Immune-related gene expression profiles in field-derived African swine fever virus (ASFV)-positive whole blood samples in Luzon, Philippines

Abstract

African swine fever (ASF) is a highly contagious and lethal hemorrhagic disease of pigs caused by the double-stranded DNA virus African swine fever virus (ASFV). Infection induces excessive immunological activation, subsequently resulting in immune suppression, which alters the expression of small signaling proteins known as cytokines. This study quantified the relative gene expression of innate, T-helper, interferon-associated, and chemokine genes in ASFV-positive whole blood samples collected from naturally infected pigs through routine surveillance in Luzon, Philippines. Samples were obtained from two geographically and temporally distinct field sampling groups: North Luzon (NL; October 2023) and South Luzon (SL; July 2024). Relative gene expression was determined using the 2-ΔΔCT method, with ASF-negative samples serving as the reference baseline. Exploratory analyses showed variation in immune gene expression among ASFV-positive samples, with NL samples generally exhibiting higher expression of innate and T-helper-associated genes than SL samples. In contrast, both groups showed increased expression of TNF-α, CCL2, CCL3L1, and CXCL10. Multivariate analyses revealed overlapping yet distinguishable expression patterns between groups, along with coordinated expression of innate, T-helper-associated, and chemokine gene clusters. These results suggest that naturally infected ASFV-positive pigs may exhibit heterogeneous immune response states characterized by variable innate and T-helper-associated gene expression, while inflammatory and chemokine signaling, particularly involving TNF-α, CCL2, CCL3L1, and CXCL10, is consistently upregulated. These preliminary findings provide initial insights into immune responses during natural ASFV infection and may guide future field studies involving larger, well-characterized field populations.