# Kiwifruit Allergy--Molecular Basis, Diagnostics and Treatment
## 3 Protein Families
### Non-Specific Lipid Transfer Proteins  
Act c 10 and Act d 10 are characterized as non-specific lipid transfer proteins (nsLTPs). These proteins are known for their ability to bind and transport lipids as well as other hydrophobic ligands [75; 76; 77]. nsLTPs constitute a large protein family and are found in all land plants with a broad range of studied functions [78]. While the biological role of nsLTPs is still not fully understood, they are often involved in plant defense and reproductive mechanisms, can hinder fungal pathogen growth in vitro, and may have roles in antimicrobial activity and structural adaptation [75; 77; 79; 80].  
The plant nsLTP family consists of two subfamilies: the larger 9 kDa nsLTP1 and the smaller 7 kDa nsLTP2 [79; 81], with Act c 10 and Act d 10 being categorized as nsLTP1s. Both subfamilies have a similar structure, consisting of four \(\alpha\)-helices stabilized by four disulfide bridges. These bridges form an internal hydrophobic cavity that can hold a variety of lipids and other hydrophobic ligands [82]. While they are similar in terms of folding structure, neither the cysteine pairings nor the overall amino acid sequences are highly consistent between subfamilies [75; 83].  
nsLTPs are classified as parallegrens, and many members of this family are classified as potent food allergens, with peach allergen Pru p 3 considered the prototypic nsLTP due to its high sensitization capacity [75; 84; 85]. nsLTPs are highly stable and resistant to heat treatment and digestion, leading to severe allergic symptoms [75; 86]. Both Act c 10 and Act d 10 are considered minor kiwifruit allergens and were found in the seed extract but not the  
Figure 5: A-RISC index for inhalant and ingestion (**A**) profiling and (**B**) nsLTPs found in the ALEX\({}^{2}\) macroarray. Sequences were selected from the WHO/IUIS database. All A-RISC diagrams in this work are scaled against each other, such that red indicates a high likelihood of IgE-mediated cross-reactivity, green indicates a low likelihood, and intermediate colors suggest intermediate cross-reactivity.  
pulp extract of kiwifruit [79]. Thus far, Act c 10 has been structurally characterized [75]. In the initial study characterizing the allergenicity of Act d 10, 804 randomly chosen allergic patients were tested for IgE against Act d 10; of these, 21.1% (170 patients) had positive SPTs [87]. Additionally, 89.4% of these 170 patients were also positive for IgE to Pru p 3 [87]. The same study showed high IgE correlations between Act c 10 and Act d 10. Many individuals sensitized to Act c 10 were shown to also be IgE-positive to Act d 10. However, in vivo studies occasionally demonstrated a non-completely overlapping behavior of Act c 10 and Act d 10 [87]. Similarly, it was observed that a few patients (4.3% of 346 patients) were IgE-positive to Act c 10 but negative to Act d 10 isoforms, suggesting structural differences in one or more IgE-binding epitopes of these allergens [75; 87]. Interestingly, the A-RISC index (Figure 5B) predicts low cross-reactivity between Act d 10, Act c 10, and other nsLTP allergens.