Immunological tolerance of the mouse IgE system: dissociation between T cell tolerance and suppressor cell activity

CpG containing oligodeoxynucleotides are potent adjuvants for parenteral vaccination with the fusion (F) protein of respiratory syncytial virus (RSV)

The feasibility of using oligodeoxynucleotides (ODN) containing unmethylated CpG motifs as parenteral adjuvants for subunit vaccines against RSV was tested in BALB/c mice. Compared with immunization with natural F protein adsorbed to aluminum hydroxide (F/AlOH) adjuvant alone, coadministration of F/AlOH with CpG ODN resulted in statistically significant increases in serum neutralization titers, an enhanced generation of splenic antigen-dependent killer cell precursors, and accelerated clearance of infectious virus from lungs 4 days after challenge. The statistically significant increases in serum IFNgamma and anti-F protein IgG2a titers, and significantly diminished pulmonary IL-5 and eosinophilia after challenge indicated that CpG ODN enhanced the ability of F/AlOH to elicit type 1 immune responses. F protein-specific serum IgE titers were also reduced. Further analysis of pulmonary inflammatory cells demonstrated an expansion of CD8(+) T cells, relative to the CD4(+) T cell compartment. The potency of CpG ODN was not adversely affected in gene knockout mice devoid of the p35 chain of the IL-12 heterodimer. Taken together, the results suggest a novel formulation for naïve recipients of F protein-based subunit vaccines that does not result in a type 2 phenotype.

The immunogenicity of subunit vaccines for respiratory syncytial virus after co-formulation with aluminum hydroxide adjuvant and recombinant interleukin-12

The effects of recombinant interleukin-12 (rIL-12) on immune responses generated by subunit vaccines for respiratory syncytial virus (RSV) were evaluated in BALB/c mice. Parenteral co-administration of rIL-12 with F/AlOH or F/PBS resulted in accelerated clearance of infectious virus from the lungs 4 days after challenge. The immune responses elicited by 0.03 microg of F protein plus 10 ng of rIL-12 adsorbed to AlOH were more efficacious than those induced by 3 microg of F protein co-formulated with 1,000 ng of rIL-12 in PBS alone. Adsorption to AIOH prolonged the presence of rIL-12 in the sera. The resultant systemic humoral immune responses after vaccination with F/AlOH or G/AlOH were dependent on the dose of rIL-12 and characterized by heightened serum immunoglobulin G2a (IgG2a) antibody titers. Co-administration of rIL-12 with F/AlOH was also associated with diminished protein-specific IgE titers, elevated neutralizing antibody titers, and interferon-gamma and (IFN-gamma) in the sera, and enhanced antigen-dependent killer cell activity in the lungs after challenge. For maximum benefit, the data suggested that rIL-12 must be co-administered with F/AlOH. Collectively, the results indicated that rIL-12 directed immune responses toward a type 1 phenotype. However, examination of pulmonary inflammatory cells after challenge suggested that the type 1 phenotype was not absolute. Co-formulation with rIL-12 did not diminish pulmonary eosinophilia upon challenge of naive mice primed with F/AlOH, G/AlOH, or FI-RSV, and CD4+ T cells were expanded relative to the CD8+ T-cell compartment. These results are important for the future design of subunit vaccines against RSV.

Treatment of spinal cord-induced experimental allergic encephalomyelitis in the Lewis rat with liposomes presenting central nervous system antigens

Chronic-relapsing experimental allergic encephalomyelitis (CR-EAE) in the Lewis rat, induced by the injection of spinal cord tissue in complete Freund's adjuvant (SC/CFA), was studied in vivo by treatment with liposomes containing central nervous tissue antigens, and in vitro by lymphocyte proliferation assays. Intracardiac administration of myelin basic protein (MBP) liposomes, galactocerebroside (GC) liposomes, or MBP + GC liposomes substantially reduced the clinical severity and/or delayed the onset of the initial phase of disease. Liposomes prepared from whole myelin provided even greater protection, and were effective at suppressing both the first disease episode and the relapses. These results indicate that while GC and MBP may play significant roles in the development of CR-EAE in the Lewis rat, immune responses to other antigens are probably also involved. Splenic and lymph node lymphocytes from MBP-GC liposome-treated rats, and splenic lymphocytes from cytochrome-GC (CYT-GC) liposome-treated rats, showed drastically reduced abilities to proliferate in response to MBP in culture. Spleen cells from both the MBP-GC- and CYT-GC-liposome-treated donors were able to actively suppress antigen-induced proliferation of MBP-primed lymphocytes. These findings suggest participation of both clonal anergy, and active suppressor cells in the liposome-mediated suppression of CR-EAE in the Lewis rat.

Suppression of experimental allergic encephalomyelitis by MBP-coupled lymphoid cells and by MBP-liposomes: a comparison

In previous experiments, we showed that administration of myelin basic protein (MBP) inserted into phosphatidyl-serine liposomes, to susceptible animals suppressed the clinical manifestations of both acute and chronic-relapsing EAE. In this report we compare the effectiveness of treatment with MBP-liposomes and with MBP-coupled syngeneic spleen cells in EAE protection. Lewis rats treated with 150 micrograms MBP-liposomes or with 160 micrograms (35 x 10(6] MBP-coupled spleen cells, given 7 days before and 7 days after encephalitogenic challenge were equally protected against clinical EAE, when compared to untreated controls. In addition to clinical protection, in vitro proliferative responses of lymphocytes from treated rats were significantly reduced, but delayed hypersensitivity (DTH) reactions remained unaffected. Proliferation of lymphocytes from MBP-sensitized donors was inhibited by the addition of spleen cells but not of lymph node cells from treated donors. The inhibitory effect was observed with spleen cells regardless of whether the donors were treated or not, was antigen nonspecific, and localized in a radio-resistant, adherent cell population. Adoptive transfers of spleen cells from treated donors, after a 48-hr in vitro incubation with concanavalin A, showed that the cells from donors treated with MBP-coupled spleen cells, but not with MBP-liposomes, suppressed the disease in recipients, following challenge with MBP-complete Freund's adjuvant (CFA). These results suggest that two distinct mechanisms operate in the protection by MBP-coupled cells and MBP-liposomes, respectively.

Role of interferon-gamma in the modulation of the IgE response by 2,4-dinitrophenyl-Bordetella pertussis vaccine in the mouse

Immunization of mice with 2,4-dinitrophenyl-Bordetella pertussis (DNP-BP) failed to induce anti-DNP IgE responses. Administration of DNP-BP induced, however, the formation of anti-DNP IgE B memory cells, as demonstrated by adoptive transfer. Furthermore, mice pretreated with DNP-BP and primed with 2 micrograms DNP-ovalbumin (OA) in alum 2 weeks later produced high day-7 anti-DNP IgE levels. These subsided to near undetectable levels by day 12-14. The transient expression of serum IgE levels was accompanied by normal levels of anti-DNP IgG. The anti-OA response induced as a result of priming with DNP-OA in alum was not affected by pretreatment with DNP-BP. IgG subclass analysis revealed that mice pretreated with DNP-BP had elevated levels of IgG2a and reduced levels of IgG1 as compared to control (TNP-keyhole limpet hemocyanin-pretreated) mice. Treatment of mice with an anti-interferon-gamma monoclonal antibody, shortly after immunization with DNP-BP, not only reduced anti-DNP IgG2a levels, but prevented the sharp anti-DNP IgE decline that occurred after priming with DNP-OA in alum. These results suggest that DNP-BP-induced interferon-gamma production modulates Ig isotype expression in vivo in an anti-gen-specific manner.

Antigen leakage from immunosorbents. Implications for the detection of site-directed auto-anti-idiotypic antibodies

The detection of site-directed anti-idiotypic antibodies is usually based on their ability to inhibit the binding of antigen to idiotype, in either solid- or fluid-phase radioimmunoassays. Passage of serum over antigen-coupled immunosorbents for the purpose of removing the idiotypes from complexes with putative anti-idiotypic antibodies resulted in the release of significant amounts of antigen into the effluents. Normal sera or even isotonic buffers were similarly contaminated with antigen. The amount of antigen released ranged between 200-400 ng/ml, well in excess of the minimal amount required in the inhibition assay. Antigen was detected in effluents passed over a number of antigen coupled-matrices and even in affinity-purified antibody preparations obtained by elution from immunosorbents coupled with dinitrophenyl (DNP)-protein conjugates. Attempts to stabilize the antigen-coupled matrices with glutaraldehyde resulted in a perceptible but insufficient decrease in the amount of antigen released. In the case of anti-hapten antibodies, antigen interference was circumvented by utilizing monovalent haptens such as DNP-lysine coupled to the immunosorbent either directly or through a spacer arm. In the case of protein antigens, the leakage was almost completely prevented by preparing glutaraldehyde-polymerized immunosorbents directly from solution.

Suppressor T cell memory. II. The role of memory suppressor T cells in tolerance to human gamma globulin

The transient presence of suppressor T cell (Ts) activity in high-dose tolerance to human gamma globulin (HGG), and its (apparent) absence in low-dose tolerance, have been advanced as strong evidence against the concept that Ts play an important role in maintenance of immunological unresponsiveness. To analyze this question, CBA mice were exposed to high or low doses of deaggregated HGG (dHGG) and later challenged with HGG in immunogenic form (aHGG); their capacity to mount a primary or secondary suppressive response was assessed in an adoptive hapten-carrier system. Primary suppression reached a maximum 7 d after high-dose tolerance induction and gradually waned thereafter, being no longer detectable by day 30-35. Subsequent challenge of tolerant mice with aHGG, however, led to a rapid reactivation of suppression that bore the hallmarks of an anamnestic secondary response, and this effect was still demonstrable 135 d after tolerance induction. It was also shown that a single low dose of dHGG was capable of generating memory for suppression despite the absence of detectable primary suppression, indicating that the latter is not a prerequisite for induction of memory cells. The results were interpreted as indicating that tolerance, like immunity, is a manifestation of specific immunological memory. If tolerance to self-antigens is maintained by a similar mechanism, it would be expected that memory Ts could be induced during the early stages of fetal development. Mice were therefore exposed to tolerogen in utero by injection of their mothers with dHGG at day 7 of gestation, and were assessed at various times after birth for the capacity to exhibit primary or secondary suppression in adoptive transfer. Nonspecific suppression masked any specific effects during the first 5 wk of life. Antigen-specific, primary suppression was demonstrable subsequently until 10-12 wk of age, and if the animals were challenged with aHGG before transfer an anamnestic secondary suppressive response could be elicited up to 6 mo of age. These observations are consistent with the notion that memory Ts may play an important role in the maintenance of self-tolerance.