Abstract Multiple myeloma (MM), its preceding stages, smoldering myeloma (SMM), and monoclonal gammopathy of undetermined significance (MGUS) are characterized by the presence of a mutated plasmacytic clone that produces large amounts of a single immunoglobulin (Ig), called monoclonal Ig. Over the years, the size of the plasmacytic clone and the quantity of monoclonal Ig increase when MGUS progresses toward SMM, then to overt MM. Thus, monoclonal Ig is a major marker of disease evolution. Yet its role in MGUS, SMM, and MM remains poorly understood, and the monoclonal Ig is not a target in the treatment of MM.
Reasoning that most Ig's are produced to fight infections, we designed a new assay, called the multiplexed infectious antigen micro-array (MIAA) assay, which allows determining whether purified monoclonal Igs from MGUS, SMM, or MM patients target infectious pathogens. Using the MIAA assay, we were able to show that >50% of MGUS patients, >40% of SMM patients, and 30% of MM patients present with a monoclonal Ig that specifically recognizes a pathogen that causes chronic infection, notably Hepatitis C and B viruses (HCV, HBV), Helicobacter pylori and Herpesviruses. MGUS and MM disease in these patients is likely initiated by infection since anti-viral therapy can lead to the disappearance of antigenic stimulation, control of the plasmacytic clone, and reduced or suppressed production of the monoclonal Ig, as demonstrated recently for MM patients presenting with a monoclonal Ig specific for HCV or HBV (Front Immunol 2022, Haematologica 2023).
In addition, the PEPperCHIP® Infectious Disease Epitope Microarray was used to identify sequences of Enterovirus VP1 proteins recognized by ~7% purified monoclonal Igs. In summary, this presentation describes results obtained using the MIAA assay or PEPperCHIP® Microarrays, to identify targets of monoclonal Ig's, and the importance and interest for patients of treatments that reduce or suppress the target of their monoclonal Ig, when the monoclonal Ig reacts against a treatable infectious pathogen.
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