New Saudi MERS case as teams publish animal studies

The dribble of MERS-CoV cases continues in Saudi Arabia with one more case reported today, with disease activity flat-lining in South Korea, where the country's leader announced that the outbreak has ended.

In scientific developments, two different animal studies yielded promising findings about a two-step vaccine strategy against the virus and a possible monoclonal antibody treatment.

Saudi illness, death

Saudi Arabia's Ministry of Health (MOH) today reported one new MERS-CoV (Middle East respiratory syndrome coronavirus) infection, involving a 44-year-old Saudi woman from Al-Kharj, located in the south-central part of the country near Riyadh.

Hospitalized in stable condition, she is not a healthcare worker, and her contact with suspected or confirmed cases in community or hospital settings is under investigation.

Also, the MOH reported the death of a previously announced case today, that of a 60-year-old Saudi woman from Riyadh who had a preexisting health condition.

The reports lift Saudi Arabia's total from the disease to 1,056 cases, including 467 deaths. Seven people are still being treated for their infections, and 582 people have recovered.

Korea anticipates MERS-free status

With no more patients under isolation and monitoring, South Korea's prime minister Hwang Kyo-anh today said the country's MERS outbreak is over, though official World Health Organization (WHO) declaration is still a few weeks away, the Korea Times reported today.

Only one patient is waiting for tests to show that the virus has cleared from his or her system, according to the report. The WHO typically waits for two incubation periods to pass after tests show the last patient is free of the virus. For MERS-CoV, two incubation periods would be 28 days, putting the WHO's official date to the end of August, if South Korea reports no new cases in the interim.

In a statement today, the WHO's Western Pacific Region office said the country hasn't reported a new case since Jul 4, and it acknowledged that all remaining contacts were released from quarantine yesterday. The outbreak total remains at 186 cases, 36 of them fatal.

The office's director, Shin Song-soo, MD, in the statement urged countries to remain vigilant for MERS-CoV cases and for healthcare workers to continue practicing stringent infection control practices.

"In our interconnected world, pathogens can travel rapidly, and outbreaks can occur in unexpected places," Shin said in the statement. "All countries in WHO's Western Pacific Region must remain alert for the possibility of an imported case of MERS-CoV and any other infectious disease and be ready to respond swiftly and efficiently."

Since the virus emerged in Saudi Arabia in 2012, the WHO said it has received reports of 1,374 MERS-CoV infections, including at least 490 deaths.

Candidate vaccine study

A prime-boost regimen of experimental vaccines against MERS-CoV showed promising results in animal studies, according to study findings published in Nature Communications today by team based at the National Institute of Allergy and Infectious Diseases (NIAID) Vaccine Research Center.

The candidate vaccines were designed with a strategy based on an understanding of viral components and their interactions with host cells, according to the NIAID. Specifically, they used information about the spike glycoprotein, which the MERS virus uses to enter cells. Using that information, the researchers designed several experimental vaccines that they gave to mice, a two-step regimen involving a priming vaccine followed several weeks later by the same or a different booster vaccine.

Currently, there is no MERS-CoV vaccine for humans, but researchers hope they can use the strategy to one day develop similar ones for humans.

The three regimens that showed the strongest response in mice were then given to groups of macaques, which had similar immune responses. Macaques don't develop typical MERS-CoV infections, but unvaccinated animals challenged with the virus had lung abnormalities consistent with pneumonia that were more severe and longer lasting than in vaccinated animals.

According to the NIAID statement, the research team is refining the vaccine candidates with a goal of testing a second-generation version in clinical trials.

Promising antibody

In another MERS countermeasure development, researchers yesterday reported on the first known isolation of a strong MERS-CoV neutralizing antibody from memory B cells of an infected patient. A Swiss-led international group of researchers published their findings in Proceedings of the National Academy of Sciences (PNAS).

They found that the antibody binds to a novel site on the spike protein, which interferes with cell receptor binding.

In mouse experiments, the monoclonal antibody was effective for prophylaxis and treatment.

See also:

Jul 28 MOH update

Jul 28 Korea Times report

Jul 28 WHO Western Pacific Region office statement

Jul 28 NIAID press release

Jul 28 Nature Communications abstract

Jul 27 PNAS abstract

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