Massive plasmablast response elicited in the acute phase of hantavirus pulmonary syndrome

Beside its key diagnostic value, the humoral immune response is thought to play a protective role in Hantavirus Pulmonary Syndrome (HPS). However, little is known about the cell source of these antibodies during ongoing human infection. Herein we characterized B cell subsets circulating in Andes virus-infected patients. A notable potent plasmablast (PB) response that increased 100-fold over the baseline levels was observed around one week after the onset of symptoms. These PB present a CD3negCD19lowCD20negCD38hiCD27hiCD138+/-IgA+/- surface phenotype together with the presence of cytoplasmic functional immunoglobulins. They are large lymphocytes (lymphoblasts) morphologically coincident with the “immunoblast-like” cells that have been previously described during blood cytology exam of hantavirus-infected patients. Immunoreactivity analysis of white blood cell lysates suggests that a fraction of circulating PB is virus-specific but we also observed a significant increase of reactivity against virus-unrelated antigens which suggests a possible bystander effect by polyclonal B cell activation. The presence of this large and transient PB response raises the question as to whether these cells might have a protective or pathological role during the ongoing HPS and suggest their practical application as a diagnostic/prognostic biomarker. This article is protected by copyright. All rights reserved.