An Aerolysin-like Pore-Forming Protein Complex Targets Viral Envelope to Inactivate Herpes Simplex Virus Type 1

Because most of animal viruses are enveloped, cytoplasmic entry of these viruses via fusion with cellular membrane initiates their invasion. However, the strategies in which host cells counteract cytoplasmic entry of such viruses are incompletely understood. Pore-forming toxin aerolysin-like proteins (ALPs) exist throughout the animal kingdom, but their functions are mostly unknown. In this study, we report that By-crystallin fused aerolysin-like protein and trefoil factor complex (beta gamma-CAT), an ALP and trefoil factor complex from the frog Bombina maxima, directly blocks enveloped virus invasion by interfering with cytoplasmic entry. beta gamma-CAT targeted acidic glycosphingolipids on the HSV type 1 (HSV-1) envelope to induce pore formation, as indicated by the oligomer formation of protein and potassium and calcium ion efflux. Meanwhile, beta gamma-CAT formed ring-like oligomers of similar to 10 nm in diameter on the liposomes and induced dye release from liposomes that mimic viral envelope. Unexpectedly, transmission electron microscopy analysis showed that the beta gamma-CAT-treated HSV-1 was visibly as intact as the vehicle-treated HSV-1, indicating that beta gamma-CAT did not lyse the viral envelope. However, the cytoplasmic entry of the beta gamma-CAT-treated HSV-1 into HeLa cells was totally hindered. In vivo, topical application of beta gamma-CAT attenuated the HSV-1 corneal infection in mice. Collectively, these results uncovered that beta gamma-CAT possesses the capacity to counteract enveloped virus invasion with its featured antiviral-acting manner. Our findings will also largely help to illustrate the putative antiviral activity of animal ALPs.

Automated summary

The study demonstrates that a toxin aerolysin-like protein and trefoil factor complex (βγ-CAT) from the frog Bombina maxima can directly block enveloped virus invasion by interfering with cytoplasmic entry, particularly inhibiting HSV-1 infection. βγ-CAT induces pore formation on the HSV-1 envelope, hindering viral entry into host cells and providing a potential antiviral strategy.