Pollen and fungal spores

Outdoor Allergen Exposure

Outdoor allergen exposure, particularly pollen, and to a lesser extent fungal spores, cause seasonal allergies to many individuals worldwide. While it is not possible to totally avoid exposure to those allergens, it is feasible to minimize it. For this purpose, it is important to be aware of the types and levels of airborne pollen and fungal spores present outdoors day-to-day during various seasons of the year in different geographical locations.

The National Allergy Bureau (NAB), founded in the early 1960s, is a section American Academy of Allergy Asthma and Immunology dedicated to distribute pollen and spore counts nation wide. For this purpose, a number of certified stations collect outdoor air samples and provide pollen and spore count data to the community. Those data are included in the NAB web site and distributed to the public.

Other organizations in the world, for example, the British Aerobiology Federation in the United Kingdom, are analogous in scope to the NAB. Those organizations also report regular pollen and spore counts to the public. In addition, they promote the science of aerobiology at different levels.

Pollen and spore counting and identification are a time-consuming task to perform that requires a high level of expertise. The fast pace that modern society operates, together with the perception that the technology currently used to perform the counts and identification has not changed in many years, has contributed to a decline in the interest of young individuals to learn about the complex area of aerobiology.

To partially overcome the caveat mentioned above, various companies are developing systems and equipment to automate particle counting and identification to the best possible extent. Current efforts in that regard indicate that while automatic particle counting is feasible, proper identification of the particles is very challenging to perform using automatic approximations. Side-by-side comparisons of the pollen/spore counts and identification determined using automatic systems and by optical microscopy should be performed to validate and optimize technology.

Another benefit of the data derived from the completion of aerobiological surveys is to assist pharmaceutical companies conducting clinical trials that involve subjects with seasonal allergies. The purpose of these trials is to ascertain the safety, efficacy, and doses of particular medications or immunotherapy formulations before they can be marketed.

To conduct those clinical trials, individuals sensitized to particular outdoor allergens are selected and allocated into various groups, receiving either an active treatment or a placebo before or during particular pollination seasons. However, due to the limitations associated with natural exposure to outdoor allergens, environmental chambers are being developed and validated to perform exposure challenges under controlled conditions. While this approximation is optimal for the purpose of licensing and marketing particular products, it does not reflect the types and levels of exposure to outdoor allergens that individuals experience under natural conditions, which is ultimately responsible for sensitization and allergy symptoms.


Fungal Allergen Extracts

A large number of fungal allergen extracts for diagnosis and treatment of allergic diseases are available on the market. This can be confusing for the allergist/immunologist to properly select the most clinically relevant extracts.

While the proper selection of the appropriate extracts derived from particular genera and/or species is critical, other factors regarding the materials used to obtain those extracts also play a pivotal role responsible for the quality and consistency of fungal extracts. It is essential for the allergist/immunologist to properly understand those factors because they are ultimately responsible for a large variation in allergen content and potency among extracts of the same species produced by different manufacturers.

Fungi have a high level of genetic adaptability to the environment. They often mutate as a result of external stimuli. Those mutations and the direct effect of environmental conditions are associated with selective allergen production and the potential secretion of secondary metabolites, particularly mycotoxins and polysaccharides. Therefore, when fungi are cultured to manufacture allergen extracts, those factors must be controlled.

For the purpose of manufacturing allergen extracts, the fungal strains used in cultures should be obtained from accredited sources such as the American Type Culture Collection or the Centraalbureau voor Schimmelcultures. The selected strains must be grown under very strict conditions in compliance with specific regulations and general manufacturing guidelines.

The environmental factors responsible for fungal allergen production are many. The most relevant are the specific media formulations and culture conditions used to grow fungi. They are  considered intellectual property that belongs to the allergen manufacturing companies that obtain fungal extracts.

While materials derived from animals or plants are generally used to prepare laboratory culture media, they can potentially be allergenic and/or contain pathogenic microorganisms. Therefore, the media used to grow fungi must be carefully formulated to assure its safety.

The common culture conditions are static or under agitation. These conditions are responsible for the amount of oxygen available in the cultures, which affects the types and levels of allergens and secondary metabolites produced.

Once fungal cultures achieve a particular level of maturity, they are harvested and inactivated to assure that no live fungi are present in the materials. Proof on inactivation is required before further processing can be initiated.

The fungal materials used for the production of allergen extracts vary, depending on particular suppliers. Mycelia, culture filtrates, or both can be used to prepare allergen extracts.

Fungal allergen extracts should be obtained from one single reliable supplier. The allergist/immunologist should be aware of the fact that extracts derived from the same genera and species produced by different manufactures are not equivalent in terms of allergen content and potency.