Fig. 1

Classification of various VLPs structure. a For enveloped VLPs, expression of one (i) or two glycoproteins will form a single layer, as demonstrated by the expression of influenza virus hemagglutinin alone or co-expression of both hemagglutinin and neuraminidase, respectively. Expression of more than three glycoproteins (iii) will also form a single layer VLP. Double layered enveloped VLPs can be formed by the multiple glycoproteins on their surface that can have two (iv) or more than three glycoproteins (v). b For non-enveloped VLPs, single layered non-enveloped VLPs can be assembled from a single protein (i) or two proteins(ii). Double layered non-enveloped VLPs can be assembled from two proteins (iii) or more than three proteins (iv). Triple layered VLPs (v) have been assembled from more than three proteins