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. 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 1 week after the onset of symptoms. These PB present a CD3neg CD19low CD20neg CD38hi CD27hi CD138+/- 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 examinations of hantavirus-infected patients. Immunoreactivity analysis of white blood cell lysates suggests that some circulating PB are 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 hantavirus pulmonary syndrome and suggest their practical application as a diagnostic/prognostic biomarker.

"Plasma cell hepatitis" in liver allografts: identification and characterization of an IgG4-rich cohort.

Plasma cell hepatitis (PCH), also known as "de novo autoimmune" hepatitis, is an increasingly recognized, but suboptimally named and poorly understood, category of late allograft dysfunction strongly resembling autoimmune hepatitis (AIH): They share plasma-cell-rich necro-inflammatory activity on biopsy, autoantibodies and steroid responsiveness, but overlap with rejection is problematic. A retrospective study of clinical, serological, histopathological and IgG4 immunohistological features of PCH (n = 20) in liver allograft recipients, native liver AIH (n = 19) and plasma-cell-rich renal allograft rejection (n = 20) showed: (1) high frequency (44%) of HLA-DR15; (2) less female predominance (p = 0.03) and (3) n = 9/20 PCH recipients showed >25 IgG4+ plasma cells/high-power field (IgG4+ PCH) versus AIH (n = 1/19, p = 0.008) or plasma-cell-rich kidney rejection (n = 2/20, p = 0.03). The IgG4+ PCH (n = 9) subgroup showed lower alanine transaminase (ALT) (p < 0.01) and aspartate transaminase (AST) (p < 0.05) at index biopsy but (a) higher plasma cell number/percentage, (b) more aggressive-appearing portal/periportal and perivenular necro-inflammatory activity and (c) more severe portal/periportal fibrosis than IgG4- PCH (n = 11). Significant demographic, histopathologic and plasma cell phenotype differences between PCH and AIH suggest distinct pathogenic mechanisms for at least the IgG4+ PCH subgroup likely representing an overlap between allo- and auto-immunity. IgG4+ PCH was associated with fibrosis, but also highly responsive to increased immunosuppression.

Association between magnitude of the virus-specific plasmablast response and disease severity in dengue patients.

Dengue is a globally expanding disease caused by infection with dengue virus (DENV) that ranges from febrile illness to acute disease with serious complications. Secondary infection predisposes individuals to more severe disease, and B lymphocytes may play a role in this phenomenon through production of Ab that enhance infection. To better define the acute B cell response during dengue, we analyzed peripheral B cells from an adult Brazilian hospital cohort with primary and secondary DENV infections of varying clinical severity. Circulating B cells in dengue patients were proliferating, activated, and apoptotic relative to individuals with other febrile illnesses. Severe secondary DENV infection was associated with extraordinary peak plasmablast frequencies between 4 and 7 d of illness, averaging 46% and reaching 87% of B cells, significantly greater than those seen in mild illness or primary infections. On average >70% of IgG-secreting cells in individuals with severe secondary DENV infection were DENV specific. Plasmablasts produced Ab that cross-reacted with heterotypic DENV serotypes, but with a 3-fold greater reactivity to DENV-3, the infecting serotype. Plasmablast frequency did not correlate with acute serum-neutralizing Ab titers to any DENV serotype regardless of severity of disease. These findings indicate that massive expansion of DENV-specific and serotype cross-reactive plasmablasts occurs in acute secondary DENV infection of adults in Brazil, which is associated with increasing disease severity.

Oral ulcers in HIV-positive Peruvian patients: an immunohistochemical and in situ hybridization study.

BACKGROUND: This study describes the histopathological, immunohistochemical (IHC) and in situ hybridization (ISH) data of 25 cases of oral ulcers in HIV-positive patients, with clinical and microscopical features similar to ulcers not otherwise specified (NOS)/necrotizing ulcerative stomatitis (NUS). METHODS: Sex, age and clinical history were obtained from the clinical records. Histological analysis for H&E, Gomori-Grocott and Ziehl-Neelsen stains, IHC analysis to detect infectious agents and to characterize inflammatory cellular infiltrate, and ISH for cytomegalovirus (CMV) and EBER1/2 were performed. RESULTS: Twenty-one patients were men and four were women (mean age of 34.6 years). The tongue was preferentially affected. Microscopically, the lesions showed extensive necrosis, leukocytoclasia, vasculitis with luminal fibrin clots and an intense inflammatory cellular infiltrate predominated by CD68(+) atypical large cells, normal-sized and crescent-shaped nuclei macrophages, interspersed by CD8(+) T lymphocytes. Mast cells were also observed in all samples studied. CD4(+) T lymphocytes, CD20(+) B lymphocytes and VS38c(+) plasma cells were practically absent. CMV and EBER1/2 were identified in scarce cells of 3 and 16 of 25 cases respectively. CONCLUSION: These results show that CD68(+) macrophages, followed by CD8(+) T lymphocytes, were the predominant inflammatory cells, indicating they are relevant to the pathogenesis of the ulcers, possibly reflecting an abnormal immune response in the oral mucosa. The clinicopathological and immunoprofile features of the present cases are similar to NOS ulcers/NUS in HIV-positive patients.