Bat ASC2 suppresses inflammasomes and ameliorates inflammatory diseases.

Bats are special in their ability to live long and host many emerging viruses. Our previous studies showed that bats have altered inflammasomes, which are central players in aging and infection. However, the role of inflammasome signaling in combating inflammatory diseases remains poorly understood. Here, we report bat ASC2 as a potent negative regulator of inflammasomes. Bat ASC2 is highly expressed at both the mRNA and protein levels and is highly potent in inhibiting human and mouse inflammasomes. Transgenic expression of bat ASC2 in mice reduced the severity of peritonitis induced by gout crystals and ASC particles. Bat ASC2 also dampened inflammation induced by multiple viruses and reduced mortality of influenza A virus infection. Importantly, it also suppressed SARS-CoV-2-immune-complex-induced inflammasome activation. Four key residues were identified for the gain of function of bat ASC2. Our results demonstrate that bat ASC2 is an important negative regulator of inflammasomes with therapeutic potential in inflammatory diseases.

Robust dengue virus infection in bat cells and limited innate immune responses coupled with positive serology from bats in IndoMalaya and Australasia.

Natural reservoir hosts can sustain infection of pathogens without succumbing to overt disease. Multiple bat species host a plethora of viruses, pathogenic to other mammals, without clinical symptoms. Here, we detail infection of bat primary cells, immune cells, and cell lines with Dengue virus. While antibodies and viral RNA were previously detected in wild bats, their ability to sustain infection is not conclusive. Old-world fruitbat cells can be infected, producing high titres of virus with limited cellular responses. In addition, there is minimal interferon (IFN) response in cells infected with MOIs leading to dengue production. The ability to support in vitro replication/production raises the possibility of bats as a transient host in the life cycle of dengue or similar flaviviruses. New antibody serology evidence from Asia/Pacific highlights the previous exposure and raises awareness that bats may be involved in flavivirus dynamics and infection of other hosts.

Exploring bat-inspired cyclic tryptophan diketopiperazines as ABCB1 Inhibitors.

Chemotherapy-induced drug resistance remains a major cause of cancer recurrence and patient mortality. ATP binding cassette subfamily B member 1 (ABCB1) transporter overexpression in tumors contributes to resistance, yet current ABCB1 inhibitors have been unsuccessful in clinical trials. To address this challenge, we propose a new strategy using tryptophan as a lead molecule for developing ABCB1 inhibitors. Our idea stems from our studies on bat cells, as bats have low cancer incidences and high ABCB1 expression. We hypothesized that potential ABCB1 substrates in bats could act as competitive inhibitors in humans. By molecular simulations of ABCB1-substrate interactions, we generated a benzylated Cyclo-tryptophan (C3N-Dbn-Trp2) that inhibits ABCB1 activity with efficacy comparable to or better than the classical inhibitor, verapamil. C3N-Dbn-Trp2 restored chemotherapy sensitivity in drug-resistant human cancer cells with no adverse effect on cell proliferation. Our unique approach presents a promising lead toward developing effective ABCB1 inhibitors to treat drug-resistant cancers.

Application of a bespoke monoclonal antibody panel to characterize immune cell populations in cave nectar bats.

Among their many unique biological features, bats are increasingly recognized as a key reservoir of many emerging viruses that cause massive morbidity and mortality in humans. Bats are capable of harboring many of these deadly viruses without any apparent signs of pathology, in a mechanism known as viral disease tolerance. However, the immunological mechanisms behind viral tolerance remain poorly understood. As a non-model organism species, there are very limited research resources and tools available to study bat immunology. In the cave nectar bat Eonycteris spelaea, we have a panel of monoclonal antibodies (mAbs) against major immune markers. An immunophenotyping survey of major immune compartments and barrier sites using these mAbs reveals differences in the immunological landscape of bats.

Establishment of a Captive Cave Nectar Bat (Eonycteris spelaea) Breeding Colony in Singapore.

Bats are known natural reservoirs of several highly pathogenic zoonotic viruses, including Hendra virus, Nipah virus, rabies virus, SARS-like coronaviruses, and suspected ancestral reservoirs of SARS-CoV-2 responsible for the ongoing COVID-19 pandemic. The capacity to survive infections of highly pathogenic agents without severe disease, together with many other unique features, makes bats an ideal animal model for studying the regulation of infection, cancer, and longevity, which is likely to translate into human health outcomes. A key factor that limits bat research is lack of breeding bat colonies. To address this need, a captive bat colony was established in Singapore from 19 wild-caught local cave nectar bats. The bats were screened for specific pathogens before the start of captive breeding. Custom-made cages and an optimized diet inclusive of Wombaroo dietary formula, liquid diet, and supplement of fruits enabled the bats to breed prolifically in our facility. Cages are washed daily and disinfected once every fortnight. Bats are observed daily to detect any sick bat or abnormal behavior. In addition, bats undergo a thorough health check once every 3 to 4 mo to check on their overall wellbeing, perform sampling, and document any potential pregnancy. The current colony houses over 80 bats that are successfully breeding, providing a valuable resource for research in Singapore and overseas.

Interferon Regulatory Factors IRF1 and IRF7 Directly Regulate Gene Expression in Bats in Response to Viral Infection.

Bat cells and tissue have elevated basal expression levels of antiviral genes commonly associated with interferon alpha (IFNα) signaling. Here, we show Interferon Regulatory Factor 1 (IRF1), 3, and 7 levels are elevated in most bat tissues and that, basally, IRFs contribute to the expression of type I IFN ligands and high expression of interferon regulated genes (IRGs). CRISPR knockout (KO) of IRF 1/3/7 in cells reveals distinct subsets of genes affected by each IRF in an IFN-ligand signaling-dependent and largely independent manner. As the master regulators of innate immunity, the IRFs control the kinetics and maintenance of the IRG response and play essential roles in response to influenza A virus (IAV), herpes simplex virus 1 (HSV-1), Melaka virus/Pteropine orthoreovirus 3 Melaka (PRV3M), and Middle East respiratory syndrome-related coronavirus (MERS-CoV) infection. With its differential expression in bats compared to that in humans, this highlights a critical role for basal IRF expression in viral responses and potentially immune cell development in bats with relevance for IRF function in human biology.