This week’s summary of some of the latest scientific studies on the novel coronavirus and efforts to find treatments for COVID-19 acknowledge the obstacles in the vaccine race to immunize the world, especially when it comes to cancer patients, while trace the doors of entry of the coronavirus. and dispelling myths about vitamins.
MRNA vaccines may need further study to treat some cancer patients
COVID-19 vaccines that employ new messenger RNA (mRNA) technology to defend against disease may require further testing before it becomes clear that they are safe for cancer patients with solid tumors, cancer treatment experts say. That would include vaccines from Pfizer Inc. with its partner BioNTech SE and Moderna Inc.
Vaccines work by carrying genetic instructions to make a virus protein that the immune system learns to recognize and defend itself. The mRNA is encased in a microscopic “package” called a lipid nanoparticle (LNP) or liposome, which protects and delivers the fragile molecule to cells.
While this technique is new to vaccines, it has long been used to deliver anticancer drugs to tumors, because liposomes are readily absorbed by tumors. This raises the possibility that tumor tissues capture some of the liposomes that carry the mRNA from the vaccine, said Gerard Milano of the University of Nice in France.
The possibility of part of the vaccine getting stuck in tumors and the resulting effect in cancer patients “is an open question for which there is currently no answer,” Milano said.
In an article published in the British Journal of Cancer, his team calls for “a careful evaluation of the efficacy of these promising COVID-19 mRNA vaccines administered as lipid carriers for patients with solid tumors, including a possible re-evaluation of the dose for protection. optimal of this specific and fragile population “.
The new coronavirus crosses the membranes between the throat and the brain
The coronavirus uses the nose as a gateway to the brain, autopsy findings suggest. The presence of the virus in the brain and cerebrospinal fluid has been linked to neurological symptoms, but it is not clear exactly how the virus enters the central nervous system.
During autopsies of 33 patients who died of COVID-19, researchers examined the nasopharynx, the region where the nasal cavity connects to the back of the throat, which is located very close to the brain. By dissecting the cells and following the path of infection, they saw the virus invade the brain, crossing the mucous membranes that separate it from the nasopharynx.
From there, according to a report published in Nature Neuroscience, it can travel along the nerve fibers that connect the nasal cavity with the part of the brain involved in the sense of smell, which would explain “some of the well-documented neurological symptoms in COVID-19, including alterations in smell and taste perception. “
The researchers also found virus particles in regions of the brain with no direct connection to the nose, suggesting that there may be additional routes for the virus to enter the brain.
Vitamin D does not help in severe cases of COVID-19
Low levels of vitamin D have been linked to an increased risk of severe COVID-19, but high levels of vitamin D do not fix the problem.
Increasing vitamin D levels in critically ill patients did not shorten their hospital stay or decrease their chances of being transferred to intensive care, needing mechanical ventilation or dying, doctors in Brazil found.
240 hospitalized patients with severe COVID-19 were randomly given a single high dose of vitamin D3 or a placebo. Only 6.7% of patients in the vitamin D group had “deficient” levels of the nutrient compared to 51.5% of patients in the placebo group, but there were no differences in the results, according to an article published in medRxiv prior to peer review. The same thing happened when the researchers focused on 116 vitamin D-deficient patients before treatment.
The authors say theirs is the first randomized trial of its kind to show that vitamin D supplementation “is ineffective in improving length of hospital stay or any other clinical outcome among hospitalized patients with severe COVID-19.”
The immune system responds strongly in asymptomatic COVID-19
Asymptomatic people infected with COVID-19 are generating robust immune responses that differ from responses in those who get sick, according to a study that appears to contradict previous thinking by health experts.
The researchers studied immune system T cells in 76 symptomatic COVID-19 patients and 85 infected individuals without symptoms and reported their findings in bioRxiv prior to peer review.
Some of these cells, CD8 + T cells, can recognize virus-infected cells and destroy them. They also make inflammatory proteins, or cytokines, that help prevent the virus from making copies of itself. Others, known as CD4 helper T cells, help the body make B cells, which make antibodies.
All study participants had similar frequencies of T cells that could recognize the virus and destroy infected cells, regardless of whether they had symptoms. But T cells from asymptomatic individuals produced higher levels of cytokines important to fight the virus, including interferon-gamma and interleukin-2.
“What we still need to understand is whether these T cells can persist over time and offer long-term immunity,” said co-author Antonio Bertoletti of the Duke-NUS School of Medicine in Singapore.