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Study identifies four new monoclonal antibodies with broad neutralizing potencies that target conserved SARS-CoV-2 epitopes

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In a recent study posted to the bioRxiv* preprint server, researchers described four novel monoclonal antibodies with potent and broad neutralization activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants, including the current globally dominant Omicron BA.4/BA.5.

Study: Identification of broad, potent antibodies to functionally constrained regions of SARS-CoV-2 spike following a breakthrough infection. Image Credit: Corona Borealis Studio/Shutterstock

Background

Although the early impetus to develop coronavirus disease 2019 (COVID-19) vaccines and the use of monoclonal antibody therapies successfully limited the severity of SARS-CoV-2 infections, the emergence of Omicron subvariants with mutations in the spike protein receptor binding domain (RBD) is challenging the vaccine-induced immunity.

Since early vaccines and monoclonal antibodies targeted the receptor binding motif that binds to the angiotensin-converting enzyme-2 (ACE-2) receptor, these novel mutations allow the emergent Omicron subvariants to escape the neutralizing antibodies generated against the RBD of earlier variants, reducing the efficacy of the therapeutic monoclonal antibodies in clinical use.

Combining monoclonal antibodies that target a wide variety of epitopes, including conserved regions inside and outside the RBD, might not only broaden the therapeutic antibodies’ neutralizing activity but also help reduce the selection pressure driving the development of new variants of concern.

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About the study

In the present study, the researchers isolated monoclonal antibodies specific for SARS-CoV-2 spike proteins from a patient who experienced a Delta variant breakthrough infection two months after completing the primary vaccination regimen with the Pfizer-BioNTech messenger ribonucleic acid (mRNA) vaccine. Peripheral blood mononuclear cells (PBMCs) were collected after 30 days of the onset of symptoms to isolate memory B cells using spike-subunit 2 or Delta spike protein peptide baits. Variable regions of the heavy and light chain immunoglobulin genes were recovered and cloned into immunoglobulin G (IgG) kappa, lambda, or gamma constructs to produce monoclonal antibodies.

Enzyme-linked immunosorbent assays (ELISA) were used to screen these monoclonal antibodies using a panel of SARS-CoV-2 spike glycoproteins from multiple variants. Biolayer interferometry (BLI) was performed to assess the binding affinity of the identified monoclonal antibodies to spike proteins from Omicron subvariants BA.1, BA.2, and BA.4/BA.5, as well as from the ancestral Wuhan-Hu-1 and SARS-CoV-1 spike glycoproteins.

Neutralization assays using spike-pseudotyped lentivirus and live SARS-CoV-2 were conducted to test the neutralizing potency of the monoclonal antibodies. The neutralizing activity of the selected monoclonal antibodies was also compared to that of monoclonal antibodies authorized for treating SARS-CoV-2 infections. The neutralization assay with pseudotyped lentivirus also assessed the neutralizing capacity of the plasma samples collected from the participant.

The live virus neutralization assay tested the efficacy of the monoclonal antibodies against a wide range of variants, including the ancestral Wuhan-Hu-1 strain and the Alpha and Delta variants. The Omicron subvariants BA.1, BA.2, and BA.2.12.1.

Additionally, various recombinant spike subdomain peptides were used to identify the spike glycoprotein regions to which the monoclonal antibodies were binding. Commercial monoclonal antibodies belonging to RBD classes based on the structural analysis of contact residues and epitope accessibility and deep mutational scanning were employed for competition ELISA to refine the epitopes of the selected monoclonal antibodies.

Fluorescence-activated cell sorting-based assay and yeast display libraries of mutated RBDs were used to determine the effect of a single amino acid substitution mutation on the binding of the monoclonal antibody to the epitope. Structural methods such as cryogenic electron microscopy (cryo-EM) structure determination and hydrogen-deuterium exchange mass spectrometry were also conducted to examine the epitopes targeted by selected monoclonal antibodies.

Results

The results described four monoclonal antibodies isolated from a patient with a heterologous antigen exposure to the spike proteins from the ancestral Wuhan-Hu-1 strain through vaccination and the Delta variant spike protein from breakthrough infections. In the neutralization assays using pseudotyped lentiviruses and live SARS-CoV-2 viruses, these four antibodies displayed neutralizing activity against the currently dominant Omicron subvariants BA.4/BA.5 while retaining potent neutralizing capacity against the Wuhan-Hu-1 strain and the Delta variant. One of the monoclonal antibodies was also able to neutralize SARS-CoV-1.

Compared to the monoclonal antibodies currently in clinical use, the potency of the newly isolated monoclonal antibodies against the Omicron subvariants was higher than all the currently approved therapeutic monoclonal antibodies except one. The epitopes targeted by these monoclonal antibodies included one in subdomain 1 in an invariant region outside the RBD and three in the RBD. The deep mutational scanning analysis to identify escape pathways from single amino acid substitutions showed that these monoclonal antibodies targeted conserved and constrained regions of the spike glycoprotein. These findings suggested that viruses could evolve to escape these monoclonal antibodies only at a fitness cost.

Conclusions

To summarize, the study identified four novel monoclonal antibodies that exhibited broad neutralization of a range of SARS-CoV-2 variants, including the Omicron subvariants BA.4/BA.5 and the ancestral Wuhan-Hu-1 strain and the Delta variant. These monoclonal antibodies target three epitopes in the RBD and one in subdomain 1 outside the RBD. Since these epitopes are highly conserved, the evolution of the virus to escape neutralization by these monoclonal antibodies could be detrimental to its fitness.

*Important notice

bioRxiv publishes preliminary scientific reports that are not peer-reviewed and, therefore, should not be regarded as conclusive, guide clinical practice/health-related behavior, or treated as established information.

Journal reference:
  • Jamie Guenthoer, Michelle Lilly, Tyler N Starr, Bernadeta Dadonaite, Klaus N Lovendahl, Jacob T Croft, Caitlin I Stoddard, Vrasha Chohan, Shilei Ding, Felicitas Ruiz, Mackenzie S Kopp, Andrés Finzi, Jesse D Bloom, Helen Y Chu, Kelly K Lee, and Julie Overbaugh. (2022). Identification of broad, potent antibodies to functionally constrained regions of SARS-CoV-2 spike following a breakthrough infection. bioRxiv. doi: https://doi.org/10.1101/2022.12.15.520606 https://www.biorxiv.org/content/10.1101/2022.12.15.520606v1

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Avian influenza spread: WHO gives public health warning as FDA calms food safety concerns – Food Ingredients First

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23 April 2024 — The World Health Organization (WHO) has warned that the ongoing spread of avian influenza poses a “significant public health concern” and urged health authorities, especially in the US, to closely monitor infections in cows. However, the US FDA maintains that the virus is not currently a concern to consumer health and downplayed its impact on commercial milk production.

Earlier this month, the largest producer of fresh eggs in the US halted production at a Texas plant after bird flu was detected in its chickens. Cal-Maine Foods said that about 3.6% of its total flock was destroyed after the infection.

However, the virus, also known as H5N1, has now been found in at least 26 dairy herds across eight US states, marking the first time this strain of bird flu has been detected in cattle, according to officials.

At least 21 states have restricted cattle importations from states where the virus is known to have infected dairy cows.

The US Department of Agriculture’s Animal and Plant Health Inspection Service strongly recommends minimizing the movement of cattle, but has not issued federal quarantine orders.

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Public health threat
The US Centers for Disease Control and Prevention (CDC) confirmed this month that a dairy worker in Texas, who reportedly had exposure to dairy cattle presumed to have had avian influenza, contracted the virus and is now recovering.

“This infection does not change the H5N1 bird flu human health risk assessment for the US general public, which CDC considers to be low,” the agency said in a press release, while acknowledging that people who come into more frequent contact with possibly infected birds or other mammals have a higher risk.

Meanwhile, WHO’s chief scientist, Dr. Jeremy Farrar, told reporters recently in Geneva, Switzerland, that H5N1 has had an “extremely high” mortality rate among the several hundred people known to have been infected with it to date.

Mother and child drinking milk.US health officials have downplayed the impact of bird flu on food safety and industry production.However, no human-to-human H5N1 transmission has yet been recorded.

“H5N1 is an influenza infection, predominantly started in poultry and ducks and has spread effectively over the course of the last one or two years to become a global zoonotic — animal — pandemic,” said Farrar.

“The great concern, of course, is that in doing so and infecting ducks and chickens — but now increasingly mammals — the virus now evolves and develops the ability to infect humans.

“And then critically, the ability to go from human-to-human transmission.”

Concerns with cattle
US health officials have stressed that bird flu’s risk to the public is low, and the country’s food supply remains safe and stable.

“At this time, there continues to be no concern that this circumstance poses a risk to consumer health or that it affects the safety of the interstate commercial milk supply,” the FDA said in a statement.

According to officials, farmers are being urged to test cows that show symptoms of infection and separate them from the herd, where they usually recover within two weeks.

US producers are not permitted to sell milk from sick cows, while milk sold across state lines must be pasteurized or heat-treated to kill viruses, including influenza.Silhouette of farmer tending to cow.A dairy worker in Texas reportedly contracted the virus after exposure to cattle.

“We firmly believe that pasteurization provides a safe milk supply,” Tracey Forfa, director of the FDA’s Center for Veterinary Medicine, told a webinar audience last week.

However, WHO’s Farrar has urged further caution by public health authorities “because it [the virus] may evolve into transmitting in different ways.”

“Do the milking structures of cows create aerosols? Is it the environment which they’re living in? Is it the transport system that is spreading this around the country?” he said.

“This is a huge concern, and I think we have to…make sure that if H5N1 did come across to humans with human-to-human transmission that we were in a position to immediately respond with access equitably to vaccines, therapeutics and diagnostics.”

According to a new European Food Safety Authority report, outbreaks of avian influenza continue to spread in the EU and beyond.

By Joshua Poole

To contact our editorial team please email us at
editorial@cnsmedia.com

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York Region urges you to get up to date on vaccinations – NewmarketToday.ca

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York Region Public Health is reminding residents to keep up to date on their vaccinations as National Immunization Awareness Week begins.

The regional municipality said it is important to stay up to date on recommended vaccinations to ensure protection from contagious diseases. That includes updated COVID-19 vaccinations for vulnerable populations, recommended as part of a spring vaccination campaign.

“We know vaccines are safe and the best way to stay protected against vaccine-preventable disease,” the region said in a news release. 

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National Immunization Awareness Week runs from April 22 to 30, with this year’s theme being “Protect your future, get immunized.” 

This spring, the region is still doing COVID-19 vaccinations. While walk-ins are no longer available as of April 2, you can book an appointment to visit a York Region clinic.

The spring COVID-19 vaccination campaign is aimed at more vulnerable groups who have received a COVID-19 vaccine before. Those include seniors, those living in seniors living facilities like long-term care homes, immunocompromised individuals and those in Indigenous households who are 55 or older. Public health also recommends the COVID-19 vaccine for those who have not yet received one.

York Region Public Health is also reminding residents of the need for other vaccines. 

Measles cases have sprung up in Ontario and York Region recently. The region is recommending that people ensure they previously raised two valid doses of the measles vaccine. The region will also start providing measles vaccines April 29 for those overdue and for who do not have access to the vaccine through a health-care provider.

School-aged vaccinations are also available for free for children in junior kindergarten to Grade 12.

You can access immunization information at york.ca/immunziations or by contacting Access York at 1-877-464-9675.

“Vaccination helps protect everyone in our families, communities and schools,” the region said. “ By continuing to stay up to date on your immunizations, you help protect infants who are too young to be vaccinated and those not able to get vaccinated due to medical conditions.”

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Bird flu raises concern of WHO – ecns

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The World Health Organization (WHO) said the rising number of bird flu cases has raised “great concern” because it had an “extremely high” mortality rate among those who had been infected around the world.

The WHO’s data show that from 2003 through March 2024, a total of 889 worldwide human cases of H5N1 infection had been recorded in 23 countries, resulting in 463 deaths and a 52 percent mortality rate. The majority of deaths occurred in Southeast Asian countries and Egypt.

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The most recent death was in Vietnam in late March, when a 21-year-old male without underlying conditions died of the infection after bird hunting. So far, cases in Europe and the United States have been mild.

Jeremy Farrar, chief scientist at the WHO, said recently that H5N1, predominantly started in poultry and ducks, “has spread effectively over the course of the last one or two years to become a global zoonotic — animal — pandemic”.

He said that the great concern is that the virus is increasingly infecting mammals and then develops the ability to infect humans. It would become critical if the virus develops the ability to “go from human-to-human transmission”, Farrar said.

In the past month, health officials have detected H5N1 in cows and goats from 29 dairy herds across eight states in the US, saying it is an alarming development because those livestock weren’t considered susceptible to H5N1.

The development worries health experts and officials because humans regularly come into contact with livestock on farms. In the US, there are only two recorded cases of human infection — one in 2022 and one in April this year in Texas. Both infected individuals worked in close proximity to livestock, but their symptoms were mild.

Wenqing Zhang, head of the WHO’s global influenza program, told the Daily Mail that “bird-to-cow, cow-to-cow and cow-to-bird transmission have also been registered during these current outbreaks, which suggest that the virus may have found other routes of transition than we previously understood”.

Zhang said that multiple herds of cow infections in the US states meant “a further step of the virus spillover to mammals”.

The virus has been found in raw milk, but the Texas Health Services department has said the cattle infections don’t present a concern for the commercial milk supply, as dairies are required to destroy milk from sick cows. In addition, pasteurization also kills the virus.

Darin Detwiler, a former food safety adviser to the Food and Drug Administration and the US Agriculture Department, said that Americans should avoid rare meat and runny eggs while the outbreak in cattle is going on to avoid the possibility of infection from those foods.

Nevertheless, both the WHO and the Centers for Disease Control and Prevention (CDC) said that the risk the virus poses to the public is still low. Currently no human-to-human infection has been detected.

On the potential HN51 public health risk, Farrar cautioned that vaccine development was not “where we need to be”.

According to a report by Barron’s, under the current plan by the US Health and Human Services Department, if there is an H5N1 pandemic, the government would be able to supply a few hundred thousand doses within weeks, then 135 million within about four months.

People would need two doses of the shot to be fully protected. That means the US government would be able to inoculate about 68 million people — 20 percent — of 330 million in case of an outbreak.

The situation is being closely watched by scientists and health officials. Some experts said that a high mortality rate might not necessarily hold true in the event the virus became contagious among people.

“We may not see the level of mortality that we’re really concerned about,” Seema Lakdawala, a virologist at Emory University, told The New York Times. “Preexisting immunity to seasonal flu strains will provide some protection from severe disease.”

Agencies contributed to this story.


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