important roles in protection against ASFV.

While serious for domestic pigs and European wild boar, ASFV circulates subclinically in African warthogs (Phacochoerus africanus) and other species of African wild pigs (Potamochoerus porcus).

Along with genetic differences, other factors could be involved in the differential susceptibility to ASF observed between Eurasian suids (Sus scrofa) and African warthogs.

Previous results obtained at IRTA-CReSA, showed that domestic pigs raised in facilities free of specific pathogens (SPF) were extremely susceptible to highly attenuated virus strains, while these strains were harmless to genetically identical pigs raised on conventional farms. The researchers worked with the hypothesis that the microbiota could play a role, along with genetics, in resistance to ASFV.

Weaned piglets were transplanted with faecal microbiota from African warthogs or domestic pigs, and subsequently challenged with a virulent or attenuated strain of ASF virus.

When the virulent strain (E75) was intramuscularly inoculated, no differences were observed in any of the cases. However, a very significant reduction in serum virus, nasal spread of the virus, and clinical signs were observed when pigs transplanted with African wild boar faeces were challenged intramuscularly with E75CV1, an attenuated strain of ASFV, and compared to pigs transplanted with domestic pig faeces. “The next step will be to identify the individual components of this microbiota and characterize its protective potential against the ASF virus in order to use them as probiotics,” said Fernando Rodríguez.

Article: Zhang, J., Rodríguez, F., Navas, M. J., Costa-Hurtado, M., Almagro, V., Bosch-Camós, L., López, E., Cuadrado, R., Accensi, F., Pina-Pedrero, S., Martínez, J., Correa-Fiz, F. (2020). Fecal microbiota transplantation from warthog to pig confirms the influence of the gut microbiota on African swine fever susceptibility. Scientific Reports, 10(1), 17605, doi: 10.1038/s41598-020-74651-3


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