Neutralizing antibody response is the critical correlate of protection mediated by prophylactic vaccines [53, 54] and native VLPs promise to be highly effective prophylactic vaccines for paramyxoviruses like NiV, and others like NDV and measles where neutralizing immune response is known to play a pivotal role in protection against disease [53, 54, 55, 74] . Our VLPs were highly effective immunogens, and all, especially in the three higher treatment groups produced high levels of response by day 35 ( Figures 5A) . Importantly, NiV VLPs were able to induce neutralizing antibodies. This response was clearly dose-dependent ( Figure 5B ). All ten mice receiving a primary inoculation of 7 or 14 mg VLPs (subgroup C and D) were able to produce such response; but even of those animals that received a first dose of only 3.5 or 1.75 ug/mouse (treatment group B and A respectively), 3 of 5 and 1 of 5 produced neutralizing antibodies. Neutralization antibody response was first seen on day 28, and increasing titers were seen in some animals within a week of it; we believe that this response, induced by our non-replicating and potentially safe particles, formulated without adjuvant, compares favorably with the levels of such response induced at an equivalent time point by some replication competent pseudotype viruses [34] .