Finally, as described above, our VLPs were highly effective as immunogens, able to induce neutralizing antibody response in all animals with primary inoculation of as little as 7 mg VLP protein each. Fusogenic property of our VLPs may be critically relevant in this regard in the light of recent findings, and would need to be experimentally verified by comparing the potency of fusioncompetent and fusion-defective VLPs as vaccine [68] .