Oct 22, 2023 21:00:00

Infection with parasites may reduce hospitalization and mortality rates due to the new coronavirus

In some regions of Africa and Asia where

helminths that parasitize the human body are endemic, it has been reported that there are fewer severe cases of coronavirus infection (COVID-19) that can lead to hospitalization or death. A research team from the U.S. National Institute of Allergy and Infectious Diseases (NIAID) has announced a new study showing that ``infection with parasites may lower the rate of death from COVID-19.''

Exposure to lung-migrating helminth protects against murine SARS-CoV-2 infection through macrophage-dependent T cell activation | Science Immunology
https://www.science.org/doi/10.1126/sciimmunol.adf8161

Relation of Parasitic Worm Infection and SARS-CoV-2 Explored | NIH: National Institute of Allergy and Infectious Diseases
https://www.niaid.nih.gov/news-events/parasiticwormsarscov2

Prior hookworm infection could offer protection from severe COVID-19 symptoms
https://medicalxpress.com/news/2023-08-prior-hookworm-infection-severe-covid-.html

Kelly Hilligan, who was affiliated with NIAID at the time of the study and is a postdoctoral fellow at New Zealand's Malaghan Institute of Medical Research at the time of writing, said, ``This study was based on the assumption that in certain regions of the world, there was a It stems from the observation that the outcome was not as bad as it could have been.'

To date, some countries in Africa and Asia have reported fewer severe cases of COVID-19 than other regions, a finding that holds true even after accounting for associated factors and the proportion of cases reported. About. Hilligan explains why this is so: ``What's interesting is that these areas are highly correlated or overlap with areas where hookworm infections are endemic.'' In fact, an Ethiopian study suggested that patients infected with the parasite may have a stronger immune system, which in turn may reduce their risk of contracting COVID-19.

'Generally speaking, it is thought that when an infectious disease stimulates and activates the immune system, it has the benefit of preventing or eliminating other pathogens,' Hilligan said. In the case of -19, this effect seems to apply regardless of whether it is a virus, bacteria, or parasite.'

Hilligan and his team used mice, which have immune systems and cells similar to those of humans, to investigate the risk of infection with a parasite called Nippostrongylus brasiliensis (N. brasiliensis), which infects the lungs of rodents, and the risk of COVID-19. We conducted an experiment to investigate the relationship between In the experiment, mice were first infected with N. brasiliensis and then exposed to a lethal dose of SARS-CoV-2. When N. brasiliensis infects mice, it moves to the lungs and causes some damage, but once removed, the damage is quickly repaired.

As a result of the experiment, about 60% of mice previously infected with N. brasiliensis survived even if infected with SARS-CoV-2, whereas about 20% of mice that had not been infected with N. brasiliensis in the past survived. Only % survived. Additionally, the same degree of protection was not seen in mice in which N. brasiliensis was removed before it migrated to the lungs, suggesting that migration of the parasite to the lungs is effective in preventing severe COVID-19. It was suggested.

When the research team measured the viral load in mice, they found that on the third day after infection with SARS-CoV-2, the viral load in the body of mice with and without parasite infection was the same. It was also found that mice infected with the parasite had a much lower amount of virus seven days after infection. This indicates that parasite infection improves

the acquired immune system in response to the infected virus, rather than the innate immune system suppressing the viral infection itself.

Further analyzing the immune system, the researchers found that macrophages , which detect invading pathogens and send signals to the immune system, were more activated in mice infected with N. brasiliensis. As a result, the amount of immune cells called CD8+ T cells , which eliminate virus-infected cells, was much higher in the mice infected with the parasite.

'We found that the induction of CD8+ T cells, which are essential for the viral response, is enhanced,' Hilligan said. 'Thanks to these engineered macrophages, T cells enter infected tissues more quickly and This effect appears to be long-lasting: even after the parasite has been cleared from the body, macrophages induce CD8+ T cells to become activated. He maintained a very strong ability to transform.'

Although this research is based on animal experiments using mice and has not yet been confirmed in humans, the researchers say they are focusing on the relationship between macrophages and parasites. 'Now we want to understand the signals that attract T cells to the lungs,' Hilligan said. 'We also want to understand what the parasite does to create these specialized macrophages, and whether it requires the parasite. I would also like to know if it is possible to recreate Zuko's effect.''