What Is a Chronic Viral Infection?

Chronic virus infection

Chronic viral infection

Referred to as SVI. A general term for viral infectious diseases with a very long incubation period. Also called late-onset viral infection. After the onset, the disease progresses quite quickly and almost never improves and dies. Mostly invade the central nervous system of mammals [encephalopathy of mink, Scarpie of sheep, human Kuru and subacute sclerosing panenitis (Subacutescleros-ing pancephalitis, etc.), and pneumonia caused by sheep like Visra and Maedi , Nephritis caused by mink Aleutian disease.

Chronic viral infection disease name

Chronic virus infection

Classification of chronic viral infections

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Chronic viral infection disease description

The reason for the long incubation period is unclear, considering the complex interaction between the virus and the host. In recent years, the earliest isolation of measles virus from human SSPE patients' brains has accumulated a wealth of data. Another source of sheep's Scrapie is DNA-type viroids.

Study on Chronic Virus Infection

?? On December 28, 2006, the website of Nature magazine will report on the new findings by researchers from the Dana-Farber Cancer Institute and Emory University. They found that the immune effect driven by CD8T cells in mice was caused by a single gene. This finding raises the possibility of improving patients' CD8 cell depletion and improves immune defenses against chronic viral infections including hepatitis and AIDS.

"CD8T cells that respond to viral infections have been found to have" memory "functions against the viruses they encounter, so they can respond quickly to new infections with these viruses," said the author of the study, Dr. Gordon Freeman, Dana-Farber Institute Say. However, in the case of a chronic viral infection, memory cells gradually become depleted and lose their ability to respond to the virus. It is unclear why this happens at the molecular level. Another lead author, Dr. Rafi Ahmed of Emory University, added.

?? To find out why, Gordon Freeman and his colleagues performed a "microsequence" experiment that examined the activity of thousands of genes in normal memory CD8T cells and "depleted" cells in mice. They found that a gene called PD-1 was more active in "depleted" cells.

It was concluded from previous studies that PD-1 is associated with a specific receptor for CD8 cells and exists as a small pocket that receives signals from other cells. In 2001, Freeman and his colleagues found that when the PD-1 receptor binds to the PD-L1 molecule, the immune system's response to the infection weakens. Freeman's team produced antibodies to block the response.

"When co-author John Wherry of the Wistar Institute found high levels of the PD-1 gene in a microsequence experiment, we thought, was it the depletion of CD8 cells?" Freeman said. Assistant medical professor in the hospital. "We found a markedly large number of PD-1 receptors in depleted CD8T cells in mice, which blocked the binding of PD-1 / PD-L1 and activated the cells in response to infection.

Although it is not yet known why CD8 cells become depleted-approximately one month after the onset of infection begins. Scientists think it may be part of the body's system, naturally ending the immune response after infection. If it lasts too long, the immune response can damage normal or healthy tissue. In mouse experiments, CD8T cells will recover again. As long as researchers continue to give PD-1 / PD-L1 blockers, the possibility of immune system disorders will be very small.

?? Human CD8T cells and mice have a similar mechanism, the new discovery can provide a simple immune pathway to treat chronic viral infections. Freeman's lab is also investigating whether anti-cancer T cells have also decreased in HIV-infected individuals and many types of cancer patients.

"The potential applications for this work are very broad," Freeman emphasized. It is worth mentioning that he and his colleagues have recently received funding from Bill Gates' Global Health Challenge, and will conduct further research on hepatitis C infection.

Chronic viral infection response

The main problem facing the invention of vaccines or treatment of infectious diseases is that chronic infectious diseases can gradually prevent the ability of immune T cells to respond. Now, a team led by researchers led by Emory University in the United States has revealed an important way for chronic viral infections to escape the immune response. The results of this study were published online in the recent PNAS (Proceedings of the National Academy of Sciences).

Using mouse models, researchers found that a chronic lymphocytic choroid plexus meningitis virus (LCMV) can attack stromal cells called fibroblastic reticulocytes (FRCs) in a lymphoid organ. Acute viruses have no effect on FRC.

FRC provides a three-dimensional network for immune cells to move and interact with other immune cells in lymphoid organs (spleen, lymph nodes). FRC is important for initiating the immune response. Scientists have discovered that the spread of FRC infection will lead to the disruption of this important stromal cell function. Last year, a team led by Emory scientist Rafi Ahmed found that in mice, another immune response pathway to chronic infection was interrupted-a pathway called PD-1 that blocks the chronic LCMV response.

The team found that FRC infection may be related to the PD-1 pathway previously discovered. PD-L1, the main partner of PD-1, increased after FRC infection. The PD-1 pathway may prevent the interaction between CD8 + T cells and FRC and prevent the destruction of FRC structure in the spleen. This can help the virus to continue to infect FRC and cause chronic long-term virus presence.

Lymphocytic choriomeningitis (LCM) is a central nervous system infection caused by lymphocytic choriomeningitis virus. Men with mild symptoms may have a cold. Meningitis may occur in a few typical cases. The general condition is mild and the mortality rate is extremely low. There are few autopsy reports, so pathological changes are unknown.

After death of severe meningitis cases, autopsy revealed extensive infiltration of perivascular monocytes in the cerebral cortex, medulla oblongata, pontine and cerebellar cortex. Virus antigen was detected in nerve cells of meninges and cerebral cortex by immunofluorescence, indicating that the virus can directly invade nerve cells.

This disease is a disease inherent in house rats, and people are infected by eating contaminated food from urine or feces or inhaling contaminated dust. There are not many human cases, but they are widely distributed in the world. They are found in Europe, America and Asia. A few cases have been reported in China. In addition, laboratory workers may be infected.

The lymphocytic choroid plexus meningitis virus belongs to the family Viridae. After being infected, humans usually present as a recessive infection and can also develop disease. The incubation period is 6 to 13 days. There are three clinical manifestations: flu-like or non-neurological infections, aseptic meningitis, and meningoencephalomyelitis. Both were common before. Similar flu-type manifestations include fever, burnout, loss of appetite, headache, myalgia, runny nose, and sometimes sore throat, joint pain, cough, photophobia, vomiting, and rashes, accompanied by leukocytes and thrombocytopenia. The course of the disease lasts 4 to 7 days and can be cured. Meningitis type also has flu-like symptoms at the beginning, but fever can be recurred during the course of the disease, accompanied by headaches, vomiting, and signs of meningitis, such as neck stiffness and pathological reflexes. Cerebrospinal fluid changes are increased lymphocytes, increased protein content, and cerebrospinal fluid contains viruses. The course of the disease lasts for several weeks and can be cured. Very few serious patients have suffered coma and death. A few patients can have sequelae, such as Parkinson's syndrome. This virus infection can also cause teratoids, miscarriages and neonatal hydrocephalus.

During fever, there is a virus in the blood. When the central nervous system is infected, there is a virus in the cerebrospinal fluid. Detection of IgM antibodies in serum and cerebrospinal fluid in the acute phase can be used as a method of early diagnosis. Neutralizing antibodies appear later, last longer, and have a lower titer.

There are currently no specific therapies, and symptomatic and supportive therapies can be used. Rodent control is the main measure to prevent the disease.

Chronic viral infection prevention

Among the most economical strategies for preventing viral infections, vaccines have proven to be effective in preventing acute, self-limiting viral infections. For these infections, vaccines can fully mimic natural viruses. However, the immune response induced by chronic infection viruses is not enough to clear the infection, and therefore, vaccines directed against these viruses must induce immune responses that are more qualitative and quantitative than natural infections. The article discusses the immunological and virological basis of vaccines against three such viruses, namely HIV, HCV and human papilloma virus (HPV), and reviews the latest presentations of clinical trials. At the same time, some new methods for improving the immunogenicity and effectiveness of vaccines have been explored.