Mice in groups of five were inoculated subcutaneously with four different concentrations of purified VLPs and boosted as described under Methods. The negative control group of five mice were inoculated with sterile endotoxin free PBS for each inoculation. The mice were bled from the submandibular vein on the day before primary inoculation, and then on days 14, 21, 28 and 35. For initial evaluation, sera from each treatment group were pooled, and the IFA method used to determine levels of NiV-specific antibodies. The results in Figure 5A show that titers (reciprocal of the highest serum dilution showing reactivity) increased with time post primary inoculation, i.e., the highest titers (1:2560) were seen on day 35. Titers also increased with VLP dosage although by day 35, the three higher treatment groups seemed to produce similar titers. As expected, the mice in the negative control group remained nonresponsive.