| |
Coronavirus research updates: Vaccine
candidate protects monkeys from infection
|
| |
| |
NEWS
30 July 2020
Nature wades through the literature on the new coronavirus - and summarizes key papers as they appear.
https://www.nature.com/articles/d41586-020-00502-w
30 July - Vaccine candidate protects monkeys from infection
An experimental coronavirus vaccine seems to have completely prevented infection in most monkeys that received the jab.
Hanneke Schuitemaker at Janssen Vaccines and Prevention in Leiden, the Netherlands, Dan Barouch at Beth Israel Deaconess Medical Center in Boston, Massachusetts, and their colleagues gave 32 rhesus macaques (Macaca mulatta) a single dose of one of 7 vaccines (N. B. Mercado et al. Nature http://doi.org/d5d4; 2020). Each vaccine comprised a weakened respiratory virus coding for one of seven forms of SARS-CoV-2's spike protein.
After vaccination, nearly all the monkeys made neutralizing antibodies - powerful immune molecules that can block infection - and T cells that trigger other immune responses. When monkeys were exposed to SARS-CoV-2, the most potent of the vaccines prevented lung infection in six out of six animals that received it, and nasal infection in five out of six.
Across all the vaccinated monkeys, levels of neutralizing antibodies were associated with protection from SARS-CoV-2 infection, but levels of T cells were not.
29 July - Immune cells against the virus are found in unexposed people
Immune cells called T cells are prepared to attack the new coronavirus not only in people with COVID-19, but also in some who have not been exposed to the virus.
At first, researchers studying the immune response to SARS-CoV-2 focused mostly on the immune molecules called antibodies, but T cells offer another possible route to immunity. Andreas Thiel at Charité University Hospital Berlin and his colleagues surveyed blood samples for T cells that react to the SARS-CoV-2 spike protein (J. Braun et al. Nature http://doi.org/d5bv; 2020).
The team found such cells in 83% of study participants with COVID-19, as well as 35% of healthy blood donors who had not been exposed to SARS-CoV-2. The authors speculate that the reactive T cells might have been generated in healthy donors during past infections with related coronaviruses, but it remains unclear whether these cells offer protection against SARS-CoV-2.
28 July - Mutations allow virus to elude antibodies
Mutations in SARS-CoV-2 might help the virus to thwart potent immune molecules.
The blood of many people who recover from COVID-19 contains immune-system molecules called neutralizing antibodies that disable particles of the new coronavirus. Most such antibodies recognize the new coronavirus's spike protein, which the virus uses to infect cells. Researchers hope that these molecules can be used as therapies, and can be elicited by vaccines.
Theodora Hatziioannou and Paul Bieniasz at the Rockefeller University in New York City and their colleagues engineered a version of the vesicular stomatitis virus, which infects livestock, to make the spike protein. They then grew the virus in the presence of neutralizing antibodies (Y. Weisblum et al. Preprint at bioRxiv http://doi.org/d439; 2020). The spike protein in the engineered viruses acquired mutations that allowed the viruses to escape recognition by a range of neutralizing antibodies.
The team also found these mutations in SARS-CoV-2 samples from infected people around the world, although at very low frequencies. Treatment 'cocktails' of multiple neutralizing antibodies, each recognizing a different part of the spike protein, could stop the virus from evolving resistance to these molecules, the authors suggest. The findings have not yet been peer reviewed.
27 July - The power of China's virus-control campaign is seen in pattern of symptoms
In China, a key metric of epidemics called the serial interval shrank drastically soon after the new coronavirus's arrival - a finding that underscores the success of China's testing and isolation efforts.
The serial interval is the average time between the onset of symptoms in a chain of people infected by a pathogen. Benjamin Cowling at the University of Hong Kong and his colleagues modelled the spread of SARS-CoV-2 in China and found that the serial interval plummeted from 7.8 days to 2.6 days over a 5-week period starting on 9 January (S. T. Ali et al. Science http://doi.org/gg5mpc; 2020).
The researchers say that early isolation of cases prevented transmission that would otherwise have occurred later in an infectious period, leading to fewer cases and slowing the spread of the virus. As a result, most of the remaining transmissions occurred either before infected people showed symptoms or early in the symptomatic phase, and the serial interval shrank.
The authors suggest the serial interval distribution be used in real time to track the changing transmissibility of the virus.
24 July - Dogs' and cats' infection rates mirror those of people
Cats and dogs are just as likely to be infected with SARS-CoV-2 as
people are, according to a survey in northern Italy that is the largest study of pets so far.
Nicola Decaro at the University of Bari and his colleagues took nose, throat or rectal swabs of 540 dogs and 277 cats in northern Italy between March and May (E. I. Patterson et al. Preprint at bioRxiv http://doi.org/d4r7; 2020). The animals lived in homes with infected people, or in regions severely affected by COVID-19.
None of the pets tested positive for SARS-CoV-2 viral RNA, but in further tests of antibodies against the virus circulating in the blood of some animals, the researchers found that around 3% of dogs and 4% of cats showed evidence of previous infection.
Infection rates among cats and dogs were comparable with those among people in Europe at the time of testing, suggesting that it is not unusual for pets to be infected. The findings have not yet been peer reviewed.
24 July - Virus rips through Israeli school after masking is suspended
More than 150 students at an Israeli secondary school were infected by the new coronavirus after students were allowed to remove their masks during a heat-wave.
Roughly 10 days after Israeli schools fully reopened on 17 May, two students at a secondary school in Jerusalem were diagnosed with COVID-19. Chen Stein-Zamir at the Ministry of Health in Jerusalem and her colleagues investigated the resulting outbreak and found that 153 students and 25 members of staff had become infected (C. Stein-Zamir et al. Euro Surveill. http://doi.org/d4sw; 2020). By mid-June, a further 87 cases had occurred among the close contacts of people infected through the school outbreak.
The virus's spread was probably aided by a heat-wave that occurred between 19 and 21 May, prompting heavy use of air-conditioning and a suspension of the requirement that students wear face masks. Crowding might also have contributed: each of the school's classrooms held 35 to 38 students, resulting in space allotments of 1.1-1.3 square metres per student.
22 July - Severely ill people yield diverse trove of powerful antibodies
Scientists have identified a diverse group of antibodies that block the new coronavirus's ability to infect cells - even when applied in low doses.
The immune-system proteins called neutralizing antibodies interfere with hostile microbes trying to enter target cells. David Ho at Columbia University Vagelos College of Physicians and Surgeons in New York City and his colleagues studied neutralizing antibodies from the plasma of five people with severe cases of COVID-19 (L. Liu et al. Nature http://doi.org/d4md; 2020).
Nineteen antibodies proved highly effective at preventing SARS-CoV-2 infection of cell samples. A small dose of one of the antibodies protected golden Syrian hamsters (Mesocricetus auratus) from SARS-CoV-2 infection.
The 19 antibodies attach to a variety of locations on the coronavirus spike protein. A therapy made from antibodies that fasten onto the spike protein at multiple sites could be difficult for the virus to evade through mutation.
21 July - Viral levels could help to target treatment
The amount of viral RNA in the nose and throat of a person infected with the new coronavirus could help clinicians to decide how best to treat them, according to an analysis of thousands of swabs taken at a hospital in Switzerland.
Onya Opota and his colleagues at Lausanne University Hospital analysed the viral load - the amount of virus in a standard volume of material - of samples taken from 4,172 people infected with SARS-CoV-2 between 1 February and 27 April (D. Jacot et al. Preprint at medRxiv http://doi.org/d4b8; 2020). They noticed two distinct stages of COVID-19. Early in the disease, people have high viral loads, which tend to decline gradually as the disease progresses. This later stage is typically characterized by inflammation. The decline of viral loads could thus serve as a cue to start treating infected people with anti-inflammatory drugs.
But the researchers found no correlation between viral load and the severity of disease, suggesting that it is not a good predictor of a patient's outcome. The research has not yet been peer reviewed.
16 July - Antiviral antibodies peter out within weeks after infection
Key antibodies that neutralize the effects of the new coronavirus fall to low levels within months of SARS-CoV-2 infection, according to the most comprehensive study yet.
Neutralizing antibodies can block a pathogen from infecting cells. But such antibody responses against coronaviruses often wane after just a few weeks.
Katie Doores at King's College London and her colleagues monitored the concentration of neutralizing antibodies against SARS-CoV-2 in 65 infected people for up to 94 days (J. Seow et al. Preprint at medRxiv http://doi.org/d3s2; 2020). In a preprint that has not yet been peer reviewed, the team reports that at the peak of antibody production, people with severe COVID-19 symptoms had higher levels of antibodies than had people with mild disease.
However, in most people, antibody levels began to fall about a month after symptoms appeared, sometimes to nearly undetectable levels - raising questions about the durability of vaccines designed to promote the production of neutralizing antibodies.
more at link above.
|
|
| |
| |
|
|
|
