Respiratory syncytial virus RSV an environmental factor in

Respiratory syncytial virus (RSV): an environmental factor in the pathogenesis of asthma and allergy Ronald L. Rabin, M. D. CBER/FDA Office of Vaccine Research and Review Laboratory of Immunobiochemistry 1

Asthma: a classic example of interaction between genetics and environment • Many genes linked to asthma and/or atopy are integral to innate or adaptive immunity. Innate: CD 14, TNF, TLR 4, C 5 Adaptive: IL 4, IL 13 • Childhood exposure to house dust endotoxin (HDE) inversely correlates with asthma prevalence. • CD 14 -260 C/T SNP and risk for atopy: Low HDE: decreased risk High HDE: increased risk 2

RSV: a viral “environmental factor? ” • RSV is frequently the first pathogen infants encounter. • T cells in infants are biased towards type 2 (Th 2) responses. • Type 2 T cell responses are necessary for asthma. • While we tend to focus on wheezing, asthmatics always (and sometimes only) cough. • Cough likely enhances spread of a respiratory pathogen compared to the symptoms of an uncomplicated upper respiratory infection (URI). • RSV URIs trigger bronchospasm with cough and wheezing in asthmatic children. • Asthma enhances RSV spread and survival. 3

Epidemiologic studies correlating RSV infection with asthma--TCRS Tuscon Children’s Respiratory Study (TCRS) • Prospective longitudinal study of 1246 infants. • Differences in airway structure and multiple genetic factors may determine the development of asthma and allergy later in life (Martinez et al, N Engl J Med, 1995). • RSV lower respiratory infection (LRI) increases risk for episodic wheezing associated with viral URI, but not with “true” asthma or atopy (Stein et al. Lancet, 1999). Boras, Sweden • 47 Swedish infants (30 -307 days) hospitalized with RSV bronchiolitis compared with age and sex matched controls • Children evaluated for asthma and atopy at about 1 and 3 years of age. • Higher incidence of asthma in RSV group that were also skin prick test positive (SPT+) 4

Genetic links common to asthma and severe RSV LRI 5

Goals of project • Define the mechanisms by which RSV manipulates innate and adaptive immune responses—ultimately in the context of genotype. • Define responses to live RSV by human T cells in vitro; must determine the cause of the T cell suppression that RSV is known to induce. • Develop a simple and reproducible experimental model, limited to monocyte-derived dendritic cells (MDDC) and CD 4 T cells. 6

Live RSV is necessary for immunosuppression 15 donors Chi et al. J Virol 80: 5032; 2006 7

Suppression transfers with MDDC supernatant P < 0. 01 P = 0. 05 120 cpm (x 103) 100 80 60 40 20 15 donors RSV UV RSV Mock Chi et al. J Virol 80: 5032; 2006 8

Live RSV stimulates MDDC to secrete IFN- P<0. 0001 450 400 350 IFN- (pg/ml) 200 150 50 40 30 20 10 0 15 donors RSV UVRSV Mock Chi et al. J Virol 80: 5032; 2006 9

RSV infection induces IFN- 1 gene expression by MDDC (q. RT-PCR) IFN- m. RNA (Ratio to -actin) 24 P P < 0. 0001. 0 0 0 ｲ P <00. 0001 1 16 4 3 2 1 0 16 donors RSV UVRSV Mock Chi et al. J Virol 80: 5032; 2006 10

IFN- and IFN- receptor blockade reverses RSV-induced suppression Inhibition of CD 4 T cell Proliferation (%) MDDC supernatants 40 30 20 10 0 anti-IFNAR 2 anti-IL 10 R 2 anti-IL 28 R - + - + + Chi et al. J Virol 80: 5032; 200611

Summary/Future directions Summary: • CD 4+ T cells, DC, and live RSV are sufficient to demonstrate RSVinduced immunosuppression. • Inhibition transfers with supernatant from RSV-infected DC. • IFN- and IFN- are expressed by MDDC in response to live RSV, and neutralizing their receptors substantially reverses RSVinduced suppression of T cells. Future directions: • Determine patterns of cytokine expression in response to RSV that are revealed by neutralizing the IFN- and IFN- receptors. • Compare the MDDC-mediated responses to primary myeloid and plasmacytoid DC from blood and tissue (tonsils). • Compare responses to RSV with those to other respiratory viruses (flu, RV, PIV 3). 12