Ultrastructural Study of Rotavirus Replication and Localization of the Intermediate Capsid Protein VP6

Rotavirus, a triple-layered non-enveloped member of the Reoviridae family, obtained a transient membrane envelope when newly synthesized subviral particles bud into the endoplasmic reticulum (ER). As rotavirus particles mature, they lose their transient membrane and obtain outer layer. It is mostly believed that only double layered particles bud into the ER. The present study describes that the single layered particles can also bud into the ER and become the immediate precursors of the mature virions. Virus replication was studied within a line of African green monkey kidney (BSC-1)cells infected with simian rotavirus SA11. The virus intermediate capsid protein (VP6) was localized within the infected cells using protein A-gold. Monospecific antibody to VP6 was the primary antibody. The electron micrographs of budding sites of ER showed two different sizes of subviral particles. The gold particles were seen on the double layered particles and very little in the cytoplasm and some on ER or very close to it. These results indicate that the single layered particles are also capable of being the precursor of the triple layered and obtain the VP6 while budding into the ER.