Binding Sites of Anti-Lcr V Monoclonal Antibodies Are More Critical than the Avidities and Affinities for Passive Protection against Yersinia pestis Infection in a Bubonic Plague Model

Plague is a zoonotic disease that is caused by Yersinia pestis. Monoclonal antibodies (mAbs) that bind to the V-antigen, a virulence factor that is produced by Y. pestis, can passively protect mice from plague. An analysis of protective mAbs that bind to V-antigen was made to assess binding sites, avidities, and affinities. Anti-V mAbs were screened for their efficacy in a murine model of plague. Antigen-binding sites of protective V mAbs were determined with a linear peptide library, V-antigen fragment, competitive binding, and surface plasmon resonance. The avidities to the V-antigen was determined by ELISA, and affinities of the mAbs to the V-antigen were determined by surface plasmon resonance. The most protective mAb 7.3 bound to a unique conformational site on the V-antigen, while a less protective mAb bound to a different conformational site located on the same V-antigen fragment as mAb 7.3. The avidity of mAb 7.3 for the V-antigen was neither the strongest overall nor did it have the highest affinity for the V-antigen. The binding site of the most protective mAb was critical in its ability to protect against a lethal plague challenge.

Immunoinformatic prediction about potential novel vaccine in surface antigen fragment protein of Toxoplasma gondii

<p class="MsoNormal" style="text-align: justify; text-justify: inter-ideograph;"><span style="font-size: 9.0pt;">Toxoplasmosis is one of the most widespread infections in animals and humans. The <em>Toxoplasma gondii</em> major surface antigen, called SAG1 or p30, is a highly immunogenic protein which has generated great interest as a diagnostic reagent, as a potential subunit vaccine, and for its role in invasion. In this study, the epitopes of <em>Toxoplasma gondii</em> SAG1 were identified using bioinformatics. Through the analysis of the out¬put of both NetCTL and CTLPred, and B-cell epitope prediction, the position of all the epitopes were found and combined in four sequences. The different tasks including, T-cell and B-cell prediction, Antigenicity determination of the conserved peptides, Homology modeling, Allergenicity and epitope conservancy analysis were done on the conserved peptides. We predict that our proposed epitopes would also trigger an immune response in vitro.</span></p><span style="font-size: 18.0pt; font-family: 'Times New Roman','serif'; mso-fareast-font-family: Batang; mso-ansi-language: EN-US; mso-fareast-language: EN-US; mso-bidi-language: AR-SA;">Immunoinformatic prediction about potential novel vaccine in surface antigen fragment protein of <em>Toxoplasma gondii</em></span>

Supramolecular biosensors based on electropolymerised pyrrole–cyclodextrin modified surfaces for antibody detection

The self-assembly of an adamantane-appended polymer bearing an antigen fragment on a polypyrrole–cyclodextrin modified surface provides a highly sensitive immunosensor with low limits of detection for celiac disease related antibodies.

Regions and Activities of Simian Virus 40 T Antigen That Cooperate with an Activated ras Oncogene in Transforming Primary Rat Embryo Fibroblasts

ABSTRACT Prolonged expression of a ras oncogene in primary cells accelerates the natural process of senescence. This ras-induced permanent growth arrest is bypassed in cells expressing the simian virus 40 large T antigen. Previously we showed that two regions of T antigen, a region consisting of the N-terminal 147 amino acids and a region consisting of amino acids 251 to 708 (T251-708), independently overcome ras-induced senescence. Coexpression of either T-antigen fragment and Ras results in the appearance of dense foci of transformed cells. Using a series of mutants that produce shorter T-antigen fragments, we show that the C-terminal limit of the N-terminal T-antigen fragment that cooperates with Ras lies between amino acids 83 and 121. The N-terminal limit of the C-terminal T-antigen fragment lies between amino acids 252 and 271. In addition, we present evidence that cooperation between the N-terminal fragment and Ras depends upon an intact T-antigen J domain and the ability of the T antigen to bind and inactivate the growth-suppressive effect of the tumor suppressor Rb. Introduction of specific amino acid substitutions surrounding residue 400 into T251-708 prevented the fragment from cooperating with Ras. T251-708 proteins with these same substitutions inhibited the transcriptional transactivating potential of p53 as effectively as did the wild-type protein. Thus, at least one activity contained within T251-708, other than inactivating p53 as a transcriptional transactivator, is likely to be required to bypass Ras-induced senescence.

Prior Immunity to Homologous and HeterologousSalmonella Serotypes Suppresses Local and Systemic Anti-Fragment C Antibody Responses and Protection from Tetanus Toxin in Mice Immunized with Salmonella Strains Expressing Fragment C

ABSTRACT We have investigated the effect of preexisting immunity to homologous (Salmonella typhimurium) or heterologous (S. dublin) serotypes of Salmonella on the ability of an attenuated S. typhimurium aroA aroD vector (BRD509) to immunize mice against the heterologous antigen fragment C (FrgC). We studied two strains, BRD847 and BRD937, expressing FrgC carried on plasmids that differ only with respect to the promoter controlling FrgC expression, the nirB promoter in the case of BRD847 and the htrA promoter in the case of BRD937. Mice were preimmunized orally with S. typhimurium BRD509,S. dublin aroA aroD (BRD620), or saline. Forty-four days later, they were immunized orally with BRD847 or BRD937. Prior immunity to S. typhimurium severely depressed the serum immunoglobulin G (IgG) and IgA anti-FrgC response in both BRD847- and BRD937-immunized mice. Mice with existing immunity to S. dublin also had lower IgG anti-FrgC geometric mean titers (GMTs) than did mice preimmunized with saline, but this difference was significant only in the case of mice immunized with BRD937. However, in nonimmune mice or in mice preimmunized with S. typhimuriumor S. dublin, the anti-FrgC IgG GMTs were always higher in mice in the BRD937 groups than in the equivalent BRD847 groups. This is reflected in the effect of prior immunity on the ability of oral immunization with BRD847 or BRD937 to protect mice from challenge with a lethal dose of tetanus toxin. All of the mice preimmunized with saline and then immunized with BRD847 or BRD937 survived challenge. Only 20% of the animals immunized with BRD847 and 60% of the mice in the BRD937 group survived tetanus toxin challenge if they were preimmunized with BRD509. Preexisting immunity to S. dublindid not affect the ability of BRD937 to immunize mice against tetanus, but it did reduce the efficiency of BRD847: only 60% percent of the mice survived challenge. The intestinal secretory IgA responses to FrgC were very similar in the BRD847 and BRD937 groups. Prior immunity did depress the IgA anti-FrgC titers but only significantly so in the mice preimmunized with BRD509. These results show that preexistingSalmonella immunity, particularly to homologous serotypes, can severely compromise the ability of live Salmonellavectors to deliver heterologous antigens to the mammalian immune system. However, the results also indicate that this may be overcome by the design of more powerful in vivo expression systems.