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. 2014 Nov 15:19:284.
doi: 10.11604/pamj.2014.19.284.4654. eCollection 2014.

High IgE sensitization to maize and rice pollen in the highlands of Madagascar

Ramavovololona  1 , Hélène Sénéchal  2 , Ange Andrianarisoa  3 , Vololona Rakotoarimanana  1 , Dominique Godfrin  4 , Gabriel Peltre  5 , Pascal Poncet  6 , Jean-Pierre Sutra  7
Affiliations

High IgE sensitization to maize and rice pollen in the highlands of Madagascar

Ramavovololona et al. Pan Afr Med J. .

Abstract

Introduction: Maize and rice are two crops constituting the main food supply in many under-developed and developing countries. Despite the large area devoted to the culture, the sensitization to the pollen from these plants is reported to be low and often considered as an occupational allergy.

Methods: Sixty five Malagasy pollen allergic patients were clinically and immunochemically investigated with regard to maize and rice pollen allergens. Pollen extracts were electrophoretically separated in 1 and 2 dimensions and IgE and IgG reactivities detected upon immunoblotting.

Results: When exploring the sensitization profile of Malagasy allergic patients to maize and rice pollen, it appears that a high proportion of these patients consulting during grass pollinating season were sensitized to both pollen as revealed by skin prick testing (62 vs. 59%) and IgE immunoblotting (85 vs. 40%). Several clinically relevant allergens were recognized by patients' serum IgE in maize and rice pollen extracts.

Conclusion: The high levels of maize and rice pollen sensitization should be related, in this tropical region, to a specific environmental exposure including i) a proximity of the population to the allergenic sources and ii) a putative exacerbating effect of a highly polluted urban atmosphere on pollen allergenicity. Cross-reactivities between wild and cultivated grasses and also between rice and maize pollen are involved as well as some specific maize sensitizations. The presence of dense urban and peri-urban agriculture, in various African regions and worldwide, could be a high environmental risk factor for people sensitive to maize pollen.

Keywords: IgE binding proteins; Madagascar; maize; pollen allergy; rice; urban and peri-urban agriculture.

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Figures

Figure 1
Figure 1
Correlations between IgE reactivities studied by SPT or IgE immunoblots for maize and rice pollen extracts. “Each dot (•) represents the result obtained with one patient; ✩: patient #60;”; A: SPT maize vs SPT rice; B: IgE immunoblot maize vs IgE immunoblot rice; C: SPT maize vs IgE immunoblot maize; D: SPT rice vs IgE immunoblot rice. SPT response was scored as + positive, if the largest wheal diameter was comprised between 70 to 80% greater than that was produced by the positive control, ++ between 80 to 90% and +++ between 90 to 100% Results of IgE immunoblot (see reactivity figure 2) are semi quantitatively expressed according to the intensity of the reaction as: -: negative; + positive low; ++ medium; +++ very high.
Figure 2
Figure 2
Most representative patterns from 1D IEF immunoblots for the 2 studied crop pollen extracts. Each strip corresponds to the IgE reactivity from individual allergic patient serum: (A) 49 sera were tested with blotted Zea mays pollen extract; (B) 42 sera were tested with blotted Oryza sativa pollen extracts and (C) Sera # 35 and #36 tested with Oryza sativa pollen extract; results of chimioluminescence obtained after a five-fold reduced exposure time. The IgG reactivity from allergic patient serum were tested (D) with blotted Zea mays pollen extract and (E) with Oryza sativa pollen extract; Strips #66 and #67: 2 European/Caucasian allergic patient sera; c: strip incubated with a non-allergy individual serum as control; T: negative control strip with buffer; at the top: serum number; on the left side: pI values
Figure 3
Figure 3
1D IEF Coomassie blue staining (A) and 1D IEF immunoblots (B) for the pollen of 6 varieties of Zea mays. (1): “Paysanne”, (2): “Volasoa”, (3): “NTS”, (4): “Meva”, (5): Europe, (6): “Tombotsoa”. The proteins from the pollen extracts separated by IEF and blotted were incubated with the serum #60 showing a high IgE reactivity (see Figure 1). pI values are indicated on the left side
Figure 4
Figure 4
2D analysis of the water-soluble proteins from Zea mays pollen. Pollen extract from Zea mays was submitted to an initial IEF separation followed by SDS-PAGE separations. The gels was either silver stained (A) or transferred on NCas and incubated with from pollen-sensitized patient serum #60. IgG (B) or IgE (C) binding were revealed using heavy chain specific Ab coupled to alkaline phosphatase followed by substrate. Boxes on each figure indicate groups of allergens recognized by IgE PAP. pI values (at the top) and Mr (kDa, on the right side) are indicated for each gel
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