- A new study indicates that chronic viral infections can have lasting effects on the immune system, similar to aging.
- Chronic inflammation contributes to illness and death as we age, but it’s not known whether chronic infections might affect us in a similar way.
- Eliminating the virus from the body can restore some functions of the immune system.
- It’s unclear what the implications are for people with long-haul COVID-19, but it could affect their ability to respond to other viral conditions.
According to a new study published in Proceedings of the National Academy of Sciences, chronic viral infections can have lasting effects on the immune system.
The study authors say these effects are similar in nature to those caused by aging.
Chronic inflammation contributes to illness and death as we age, the authors explain.
However, it’s not clear whether similar mechanisms are at play in the immune system dysfunction associated with chronic infections.
Systemic inflammation may occur in response to chronic viral infections or aging, the study authors explain in their write-up.
In addition, systemic inflammation has been associated with immune dysregulation and the development of certain chronic illnesses.
To examine any similarities or differences between these states, David Furman, PhD, Buck Institute for Research on Aging associate professor and senior author of the paper, said he and his team used an “unbiased approach.”
This was achieved by doing deep immune monitoring of human blood in three cohorts: aging, HIV, and hepatitis C virus (HCV).
In their study, they looked at the effects of chronic infections and aging in various components of the immune system.
The researchers found many things in common between the immune dysregulation associated with aging and chronic infections, including changes “from naïve to memory T cells, elevated baseline inflammatory signaling, and a diminished sensitivity to cytokine stimulation in lymphocytes and myeloid cells.”
In other words, the study suggests that these chronic viral infections can diminish the immune system’s effectiveness in ways similar to aging.
They also found that these effects can last for a year or more after the viral load has been reduced or eliminated.
However, removing the virus from the body can restore some functions of the immune system.
According to Nick Pullen, PhD, associate professor of biological sciences at the University of Northern Colorado in Greeley, who was not involved with the study, there are two big things that we can glean from this research.
First, that the chronic viruses studied have significant impact by suppressing the immune system.
“This is expected (particularly for HIV), but some of the news here is that the mechanism affected might actually prevent you from responding effectively to any viruses innately through a signaling system that starts with the protein interferon-alpha,” Pullen said.
Interferon-alpha is a cytokine the immune system produces as a response to fight viral infections.
“The other big take away is that this might be reversible if you can totally eliminate the chronic virus,” Pullen said.
“Elimination of HCV restored some innate antiviral function, whereas maintenance suppressive drugs for inhibiting HIV (in other words treating but not completely eliminating chronic virus) were not enough to mitigate the virus’s impact on this aspect of immunity,” he said.
According to Furman, this is “good news because it shows there’s room for interventions.”
As for the coronavirus that causes COVID-19, Furman said it’s still too early to say what the implications might be.
However, “the model is that each immune reaction, the accumulation of viral exposures, determines to a large extent the health of the immune system,” he said.
“Especially those eliciting immune memory where we predict there is ample modification in the epigenetic landscape with major consequences in subsequent immune cell responses to new pathogenic challenges,” Furman said.
“Has the immune system of those infected with the coronavirus taken a big hit? That’s a theory, but we don’t know what will happen,” he said.
Pullen added that while it’s unclear how COVID-19 “long-haulers” will be affected, the concept of “off-target” responses is generating some interest.
“For example, could immune reaction due to COVID affect one’s ability to respond to other threats?” Pullen said.
“In this study, suppression of interferon-alpha by chronic infection implies that there will be problems responding to just about any other virus at first,” he said.