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Infectious Disease Immune System

Time of Day Influences Susceptibility to Infections

7 months, 3 weeks ago

1658  0
Posted on Apr 27, 2017, 6 a.m.

Circadian rhythm affects the ability of viruses to replicate and spread between cells, causing higher susceptibility to infection at certain times of the day.

Routinely disrupted patterns in the body, such as unpredictable sleep patterns and shift work, play a major role in how and when infections occur in the body. A study suggests that people are more susceptible to infections at specific times of the day. It is during this time that the body’s anatomy promotes the growth and development of viruses that replicate and migrate between the cells. The study sheds light on why shift workers whose bodies constantly go through disruptive patterns are more prone to chronic diseases, infections, and other health problems. When a foreign object enters the body, it takes over the structure of the cells and reproduces itself (depending on the time of day). The body resources fluctuate constantly in response to the body’s circadian rhythm.

New Tests Reveals the Difference between Early and Late Virus Replication
When mice were infected with the herpes virus at various hours of the day, researchers were astonished at the results. In mice that were infected in the early hours of the day, the virus had reproduced itself 10 times greater than mice that were infected during the later part of the day. The controlled environment allowed the mice to experience 12 hours of light and 12 hours of dark.

The responses from each group were different, as the results were dependent upon the circadian rhythm, which controls body temperature, immune systems, and sleep patterns. Researchers repeated the test with mice without the specific circadian rhythm gene factor, and found that no matter what time of day, the viral replication remained higher in the infected mice.

Consistent Studies Unlock New Information
What does this mean? It means that the time of day an infection develops can cause the onset of a more acute infection. According to Professor Akhilesh Reddy, the senior author of the study, “This is consistent with recent studies which have shown that the time of day that influenza vaccine is administered can influence how effectively it works.”

First author, Dr. Rachel Edgar, states that each cell in the body has its own biological clock which allows the cells to keep track of how often they change throughout the day. This information suggests that the cells use the clock to determine how successively a virus replicates itself. Tests concluded that no matter what time of day the normal patterns of the body were disturbed, replication had always been high.This test indicates that shift workers who work at night and rest during the day have a disrupted biological clock, and they are more susceptible to viral diseases.

It seems that some infections and diseases are seasonal, and many are less active during certain seasons of the year. Researchers explain this theory by comparing the disease influenza, which affects thousands of people during the winter months.

Researchers found that the herpes virus can manipulate the body’s molecular clockwork, which controls the circadian rhythm, which in turn helps the virus to progress. Some diseases use the body’s cells to replicate itself. One such disease is the malaria parasite, which successively reproduces itself. The body is designed to defend itself against unknown pathogens.

Edgar, RS et al. Cell autonomous regulation of herpes and influenza virus infection by the circadian clock. PNAS, 15 Aug 2016 DOI: 10.1073/pnas.1601895113

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