Liposome entrapped allergen reduces plasma histamine in sensitized mice.

Immunotherapy of allergic diseases is associated with problems of adverse systemic reactions. We have shown earlier that liposome entrapped allergen (LEA) is effective in inducing IgG response and restricting IgE response in immunized mice. This mode of treatment may be more effective and safer if it can prevent anaphylaxis. To determine this feature, mice were administered allergen preparations repeatedly and later challenged with the same allergen. Mice given liposomal preparation showed lower specific IgE response as compared to the mice given free allergen or alum adsorbed allergen of Artemisia scoparia. Specific IgG response was higher in mice immunized with LEA. The mice immunized with liposomal preparation survived whereas others injected with free allergen or alum adsorbed allergen died probably due to anaphylaxis. High levels of histamine were observed in mice injected with free allergen as compared to the mice injected LEA. The increase in plasma histamine level may be the cause of anaphylaxis during allergen challenge. In conclusion, LEA could be used as a safe and effective mode of immunotherapy for allergy diseases, since it reduces plasma histamine levels considerably thereby reducing the chances of anaphylaxis.

A study on antigenic and allergenic changes during storage in three different biological extracts.

The stability of three allergens common in tropical countries was evaluated under different storage conditions. Prosopis juliflora (PJ), Rhizopus nigricans (RN), and wheat dust (WD), were taken as representatives of various groups of allergens viz, pollen, fungi and dust. The extracts were stored in buffer containing phenol (0.4%) or glycerol (50%) at temperatures ranging from 4-55 degrees C for 15 to 60 days. Protein content of PJ extract was reduced remarkably when it was stored at 40 degrees C for 45 days. Thin layer isoelectric focusing and rocket immunoelectrophoresis of PJ showed that certain antigenic proteins degrade rapidly even at 25 degrees C as early as day 15. However, two to three proteins of PJ remain stable at a higher temperature (40 degrees C) for two months. Relative radioallergosorbent test (RAST) inhibition showed substantial loss of allergenic activity in all the three extracts, when stored at higher temperatures (25-55 degrees C) even for short durations, i.e., 15 days. Extracts (PJ and RN) containing 50% glycerol were found to be stable, retaining more than 50% activity, even when stored at 55 degrees C for 40 days, while extracts without glycerol lost more than 75% of their allergenic activity. However, addition of glycerol did not change the stability of wheat dust allergenic extract. The present findings indicate that allergenic extracts behave differently when stored. Hence, the stability of each extract should be determined individually.