Poxvirus Entry Mechanism and Membrane Fusion Regulation

I. Investigation of vaccinia virus membrane fusion complex

Vaccinia virus is a large enveloped DNA virus and belongs to the poxvirus family. Vaccinia virus has a wide host range and infects different cell types in vitro and in vivo. Vaccinia mature virus contains four enveloped proteins for cell attachment and a fusion complex of eleven enveloped proteins for membrane fusion. We previously identified four mature virus attachment proteins and studied the viral endocytic pathway. We are now focusing on vaccinia virus fusion protein complex. We aim to dissect the structure and function of each components of viral fusion complex in order to understand the membrane fusion mechanism. In the future, we will expand our study into other DNA viruses such as African swine fever virus.

II. Investigation of vaccinia viral fusion suppressor proteins

Because virus-mediated membrane fusion often occurs in acidic endosomes and acidic pH serves as an environmental cue to induce conformational changes of viral fusion protein to execute membrane fusion. We recently identified a unique protein A26 on mature virus which, upon acidification, had conformational changes through protonation of specific His residues, providing a critical mechanism to de-repress fusion complex leading to membrane fusion activation. Therefore, vaccinia virus not only has a complicated fusion protein complex but also has a unique viral fusion suppressor protein, such as A26, to control where and when membrane fusion should be activated during virus entry. In the future, structure and functional analyses of viral fusion suppressor proteins will be explored.

III. Host specific influences on virus entry, replication and egress

When we deleted A26 ORF from wild type vaccinia virus WR strain (WT-WR), we found that WRΔA26 infections into murine bone marrow derived macrophages (BMDM) were better than WT-WR virus with high levels of early and late gene expression. Subsequently analyses revealed that WT-WR entry into BMDM induced type 1 interferon response whereas WRΔA26 was able to escape such innate immune detection. Currently, we are trying to understand the cellular factors involved in such a differential interferon induction pathway. We anticipate such knowledge will expand the usefulness of designing vaccinia virus as a better vaccine vector or an oncolytic agent for cancer treatment.

• Education
• Achievements & Honors
• Selected publications
• Lab members

• PDF, 1989-1992, Center for Cancer Research, MIT, USA
• PDF, 1988, Bristol-Myers Squibb Pharmaceutical Research Institute, Seattle, USA
• Ph.D., 1988, Department of Microbiol. & Immunol., University of Washington at Seattle, USA
• BS, 1982, Department of Agriculture Chemistry, National. Taiwan University

• 2002, Academia Sinica Early-Career Investigator Research Achievement Award
• 2006, Research Excellence Award, National Science and Technology Council

1. Hyun, J., Hsieh, L.T., Ayala, R., Chang, W., and Wolf, M. (2025). Methods to Study Poxvirus Structures by Cryo-EM Imaging Modalities. Methods Mol Biol 2860, 191-218. 10.1007/978-1-0716-4160-6_13.
2. Chiu, H.J., Wang, H.C., and Chang, W. (2025). Structural dissection of vaccinia G9 identifies residues essential for membrane fusion and complex assembly. J Virol, e0072325. 10.1128/jvi.00723-25.
3. Kulkarni, R., Kasani, S.K., Tsai, C.Y., Tung, S.Y., Yeh, K.H., Yu, C.A., and Chang, W. (2023). FAM21 is critical for TLR2/CLEC4E-mediated dendritic cell function against Candida albicans. Life Sci Alliance 6. 10.26508/lsa.202201414.
4. Kao, S., Kao, C.F., Chang, W., and Ku, C. (2023). Widespread Distribution and Evolution of Poxviral Entry-Fusion Complex Proteins in Giant Viruses. Microbiol Spectr 11, e0494422. 10.1128/spectrum.04944-22.
5. Kao, C.F., Tsai, M.H., Carillo, K.J., Tzou, D.L., and Chang, W. (2023). Structural and functional analysis of vaccinia viral fusion complex component protein A28 through NMR and molecular dynamic simulations. PLoS Pathog 19, e1011500. 10.1371/journal.ppat.1011500.
6. Kao, C.F., Liu, C.Y., Hsieh, C.L., Carillo, K.J.D., Tzou, D.L., Wang, H.C., and Chang, W. (2023). Structural and functional analyses of viral H2 protein of the vaccinia virus entry fusion complex. J Virol 97, e0134323. 10.1128/jvi.01343-23.
7. Wu, D., Lou, Y.C., Chang, W., and Tzou, D.M. (2021). NMR assignments of vaccinia virus protein A28: an entry-fusion complex component. Biomol NMR Assign 15, 117-120. 10.1007/s12104-020-09993-0.
8. Kulkarni, R., Wiemer, E.A.C., and Chang, W. (2021). Role of Lipid Rafts in Pathogen-Host Interaction - A Mini Review. Front Immunol 12, 815020. 10.3389/fimmu.2021.815020.
9. Kulkarni, R., Chen, W.C., Lee, Y., Kao, C.F., Hu, S.L., Ma, H.H., Jan, J.T., Liao, C.C., Liang, J.J., Ko, H.Y., et al. (2021). Vaccinia virus-based vaccines confer protective immunity against SARS-CoV-2 virus in Syrian hamsters. PLoS One 16, e0257191. 10.1371/journal.pone.0257191.
10. Hong, G.C., Tsai, C.H., and Chang, W. (2020). Experimental Evolution To Isolate Vaccinia Virus Adaptive G9 Mutants That Overcome Membrane Fusion Inhibition via the Vaccinia Virus A56/K2 Protein Complex. J Virol 94. 10.1128/JVI.00093-20.
11. Chang, H.W., Yang, C.H., Luo, Y.C., Su, B.G., Cheng, H.Y., Tung, S.Y., Carillo, K.J.D., Liao, Y.T., Tzou, D.M., Wang, H.C., and Chang, W. (2019). Vaccinia viral A26 protein is a fusion suppressor of mature virus and triggers membrane fusion through conformational change at low pH. PLoS Pathog 15, e1007826. 10.1371/journal.ppat.1007826.