Chronic virus infections supress atopy but not asthma in a set of children from a large latin american city: a cross-section study
1 SCAALA (Social Change, Asthma and Allergy in Latin America) Research Program
2 Departamento de Ciências da Biointeração, Instituto de Ciências da Saúde, Universidade Federal da Bahia, Av. Reitor Miguel Calmon, Canela, Salvador, CEP 40110100, Brazil
3 Departamento de Medicina Social, Centro de Ciências da Saúde, Universidade Federal de Pernambuco, Av. Prof. Moraes Rêgo, 1235, Cidade Universitária, Recife, CEP 50670-901, Brazil
4 ProAR, Departamento de Clínica Médica, Faculdade de Medicina da Bahia, Universidade Federal da Bahia, Av. Reitor Miguel Calmon, Canela, Salvador, CEP 40110100, Brazil
5 Colegio de Ciencias de la Salud, Universidad San Franscisco de Quito, Hospital de Los Valles, Via Interoceanica Km 12.5, Quito, Ecuador
6 Molecular and Biochemical Parasitology, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
7 London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
8 Instituto de Saúde Coletiva, Universidade Federal da Bahia, Rua Basílio da Gama S/N Canela, Salvador, CEP 40.110-040, Brazil
BMC Pulmonary Medicine 2011, 11:24 doi:10.1186/1471-2466-11-24Published: 14 May 2011
The prevalence of allergic diseases has increased over recent decades in affluent countries, but remains low in rural populations and some non-affluent countries. An explanation for these trends is that increased exposure to infections may provide protection against the development of allergy. In this work we investigated the association between exposure to viral infections in children living in urban Brazil and the prevalence of atopy and asthma.
School age children living in poor neighborhoods in the city of Salvador were studied. Data on asthma symptoms and relevant risk factors were obtained by questionnaire. Skin prick tests (SPTs) were performed to seven aeroallergens, and specific IgE was measured to four of these. Viral infections were determined by the presence of specific IgG in serum to Herpes simplex (HSV), Herpes zoster (HZV), Epstein-Barr (EBV), and Hepatitis A (HAV) viruses.
A total of 644 (49.7%) children had at least one allergen-specific IgE> 0.35 kU/L and 489 (37.7%) had specific IgE> 0.70 kU/L. A total of 391 (30.2%) children were skin test positive (SPT+), and 295 (22.8%) children were asthmatic. The seroprevalence of viral infections was 88.9% for EBV, 55.4% for HSV, 45.5% for VZV and 17.5% for HAV. Negative associations were observed between SPT+ and HSV (OR = 0.64, CI = 0.51, 0.82) and EBV (OR = 0.63, CI = 0.44, 0.89) infections, but no associations were seen between viral infections and the presence of allergen-specific IgE or asthma.
These data do not support previous data showing a protective effect of HAV against atopy, but did show inverse associations between SPT+ (but not specific IgE+) and infections with HSV and EBV. These findings suggest that different viral infections may protect against SPT+ in different settings and may indicate an immunoregulatory role of such infections on immediate hypersensitivity responses. The data provide no support for a protective effect of viral infections against asthma in this population.