Herpesvirus infections can manifest themselves in different ways: their pathogenesis extends from an asymptomatic course, lesions of the skin and mucous membranes to malignant formations and disorders of the brain. When the herpes virus enters the body, it remains in it to live forever. The quality of life of a person who has the herpes virus depends on the interferon system’s operation.
Primary herpetic infection
At the first encounter with the virus, the body activates its interferon system (IFN). It triggers all the mechanisms of antiviral defense and stimulates both innate and acquired immunity. The IFN system principles are described in the article “The role of interferons in the evolution of vertebrates”.
If the interferon system works without failures, then the immune system quickly copes with the acute phase of herpes infection. Some immune cells destroy the virus particles, while others produce antibodies against the virus to protect against re-infection.
The acute phase of herpetic infection is successfully treated with local and systemic drugs.
Latent form of herpetic infection
The herpes virus, unlike many other types of viruses, can retain its genetic information in the infected body even after the acute phase of the disease. The viral DNA penetrates the cell nucleus, attaches to the chromosomes, and does not manifest itself in any way. It waits for favorable conditions for reproduction.
Immune cells cannot detect and destroy the virus’s DNA hidden in the nuclei of tissue cells. It is called a hidden (latent) form of herpetic infection.
There are no ways to treat the latent form of the disease yet. Advanced research in this area is being conducted in mice. For example, in 2020, an American-French team of scientists investigated the possibility of editing the virus genome in a latent state in infected mice. The scientists used a particular enzyme that can recognize the viral genome in the nuclei of cells and change it so that the genome becomes inoperable. The experiment was successful – more than 90% of the viral DNA was deactivated in the experimental mice.
Another study conducted by American scientists in 2019 at Harvard Medical School showed that the interferon system also has a tool for keeping the virus in a latent state. Scientists have discovered a filamentous protein that is produced when stimulated by interferon. This protein clings to the viral DNA and mechanically prevents it from synthesizing new viral particles.
Recurrent herpetic infection
The decrease in the body’s immunity is a favorable condition for the reproduction of viral particles. Herpes relapse can cause stress, lack of sleep, hypothermia, infectious diseases, hormonal changes, and immunosuppressive therapy. The viral DNA, which is in a latent state, detects the deterioration of the host cell’s energy balance and starts synthesizing new viral particles. That is how the acute phase of the disease begins.
During recurrent herpes, the production of interferons decreases in patients, the activity of cells of the immune system decreases, lesions appear on the skin and mucous membranes. The patient becomes infectious: the foci contain a large number of viable viral particles.
Relapses of herpetic infection are successfully treated with local or systemic drugs. After the end of the acute phase, the disease again passes into a latent form.
Particularly dangerous manifestations of herpetic infection
The herpes virus can affect all human organs.
During the acute phase of the disease, the virus often penetrates through nerve cells’ processes into the brain. In rare cases, this leads to acute inflammation and encephalitis.
Herpetic encephalitis is associated with genetic mutations that disrupt the interferon system. In 2015, scientists from Germany, Denmark, and Japan studied a case of herpetic encephalitis in a 15-year-old teenager. Scientists have found that encephalitis is associated with defects in the synthesis of IFN molecules and a violation of signals transmission of the interferon system inside the cell.
When the herpes virus attacks brain cells, the consequences of the disease may not appear immediately. In 2020, an international team of scientists from Italy and France published a review in which they collected research that recurrent herpes infection can lead to cognitive impairment and Alzheimer’s disease.
Sources
Functional IRF3 deficiency in a patient with herpes simplex encephalitis
Herpes Simplex Virus-1 in the Brain: The Dark Side of a Sneaky Infection
Gene editing and elimination of latent herpes simplex virus in vivo
