Native VLPs like the ones we have produced allow the viral proteins to be presented to the immune system in the same conformation as in the virion for effective B and T cell response [31] . VLPs are particularly effective in producing a protective antibody response because of their virus-like size range, their particulate nature, and their virus-like dense, repetitive and ordered surface structure [31, 36] . The spacing of the antigenic epitopes on the VLP is also optimal for B cell activation [31] : EM analysis showed that our particles resembled the real virus in terms of size and surface structure [63, 64] . The image in Figure 2D is the first elucidation of VLP structure of any paramyxovirus imaged by CryoEM, and it provides a careful assessment of their morphology; it alludes to a surface similar to that revealed for measles virus by the same imaging technique (Dr. Elizabeth Wright, Emory University). The proteins on the VLP surface are clearly visible here; the average distance between the spikes was 9.13 nm and standard deviation was 1.72 nm. This is of interest given that epitopes spaced between 5 and 10 nm are known to be sufficient to drive optimal B cell activation [36] .