Aluminium Phosphate Vaccine Adjuvant | Uses, Suppliers, and Specifications
Aluminium phosphate adjuvant is an aluminium compound with the chemical composition AlPO4. The names of the two forms of aluminium-containing adjuvants, aluminium hydroxide adjuvant and aluminium phosphate adjuvant, do not correctly describe the adjuvant structures. X-ray diffraction and infrared spectroscopy identify aluminium hydroxide adjuvant as crystalline aluminium oxyhydroxide, AlO(OH). Aluminium phosphate adjuvant is amorphous to x-rays but its infrared spectrum identifies it as aluminium hydroxide in which phosphate has substituted for some hydroxyls. It is correctly termed amorphous aluminium hydroxyphosphate, Al(OH)x (PO4 )y . Unlike aluminium hydroxide adjuvant, it is not a stoichiometric compound. Rather, the degree of phosphate substitution for hydroxyl depends on the reactants and method of preparation.
Aluminium phosphate adjuvant is a white hydrogel that sediments slowly and forms a clear supernatant.
|Acidity/alkalinity||pH = 6.0-8.0|
|Al: P atomic ratio||1.0-1.4:1.0|
|Particle size distribution||Primary particles are plary with an average diameter of 50nm. The primary particles form aggregates of 1-10 µm|
|Point of zero charge||pH = 4.6-5.6, depending on the Al: P atomic ratio.|
|Protein binding capacity||>0.6mg lysozyme/mg equivalent A1203|
|Solubility||Soluble in mineral acids and alkali hydroxides.|
|X-ray diffractogram||Amorphous to x-rays|
Applications in Pharmaceutical Formulations
Aluminum phosphate an adsorbent and adjuvant for use in parenteral human and veterinary vaccines. It activates Th2 immune responses, including IgG and IgE antibody responses.
Aluminum-containing adjuvants, such as aluminum hydroxide adjuvant and aluminum phosphate adjuvant, contribute to the efficacy of many vaccines by potentiating the immune response. This effect was first noted by Glenny et al. in 1926  . Research since 1990 has elucidated many aspects of the physical and chemical properties of aluminum-containing adjuvants and has related these properties to their mechanism of immunopotentiation.
Safety and Regulatory Status
Aluminium phosphate adjuvant is intended for use in parenteral vaccines and is generally regarded as safe. GRAS listed. Accepted for use in human and veterinary vaccines in Europe and the USA. The limits for use in human vaccines are 0.85mg aluminium/dose (FDA) and 1.25mg aluminium/dose (WHO). There are no established limits for use in veterinary vaccines. Reported in the EPA TSCA Inventory.
Aluminium phosphate adjuvant may cause mild irritation, dryness, and dermatitis on skin contact. It may also cause redness, conjunctivitis, and short-term mild irritation on eye contact. Ingestion of large amounts of aluminium phosphate adjuvant may cause respiratory irritation with nausea, vomiting, and constipation. Inhalation is unlikely, although the dried product may cause respiratory irritation and cough. Type I hypersensitivity reactions following parenteral administration have also been reported.
Stability and Storage Conditions
Aluminum phosphate adjuvant is stable for at least 2 years when stored at 4-30 0C in well-scaled inert containers. It must not be allowed to freeze as the hydrated colloid structure will be irreversibly damaged.
Observe normal precautions appropriate to the circumstances and quantity of material handled. Eye protection and gloves are recommended.
The point of zero charge is related directly to the Al : P atomic ratio. Therefore, the substitution of additional phosphate groups for hydroxyl groups will lower the point of zero charge. Substitution of carbonate, sulfate, or borate ions for hydroxyl groups will also lower the point of zero charge.
Method of Manufacture
Aluminum phosphate adjuvant is formed by the reaction of a solution of aluminum chloride and phosphoric acid with alkali hydroxide.
Aluminum hydroxide adjuvant.
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