When used simultaneously, latex proteins Hev b 2 and Hev b 7 reacted significantly with specific serum IgE in 80% of health care workers and 92% of spina bifida patients with latex allergy by ELISA technique, while this combination gave lower positivity when the RASTs were used. By the addition of Hev b 3, specific IgE was detected in all spina bifida patients with latex allergy. Both RASTs failed to show specific IgE in the control subjects, while the ELISA showed significant latex-specific IgE in 22% of controls.

I read with interest the paper entitled 'Latex allergy: low prevalence of immunoglobulin E to highly purified proteins Hev b 2 and Hev b 13 by Palosuo et al. [1]. The authors dispute that prevalence of sensitivity to Hev b 2 and Hev b 13 is sufficiently high for them to be classified as major latex allergens (450% binding to IgE of latexallergic individuals), contrary to the results from recent research [2, 3] and earlier reports [4,5]. They contend that only Hev b 5 and Hev b 6 are the major allergens among latex-allergic adults.In their paper, the authors isolated and purified Hev b 2 and Hev b 13 from natural rubber latex, and then went on to refine further what they describe as already highly purified proteins. Might these allergens have ended up being over purified?In the first instance, is it even possible to 'over-purify' a substance? If the subject of purification is homogeneous, then the answer is generally 'No'. But many allergens are heterogeneous by nature and occur as multiple molecular variants (isoforms). The International Union of Immunological Societies has provision for naming such isoallergens and their variants, although many more isoforms have been reported than officially classified. Except where the isoallergen is specified, a named allergen should refer to a balanced representation of its isoforms that are commonly encountered.Purifying something from a mixture is a matter of isolating the target substance and rejecting the remainder through a sequence of refining steps. There is no reason to doubt what the authors isolated at the end of their elaborate purification regime as indeed pure extracts of Hev b 2 and Hev b 13. But of no lesser importance here are the fractions that were thrown out in the course of purification. Were key isoallergens discarded en route?It is not always easy to distinguish between different isoallergens because changes in the DNA are often difficult to detect in the translated proteins. In the case of Hev b 2, however, the existence of isoforms is evident even from routine SDS-PAGE where it commonly appears as a doublet of about 35 kDa [6-8], with both protein bands similar enough to be recognized by the same monoclonal antibody [9]. Yagami et al.[8] resolved the Hev b 2 doublet into three distinct isoforms (from at least five molecular variants that exist [9]). The slower migrating (slightly larger) isoform was glycosylated, whereas the fast-migrating protein band yielded one glycosylated and another unglycosylated isoform. All three isoforms were shown by skin prick tests to be allergenic, but individual patients exhibited varying sensitization to the three variants. More recent work on Hev b 2 isoallergens indicate that glycans in the glycosylated isoforms play an active role in allergy, rather than being passive cross-reactive carbohydrate determinants [3, 10].The purification procedure described for Hev b 2 is closely similar to an earlier protocol (similar gel filtration technique, separation column, buffer and elution rate) from the same research group [11]...

No abstract