Lipopolysaccharide from Brucella abortus behaves as a T-cell-independent type 1 carrier in murine antigen-specific antibody responses

Abstract

In order to determine the carrier nature of lipopolysaccharide from Brucella abortus (LPS-BA) in evoking humoral responses, normal and immunodeficient mice were immunized with trinitrophenyl (TNP)-conjugated LPS-BA (TNP-LPS-BA) and the responses were compared with those to known T-dependent and T-independent antigens. TNP-LPS-BA, like T-independent type 1 (TI-1) antigens such as TNP-BA and TNP-LPS from Escherichia coli (TNP-LPS-EC), generated anti-TNP responses in BALB/c, athymic BALB/c nulnu, and CBAIN mice. In contrast, N-2,4-dinitrophenyl-j8-alanylglycylglycyl-substituted keyhole limpet hemocyanin, a typical T-dependent antigen, was not immunogenic in athymic mice, and TNP-Ficoll (T-independent type 2) was ineffective in eliciting humoral responses in CBA/N mice. These results indicate that LPS from B. abortus acts as a TI-i carrier in generating antibody responses. In C3H/HeJ mice, TNP-LPS-BA generated higher-titer immunoglobulin Gi (IgGI), IgG2a, and IgG2b anti-TNP antibodies than TNP-LPS-EC. Compared with those from BALB/c mice, pure resting B cells isolated from C3H/HeJ mice exhibited a 30-fold lower proliferative response to LPS-EC, whereas the LPS-BA response was reduced to a lesser extent (5-fold). This suggests that the disparity observed in antibody titers was due to different abilities of LPS from B. abortus and E. coli to stimulate C3H/HeJ B cells. The ability of LPS from B. abortus to act as a carrier in generating humoral immune responses indicates that LPS-BA can be substituted for whole B. abortus organisms in vaccine development. * Corresponding author. polysaccharides such as TNP-Ficoll are TI-2 antigens. Typically, TI-1 and TI-2 antigens are able to induce IgM antibody production in athymic nude mice, whereas a TD antigen, e.g., DNP-KLH, will induce little or no antibody

Monophosphoryl lipid A behaves as a T-cell-independent type 1 carrier for hapten-specific antibody responses in mice

“…TNP-Cap-MLA elicits anti-TNP antibody responses in BALB/c mice. It is well known that both LPS EC and LPS BA are effective carriers for the TNP hapten, in that both TNP-LPS EC and TNP-LPS BA are able to elicit strong anti-TNP antibody responses of all isotypes in normal mice (4,35). However, these two types of LPS differ dramatically with respect to their endotoxic nature; LPS BA was found to be 300 to 10,000 times less potent than LPS EC in a variety of assays of endotoxic activity (14).…”

“…TNP-Cap-MLA induces anti-TNP antibody responses in athymic mice. LPS EC and LPS BA are effective carriers for the TNP hapten in athymic mice, indicating that they are able to act as TI carriers (4,35). The ability of MLA to act in a T-cell-independent manner was examined by immunizing groups of BALB/c nu/nu mice with TNP-Cap-MLA in parallel with the other previously defined immunogens (Fig.…”

“…(v) TNP-Ficoll. TNP-Ficoll was prepared from aminoethyl-carbamethyl-Ficoll as described by Betts et al (4).…”

“…Measurement of antibody titers. Enzyme-linked immunosorbent assays (ELISAs) were performed by using TNP-bovine serum albumin-coated plates as described by Betts et al (4). Sera were added at different dilutions and detected by isotype-specific goat anti-mouse antibodies (anti-, anti-␥ 1 , anti-␥ 2a , anti-␥ 2b , and anti-␥ 3 ) obtained from Southern Biotechnology Associates (Birmingham, Ala.).…”

“…Furthermore, LPS itself acts as a TI-1 antigen, and this antigenic character is imparted to covalently attached haptens. Thus, the antitrinitrophenyl (anti-TNP) responses elicited by TNP conjugated to LPS from Escherichia coli (TNP-LPS EC [35]) or LPS from Brucella abortus (TNP-LPS BA [4]) are characteristic of TI-1 antigens. TI-1 antigens have been proposed as candidates for vaccines in immunosuppressed populations, such as human immunodeficiency virus-infected individuals, because of their ability to elicit a protective antibody response in the absence of functional helper T-cell populations (12).…”