Effects of immunological adjuvants on the mouse complement system--II. Anti-complementary effects of surface-active compounds

Lipophilic quaternary ammonium salt acts as a mucosal adjuvant when co-administered by the nasal route with vaccine antigens

Nasal administration of vaccines is an attractive approach which offers several significant advantages over traditional intramuscular vaccine delivery. These advantages include easier administration and induction of immune responses in the mucosal secretions of the body. In this study we describe a new potent nasal adjuvant, dimethyldioctadecylammonium bromide (DDA), that induces both mucosal and systemic immune responses when co-administered with diphtheria toxoid (DT), tetanus toxoid (TT) and BBG2Na antigens. In particular, we show that the nasal delivery of recombinant fragment (BBG2Na) of the G protein of respiratory syncytial virus (RSV) mixed with DDA induces both local and systemic anti-RSV immune responses and protects against viral challenge. Furthermore, we provide evidence that the DDA+BBG2Na vaccine does not induce lung immunopathology upon subsequent RSV challenge.

DDA as an immunological adjuvant

As compared to other adjuvants, DDA is a moderate or strong adjuvant for humoral responses and a strong adjuvant for CMI, especially DTH responses, against different types of antigens and in both laboratory animals and larger animals. DDA can collaborate with other immunomodulating compounds resulting in further enhanced responses. Mechanisms include interactions with both antigen and components of the host immune system and possibly, multiple beneficial effects contribute to the relatively strong adjuvanticity of DDA. Toxicity of DDA is not known but severe detrimental side effects were not seen. This adjuvant can be applied in experimental vaccines and in commercial vaccines for veterinary purposes, especially if cell-mediated immunity is considered to be important. In immunology, DDA can be of use to study T helper cells responsible for DTH responses (T helper cells type 1) and to characterize T helper cell epitopes on antigens (Snijder et al., 1992).

C5 does not play a major role in the immune response of mice to SRBC in vivo

The role of complement component C5 in the immune response of mice to sheep red blood cells (SRBC) was investigated. Congenic C5-sufficient and C5-deficient B10. D2 mice and genetically C5-deficient DBA/2 mice, as such or supplemented with C5-sufficient serum, were used as experimental animals. C5-substitution of the C5-deficient mice resulted in measurable C5 levels for days. The functional half-life of C5 in C5-deficient DBA/2 mice was about 21 h. No significant differences between the IgM-responses of C5-bearing and naive C5-deficient animals were observed. This suggests that C5 does not play a major role in the primary humoral immune response of mice in vivo, although C5 seems to do so in in vitro experiments, even with the same antigen. Antigen-induced C5-production by C5-deficient mice as one of the explanations of the in vitro/in vivo discrepancy could not be confirmed experimentally.

House dust extracts contain potent immunological adjuvants

A crude aqueous extract of house dust and two house dust subfractions were tested for adjuvant activity in a sensitivity assay performed in mice. Evidence is presented that house dust contains at least two potent immunological adjuvants. One of these, present in both subfractions, was probably endotoxin and acted in a complement-independent way. The immunostimulatory effect of the other adjuvant was abrogated by prior complement depletion of the animals. This apparently complement-dependent adjuvant needs further identification.