Timothy Tan

I am a research fellow in cancer immunology at the Cancer Science Institute at the National University of Singapore. I study oncoviruses to develop prophylactic strategies, and to learn more about the intricacies of cellular biology. Currently, I am investigating antibody responses to immunodominant viral glycoproteins, and identifying genetic factors that increase the risk of contracting cancer upon oncovirus infection. To address these questions, I develop high-throughput methodologies, and combine biochemical, biophysical, optical, and computational tools.

selected publications

Evidence of antigenic drift in the fusion machinery core of SARS-CoV-2 spike

Tan TJC, Verma AK, Odle A, Lei R, Meyerholz DK, Matreyek KA, Perlman S, Wong LYR, and Wu NC

Proceedings of the National Academy of Sciences (2024)

Abs HTML PDF Supp

Antigenic drift of SARS-CoV-2 is typically defined by mutations in the N-terminal domain and receptor binding domain of spike protein. In contrast, whether antigenic drift occurs in the S2 domain remains largely elusive. Here, we perform a deep mutational scanning experiment to identify S2 mutations that affect binding of SARS-CoV-2 spike to three S2 apex public antibodies. Our results indicate that spatially diverse mutations, including D950N and Q954H, which are observed in Delta and Omicron variants, respectively, weaken the binding of spike to these antibodies. Although S2 apex antibodies are known to be nonneutralizing, we show that they confer protection in vivo through Fc-mediated effector functions. Overall, this study indicates that the S2 domain of SARS-CoV-2 spike can undergo antigenic drift, which represents a potential challenge for the development of more universal coronavirus vaccines.
High-throughput identification of prefusion-stabilizing mutations in SARS-CoV-2 spike

Tan TJC, Mou Z, Lei R, Ouyang WO, Yuan M, Song G, Andrabi R, Wilson IA, Kieffer C, Dai X, Matreyek KA, and Wu NC

Nature Communications (2023)

Abs HTML PDF Supp

Designing prefusion-stabilized SARS-CoV-2 spike is critical for the effectiveness of COVID-19 vaccines. All COVID-19 vaccines in the US encode spike with K986P/V987P mutations to stabilize its prefusion conformation. However, contemporary methods on engineering prefusion-stabilized spike immunogens involve tedious experimental work and heavily rely on structural information. Here, we establish a systematic and unbiased method of identifying mutations that concomitantly improve expression and stabilize the prefusion conformation of the SARS-CoV-2 spike. Our method integrates a fluorescence-based fusion assay, mammalian cell display technology, and deep mutational scanning. As a proof-of-concept, we apply this method to a region in the S2 domain that includes the first heptad repeat and central helix. Our results reveal that besides K986P and V987P, several mutations simultaneously improve expression and significantly lower the fusogenicity of the spike. As prefusion stabilization is a common challenge for viral immunogen design, this work will help accelerate vaccine development against different viruses.
Sequence signatures of two IGHV3-53/3-66 public clonotypes to SARS-CoV-2 receptor binding domain

Tan TJC*, Yuan M*, Kuzelka K, Padron GC, Beal JR, Chen X, Wang Y, Rivera-Cardona J, Zhu X, Stadtmueller BM, Brooke CB, Wilson IA^, and Wu NC^

Nature Communications (2021)

Abs HTML PDF Supp

Since the COVID-19 pandemic onset, the antibody response to SARS-CoV-2 has been extensively characterized. Antibodies to the receptor binding domain (RBD) on the spike protein are frequently encoded by IGHV3-53/3-66 with a short complementarity-determining region (CDR) H3. Germline-encoded sequence motifs in heavy chain CDRs H1 and H2 have a major function, but whether any common motifs are present in CDR H3, which is often critical for binding specificity, is not clear. Here, we identify two public clonotypes of IGHV3-53/3-66 RBD antibodies with a 9-residue CDR H3 that pair with different light chains. Distinct sequence motifs on CDR H3 are present in the two public clonotypes that seem to be related to differential light chain pairing. Additionally, we show that Y58F is a common somatic hypermutation that results in increased binding affinity of IGHV3-53/3-66 RBD antibodies with a short CDR H3. These results advance understanding of the antibody response to SARS-CoV-2.