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Vaccine Blocks Covid-19 Infections in Animal Tests


(frolicsomepl, Pixabay)

20 Aug. 2020. An experimental vaccine shows in challenge tests with monkeys it protects against Covid-19 infections in nose, throat, and airways. Results of the tests, conducted by developer of the vaccine Novavax in Gaithersburg, Maryland, appear in a non-peer reviewed paper appearing yesterday on the bioRxiv preprint server.

Novavax creates vaccines protecting against infectious diseases with nanoscale particles of synthetic proteins designed specifically against the genetic code of their targets. The company says it infects cells from reproductive systems of the fall armyworm, a tropical insect, with engineered viruses that grow only in those cells. The engineered viruses are designed to express surface proteins that trigger an immune response, which make up the nanoscale particles in their vaccines.

The researchers, led by Novavax’s vice-president for vaccine development Gale Smith, tested the company’s Covid-19 vaccine, code-named NVX-CoV2373, in macaque monkeys. NVX-CoV2373 is designed to generate antibodies that neutralize the SARS-CoV-2 coronavirus responsible for Covid-19 infections with one dose, and with two doses produce these antibodies with a titer volume — a measure of antibody concentration — likely to be effective in humans. Novavax also produces an adjuvant, a vaccine additive called Matrix-M to boost immune responses, allowing for lower doses of the primary vaccine.

The team first randomly assigned the monkeys to receive NVX-CoV2373 in doses of 2.5, 5, or 25 micrograms, combined with Matrix-M, or a placebo, 21 days apart. The animals were then exposed to SARS-CoV-2 coronaviruses in their nasal passages, throat, and lower airways. The researchers tested the monkeys for SARS-CoV-2 viral load two days, four days, and two weeks following exposure to the coronavirus.

The results show all doses of NVX-CoV2373 produced immunoglobulin G, or IgG, antibodies neutralizing SARS-CoV-2 at levels that exceed comparable levels of antibodies in convalescent plasma taken from recovered Covid-19 patients, when tested two weeks after the second vaccination. In fact, all vaccinated animals cleared the viruses after four days. After seven days, tissue specimens from the monkeys’ lungs receiving NVX-CoV2373 showed little or no inflammation, while placebo recipients had moderate to severe lung inflammation.

Earlier in August, Novavax reported its first results from an early- and mid-stage clinical trial of NVX-CoV2373, again in a non-peer reviewed preprint. Those results show largely mild reactions to the vaccine among the 131 healthy volunteers receiving two injections, including tenderness or pain near the injections, as well as headache, fatigue, or muscle aches. Participants receiving the vaccine also developed neutralizing IgG antibodies after two vaccinations, even at the lower dose. Among a part of the test group receiving NVX-CoV2373 plus Matrix-M adjuvant, those participants developed T-cells in the immune system, as well as antibodies to attack the coronavirus.

As reported by Science & Enterprise last month, the Biomedical Advanced Research and Development Authority, or BARDA, with the U.S. Department of Defense, are contracting with Novavax to purchase large quantities of NVX-CoV2373, in anticipation of continued favorable clinical trial results.

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Hat tip: Endpoints News

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