Chronic Infection, a Neglected Cause Of Development Of Monoclonal Gammopathy Of Undetermined Significance (MGUS) and Myeloma

Chronic infection can lead to B-cell malignancy via the direct transformation of infected B-lymphocytes or indirectly via cell transformation consecutive to chronic antigen-driven stimulation; the two mechanisms may occur simultaneously (Seifert et al. Methods Mol Biol 2013; 971:1; Hermouet et al. New Engl J Med 2003; 348:178; de Martel et al. Lancet Oncol 2012). Numerous studies have established that viruses (Epstein-Barr virus (EBV), human herpes virus 8, hepatitis C virus (HCV)) or bacteria (H. pylori) can induce lymphoma and chronic lymphocytic leukemia (CLL). In contrast, the role of chronic infection in the pathogenesis of myeloma is rarely investigated. Yet monoclonal immunoglobulins (mc Ig) that arise in HCV-positive myeloma patients typically target the virus (Bigot-Corbel et al. Blood 2008). Thus HCV infection may lead to monoclonal gammopathy of undetermined significance (MGUS) and eventually, myeloma. The present study shows that mc Ig also frequently target EBV, and less frequently, H. pylori.

In order to study the specificity of mc Ig, we designed a new assay based on a multiplexed infectious protein (MIP) microarray that combines representative panels of epitopes of a panel of germs that included HCV, EBV, H. pylori and 5 other germs, spotted in triplicate on nitrocellulose-coated slides (Feron et al. Anal Biochem 2013; 433:202). Slides were first incubated with either serum or purified mc Ig, then with an infrared dyed (IRD)-labeled secondary antibody, and fluorescence signals were detected and quantified.

The specificity of purified mc Ig from 101 patients diagnosed with MGUS (n=34) or myeloma (n=67) was analysed using the 8-germ MIP microarray assay. We found that 20.6% of MGUS and 24.2% of myeloma patients (p=0.810) presented with a mc Ig that was specific for an antigen from HCV, EBV, or H. pylori. Indeed for 23/101 patients (22.7%), the purified mc Ig recognized HCV (n=10), EBV (n=11) or H. pylori (n=2). In contrast, none of the 101 mc Ig studied targeted CMV, a virus against which a majority of individuals possess antibodies.

Interestingly, HCV- and EBV-specific mc Ig all targeted a single antigen. For 10/11 (91%) of the HCV-positive patients, the mc Ig was directed against HCV core protein. Regarding EBV-positive patients, the mc Ig specifically recognized EBV in 23% cases (11/59 tested), and in all cases the mc Ig targeted Epstein Barr nuclear antigen (EBNA). For 8% (2/25 tested) of H. pylori-positive patients, the mc Ig targeted different antigens of H. Pylori. The specificity of each mc Ig was confirmed by Western Blot analysis.

Altogether, 22.7% of the 101 MGUS and myeloma patients examined presented a mc Ig specific for HCV, EBV or H. pylori. Thus beside lymphoma and CLL, chronic infection by these 3 germs can also induce MGUS and eventually, trigger the pathogenic processes that lead to myeloma. Efforts should be made to identify the subsets of patients with mc Ig specific for HCV, EBV and H. pylori, preferably at the MGUS stage, as anti-infection treatment is expected to cure MGUS and prevent progression toward myeloma.

No relevant conflicts of interest to declare.