Adjuvant-enhanced antibody responses in the absence of toll-like receptor signaling

Abstract

Innate immune signals mediated by Toll-like receptors (TLRs) have been thought to contribute considerably to the antibody-enhancing effects of vaccine adjuvants. However, we report here that mice deficient in the critical signaling components for TLR mount robust antibody responses to T cell-dependent antigen given in four typical adjuvants: alum, Freund's complete adjuvant, Freund's incomplete adjuvant, and monophosphoryl-lipid A/trehalose dicorynomycolate adjuvant. We conclude that TLR signaling does not account for the action of classical adjuvants and does not fully explain the action of a strong adjuvant containing a TLR ligand. This may have important implications in the use and development of vaccine adjuvants.

Figure 1

T dependent antibody responses of Myd88^−/−; Trif^Lps2/Lps2 and control mice using CFA. Two month old mice were immunized with TNP-Hy in CFA on day 0 and boosted with antigen in PBS on day 21. Each point represents the serum anti-TNP titer of an individual mouse. IgE titers represent ng/ml, whereas other measurements represent reciprocal serum dilution yielding half maximal signal. Closed circles, wild type C57BL/6; open squares, Myd88^−/−; Trif^Lps2/Lps2 double knockout mice. Statistically significant differences between mutant and control groups are as indicated with asterisks; *, p>.05; **, p>.01. For methods, see (9).

Figure 2

Comparison of serum antibody responses of C57BL/6 and Myd88^−/−; Trif^Lps2/Lps2 mice given immunogen in different adjuvants. Groups of four mice were immunized with 100μg TNP-KLH in PBS in the indicated adjuvants and anti-TNP titers of the indicated immunoglobulin isotypes determined on day 7 and 14.

Figure 3

Preimmune serum immunoglobulin levels in Myd88^−/−; Trif^Lps2/Lps2 compared to wild type C57BL/6 controls as measured by ELISA. Each point represents data from a different mouse. Closed circles, wild type, C57BL/6; open squares, Myd88^−/−; Trif^Lps2/Lps2 mice.