The researchers in this study utilized transcriptome analysis to assess the impacts of Escherichia coli (E. coli) contamination on the immune responses triggered by various proteins of African horse sickness virus serotype 4 (AHSV4) in horse peripheral blood cells.

Exploration of Immune Responses

• The study firstly aimed to understand the primary and secondary immune responses generated by horse peripheral blood mononuclear cells (PBMC) when stimulated with individual recombinant proteins of AHSV serotype 4.
• The AHSV4 proteins examined in the research, known as rAHSV4 proteins, were expressed in E. coli for the experiments.
• Through the use of transcriptome analysis, a tool that allows for the examination of gene expression, the scientists were able to evaluate the changes that occurred in the immune response due to the stimulation by these proteins.

Impact of E. coli Contamination

• The research found that the contamination products from E. coli greatly influenced the innate and humoral immune responses.
• The innate immune response is the body’s first line of defense against pathogens, functioning immediately or within hours of an antigen’s appearance in the body. The humoral immune response, on the other hand, refers to antibody production and the accessory processes that accompany it, such as activation of B cells and helper T cells.
• The researchers assessed the specific influence of these E. coli contamination products on the immune response, to understand the full extent of their impact.

Pro-inflammatory Responses and Endotoxin Tolerance

• The data demonstrated that the amplification effects of synergistic pattern recognition receptors (PRRs), tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) signalling initiated strong pro-inflammatory responses.
• These pro-inflammatory reactions were overwhelming and not adequately managed by anti-inflammatory cytokines and regulators, suggesting a detrimental effect on the body’s immune balance.
• The study also found that lipopolysaccharide (LPS), a molecule found in the outer membrane of Gram-negative bacteria like E. coli, could activate ‘innate-like’ B cells and induce polyreactive (natural) antibody responses. This could potentially contribute to a state of endotoxin tolerance where the body develops a diminished response to endotoxins (harmful substances released when bacteria die and their cell walls disintegrate).