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Biomedical subjects

P C Potter

Publications and source records attributed to P C Potter.

At least 19 recordsLinked to original sources
PubMed2006

Mycobacterium tuberculosis infection may protect against allergy in a tuberculosis endemic area.

BACKGROUND: Epidemiological studies have shown an inverse relation of mycobacterial infection and the frequency of allergic diseases and asthma. Recent evidence suggests that allergic inflammation may be inhibited in the presence of chronic and persistent infections, such as that by Mycobacterium tuberculosis (MTB). The relation of tuberculin skin test (TST) size, an accepted marker of MTB infection and the frequency of allergic disease symptoms has not been reported from an area where MTB infection is endemic. OBJECTIVE: To investigate the association of TST and allergic disease symptoms, in children living in a tuberculosis (TB) endemic area. METHODS: In this cross-sectional study, 841 children aged 6-14 years from randomly selected household addresses in two poor communities of Cape Town, South Africa, were investigated with TST and standardized International Study on Asthma and Allergies in Childhood-based questionnaire on allergic disease symptoms. RESULTS: Children with positive TST (> or =10 mm) were significantly less likely to have allergic disease symptoms, in particular allergic rhinitis (AR) (adjusted odds ratio 0.43; 95% confidence interval 0.24-0.79) than those with negative TST. This association remained significant after adjusting for possible confounders and correcting for the effect of clustering (>1 child per household address) in the sample. There was a significant inverse linear trend in the relation of TST size in millimetre and the frequency of allergic disease symptoms, in particular AR (P<0.001). CONCLUSIONS: These results of inverse association of strong TST reaction and allergic disease symptoms in children from a TB endemic area are in support of the hypotheses that allergic inflammation may be inhibited by chronic infections, such as MTB.

Adolescent↗
PubMed2005

Occupational allergy in laboratory workers caused by the African migratory grasshopper Locusta migratoria.

BACKGROUND: Recent reports of fatal asthma cases associated with swarms of locusts affecting African countries have highlighted the importance of this insect in causing asthma morbidity and mortality. However, only limited information is available about the allergic health outcomes such as asthma and its determinants in exposed individuals. In this study, workers exposed to the African migratory locust Locusta migratoria were evaluated for allergic health outcomes as well as the nature of the offending allergens. METHODS: Ten scientists and technicians exposed to locusts in a laboratory were investigated for locust-related allergy using questionnaires and immunological tests. The presence of allergy was determined by quantification of specific IgE and IgG to L. migratoria using the UniCAP system and via skin-prick testing (SPT). The allergens were characterized by Western blot and ImmunoCAP inhibition assays. RESULTS: Six of the 10 workers experienced symptoms ranging from urticaria and rhinoconjuctivitis to asthma. Seven individuals demonstrated sensitivity on SPT and five had specific IgE antibodies to L. migratoria. Significant cross-reactivity was demonstrated for allergens in the locust faeces, body and wings but not to cockroach allergens. Novel allergens with molecular weights of approximately 70 kDa were identified in locust wings, which are distinctly different from other known allergen sources from locusts. CONCLUSION: Exposure to L. migratoria allergens is a potential sensitizer in exposed individuals. Raised levels of locust-specific IgE can be readily quantified. The wings of this insect species have been identified as a novel allergen source.

Adult↗
PubMed2005

Inverse association between Mycobacterium tuberculosis infection and atopic rhinitis in children.

BACKGROUND: The association between Mycobacterium tuberculosis (MTB) infection and atopy remains controversial. AIM: To investigate the association between MTB infection and atopic rhinitis in children living in a high TB incidence area. METHODS: In this cross-sectional study 418 children aged 6-14 years from an established epidemiological research-site in a poor urban community were invited to participate. They were assessed for allergic rhinitis (ISAAC questionnaire) and skin responses to tuberculin and eight environmental allergens. The presence of a BCG scar was documented, intestinal parasites and total and Ascaris lumbricoides-specific IgE levels were measured. Atopic rhinitis was defined, using the new World Allergy Organization (WAO) definition, as reported allergic rhinitis and a positive skin prick test (SPT > or =3 mm) to any allergen. RESULTS: Among the 337 children enrolled 10.4% had allergic rhinitis, 17.5% a positive SPT and 53% a positive tuberculin skin test (TST > or =10 mm). Children with a positive TST were significantly less likely to have recent atopic rhinitis (OR(adjusted) 0.06; 95% CI 0.007-0.5) than those with a negative TST. SPTs were significantly more common in children with negative TST who had recent allergic rhinitis (OR(adj) 34.0; 95% CI 7.6-152.6), but not in children with positive TST and recent allergic rhinitis (OR(adj) 0.6; 95% CI 0.07-5.2). CONCLUSIONS: MTB infection seems to reduce the prevalence of atopic rhinitis, and influences SPT reactivity in children with allergic rhinitis from a high TB incidence area.

Adolescent↗
PubMed2003

Effects of triamcinolone on quality of life in patients with persistent allergic rhinitis.

OBJECTIVE: To study the effects of triamcinolone acetonide on health-related quality of life (HRQL) in adult patients with allergic rhinitis. METHODS: This study was conducted in South Africa as a placebo-controlled, multicenter, randomized, double-blind study. Following a 7-day baseline run-in, patients were treated for 28 days with either triamcinolone or placebo. Interviewer-assisted quality-of-life assessments were conducted using the Juniper Rhinoconjunctivitis Quality of Life Questionnaire (RQLQ). Total symptom scores, including nasal congestion, were measured using daily diary cards. RESULTS: A total of 337 patients were recruited and 253 patients completed the study per protocol, of which 55 had seasonal allergic rhinitis (SAR) and 198 had persistent allergic rhinitis (PAR). Improvements in the mean scores per area of the RQLQ were significantly better with triamcinolone compared with placebo for the entire study group for activities (P = .04 at visit 4) and sleep, nasal symptoms, emotional problems, and overall score (P = .002, P = .04, P = .03, and P = .04, respectively, at visit 3). When the patients with SAR were separated from the patients with PAR in the analysis, improvement with triamcinolone was better than placebo only in the PAR patients. The overall investigator and patient assessments of relief favored triamcinolone. CONCLUSIONS: Triamcinolone given for 4 weeks improves symptom scores and HRQL in patients with allergic rhinitis. The ability of triamcinolone to relieve nasal congestion symptoms in PAR patients was correlated with improvements in HRQL.

Adolescent↗
PubMed2003

Levocetirizine is effective for symptom relief including nasal congestion in adolescent and adult (PAR) sensitized to house dust mites.

BACKGROUND: Antihistamines are the most commonly prescribed class of medication for perennial allergic rhinitis (PAR). The primary objective of this study was to determine whether levocetirizine (Xyzal(R)), the active enantiomer of cetirizine, could achieve at least a 50% improvement in PAR symptoms compared to the placebo over the first week of treatment. METHODS: A total of 294 patients with PAR due to house dust mites were randomized in this 8-week double-blind, placebo-controlled, multicentre trial to receive either levocetirizine 5 mg/day or placebo. Mean Total Four-Symptom Scores (T4SS) (nasal pruritus, ocular pruritus, rhinorrhoea and sneezing) were compared between treatment groups over weeks 1, 4 and 6. All individual symptom scores, including nasal congestion, were also studied. RESULTS: Levocetirizine showed an 86% improvement in T4SS over the first week of treatment and a 47% improvement over the entire treatment period compared with placebo. Absolute changes from baseline were 3.64 and 2.47 for levocetirizine and placebo, respectively. Individual symptom scores showed statistically significant (P < or = 0.01) differences in favour of levocetirizine for all study time-points. Nasal congestion was unexpectedly significantly improved (P < 0.001). The incidence of reported adverse events was comparable between treatment and placebo group. CONCLUSIONS: Levocetirizine 5 mg/day is an effective and well-tolerated treatment of PAR. In addition, levocetirizine is effective for the relief of nasal congestion.

Adolescent↗
PubMed2001

Allergenicity and cross-reactivity of buffalo grass (Stenotaphrum secundatum).

BACKGROUND: In the subtropical climate of South Africa, grasses of the subfamily Panicoideae are predominant. Bermuda grass has previously been shown to be an important local allergen, and immunoglobulin E (IgE) epitopes of Bermuda grass extracts are known to be distinct from those of the Pooid pollen extracts. Following our demonstration of sensitivity in 43% of patients grass-allergic to the Panicoid, Kikuyu grass, we have studied the closely related buffalo grass, Stenotaphrum secundatum, indigenous to the Western Cape region, the east coast of Africa and the oceanic islands such as Mauritius; and Eragrostis, another common indigenous grass with a wide distribution. OBJECTIVE: To partially characterise the allergens of buffalo pollen, and examine its immunological relationships with local common grasses such as Eragrostis and Kikuyu. METHODS: Grass-allergic patients were evaluated clinically, and skin prick tests (SPTs) and radio-allergosorbent tests (RASTs) to Bermuda and grass mix were performed. Sera of timothy grass-sensitive patients from Belgium were also included in this study. Pollen extract from buffalo grass was characterised by specific IgE binding by means of immunoblotting and enzyme-linked immunosorbent assay (ELISA). Cross-reactivity between the grasses was studied by means of inhibition of IgE binding. RESULTS: More than 90% of grass-sensitive patients were found to have IgE antibodies to Buffalo and Eragrostis pollen. Inhibition of ELISA and immunoblots revealed that extracts of these grass pollens could significant inhibit IgE binding to the local grass pollens, Kikuyu, buffalo, Eragrostis and Bermuda on solid phase, but 100% inhibition was never achieved, indicating that cross-reactive but also unique epitopes are present. We also identified a subset of patients with negative RASTs to Bermuda, and minimal inhibition by Bermuda pollen extract. CONCLUSION: Buffalo and Eragrostis are important aeroallergens in the Cape, dispersed during the long dry, windy summer. Our data suggest that the local grasses are major sensitisers, and that South African diagnostic panels should include extracts of buffalo and Eragrostis grasses.

Cross Reactions↗
PubMed2001

Latex allergy at Groote Schuur Hospital--prevalence, clinical features and outcome.

BACKGROUND: The incidence of latex allergy is increasing worldwide but there is very little information available on the clinical outcome for affected individuals. OBJECTIVE: To determine the prevalence of latex allergy at Groote Schuur Hospital, a large teaching hospital in Cape Town, and to study the outcome for affected individuals. METHOD: Using a questionnaire, we screened 2,316 hospital workers for the presence of work-related symptoms. Workers who were symptomatic had Immunocap RAST (CAP RAST) or skin-prick tests to confirm latex sensitivity. Latex-avoidance measures were implemented in positive subjects. One hundred symptomatic, sensitised individuals were followed up 3 months after intervention to assess their clinical status. A further cohort of 25 individuals with ongoing nasal symptoms were studied in detail. RESULTS: Latex sensitisation was confirmed in 182 of 717 symptomatic workers (25.3%). Sensitised symptomatic workers were significantly more likely to have had a previous history of urticaria (P = < 0.001), oral allergy syndrome (P = < 0.001), or allergic conjunctivitis (P = 0.001), but not hay fever, perennial rhinitis, eczema or insect allergies. Latex sensitisation occurred among all classes of health care workers. Ocular and cutaneous symptoms were significantly associated with positive latex sensitisation (P = < 0.001). After latex intervention, ocular symptoms (P = < 0.001), skin rashes (P = < 0.001) and wheezing (P = 0.001) reduced significantly. Nasal symptoms did not improve. Undiagnosed and untreated underlying allergies to common aero-allergens were present in the majority of latex-sensitised patients with ongoing nasal symptomatology. CONCLUSION: The prevalence of symptomatic sensitisation to latex allergy at Groote Schuur Hospital is between 9.2 and 11.2%. Ocular and cutaneous symptoms are the most prevalent in sensitised workers, and unlike nasal symptoms are significantly reduced when latex-avoidance measures are introduced. Ongoing nasal symptoms after intervention is instituted are probably due to other allergic sensitivities in latex-sensitised health care workers.

Humans↗
PubMed2000

PBMCs from both atopic asthmatic and nonatopic children show a TH2 cytokine response to house dust mite allergen.

BACKGROUND: The hypothesis that in atopic diseases the T-helper response is skewed toward a T(H)2-type cytokine response was based on studies with mitogen stimulation, T-cell clones, or both. OBJECTIVE: Using primary cultures, we investigated (1) whether atopic asthmatic patients have a T(H)2 response and nonatopic subjects have a T(H)1 response to allergen and (2) whether atopic patients have a decreased ability to mount T(H)1 immune responses to mycobacterial antigens. METHODS: The responses of PBMCs to allergen (house dust mite [HDM]) or purified protein derivative of Mycobacterium tuberculosis (PPD) stimulation from 10 severely and 14 moderately asthmatic patients (all allergic to HDM) were compared with those of 17 nonatopic healthy black (Xhosa) children. RESULTS: HDM-stimulated proliferation, IL-5 release, and the IL-5/IFN-gamma ratio were significantly increased in subjects with atopic asthma, whereas IFN-gamma release was not significantly different. IL-4 levels were below the level of detection. PPD-stimulated proliferation, IL-5 release, IFN-gamma release, and the IL-5/IFN-gamma ratio were not significantly different among the groups. Each group had a significantly higher IL-5/IFN-gamma ratio in response to HDM than to PPD (a T(H)1 stimulus). CONCLUSION: Our study, which used primary cultures to investigate the hypothesis that nonatopic subjects have a T(H)1 response to allergens, indicates that HDM stimulates a T(H)2 cytokine response in both atopic and nonatopic subjects but that the response is enhanced in atopic patients. Our results with PPD suggest that normal and atopic asthmatic subjects can have a T(H)1 cytokine response to mycobacteria, but there is a subgroup of atopic subjects that have a T(H)2 response.

Allergens↗
PubMed2000

Guideline for the management of chronic asthma in children--2000 update. Allergy Society of South Africa Working Group.

OBJECTIVE: To increase awareness of asthma and diagnose asthma early in children. To make recommendations regarding management of chronic childhood asthma in a country with diverse cultural, socio-economic and educational characteristics. The guideline should be used by health professionals involved in the treatment of asthma at all levels of care. OPTIONS: Various management options were considered. Ideal treatment includes use of the new generation inhaled corticosteroids (fluticasone, budesonide), housedust mite intervention for asthma control using impermeable covers for pillows and mattresses, and if needed use of inhaled long-acting beta 2 agonists (LABAs) and leukotriene receptor antagonists (LRAs). Alternative therapeutic approaches for situations where resources are limited include simple housedust mite control measures (e.g. airing mattresses and bedding), avoidance of exposure to passive smoking, use of lower doses of beclomethasone than recommended by other guideline documents and/or sustained-release (SR) theophylline as preventer treatment and use of plastic bottles as cheap spacer devices. OUTCOMES: The main potential outcomes considered were: to reduce morbidity and mortality by correct diagnosis of asthma, to achieve the best quality of life for the child with asthma, to minimise side-effects from medication and to prevent development of permanently abnormal lung function. EVIDENCE: Current international guideline documents for diagnosis and management of childhood asthma were evaluated. Clinical studies before 1998 pertaining to the various aspects of management of childhood asthma were reviewed, including controlled studies on the use of inhaled corticosteroids in children with asthma, randomised controlled trials on the use of LRAs and two studies evaluating the efficacy of LABAs. Current data on the anti-inflammatory effects of SR theophylline were also reviewed as well as a randomised controlled trial on the benefits of SR theophylline as adjunct treatment in childhood asthma. The benefit of simple spacer devices, based on well-conducted local studies (published in an international peer-reviewed journal) was also considered. VALUES: The South African Childhood Asthma Working Group (SACAWG) committee members, appointed by the Allergy Society of South Africa (ALLSA), were selected to represent the interests of health professionals involved in the care of childhood asthma and to co-opt other colleagues with expertise relevant to the guideline. The committee was divided into six task groups headed by a chairperson--each task group had to review critically the previous SACAWG guideline (for deficiencies and obstacles to implementation), review current trends in asthma management (evidence-based where available) and submit proposals and recommendations to their respective chairperson. The chairperson then compiled a report for discussion by the SACAWG executive committee. The executive group convened a meeting to discuss the recommendations and obtain consensus. An editorial board was appointed to compile the final report. Cultural factors, patient preferences, cost, availability and education were considered important. BENEFITS, HARMS AND COSTS: Proper treatment should enable most children with asthma to lead normal or near-normal lives. The guideline could be implementable at all levels of care. The risk of systemic effects due to inhaled corticosteroids should be minimised in children with mild to moderate persistent asthma (risk of systemic effects is more likely at daily beclomethasone doses exceeding 400 micrograms or the equivalent dose of other inhaled corticosteroids). Promotion of simple environmental control measures and use of inhaled beclomethasone and/or SR theophylline should make treatment more widely available and more affordable and improve adherence to treatment. Alternative cheap plastic bottle spacer devices will increase availability and assist with overcoming the problem of incorrect inha

Adrenal Cortex Hormones↗
PubMed1999

Decline in total serum IgE after treatment for tuberculosis.

BACKGROUND: Infection with Mycobacterium tuberculosis induces a type-1 immune response, whereas intestinal parasites elicit a type-2 response. Given that type-1 and type-2 responses inhibit each other, we investigated if M tuberculosis downregulates serum IgE, a marker of a type-2 response. METHODS: A prospective study was done in the Western Cape Province of South Africa, where tuberculosis and intestinal-parasite infection are common. Total serum IgE was determined for 37 controls and for 33 adolescent patients at presentation with tuberculosis and after successful completion of treatment. IgE specific for ascaris and allergens were measured in a subset of these individuals. Mantoux skin tests were done on 35 controls and on 31 patients at diagnosis. FINDINGS: Total IgE concentrations were high in controls (mean 313 kU/L) and in patients before treatment (mean 457 kU/L, p=0.085) and declined in all patients following successful treatment (mean 175 kU/L, p<0.0001). Posttreatment IgE concentrations did not differ from concentrations in controls. Ascaris-specific IgE was lower in controls (mean 1.73 kU/L) than in patients before treatment (4.62 kU/L, p=0.023) and was 2.39 kU/L in patients after treatment (p=0.0625). Tuberculin induration correlated inversely with IgE in patients but not in controls. INTERPRETATION: Infection with M tuberculosis as such is not incompatible with a prominent IgE response. IgE concentrations decreased after successful treatment of tuberculosis, showing that IgE concentrations in human beings can be downregulated under these circumstances, presumably due to enhancement of a type-1 response.

Adolescent↗
PubMed1999

Exposure to peanuts in utero and in infancy and the development of sensitization to peanut allergens in young children.

This study attempted to determine the underlying factors that may influence the development of peanut sensitization in young children in South Africa. One of our objectives was to ascertain whether the consumption of peanuts or peanut-containing foods during pregnancy and lactation by mothers from atopic families impacted upon the development of an allergic response to peanuts in the child. Forty-three children between the ages of 0 and 3 yr participated in this study. There were 25 peanut-sensitized subjects and 18 control subjects (children sensitized to milk and/or egg, but not to peanuts). A significant association was found between peanut sensitization and sensitivity to soya (p=0.0002), wheat (p=0.03), and cod fish. We found that mothers who consumed peanuts more than once a week during pregnancy were more likely to have a peanut-allergic child than mothers who consumed peanuts less than once a week (odds ratio=3.97, 98% confidence interval 0.73-24). Peanuts or peanut butter was introduced into the child's diet from a significantly younger age in the peanut-allergic subjects (p<0.03). There was a positive correlation in the peanut-allergic subjects between age of introduction of peanuts and age at the onset of symptoms (r=0.63). Exclusive breast feeding did not protect against the development of peanut sensitization. Peanut allergy is associated with an increased risk of sensitization to other foods. It is more likely to occur if mothers eat peanuts more frequently during pregnancy and introduce it early to the infant's diet. These features highlight potentially avoidable factors that might prevent sensitization.

Animals↗