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250 Natural rubber latex skin test safety
Abstracts
.I ALLERGY CLIN IMMUNOL VOLUME 105, NUMBER 1, PART 2
249
The Absence of Hev b 5 in Capture Antigen May Cause Falsenegative Results in Serologic Assays for Latex-specific IgE Antibodies Z Chen*. HP Ribs*, JE Slarerf. EJ Pauporef. EM Schneider*. X Baur* *BGFA, Bochum, Germany tCBER/FDA. Bethesda, MD Recent studies indicated that the two major serologic assays (CAP System and AlaSTAT) used for natural rubber latex-specific IgE antibodies produced more than 20% false-negative results when compated with the skin tests (puncture or prick test). To investigate if the false-negative serologic results are due to the absence of some allergens among the capture antigen used in the assays, we produced three latex major allergens Hev b I (rubber elongation factor), Hev b 5 and Hev b 6.01 (prohevein) as fusion-proteins with the maltose-binding protein (MBP) by recombinant methods. The individual recombinant allergens were then used to examine the specific IgE antibodies in sera from the patients with controversy results. I6 subjects were involved in this study. All these I6 subjects had been examined to have a clear latex allergy history and showed immediate type reactions in the skin prick testing as well as in the challenge test. The effort to determine the latex-specific IgE antibodies in all subjects failed not only by the Pharmacia-Upjohn CAP system but also by the EAST and immunoblots using the latex extract from the same production batch as the SPT reagent. The levels of the total IgE antibodies and the specific IgG antibodies to latex were found to be normal in all I6 subjects (median: 31.6 and 6.41 kU/L, respectively), when compared to that from the control groups with positive IgE values to latex (median: 78.2 and 4.81 kU/I+ respectively). Therefore, the levels of total IgE or specific IgG antibodies seem not to be the reason for the negative IgE measurements. Eight of the 16 subjects were found to be atopic based on the positive SPT results to common environmental and indoor aeroallergens. Specific IgE antibodies to corresponding allergens could be detected by all but one of these 8 subjects, indicating the presence of measurable circulating IgE in blood. RAST results using the individual recombinant latex allergens revealed negative IgE binding to Hev b I and Hev b 6.01 in all subjects. But, 8 of the I6 subjects showed significantly elevated IgE levels to Hev b 5 (0.45 to 7.43 kU/L by the EAST and CAP, median: 5.67 kUiL). No IgE-binding reactivity to MBP alone was observed. Autoinhibition assays also confirmed the test specificity. These findings demonstrate that latex allergen Hev b 5 may play a special role in the diagnostic tests showing false-negative IgE results. Hev b 5 has been identified as a strong antigen in latex by recombinant methods. So far, there is no direct experimental data showing the presence of intact Hev b 5 molecule in natural rubber latex. Low abundance in the latex protein preparation and high instability of the natural Hev b 5 are thought to be the major reasons for all these experimental results. Our present findings suggest that the role of Hev b 5 in the development of latex allergy needs to be further investigated.
S83
250
Natural Rubber Latex Skin Test Safety ME Bubak, MA Valyasevi, RT Jones. JW Yunginger. E Frigas, LW Hunt Mayo Clinic, Rochester. MN Natural rubber latex allergy has now been recognized for two decades. The quest for a safe, accurate, and commercially available skin test reagent continues, with sensitivity and safety as the main concerns. This Is a report of our latex skin testing safety data. Mayo Allergy uses a glycerinated, whole glove extract prepared by the Mayo Allergy Research Laboratory with 3 mg/ml total protein. The extract is standardized by inhibition immunoassay against a latex reference preparation (E5) provided by the FDA Center for Biologics Evaluation and Research. Testing is performed via prick technique with I: IO and neat material. Positives are 3 mm or greater wheals with flare and appropriate controls. From January 1992 thru August 1999. 2,932 patients underwent latex skin testing. Two (2) developed systemic symptoms (0.07% or 0.7 per I.000 patients tested). One patient had positives to many other allergens as well. with her reaction as hives and itching. The other patient had cough, wheeze, and dyspnea. Both were quickly resolved with epinephrine, beta agonist or antihistamine. 248 patients were skin test positive (8.5%). Natural rubber latex allergy skin testing has been performed on a large number of allergic patients with a very low incidence of sideeffects. This allergen behaves much like any of the other potent allergens. A standardized, commercially available extract would greatly aid in the evaluation of the latex allergic patient.
251
Safety and Reproducibility of Repeated Latex Allergen Challenges Using the Hooded Exposure Chamber @#EC) Method KM Kurtz. RG Hamilton, JA Schaefer; NF Adkinson Jr Johns Hopkins University School of Medicine, Baltimore, MD Bronchial, nasal and conjunctival challenges are useful forclarifying discordant clinical history (Hx) and skin and/or serologic tests and in assessing the degree of allergic sensitivity if they are quantitative (or at least semi-quantitative) and reproducible for a given individual. The HEC system is comprised of a powdered air purifying respirator with a fitted face shield and hood and uses glove derived latex allergen associated cornstarch particles (LAC) to simultaneously expose the conjunctiva, nose and lungs. Serial control and incremental LAC challenges are conducted until an endpoint based on upper and/or lower respiratory tract symptoms and peak expiratory flow rates is reached. The aim of this study was to determine the safety and reproducibility of the endpoint LAC dose using the HEC method. Six latex allergic [Hx, radioallergosorbent test (RAST), and prick skin test (PST) positive] subjects were challenged on 3 separate occasions. Serial dilution latex PST and serum anti-latex IgE by RAST were monitored at each visit and at a fourth follow-up visit. All subjects responded to LAC but not to air or cornstarch that were administered as controls. All reactions were confined to mild symptoms of allergic rhinoconjunctivitis and/or asthma that either resolved spontaneously or were reversed with inhaled albuterol. No subject experienced a systemic or late phase reaction. There were no significant changes in the endpoint LAC doses among the three challenge visits (p 9.2). The serum latex specific IgE of the individual subjects was not significantly affected by the three challenges (p ti.2). ‘Ihe concentration of latex extract necessary to produce an 8 mm wheal by PST significantly increased during the study (p < 0.001) suggesting that the natural history of declining latex sensitivity in latex avoiders was not affected by the repeated LAC exposures. The results of this study indicate that repeated HEC latex allergen challenges are both reproducible and safe and do not increase latex sensitivity.
.I ALLERGY CLIN IMMUNOL VOLUME 105, NUMBER 1, PART 2
249
The Absence of Hev b 5 in Capture Antigen May Cause Falsenegative Results in Serologic Assays for Latex-specific IgE Antibodies Z Chen*. HP Ribs*, JE Slarerf. EJ Pauporef. EM Schneider*. X Baur* *BGFA, Bochum, Germany tCBER/FDA. Bethesda, MD Recent studies indicated that the two major serologic assays (CAP System and AlaSTAT) used for natural rubber latex-specific IgE antibodies produced more than 20% false-negative results when compated with the skin tests (puncture or prick test). To investigate if the false-negative serologic results are due to the absence of some allergens among the capture antigen used in the assays, we produced three latex major allergens Hev b I (rubber elongation factor), Hev b 5 and Hev b 6.01 (prohevein) as fusion-proteins with the maltose-binding protein (MBP) by recombinant methods. The individual recombinant allergens were then used to examine the specific IgE antibodies in sera from the patients with controversy results. I6 subjects were involved in this study. All these I6 subjects had been examined to have a clear latex allergy history and showed immediate type reactions in the skin prick testing as well as in the challenge test. The effort to determine the latex-specific IgE antibodies in all subjects failed not only by the Pharmacia-Upjohn CAP system but also by the EAST and immunoblots using the latex extract from the same production batch as the SPT reagent. The levels of the total IgE antibodies and the specific IgG antibodies to latex were found to be normal in all I6 subjects (median: 31.6 and 6.41 kU/L, respectively), when compared to that from the control groups with positive IgE values to latex (median: 78.2 and 4.81 kU/I+ respectively). Therefore, the levels of total IgE or specific IgG antibodies seem not to be the reason for the negative IgE measurements. Eight of the 16 subjects were found to be atopic based on the positive SPT results to common environmental and indoor aeroallergens. Specific IgE antibodies to corresponding allergens could be detected by all but one of these 8 subjects, indicating the presence of measurable circulating IgE in blood. RAST results using the individual recombinant latex allergens revealed negative IgE binding to Hev b I and Hev b 6.01 in all subjects. But, 8 of the I6 subjects showed significantly elevated IgE levels to Hev b 5 (0.45 to 7.43 kU/L by the EAST and CAP, median: 5.67 kUiL). No IgE-binding reactivity to MBP alone was observed. Autoinhibition assays also confirmed the test specificity. These findings demonstrate that latex allergen Hev b 5 may play a special role in the diagnostic tests showing false-negative IgE results. Hev b 5 has been identified as a strong antigen in latex by recombinant methods. So far, there is no direct experimental data showing the presence of intact Hev b 5 molecule in natural rubber latex. Low abundance in the latex protein preparation and high instability of the natural Hev b 5 are thought to be the major reasons for all these experimental results. Our present findings suggest that the role of Hev b 5 in the development of latex allergy needs to be further investigated.
S83
250
Natural Rubber Latex Skin Test Safety ME Bubak, MA Valyasevi, RT Jones. JW Yunginger. E Frigas, LW Hunt Mayo Clinic, Rochester. MN Natural rubber latex allergy has now been recognized for two decades. The quest for a safe, accurate, and commercially available skin test reagent continues, with sensitivity and safety as the main concerns. This Is a report of our latex skin testing safety data. Mayo Allergy uses a glycerinated, whole glove extract prepared by the Mayo Allergy Research Laboratory with 3 mg/ml total protein. The extract is standardized by inhibition immunoassay against a latex reference preparation (E5) provided by the FDA Center for Biologics Evaluation and Research. Testing is performed via prick technique with I: IO and neat material. Positives are 3 mm or greater wheals with flare and appropriate controls. From January 1992 thru August 1999. 2,932 patients underwent latex skin testing. Two (2) developed systemic symptoms (0.07% or 0.7 per I.000 patients tested). One patient had positives to many other allergens as well. with her reaction as hives and itching. The other patient had cough, wheeze, and dyspnea. Both were quickly resolved with epinephrine, beta agonist or antihistamine. 248 patients were skin test positive (8.5%). Natural rubber latex allergy skin testing has been performed on a large number of allergic patients with a very low incidence of sideeffects. This allergen behaves much like any of the other potent allergens. A standardized, commercially available extract would greatly aid in the evaluation of the latex allergic patient.
251
Safety and Reproducibility of Repeated Latex Allergen Challenges Using the Hooded Exposure Chamber @#EC) Method KM Kurtz. RG Hamilton, JA Schaefer; NF Adkinson Jr Johns Hopkins University School of Medicine, Baltimore, MD Bronchial, nasal and conjunctival challenges are useful forclarifying discordant clinical history (Hx) and skin and/or serologic tests and in assessing the degree of allergic sensitivity if they are quantitative (or at least semi-quantitative) and reproducible for a given individual. The HEC system is comprised of a powdered air purifying respirator with a fitted face shield and hood and uses glove derived latex allergen associated cornstarch particles (LAC) to simultaneously expose the conjunctiva, nose and lungs. Serial control and incremental LAC challenges are conducted until an endpoint based on upper and/or lower respiratory tract symptoms and peak expiratory flow rates is reached. The aim of this study was to determine the safety and reproducibility of the endpoint LAC dose using the HEC method. Six latex allergic [Hx, radioallergosorbent test (RAST), and prick skin test (PST) positive] subjects were challenged on 3 separate occasions. Serial dilution latex PST and serum anti-latex IgE by RAST were monitored at each visit and at a fourth follow-up visit. All subjects responded to LAC but not to air or cornstarch that were administered as controls. All reactions were confined to mild symptoms of allergic rhinoconjunctivitis and/or asthma that either resolved spontaneously or were reversed with inhaled albuterol. No subject experienced a systemic or late phase reaction. There were no significant changes in the endpoint LAC doses among the three challenge visits (p 9.2). The serum latex specific IgE of the individual subjects was not significantly affected by the three challenges (p ti.2). ‘Ihe concentration of latex extract necessary to produce an 8 mm wheal by PST significantly increased during the study (p < 0.001) suggesting that the natural history of declining latex sensitivity in latex avoiders was not affected by the repeated LAC exposures. The results of this study indicate that repeated HEC latex allergen challenges are both reproducible and safe and do not increase latex sensitivity.