A B lymphocyte mitogen is a Brucella abortus virulence factor required for persistent infection

Area of Science:

• Immunology
• Microbiology
• Molecular Biology

Background:

• Chronic infections by microbial pathogens often involve immune evasion strategies.
• Brucellosis, caused by Brucella abortus, can become a lifelong chronic infection if untreated.
• Mechanisms by which pathogens establish chronic infections remain largely unknown.

Purpose of the Study:

• To identify genes in Brucella abortus involved in modulating the host immune response.
• To investigate the role of the identified gene, prpA, in the pathogenesis of Brucellosis.
• To understand how Brucella establishes chronic infections through immune modulation.

Main Methods:

• Identification and characterization of the Brucella abortus prpA gene.
• Analysis of PrpA's effect on B lymphocyte activation and cytokine secretion (IL-10).
• Construction and infection studies of a B. abortus-prpA mutant in a mouse model.

Main Results:

• The prpA gene encodes a proline-racemase protein that induces polyclonal B lymphocyte activation.
• PrpA stimulation of splenocytes leads to increased Interleukin-10 (IL-10) secretion.
• Mice infected with B. abortus showed transient splenocyte unresponsiveness, which was absent in mice infected with the prpA mutant.
• The B. abortus-prpA mutant exhibited a reduced ability to establish chronic infection in mice.

Conclusions:

• The Brucella abortus prpA gene product acts as a B cell polyclonal activator, contributing to immune suppression.
• Early, transient immune nonresponsiveness induced by PrpA is crucial for establishing chronic Brucellosis.
• Targeting PrpA may offer a strategy to combat chronic Brucellosis infections.