A new study has highlighted the early loss of immune cells in pigs infected with African Swine Fever virus (ASFV).
The rapid depletion of immune cells that are key to sensing and controlling infections in infected pigs may explain why vaccines remain elusive and the disease is almost always fatal.
African swine fever (ASF) is a highly contagious viral disease of pigs with fatality rates approaching 100 per cent. Since the emergence of the Georgia 2007/1 strain in 2007, the virus has spread across five continents, posing a severe threat to global pork production and food security.
Current control measures including mass culling and movement restrictions have failed to curtail its reach. Last November 2025, Spain confirmed its first outbreak of ASF since 1994, prompting a swift response by the country’s veterinary authorities.
Writing in Discovery Immunology, scientists at The Pirbright Institute explain how ASFV quickly disrupts immune responses during the earliest stages of infection. Using highly inbred Babraham pigs to reduce genetic variability, the team examined early virus spread and immune cell dynamics following infection through routes that closely mimic natural exposure.
Dr Priscilla Tng, from Pirbright’s African Swine Fever Vaccinology Group, said:
“The virus was detected in lymphoid tissues associated with the mouth and respiratory tract within one to three days of infection before spreading systemically. By the time clinical signs such as fever and lethargy appeared, often within a week, critical immune cell populations were already being depleted”.
The researchers observed widespread loss and dysfunction of immune cells essential for mounting effective defences, including T cells, dendritic cells, natural killer (NK) cells and macrophages.
“Many of these cells showed signs of apoptosis, or programmed cell death, suggesting that the virus not only infects immune cells directly but also triggers their destruction,” added Dr Tng.
Notably, the study showed the collapse of the ‘innate-adaptive interface’ - the coordinated interaction between early, non-specific immune responses and the longer-lasting adaptive response. Cells that normally connect these two arms of immunity, such as dendritic cells and gamma-delta (γδ) T cells, were rapidly depleted or rendered dysfunctional.
“This early loss of key immune cell populations helps explain why pigs infected with highly virulent ASFV rarely survive” added Dr Tng.
The findings suggest the speed and breadth of immune disruption caused by virulent ASFV strains may be a defining feature of acute disease. Understanding which immune cells are targeted first - and how this varies between viral strains - could hold the key to the design of future vaccines.
“Our findings highlight the need to investigate the innate-adaptive axis further with different ASFV isolates of varying virulence to determine if this immune imbalance is a defining feature of acute ASFV infection,” conclude the Pirbright researchers.
For further information about The Pirbright Institute’s work on African Swine Fever vaccinology, visit our web pages.
Read the paper:
Priscilla Y L Tng, Laila Al-Adwani, Lynnette Goatley, Raquel Portugal, Anusyah Rathakrishnan, Christopher L Netherton, Early disruption of the innate-adaptive immune axis in vivo after infection with virulent Georgia 2007/1 ASFV, Discovery Immunology, Volume 4, Issue 1, 2025, kyaf014.