[ti:Studies Suggest T Cells Important in Fighting Coronavirus] [by:www.51voa.com] [00:00.00]更多听力请访问51VOA.COM [00:00.04]What gives some people immunity from the novel coronavirus, [00:06.00]the virus that causes COVID-19? [00:11.12]Some scientists are studying whether it is the presence of antibodies. [00:18.40]Others are studying a part of the human immune system, [00:22.68]known as T cells, which can protect people from viruses. [00:30.00]Recent studies show that some recovered patients who tested negative [00:36.08]for coronavirus antibodies developed T cells in their immune systems. [00:44.32]The reaction is believed to be the result of their COVID-19 infection. [00:51.08]The studies are small and have yet to be confirmed by outside experts. [00:57.80]However, some scientists now say that people who show few signs of sickness [01:05.04]from the new coronavirus, or show no signs at all, [01:10.16]may be actually killing off the infection with their T cells. [01:17.16]The findings add to the evidence that an effective COVID-19 vaccine [01:23.68]will need to push T cells to work in addition to producing antibodies. [01:30.72]This may also affect several treatments that are being developed. [01:36.04]The recent findings may explain how immunity to the virus might work. [01:43.88]Dr. Alessandro Sette is studying the reaction to the coronavirus [01:50.44]at the La Jolla Institute's Infectious Disease and Vaccine Center in California. [01:58.52]He said there is growing evidence that "people exposed to the virus [02:03.68]have a transient (short-lived) antibody response," [02:07.16]or they have a T cell response without creating antibodies. [02:13.44]When a virus gets past the body's infection-fighting white blood cells, [02:19.24]another defense reaction starts. [02:22.28]It causes the production of cells that attack the invading virus. [02:29.24]The defense includes antibodies that can identify the virus [02:34.44]and lock onto it, preventing its entry into a person's cells. [02:42.20]The body's defense also can include T cells [02:46.88]that can kill both invaders and the cells they have infected. [02:54.04]The world is now six months into the COVID-19 outbreak. [02:59.12]The coronavirus has infected more than 12 million people. [03:04.36]But scientists are not sure whether the antibody reaction to the virus infection [03:12.00]is strong or lasts over time. [03:17.08]Some scientists think this could mean T cells [03:20.88]have an important job protecting humans against illness. [03:27.44]"T cells are often important in controlling viral infections. [03:32.72]We are seeing evidence of that," John Wherry told Reuters. [03:39.08]He is a director of the University of Pennsylvania's Institute for Immunology. [03:46.64]Reuters reports that a recent, small French study [03:50.84]that has not yet been confirmed by experts, [03:54.52]examined immunity in family members. [03:58.84]It found that six out of eight family members in close contact with relatives [04:05.56]who had COVID-19 developed a T cell response. [04:11.16]Importantly, tests did not show that they had coronavirus antibodies. [04:18.64]A Swedish study of about 200 people had similar results. [04:25.44]It found a strong T cell response in most individuals [04:31.08]who had few or no signs of sickness following coronavirus infection. [04:38.80]The T cells were present whether or not any antibody response was found. [04:47.40]Examining T cell responses could also help explain longer-term immunity. [04:55.84]There is some evidence that T cells developed after exposure [05:00.80]to other coronaviruses which cause the common cold [05:05.28]could help fight off the new virus. [05:08.52]The new virus is also known as SARS-CoV-2. [05:14.40]A study by the La Jolla Institute found T cells that reacted to SARS-CoV-2 [05:22.00]in about half of stored blood samples collected between 2015 and 2018. [05:29.88]That might mean that earlier infections with the common cold coronaviruses [05:36.08]might help protect against the new virus. [05:40.76]"It is a potentially encouraging piece of evidence," Wherry said. [05:47.72]The current vaccine candidates against COVID-19 [05:52.20]aim to create antibody and T cell responses. [05:57.24]The recent findings suggest the importance of the T cell response [06:02.64]in human medical tests. [06:06.56]"We believe that the optimal vaccine design [06:10.52]would be one with both an antibody and T cell response," Sette said. [06:18.28]After an infection or vaccination, the immune system [06:23.28]keeps a number of "memory" cells that are ready to quickly attack [06:28.40]the same virus in case of a future infection. [06:33.84]Many countries are using blood tests that look for antibodies [06:38.72]to estimate how many people have been infected. [06:43.88]But measuring "memory" T cells is much more difficult. [06:48.84]It also remains unclear what combination of immune system cells [06:55.40]will result in the best protection from the virus. [07:00.68]"It is a lot easier to collect antibody data," said Daniela Weiskopf. [07:07.72]She is an assistant professor at the La Jolla Institute. [07:13.52]I'm Susan Shand. 更多听力请访问51VOA.COM