ESAT-6 subunit vaccination against Mycobacterium tuberculosis.

The ESAT-6 antigen from Mycobacterium tuberculosis is a dominant target for cell-mediated immunity in the early phase of tuberculosis (TB) in TB patients as well as in various animal models. The purpose of our study was to evaluate the potential of ESAT-6 in an experimental TB vaccine. We started out using dimethyl dioctadecylammonium bromide (DDA), an adjuvant which has been demonstrated to be efficient for the induction of cellular immune responses and has been used successfully before as a delivery system for TB vaccines. Here we demonstrate that, whereas immune responses to both short-term-culture filtrate and Ag85B are efficiently induced with DDA, this adjuvant was inefficient for the induction of immune responses to ESAT-6. Therefore, we investigated the modulatory effect of monophosphoryl lipid A (MPL), an immunomodulator which in different combinations has demonstrated strong adjuvant activity for both cellular and humoral immune responses. We show in the present study that vaccination with ESAT-6 delivered in a combination of MPL and DDA elicited a strong ESAT-6-specific T-cell response and protective immunity comparable to that achieved with Mycobacterium bovis BCG.

Stability of aluminium-containing adjuvants to autoclaving.

Aluminium phosphate adjuvant remained amorphous when autoclaved for 30 or 60 min at 121 degrees C. However, deprotonation and dehydration reactions occurred as evidenced by a decrease in the pH. The protein adsorption capacity, rate of acid neutralization at pH 2.5 and point of zero charge also decreased indicating that the deprotonation/dehydration reactions resulted in a decreased surface area. Autoclaving aluminium hydroxide adjuvant increased the degree of crystallinity as measured by the width at half height of the major band in the X-ray diffractogram. The pH decreased during autoclaving suggesting that the same deprotonation/dehydration reactions which reduced the surface area of aluminium phosphate adjuvant were responsible for the increased degree of crystallinity. These reactions also resulted in a reduced surface area as both the protein adsorption capacity and viscosity decreased following autoclaving.

The Production of Polyclonal Antibodies in Laboratory Animals. The Report and Recommendations of ECVAM Workshop 35.

This is the report of the thirty-fifth of a series of workshops organised by the European Centre for the Validation of Alternative Methods (ECVAM). ECVAM's main goal, as defined in 1993 by its Scientific Advisory Committee, is to promote the scientific and regulatory acceptance of alternative methods which are of importance to the biosciences and which reduce, refine or replace the use of laboratory animals. One of the first priorities set by ECVAM was the implementation of procedures which would enable it to become well informed about the state-of-the-art of non-animal test development and validation, and the potential for the possible incorporation of alternative tests into regulatory procedures. It was decided that this would be best achieved by the organisation of ECVAM workshops on specific topics, at which small groups of invited experts would review the current status of various types of in vitro tests and their potential uses, and make recommendations about the best ways forward (1). This joint ECVAM/FELASA (Federation of European Laboratory Animal Science Associations) workshop on The Immunisation of Laboratory Animals for the Production of Polyclonal Antibodies was held in Utrecht (The Netherlands), on 20-22 March 1998, under the co-chairmanship of Coenraad Hendriksen (RIVM, Bilthoven, The Netherlands) and Wim de Leeuw (Inspectorate for Health Protection, The Netherlands). The participants, all experts in the fields of immunology, laboratory animal science, or regulation, came from universities, industry and regulatory bodies. The aims of the workshop were: a) to discuss and evaluate current immunisation procedures for the production of polyclonal antibodies (including route of injection, animal species and adjuvant ); and b) to draft recommendations and guidelines to improve the immunisation procedures, with regard both to animal welfare and to the optimisation of immunisation protocols. This report summarises the outcome of the discussions and includes a number of recommendations and a set of draft guidelines (included in Appendix 1).

Adjuvant modulation of immune responses to tuberculosis subunit vaccines.

Mice were immunized with experimental subunit vaccines based on secreted antigens from Mycobacterium tuberculosis in a series of adjuvants, comprising incomplete Freund's adjuvant (IFA), dimethyl dioctadecyl ammoniumbromide (DDA), RIBI adjuvant, Quil-A saponin, and aluminum hydroxide. Immune responses induced by these vaccines were characterized by in vitro culture of primed cells, PCR analysis for cytokine mRNA, detection of specific immunoglobulin G isotypes induced, and monitoring of protective immunity to tuberculosis (TB). The study demonstrated marked differences in the immune responses induced by the different adjuvants and identified both IFA and DDA as efficient adjuvants for a TB subunit vaccine. Aluminum hydroxide, on the other hand, induced a Th2 response which increased the susceptibility of the animals to a subsequent TB challenge. DDA was further coadjuvanted with either the Th1-stimulating polymer poly(I-C) or the cytokines gamma interferon, interleukin 2 (IL-2), and IL-12. The addition of IL-12 was found to amplify a Th1 response in a dose-dependent manner and promoted a protective immune response against a virulent challenge. However, if the initial priming in the presence of IL-12 was followed by two booster injections of vaccine without IL-12, no improvement in long-term efficacy was found. This demonstrates the efficacy of DDA to promote an efficient immune response and suggests that IL-12 may accelerate this development, but not change the final outcome of a full vaccination regime.

Adjuvanticity of dimethyl dioctadecyl ammonium bromide, complete Freund's adjuvant and Corynebacterium parvum with respect to host immune response to coccidial antigens.

Immune response of chickens to Eimeria was investigated following immunization with coccidial antigens in combination with various immunological adjuvants. The adjuvanticity of dimethyl dioctadecyl ammonium bromide (DDA) was comparable to that of two other adjuvants known to stimulate cell-mediated immunity: complete Freund's adjuvant (CFA) and Corynebacterium parvum. However, DDA is considered less toxic than CFA and appeared to evoke longer-lasting immunity than C. parvum. In general, intramuscular immunization of chickens with merozoite antigens in DDA engendered higher protective immunity than did oral immunization. Immunization of chickens with merozoite antigens in CFA, DDA, or C. parvum engendered serum IgG and biliary secretory IgA (sIgA) antibody responses, as well as coccidial antigen-specific T-cell lymphoproliferation responses. This study presents evidence that DDA acts as an adjuvant for both coccidia antigen-specific antibody and T-cell immunity in the avian system.

Adjuvants--a balance between toxicity and adjuvanticity.

Adjuvants have been used to augment the immune response in experimental immunology as well as in practical vaccination for more than 60 years. The chemical nature of adjuvants, their mode of action and the profile of their side effects are highly variable. Some of the side effects can be ascribed to an unintentional stimulation of different mechanisms of the immune system whereas others may reflect general adverse pharmacological reactions. The most common adjuvants for human use today are still aluminium hydroxide, aluminium phosphate and calcium phosphate although oil emulsions, products from bacteria and their synthetic derivatives as well as liposomes have also been tested or used in humans. In recent years monophosphoryl lipid A, ISCOMs with Quil-A and Syntex adjuvant formulation (SAF) containing the threonyl derivative of muramyl dipeptide have been under consideration for use as adjuvants in humans. At present the choice of adjuvants for human vaccination reflects a compromise between a requirement for adjuvanticity and an acceptable low level of side effects.

Ultrasonic degradation of DNA.

Different results are obtained when DNA in aqueous solution and DNA in biological tissue are exposed to ultrasound. At intensities of ultrasound comparable to those applied clinically, ultrasonication is able to degrade purified DNA in aqueous solution, making ultrasonication a useful tool for preparing DNA fragments in vitro. Ultrasonic degradation of DNA in solution occurs by breaking hydrogen bonds and by single-strand and double-strand ruptures of the DNA helix. Two mechanisms are mainly responsible: cavitation and a thermal or mechanical effect. Stable cavitation is seen at low intensities of ultrasound. Increasing the intensity of the ultrasound above 2 W/cm2 is followed by increases in single-strand ruptures due to the creation of free radicals by transient cavitation. Following sonication, the distribution of the resulting DNA fragments approaches a lower size limit of 100-500 bp. Breaks in the DNA helix occur mainly between oxygen and carbon atoms, resulting in DNA fragments with a phosphorylated 5' end and a free alcohol at the 3' end. The relative lack of specificity in degrading the DNA helix makes ultrasonication a complementary alternative to the highly specific fragmentation obtained by restriction endonucleases.