Bats’ Best Friend

Bats have long been the subjects of mystery. Much of the stage has been taken up by vampire bats – technically, a species of the subfamily Desmodontinae – as blood-sucking manifestations of fear and fantasy horror. They inhabit our literature and our nightmares and fly across our movie screens with the power to shape shift into Dracula and a penchant for Halloween hangouts with witches and black cats.

The advent of the coronavirus turned these creatures of the night into real-life monsters – prime suspects, some would say, for spreading a virus that has killed more than 600,000 Americans and 4 million people worldwide.

But there’s a bright side to these nocturnal creatures that just might redeem them. They may also hold the secret to humankind’s salvation – they are immune to the very virus that has been killing us. 

Liliana M. Davalos, a professor in Stony Brook University’s Department of Ecology and Evolution, is one of the world-renowned researchers looking to uncover the mysteries of these winged mammals of the order Chiroptera. She has been working for the past few years to understand how their genomic and molecular evolution has resulted in their immunity to severe acute respiratory syndrome coronavirus, or SARS-CoV-2. 

“One of the problems with the human pathogen is that the virus has such terrible consequences, particularly for the elderly or people under particular kinds of treatment,” Davalos said, referring to those with weakened immune systems such as cancer patients. “But for other kinds of people that are young [or healthier], it doesn’t seem to have as much of an effect. That tells us something about the condition of the organism that the virus interacts with.” 

Even though she doesn’t work with the exact species of bats involved in the spread of COVID-19, Davalos is on a quest for answers to what she sees as fundamental questions: “Does the genome of bats have the same elements as humans? If we created a model of the immune response of the bat, how would it differ to that of a human?”

Davalos’ study on bat genomic adaptations, published last July, was part of the Bat1K Project – an initiative by Nature, the leading international journal of science. It brought together a consortium of researchers like Davalos with biologists, conservationists and plain old bat-lovers to sequence the genomes of all 1,400 living bat species. The project provides one of the most extensive studies of the bat genomes to date.

“Our reference-quality bat genomes provide the resources required to uncover and validate the genomic basis of adaptations of bats,” according to the study, which featured the contributions of more than a dozen scientists.  It also predicted that these genomes will “stimulate new avenues of research that are directly relevant to human health and disease.”

The study revealed that bats have developed anti-inflammatory responses to viruses as well as an expansion of an anti-viral gene, which contributes to their exemplary immunity.

How the virus developed into a human pathogen is still unknown, according to a recent report published by the World Health Organization (WHO). President Joseph R. Biden ordered a deeper look into the origins of COVID-19, including whether the virus may have leaked from a lab in Wuhan, China – the city that was the global ground zero of the pandemic. After a 90-day investigation, United States intelligence agencies issued an inconclusive report, citing the Chinese government’s unwillingness to share essential data. But the review settled one key issue – the virus was not developed as a biological weapon.

While both origin stories remain plausible, the prevailing theory in some circles is that the virus was transmitted from an infected animal. More than a dozen researchers from around the world were involved in the WHO study, which analyzed surveillance data of early cases of COVID-19 and genomic data of the virus. The research found related coronaviruses in bats and pangolins – scaly nocturnal anteaters that live in Asia and sub-Saharan Africa. Bats remain the prime suspect, as they carry two strains of SARS-CoV sharing more than 90 percent similarity to COVID-19. 

Davolos detailed the difficulty of narrowing down the development of the virus. “There is a very large gap, biological gap, that happens when a virus that circulates in wild populations of bats, for it to become a human pathogen. That gap persists. … We still don’t know how the virus evolved, what changes it underwent. … We have … this darkness with regard to this.” 

Davalos began her journey into bat genomic research after finishing her undergraduate studies in biology at the University of Valle in her native Colombia. She continued her education at Columbia University in New York, earning a master’s degree, then a doctorate in ecology, evolution and environmental biology.

Although her focus of study was birds, she ended up accepting a post-graduate position as a research associate at the American Museum of Natural History in Manhattan, where her interest shifted to bat evolution and genomics. Since then, she has worked on several studies relating to the morphology and characteristics of neotropical and frugivorous, or fruit-eating bats.

Now, her research focuses on the evolution of bat noses and the creatures’ immunological adaptations.

“For the longest time, I think roughly since 2014, I have become very interested in the olfactory receptors of bats,” Davalos said. “So by the time the pandemic came around, we had this unique data set that no one else in the world had, that was focused on the genetics, and the morphology of bat noses.” 

Stony Brook researcher, Laurel Yohe, worked alongside Davalos for her dissertation on the genetic evolution of bat noses. “Specifically what we’re looking at is why bats are able to be infected or be potential reservoirs for coronaviruses, but not manifest any symptoms,” Yohe said, discussing the work she did in collaboration with Davalos. “And we’re particularly focusing on the sense of smell per se, or noses, because the nose is actually ground zero for where the SARS-CoV-2 virus enters the cells. So there’s these mucus-producing cells within your nasal cavity that are directly attacked and are expressed with different proteins that allow the virus to enter into the body.”

This research can provide more context for studies of COVID-19 and how it has spread among humans. It may also shed light on other SARS-type diseases – because how bats tolerate coronavirus infections may hold clues for the human species.  

As the report of her study in Nature concluded: “This is of particular global relevance … and ultimately may provide solutions to increase human survivability – thus providing a better outcome for this, and future, pandemics.”