Browsing by Subject "Immunity, Humoral"

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    Differential Killing of Salmonella enterica Serovar Typhi by Antibodies Targeting Vi and Lipopolysaccharide O:9 Antigen.
    (PLoS One, 2016) Hart, Peter J; O'Shaughnessy, Colette M; Siggins, Matthew K; Bobat, Saeeda; Kingsley, Robert A; Goulding, David A; Crump, John A; Reyburn, Hugh; Micoli, Francesca; Dougan, Gordon; Cunningham, Adam F; MacLennan, Calman A
    Salmonella enterica serovar Typhi expresses a capsule of Vi polysaccharide, while most Salmonella serovars, including S. Enteritidis and S. Typhimurium, do not. Both S. Typhi and S. Enteritidis express the lipopolysaccharide O:9 antigen, yet there is little evidence of cross-protection from anti-O:9 antibodies. Vaccines based on Vi polysaccharide have efficacy against typhoid fever, indicating that antibodies against Vi confer protection. Here we investigate the role of Vi capsule and antibodies against Vi and O:9 in antibody-dependent complement- and phagocyte-mediated killing of Salmonella. Using isogenic Vi-expressing and non-Vi-expressing derivatives of S. Typhi and S. Typhimurium, we show that S. Typhi is inherently more sensitive to serum and blood than S. Typhimurium. Vi expression confers increased resistance to both complement- and phagocyte-mediated modalities of antibody-dependent killing in human blood. The Vi capsule is associated with reduced C3 and C5b-9 deposition, and decreased overall antibody binding to S. Typhi. However, purified human anti-Vi antibodies in the presence of complement are able to kill Vi-expressing Salmonella, while killing by anti-O:9 antibodies is inversely related to Vi expression. Human serum depleted of antibodies to antigens other than Vi retains the ability to kill Vi-expressing bacteria. Our findings support a protective role for Vi capsule in preventing complement and phagocyte killing of Salmonella that can be overcome by specific anti-Vi antibodies, but only to a limited extent by anti-O:9 antibodies.
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    ItemOpen Access
    Germinal center entry not selection of B cells is controlled by peptide-MHCII complex density.
    (Nature communications, 2018-03-02) Yeh, Chen-Hao; Nojima, Takuya; Kuraoka, Masayuki; Kelsoe, Garnett
    B cells expressing high affinity antigen receptors are advantaged in germinal centers (GC), perhaps by increased acquisition of antigen for presentation to follicular helper T cells and improved T-cell help. In this model for affinity-dependent selection, the density of peptide/MHCII (pMHCII) complexes on GC B cells is the primary determinant of selection. Here we show in chimeric mice populated by B cells differing only in their capacity to express MHCII (MHCII+/+ and MHCII+/-) that GC selection is insensitive to halving pMHCII density. Alone, both B cell types generate identical humoral responses; in competition, MHCII+/+ B cells are preferentially recruited to early GCs but this advantage does not persist once GCs are established. During GC responses, competing MHCII+/+ and MHCII+/- GC B cells comparably accumulate mutations and have indistinguishable rates of affinity maturation. We conclude that B-cell selection by pMHCII density is stringent in the establishment of GCs, but relaxed during GC responses.
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    Single-shot Ad26 vaccine protects against SARS-CoV-2 in rhesus macaques.
    (Nature, 2020-10) Mercado, Noe B; Zahn, Roland; Wegmann, Frank; Loos, Carolin; Chandrashekar, Abishek; Yu, Jingyou; Liu, Jinyan; Peter, Lauren; McMahan, Katherine; Tostanoski, Lisa H; He, Xuan; Martinez, David R; Rutten, Lucy; Bos, Rinke; van Manen, Danielle; Vellinga, Jort; Custers, Jerome; Langedijk, Johannes P; Kwaks, Ted; Bakkers, Mark JG; Zuijdgeest, David; Rosendahl Huber, Sietske K; Atyeo, Caroline; Fischinger, Stephanie; Burke, John S; Feldman, Jared; Hauser, Blake M; Caradonna, Timothy M; Bondzie, Esther A; Dagotto, Gabriel; Gebre, Makda S; Hoffman, Emily; Jacob-Dolan, Catherine; Kirilova, Marinela; Li, Zhenfeng; Lin, Zijin; Mahrokhian, Shant H; Maxfield, Lori F; Nampanya, Felix; Nityanandam, Ramya; Nkolola, Joseph P; Patel, Shivani; Ventura, John D; Verrington, Kaylee; Wan, Huahua; Pessaint, Laurent; Van Ry, Alex; Blade, Kelvin; Strasbaugh, Amanda; Cabus, Mehtap; Brown, Renita; Cook, Anthony; Zouantchangadou, Serge; Teow, Elyse; Andersen, Hanne; Lewis, Mark G; Cai, Yongfei; Chen, Bing; Schmidt, Aaron G; Reeves, R Keith; Baric, Ralph S; Lauffenburger, Douglas A; Alter, Galit; Stoffels, Paul; Mammen, Mathai; Van Hoof, Johan; Schuitemaker, Hanneke; Barouch, Dan H
    A safe and effective vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) may be required to end the coronavirus disease 2019 (COVID-19) pandemic1-8. For global deployment and pandemic control, a vaccine that requires only a single immunization would be optimal. Here we show the immunogenicity and protective efficacy of a single dose of adenovirus serotype 26 (Ad26) vector-based vaccines expressing the SARS-CoV-2 spike (S) protein in non-human primates. Fifty-two rhesus macaques (Macaca mulatta) were immunized with Ad26 vectors that encoded S variants or sham control, and then challenged with SARS-CoV-2 by the intranasal and intratracheal routes9,10. The optimal Ad26 vaccine induced robust neutralizing antibody responses and provided complete or near-complete protection in bronchoalveolar lavage and nasal swabs after SARS-CoV-2 challenge. Titres of vaccine-elicited neutralizing antibodies correlated with protective efficacy, suggesting an immune correlate of protection. These data demonstrate robust single-shot vaccine protection against SARS-CoV-2 in non-human primates. The optimal Ad26 vector-based vaccine for SARS-CoV-2, termed Ad26.COV2.S, is currently being evaluated in clinical trials.