Browsing by Subject "Antibody Formation"
Now showing 1 - 18 of 18
Results Per Page
Sort Options
Item Open Access A Prevalent Focused Human Antibody Response to the Influenza Virus Hemagglutinin Head Interface.(mBio, 2021-06) McCarthy, Kevin R; Lee, Jiwon; Watanabe, Akiko; Kuraoka, Masayuki; Robinson-McCarthy, Lindsey R; Georgiou, George; Kelsoe, Garnett; Harrison, Stephen CNovel animal influenza viruses emerge, initiate pandemics, and become endemic seasonal variants that have evolved to escape from prevalent herd immunity. These processes often outpace vaccine-elicited protection. Focusing immune responses on conserved epitopes may impart durable immunity. We describe a focused, protective antibody response, abundant in memory and serum repertoires, to a conserved region at the influenza virus hemagglutinin (HA) head interface. Structures of 11 examples, 8 reported here, from seven human donors demonstrate the convergence of responses on a single epitope. The 11 are genetically diverse, with one class having a common, IGκV1-39, light chain. All of the antibodies bind HAs from multiple serotypes. The lack of apparent genetic restriction and potential for elicitation by more than one serotype may explain their abundance. We define the head interface as a major target of broadly protective antibodies with the potential to influence the outcomes of influenza virus infection. IMPORTANCE The rapid appearance of mutations in circulating human influenza viruses and selection for escape from herd immunity require prediction of likely variants for an annual updating of influenza vaccines. The identification of human antibodies that recognize conserved surfaces on the influenza virus hemagglutinin (HA) has prompted efforts to design immunogens that might selectively elicit such antibodies. The recent discovery of a widely prevalent antibody response to the conserved interface between two HA "heads" (the globular, receptor-binding domains at the apex of the spike-like trimer) has added a new target for these efforts. We report structures of eight such antibodies, bound with HA heads, and compare them with each other and with three others previously described. Although genetically diverse, they all converge on a common binding site. The analysis here can guide immunogen design for preclinical trials.Item Open Access Adjuvant Injections Altered the Ileal and Fecal Microbiota Differently with Changes in Immunoglobulin Isotypes and Antimycobacterial Antibody Responses.(International journal of molecular sciences, 2023-02) Khadka, Sundar; Omura, Seiichi; Sato, Fumitaka; Tsunoda, IkuoAlterations in the gut microbiota, "dysbiosis," have been reported in autoimmune diseases, including multiple sclerosis (MS), and their animal models. Although the animal models were induced by injections of autoantigens with adjuvants, including complete Freund's adjuvant (CFA) and pertussis toxin (PT), the effects of adjuvant injections on the microbiota are largely unknown. We aimed to clarify whether adjuvant injections could affect the microbiota in the ileum and feces. Using 16S rRNA sequencing, we found decreased alpha diversities of the gut microbiota in mice injected with CFA and PT, compared with naïve mice. Overall, microbial profiles visualized by principal component analysis demonstrated dysbiosis in feces, but not in the ileum, of adjuvant-injected mice, where the genera Lachnospiraceae NK4A136 group and Alistipes contributed to dysbiosis. When we compared the relative abundances of individual bacteria, we found changes in 16 bacterial genera in feces and seven genera in the ileum of adjuvant-injected mice, in which increased serum levels of antibody against mycobacteria (a component of CFA) and total IgG2c were correlated with the genus Facklamia. On the other hand, increased IgG1 and IgA concentrations were correlated with the genus Atopostipes. Therefore, adjuvant injections alone could alter the overall microbial profiles (i.e., microbiota) and individual bacterial abundances with altered antibody responses; dysbiosis in animal models could be partly due to adjuvant injections.Item Open Access Antibody formation and mannose-6-phosphate receptor expression impact the efficacy of muscle-specific transgene expression in murine Pompe disease.(J Gene Med, 2010-11) Sun, Baodong; Li, Songtao; Bird, Andrew; Yi, Haiqing; Kemper, Alex; Thurberg, Beth L; Koeberl, Dwight DBACKGROUND: Lysosomal storage disorders such as Pompe disease can be more effectively treated, if immune tolerance to enzyme or gene replacement therapy can be achieved. Alternatively, immune responses against acid α-glucosidase (GAA) might be evaded in Pompe disease through muscle-specific expression of GAA with adeno-associated virus (AAV) vectors. METHODS: An AAV vector containing the MHCK7 regulatory cassette to drive muscle-specific GAA expression was administered to GAA knockout (KO) mice, immune tolerant GAA-KO mice and mannose-6-phosphate deficient GAA-KO mice. GAA activity and glycogen content were analyzed in striated muscle to determine biochemical efficacy. RESULTS: The biochemical efficacy from GAA expression was slightly reduced in GAA-KO mice, as demonstrated by higher residual glycogen content in skeletal muscles. Next, immune tolerance to GAA was induced in GAA-KO mice by co-administration of a second AAV vector encoding liver-specific GAA along with the AAV vector encoding muscle-specific GAA. Antibody formation was prevented by liver-specific GAA, and the biochemical efficacy of GAA expression was improved in the absence of antibodies, as demonstrated by significantly reduced glycogen content in the diaphragm. Efficacy was reduced in old GAA-KO mice despite the absence of antibodies. The greatest impact upon gene therapy was observed in GAA-KO mice lacking the mannose-6-phosphate receptor in muscle. The clearance of stored glycogen was markedly impaired despite high GAA expression in receptor-deficient Pompe disease mice. CONCLUSIONS: Overall, antibody formation had a subtle effect upon efficacy, whereas the absence of mannose-6-phosphate receptors markedly impaired muscle-targeted gene therapy in murine Pompe disease.Item Open Access B-lymphocyte effector functions in health and disease.(2010) DiLillo, David JohnB cells and humoral immunity make up an important component of the immune system and play a vital role in preventing and fighting off infection by various pathogens. B cells also have been implicated in the pathogenesis of autoimmune disease. However, the various functions that B cells perform during the development and maintenance of autoimmune conditions remain unclear. Therefore, the overall goal of this dissertation was to determine what roles B cells play during autoimmune disease. In the Chapter 3 of this dissertation, the function of B cells was assessed during tumor immunity, a model of immune system activation and cellular immunity. To quantify B cell contributions to T cell-mediated anti-tumor immune responses, mature B cells were depleted from wild type adult mice using CD20 monoclonal antibody (mAb) prior to syngeneic B16 melanoma tumor transfers. Remarkably, subcutaneous (s.c.) tumor volume and lung metastasis were increased two-fold in B cell-depleted mice. Effector-memory and interferon (IFN)γ or tumor necrosis factor (TNF)α-secreting CD4+ and CD8+ T cell induction was significantly impaired in B cell-depleted mice with tumors. Tumor antigen (Ag)-specific CD8+ T cell proliferation was also impaired in tumor-bearing mice that lacked B cells. Thus, B cells were required for optimal T cell activation and cellular immunity in this in vivo non-lymphoid tumor model. In Chapter 4 of this dissertation, the roles that B cells play during immune responses elicited by different allografts were assessed, since allograft rejection is thought to be T cell-mediated. The effects of B cell-depletion on acute cardiac rejection, chronic renal rejection, and skin graft rejection were compared using CD20 or CD19 mAbs. Both CD20 and CD19 mAbs effectively depleted mature B cells, while CD19 mAb treatment depleted plasmablasts and some plasma cells. B cell depletion did not affect acute cardiac allograft rejection, although CD19 mAb treatment prevented allograft-specific IgG production. Nonetheless, CD19 mAb treatment significantly reduced renal allograft rejection and abrogated allograft-specific IgG development, while CD20 mAb treatment did not. By contrast, B cell depletion exacerbated skin allograft rejection and augmented the proliferation of adoptively transferred alloAg-specific CD4+ T cells, demonstrating that B cells can also negatively regulate allograft rejection. Thereby, B cells can either positively or negatively regulate allograft rejection depending on the nature of the allograft and the intensity of the rejection response. Serum antibody (Ab) is, at least in part, responsible for protection against pathogens and tissue destruction during autoimmunity. In Chapter 5 of this dissertation, the mechanisms responsible for the maintenance of long-lived serum Ab levels were examined, since the relationship between memory B cells, long-lived plasma cells, and long-lived humoral immunity remains controversial. To address the roles of B cell subsets in the longevity of humoral responses, mature B cells were depleted in mice using CD20 mAb. CD20+ B cell depletion prevented humoral immune responses and class switching, and depleted existing and adoptively-transferred B cell memory. Nonetheless, B cell depletion did not affect serum Ig levels, Ag-specific Ab titers, or bone marrow (BM) Ab-secreting plasma cell numbers. Co-blockade of LFA-1 and VLA-4 adhesion molecules temporarily depleted long-lived plasma cells from the BM. CD20+ B cell depletion plus LFA-1/VLA-4 mAb treatment significantly prolonged Ag-specific plasma cell depletion from the BM, with a significant decrease in Ag-specific serum IgG. Collectively, these results indicate that BM plasma cells are intrinsically long-lived. Further, these studies now demonstrate that mature and memory B cells are not required for maintaining BM plasma cell numbers, but are required for repopulation of plasma cell-deficient BM. Thereby, depleting mature and memory B cells does not have a dramatic negative effect on pre-existing Ab levels. Collectively, the studies described in this dissertation demonstrate that B cells function through multiple effector mechanisms to influence the course and intensity of normal and autoreactive immune responses: the promotion of cellular immune responses and CD4+ T cell activation, the negative regulation of cellular immune responses, and the production and maintenance of long-lived Ag-specific serum Ab titers. Therefore, each of these three B cell effector mechanisms can contribute independently or in concert with the other mechanisms to clear pathogens or cause tissue damage during autoimmunity.Item Open Access CD20 deficiency in humans results in impaired T cell-independent antibody responses.(J Clin Invest, 2010-01) Kuijpers, Taco W; Bende, Richard J; Baars, Paul A; Grummels, Annette; Derks, Ingrid AM; Dolman, Koert M; Beaumont, Tim; Tedder, Thomas F; van Noesel, Carel JM; Eldering, Eric; van Lier, René AWCD20 was the first B cell differentiation antigen identified, and CD20-specific mAbs are commonly used for the treatment of B cell malignancies and autoantibody-mediated autoimmune diseases. Despite this the role of CD20 in human B cell physiology has remained elusive. We describe here a juvenile patient with CD20 deficiency due to a homozygous mutation in a splice junction of the CD20 gene (also known as MS4A1) that results in "cryptic" splicing and nonfunctional mRNA species. Analysis of this patient has led us to conclude that CD20 has a central role in the generation of T cell-independent (TI) antibody responses. Key evidence to support this conclusion was provided by the observation that although antigen-independent B cells developed normally in the absence of CD20 expression, antibody formation, particularly after vaccination with TI antigens, was strongly impaired in the patient. Consistent with this, TI antipolysaccharide B cell responses were severely impeded in CD20-deficient mice. Our study therefore identifies what we believe to be a novel type of humoral immunodeficiency caused by CD20 deficiency and characterized by normal development of antigen-independent B cells, along with a reduced capacity to mount proper antibody responses.Item Restricted Comparative immunogenicity of HIV-1 clade C envelope proteins for prime/boost studies.(PLoS One, 2010-08-11) Smith, Douglas H; Winters-Digiacinto, Peggy; Mitiku, Misrach; O'Rourke, Sara; Sinangil, Faruk; Wrin, Terri; Montefiori, David C; Berman, Phillip WBACKGROUND: Previous clinical efficacy trials failed to support the continued development of recombinant gp120 (rgp120) as a candidate HIV vaccine. However, the recent RV144 HIV vaccine trial in Thailand showed that a prime/boost immunization strategy involving priming with canarypox vCP1521 followed by boosting with rgp120 could provide significant, although modest, protection from HIV infection. Based on these results, there is renewed interest in the development of rgp120 based antigens for follow up vaccine trials, where this immunization approach can be applied to other cohorts at high risk for HIV infection. Of particular interest are cohorts in Africa, India, and China that are infected with clade C viruses. METHODOLOGY/PRINCIPAL FINDINGS: A panel of 10 clade C rgp120 envelope proteins was expressed in 293 cells, purified by immunoaffinity chromatography, and used to immunize guinea pigs. The resulting sera were collected and analyzed in checkerboard experiments for rgp120 binding, V3 peptide binding, and CD4 blocking activity. Virus neutralization studies were carried out with two different assays and two different panels of clade C viruses. A high degree of cross reactivity against clade C and clade B viruses and viral proteins was observed. Most, but not all of the immunogens tested elicited antibodies that neutralized tier 1 clade B viruses, and some sera neutralized multiple clade C viruses. Immunization with rgp120 from the CN97001 strain of HIV appeared to elicit higher cross neutralizing antibody titers than the other antigens tested. CONCLUSIONS/SIGNIFICANCE: While all of the clade C antigens tested were immunogenic, some were more effective than others in eliciting virus neutralizing antibodies. Neutralization titers did not correlate with rgp120 binding, V3 peptide binding, or CD4 blocking activity. CN97001 rgp120 elicited the highest level of neutralizing antibodies, and should be considered for further HIV vaccine development studies.Item Open Access HIV-specific functional antibody responses in breast milk mirror those in plasma and are primarily mediated by IgG antibodies.(J Virol, 2011-09) Fouda, GG; Yates, NL; Pollara, J; Shen, X; Overman, GR; Mahlokozera, T; Wilks, AB; Kang, HH; Salazar-Gonzalez, JF; Salazar, MG; Kalilani, L; Meshnick, SR; Hahn, BH; Shaw, GM; Lovingood, RV; Denny, TN; Haynes, B; Letvin, NL; Ferrari, G; Montefiori, DC; Tomaras, GD; Permar, SR; Immunology, the Center for HIVAIDS VaccineDespite months of mucosal virus exposure, the majority of breastfed infants born to HIV-infected mothers do not become infected, raising the possibility that immune factors in milk inhibit mucosal transmission of HIV. HIV Envelope (Env)-specific antibodies are present in the milk of HIV-infected mothers, but little is known about their virus-specific functions. In this study, HIV Env-specific antibody binding, autologous and heterologous virus neutralization, and antibody-dependent cell cytotoxicity (ADCC) responses were measured in the milk and plasma of 41 HIV-infected lactating women. Although IgA is the predominant antibody isotype in milk, HIV Env-specific IgG responses were higher in magnitude than HIV Env-specific IgA responses in milk. The concentrations of anti-HIV gp120 IgG in milk and plasma were directly correlated (r = 0.75; P < 0.0001), yet the response in milk was 2 logarithm units lower than in plasma. Similarly, heterologous virus neutralization (r = 0.39; P = 0.010) and ADCC activity (r = 0.64; P < 0.0001) in milk were directly correlated with that in the systemic compartment but were 2 log units lower in magnitude. Autologous neutralization was rarely detected in milk. Milk heterologous virus neutralization titers correlated with HIV gp120 Env-binding IgG responses but not with IgA responses (r = 0.71 and P < 0.0001, and r = 0.17 and P = 0.30). Moreover, IgGs purified from milk and plasma had equal neutralizing potencies against a tier 1 virus (r = 0.65; P < 0.0001), whereas only 1 out of 35 tested non-IgG milk fractions had detectable neutralization. These results suggest that plasma-derived IgG antibodies mediate the majority of the low-level HIV neutralization and ADCC activity in breast milk.Item Open Access Salmonella Typhi Vi capsule prime-boost vaccination induces convergent and functional antibody responses.(Science immunology, 2021-10) Dahora, Lindsay C; Verheul, Marije K; Williams, Katherine L; Jin, Celina; Stockdale, Lisa; Cavet, Guy; Giladi, Eldar; Hill, Jennifer; Kim, Dongkyoon; Leung, Yvonne; Bobay, Benjamin G; Spicer, Leonard D; Sawant, Sheetal; Rijpkema, Sjoerd; Dennison, S Moses; Alam, S Munir; Pollard, Andrew J; Tomaras, Georgia DVaccine development to prevent Salmonella Typhi infections has accelerated over the past decade, resulting in licensure of new vaccines, which use the Vi polysaccharide (Vi PS) of the bacterium conjugated to an unrelated carrier protein as the active component. Antibodies elicited by these vaccines are important for mediating protection against typhoid fever. However, the characteristics of protective and functional Vi antibodies are unknown. In this study, we investigated the human antibody repertoire, avidity maturation, epitope specificity, and function after immunization with a single dose of Vi-tetanus toxoid conjugate vaccine (Vi-TT) and after a booster with plain Vi PS (Vi-PS). The Vi-TT prime induced an IgG1-dominant response, whereas the Vi-TT prime followed by the Vi-PS boost induced IgG1 and IgG2 antibody production. B cells from recipients who received both prime and boost showed evidence of convergence, with shared V gene usage and CDR3 characteristics. The detected Vi antibodies showed heterogeneous avidity ranging from 10 μM to 500 pM, with no evidence of affinity maturation after the boost. Vi-specific antibodies mediated Fc effector functions, which correlated with antibody dissociation kinetics but not with association kinetics. We identified antibodies induced by prime and boost vaccines that recognized subdominant epitopes, indicated by binding to the de–O-acetylated Vi backbone. These antibodies also mediated Fc-dependent functions, such as complement deposition and monocyte phagocytosis. Defining strategies on how to broaden epitope targeting for S. Typhi Vi and enriching for antibody Fc functions that protect against typhoid fever will advance the design of high-efficacy Vi vaccines for protection across diverse populations.Item Restricted Immunization with cocktail of HIV-derived peptides in montanide ISA-51 is immunogenic, but causes sterile abscesses and unacceptable reactogenicity.(PLoS One, 2010-08-10) Graham, Barney S; McElrath, M Juliana; Keefer, Michael C; Rybczyk, Kyle; Berger, David; Weinhold, Kent J; Ottinger, Janet; Ferarri, Guido; Montefiori, David C; Stablein, Don; Smith, Carol; Ginsberg, Richard; Eldridge, John; Duerr, Ann; Fast, Pat; Haynes, Barton F; AIDS Vaccine Evaluation GroupBACKGROUND: A peptide vaccine was produced containing B and T cell epitopes from the V3 and C4 Envelope domains of 4 subtype B HIV-1 isolates (MN, RF, CanO, & Ev91). The peptide mixture was formulated as an emulsion in incomplete Freund's adjuvant (IFA). METHODS: Low-risk, healthy adult subjects were enrolled in a randomized, placebo-controlled dose-escalation study, and selected using criteria specifying that 50% in each study group would be HLA-B7+. Immunizations were scheduled at 0, 1, and 6 months using a total peptide dose of 1 or 4 mg. Adaptive immune responses in16 vaccine recipients and two placebo recipients after the 2nd immunization were evaluated using neutralization assays of sera, as well as ELISpot and ICS assays of cryopreserved PBMCs to assess CD4 and CD8 T-cell responses. In addition, (51)Cr release assays were performed on fresh PBMCs following 14-day stimulation with individual vaccine peptide antigens. RESULTS: 24 subjects were enrolled; 18 completed 2 injections. The study was prematurely terminated because 4 vaccinees developed prolonged pain and sterile abscess formation at the injection site-2 after dose 1, and 2 after dose 2. Two other subjects experienced severe systemic reactions consisting of headache, chills, nausea, and myalgia. Both reactions occurred after the second 4 mg dose. The immunogenicity assessments showed that 6/8 vaccinees at each dose level had detectable MN-specific neutralizing (NT) activity, and 2/7 HLA-B7+ vaccinees had classical CD8 CTL activity detected. However, using both ELISpot and ICS, 8/16 vaccinees (5/7 HLA-B7+) and 0/2 controls had detectable vaccine-specific CD8 T-cell responses. Subjects with moderate or severe systemic or local reactions tended to have more frequent T cell responses and higher antibody responses than those with mild or no reactions. CONCLUSIONS: The severity of local responses related to the formulation of these four peptides in IFA is clinically unacceptable for continued development. Both HIV-specific antibody and T cell responses were induced and the magnitude of response correlated with the severity of local and systemic reactions. If potent adjuvants are necessary for subunit vaccines to induce broad and durable immune responses, careful, incremental clinical evaluation is warranted to minimize the risk of adverse events. TRIAL REGISTRATION: ClinicalTrials.gov NCT00000886.Item Open Access In situ studies of the primary immune response to (4-hydroxy-3-nitrophenyl)acetyl. I. The architecture and dynamics of responding cell populations.(J Exp Med, 1991-05-01) Jacob, J; Kassir, R; Kelsoe, GAfter primary immunization with an immunogenic conjugate of (4-hydroxy-3-nitrophenyl)acetyl, two anatomically and phenotypically distinct populations of antibody-forming cells arise in the spleen. As early as 2 d after immunization, foci of antigen-binding B cells are observed along the periphery of the periarteriolar lymphoid sheaths. These foci expand, occupying as much as 1% of the splenic volume by day 8 of the response. Later, foci grow smaller and are virtually absent from the spleen by day 14. A second responding population, germinal center B cells, appear on day 8-10 and persist at least until day 16 post-immunization. Individual foci and germinal centers represent discrete pauciclonal populations that apparently undergo somatic evolution in the course of the primary response. We suggest that foci may represent regions of predominantly interclonal competition for antigen among unmutated B cells, while germinal centers are sites of intraclonal clonal competition between mutated sister lymphocytes.Item Open Access Induction of anti-myelin antibodies in EAE and their possible role in demyelination.(J Neurosci Res, 1991-12) Sadler, RH; Sommer, MA; Forno, LS; Smith, MEExperimental allergic encephalomyelitis is characterized by invasion of lymphocytes and macrophages into the central nervous system resulting in inflammation, edema, and demyelination. Sera from Lewis rats from 7-95 days after immunization with purified guinea pig CNS myelin were examined with respect to their ability to opsonize myelin. This was correlated with the appearance of antibody components and the relative amounts of antibody to myelin basic protein (MBP) and proteolipid protein (PLP). Sera from rats 10-95 days after immunization preincubated with purified myelin induced phagocytosis of myelin by cultured macrophages with the resulting production of cholesterol ester. This opsonization activity as measured by the percentage of cholesterol esterified reached a peak at 26-27 days after immunization but remained significantly elevated up to 95 days post-immunization compared to the activity of serum from the Freund's adjuvant-injected controls. Immunoblots of the sera revealed a gradual increase in antibody activity against myelin components. ELISA assays for MBP and PLP antibody showed a similar pattern. Antibody to galactocerebroside (GC) was not detected by immunostains nor by the ELISA assay. Areas of demyelination were observed histologically by luxol-fast blue stained spinal cords up to 60 days post-immunization. These results indicate that antibodies to myelin protein when given access to myelin through or within the blood brain barrier could initiate or enhance the phagocytic response by peripheral or resident macrophages.Item Open Access Maternal Fc-mediated non-neutralizing antibody responses correlate with protection against congenital human cytomegalovirus infection.(The Journal of clinical investigation, 2022-08) Semmes, Eleanor C; Miller, Itzayana G; Wimberly, Courtney E; Phan, Caroline T; Jenks, Jennifer A; Harnois, Melissa J; Berendam, Stella J; Webster, Helen; Hurst, Jillian H; Kurtzberg, Joanne; Fouda, Genevieve G; Walsh, Kyle M; Permar, Sallie RHuman cytomegalovirus (HCMV) is the most common congenital infection and a leading cause of stillbirth, neurodevelopmental impairment, and pediatric hearing loss worldwide. Development of a maternal vaccine or therapeutic to prevent congenital HCMV has been hindered by limited knowledge of the immune responses that protect against HCMV transmission in utero. To identify protective antibody responses, we measured HCMV-specific IgG binding and antiviral functions in paired maternal and cord blood sera from HCMV-seropositive transmitting (n = 41) and non-transmitting (n = 40) mother-infant dyads identified via a large, US-based, public cord blood bank. We found that high-avidity IgG binding to HCMV and antibody-dependent cellular phagocytosis (ADCP) were associated with reduced risk of congenital HCMV infection. We also determined that HCMV-specific IgG activation of FcγRI and FcγRII was enhanced in non-transmitting dyads and that increased ADCP responses were mediated through both FcγRI and FcγRIIA expressed on human monocytes. These findings suggest that engagement of FcγRI/FcγRIIA and Fc effector functions including ADCP may protect against congenital HCMV infection. Taken together, these data can guide future prospective studies on immune correlates against congenital HCMV transmission and inform HCMV vaccine and immunotherapeutic development.Item Open Access Neutralizing BAFF/APRIL with atacicept prevents early DSA formation and AMR development in T cell depletion induced nonhuman primate AMR model.(Am J Transplant, 2015-03) Kwun, J; Page, E; Hong, JJ; Gibby, A; Yoon, J; Farris, AB; Villinger, F; Knechtle, SDepletional strategies directed toward achieving tolerance induction in organ transplantation have been associated with an increased incidence and risk of antibody-mediated rejection (AMR) and graft injury. Our clinical data suggest correlation of increased serum B cell activating factor/survival factor (BAFF) with increased risk of antibody-mediated rejection in alemtuzumab treated patients. In the present study, we tested the ability of BAFF blockade (TACI-Ig) in a nonhuman primate AMR model to prevent alloantibody production and prolong allograft survival. Three animals received the AMR inducing regimen (CD3-IT/alefacept/tacrolimus) with TACI-Ig (atacicept), compared to five control animals treated with the AMR inducing regimen only. TACI-Ig treatment lead to decreased levels of DSA in treated animals at 2 and 4 weeks posttransplantation (p < 0.05). In addition, peripheral B cell numbers were significantly lower at 6 weeks posttransplantation. However, it provided only a marginal increase in graft survival (59 ± 22 vs. 102 ± 47 days; p = 0.11). Histological analysis revealed a substantial reduction in findings typically associated with humoral rejection with atacicept treatment. More T cell rejection findings were observed with increased graft T cell infiltration in atacicept treatment, likely secondary to the graft prolongation. We show that BAFF/APRIL blockade using concomitant TACI-Ig treatment reduced the humoral portion of rejection in our depletion-induced preclinical AMR model.Item Open Access Patterns of de novo allo B cells and antibody formation in chronic cardiac allograft rejection after alemtuzumab treatment.(Am J Transplant, 2012-10) Kwun, J; Oh, BC; Gibby, AC; Ruhil, R; Lu, VT; Kim, DW; Page, EK; Bulut, OP; Song, MQ; et al.Even though the etiology of chronic rejection (CR) is multifactorial, donor specific antibody (DSA) is considered to have a causal effect on CR development. Currently the antibody-mediated mechanisms during CR are poorly understood due to lack of proper animal models and tools. In a clinical setting, we previously demonstrated that induction therapy by lymphocyte depletion, using alemtuzumab (anti-human CD52), is associated with an increased incidence of serum alloantibody, C4d deposition and antibody-mediated rejection in human patients. In this study, the effects of T cell depletion in the development of antibody-mediated rejection were examined using human CD52 transgenic (CD52Tg) mice treated with alemtuzumab. Fully mismatched cardiac allografts were transplanted into alemtuzumab treated CD52Tg mice and showed no acute rejection while untreated recipients acutely rejected their grafts. However, approximately half of long-term recipients showed increased degree of vasculopathy, fibrosis and perivascular C3d depositions at posttransplant day 100. The development of CR correlated with DSA and C3d deposition in the graft. Using novel tracking tools to monitor donor-specific B cells, alloreactive B cells were shown to increase in accordance with DSA detection. The current animal model could provide a means of testing strategies to understand mechanisms and developing therapeutic approaches to prevent chronic rejection.Item Open Access Relaxed negative selection in germinal centers and impaired affinity maturation in bcl-xL transgenic mice.(J Exp Med, 1999-08-02) Takahashi, Y; Cerasoli, DM; Dal Porto, JM; Shimoda, M; Freund, R; Fang, W; Telander, DG; Malvey, EN; Mueller, DL; Behrens, TW; Kelsoe, GThe role of apoptosis in affinity maturation was investigated by determining the affinity of (4-hydroxy-3-nitrophenyl)acetyl (NP)-specific antibody-forming cells (AFCs) and serum antibody in transgenic mice that overexpress a suppressor of apoptosis, Bcl-xL, in the B cell compartment. Although transgenic animals briefly expressed higher numbers of splenic AFCs after immunization, the bcl-xL transgene did not increase the number or size of germinal centers (GCs), alter the levels of serum antibody, or change the frequency of NP-specific, long-lived AFCs. Nonetheless, the bcl-xL transgene product, in addition to endogenous Bcl-xL, reduced apoptosis in GC B cells and resulted in the expansion of B lymphocytes bearing VDJ rearrangements that are usually rare in primary anti-NP responses. Long-lived AFCs bearing these noncanonical rearrangements were frequent in the bone marrow and secreted immunoglobulin G(1) antibodies with low affinity for NP. The abundance of noncanonical cells lowered the average affinity of long-lived AFCs and serum antibody, demonstrating that Bcl-xL and apoptosis influence clonal selection/maintenance for affinity maturation.Item Open Access The human antibody response to the surface of Mycobacterium tuberculosis.(PLoS One, 2014) Perley, Casey C; Frahm, Marc; Click, Eva M; Dobos, Karen M; Ferrari, Guido; Stout, Jason E; Frothingham, RichardBACKGROUND: Vaccine-induced human antibodies to surface components of Haemophilus influenzae and Streptococcus pneumonia are correlated with protection. Monoclonal antibodies to surface components of Mycobacterium tuberculosis are also protective in animal models. We have characterized human antibodies that bind to the surface of live M. tuberculosis. METHODS: Plasma from humans with latent tuberculosis (TB) infection (n = 23), active TB disease (n = 40), and uninfected controls (n = 9) were assayed by ELISA for reactivity to the live M. tuberculosis surface and to inactivated M. tuberculosis fractions (whole cell lysate, lipoarabinomannan, cell wall, and secreted proteins). RESULTS: When compared to uninfected controls, patients with active TB disease had higher antibody titers to the surface of live M. tuberculosis (Δ = 0.72 log10), whole cell lysate (Δ = 0.82 log10), and secreted proteins (Δ = 0.62 log10), though there was substantial overlap between the two groups. Individuals with active disease had higher relative IgG avidity (Δ = 1.4 to 2.6) to all inactivated fractions. Surprisingly, the relative IgG avidity to the live M. tuberculosis surface was lower in the active disease group than in uninfected controls (Δ = -1.53, p = 0.004). Patients with active disease had higher IgG than IgM titers for all inactivated fractions (ratios, 2.8 to 10.1), but equal IgG and IgM titers to the live M. tuberculosis surface (ratio, 1.1). Higher antibody titers to the M. tuberculosis surface were observed in active disease patients who were BCG-vaccinated (Δ = 0.55 log10, p = 0.008), foreign-born (Δ = 0.61 log10, p = 0.004), or HIV-seronegative (Δ = 0.60 log10, p = 0.04). Higher relative IgG avidity scores to the M. tuberculosis surface were also observed in active disease patients who were BCG-vaccinated (Δ = 1.12, p < 0.001) and foreign-born (Δ = 0.87, p = 0.01). CONCLUSIONS/SIGNIFICANCE: Humans with active TB disease produce antibodies to the surface of M. tuberculosis with low avidity and with a low IgG/IgM ratio. Highly-avid IgG antibodies to the M. tuberculosis surface may be an appropriate target for future TB vaccines.Item Open Access TSC1 Promotes B Cell Maturation but Is Dispensable for Germinal Center Formation.(PLoS One, 2015) Ci, Xinxin; Kuraoka, Masayuki; Wang, Hongxia; Carico, Zachary; Hopper, Kristen; Shin, Jinwook; Deng, Xuming; Qiu, Yirong; Unniraman, Shyam; Kelsoe, Garnett; Zhong, Xiao-PingAccumulating evidence indicates that the tuberous sclerosis complex 1 (TSC1), a tumor suppressor that acts by inhibiting mTOR signaling, plays an important role in the immune system. We report here that TSC1 differentially regulates mTOR complex 1 (mTORC1) and mTORC2/Akt signaling in B cells. TSC1 deficiency results in the accumulation of transitional-1 (T1) B cells and progressive losses of B cells as they mature beyond the T1 stage. Moreover, TSC1KO mice exhibit a mild defect in the serum antibody responses or rate of Ig class-switch recombination after immunization with a T-cell-dependent antigen. In contrast to a previous report, we demonstrate that both constitutive Peyer's patch germinal centers (GCs) and immunization-induced splenic GCs are unimpaired in TSC1-deficient (TSC1KO) mice and that the ratio of GC B cells to total B cells is comparable in WT and TSC1KO mice. Together, our data demonstrate that TSC1 plays important roles for B cell development, but it is dispensable for GC formation and serum antibody responses.Item Open Access Very low affinity B cells form germinal centers, become memory B cells, and participate in secondary immune responses when higher affinity competition is reduced.(J Exp Med, 2002-05-06) Dal Porto, Joseph M; Haberman, Ann M; Kelsoe, Garnett; Shlomchik, Mark JTo understand the relationship between the affinity of the B cell antigen receptor (BCR) and the immune response to antigen, two lines of immunoglobulin H chain transgenic (Tg) mice were created. H50Gmu(a) and T1(V23)mu(a) mice express mu H chain transgenes that associate with the lambda1 L chains to bind the (4-hydroxy-3-nitrophenyl)acetyl hapten with association constants (K(a)s) of only 1.2 x 10(5) M(-1) and 3 x 10(4) M(-1), respectively. Both lines mounted substantial antibody-forming cell (AFC) and germinal center (GC) responses. H50Gmu(a) Tg mice also generated memory B cells. T1(V23)mu(a) B cells formed AFC and GCs, but were largely replaced in late GCs by antigen-specific cells that express endogenous BCRs. Thus, B lymphocytes carrying BCRs with affinities previously thought to be irrelevant in specific immune responses are in fact capable of complete T cell-dependent immune responses when relieved of substantial competition from other B cells. The failure to observe such B cells normally in late primary responses and in memory B cell populations is the result of competition, rather than an intrinsic inability of low affinity B cells.