CpG-oligodeoxynucleotides inhibit RSV-enhanced allergic sensitisation in guinea pigs

Abstract

Experimental respiratory syncytial virus (RSV) infection of guinea pigs is associated with enhanced allergic sensitisation to inhaled ovalbumin (OA) and low-level viral persistence in the lungs. Based on the T-helper (Th)1/Th2 paradigm, in which a Th2 shift is characteristic of an allergic response and less effective anti-viral immunity, the effects of immunotherapy with synthetic cytosine phosphate-guanine-oligodeoxynucleotides (CpG-ODN), which are potent Th1 stimuli, on OA sensitisation with and without RSV infection were evaluated.Measurements included quantitative histology for airway inflammation by T-cells and eosinophils, semiquantitative RT-PCR for lung Th1/Th2 balance (interferon (IFN)-c/interleukin (IL)-5 mRNA ratios), and serology for circulating titres of OA-specific immunoglobulin (Ig)G 1 antibodies. RSV antigens were identified in lung tissue sections by immunohistochemistry.CpG-ODN immunotherapy did not prevent OA sensitisation of guinea pigs; however, in RSVinfected, OA-sensitised animals, CpG-ODN administration was associated with significant reductions of airway T-cells and eosinophils, increased lung IFN-c/IL-5 ratios, and decreased OA-specific IgG 1 antibody titres to levels observed in uninfected, OA-sensitised animals. Viral antigens were identified in a similar proportion of the lungs of RSV-infected animals, irrespective of CpG-ODN immunisation status.In conclusion, cytosine phosphate-guanine-oligodeoxynucleotides immunotherapy protects guinea pigs against respiratory syncytial virus-enhanced ovalbumin sensitisation and might be a relevant intervention in the context of post-bronchiolitis allergic sensitisation in children.

T Helper 1 Background Protects Against Airway Hyperresponsiveness and Inflammation in Guinea Pigs With Persistent Respiratory Syncytial Virus Infection

“…CPG-ODN, Type B (single-stranded, code 2007, sequence 5=-TCGTCGTTGTCGTTTTGTCGTT-3=) was purchased from Coley Pharmaceuticals, Inc. (Wellesley, MA). Based on our previous work with CpG-ODN administration to guinea pigs (21), animals underwent anesthesia with 3%-5% inhalational halothane and were intranasally inoculated with 100 g of CpG-ODN dissolved in 300 L of sterile saline, given biweekly over 4 wk, for a total of three doses. CpG-ODN-treated animals were inoculated with RSV 7 d after receiving the final dose of CpG-ODN (21).…”

“…RT was performed on 1.0 g aliquots of total RNA using random primers (Invitrogen Canada, Inc., Burlington, Ontario, Canada) according to the manufacturer's instructions with Superscript II (Invitrogen). PCR for guinea pig-specific IFN-␥, IL-5, and ␤-actin (constitutively expressed housekeeping gene) was performed in duplicate for each animal using cycling conditions published elsewhere (21). PCR products underwent electrophoresis on 2% agarose gels stained with ethidium bromide.…”

“…Slides were coded to mitigate against observer bias. Digital images of five to 10 membranous bronchioles per animal were captured using a digital camera mounted on a light microscope (Nikon Corporation, Kanagawa, Japan) (21). Image Pro PLUS image analysis software (Media Cybernetics, Inc., Silver Spring, MD) was used to place a grid (60 ϫ 60 pixels) over each image.…”

“…In naïve CH, intranasal administration of CpG-ODN is well tolerated and produces a Th1 shift in the lung IFN-␥/ IL-5 gene expression ratio (21). We have recently shown that CpG-ODN immunoprophylaxis of CH inhibits the viral component of RSV-enhanced allergic sensitization to aerosolized OA (21), suggesting that CpG-ODN could potentially be useful for limiting the extent of RSV infection in these animals.…”

“…STR2 are comparatively allergy resistant, as these animals do not readily sensitize to foreign antigens (19) and release less histamine in response to ovalbumin (OA) challenge when passively sensitized with anti-OA IgG antibody (20). We have previously reported that RSV-inoculated STR2 develop an acute lung infection characterized by AHR, airway inflammation by T cells and eosinophils, and a Th2 shift in the lung gene expression ratios of IFN-␥ (Th1 cytokine) to IL-5 (Th2 cytokine), but with lower titers of intrapulmonary replicating virus than observed in more allergysusceptible animals (16,21). Long-term outcomes of RSV infection regarding the possibility of viral persistence, AHR, and airway inflammation in STR2 have not yet been reported.…”