# CD36 is required for human sapovirus propagation

## TL;DR

Researchers discovered that the CD36 protein is essential for the propagation of human sapoviruses, which cause stomach flu, in human and non-human cells.

## Contribution

The study identifies CD36 as a critical host factor for propagation of multiple genotypes of human sapovirus.

## Key findings

- CD36 is required for propagation of 15 HuSaV genotypes in human-derived cells.
- Re-expression of CD36 in knockout cells restored propagation of most HuSaV strains.
- Human CD36 enabled propagation of several HuSaV genotypes in non-human cells.

## Abstract

Human sapoviruses (HuSaVs), which cause acute gastroenteritis, are highly diverse. Fifteen HuSaV genotype strains (GI.1-7, GII.1-5, -8, and GV.1-2) were efficiently propagated in the human duodenum-derived cell line HuTu80 when supplemented with conjugated bile acid (T. Oka, T.-C. Li, K. Yonemitsu, Y. Ami, et al., J Virol 98:e00639-24, 2024, https://doi.org/10.1128/jvi.00639-24). However, the host cellular factors involved in HuSaV infection and propagation remain unidentified. Using a knockout approach, we newly identified and confirmed that CD36 is a critical cellular protein for the propagation of all 15 HuSaV genotypes tested in HuTu80 cells. When the CD36 gene was re-expressed in CD36 gene knockout HuTu80 cells, all HuSaV genotype strains, except for GI.6 and GII.3, recovered their viral propagation ability. To further demonstrate that human CD36 is critical for HuSaV propagation, we expressed human CD36 in HuSaV-insensitive non-human origin cells. Of the 15 HuSaV genotype strains tested, 10 from GI, GII, and GV (GI.3, -5, -6, GII.1-3, -5, -8, GV.1, and GV.2) were propagated in Chinese Hamster Ovary-K1 cells, and six from GII (GII.1-5, -8) were propagated in Vero cells. Although there were differences in the propagation ability between the genotypes tested, at least one of the three cell lines engineered to express the human CD36 gene acquired HuSaV propagation potential, confirming that human CD36 is an essential cellular factor for HuSaV propagation.

The host cellular factor(s) involved in the infection and propagation of sapovirus, which causes acute gastroenteritis in humans, remain unclear. By using a loss-of-gene function approach with a potential physiological infection site derived from a human cell line clone, which caused a marked cytopathic effect related to human sapovirus (HuSaV) propagation, we identified that CD36 was essential for the propagation of all 15 genotype strains of HuSaV tested. We confirmed different effects on distinct genotypes of HuSaV propagation by the re-expression of human CD36 in HuTu80 cells and human CD36 introduced into two non-human HuSaV-insensitive cells. This finding is an important step toward understanding common and genogroup/genotype-specific HuSaV propagation mechanisms, and the development of methods to control this highly contagious virus, including research on the development of anti-viral drugs and the establishment of HuSaV-susceptible animal models in the future.