Antioxidant Treatment Regulates the Humoral Immune Response during Acute Viral Infection

Abstract

Generation of reactive oxygen intermediates (ROI) following antigen receptor ligation is critical to promote cellular responses. However, the effect of antioxidant treatment on humoral immunity during a viral infection was unknown. Mice were infected with lymphocytic choriomeningitis virus (LCMV) and treated with Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), a superoxide dismutase mimetic, from days 0 to 8 postinfection. On day 8, at the peak of the splenic response in vehicle-treated mice, virus-specific IgM and IgG antibody-secreting cells (ASC) were decreased 22-and 457-fold in MnTBAP-treated animals. By day 38, LCMV-specific IgG ASC were decreased 5-fold in the bone marrow of drug-treated mice, and virus-specific antibodies were of lower affinity. Interestingly, antioxidant treatment had no effect on the number of LCMV-specific IgG memory B cells. In addition to decreases in ASC, MnTBAP treatment decreased the number of functional virus-specific CD4 ؉ T cells. The decreased numbers of ASC observed on day 8 in drug-treated mice were due to a combination of Bim-mediated cell death and decreased proliferation. Together, these data demonstrate that ROI regulate antiviral ASC expansion and have important implications for understanding the effects of antioxidants on humoral immunity during infection and immunization.A ntibodies are a critical component of the immune system's defense to infectious microorganisms. In order to initiate an antibody response to a pathogen, naïve B cells must first be activated through recognition of antigen by the B cell receptor (BCR). Following antigen stimulation, activated B cells enlist cognate CD4 ϩ T cell help to stimulate clonal expansion (1). Upon activation and proliferation, B cells embark on two distinct differentiation pathways (2). First, the initial production of antibody to a pathogen is accomplished through the differentiation of activated B cells into extrafollicular plasmablasts (3). These short-lived cells are essential in generating low-affinity antibodies early during the infection. However, to generate long-lived humoral immunity, activated B cells must migrate to the germinal center, undergo affinity maturation by somatic hypermutation, and undergo isotype switching to produce memory B cells or antibody-secreting plasma cells (ASC) (3). Memory B cells are long-lived and rapidly respond to pathogen re-encounter by proliferating and differentiating into ASC (4). High-affinity, long-lived ASC migrate to the bone marrow, where they continuously secrete antibody and persist for a year or more in mice (5) and decades in humans (6). Therefore, determining the factors that modulate these pathways is critical not only for understanding the generation and maintenance of serological memory but also for optimizing vaccines and therapeutics for autoimmune disorders.Following antigen receptor ligation, reactive oxygen intermediates (ROI) are generated and required for B cell function (7-9). Previous work has demonstrated that antioxidant treatment decreased lipo...

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