Anti-Mouse IgG3 polyclonal antibody

Broadly neutralizing antibodies (bNAbs) protect against HIV infection in non-human primates and their efficacy may be enhanced through interaction with Fc receptors on immune cells. Antibody isotype is a modulator of this binding with the IgG3 subclass mediating potent Fc effector function and is associated with HIV vaccine efficacy and HIV control. BNAb functions are typically assessed independently of the constant region with which they are naturally expressed. To examine the role of natural isotype in the context of a bNAb lineage we studied CAP256, an HIV-infected individual that mounted a potent V2-specific bNAb response. CAP256 expressed persistently high levels of plasma IgG3 which we found mediated both broad neutralizing activity and potent Fc function. Sequencing of germline DNA and the constant regions of V2-directed bNAbs from this donor revealed the expression of a novel IGHG3 allele as well as IGHG3*17, an allele that produces IgG3 antibodies with increased plasma half-life. Both allelic variants were used to generate CAP256-VRC26.25 and CAP256-VRC26.29 IgG3 bNAbs and these were compared to IgG1 versions. IgG3 variants were shown to have significantly higher phagocytosis and trogocytosis compared to IgG1 versions, which corresponded to increased affinity for Fc gamma RIIa. Neutralization potency was also significantly higher for IgG3 bNAbs, particularly against viruses lacking the N160 glycan. By exchanging hinge regions between subclass variants, we showed that hinge length modulated both neutralization potency and Fc function. This study showed that co-operation between the variable and natural IgG3 constant regions enhanced the polyfunctionality of antibodies, indicating the value of leveraging genetic variation which could be exploited for passive immunity. Author summary In the only partially effective HIV vaccine trial to date, reduced risk of infection correlated with IgG3 antibodies that bound to the V2 region of the HIV envelope. IgG3 antibodies potently mediate the broadest range of Fc cytotoxic functions such as complement deposition, cellular lysis, engulfment and membrane nibbling. The relevance of different IgG3 alleles in antibody function is not typically examined, nor are antibodies usually assessed in the context of their natural isotype. Here we show that IgG3 V2-specific broadly neutralizing antibodies from donor CAP256 mediated both enhanced cytotoxic functions and neutralization potency compared to an IgG1 variant. We demonstrate that the long hinge region of IgG3 facilitated this increased functionality. These data suggest that isotype may be tuned to enhance both neutralization and cytotoxic activity of broadly neutralizing antibodies that can be used to improve the efficacy of passive immunization strategies for HIV prevention.

Brucellosis is an infectious disease caused by Brucella bacteria, affecting animals and humans. It is found as an endemic disease in many parts of the world, especially in the Middle East, Central Asian, and South American countries. The objective of this study was to prepare alginate microparticle containing conjugate of Brucella melitensis 16 M oligopolysaccharide (OPS) with tetanus toxoid, and to assess its immunogenicity in mouse, in order to find a new method of confronting brucellosis. In this study, we extracted OPS from lipopolysaccharide (LPS) and conjugated it with tetanus toxoid by amidation method. Then, the obtained conjugate was condensed by gel filtration, followed by emulcification method in iso-octane organic phase to prepare alginate microparticles containing the conjugate. In our study, sera titr of antibodies IgM, IgA, IgG(2a), IgG(1), IgG(2b), IgG(3), and total IgG generated against oligopolysaccharide was performed by ELISA test. The final results, considering the obtained immunogenicity and the increased titer of antibodies IgG1 (19 times), IgG3 (19 times), IgG (15 times), and IgM (9 times) after injection of produced microparticle in mouse indicates appropriateness of the produced microparticle as a candidate vaccine. Thus, it could be concluded that alginate microparticles containing conjugates of B. melitensis 16 M oligopolysaccharide with tetanus toxoid can be proposed as a candidate anti-brucellosis vaccine.