IgG1 Is Required for Optimal Protection after Immunization with the Purified Porin OmpD from Salmonella Typhimurium

Abstract

In mice, the IgG subclass induced after Ag encounter can reflect the nature of the Ag. Th2 Ags such as alum-precipitated proteins and helminths induce IgG1, whereas Th1 Ags, such as Salmonella Typhimurium, predominantly induce IgG2a. The contribution of different IgG isotypes to protection against bacteria such as S. Typhimurium is unclear, although as IgG2a is induced by natural infection, it is assumed this isotype is important. Previously, we have shown that purified S. Typhimurium porins including outer membrane protein OmpD, which induce both IgG1 and IgG2a in mice, provide protection to S. Typhimurium infection via Ab. In this study we report the unexpected finding that mice lacking IgG1, but not IgG2a, are substantially less protected after porin immunization than wild-type controls. IgG1-deficient mice produce more porin-specific IgG2a, resulting in total IgG levels that are similar to wild-type mice. The decreased protection in IgG1-deficient mice correlates with less efficient bacterial opsonization and uptake by macrophages, and this reflects the low binding of outer membrane protein OmpD–specific IgG2a to the bacterial surface. Thus, the Th2-associated isotype IgG1 can play a role in protection against Th1-associated organisms such as S. Typhimurium. Therefore, individual IgG subclasses to a single Ag can provide different levels of protection and the IgG isotype induced may need to be a consideration when designing vaccines and immunization strategies.

Outer membrane protein size and LPS O-antigen define protective antibody targeting to the Salmonella surface

“…1a and ref. 12 ) in the absence of additional adjuvant. The induced anti-STmOmpD IgG bound to the surface of two different isolates of STm: the model laboratory strain SL1344 and a representative invasive African isolate of STm, D23580, which was originally isolated from an African patient 13 (Fig.…”

“…OMPs were purified by 2% (v/v) Triton X-100 extraction from bacterial pellets 36 . STmOmpD (from OmpC and OmpF-deficient STm SL1344 or an OmpC, OmpF, and wbaPdeficient mutant) and STm or SEn porins were purified by 2% (v/v) Triton X-100 extraction and repeated extraction with SDS and separation by fast protein liquid chromatography on a Sephacryl S-200 column before dialysis against PBS/0.1% (w/v) SDS in PBS 10,12,37 . The level of LPS detected in OmpD preparations by limulus assay was typically ≤ 2 EU / 10 μg OmpD.…”

“…Previously, using a number of model systems, we had identified that IgG antibodies to the porin protein OmpD can offer cell-dependent or complement-dependent protection 10,11 . Unexpectedly, not all IgG isotypes offer equivalent protection, and this correlated to the level of access of antibodies to bind OmpD in the presence of O-Ag 12 . This suggests that O-Ag influences the level of binding of IgG to the bacterial surface.…”

Enhanced Immune Responses with Serum Proteomic Analysis of Hu Sheep to Foot-and-Mouth Disease Vaccine Emulsified in a Vegetable Oil Adjuvant

“…Different subtypes of IgG, such as IgG1 and IgG2, provide animals with the bulk of immunity against the majority of microbial agents. During T cell-dependent immunity, the major IgG subtypes progressively change [51] and are influenced by T lymphocytes and their produced cytokines. In animals, IL-4 is preferred to switch activated B cells into produce the IgG1 antibody (Th2) and IFN-γ is associated with boosting the IgG2 response (Th1) [52][53][54][55].…”

Effect of Deletion of Gene Cluster involved in Synthesis of Enterobacterial Common Antigen on Virulence and Immunogenicity of Live Attenuated Salmonella Vaccine when Delivering Heterologous Streptococcus pneumoniae Antigen PspA

“…In mice, the direction of IgG (IgG1 vs IgG2a) switching can re ect the polarization of the Th cell response [38]. We compared the levels of two isotype subclasses of anti-PspA IgG1 and IgG2a in this study.…”