The diagnosis of Brazil nut allergy using history, skin prick tests, serum-specific immunoglobulin E and food challenges

BACKGROUND

Allergy to Brazil nut is a relatively common nut allergy and can be fatal. However, the evidence is lacking regarding the best approach to its diagnosis.

OBJECTIVE

We sought to determine the relative merits of history, skin prick testing, measurement of serum-specific IgE and challenge in the diagnosis of Brazil nut allergy.

METHODS

Fifty-six children and adults with a history of an allergic reaction to Brazil nut or evidence of sensitization were investigated by questionnaire (n=56), skin prick tests (SPTs) (n=53), measurement of serum-specific IgE to Brazil nut (n=54) and double-blind, placebo-controlled labial, and if necessary oral, challenges (n=19).

RESULTS

Brazil nut allergy occurred in highly atopic individuals of any age with a strong family history of atopy. In 24 of 56 (43%), the history of an immediate reaction was sufficient to make a diagnosis with confidence and an oral challenge was considered unsafe. Of the 19 subjects undertaking the 'gold standard' test of a double-blind, placebo-controlled, food challenge, all six subjects with a SPT of at least 6 mm had a positive challenge and all three subjects with a SPT of 0 mm had a negative challenge. In the remaining 10 (53%) subjects, where SPT was between 1 and 5 mm and serum-specific IgE was less than 3.5 kU/L, an oral challenge was performed resulting in three positive and seven negative challenges.

CONCLUSION

A combination of history, SPT and serum-specific IgE was adequate in achieving a diagnosis in the majority (77%) patients with suspected Brazil nut allergy. However, a doubtful history with SPT between 1 and 5 mm, or a serum-specific IgE less than 3.5 kU/L may require an oral challenge to help determine the risk of a Brazil nut allergic reaction.

In vitro stability and immunoreactivity of the native and recombinant plant food 2S albumins Ber e 1 and SFA-8

BACKGROUND

The ability of an intact protein to reach the circulatory system may be a prerequisite to allergenicity and many allergens, particularly those from plant foods, have been found to be consistently more resistant to digestion by pepsin than other proteins.

OBJECTIVE

This study assessed the pepsinolytic stability of native 2S albumins from Brazil nut and sunflower seed and their recombinant versions produced in Pichia pastoris. The physicochemical stability of native and recombinant Brazil nut 2S albumins and recombinant sunflower seed 2S albumin was also assessed. The immunoreactivity of native Brazil nut 2S albumin and recombinant 2S albumins was compared using serum from patients allergic to Brazil nuts and animals immunized with native 2S albumins.

METHODS

Digestibility was measured in simulated gastric fluid followed by SDS-PAGE. Circular dichroism spectra were used to analyse unfolding, as proteins were denatured by temperature, pH and guanidinium chloride. Immunoreactivity was assessed by immunoblot, RAST and ELISA.

RESULTS

Brazil nut 2S albumin was significantly more resistant to proteolytic digestion than other Brazil nut proteins. It was also resistant to thermally and chemically induced denaturation. Equally high resistance to proteolytic digestion was observed with sunflower seed 2S albumin. The recombinant albumins mirrored their native counterparts in stability and immunoreactivity.

CONCLUSION

The important food allergen Brazil nut 2S albumin is as stable to digestion as is sunflower seed 2S albumin, whose allergenicity has yet to be determined. The 2S albumins and their recombinant counterparts could not be easily denatured by physicochemical treatments. The results suggest that 2S albumin is the only Brazil nut protein to reach the gut immune system intact. The production of properly folded recombinant proteins will facilitate mechanistic studies as well as diagnostic testing and antigen-based therapies.

Cohort study of peanut and tree nut sensitisation by age of 4 years

OBJECTIVE

To determine the prevalence of sensitisation to peanuts and tree nuts in all children born during one year in one geographical area.

DESIGN

Birth cohort study with structured review at ages 1, 2, and 4 years.

SETTING

All children born on the Isle of Wight between January 1989 and February 1990.

SUBJECTS

Of 1456 children originally included, 1218 were reviewed at age 4 years. Of these, 1981 had skin prick tests.

MAIN OUTCOME MEASURES

Positive skin test results, clinical atopic disease, and risk factors for the development of atopy.

RESULTS

15 of 1218 (1.2%) children were sensitised to peanuts or tree nuts (13 to peanuts). Six had had allergic reactions to peanuts (0.5% of the population), one to hazelnuts, and one to cashew nuts; three had had anaphylactic reactions. Seven children had positive skin test results or detectable IgE to peanuts without clinical symptoms. Two children who reacted to peanut in infancy had lost their sensitivity by 4 years. Family history of atopy, allergy to egg (odds ratio 9.9, 95% confidence interval 2.1 to 47.9, and eczema (7.3, 2.1 to 26.1) were important predictors for peanut allergy.

CONCLUSIONS

IgE mediated allergy to peanuts is common in early childhood. In many the allergy persists but a minority may develop tolerance.

Effect of allergen avoidance in infancy on allergic manifestations at age two years

BACKGROUND

One hundred twenty children, identified before birth as being at high risk for atopy, were prenatally assigned to prophylactic or control groups.

METHODS

The infants in the prophylactic group either received breast milk from mothers on an exclusion diet or an extensively hydrolyzed formula. Their bedrooms and living rooms were treated repeatedly with an acaricide, and they used polyvinyl-covered mattresses with vented head areas. The infants in the control group were fed conventionally, and no environmental control was recommended.

RESULTS

A significant advantage, first demonstrated at 1 year of age, persists for children in the prophylactic group. They have less of any allergy or eczema, but the reduced prevalence of asthma is no longer significant. Only three children in the prophylactic group had positive skin prick test results compared with 16 in the control group, suggesting a significant reduction in sensitization.

CONCLUSION

A dual approach to allergen avoidance, focusing on foods and aeroallergens, appears to be beneficial in selected high-risk infants. Avoidance of potent allergens in early life increases the threshold for sensitization in these high-risk infants. Whether sensitization has been avoided or merely deferred has yet to be proved.

Acarosan and the Acarex test in the control of house dust mite allergens in the home

House dust mites are believed to be major triggers for allergic disease in atopic individuals. As part of a programme controlling dietary and aero-allergen exposure in high-risk infants, an acaricidal foam and powder (Acarosan) was applied to bedroom and main living room carpets, as well as upholstered furniture, on four occasions in the first year of life. Dust was assayed for mite antigen (Der p1) and these results compared with the semi-quantitative assay of guanine content (Acarex Test). After nine months mean Der p1 levels had decreased by 70% in the treatment group. Proportionally, the greatest fall occurred in those items that had the highest initial mite antigen content. The Acarex score does show a correlation with Der p1 levels, but cannot replace antigen assay when accurate data is required. A chemical acaricide may help reduce house dust mite antigen levels, but is not by itself sufficient to reduce levels below that considered critical for sensitisation.

Hypertensive care and the small practice

In an audit of a protocol for the follow-up of patients treated for hypertension, it was found that satisfactory compliance to standards was met for the majority. Satisfactory results are dependent on having one person responsible for follow-up and record systems.

Knowledge of and attitudes to medicines in the Southampton community

A 1 in 200 sample of the Southampton electorate was sent a postal questionnaire in January, 1984. Of the 740 adults surveyed, 443 (59.9%) returned completed questionnaires. One hundred and eighty-eight (42.4%) of those replying had been prescribed a medicine within the previous month. Two hundred and seventy-five respondents (62%) felt that not enough was explained about medicines by doctors or pharmacists. Consistent with this, was the fact that 37% were unaware of safe methods of disposal of leftover medicines. In addition, 112 of 154 (72.7%) people currently taking a prescribed medicine knew of no side-effects which could result from this. Eighty-three per cent of respondents thought an information leaflet would be helpful. Of nine items which previous authors had suggested should be included, seven were thought to be important by more than 75% of those replying. Although 54% of people wanted detailed information, 43% stated a preference for short, summarized points. We conclude that most patients need to have more information about prescribed medicines and they would welcome written leaflets. However, further work is necessary to determine the best format for such leaflets.

Evolution of obesity in young people in Busselton, Western Australia

The height and weight measurement of 928 young people of Busselton were collected over a period of up to 11 years. The prevalence of obesity was low in early childhood and increased progressively through adolescence and adulthood, so that 9% of male subjects and 16% of female subjects aged 21 years or over, were obese. The prevalence and degree of obesity were both greater in female subjects than in male subjects. Although most obese young adults were not obese in childhood, 50% of those who were obese between the ages of 9 and 14 years were still obese when examined in young adult life, and were at greater risk of becoming obese adults than were their non-obese peers. Most subjects who subsequently became obese young adults were significantly heavier than their non-obese peers at all ages from the age of 6 years.