Humoral and cellular immunity induced by antigens adjuvanted with colloidal iron hydroxide.

The immunopotentiating activities of colloidal iron hydroxide, a novel, experimental mineral adjuvant, and of aluminium hydroxide. the licensed adjuvant for human vaccines, were compared. Our studies revealed that colloidal iron hydroxide and aluminium hydroxide behaved comparably with respect to supporting induction of an antibody response to tetanus toxoid. Furthermore, mice immunized with both, the experimental vaccine (tick-borne encephalitis virus (TBEV) antigen adsorbed to colloidal iron hydroxide) or with a commercially available TBEV vaccine (adjuvanted with aluminium hydroxide), developed long-lasting antibody responses which protected the animals from TBEV infection even one year after vaccination. The use of colloidal iron hydroxide as adjuvant had the additional advantage to reproducibly support induction of HIV-1 envelope-specific cytotoxic T lymphocytes (CTL), when used as adjuvant for a HIV-1 env-carrying recombinant fowlpox virus and being applied via the subcutaneous route. Aluminium hydroxide was much less active in this respect. Non-adjuvanted recombinant fowlpox elicited CTLs only when given intravenously or intraperitoneally, vaccination routes considered not to be suitable for routine use in humans. Further studies to evaluate the use of colloidal iron as possible alternative and/or supplement for routinely used mineral adjuvants may therefore be warranted.

Adjuvant/carrier activity of inactivated tick-borne encephalitis virus.

Virus-like or virus-derived particles have been reported to increase the immunogenicity of foreign antigens. In this study formaldehyde-inactivated tick-borne encephalitis virus (TBEV), a potent immunogen in humans, was tested for possible adjuvant/carrier function. The results of our study revealed that substantial antibody titers against very low doses of tetanus toxoid could be obtained when mice were immunized with the antigen covalently coupled to TBEV (using N-succinimidyl-3-(2-pyridyldithio)propionate, a heterobifunctional, cleavable crosslinker containing a disulfide bridge). In contrast, only moderate anti-tetanus toxoid titers were induced by immunizations with a simple mixture of low dose tetanus toxoid and TBEV or when the disulfide bridge of the crosslinker used to couple tetanus toxoid to TBEV was cleaved prior to immunization. The antibody response to TBEV, on the other hand, was not influenced by its linkage to tetanus toxoid. Comparable anti-TBEV titers were obtained following immunization of the animals with either the TBEV-tetanus toxoid conjugate or the mixture of tetanus toxoid and TBEV. Prior application of a TBEV vaccine did not change the antibody response against tetanus toxoid and thus carrier-induced epitopic suppression could be ruled out. The abovementioned adjuvant/carrier properties of TBEV might make it a suitable candidate for use in bi- or multivalent vaccines containing weak immunogens.

Method for the isolation of biologically active monomeric immunoglobulin A from a plasma fraction.

A purification method for immunoglobulin A (IgA) yielding monomeric IgA with a purity of over 97% has been developed. This procedure uses ethanol-precipitated plasma (Cohn fraction III precipitate) as the starting material and includes heparin-Sepharose adsorption, dextran sulfate and ammonium sulfate precipitation, hydroxyapatite chromatography, batch adsorption by an anion-exchange matrix and gel permeation. Additional protein G Sepharose treatment leads to an IgA preparation of greater than 99% purity. The isolated IgA presented with an IgA subclass distribution, equivalent to IgA in unfractionated plasma, and was biologically active, as was shown by its ability to down-modulate Haemophilus influenzae-b-induced IL-6 secretion of human monocytes.