Cross-reactivity with avocado
In response to reports of an association between allergy to natural rubber latex and avocado, Ahlroth et al. investigated cross-reactive proteins between natural rubber latex and avocado in 1995 by using skin-prick tests with fresh avocado on 11 patients and the sera of 18 patients with known latex allergy for IgE antibodies. Fourteen of the 18 sera were found to have IgE antibodies binding to 17 distinct avocado proteins, with multiple immunoblot experiments and skin-prick test results (positive in 7 of 11 patients) revealing marked immunologic cross-reactivity between latex and avocado.8
In 1998, Chen et al. set out to identify the cross-sensitizing allergen between latex and avocado, with hevein suspected. The researchers looked at sera samples from 118 health care workers allergic to latex and 78 patients with spina bifida who were allergic to latex. They noted a robust correlation between the prevalence of seropositive IgE antibodies to avocado in the presence of hevein-specific IgE antibodies in both groups. All members in the spina bifida group and 91 (73%) of the health care workers had positive IgE antibodies to hevein and high IgE values to avocado. Additional results supported the conclusion that sensitization to avocado in the majority of people allergic to latex is engendered by IgE-binding epitopes found in hevein.9
A year later, Diaz-Perales et al. considered the potential relevance of chitinases and complex glycans as factors in the then newly described latex/food syndrome, particularly in avocado, banana, and chestnuts. The investigators culled extracts from 20 various plant foods as well as latex. In immunoblot inhibition assays, the primary allergen and class I chitinase in avocado, Prs a 1, and the latex extract potently or completely blocked IgE binding by these constituents. Polyclonal antibodies to chitinases and sera from patients with latex/fruit allergy responded to reactive proteins of about 30-45 kd (putative class I chitinases) in chestnut, cherimoya, kiwi, mango, papaya, passion fruit, tomato, and wheat flour extracts. The glycans complex was deemed to be irrelevant in latex/fruit cross-reactivity, but the researchers found the putative class I chitinases to be notable players in the latex/fruit syndrome.10
According to Wagner and Breitender, anywhere from 30%-50% of people with known latex allergy also evince a related hypersensitivity or allergy to various plant-derived foods, with avocado, banana, chestnut, kiwi, peach, tomato, potato, and bell pepper among the foods most frequently linked to latex/fruit syndrome. They summarize that several plant defense proteins have been shown to be involved in the syndrome, with the most prominent, class I chitinases with an N-terminal hevein-like domain, having been found to cross-react with hevein (Hev b 6.02), a major IgE-binding allergen for individuals allergic to latex. A beta-1,3-glucanase, a key latex allergen, has also shown cross-reactivity with proteins of bell pepper, and another significant latex allergen, Hev b 7, a patatin-like protein, cross-reacts with its analogous protein in potato.11