Podcast Summary

Podcast: Becker’s Healthcare Podcast
Episode: Uncovering a Viral Link to Parkinson’s Disease with Dr. Barbara Hanson and Dr. Igor Koralnik
Release Date: August 18, 2025
Host: Laura Dardo (A)
Guests:

• Dr. Barbara Hanson, Postdoctoral Researcher, Department of Neurology, Northwestern Medicine
• Dr. Igor Koralnik, Archibald Church Professor of Neurology & Chief of Neuroinfectious Disease and Global Neurology, Northwestern Medicine

Episode Overview

This episode delves into groundbreaking research from Northwestern Medicine that investigates the possible viral triggers of Parkinson’s disease (PD), specifically the discovery of a strong association between human pegivirus and PD pathology. Dr. Barbara Hanson and Dr. Igor Koralnik share their recent findings connecting certain viruses to the brains of people with Parkinson’s, discuss how genetic factors might interact with viral presence, and highlight the broader implications for diagnosis, treatment, and future research around Parkinson’s disease.

Key Discussion Points & Insights

1. Research Focus and Motivation

• Dr. Koralnik’s lab seeks to understand how viruses affect the nervous system, with a focus on whether viruses may contribute to neurodegenerative diseases like Parkinson’s.
  • “You know that Parkinson's disease is this deteriorative disease of the nervous system affecting more than a million people in the United States...the cause of the disease is unknown for the majority of cases.” (C, 00:50)
• Environmental factors—including viruses—have long been hypothesized as potential triggers for Parkinson’s, given that genetics account for only a minority of cases.

2. Comprehensive Virome Analysis

• The team developed an unbiased assay called “varofind” to search for all known human viruses in postmortem brain samples of PD patients and matched controls.
• Significant finding: While various viruses were found in both groups, human pegivirus was detected exclusively in the brains of PD patients.
  • “There was one species of viruses that existed only in the brain of Parkinson's patient. This is called the human Pegivirus...” (C, 01:49)
• Human pegivirus is generally thought to be harmless and not found in the brain, making its presence in PD brains particularly startling.

3. Findings and Significance

• Out of 10 PD donors, 5 had human pegivirus in their brain tissue. By contrast, none of the age and sex-matched controls tested positive.
  • “We identified in 5 out of 10 of the PD donors the presence of human pegivirus... we did not find it in any of the control donors in this population.” (B, 02:53)
• Historically, human pegivirus has not been linked to any clinical symptoms or to being part of the healthy brain virome.
• Association with Parkinson’s was stronger than with other neurodegenerative conditions (ALS, MSA, AD, HIV, etc.) previously studied by the group.

4. Implications for Pathology and Detection

• In addition to brain tissue, human pegivirus was found in the cerebrospinal fluid (CSF) of about 30% of PD cases, suggesting potential for in vivo detection.
  • “...not only the virus was present in the brain...but also in 30% of them, we found the virus in their cerebrospinal fluid.” (C, 04:29)
• Presence of the virus correlated with differences in pathology—though clarification was made that increased pathology observed was for Alzheimer’s (AD) markers, not Parkinson’s, due to the recruitment through an AD cohort.
  • [Clarification] “These individuals were actually recruited through an AD cohort and the only measures that we have are actually measures of AD pathology.” (B, 06:42)

5. Interaction Between Virus and Genetics

• Analysis using blood samples and datasets from the Parkinson’s Progression Marker Initiative (PPMI) showed that immune responses to pegivirus varied depending on whether PD patients carried the LRRK2 mutation (a known genetic risk factor).
  • “We saw a dichotomy between individuals who have PD and carry a LRRK2 mutation and those who have PD but don’t carry that LRRK2 mutation.” (B, 09:10)
• Differences centered around an immune signaling molecule, IL4, which may play an unexpected role in modulating disease progression.

6. Potential for Therapeutic Repurposing

• Human pegivirus is closely related to Hepatitis C virus (HCV), for which effective medications already exist.
• If findings are validated, HCV therapies could potentially be repurposed to target human pegivirus in PD patients.
  • “It would be possible to think that those medications that could affect the hepatitis C virus in the liver could be also repurposed to...target the human [pegivirus] in the brain.” (C, 05:35)

7. Next Steps and Broader Research Directions

• Ongoing work includes:
  • Expanding the study to new brain samples from Australia and other sources to validate findings outside the US.
  • Investigating localization of the virus to specific brain cell types, such as oligodendrocytes, via neuropathological methods.
  • Testing in silico how anti-HCV drugs might bind or inhibit human pegivirus.
  • Seeking collaborations with researchers and pharmaceutical companies.
  • “...the more the merrier. Obviously, this is a new field of investigation and I think that we need to attract more people to this field, including pharmaceutical companies...” (C, 12:52)

Notable Quotes & Memorable Moments

• On the nature of the discovery:

  • “This is really not something that we particularly expect to be associated with any pathology...” (B, 03:08)

• Potential for treatment:

  • “There are treatments but no cure. What we find is also interesting is that this human pegivirus is a close relative from another virus called Hepatitis C virus...If the finding...is confirmed and expanded...then it would be possible to think that those medications...could be also repurposed...” (C, 05:15)

• On the interplay of genes and environment:

  • “You’ve got this interaction between the environment and the genetic background where some individuals may be infected...and maybe developing very, very different responses to it that could have some interactions with that, the development of Parkinson’s disease...” (B, 10:38)

• Call for collaboration:

  • “First, I'm happy if people are interested in our study and want to collaborate with us. Maybe they have unique samples...the more the merrier...I think that we need to attract more people to this field...” (C, 12:52)

Important Timestamps for Key Segments

• [00:50] – Dr. Koralnik introduces the study’s motivation and background
• [01:49] – Discovery of human pegivirus association with PD brains
• [02:53] – Dr. Hanson details specific findings from brain tissue samples
• [04:29] – Detection of the virus in cerebrospinal fluid; potential clinical implications
• [05:35] – Discussion of antiviral therapy repurposing prospects
• [06:42] – Clarification on observed pathology measures (AD vs PD)
• [08:21] – Interaction with genetic mutations (LRRK2) and immune signaling (IL4)
• [12:52] – Appeal for collaboration and description of ongoing/next studies

Conclusion & Future Directions

The research by Dr. Hanson and Dr. Koralnik represents a major step toward understanding how environmental factors—specifically viral infections—may interplay with genetics to influence Parkinson’s disease development and progression. Their discovery of human pegivirus in the brains of PD patients challenges assumptions about the role of “harmless” viruses and opens opportunities both for new diagnostic methods and for exploring the repurposing of existing antiviral therapies. The team’s openness to collaboration and commitment to expanding the scientific inquiry set an exciting direction for future neurodegenerative disease research.