study of T-helper 2 / T-Helper 1 imbalance in respiratory syncytial virus bronchiolitis in relation to severity and outcome

ABSTRACT

The present study was carried out on 80 infants with acute bronchiolitis. Their ages ranged from 2-22 mo. They were 60 males and 20 females. 30 apparently healthy infants of matchable age and sex were enrolled in the study as controls. Besides taking history, thorough clinical examination and routine laboratorial investigations, arterial oxygen saturation, RSV tissue culture of nasopharyngecil lavage, direct immunoflourescence for serum RSV Ig-M, serum IL-4 and INF-gamma were done. Results showed that viral bronchiolitis is predominant in males around 6 mo of age and in winter months. RSV infection was found, in 72.5% of cases. Serum IL-4 was not different between RSV negative patients and controls but it was significantly higher in RSV positive patients than either RSV-ve cases or controls [P< 0.001 for each]. Furthermore in RSV + ve patients it was significantly higher in severe and fatal cases than in milder and surviving ones [P<0.001 for each]. Serum INF-gamma showed no significant difference between RSV + ve and RSV -ve patients hut it was significantly higher in both groups than controls [P< 0.001 for each]. In RSV+ve cases it was significantly lower in more severe and fatal cases than milder and living ones [P<0.05 respect]. The ratio I-L-4/ INF-gamma was significantly higher in RSV + ve group than RSV-ve and than controls [P<0.001 and P< 0. 05 respectively]. ARC and SaO[2]% showed significantly lower values in RSV + ve patients than RSV-ve ones [P<0.001], but the latter showed significantly higher AEC than controls [P < 0.05]. In RSV + ve group, both parameters were significantly lower in severer and fatal cases than milder and living ones [P < 0.001 for each]. In RSV positive group, significant positive correlations were found between disease severity and either serum IL-4 or IL-4 /INF-gamma ratio [r=0.789 and r=0.823, P < 0.001 respectively] but disease severity was inversely correlated with either AEC or SaO2% [r = - 0.962 and r = - 0.828, P < 0.001 respectively]. RSV is the major etiologic virus of bronchiolitis in young infants. Viral tissue cultures and direct immunoflourescene are of equally diagnostic value but both may be needed. Most of the severe and fatal cases are in RSV + ve group. Th2 / Th-l imbalance reflected on IL-4 /INF gamma ratio is more deranged in RSV bronchiolitis with Th-2 predominance especially in more severe and fatal cases. These conclusions may be a rationale for addition of antiviral in severe cases of bronchiolitis but further studies of antiviral drugs and their effect on cytokines may be needed to address this recommendation