Volume 29, Number 9—September 2023
Research
Interspecies Transmission of Swine Influenza A Viruses and Human Seasonal Vaccine-Mediated Protection Investigated in Ferret Model
Figure 2

Figure 2. Longitudinal monitoring of A/Pavia/65/2016 influenza A virus infection and transmission in ferrets. In 2 replicates, ferrets (n = 2) were intranasally inoculated with the A/Pavia/65/2016 strain and cohoused with ferrets in direct contact (n = 2) or in the same airspace (n = 2) enabling airborne exposure to respiratory droplets. Infection was evaluated by (A) monitoring daily nasal shedding of viral RNA between 0–14 dpi expressed as REUs. The specific humoral immune response was evaluated at 0 and 14 dpi using (B) a competitive ELISA to determine nucleoprotein-specific antibody titer, expressed as the inverse of the competition percentage (%) or (C) HI titer with the homologous virus. Competition percentage was calculated as (1 – sample/negative) ´ 100. Nucleoprotein competition percentage <50% or HI titer of <20 are considered negative (gray shaded areas). Outlier results for a single ferret in the intranasally inoculated group (IN-outlier) were excluded from the analysis and are shown by hollow black symbols. DC, direct contact; dpc, days postcontact; dpi, days postinoculation; HI, hemagglutination inhibition; IN, intranasally inoculated; Neg, negative; Pos, positive; RD, respiratory droplet; REU, relative equivalent unit; TCID50, 50% tissue culture infectious dose.