# Comparative analysis of NSP5/VP2-induced viroplasm-like structures in rotavirus species A to J

## TL;DR

The study compares how different rotavirus species form viroplasm-like structures using NSP5 and VP2 proteins, which could help develop ways to stop infections.

## Contribution

The study identifies conserved VP2 regions critical for viroplasm-like structure formation across all rotavirus species A–J.

## Key findings

- NSP5 and VP2 from all tested rotavirus species A–J form viroplasm-like structures.
- Conserved residues in VP2 are essential for viroplasm-like structure formation across species.
- Interspecies viroplasm-like structures form between closely related rotavirus pairs.

## Abstract

Rotavirus (RV) is classified into nine species, A–D and F–J,
with RV species A (RVA) being the most extensively studied. While RVA
infects infants and young animals, non-RVA species infect adult humans,
various mammals, and birds. However, the lack of appropriate research tools
has limited our understanding of non-RVA life cycles. RVA replication and
assembly occur in cytosolic inclusions termed viroplasms. We recently
identified viroplasm-like structures (VLS) composed of NSP5 and NSP2 in
non-RVA. In this context, globular VLS induced by NSP2 formed in RVA, RVB,
RVD, RVF, RVG, and RVI, but not in RVC, RVH, and RVJ. Additionally, in RVA,
VLS can also be formed through the co-expression of NSP5 with VP2. Here, we
report that VP2-induced VLS formed in RV species A to J, with notable
formation in RVH and RVJ, where NSP2 RVH or RVJ was also recruited into
VLSs. The NSP5 C-terminal region in non-RVA is required for association with
VP2 and forming VLS. Mutation of conserved VP2-L124 in RVA to alanine
disrupts viroplasm formation, impairing RV replication. Equivalent residues
within the same predicted VP2 region disrupt VLS formation across non-RVA.
We also observed interspecies VLS formation, most notably between the
closely related pairs RVA–RVC, RVH–RVJ, and RVD–RVF.
Interestingly, substituting the N-terminal region of VP2 from RVB with that
of VP2 from RVG supported VLS formation with NSP5 from RVB in avian cells.
Elucidating the formation of viroplasms is essential for developing
strategies to halt infection across RV species A to J.

Rotaviruses (RV) are a group of viruses classified into species A through J,
with species A being the best understood. Other RV species infecting animals
and humans are less studied due to limited research tools. In RVA, the virus
replicates in specialized compartments called viroplasms formed in the
cytoplasm by viral proteins, including NSP5, NSP2, and VP2. In this study,
we explored how similar structures, termed viroplasm-like structures (VLS),
are formed by proteins of RV species A–J. We found that for all
tested RV species, NSP5 and VP2 form VLSs. We also identified key regions in
the VP2 protein that are essential for forming these structures.
Understanding how viroplasms form across different RV species may help
develop new strategies to block infection in humans and animals.