June 16, 2022

Dr. Kumar receives two NIH grants to study bacterial and viral infections of the eye

The Wayne State University School of Medicine’s Ashok Kumar, Ph.D., associate professor of Ophthalmology, Visual and Anatomical Sciences, has received a five-year R01 grant from the National Eye Institute and a two-year R21 grant from National Institute of Allergy and Infectious Diseases of the National Institutes of Health, totaling $2.4 million in support.

Ashok Kumar, Ph.D.

The NEI grant is focused on “Targeting NAD+ metabolism to ameliorate bacterial endophthalmitis.”

Patients who underwent eye surgeries or who experienced trauma to the eye often develop intraocular infections caused by bacteria, called endophthalmitis. If not diagnosed or treated promptly, these infections can cause partial or complete vision loss leading to blindness, and sometimes requires surgical removal of the eye.

“Over the last decade, our laboratory has been studying the pathobiology of bacterial endophthalmitis using mouse model and culture retinal cells,” Dr. Kumar said. “Using metabolomics and transcriptomics approaches, we discovered that energy metabolism is significantly perturbed in bacterial-infected eyes. During the initial funding period, we focused on AMP-activated protein kinase, a master regulator of energy metabolism, and found that AMPK activation exerts protective effects in the eye by reducing inflammation.”

Intrigued by the link between the cellular metabolism and the innate immunity, they recently discovered that a metabolite called “itaconate,” produced during cellular metabolism, plays a role in protecting the eye from abnormal inflammation during infection. They also show that this metabolite can be used with antibiotics to treat eye infections. “Our metabolomics analysis also revealed that bacterial infection rapidly depletes the nicotinamide adenine dinucleotide (NAD+) pool in the eye. In the renewed R01, we proposed to study NAD+ dysregulation during ocular infection. The major impact of this research will be to consider NAD+ supplements as an adjunct therapy to treat eye infections,” he said.

The multidisciplinary project bridges three distinct disciplines of microbiology, immunology and biochemistry, collectively known as immunometabolism.

“This is an emerging area of research that focuses on the role of metabolic reprogramming, including dynamic regulation of aerobic glycolysis, lipid synthesis and degradation, and mitochondrial activity on the outcome of immune responses. The long-term goal of our study is to determine how cellular metabolism of immune cells impacts their ability to kill pathogens and mount protective immune responses to defend the eye from infection,” Dr. Kumar said.

The second grant is focused on “ADAR1-mediated antiviral response in Zika Virus (ZIKV) infection.”

Emerging and re-emerging viruses have the potential to cause both localized outbreaks and pandemics with increased mortality and morbidity, as evidenced by the ongoing COVID-19 pandemic, along with the Zika virus epidemics in Brazil and Ebola outbreaks in Africa. Dr. Kumar’s laboratory is one of few in the world to study ocular complications of RNA viruses such as Zika, Dengue, Chikungunya and, now, SARS-CoV-2.

“The eye is protected from systemic viral infections by the presence of a blood-retinal barrier composed of unique cell types called endothelial and retinal pigment epithelial cells, or RPE. In our previous studies, we showed that ZIKV infects these cell type and causes retinal lesions in mouse eyes, which mimic ZIKV-associated ocular pathology in infants,” he said. “Once infected with ZIKV, host cells mount an innate immune response, predominantly by producing the interferons and IFN-stimulated genes, or ISGs. These antiviral responses promote inflammation and immune cell activation for viral clearance. The transcriptomic analysis of ZIKV-infected RPE revealed the induction of adenosine deaminases acting on RNA1, ADAR1, a potent ISG, which can exert pro- or antiviral activity by A-to-I editing of the host and viral RNA,”

The study will define the functions and mechanisms of ADAR1-mediated antiviral innate immunity in the retina. Due to the lack of vaccines or specific antiviral therapies against ZIKV, the data obtained could allow for the design of novel therapeutics to prevent ZIKV complications in humans.

“I am very thankful to my current and past trainees and collaborators in these exciting projects. We are optimistic that the anticipated results from these studies will aid in the development of approaches to treat bacterial and viral infections affecting the vision,” Dr. Kumar said.

The grant numbers for these National Institutes of Health studies are R01EY026964 and R21AI149385.

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