The hunt for an effective treatment for COVID-19 has led to an unlikely ally – a llama and her antibodies.
Researchers at the University of Texas-Austin linked two copies of an antibody produced by llamas to create a new antibody that binds to a protein on the coronavirus that causes COVID-19. The protein – called the spike protein – allows the virus to break into host cells. Initial tests indicate the antibody blocks viruses that display the spike protein from infecting cells in culture. It is one of the first antibodies known to neutralize SARS-CoV-2.
Our team is preparing to conduct pre-clinical studies in animals such as hamsters and primates, with hopes to eventually conduct testing in humans. The goal is to develop a treatment that would help people soon after being infected with the virus.
Vaccines must be given a month or two before infection to provide protection. With antibody therapies you’re directly giving someone the protective antibodies. So immediately after treatment the person should be protected. The antibodies also could be used to lessen the severity of the disease for someone who already is sick.
When llamas’ immune systems detect foreign invaders such as bacteria and viruses, the animals – and other camelids such as alpacas – produce two types of antibodies. One is similar to human antibodies. The other is only about a quarter of the size. The smaller ones – called single-domain antibodies or nanobodies – can be nebulized and used in an inhaler.
Enter "Winter" the llama. The 4-year-old is living on a farm in Belgium along with about 130 other llamas and alpacas. Her part in the experiment happened in 2016 when she was about 9 months old. Two earlier studies involved coronaviruses SARS-CoV-1 and MERS-CoV. Winter was injected with stabilized spike proteins from the viruses in the course of about six weeks.
A blood sample and isolated antibodies that bound to each version of the spike protein were collected. One showed promise in stopping a virus – that displays spike proteins from SARS-CoV-1 – from infecting cells in culture.
The research team engineered the new antibody that shows promise for treating the current SARS-CoV-2. We linked two copies of the llama antibody that worked against the earlier SARS virus. We demonstrated that the new antibody neutralizes viruses displaying spike proteins from SARS-CoV-2 in cell cultures.
Inspired by a special kind of antibody produced by llamas we created an antibody called VHH-72Fc – see blue in the accompanying image. It binds to the spike protein on SARS-CoV-2 – shown in pink, green and orange. And it blocks the virus from infecting cells in culture. The spike protein structure was discovered by part of the same research team and was published in the Feb. 19 edition of “Science.” The study recently was pre-published in “Cell.” Visit cell.com/pb-assets/products/coronavirus/CELL_CELL-D-20-00891.pdf for more information.