Dr. Ram Savan is an Associate Professor in the Department of Immunology at the University of Washington. His research focuses on human genetic variations in immune genes affecting viral clearance.
Ram Savan, PhD
Journal of Interferon and Cytokine Research: When did you get interested in type III interferon (IFN)/IFN-lambda research?
Ram Savan: I was a fellow in Howard Young's laboratory at the National Cancer Institute, National Institutes of Health (NIH). In his laboratory, there was a lot of IFN work going on. My interest was in type II IFN (IFN-gamma) and its regulation. During that time, I attended a cytokine meeting, and listening to IFN lambda talks it dawned on me that not much was known about type III IFNs except that they were very similar to type I IFNs—they induced an antiviral program, which acted on epithelial cells. It was unclear why type III IFNs are much weaker than type I IFNs. These differences were interesting, but at the same time I was curious to know why we would require 2 IFN families, which essentially engage similar antiviral pathways.
JICR: How does IFN-lambda differ from IFN-beta in its induction and the response it drives?
Ram Savan: Type III IFN signals through its own separate receptor, which is a heterodimer of lambda receptor 1 and a common receptor IL-10RA. The lambda receptor is only expressed on epithelial cells predominantly on mucosal surfaces. Lambda receptor is usually not expressed on most of the immune cells. I know that some work from a couple of groups, including Emily Hemann's laboratory at The Ohio State University, has shown that the lambda receptor is expressed on some immune cells. But the relation of receptor expression is unclear.
Type I IFN receptors are expressed on all nucleated cells. The question is, why is lambda sensing mostly restricted to the mucosal cell surfaces. One reasoning is that lambda induces weaker antiviral activity than type I IFN, probably because it has an additional responsibility of maintaining barrier integrity of the mucosal tissue. Damaging the mucosal tissue would be counterproductive during an infection as it might lead to secondary infections.
Although the biggest difference is the tissue specificity, IFN lambdas are known to be highly effective against certain viruses, including hepatitis C virus (HCV), which infects the liver. Single nucleotide polymorphisms in the IFN-lambda locus determines susceptibility to HCV. Recent work from other groups have also shown that viruses that infect mucosal surfaces such as norovirus, influenza A virus, and SARS-CoV-2 are also susceptible to IFN-lambda-mediated restriction.
JICR: There are 3 IFN-lambda genes in humans—do they have different functions?
Ram Savan: Actually, there are 4 IFN-lambda genes: lambda-1, lambda-2, lambda-3, and the most recently discovered member, lambda-4. A lot of work has been done on the first 3 genes, and currently, the functional role for lambda-4 is being investigated. Although it is unclear whether there are specific roles for these lambda genes, we do know that lambda genes have distinct binding and activation capacities. Lambda-3 has the strongest antiviral activity, compared with lambda-2 or lambda-1. But if you look at the tissue expression, lambda-1 is the most highly expressed in the lung. It is unclear whether there is a tissue-specific expression pattern of lambdas that correlates with their function. This is a difficult problem to address as mice do not express all the lambda genes, making it hard to tease out their specific activities. Clearly, there is a lot of work to be done in this area.
JICR: How does IFN-lambda protect us against viruses?
Ram Savan: IFN-lambda activates similar interferon stimulated genes (ISGs) as type I IFN does, but recent investigations have revealed that lambda also activates genes that are important to maintain tissue integrity without damaging the epithelial barrier, which is being investigated by Adriana Forero, a new investigator also at The Ohio State University. The most basic activity of IFNs is to activate these ISGs in a nonspecific manner; these ISGs, in turn, can block specific viruses. Among the hundreds of ISGs that are induced—some of which are specific to certain viruses—they act by either blocking the entry, replication, or egress of the virus from the cell.
JICR: Is IFN-lambda an approved therapeutic?
Ram Savan: Initially, IFN lambda was developed for clinical use against HCV. A number of companies conducted clinical trials and found it to be efficacious. I am not sure whether any compounds received Food and Drug Administration (FDA) approval because better direct-acting antiviral drugs against HCV have been developed and are now in the clinic curing patients. Now, for SARS-CoV-2, some clinical trials of IFN-lambda therapy are underway as well.
JICR: Your studies have identified a novel role for ISGs in directing antiviral defense. Are any ISGs more important than others in fighting off viruses?
Ram Savan: For the past 5–6 years, our laboratory is focused on identifying specific functions for ISGs. Hundreds of ISGs are induced during IFN activation. Most of the ISGs are conserved between bony fish and humans, and this conservation hints at specific functions. Although the functions of the majority of the ISGs are still unknown, the questions that we are currently focusing on are as follows: are there specific activities for the ISGs and are there certain ISGs that are more active against specific viruses?
I will give you 2 specific examples of our efforts in this area. Recently our laboratory found the mechanism of action of an ISG called ZAP—zinc-finger antiviral protein—which has specific activity against alphavirus. ZAP traffics to the endosomal membrane to restrict alphavirus where they replicate. A recent study from our laboratory—which will be published very soon—found a splice form of OAS1 called OAS1-p46 that exhibits pan-antiviral activity against plus-stranded RNA viruses. This OAS1 isoform enters the viral replication organelles and activates RNAseL activity that, in turn, neutralizes the virus. Frank Soveg and Johannes Schwerk found that OAS1-p46 is highly active against West Nile virus, Zika viruses, and SARS-CoV-2. More intriguingly, certain human populations do not express OAS1-p46 and they are natural human knockouts for this gene. We found that patients who do not express OAS1-p46 present with more severe COVID-19 disease.
JICR: Does IFN-lambda play a role in protection or disease in COVID-19?
Ram Savan: There is conflicting data on the protection and exacerbation of disease by IFN lambda. Some studies are pointing at beneficial outcomes if treated early with IFN-lambda. The question is, when do you administer IFN-lambda? If you treat patients with IFN-lambda early on during infection, I think it would be protective, but once the infection has set in and there is a lot of inflammation in the lung, treating with IFN-lambda is probably counterproductive, and there are some data showing that it might exacerbate COVID-19 disease. More studies on the timing of IFN-lambda treatments during the disease could provide insights into its efficacy against SARS-CoV-2, which causes COVID-19 disease.
JICR: What is the future for IFN-lambda research?
Ram Savan: Although IFN-lambda has been studied for over 2 decades, there is lot to learn about this IFN. Some areas we are interested in are what are these different IFN-lambdas doing? Do they have tissue-specific expression and activity? Do they have specific activity against certain mucosal pathogens? What determines the induction pattern of IFN-lambda and is there cell-type specificity? Are there negative and positive regulators of IFN lambda expression and signaling and factors that determine the temporal induction pattern of type I and type III IFNs?
We also need to generate new tools and animal models that will help clarify these questions and help us better understand the role of type III IFNs at the mucosal surfaces.
JICR: What would you suggest are important or emerging new areas of research for new investigators to consider working on in the area of IFN and cytokine research?
Ram Savan: We have a broad understanding of how type I and type III IFNs work. We are currently scratching the surface of ISG functions and identifying ISGs that neutralize specific viruses. Work in this area would be critical for developing antiviral therapeutics for new and emerging viral infections.
JICR: What advice can you give to new investigators?
Ram Savan: The recent pandemic has been especially hard on new investigators who just started their laboratories. They have not been able to get back to the laboratory and their productivity might be severely impacted. They may not be able to hire people, and funding for the laboratory could be hard to get initially. Although these are not only issues for new investigators, they impact all of us but new investigators are the most affected. New investigators should have an open line of communication with their peers and mentors. The university leadership should find ways to support new investigators, and at the same time be sure they are given enough time to get back on their feet after this pandemic. New investigators need to talk to their department chairs and make sure that 2020 was not counted against their tenure clock.
Broadly, I want to emphasize that when you are starting up your own laboratory, focus on a couple of projects and do not over stretch yourself. You can say no to opportunities to serve on committees, as it is a huge investment of time initially. Try to get a few articles out early, it does not have to be the most impactful article in the field, but having your name out with solid work is very important as this has implications for grant applications, finding good research team members and to be noticed by your peers. Be a kind and a generous mentor as the future of science is in your hands. Most importantly, have fun doing science!
