Abstract
Background:
Dermatophagoides pteronyssinus (Dp), with its major allergen Der p 2, triggers allergy symptoms in various populations worldwide, but their IgE-binding properties among Filipinos remain limited.
Objectives:
This study investigated the IgE reactivity of Dp and its major allergen rDer p 2 in a cohort of allergic and nonallergic Filipinos from Ilocos Norte, Philippines.
Methods:
Using enzyme-linked immunosorbent assay, total IgE (n = 960), Dp-specific IgE (n = 247), and rDer p 2-specific IgE (n = 90) levels were determined. The odds ratio was used to determine the association between Dp and rDer p 2 specific IgE among selected demographic variables. An inhibition enzyme-linked immunosorbent assay was used to measure the inhibition of rDer p 2 against Dp allergen extract.
Results:
Among 171 allergic cases, mean IgE levels were significantly higher (P < 0.01) than in 76 nonallergic controls. Of the allergic cases, 85 individuals (49.71%) were sensitized to Dp allergens, with 68.89% of these also displaying sensitization to rDer p 2. On average, rDer p 2 inhibited IgE binding to Dp allergens by approximately 36%. Significant associations were found between Dp sensitization and age (P < 0.01), male gender (P = 0.01), and between rDer p 2-sensitization and atopy (P = 0.01).
Conclusion:
This study has shown the importance of Dp extract and its major allergen rDer p 2 as a source of allergen that sensitizes atopic Filipino individuals. Consequently, the inclusion of Dp and rDer p 2 in the panel of reagents utilized in immunodiagnostic and immunotherapeutic strategies and interventions for the local Filipino population sensitized to house dust mites is highly recommended.
Keywords: Allergy, atopy, dermatophagoides pteronyssinus, Der p 2, IgE
1. Introduction
Allergic diseases have significantly contributed to morbidity and mortality rates across global populations. Among them, atopic dermatitis (AD), allergic asthma (AA), and allergic rhinitis (AR) are prevalent chronic disorders that profoundly impact the quality of life of affected individuals [1, 2]. The primary culprit behind these conditions is specific antigenic molecules known as allergens that induce an abnormal immune response marked by increased production of immunoglobulin ε (IgE) [3].
Among all allergen sources, house dust mites (HDMs) stand as one of the primary causes of chronic disorders, which also play a crucial role as disease triggers, posing a significant global health threat. HDM allergens sensitize and induce allergies in a substantial number of atopic individuals worldwide, with at most 1% to 2% of the global population being sensitized and affects 65 to 130 million people [4]. Dermatophagoides pteronyssinus (Dp), a significant HDM species with around 40 allergens, shows varying sensitization rates across populations that even exceed up to 90% in various countries [5].
Of Dp’s multiple allergens, the group 2 allergen, Der p 2, dominates as the primary cause of over 80% of the IgE-mediated immune responses in Dp-sensitized individuals [6]. Der p 2, a 15 kDa class C2 Niemann-Pick protein homolog that is present in Dp fecal pellets, triggers hypersensitivity reactions in sensitized individuals when inhaled [7]. Although the prevalence of sensitization to Dp allergens and Der p 2 is well-documented in various populations [5, 8], their clinical significance as triggers of allergies in the Filipino population remains poorly understood. Hence, this study examines the IgE reactivity of individuals from the Ilocos Norte Region, Philippines, measuring total IgE, Dp-specific IgE, and rDer p 2-specific IgE levels, and exploring associations with demographics and clinical presentations.
2. Methods
2.1. Study design, subjects, and blood extraction
This case–control study, approved by the Ethics Review Committee of the Graduate School, University of Santo Tomas, Manila, Philippines (protocol number GS2019 PNEX004), determined the minimum required sample size for statistical power using G*Power 3.1.9.7. It includes individuals with and without self-reported symptoms of AA, AR, or AD who had resided, worked, and studied in Laoag City, Ilocos Norte, Philippines, for over 2 years. Recruitment took place at Northwestern University in Laoag City, Ilocos Norte, Philippines, with eligibility assessed through questionnaires and was supplemented by interviews conducted by physicians. Exclusion criteria encompassed pregnancy, breastfeeding, and current use of antihistamines, corticosteroids, or anti-inflammatory or immunosuppressive medications. In total, 960 eligible participants provided informed or parental consent and completed modified standardized questionnaires based on the International Study of Asthma and Allergies in Childhood to determine their demographics and allergy phenotype.
About 5 mL of peripheral blood samples were collected from participants via venipuncture. Blood plasma samples were subsequently isolated by centrifugation at 6000 rpm for 10 minutes, divided into ~1.5 mL aliquots, and stored at –80 °C until use.
2.2. Total IgE ELISA
For the quantification of total plasma IgE concentration, a sandwich enzyme-linked immunosorbent assay (ELISA) was conducted using a Human IgE ELISA kit (LABISKOMA, Republic of Korea) following the specified protocol with slight adjustments. In brief, serially diluted standards were prepared using 1% bovine serum albumin (BSA; Fisher Scientific, MA, USA) in 1X phosphate-buffered saline (PBS) as the assay diluent. Each well of 96-well flat-bottom plates (Corning Costar Inc., NY, USA) was coated with 100 µL of 10 µg/mL of antihuman IgE, reconstituted with 10 mL of 50 mM carbonate-bicarbonate coating buffer (pH 9.6), and incubated at 4 °C overnight (~16 hours) on a horizontal shaker. Plates underwent three washes with 1X PBS containing 0.05% Tween 20 (Loba Chemie, India) using an ELISA plate washer (Lisawash 3000, India). Wells were subsequently blocked with 100 µL of the assay diluent and incubated on a shaker at room temperature (25 °C) for at least 1 hour. Next, wells were incubated with 100 µL of each standard dilution or plasma samples in duplicate for 2 hours at room temperature. Following this, the wells were loaded with 100 µL of a 1000:1 solution of assay diluent and a reconstituted 10 µg/mL antihuman IgE detection antibody conjugated with horseradish peroxidase (HRP) and incubated for at least 1 hour at room temperature. The reaction was then detected using 100 µL of 3,3’,5,5’-tetramethylbenzidine (TMB; Sigma-Aldrich, Saint Louis, MO, USA) solution. The absorbance at 605 nm was measured 30 minutes after the addition of TMB using a microplate reader (SPECTROstar Nano, USA). The concentration curve of the standards was employed to calculate the IgE concentration of the samples in IU/mL [9], Individuals with self-reported allergies and plasma total IgE ≥100 IU/mL were categorized as allergic cases, while self-reported non-allergic individuals with plasma total IgE <100 IU/mL were considered nonallergic controls [10, 11].
2.3. Dp extract preparation
Dp house dust mites stored at −80 °C were macerated in 1X PBS using a precooled mortar and pestle for 30 minutes. Phenylmethylsulfonyl fluoride was added at a ratio of 1 µL per mL of 1X PBS during the maceration. The mixture was incubated at 4 °C with gentle shaking for 16 hours, followed by centrifugation at 14,000 rpm for 20 minutes (DLAB Scientific Co., Ltd., Beijing, China) to isolate the supernatant. Total protein concentration was quantified by Bradford assay. In brief, a standard stock solution of 4 mg BSA (Fisher Scientific, USA) in 2 mL 1X PBS was serially diluted elevenfold in 200 µL aliquots, alongside the extract, which was also diluted 1:2 and 1:10 with 1X PBS. Subsequently, 10 µL of each standard and extract dilutions were loaded onto separate wells, to which 200 µL of Bradford reagent was added. The reaction was incubated at room temperature for at least 5 minutes before spectrophotometric analysis at 595 nm using a microplate reader (SPECTROstar Nano, USA).
2.4. Allergen-specific ELISA
Specific IgE levels for Dp extract and rDer p 2 were quantified using indirect ELISA. In summary, 96-well plates were coated with diluted Dp extract (10 µg/mL) or rDer p 2 (5 µg/mL) and incubated overnight at 4 °C. After washing with PBS containing 0.05% Tween 20, each well was blocked and incubated for 1 hour. Duplicate case and control plasma samples, diluted 1:5, were incubated for 2 hours. For rDer p 2-specific IgE, case plasma had Dp-specific IgE exceeding mean + 1 SD of control Dp-specific IgE. Each well received a 1000:1 diluted solution of an antihuman IgE detection antibody with HRP. After at least 1 hour of incubation, 50 µL of TMB was added per well. Positive Dp allergen and rDer p 2-sensitization were determined based on mean + 1 SD of blank-corrected absorbance readings at 605 nm from selected controls (n = 76 for Dp allergen-specific and n = 45 for rDer p 2-specific IgE quantification) [12].
2.5. Inhibition assay
To assess rDer p 2’s capacity to inhibit IgE reactivity, ELISA was performed using 7 plasma samples positive for both Dp extract and rDer p 2. All procedures were conducted at room temperature unless specified. The Dp extract, diluted to a concentration of 10 µg/mL using the previously mentioned coating buffer, was coated onto a Corning Costar Inc. ELISA plate at 50 µL per well and incubated overnight at 4 °C. Simultaneously, each plasma sample was preabsorbed with 1 µL of 5 µg/mL rDer p 2 and incubated overnight at 4 °C. The incubated plate was blocked with 1% BSA (Fisher Scientific, USA) diluted in 1X PBS for 1 hour. The preabsorbed plasma, along with the corresponding unabsorbed plasma, were added to the plate in duplicates and incubated for 2 hours. Afterward, 100 µL of diluted HRP-conjugated antihuman IgE (brand not specified) was added per well and was incubated for 1 hour. Lastly, a colorimetric reaction was performed by adding 100 µL of TMB (Sigma-Aldrich) per well. Plates were washed 3 times with 1X PBS with 0.05% Tween 20 (Loba Chemie, PVT, LTD) using an ELISA plate washer (Lisawash 3000, India) in between steps. Absorbance at 605 nm was read 30 mins after the addition of TMB using a SPECTROstar Nano microplate reader (USA) [13].
2.6. Statistical tests
Data collected encompassed both numerical variables (age, total IgE, and allergen-specific IgE concentrations) and categorical variables (name, address, sex, smoking habits, mode of birth, familial history of allergy, presence of pets at home, and allergy phenotype for cases). Data analysis and statistical procedures were carried out using RStudio 2022-12.0+353 (R 4.2.2) and Microsoft Excel. The Shapiro-Wilk test determined data normality. Differences between mean total IgE and mean relative allergen-specific IgE in cases versus controls were evaluated using Welch’s two-sample t test. To identify variations in median total plasma IgE levels among different allergic phenotypes, the Kruskal–Wallis test was employed. Odds ratio (OR) measured associations between demographics and Dp or rDer p 2 sensitizations, with ORs computed post hoc to determine association strength. Statistical significance was defined as P value < 0.05, and no corrections for multiple testing were applied.
3. Results
3.1. Allergic and nonallergic subjects’ demographic profiles
Among the 960 study participants, 72% (690 individuals) self-reported allergies, while 28% (270 individuals) were nonallergic based on initial questionnaires. Secondary screening using total plasma IgE identified 171 allergic cases and 76 nonallergic controls, surpassing the minimum sample size requirement for statistical power. The majority of both cases and controls were pediatric, assigned female at birth, had pets at home, were nonsmokers, and were born via normal delivery. A small number of participants were older than 50 years, with the oldest case and control aged 63 and 56, respectively. Most participants fell into the 18 to 29 age range, and the age distribution skewed to the right (Table 1). Among the 20 smokers, 60% of allergic cases were active smokers, while 30% had stopped smoking; the remaining 10% were former smokers, including 1 allergic case and 1 nonallergic control. Among the 151 nonsmokers, 30% were exposed to secondhand smoke. Among allergic cases, 56% exhibited mixed allergy phenotypes (Fig. 1), with the rarest combination being a single female case with both AA and AD symptoms. In contrast, 42 individuals had AA+AR symptoms, and among cases with a single allergy phenotype (76 individuals), AR was the most common (43 cases), followed by AA (18 cases) and AD (15 cases).
Table 1.
Demographic profiles of allergic cases and nonallergic controls
| Demographic | Allergic cases (n = 171) |
Nonallergic controls (n = 76) |
|---|---|---|
| Age group* | ||
| Pediatric (n = 187) | 126 (73.68%) | 61 (80.26%) |
| Adult (n = 60) | 45 (26.32%) | 15 (19.74%) |
| Assigned sex at birth | ||
| Male (n = 38) | 31 (18.13%) | 7 (9.21%) |
| Female (n = 209) | 140 (81.87%) | 69 (90.79%) |
| Family history of allergies | ||
| With atopy (n = 69) | 54 (31.58%) | 15 (19.74%) |
| Without atopy (n = 92) | 56 (32.75%) | 36 (47.37%) |
| Unsure/unanswered (n = 86) | 61 (35.67%) | 25 (32.89%) |
| Pets at home | ||
| Yes (n = 206) | 141 (82.46%) | 65 (85.53%) |
| No (n = 41) | 30 (17.54%) | 11 (14.47%) |
| Smoker | ||
| Yes (n = 20) | 18† (10.53%) | 2† (2.63%) |
| No (n = 225) | 151 (88.30%) | 74 (97.37%) |
| Unsure/unanswered (n = 2) | 2 (1.17%) | 0 (0%) |
| Exposure to secondhand smoke | ||
| Yes (n = 81) | 57 (33.33%) | 24 (31.58%) |
| No (n = 161) | 110 (64.33%) | 51 (67.11%) |
| Unsure/unanswered (n = 5) | 4 (2.34%) | 1 (1.32%) |
| Type of birth | ||
| Normal delivery (n = 192) | 128 (74.85%) | 64 (84.21%) |
| Cesarean section (n = 38) | 30 (17.54%) | 8 (10.53%) |
| Unsure/unanswered (n = 17) | 13 (7.60%) | 4 (5.26%) |
Pediatric age: ≤21 y/o Adult age: >21 y/o.
12 cases and 1 control reported being active smokers, while 6 cases and 1 control reported to have quit.
Figure 1.
The distribution of allergic cases based on specific allergies: allergic asthma (n = 18), allergic rhinitis (n = 43), atopic dermatitis (n = 15), and multiple allergies (n = 95). Participants with uncertain or unanswered responses are excluded from this count.
3.2. 50% of allergic cases were sensitized to Dp allergens
Approximately half (50%) of the allergic cases (85 out of 171) exhibited sensitivity to Dp allergens, with significantly higher mean relative Dp allergen-IgE concentrations in their plasma (0.659 OD605) compared to nonallergic controls (0.360 OD605) (t = 16.206, P < 0.01). Additionally, their mean total IgE levels (188.31 IU/mL) were significantly elevated (t = 14.154, P < 0.01) compared to controls (38.85 IU/mL), with the highest recorded total IgE level among Dp-sensitized cases reaching 503.96 IU/mL (Fig. 2). Interestingly, there were no statistically significant differences in total IgE levels (H = 1.228, P = 0.541) among Dp-sensitized allergic cases with different single allergy phenotypes (AA, AR, and AD), and no significant variation (H = 2.706, P = 0.258) was observed in the relative levels of Dp-specific IgE among Dp-sensitized cases with these allergy phenotypes.
Figure 2.
Comparison of the relative Dp-specific IgE levels between 171 allergic cases (squares) and 76 nonallergic controls (triangle). The straight lines represent the sample means, while the broken line indicates the mean +1 SD of Dp-specific IgE levels in controls, used as the cutoff for Dp allergen sensitization. P value was using a 1-tailed Welch’s 2-sample t -test for means of 2 independent non-normal data samples.
3.3. 69% of Dp-positive allergic cases produce elevated levels of rDer p 2-specific IgE
Out of the 85 Dp-sensitized allergic individuals, 31 (69%) tested positive for sensitization to rDer p 2, with positive sensitization defined as having a relative rDer p 2-specific IgE concentration higher than the mean + 1 SD of the rDer p 2-specific IgE levels in selected nonallergic controls (Fig. 3). The mean relative IgE against rDer p 2 in rDer p 2-sensitized allergic cases (2.718 OD605) was significantly higher than in nonallergic controls (1.484 OD605). Additionally, the mean total plasma IgE level in rDer p 2-sensitized allergic cases (202.19 IU/mL) was significantly higher (t = 8.005, P < 0.01) than in nonallergic controls (50.68 IU/mL). The highest recorded plasma IgE concentration among rDer p 2-sensitized allergic cases was 480.21 IU/mL, and 8 of these cases (26%) manifested the AR-only phenotype.
Figure 3.
Comparison of relative rDerp2 allergen-specific IgE levels between 45 allergic cases (squares) and 45 nonallergic controls (triangles) at 605 nanometers (OD605) revealed significantly higher levels in allergic cases, with the mean exceeding the mean + 1 SD of nonallergic controls, indicating rDerp2 sensitization. The P value was computed using a 1-tailed Welch’s 2-sample t test for means of 2 independent normal distributions.
3.4. Up to 60% of IgE binding to Dp allergens was inhibited by rDer p 2
Plasma of Dp-sensitized cases preabsorbed with rDer p 2 significantly inhibited IgE binding to a Dp extract. Using seven Dp- and Der p 2-positive blood plasma samples, the observed percentage inhibition ranged from 20% to 63%. The mean percent inhibition of rDer p 2 against Dp was 39%. Only 2 plasma exhibited a percent inhibition that exceeded 50% (Fig. 4). These results indicate that rDer p 2 is a major sensitizing allergen in the Dp allergen extract that triggers IgE production among exposed atopic individuals.
Figure 4.
Percentage of plasma IgE inhibited by rDerp2 allergen from binding to a Dermatophagoides pteronyssinus (Dp) allergen extract. Mean percent inhibition is represented by a broken line (n = 7).
3.5. Pediatric individuals were sensitized to Dp allergens more often than adult individuals
OR revealed that sensitization to Dp allergens favored the pediatric age group (OR = 0.343, P < 0.01) and the male population (OR = 0.406, P = 0.01). Therefore, elevated Dp-specific IgE levels may be influenced by an individual’s age and sex (Table 2). This implies that age and sex are significantly associated with lower odds of sensitization to Dp. Therefore, adult individuals and a particular sex, such as females, may have a higher risk of sensitization to Dp. In contrast, other demographic and environmental variables such as familial history of allergy, type of birth, smoking status, and pet ownership did not demonstrate statistically significant associations with Dp sensitization. These nonsignificant outcomes imply that while these factors may influence immune responses, their impact on Dp sensitization alone is limited or potentially masked by other confounding factors.
Table 2.
Odds ratios (OR) of Dp sensitization associated with participant demographics
| Sensitization to Dp | Reference group | Odds ratio | Confidence interval (95%) |
|---|---|---|---|
| Age (n = 247) |
Pediatric | 0.343** | 0.167–0.702 |
| Sex (n = 247) |
Female | 0.406* | 0.202–0.819 |
| Familial history of allergy (n = 161) |
With atopy | 1.329ns | 0.693–2.547 |
| Type of birth (n = 230) |
Cesarean section | 0.927ns | 0.446–1.928 |
| Smoking (n = 245) |
Smoker | 0.858ns | 0.336–2.190 |
| Ownership of pets (n = 247) |
Pet owner | 1.326ns | 0.639–2.755 |
Data were transformed into binary variables. Odds Ratios were interpreted as follows: OR = 1 indicates no association between exposure and outcome; OR > 1 indicates a positive association (exposure increases the odds of outcome); OR < 1 indicates a negative association (exposure decreases the odds of outcome) [14].
Age: pediatric = 1; adult = 0.
Sex: female = 1; male = 0.
Familial history of allergy: with atopy = 1; without atopy = 0.
Type of birth: cesarean section= 1; normal delivery = 0.
Smoking: yes = 1; no: 0.
Ownership of pets: yes = 1; no: 0.
Dp, dermatophagoides pteronyssinus allergen extract; ns, not significant.
Statistically significant at P < 0.05.
Statistically significant at P < 0.01.
3.6. Atopic individuals expressed rDer p 2-specific IgE more often than nonatopic individuals
Individuals with atopy were found to have significantly higher odds of producing rDer p 2-specific IgE compared to nonatopic individuals. Specifically, those with a familial history of allergy were over 4 times more likely to be sensitized to rDer p 2 (OR = 4.167, P = 0.014), emphasizing atopy as a strong and reliable predictor of sensitization to this specific recombinant allergen (Table 3). This suggests that inherited allergic tendencies play a critical role in rDer p 2-specific IgE responses.
Table 3.
Odds ratios of rDer p 2-sensitization associated with participant demographics
| Sensitization to rDer p 2 | Reference group | Odds ratio | Confidence interval (95%) |
|---|---|---|---|
| Age (n = 90) |
Pediatric | 0.683ns | 0.168–2.78 |
| Sex (n = 90) |
Female | 0.279ns | 0.062–1.255 |
| Familial history of allergy (n = 58) |
With Atopy | 4.167* | 1.334–13.013 |
| Type of birth (n = 85) |
Cesarean Section | 1.333ns | 0.345–5.160 |
| Smoking (n = 90) |
Smoker | 3.107ns | 0.593–16.277 |
| Ownership of pets (n = 90) |
Pet owner | 0.909ns | 0.244–3.380 |
Data were transformed into binary variables. Odds ratios (OR) were interpreted as follows: OR = 1 indicates no association between exposure and outcome; OR >1 indicates a positive association (exposure increases the odds of outcome); OR <1 indicates a negative association (exposure decreases the odds of outcome) [14].
Age: pediatric = 1; adult = 0.
Sex: female = 1; male = 0.
Familial history of allergy: with atopy = 1; without atopy = 0.
Type of birth: cesarean section= 1; normal delivery = 0.
Smoking: yes = 1; no: 0.
Ownership of pets: yes = 1; no: 0.
rDer p 2, recombinant Der p 2 allergen; ns, not significant.
Statistically significant at P < 0.05.
In contrast, other factors such as age, sex, type of birth, smoking, and pet ownership did not show statistically significant associations with rDer p 2 sensitizations. Although not significant, the elevated OR for smoking may indicate a potential link that could emerge more clearly with larger sample sizes. It is also worth noting that the rDer p 2 analysis had a smaller sample size compared to the Dp analysis, which may have reduced the ability to detect other meaningful associations. Despite this limitation, the strong association between familial allergy history and rDer p 2 sensitization reinforces the importance of genetic predisposition in allergic responses, particularly to specific molecular components. These findings contribute valuable knowledge to our understanding of the factors that drive allergen-specific IgE production and may help inform targeted approaches in allergy diagnostics and management.
4. Discussion
HDMs are widely recognized as significant sources of allergens, with a substantial impact on individuals suffering from allergies due to their close proximity to humans. Despite the considerable clinical and socioeconomic consequences associated with HDM allergies [15], our knowledge of their allergenic profiles, especially in local contexts, remains incomplete [4]. Therefore, this study, which investigates the IgE reactivity of Filipinos to Dp allergens, with a particular focus on the major allergen Der p 2, holds considerable relevance.
The study findings reveal that both total IgE levels and allergen-specific IgE levels are markedly elevated in individuals with allergies compared to their nonallergic counterparts. This observation aligns with the well-established role of IgE in allergic reactions [16]. When examining the clinical presentations of allergies among the participants, the study identifies the combination of AA and AR as the most prevalent phenotype, while the co-occurrence of AA and AD is the least common. Although these findings resemble those of a Swedish study [17], differences in sample size and incidence rates exist. Importantly, the study does not identify statistically significant variations in total IgE and allergen-specific IgE levels among AA, AR, and AD phenotypes. This suggests that the diversity of allergy phenotypes may not be solely dependent on serological IgE concentration or specific allergen reactivity. This observation is in line with existing literature emphasizing the multifactorial and complex nature of allergy manifestations, particularly when they involve various concurrent and heterogeneous conditions [18–20].
The hereditary component of allergic disease susceptibility, recognized as a heritable trait to some extent [21, 22] and a significant risk factor for clinical allergic manifestations [23], was investigated by examining familial histories of allergy in relation to sensitization to Dp and rDer p 2. The study reveals that individuals with immediate relatives who have allergies are more likely to be sensitized to rDer p 2. Therefore, atopy can serve as a predictive factor for sensitization to Der p 2. In contrast, sensitization to Dp appears to be strongly associated with male gender and pediatric age, consistent with findings in other Asian populations [24, 25]. However, it is worth noting that the higher sensitization rate observed in males may extend beyond Dp allergens to include various other allergenic substances. While heredity plays a role in allergy predisposition, it is important to recognize that the clinical phenotype of allergy is influenced not only by genetic factors [21] but also by nongenetic elements. Epidemiological research on allergies has highlighted the impact of environmental and lifestyle factors during infancy, adolescence, and even during pregnancy [10, 26–28]. These factors, which primarily affect the diversity and balance of microorganisms residing on the body’s barrier organs [29, 30], can lead to a compromised innate immune system response and, consequently, the development of hypersensitivity later in life [31].
Among these nongenetic factors, smoking, pet ownership, and cesarean delivery have been identified as contributors to atopy through various mechanisms. Cigarette smoke, while devoid of allergenic molecules itself, increases the risk of sensitization to indoor allergens by altering the airway epithelium, reducing its protective barrier function [32]. This alteration facilitates the recognition of allergens by the innate immune system, triggering an adaptive immune response. Pet ownership can also play a significant role in allergy development, as animal dander is a common allergenic source with sensitization potential [33]. Additionally, biological agents such as parasites and commensal organisms in the fur of domesticated pets can serve as allergen sources [34]. Finally, cesarean delivery deprives infants of exposure to maternal birth canal microflora, which typically provides immunomodulatory signals crucial for preventing immune-mediated chronic disorders [35]. However, no significant associations were found between sensitization to Dp or rDer p 2 and factors such as cesarean delivery, exposure to pets, or cigarette smoke among the participants, suggesting these factors may have a relatively indirect role in allergy pathophysiology.
Comparatively, the rate of sensitization to Dp allergens in this study (approximately 50% of allergic cases) was lower than reported IgE-binding frequencies exceeding 80% in other populations [6, 36]. Similarly, the proportion of individuals with IgE specific to rDer p 2 in this study (69% of Dp-sensitized cases) was relatively lower compared to other populations [37, 38]. This discrepancy may be attributed to epitope differences between the rDer p 2 used in this study and the native Der p 2 from the extract. Additionally, participants may have been sensitized to other Dp allergens, supported by limited inhibition against the Dp extract in rDer p 2-absorbed plasma samples. However, apart from these observations, this study still validates the importance of rDer p 2 as a major allergen in Dp. Although having a lower comparative rate of sensitization in previous literature, the study shows that the majority of Dp-positive cases were also sensitized to rDer p 2 along with its high reactivity with the allergen extract, we have established that rDer p 2 is one of the major allergens that sensitizes allergic individuals from Ilocos Norte.
5. Conclusion
The data presented in this study revealed that allergic patients from Ilocos Norte, Philippines, exhibited sensitization to allergens in a Dp extract and rDer p 2. This study identifies the male sex and pediatric age as potential predictors for sensitization to Dp allergens, while a family history of allergy may serve as a predictor for elevated Der p 2-specific IgE. Consequently, it is strongly recommended that Dp and rDer p 2 be included in the panel of reagents utilized in immunodiagnostic and immunotherapeutic strategies and interventions for the local Filipino population sensitized to house dust mites, providing valuable insights for clinical applications.
Acknowledgements
The authors would like to acknowledge the unmatched commitment, devotion, and guidance of Dr. John Donnie A. Ramos from the birth of this study up to its completion; especially in facilitating the experiment, providing the materials and reagents, and proofreading the manuscript. The authors would also like to acknowledge the significant contributions of Prof. Maureen B. Sabit and her group, especially in the recruitment of participants and the collection of blood samples from Northwestern University, Laoag City, Ilocos Norte, Philippines as well as the Philippine Council for Health Research and Development. The authors thank the Research Center for the Natural Sciences, University of Santo Tomas for housing the experiment, and the University of Santo Tomas Ethics Review Committee for approving the study design and protocol.
Conflicts of interest
The authors have no financial conflicts of interest.
Author contributions
Ramos conceptualized and supervised the study. Sabit coordinated the blood sample collection and co-supervised the study. Alberba, Solis, Base, Julia, and Villanueva carried out the experiments, data analysis, and initial manuscript drafting. Patanindagat revised the manuscript. All authors have read and agreed to the final version of the manuscript.
References
- 1.Baiardini I, Braido F, Brandi S, Canonica GW. Allergic diseases and their impact on quality of life. Ann Allergy Asthma Immunol. 2006;97:419-28. [DOI] [PubMed] [Google Scholar]
- 2.Ramos JDA, Concepcion ZS, Pineda BA, Romano EL, Saep JB, Tagura J. Acarofauna and allergenicity of house dust mites in houses of selected Filipino allergic patients in Metro Manila. Acta Manila Ser A. 2006;54:7-14. [Google Scholar]
- 3.Yuriev S, Rodinkova V, Mokin V, Varchuk I, Sharikadze O, Marushko Y, Halushko B, Kurchenko A. Molecular sensitization pattern to house dust mites is formed from the first years of life and includes group 1, 2, Der p 23, Der p 5, Der p 7 and Der p 21 allergens. Clin Mol Allergy. 2023;21:1. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 4.Rodinkova VV, Yuriev SD, Kryvopustova MV, Mokin VB, Kryzhanovskyi YM, Kurchenko AI. Molecular profile sensitization to house dust mites as an important aspect for predicting the efficiency of allergen immunotherapy. Front Immunol. 2022;13:848616. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5.Limão R, Spínola Santos A, Araújo L, Cosme J, Inácio F, Tomaz E, Ferrão A, Santos N, Sokolova A, Môrete A, Falcão H, Cunha L, Ferreira A, Bras A, Ribeiro F, Lozoya C, Leiria Pinto P, Prates S, Plácido J, Coimbra A, Taborda-Barata L, Pereira Santos MC, Pereira Barbosa M, Pineda F. Molecular profile of sensitization to dermatophagoides pteronyssinus dust mite in Portugal. J Investig Allergol Clin Immunol. 2022;32:33-9. [DOI] [PubMed] [Google Scholar]
- 6.Caraballo L, Valenta R, Puerta L, Pomés A, Zakzuk J, Fernandez-Caldas E, Acevedo N, Sanchez-Borges M, Ansotegui I, Zhang L, van Hage M, Abel-Fernández E, Karla Arruda L, Vrtala S, Curin M, Gronlund H, Karsonova A, Kilimajer J, Riabova K, Trifonova D, Karaulov A. The allergenic activity and clinical impact of individual IgE-antibody binding molecules from indoor allergen sources. World Allergy Organ J. 2020;13:100118. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 7.Douwes J, Eduard W, Thorne PS. Bioaerosols. Int Encyclopedia Pub Health. 2017; 210-18. [Google Scholar]
- 8.Yang Y, Zhu R, Huang N, Li W, Zhang W, Wang Y, Yang L. The dermatophagoides pteronyssinus molecular sensitization profile of allergic rhinitis patients in Central China. Am J Rhinol Allergy. 2018;32:397-403. [DOI] [PubMed] [Google Scholar]
- 9.Hong S-N, Won JY, Nam E-C, Kim TS, Ryu Y-J, Kwon J-W, Lee WH. Clinical manifestations of allergic rhinitis by age and gender: a 12-year single-center study. Ann Otol Rhinol Laryngol. 2020;129:910-17. [DOI] [PubMed] [Google Scholar]
- 10.Marfortt DA, Josviack D, Lozano A, Cuestas E, Agüero L, Castro-Rodriguez JA. Differences between preschoolers with asthma and allergies in urban and rural environments. J Asthma. 2017;55:470-76. [DOI] [PubMed] [Google Scholar]
- 11.Altrichter S, Fok JS, Jiao Q, Kolkhir P, Pyatilova P, Romero SM, Scheffel J, Siebenhaar F, Steinert C, Terhorst-Molawi D, Xiang YK, Church MK, Maurer M. Total IgE as a marker for chronic spontaneous urticaria. Allergy Asthma Immunol Res. 2021;13:206-18. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 12.Ramos JD, Teo AS, Ou KL, Tsai LC, Lee BW, Cheong N, Chua KY. Comparative allergenicity studies of native and recombinant Blomia tropicalis Paramyosin (Blo t 11). Allergy. 2003;58:412-19. [DOI] [PubMed] [Google Scholar]
- 13.Ramos JDA, Castillo MP, del Rosario M, Gapay MA, Go TP, Kamantigue EG. Allergenicity and cross-reactivity of 3 house dust mite species among Filipino allergic patients. Philipp J Sci. 2007;29:357-61. [Google Scholar]
- 14.Szumilas M. Explaining odds ratios [published correction appears in J Can Acad Child Adolesc Psychiatry 2015 Winter;24(1):58]. J Can Acad Child Adolesc Psychiatry. 2010;19:227-29. [PMC free article] [PubMed] [Google Scholar]
- 15.Čelakovská J, Čermákova E, Vaňková R, Boudkova P, Andrýs C, Krejsek J. Sensitisation to molecular components of mites in atopic dermatitis patients. Food Agric Immunol. 2022;33:588-603. [Google Scholar]
- 16.Karsonova A, Riabova K, Villazala‐Merino S, Campana R, Niederberger V, Eckl‐Dorna J, Fröschl R, Perkmann T, Zhernov YV, Elisyutina OG, Fedenko ES, Khaitov MR, Fomina D, Beltiukov E, van Hage M, Grönlund H, Valenta R, Karaulov A, Curin M. Highly sensitive ELISA‐based assay for quantification of allergen‐specific IgE antibody levels. Allergy. 2020;75:2668-670. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 17.Pullerits T, Rönmark EP, Ekerljung L, Palmqvist MA, Arvidsson M, Mincheva R, Backman H, Kankaanranta H, Ilmarinen P, Rådinger M, Lundbäck B, Nwaru BI. The triad of current asthma, rhinitis and eczema is uncommon among adults: Prevalence, sensitization profiles, and risk factors. Respir Med. 2021;176:106250. [DOI] [PubMed] [Google Scholar]
- 18.Custovic A, Custovic D, Kljaić Bukvić B, Fontanella S, Haider S. Atopic phenotypes and their implication in the atopic march. Expert Rev Clin Immunol. 2020;16:873-81. [DOI] [PubMed] [Google Scholar]
- 19.Lee E, Hong S-J. Phenotypes of allergic diseases in children and their application in clinical situations. Korean J Pediatr. 2019;62:325-33. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 20.Yap JMG, Ching MW, Cabanilla CQ, Santos KC, Ramos JDA. Multiple house dust mite allergen-sensitization profiles in children with allergic asthma. J Allergy Ther. 2014;5:179. [Google Scholar]
- 21.Gilles S, Akdis C, Lauener R, Schmid‐Grendelmeier P, Bieber T, Schäppi G, Traidl‐Hoffmann C. The role of environmental factors in allergy: a critical reappraisal. Exp Dermatol. 2018;27:1193-200. [DOI] [PubMed] [Google Scholar]
- 22.Bønnelykke K, Sparks R, Waage J, Milner JD. Genetics of allergy and allergic sensitization: common variants, rare mutations. Curr Opin Immunol. 2015;36:115-26. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 23.Mahrunnisa F, Sumadiono S, Mulatsih S. Correlation between allergy history in family and allergy manifestation in school age children. Avicenna. 2021;2:11-8. [Google Scholar]
- 24.Melén E, Bergström A, Kull I, Almqvist C, Andersson N, Asarnoj A, Borres MP, Georgellis A, Pershagen G, Westman M, van Hage M, Ballardini N. Male sex is strongly associated with IgE-sensitization to airborne but not food allergens: results up to age 24 years from the BAMSE birth cohort. Clin Transl Allergy. 2020;10:15. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 25.Lindberg R, Arroyave C. Levels of IgE in serum from normal children and allergic children as measured by an enzyme immunoassay. J Allergy Clin Immunol. 1986;78:614-18. [DOI] [PubMed] [Google Scholar]
- 26.Oland AA, Booster GD, Bender BG. Psychological and lifestyle risk factors for asthma exacerbations and morbidity in children. World Allergy Organ J. 2017;10:35. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 27.Bloomfield SF, Rook GA, Scott EA, Shanahan F, Stanwell-Smith R, Turner P. Time to abandon the hygiene hypothesis: new perspectives on allergic disease, the human microbiome, infectious disease prevention and the role of targeted hygiene. Perspect Public Health. 2016;136:213-24. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 28.Sbihi H, Boutin RCT, Cutler C, Suen M, Finlay BB, Turvey SE. Thinking bigger: How early‐life environmental exposures shape the gut microbiome and influence the development of asthma and allergic disease. Allergy. 2019;74:2103-115. [DOI] [PubMed] [Google Scholar]
- 29.Vangay P, Ward T, Gerber JS, Knights D. Antibiotics, pediatric dysbiosis, and disease. Cell Host Microbe. 2015;17:553-64. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 30.Hyun D-W, Min HJ, Kim M-S, Whon TW, Shin N-R, Kim PS, Kim HS, Lee JY, Kang W, Choi AMK, Yoon J-H, Bae J-W. Dysbiosis of inferior turbinate microbiota is associated with high total IgE levels in patients with allergic rhinitis. Infect Immun. 2018;86:e00934-e00917. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 31.Nash MJ, Frank DN, Friedman JE. Early microbes modify immune system development and metabolic homeostasis—the “Restaurant” hypothesis revisited. Front Endocrinol. 2017;8:349. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 32.Saulyte J, Regueira C, Montes-Martínez A, Khudyakov P, Takkouche B. Active or passive exposure to tobacco smoking and allergic rhinitis, allergic dermatitis, and food allergy in adults and children: a systematic review and meta-analysis. PLoS Med. 2014;11:e1001611. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 33.Konradsen JR, Fujisawa T, van Hage M, Hedlin G, Hilger C, Kleine-Tebbe J, Matsui EC, Roberts G, Rönmark E, Platts-Mills TAE. Allergy to furry animals: new insights, diagnostic approaches, and challenges. J Allergy Clin Immunol. 2015;135:616-25. [DOI] [PubMed] [Google Scholar]
- 34.Zahradnik E, Raulf M. Animal allergens and their presence in the environment. Front Immunol. 2014;5:76. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 35.Boker F, Alzahrani A, Alsaeed A, Alzhrani M, Albar R. Cesarean section and development of childhood bronchial asthma: is there a risk? Open Access Maced J Med Sci. 2019;7:347-51. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 36.Sánchez-Borges M, Fernandez-Caldas E, Thomas WR, Chapman MD, Lee BW, Caraballo L, Acevedo N, Chew FT, Ansotegui IJ, Behrooz L, Phipatanakul W, Gerth van Wijk R, Pascal D, Rosario N, Ebisawa M, Geller M, Quirce S, Vrtala S, Valenta R, Ollert M, Canonica GW, Calderón MA, Barnes CS, Custovic A, Benjaponpitak S, Capriles-Hulett A. International consensus (ICON) on: clinical consequences of mite hypersensitivity, a global problem. World Allergy Organ J. 2017;10:14. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 37.Reginald K, Chew FT. Conformational IgE epitope mapping of Der p 2 and the evaluations of two candidate hypoallergens for immunotherapy. Sci Rep. 2018;8:3391. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 38.Wang HY, Gao ZS, Zhou X, Dai Y, Yao W, Zhang XF, Yang Z-W, Wu S-D, Yu C-H, Yang X-Y, van Ree R. Evaluation of the role of IgE responses to Der p 1 and Der p 2 in Chinese house dust mite-allergic patients. Int Arch Allergy Immunol. 2015;167:203-10. [DOI] [PubMed] [Google Scholar]