Hantaviruses came back into the news in late February when a pest control worker found actor Gene Hackman and his wife, Betsy Arakawa, dead in their home in Santa Fe, New Mexico.
Autopsies determined that Arakawa died of hantavirus pulmonary syndrome, a rare but serious illness with a death rate close to 40%. Hackman died a few days later of heart disease and Alzheimer’s disease.
Hantaviruses can cause two potentially deadly diseases: HPS and hemorrhagic fever with renal syndrome. You can get a hantavirus from the urine, saliva, or droppings of rats, mice, or other rodents.
You can also get the virus from rodent bites and scratches. Most cases in the U.S. occur in the Western U.S. states, but there are different hantaviruses across North and South America, as well as in Europe, Asia, and anywhere else there are rodents.
The ELISA antibodies test can spot hantavirus, but doctors do not commonly use it. Rather, if your doctor suspects you have hantavirus, they may refer you to your state laboratory or the CDC for testing.
But researchers are developing both new tests and treatments for the hantavirus.
How Do You Know If You Have Hantavirus?
A recent study shows that lateral flow tests, similar to the ones that detect COVID-19, can be highly effective at detecting hantavirus antibodies. This could one day lead to cheaper and more widespread testing.
WebMD spoke with Robert H. Carnahan, PhD, professor and associate director of Vanderbilt University’s Crowe Lab, who is one of the leaders of the Vanderbilt antibody “sprint” to see how quickly they can develop monoclonal antibodies against emerging infections and other biological threats to prevent the next pandemic.
Doctors already use monoclonal antibodies to treat cancer, lupus, and other diseases. Soon they could treat hantaviruses, too.
What are monoclonal antibodies? Our white blood cells make antibodies to fight disease. By cloning white blood cells from specific people or animals, scientists can tailor antibodies to fight a specific illness.
In 2021, scientists used antibodies from survivors of a hantavirus called “sin nombre” to make a new antibody that kills several different hantaviruses. More recently, researchers at Vanderbilt University discovered a two-antibody combination that kills both New World hantaviruses from the Americas and Old World hantaviruses from Europe and Asia.
We asked Carnahan about the state of hantavirus treatment.
The following interview has been edited for style and clarity.
Where is the hantavirus antibody sprint now in terms of development?
Robert H. Carnahan, PhD: We have discovered a two-antibody combination that broadly neutralizes hantaviruses across Old World (example hantaan virus) and “New World” (example sin nombre virus) species.
We have initial in vivo efficacy data in a widely accepted hamster model. We are carrying out some follow-on [tests] in vivo experiments to establish optimal dosing.
How soon do you think authorities will be able to deploy a rapid response to a hantavirus outbreak?
Carnahan: This is complex. It will involve either the U.S. government or a company taking our discovery and moving it through manufacturing and clinical trials. If desired, this could be done through a phase I safety trial in a year or less.
From there, it could likely be authorized to be deployed in an outbreak as part of a compassionate use or a field clinical trial. Doing a standard phase II or III clinical trial will be difficult due to the rarity of severe disease.
Monoclonal antibodies can be used to treat or prevent conditions. Do you think monoclonal antibodies could one day be used as the basis of a hantavirus vaccine?
Carnahan: One of the strengths of antibodies is they can be used for both treatment and prevention (prophylaxis). A typical antibody has a serum half-life of 30 days. But if one sets the dosing above the protective threshold, this can mean several months of protection.
However, scientists have discovered how to make modifications to antibody-based drugs to increase the half-life by threefold or more. If one has a potent high-functioning antibody, this can mean a year or more of protection against infection.
Our antibody to COVID (Evusheld – AstraZeneca) was one such modified antibody. It was shown to provide substantial protection beyond one year. So in this sense, antibodies may be used as a vaccine-like strategy.
Compared to different treatments in development for hantavirus, where does monoclonal antibody treatment stand in terms of effectiveness? Is it too early to tell?
Carnahan: Drug treatments (small molecules) for viral disease do not have a strong track record. This is partially due to the fact they are rapidly cleared from the body. So they really only make sense as a treatment, not a prevention.
Many also seem to have a narrow window after infection when they can provide benefit. For example, Tamiflu can shorten the course of a flu infection, but only if taken very early after symptom onset. All that to say, these drugs have a narrow window of use.
True vaccines, not antibodies, can provide relatively low-cost long-term protection (up to lifelong protection). The limitation here is that they are only effective before infection. Once infected, they will provide little benefit. However, they tend to be much cheaper to make and therefore are lower cost to patients.
In the long term, we foresee antibody costs declining as new manufacturing approaches solve costly production issues. I think there is a day where one will receive a mix of vaccines and antibodies based on the needs of the individual.
Hantavirus is fairly rare, but three people recently died from HPS in California, and six new species of hantavirus-carrying rodents have been identified. Do you think any of the current hantaviruses has the potential to become a pandemic, or at least a larger-scale problem than it already is?
Carnahan: As far as we know, person-to-person spread is not common. As long as that continues to be the case, it seems unlikely to become a full-blown pandemic.
However, we could continue to see increases in outbreaks. These increasing outbreaks will lead to higher morbidity and mortality. So there is a strong chance that we will need to find ready-for-use solutions for these outbreaks. Antibodies make an ideal response for this type of issues, as they can be used to “ring vaccinate” within an outbreak. This is where all those in the infected area are prophylactically treated with antibodies to protect from infection and/or spread.
