Biology subjects

Tan, H. C.

Publications and source records attributed to Tan, H. C..

4 recordsLinked to original sources

bioRxiv2025

In mitochondrial disease respiratory complex III2 assembles complex I via toxic intermediate

Mutations in mitochondrial complex I can cause severe metabolic disease. Although no treatments are available for complex I deficiencies, chronic hypoxia improves lifespan and function in a mouse model of the severe mitochondrial disease Leigh syndrome caused by mutation of complex I subunit NDUFS4. To understand the molecular mechanism of NDUFS4 mutant pathophysiology and hypoxia rescue, we investigated the structure of complex I in respiratory supercomplexes isolated from NDUFS4 mutant mice. We identified complex I assembly intermediates bound to complex III2, proving the cooperative assembly model. Further, an accumulated complex I intermediate is structurally consistent with pathological oxygen-dependent reverse electron transfer, revealing unanticipated pathophysiology and hypoxia rescue mechanisms. Thus, the build-up of toxic intermediates and not simply decreases in complex I levels underlie mitochondrial disease.

biochemistry↗

bioRxiv2021

Cell strain-derived induced pluripotent stem cell as a genetically controlled approach to investigating aging mechanisms and viral pathogenesis

The expansion of the geographic footprint of dengue viruses (DENVs) and their mosquito vectors have affected more than half of the global population, including older adults who appear to show elevated risk of severe dengue. Despite this epidemiological trend, how age and senescence impact virus-host interactions involved in dengue pathogenesis to increase the risk of severe dengue is poorly understood. Herein, we show that conversion of diploid cells with finite lifespan into iPSCs followed by differentiation back into cell strain can be an approach to derive genetically identical cells at different stages of senescence to study virus and aging host interactions. Our findings show that cellular senescence impact the host response to infection and the ensuing outcome. We suggest iPSC-derive cell strains as a potentially useful technical approach to genetically controlled host-virus interaction studies to understand how aging impact viral pathogenesis.

microbiology↗

bioRxiv2020

A Single Dose of Self-Transcribing and Replicating RNA Based SARS-CoV-2 Vaccine Produces Protective Adaptive Immunity In Mice

A self-transcribing and replicating RNA (STARR) based vaccine (LUNAR(R)-COV19) has been developed to prevent SARS-CoV-2 infection. The vaccine encodes an alphavirus-based replicon and the SARS-CoV-2 full length spike glycoprotein. Translation of the replicon produces a replicase complex that amplifies and prolong SARS-CoV-2 spike glycoprotein expression. A single prime vaccination in mice led to robust antibody responses, with neutralizing antibody titers increasing up to day 60. Activation of cell mediated immunity produced a strong viral antigen specific CD8+ T lymphocyte response. Assaying for intracellular cytokine staining for IFN-{gamma} and IL-4 positive CD4+ T helper lymphocytes as well as anti-spike glycoprotein IgG2a/IgG1 ratios supported a strong Th1 dominant immune response. Finally, single LUNAR-COV19 vaccination at both 2 g and 10 g doses completely protected human ACE2 transgenic mice from both mortality and even measurable infection following wild-type SARS-CoV-2 challenge. Our findings collectively suggest the potential of Lunar-COV19 as a single dose vaccine.

immunology↗

bioRxiv2020

Bivalent binding of a fully human IgG to the SARS-CoV-2 spike proteins reveals mechanisms of potent neutralization

In vitro antibody selection against pathogens from naive combinatorial libraries can yield various classes of antigen-specific binders that are distinct from those evolved from natural infection1-4. Also, rapid neutralizing antibody discovery can be made possible by a strategy that selects for those interfering with pathogen and host interaction5. Here we report the discovery of antibodies that neutralize SARS-CoV-2, the virus responsible for the COVID-19 pandemic, from a highly diverse naive human Fab library. Lead antibody 5A6 blocks the receptor binding domain (RBD) of the viral spike from binding to the host receptor angiotensin converting enzyme 2 (ACE2), neutralizes SARS-CoV-2 infection of Vero E6 cells, and reduces viral replication in reconstituted human nasal and bronchial epithelium models. 5A6 has a high occupancy on the viral surface and exerts its neutralization activity via a bivalent binding mode to the tip of two neighbouring RBDs at the ACE2 interaction interface, one in the "up" and the other in the "down" position, explaining its superior neutralization capacity. Furthermore, 5A6 is insensitive to several spike mutations identified in clinical isolates, including the D614G mutant that has become dominant worldwide. Our results suggest that 5A6 could be an effective prophylactic and therapeutic treatment of COVID-19.

microbiology↗