FIG 3.

Reciprocal NA inhibition (NAI) titers across a panel of N1 influenza viruses. The N1-I COBRA vaccinated sera (A) inhibited all representative viruses in the panel (B). The wild-type sera (B to E) elicited various levels of inhibition breadth from very broad (D) to narrow (C and E), but was not as broad as the N1-I COBRA. The enzyme-linked lectin assays (ELLAs) were performed with RDE-treated and heat-inactivated sera initially diluted to 1:100 followed by 2-fold dilutions. The limit of detection was defined as 2.0 log₁₀ NAI reciprocal titer. The mean log₁₀ NAI reciprocal titer that inhibited 50% of the NA activity with 95% confidence intervals was estimated with nonlinear regression of the ELLA dilution curves (Fig. S1 in the supplemental material).