Source of Bet v 1 loaded inhalable particles from birch revealed

 Allergenic proteins present in pollen grains, when inhaled, interact with the airways to cause an attack of asthma in susceptible humans. In one system, grass pollen grains rupture osmotically in rainfall, releasing allergen-containing inhalable particles into the atmosphere. In contrast, birch tree pollen grains do not rupture under these conditions, yet the major allergen, Bet v 1, has been detected in the atmosphere in inhalable particles of unknown origin. It is possible that Bet v 1 may diffuse from intact settled pollen grains and the allergenic material may again become airborne, interacting with settled fine particles from other sources prior to resuspension. This study investigates the mechanism for the release of birch pollen allergen-containing inhalable particles from pollen grains. We propose the hypothesis that (1) airborne birch pollen grains settle on nearby leaf surfaces; (2) then, following light rainfall, the grains germinate and, (3) later, pollen tubes burst, releasing inhalable particles carrying Bet v 1 into the atmospheric aerosol.   We used microscopic analyses of pollen behaviour following anther opening, a Burkard volumetric trap for pollen counts and a high volume air sampler with a two-stage cascade impactor for quantitative immunochemical analyses of Bet v 1. On dry days of high birch pollen count (48 grains/m³, 1.5 ng/m³ of Bet v 1), we found that the surfaces of birch leaves became coated with pollen. This ”pollen rain” is a source of secondary emission of allergens into the atmosphere. We observed that following light rainfall (<1 mm per day), about 80% of the birch pollen grains germinated, producing pollen tubes, especially in the sticky surface secretions of leaf glands. These pollen tubes may grow up to 300 μm in length prior to rupturing, each releasing about 400 starch granules coated with allergen molecules that may, after drying, be dispersed into the aerosol. On these days following light rainfall, the highest atmospheric levels of Bet v 1 (1.18 ng/m³) are associated with inhalable particles. Following heavy rainfall, both pollen and inhalable particles are washed from the atmosphere. Immunoprinting studies show that Bet v 1 is associated with starch granules rather than the smaller orbicules. Bet v 1 is present in the atmosphere in large particles, i.e. in particular pollen grains and in inhalable particles, i.e. in particular starch granules. Received: 28 May 1997 / Revision accepted: 18 August 1997     

Analysis of allergens in ambient aerosols: Comparison of areas subjected to different levels of air pollution

Recent studies describe interactions of pollen surfaces with aerosol particles; pollen surfaces undergo morphological changes and the release of allergens and allergenic fragments from the pollen can be enhanced. Thus allergens from pollen can be found in particle size fractions much smaller than undamaged pollen (<5 μm). This may explain allergic reactions in parts of the lungs which cannot be reached by undamaged pollen. In Switzerland the birch tree (betula verrucosa) major allergen Bet v 1 and the grass (phleum pratense) pollen major allergen Phl p 5 are of particular relevance for inducing pollinosis. In this study aerosols of different aerodynamic diameters were sampled by Andersen-Impactors over 18 months. Sampling areas are subjected to different levels of air pollution (Zürich, Switzerland, urban; Payerne, Switzerland, rural; Davos, Switzerland, alpine). Samples were scanned by electron microscopy and submitted to specific allergen assays (ELISA) for birch pollen major allergen Bet v 1 and grass pollen major allergen Phl p 5 respectively. Particle and major allergen concentrations were highest in Zürich, followed by Payerne and, significantly lower, Davos. Scanning electron microscopy investigations showed interactions of aerosols with pollen surfaces in Zürich and Payerne. The presence of Bet v 1 in smaller aerosol fractions was demonstrated in Zürich and Payerne some weeks before and after birch pollen was counted. An erratum to this article is available at .     

Ragweed and mugwort pollen in Szczecin, Poland

Ragweed (genus Ambrosia) and mugwort (Artemisia vulgaris) pollen grains are known to be very potent aeroallergens, often noted to enter into cross reactions. The aim of the study was to analyse ragweed and mugwort pollen release in Szczecin (western Poland) during the period 2000–2003. Measurements were performed by the volumetric and gravimetric method. Pollen seasons were defined as the periods of 90% of the total catch. Of the 4 years studied, the lowest concentration of ragweed pollen was observed in 2000. In 2000, the annual ragweed pollen count was very high, threefold higher than in 2001. There was a high Ambrosia pollen count in 2003, with the highest daily value of 84 grains/m³. The mugwort pollen season started in the third 10-day period of July and lasted to the end of August in all of the years studied. Analysis of pollen deposition from different Szczecin city’s districts showed that the highest exposure to ragweed pollen allergens occurred in the Majowe district, which is related to the presence of numerous plants of Ambrosia in that district. The mugwort pollen deposition was more abundant in the Żelechowa district, which is an area with villas and gardens. Statistically significant correlations were found between the ragweed pollen count in the air and the maximum wind speed, air temperature and relative humidity and between the mugwort pollen count in the air and air temperature and relative humidity.     

Localisation of allergens in ryegrass pollen and in airborne micronic particles

Summary In Melbourne, Australia, grass pollen allergens, especially from ryegrass, are a major cause of allergic hayfever and asthma. This review outlines recent developments in our understanding of how grass pollen allergens find their way into the atmosphere and how they are transported in particulate form. Much of this work has relied on antibody technology in immunological and immunocytochemical investigations. The localisation of allergens in situ has proved difficult due to their water-soluble character. Recently, allergens have been localised in developing ryegrass pollen by dryfixation, rapid-freeze and freeze-substitution techniques. This involved anthers being substituted in a mixture of aldehydes, organic solvents, and 2,2-dimethoxypropane. Incubation in dimethylsulfoxide prior to embedding in LR Gold resin provided good infiltration with freeze-substituted material. Immunogold-labelled sections show that the major allergens, Lol p 1 and Lol p 5, are synthesised in the pollen cytoplasm from the early bicellular stage, soon after the first starch granules are formed. From the early tricellular stage, Lol p 5 moves into the starch granules where it remains until maturity. Lol p 1 is localised in the cytoplasm of mature pollen grains. The incidence of airborne grass pollen, as measured in pollen traps, correlates with hayfever symptoms. Forecasting models which rely on rainfall and temperature data have been produced for the grass pollen (daily and seasonal) counts in Melbourne. Research over the past six years has shed light on the causes of grass-pollen-induced asthma. Micronic particles in the atmosphere may be starch granules originating from pollen grains osmotically ruptured by rainwater. Ultrastructural and immunological characterisation of micronic particles collected from outdoor air filters confirm the presence of airborne starch granules. These are loaded with grass pollen allergens, occur in the atmosphere especially after rainfall, and correlate significantly with instances of allergic asthma. Diesel particles might also play a role in the transmission of grass pollen allergens and thus become an extra asthma trigger. A variation in the mode of release of micronic particles occurs in other species, such as birch, where such particles are derived from burst birch pollen tubes. These particles are positive for Bet v 1 and are starch granules which are released into the atmosphere after light rain as a result of pollen germination on, e.g., leaves. After subsequent rupture of pollen tubes their contents are released when conditions become drier.Abbreviations DECP diesel exhaust carbon particles - DMP 2,2-dimethoxypropane - GPC grass pollen count - IgE immunoglobulin E - IgG immunoglobulin G - OGPS onset of the grass pollen season     

Analysis of allergens in ambient aerosols: Comparison of areas subjected to different levels of air pollution

Recent studies describe interactions of pollen surfaces with aerosol particles; pollen surfaces undergo morphological changes and the release of allergens and allergenic fragments from the pollen can be enhanced. Thus allergens from pollen can be found in particle size fractions much smaller than undamaged pollen (<5m). This may explain allergic reactions in parts of the lungs which cannot be reached by undamaged pollen. In Switzerland the birch tree (betula verrucosa) major allergen Bet v 1 and the grass (phleum pratense) pollen major allergen Phl p 5 are of particular relevance for inducing pollinosis. In this study aerosols of different aerodynamic diameters were sampled by Andersen-Impactors over 18 months. Sampling areas are subjected to different levels of air pollution (Zürich, Switzerland, urban; Payerne, Switzerland, rural: Davos, Switzerland, alpine). Samples were scanned by electron microscopy and submitted to specific allergen assays (ELISA) for birch pollen major allergen Bet v 1 and grass pollen major allergen Phl p 5 respectively. Particle and major allergen concentrations were highest in Zürich, followed by Payerne and, significantly lower, Davos. Scanning electron microscopy investigations showed interactions of aerosols with pollen surfaces in Zürich and Payerne. The presence of Bet v 1 in smaller aerosol fractions was demonstrated in Zürich and Payerne some weeks before and after birch pollen was counted.     

Airborne birch and oak pollen grains and birch pollen allergens at a common sampling station in Stockholm

In the present study, the airborne concentrations of birch and oak pollen grains and birch pollen allergens have been recorded in samples from a common sampling station in Stockholm. The sampling period was between April 22^nd and May 31^st 2003. The objectives were to evaluate if analysis of allergen particles in parallel with pollen grains would be relevant to aid subjects suffering from pollinosis. Days with low birch pollen counts had relatively high nominal allergen concentrations in the beginning of the sampling period. The birch pollen grain concentration peaks, during the dry pollination culmination interval in the middle of the period, were associated with correspondingly lower nominal concentrations of allergens than grains. At the end of the sampling period very high nominal amounts of allergen appeared, as reflected by high concentrations of oak pollen grains. The high allergen concentrations were obtained as a result of inherent cross‐reactivity of anti‐ Bet v 1 antibodies with Que a antigens, which are immunologically analogous with Bet v 1. Allergen concentrations increased and decreased after light and heavy rain, respectively. Results obtained indicate that adding a pollen count forecast with allergen concentration data should aid pollen allergic subjects to avoid particulate allergens which might be expected to penetrate more easily than pollen grains into indoor environments.     

Airborne pollen of Borassus flabellifer: Quantification of allergen and antigen

Airborne pollen grains of Borassus flabellifer were recorded at Madhyamgram, during February to June 1995–1996 commensurate with the plants flowering season. The following year (1996–1997), the exposed Burkard tape segments with the optimal and minimal daily concentrations were divided into two longitudinal equal halves. For each segment, after immunoblotting, one half was incubated with human sera having high IgE titer against Borassus, and the other half with anti-Borassus rabbit sera for the detection of allergen and antigen respectively. Antigen detection was performed by general immunoblotting method, whereas the allergens were detected by chemiluminescence. The occurrence of the pollen grains in air was compared and correlated with that of the allergen and antigen. The number of allergen and antigen spots were always found to be higher than airborne pollen with great size variation due to the presence of exine free protein particles originating from the pollen grains. The number of allergen spots was always lower than the antigen spots. The occurrence of pollen grains and antigen spots showed stronger positive correlation compared with allergen spots. The peak hours for the occurrence of pollen grains, allergens and antigens were recorded. It is evident from this study that the application of direct aeroallergen monitoring method will be highly useful in allergological research.     

Proteomic analysis of major and minor allergens from isolated pollen cytoplasmic granules

Grass pollen is one of the most important vectors of aeroallergens. Under atmospheric conditions, pollen grains can release pollen cytoplasmic granules (PCGs). The allergens associated with these intrinsic subfractions induce, in laboratory animals as well as in asthmatic patients, allergic and inflammatory responses. The objectives of this study were to characterize the PCGs' intrinsic allergens and to compare them with those of pollen grains. The water-soluble proteins were extracted from pollen grains and their PCGs. IgE-binding proteins were analyzed and characterized through an allergomic strategy: 1- and 2-dimensional gel electrophoresis (1-DE and 2-DE), immunoblotting, using grass-pollen-sensitized patient sera, mass spectrometry (MS) analysis, and database searching. Several of the allergens listed in the IUIS nomenclature, Phl p 1, 4, 5, 6, and 12, were detected in pollen and PCG extracts, whereas Phl p 11 was found only in PCGs, and Phl p 2 as well as Phl p 13 were found only in pollen extract. Some other allergens not listed in the IUIS nomenclature were also characterized in both pollen and PCG extracts. Since the major grass pollen allergens were found in PCGs and because of their small size, these submicronic particles should be considered as very potent sensitizing and challenging respirable vectors of allergens.     

The role of allergenic proteins Pla a 1 and Pla a 2 in the germination of Platanus acerifolia pollen grains

Platanus acerifolia (Aiton) Willdenow is a plane tree, widely grown as an ornamental tree in many cities of the United States and Western Europe, which has become an important source of airborne allergens in our cities. The aim of the present study is to immunolocalize the major allergens in the pollen grain and to examine their potential function in the fertilization process. Observations were made in mature and hydrated, activated pollen of P. acerifolia for 5, 15, 30 min and 2 h in the germination medium. Specimens were fixed using freezing protocols for transmission electron microscopy (TEM). For immunogold labelling, cryosections and resin-embedded ultrathin sections were incubated using rabbit antisera against the purified pollen allergens Pla a 1 and Pla a 2. Elution of P. acerifolia allergens took place after 5 min of pollen incubation in buffered medium. Intense labelling of Pla a 1 and Pla a 2 was detected after pollen exudates were released. In pollen grains, Pla a 1 was predominantly localized in concentric cisternae of the endoplasmic reticulum (ER), situated between the vegetative nucleus and the generative cell, and was released from pollen grains 5 min after hydration; cytoplasmic localization decreased 15 min after hydration. In pollen grains, glycoprotein Pla a 2 was abundant in association with Golgi cisternae and vesicles situated in the apertural periphery of the mature pollen grains. Pla a 2 proteins were also detected in ER and in the generative cell wall. Immunolabelling of Pla a 2 decreased 5 min after pollen hydration but was again intense after 15–30 min in germination medium, presumably as a consequence of renewed expression and glycosylation of this protein. Pla a 1 belongs to a new class of allergens related to proteinaceous invertase and pectin methyl esterase inhibitors (PII, PMEI) which could be involved in membrane protection and pectin de-esterification control during pollen hydration. Pla a 2 has an exopolygalacturonase (PG) enzymatic activity consistent with pollen-stigma adhesion mechanisms or compatibility systems. Moreover, the expression of Pla a 2 found 15–30 min after hydration might contribute to pollen-tube growth and the modification of transmitting tissue cell walls. The abundant production and elution of Pla a 1 and Pla a 2 proteins may alter the environment in which pollen tube elongation occurs, thus promoting a potential crosstalk between the pollen and the gynoecium.     

The combination of airborne pollen and allergen quantification to reliably assess the real pollinosis risk in different bioclimatic areas

Exposure to allergens represents a key factor among the environmental determinants of asthma. The most common information available for pollinosis patients is the concentration of pollen grains in the bioaerosol and their temporal distribution. However, in recent years, discordance between pollen concentrations and allergic symptoms has been detected. The purpose of this research is to evaluate the relationship between pollen counts and the atmospheric aeroallergen concentrations in different Spanish bioclimatic areas. For the monitoring of allergen content in the air, a quantitative antigen–antibody technique combined with the Cyclone sampling methodology was used. The study was conducted during 2007 by considering some of the most common allergens that induce pollinosis in each area: Platanus and Urticaceae in Ourense and Cartagena, and Poaceae in Ourense and León. In Ourense, pollen counts and aeroallergen concentrations coincided for the three pollen types studied, and the pollen and allergen data associated with the meteorological factors were highly significant for the pollen counts. In Cartagena (for Platanus and Urticaceae) and León (for Poaceae), the low correlations between pollen counts and allergen concentrations obtained could be due to the specific bioclimatic conditions. In contrast, the higher allergen concentrations found in the atmosphere in Cartagena and León compared to Ourense could be related to the existing pollutant levels there, inducing a higher expression of plant pathogenesis-related proteins in the plants of polluted cities. The combination of pollen counts and allergen quantification must be assessed to reliably estimate exposure of allergic people to allergens in different bioclimatic areas.     

Aeroallergens, Allergic Disease, and Climate Change: Impacts and Adaptation

Recent research has shown that there are many effects of climate change on aeroallergens and thus allergic diseases in humans. Increased atmospheric carbon dioxide concentration acts as a fertilizer for plant growth. The fertilizing effects of carbon dioxide, as well as increased temperatures from climate change, increase pollen production and the allergen content of pollen grains. In addition, higher temperatures are changing the timing and duration of the pollen season. As regional climates change, plants can move into new areas and changes in atmospheric circulation can blow pollen- and spore-containing dust to new areas, thus introducing people to allergens to which they have not been exposed previously. Climate change also influences the concentrations of airborne pollutants, which alone, and in conjunction with aeroallergens, can exacerbate asthma or other respiratory illnesses. The few epidemiological analyses of meteorological factors, aeroallergens, and allergic diseases demonstrate the pathways through which climate can exert its influence on aeroallergens and allergic diseases. In addition to the need for more research, there is the imperative to take preventive and adaptive actions to address the onset and exacerbation of allergic diseases associated with climate variability and change.     

Electron tomography of structures in the wall of hazel pollen grains

The three-dimensional structure of channels and bacula cavities in the wall of hazel pollen grains was investigated by automated electron tomography in order to explore their role in the release of allergen proteins from the pollen grains. 3D reconstructions of 100–150 nm thick resin-embedded sections, stabilized by thin platinum–carbon coating, revealed that the channels aimed directly towards the surface of the grain and that the bacula cavities were randomly sized and merged into larger ensembles. The number and the dimensions of the ensembles were quantitatively determined by neighboring voxel analysis on thresholded reconstructed volumes. To simulate the allergen release, allergen proteins were approximated by a hard sphere model of a diameter corresponding to the largest dimension of the known 3D structure of the major birch allergen, Bet v 1, whose amino acid sequence is highly similar to the amino acid sequence of the major hazel allergen, Cor a 1. The analysis of positions where the hard sphere fits into the resolved channels and bacula cavity structures revealed that unbound allergens could freely traverse through the channels and that the bacula cavities support the path of the allergens towards the surface of the grain.     

Localization and release of allergens from tapetum and pollen grains ofBetula pendula

Summary Although intact pollen grains are assumed to be the primary carrier of pollen allergens, specific immunoreactive components have been found in other aerosol fractions, e.g., starch grains and remains of tapetal cells Cryo-scanning-electron-microscopy results demonstrate the presence of a clear network of strands connecting the tapetum with the microspores. The distribution of protein in tapetal orbicules, pollen wall, and pollen cytoplasm was tested by histochemical stains for light microscopy and transmission electron microscopy. The protein is mainly localized at the apertures and starch grains in the cytoplasm of pollen and in the core and on the surface of tapetal orbicules. Monoclonal antibodies Bv-10, BIP3, and BIP4 have been used to locate the cellular sites of pollen and tapetal allergens inBetula pendula (syn.B. verrucosa). The application of rapid-freeze fixation prevented relocation of allergens from their native sites. The allergens are predominantly found in the starch grains and to lesser extent in the exine. We also tested interactions between mature birch pollen and human fluids: saliva, nostrils fluid, and eyes solution. The aim was to mimic more closely the in vivo situation during allergenic response. In all cases we observed several pollen grains that were burst and had released their cytoplasmic contents. In the nose the allergens are released from the pollen within minutes. In rhinitis, nasal pH is increased from the normal pH 6.0 to 8.0. When we used nasal fluid at pH 8.0, the number of ruptured pollen grains increased. The mechanism that might induce formation of small allergen-bearing particles from living plant cells is discussed.     

Particle size of airborne mouse crude and defined allergens

Laboratory animal allergy is a serious occupational diseases of many workers and scientists engaged in animal experimentation. Control measures depend upon characterization of allergens including airborne particles. This study measured the particle size of crude mouse urine and pelt aeroallergens generated in mouse housing rooms and compared them with mouse serum albumin, a defined major allergen. Allergens were detected by specific immunological methods. Most crude and defined allergens (74.5-86.4%) concentrated on a filter with a retention size greater than 7 microns. In distrubed air, allergen concentration increased 1.4 (albumin) to 5 (crude) fold and the proportion of small particles increased from 1.4% in calm air to 4.5% in distrubed air. This information on the generation and size distribution of aeroallergens will be important in the development of effective counter measures.     

Cellular localization of water soluble, allergenic proteins in rye-grass (Lolium perenne) pollen using monoclonal and specific IgE antibodies with immunogold probes

Summary A postembedding method has been developed for localizing water soluble allergens in rye-grass pollen. This uses dry fixation in glutaraldehyde vapour, followed by 2,2-dimethoxypropane, prior to a 100% ethanol series leading into embedment in LR Gold. This has allowed the attachment of specific monoclonal antibodies to the allergen, which are themselves probed with specific immunogold labels to the antibodies. Wall and cytoplasmic sites have been identified, representing an improvement of fixation and localization of allergens over previous studies employing polyclonal, broad spectrum antibodies.Rye-grass allergens are labelled in mature pollen grains in the exine (tectum, nexine and central chamber), and in the electron opaque areas of the cytoplasm, especially mitochondria. The allergens are absent from the intine, polysaccharide (P) particles, amyloplasts, Golgi bodies and endoplasmic reticulum. IgE antibodies derived from humans allergic to rye-grass pollen, bind to similar sites in the cytoplasm but only to the outer surface of the pollen grain wall. This method now provides a valuable tool for further developmental studies on the pollen grains, in order to establish the site/s of synthesis of the allergens.     

New immunodiagnostic system

We have developed a new immunodiagnostic system whichmeasures personal allergen exposure and which can beused to identify allergens.Personal exposure is directly sampled using inertialimpaction filters which fit just inside the nose andcollect particles (mainly >5 µm) inhaled duringnormal respiration. These samplers provide both anindex of personal exposure as well as being aninexpensive and portable sampling system.The particles are captured on adhesive tapes which arethen laminated with a protein-binding membrane. Theallergens eluting from the particles are bound by the membrane in theperiphery of each particle. The systemthen uses either allergen-specific monoclonalantibodies or the subject's IgE as primary probes toimmuno-label the `halo' of allergen around individualallergen-containing particles. Such an assay is verysensitive and can detect a single particle carryingallergens. In addition, the system providesinformation on the size, shape and allergen content ofthe particles. Because the particles carryingallergens can be seen, high resolution video images ofpollen grains and fungal spores can be subjected to atraditional morphological study or a range of featureextraction routines. This information can be comparedto a database of some known allergenic pollen grainsand fungal spores which we have also assembled tofacilitate their identification.When using monoclonal antibodies as the probe, thesystem determines the amount of allergen the subjectis exposed to and the characteristics of the particles(size, shape, etc). When using the subject's IgE as theprobe, the system allows visualisation of the allergensources that an individual is allergic to. The systemmay have clinical applications in quantifying personalexposure as well as identifying allergens anddetermining exposure to unsuspected allergens.     

Degradation of soluble proteins including some allergens in brown rice grains by endogenous proteolytic activity during germination and heat-processing

The effect of germination and subsequent heat-processing on the degradation of soluble proteins, including some allergenic proteins, in brown rice grains was investigated. The content of soluble proteins, including 14-16-kDa and 26-kDa allergens, in the germinated and processed brown rice grains (GPR) was much lower than that of non-germinated brown rice. These proteins in brown rice grains were also much lower after subsequent heat-processing during the manufacturing process. The protease activity of germinated brown rice (GR) was detected and increased 1.5 times after germination. The optimum pH values for degradation of the 26-kDa and 14-16-kDa allergens in the GR grains were 4 and between 5 and 7, respectively. These results suggest that the decrease in the soluble proteins and allergens was induced in part by proteolytic degradation. The presence of a detergent enhanced the proteolytic degradation of the soluble proteins, especially of the 26-kDa allergen, in the brown rice grains. The degradation of the 26-kDa allergen was weakly inhibited by NEM, suggesting cysteine protease(s) may have been involved in its degradation. These results suggest that the two abundant allergens were degraded in a different manner and probably by different proteases in the grains during germination.     

Grass-pollen allergen carried by the smaller micronic aerosol fraction

Aerodynamically, grass-pollen grains should be filtered from the inhaled air in the nose. They should not penetrate into the deeper airways (bronchi, bronchioles). Yet, bronchial symptoms are not seldom seen in patients suffering from pollinosis. Therefore, the grass-pollen allergenic activity of the smaller, paucimicronic atmospheric aerosol fraction was studied. Outdoor airborne particulate matter was collected and separated into fractions according to aerodynamic sizes (> 10; 4.9–10; 2.7–4.9; 1.3–2.7; 0.6–1.3; < 0.6 μm), with a Cascade Impactor mounted on top of a high volume sampler. The different fractions were tested for the presence of grass-pollen allergenic activity using a RAST-inhibition assay. The results show that on days with a relatively high grass-pollen count, a considerable amount of allergen was present in all the smaller micronic aerosol fractions.     

Airborne dispersal ofCecropia peltata L. (Moraceae) pollen,a neotropical species,in the vicinity of Caracas,Venezuela

In this paper, airborne dispersion of the pollen ofCecropia peltata L. (Moraceae) in a location close to the Equator is described. The Cecropias are fast-growing pioneer trees unique to the Neotropics, where they grow within a large altitude range, from Mexico to Brazil.Cecropia pollen was the most abundant grain throughout the year. The highest recovery occurred during April–May. As widely distributed members of the Moraceae family and because of their small pollen size, the Cecropias are prime suspects for being the source of inhalant allergens. The numbers ofCecropia airborne pollen grains that were recorded are well above those deemed necessary for human sensitization.     

Transgenic ryegrasses (Lolium spp.) with down-regulation of main pollen allergens

Ryegrass pollen (Lolium species) is a widespread source of air-borne allergens and is a major cause of hayfever and seasonal allergic asthma, which affect approximately 25% of the population in cool temperate climates. The main allergens of ryegrass pollen are the proteins Lol p 1 and Lol p 2. These proteins belong to two major classes of grass pollen allergens to which over 90% of pollen-allergic patients are sensitive. The functional role in planta of these pollen allergen proteins remains largely unknown. Here we describe the generation and analysis of transgenic plants with reduced levels of the main ryegrass pollen allergens, Lol p 1 and Lol p 2 in the most important worldwide cultivated ryegrass species, L. perenne and L. multiflorum. These transgenic plants will allow the study of the functional role in planta of these pollen proteins and the determination of potential for development of hypo-allergenic ryegrass cultivars.