Fig 2. Changes in FHA expression in B. pertussis after passage through nose and lungs of naive and vaccinated mice.

(a) DNA sequence of the three homopolymeric fhaB-G tract variants observed in B. pertussis. The wild type fhaB gene is 10,773 nucleotides (nt) long, with a homopolymeric tract of 10 Gs at nucleotide position 1,078–1,088. Frameshift mutations in this G-tract result in the introduction of stop codons at nucleotides 1,541 and 1,090 for fhaB-G₁₁ and fhaB-G₉, respectively. (b-c) Bacteria from the nose (b) or lungs (c) were pooled per mouse. Each symbol represents the log-transformed fhaB-G₁₀ percentage of the recovered bacteria normalized to the fhaB-G₁₀ percentage of its respective inoculum. Data is shown for all time points combined. Horizontal lines represent median ± interquartile range. Dashed line indicates no change in fhaB-G₁₀ percentage of the recovered bacteria compared to its inoculum. (d) Expression of FHA in inoculum batches and in post-challenge bacterial samples was determined by western blot. Polyclonal antibodies to FHA were used; purified FHA and a fhaB knockout strain (ΔfhaB) were included as a positive and negative control, respectively. B3629-m089, B3629-m086 and B3629-m093 contain predominantly wild type, mutant, and mutant fhaB alleles, respectively. The position of molecular weight marker (in kDa) is shown.