H5N1, the avian flu virus, has spread extensively among animal populations since 2022, but no human-to-human transmission has been reported yet.
Many people already possess immune cells prepared to combat the H5N1 virus, commonly referred to as highly pathogenic avian influenza.
The H5N1 “bird flu” virus first appeared in 2022 and has since spread extensively throughout animal populations, including cattle and poultry. U.S. poultry and dairy workers who contracted H5N1 through animal contact have reported 66 confirmed cases of the virus according to the U.S. Centers for Disease Control and Prevention. To date, no human-to-human transmission cases have been reported.
The new virus is being closely monitored by scientists and vaccine specialists, who have matched the genetic sequences of H5N1 with those of seasonal influenza viruses that are currently circulating in people.
Since H5N1 and these common viruses have many similarities, the LJI team was able to predict that many people already have “cross-reactive” T cells that are prepared to target H5N1 should it ever change to cause widespread sickness in humans.
“This leads us to believe that a certain number of cross-reactive T cell responses might already be present and could help reduce the severity of the disease,” says Sette, who is also the Co-Director of the LJI Center for Vaccine Innovation.
How T Cells Could Help Combat H5N1
Most Americans have had the flu or received a flu shot in the past. That means their immune systems have built up some level of immunity against common influenza viruses.
Sette and Grifoni investigated how well these influenza-fighting T cells might recognize and target the new H5N1 virus. The scientists used data from the LJI-led Immune Epitope Database (IEDB) to identify exactly how human T cells attack key proteins, or epitopes, on seasonal flu viruses. They then developed a computational approach to figure out if the
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The researchers found that many epitopes are shared, or “conserved” between H5N1 and seasonal influenza viruses. This means many people may already have T cells equipped to battle H5N1 infections.
“We can predict that—in the majority of cases—our T cells have memory responses and can provide pre-existing immunity to H5N1,” says Grifoni. “That’s good news.”
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Cross-Reactive T Cells: Potential Key to Reducing H5N1 Severity
The researchers cannot say for sure whether these T cell responses can lessen disease severity; however, there is reason to believe cross-reactive T cells may be good fighters. In previous studies, LJI scientists have shown that cross-reactive T cells can lessen the severity of COVID-19 and even mpox.
Going forward, the researchers are interested in studying the strength of these T-cell responses. They are also prepared to analyze immune cells from human samples, should H5N1 begin spreading between people.
“We need to continue to monitor the situation, and if an outbreak were to occur, we’re ready to examine immune responses in more detail,” says Sette.
According to the CDC, there have been avian influenza A viruses—other than H5N1—which have spread between humans in the past, but that is very rare.
Reference:
- Targets of influenza human T-cell response are mostly conserved in H5N1- (https:journals.asm.org/doi/10.1128/mbio.03479-24)
Source-Eurekalert
