Host responses that correlate with respiratory droplet transmission of swine-origin influenza viruses in ferrets.. Mustela putorius furo

The determinants of influenza transmission remain poorly understood. Swine influenza viruses preferentially attach to receptors found in the upper airways; however, most swine influenza viruses fail to transmit efficiently from swine to humans, and from human-to-human. The pandemic 2009 H1N1 (H1N1pdm) virus was a rare exception of a swine virus that acquired efficient transmissibility from human-to-human, and is reflected in efficient respiratory droplet transmission in ferrets. We hypothesize that virus-induced host responses in the upper airways correlate with airborne transmission in ferrets. To address this question, we used the H1N1pdm virus and swine influenza A/swine/Hong Kong/201/2010 (HK201) virus that has comparable titre in the ferret nasopharynx, but it exhibits differential transmissibility in ferrets via respiratory droplet route. We performed a transcriptomic analysis of tissues from the upper and lower respiratory tract from ferrets infected with either H1N1pdm or HK201 viruses using ferret-specific Agilent oligonucleotide arrays. We found differences in the kinetics of the innate immune response elicited by these two viruses that varied across tissues. Overall design: Ferrets were mock inoculated with 0.5mL media or inoculated with 105 TCID50 of the A/CA/04/09 (H1N1) or A/Sw/HK/ 210/10 (H1N1) influenza viruses intra-nasally. There are a total of 9 ferrets per virus group and six ferrets for the mock group. Ferrets were euthanized at day 1 (n = 4 per virus group) and day 2 (n = 5 per virus group) post-inoculation (p.i.). Three mock inoculated ferrets were euthanized at days 1 and 2 p.i. Tissues from nasal turbinate, soft palate, pharynx, trachea, bronchus, and lungs were collected at necropsy, placed in RNAlater overnight at 4°C and conserved at -80°C. RNA was extracted and gene expression was analyzed by custom 4x180K ferret-specific oligonucleotide arrays (Agilent Cat# G4862A, design ID 48472)