Research Roundup: In the Unvaccinated, COVID-19 Reinfection May Still be Possible and More
Every week there are numerous scientific studies published. Here’s a look at some of the more interesting ones.
In Unvaccinated, Strong Protection from COVID-19 Infection is Short-Lived
During the course of the COVID-19 pandemic, one of the open questions has been whether being sick with COVID-19 would protect you from re-infection. In light of breakthrough infections in people who are vaccinated, it was even more of a pressing question. Researchers with the Yale School of Public Health and the University of North Carolina at Charlotte published a study in the journal The Lancet Microbe that suggests that protection after natural infection is short-lived.
“Reinfection can reasonably happen in three months or less,” said Jeffrey Townsend, the Elihu Professor of Biostatistics at the Yale School of Public Health and lead author of the study. “Therefore, those who have been naturally infected should get vaccinated. Previous infection alone can offer very little long-term protection.”
The researchers analyzed data about reinfection and immunological numbers from the close viral relatives of SARS-CoV-2 that cause “common colds” as well as data from SARS-CoV-1 (SARS) and Middle East Respiratory Syndrome (MERS). Using evolutionary principles, they modeled the risk of COVID-19 reinfection over time. Their model has similarities to reinfection risks over time between COVID-19 and endemic coronaviruses, which is to say, coronaviruses that cause colds or other illnesses.
“We tend to think about immunity as being immune or not immune,” said Alex Dornburg, assistant professor of bioinformatics and genomics at the University of North Carolina at Charlotte, who co-led the study. “As new variants arise, previous immune responses become less effective at combating the virus. Those who were naturally infected early in the pandemic are increasingly likely to become reinfected in the near future.”
The authors admit there are limitations to the study, which was based on published results on relatively small numbers of infected individuals and is based on mathematical models. It also does not take into consideration the severity of the original infection and whether the infection was asymptomatic. It also leans heavily on the protective immunity of antibody-based immunity and cell-mediated immunity but doesn’t really evaluate memory B- and T-cells, which may provide longer-term immunity.
The authors wrote, “The probabilistic framework of our analysis does not capture these aspects, their interactions, and other aspects of SARS-CoV-2 infection that merit special attention. For example, asymptomatic infection by SARS-CoV-2 can induce a weaker immune response than symptomatic infection, which in turn would result in lower production of antibodies, and consequently shorter-term resistance against reinfection over time. This observation is of particular importance as reinfection can lead to lower infection severity than primary infection.”
Aging Effects the Gut Microbiome
The microbiome is the trillions of bacteria, viruses and fungi that live in the body. Investigators at the Cedars-Sinai Medical Center found that aging caused significant changes in the human small intestine microbiome that is distinct from what is caused by drugs or illness. This was the first study of its kind to evaluate samples from the small intestine, which is over 20 feet in length and has a surface area of a tennis court. It was in people 18 years of age to 80. One of the key findings was that as people age, the bacteria in the small intestine changes from microbes that prefer oxygen to bacteria that survive with less oxygen. The theory is that because the small bowel plays a significant role in nutrient absorption, the changes in gut microbiome likely have a big impact on human health.
Link Between Crohn’s Disease and Fatty Tissue in the Gut
Researchers from the University of Limerick in Ireland found a connection between Crohn’s disease, an inflammatory bowel disease, and a fatty intestine. The researchers performed body composition analysis of Crohn’s patients and found that Crohn’s patients incorporate fat into their body differently than people who do not have Crohn’s. And this seems to preferentially lay down fat on the lower parts of their body instead of the abdomen. This was in the abdominal areas where the intestines are located. The techniques they used are more commonly used to study athletes or to research changes in the body during aging. But in this case, they found that inflammation in the intestine from Crohn’s disease is directly linked to fatty tissue in those locations.
Linker Histones Tune Chromosomes
DNA doesn’t just float around in the cell. It is coiled into chromosomes, which align and duplicate during cell division. In fact, the cell nucleus is about 10 microns in size, but DNA is about six feet long. It’s not just a matter of getting all the DNA into the nucleus, but it has to stay organized, coiled into loops so the genetic information is accessible and doesn’t get tangled into a knot. Chromosomes are also coiled around proteins called histones, but researchers at Rockefeller University have identified specific proteins called linker histones that control whether DNA winds into long and thin chromosomes and how coiled they are. Specifically, they found that the linker histones control the number of loops in the chromosome and its ultimate shape.
Major Shift in Treating Type 2 Diabetes
An international panel of experts from four major diabetes research centers, including UT Southwestern Medical Center, reviewed current literature and is recommending a significant change in treatment paradigms for Type 2 diabetes. The primary shift is to focus on obesity first and glucose control second. The researchers found that dropping 15% or more of body weight can have a disease-modifying effect on Type 2 diabetes, which is an outcome that can’t be made using any other glucose-lowering intervention. They note that this would require updating current treatment guidelines and significant provider education. Current approaches depend on clinical studies from the 1980s, that indicated lowering blood sugar resulted in fewer complications, and caused physicians to focus on blood glucose levels first.
“The problem with this approach is that it doesn’t address the core problem and does not offer an opportunity to reverse the disease,” said first author Lidiko Lingvay, Professor of Internal Medicine and Population and Data Sciences at UT Southwestern. “We propose using a proactive approach. Let’s address the cause of the disease — obesity.”