viral hepatitis C
Introduction
Introduction to hepatitis C virus Hepatitis C virus is caused by hepatitis C virus (HCV) and is caused by blood transfusion or blood products, blood dialysis, apheresis and blood transfusion, kidney transplantation, intravenous drug use, sexual transmission, and mother-to-child transmission. basic knowledge The proportion of the disease: the probability of the population is 0.1% Susceptible people: no specific people Mode of infection: blood transmission Complications: fatty liver cirrhosis
Cause
Cause of hepatitis C virus
(1) Causes of the disease
HCV is a blood-borne type of hepatitis virus. In 1989, Chiron Corporation of the United States applied molecular cloning technology to successfully clone (HCV) cDNA. HCV is the first human virus discovered by molecular biology technology. HCV belongs to the hood. Virology, its biological traits, gene structure and yellow virus, prion similar, has been confirmed that HCV is a spherical particle containing a lipid shell, diameter 30 ~ 60nm, HCV genome is a long positive chain, single-stranded RNA, long 9.5Kb, the HCV genome has a large open reading frame (ORF) encoding a 3010 or 3011 amino acid polyprotein. The encoded polyprotein body has a distinct structure with the flavivirus: structural proteins (including core proteins and envelope proteins) And non-structural proteins (NS1-NS5).
HCV is an RNA virus, which is relatively easy to mutate. Only 68.1% to 91.8% of the nucleotides in different regions are identical. According to the difference in HCV gene sequence, they can be divided into different genotypes. Currently, there is no uniform standard for HCV genotyping. Methods, Okamoto divided HCV into four genotypes I, II, III, and IV. According to their classification, most of North America, European HCV strains belong to type I, Japan is mainly type II, and also has type III and type IV. According to Wang Yu, the northern cities are mainly type II and type III, while in southern cities, more than 90% are type II.
(two) pathogenesis
1. Direct pathogenic effects of HCV infection Many studies have shown that the severity of liver tissue inflammation in HCV-infected patients is related to viremia. The severity of liver tissue inflammation in patients with chronic hepatitis C is related to the level of HCV RNA in hepatocytes. The correlation of HCV RNA levels is stronger. After treatment with interferon, serum ALT levels are gradually decreased with the decrease of serum HCV RNA content. The above results suggest that HCV may have direct pathogenic effects. However, immunohistochemical study The expression of HCV antigen in liver tissue has not been fully proved to be related to the inflammatory activity of liver disease. Groff et al. found that the presence of HCV antigen in hepatocytes does not necessarily indicate the presence of hepatocytes. HCV granules, liver disease inflammatory activities are not necessarily related to HCV antigen expression in hepatocytes. Related, and liver tissue inflammation is related to the presence of HCV virions in hepatocytes. It also indicates that HCV has direct cytopathic effects. The direct pathogenic effect of HCV may presumably replicate with HCV in hepatocytes, causing changes in liver cell structure and function. , or interfere with liver cell protein synthesis caused by hepatocyte degeneration and necrosis, the presence of HCV asymptomatic carrier It seems to suggest that HCV has no direct pathogenic effect, but recently reported that most of the "chronic HCV carriers" liver tissues with normal ALT persisted in different degrees of pathological changes and inflammation, and the degree of liver tissue inflammation damage is related to HCV replication level, indicating that there is no The state of symptoms is less common and further supports the direct pathogenic role of HCV.
2. Cell-mediated immune damage may be the main cause of liver disease caused by HCV. One of the important features of hepatitis C liver histopathology is the accumulation of lymphocytes in the portal area, sometimes forming lymphoid follicles. Hepatitis is obvious, lymphocyte infiltration is undoubtedly related to immune response. Some scholars have proved that the lymphocytes infiltrated in chronic hepatitis C are mainly CD8+ cells, many of which have active epitopes, which are shown to be activated, and lymphocytes are observed under electron microscope. The cells are in close contact with the liver cells, suggesting that it has toxic damage to the liver cells. Mondelli et al. have confirmed that the toxicity of chronic non-A, non-B hepatitis cytotoxic T cells on autologous hepatocytes is increased in chronic hepatitis C and cytotoxicity. Mainly caused by T cells, on the contrary, in patients with autoimmune hepatitis, immune effector cells are limited to non-T lymphocytes. In chronic HBV infection, non-T and T lymphocytes are involved in hepatocyte injury, and HCV-specific antigens can activate CD8+. And CD56+ cells suggest that CD56+ cells also play an important role in the pathogenesis of chronic hepatitis C, chronic hepatitis C Intrahepatic T cells can recognize the C protein of HCV, multiple antigenic determinants of E1 and E2/NS1 proteins, and this recognition is restricted by HLA-I, which also indicates that Tc cells play a role in the pathogenesis of chronic hepatitis C. Other studies have shown that most of the chronic HCV-infected patients with peripheral blood and liver tissue restricted by HLA-II molecules CD4+ cells (TH-1 cells) can attack HCV-specific immune antigenic determinants, CD4+ cells to HCV core antigen The response is related to hepatic inflammatory activity. TH-1 cells play a key role in chronic hepatitis C. HCV-specific TH cell surface antigenic determinants enhance the specific response of Tc cells to HCV antigen, suggesting that TH cells can assist and enhance Tc. Cell attack destroys HCV-infected hepatocytes.
The E1 and E2/NS of HCV RNA are hypervariable regions, which are easily mutated in vivo and can cause changes in the target antigen (E1, E2/NS protein) of the hepatocyte membrane of HCV-infected patients, and Tc cells will be recognized again. Emerging antigenic determinants and attack damage to liver cells, which is the higher the HCV RNA mutation rate, the more serious the liver tissue inflammation, and the immune-mediated mechanism plays an important role in liver cell damage in chronic HCV-infected patients.
3. Autoimmune HCV infection is often accompanied by the following characteristics:
1 non-specific immune disorders, such as mixed condensed globulinemia, Sjogren's syndrome and thyroiditis.
2 Non-specific autoantibodies, such as rheumatoid factor, anti-nuclear antibody and anti-smooth muscle antibody, can be detected in serum.
3 part of type II autoimmune hepatitis [anti-liver kidney microsomal type I antibody (anti-C-LKM-1 antibody) positive] may be anti-HCV positive.
4 can appear anti-GOR;
5 liver histological changes are similar to autoimmune liver disease, so it is speculated that the pathogenesis of HCV infection may involve autoimmune factors, but the relationship between anti-HCV, anti-LKM-1 and anti-GOR, and its pathogenesis Significance and so on are for further study.
4. Significance of apoptosis in the pathogenesis of hepatitis C Apoptosis is mediated by Fas antigen on the surface of cell membrane. Hiramatsu et al. confirmed that Fas antigen is not expressed in normal liver tissue. When infected with HCV, Fas antigen is more common in Liver tissues with active lesions, especially around the portal area, the expression of Fas antigen in HCV-infected patients is closely related to liver tissue necrosis and inflammation, and the expression of HCV core antigen in hepatocytes, indicating that Fas-mediated apoptosis is HCV. One of the forms of infection with hepatocytes.
The pathogenesis of HCV infection is complex, and many factors and their interrelationships need further study and clarification.
Compared with other types of hepatitis, hepatitis C has its characteristic pathological changes, mainly the following:
1 The cluster of lymphocytes in the portal area and Poulsen-Christoffersen type cholangitis (degeneration of bile duct epithelial cells, surrounded by a large number of lymphocytes) are important features and have diagnostic value.
2 Early cases showed sinusoidal cell infiltration, but did not affect the liver cells around the sinus is the important difference between acute hepatitis B.
3 Hepatocyte necrosis is lighter, the range is limited, and it appears later.
4 sinus and hepatocyte interstitial fibrosis is more obvious than hepatitis B, and appears earlier, which may be one of the reasons for the development of cirrhosis.
5 Hepatocyte steatosis is more common, fat vacuoles can be macrobubble or vesicular.
6 Hepatocyte eosinophilic changes are flaky and appear in the non-inflammatory response zone.
Prevention
Hepatitis C prevention
1. Anti-HCV screening of blood donors is an important measure to reduce hepatitis C after transfusion.
2. Management of infectious sources: according to patients with hepatitis type, use disposable medical supplies; publicize the knowledge of prevention and treatment of hepatitis C, and abide by the disinfection and isolation system.
3. Protection of susceptible population: It has been reported that immunoglobulin is effective in preventing hepatitis C. The usage is 0.06ml/kg, intramuscular injection. The ultimate control of this disease depends on vaccine prevention. HCV molecular cloning is successful, providing vaccine prevention for this disease. The conditions.
Complication
Hepatitis C complications Complications fatty liver cirrhosis
Common complications include arthritis (12% to 27%), glomerulonephritis (26.5%), nodular polyarteritis, etc., using direct immunofluorescence and electron microscopy, found that there are HBV particles on the synovial membrane, serum In patients with membranous glomerulonephritis with persistent HBsAg, HBcAg deposition was found in renal biopsy glomerular tissue. In this hospital, 180 patients with glomerulonephritis were examined by renal biopsy, and 33 patients with HBcAg deposition in the kidney were found. 18.3%), the complex of HBcAg, IgG, IgM, C3 and other immune complexes can be seen on the wall of the diseased tuberculosis. The rare complications are diabetes, fatty liver, aplastic anemia, multiple Neuritis, pleurisy, myocarditis and pericarditis, among which diabetes and fatty liver are worthy of attention, and a small number of patients may have hyperbilirubinemia after hepatitis.
Symptom
C virus hepatitis symptoms Common symptoms Liver pain liver function check bilirubin... Astragalus liver disease diffuse liver capsule tension liver large and hard HBV and HCV...
1. Latency: The incubation period of this disease is 2 to 26 weeks, with an average of 7.4 weeks. The incubation period of hepatitis C caused by blood products is short, generally 7 to 33 days, with an average of 19 days.
2. Clinical experience: clinical manifestations are generally lighter than hepatitis B, mostly subclinical without jaundice, common single ALT is elevated, long-term persistence does not drop or repeated fluctuations, patients with lower mean ALT and serum bilirubin, jaundice The duration is shorter, but it is also more serious, and the clinical difficulty is different from hepatitis B.
Hepatitis C virus infection is more chronic than hepatitis B virus infection. It is observed that about 40% to 50% develop chronic hepatitis, 25% develop cirrhosis, and the rest is self-limiting. Acute hepatitis C develops into chronic Most of them are jaundice-free, ALT long-term fluctuations do not fall, serum anti-HCV continues to be high titer positive, therefore, clinical attention should be paid to observe changes in ALT and anti-HCV.
Although the clinical manifestations of hepatitis C are mild, but severe hepatitis can also occur, HAV, HBV, HCV, HDV and HEV can cause severe hepatitis, but the background and frequency of occurrence are different. The causes of acute, subacute severe hepatitis are: HBV is mostly, and most cases are HCV in Japan. It is speculated that the reason may be that the HCV infection rate in Japanese population is much higher than that in Europe and America, and the HCV genotype in Europe and America is different from that in Japan. Most of the reports were mostly HBV. HCV-induced severe hepatitis was mostly caused by chronic hepatitis B with HCV infection. 3. Viral model. Follow-up study of patients with hepatitis C after transfusion showed that HCV was as follows. Mode:
(1) Acute self-limiting hepatitis with transient viremia.
(2) Acute self-limiting hepatitis with persistent viremia.
(3) persistent viremia but no hepatitis, as a symptomatic carrier of HCV.
(4) Chronic hepatitis C with intermittent viremia.
(5) Chronic hepatitis C with persistent viremia.
4. HBV and HCV overlap infection: Because HCV and HBV have similar transmission routes, the possibility of infecting both viruses is present, but it is more common to infect HCV based on persistent HBV infection. The 302 Hospital of the People's Liberation Army found that the anti-HCV positive rate in the serum of patients with HBsAg-positive chronic liver disease was 0 (0/14) in mild chronic hepatitis (suspended liver); 24.24% (8/33) in chronic active hepatitis; chronic Severe hepatitis was 33.33% (3/9), indicating an increase in the positive rate with the progression and evolution of hepatitis B. It is speculated that the cause may be the increase in the chance of receiving iatrogenic infections such as blood transfusion during the progression of chronic hepatitis B. For the sake of this, on the other hand, there are reports that HBV/HCV overlap infection with severe hepatitis and severe HBV-infected severe hepatitis, two groups of bilirubin, AST/ALT and mortality, there are significant differences, indicating overlapping infection group Hepatocyte necrosis is much more severe than severe hepatitis with HBV infection alone.
It has been observed that HBV DNA and HCV RNA in HBV and HCV overlap cases are only 19% positive, and most of them are HCV RNA or HBV DNA single positive. In addition, almost all HCV RNA positive patients are e antigen negative cases, suggesting that the virus overlaps. The proliferation of infection occurs.
5. HCV infection and hepatocellular carcinoma (HCC): The relationship between HCV infection and HCC is receiving more and more attention. From HCV infection to HCC, the average is about 25 years. It can also be directly developed from chronic hepatitis without cirrhosis. HCC in various countries. The detection rate of anti-HCV is different. The preliminary report in China is 10.96%-59%. Due to the wide heterogeneity of HCV, the occurrence of HCC has a certain relationship with HCV infection of different genotypes. The prevalence of HCV in Japan and the United States The situation is basically similar, but there are more HCCs related to HCV in Japan, but less in the United States. The results show that type II HCV has the characteristics of high level of replication and poor response to interferon therapy, leading to progressive development and canceration of liver diseases. The process may play an important role and provide a molecular epidemiological basis for studying HCV-induced HCC mechanisms.
The mechanism of HCV carcinogenesis is different from that of HBV. It has been shown that HCV is not integrated into the DNA of liver cells like HBV. It is reported that the double infection of HBV and HCV seems to increase the incidence of hepatocellular carcinoma, so HCV should be noted. The role of HBV in carcinogenesis.
6. HCV infection and autoimmune hepatitis (AIH): autoimmune hepatitis is generally classified into four types according to different autoantibodies. Among them, type II AIH refers to anti-nuclear antibody negative and anti-LKM-I positive, recently studied II Type AIH is divided into two subtypes: Type IIa AIH: young people are more common, female-dominated, have familial autoimmune diseases, immunosuppressive therapy has good effect, and has nothing to do with HCV infection, IIb type AIH: mostly elderly, Male, no familial autoimmune disease, antiviral therapy is superior to immunosuppressive agents, associated with HCV infection, anti-HCV positive, anti-GOR positive, such patients should check HCV RNA when necessary.
Examine
Examination of hepatitis C virus
Anti-HCV, HCV-RNA detection clinical significance
1. Anti-HCV
Most HCV-infected patients have anti-HCV in their bodies. Therefore, detection of anti-HCV is valuable for the diagnosis of hepatitis C. Anti-HCV-positive is a sign of HCV infection, but the current test results do not fully reflect acute, chronic or recovery. Infection, antibody titer also does not reflect the intensity of HCV infection, at least not confirmed in animal experiments, anti-HCV positive may indicate the immune status after the recent infection, but most of the current symptoms of HCV infection, and to some extent reflect Individual contagious, human infection HCV logistics work to anti-HCV positive rotation, the length of individual varies greatly during this time, the current method, the antibody is detected later, the only infection in this period of the patient does not appear anti-RNA In addition, 20% of patients with hepatitis C have never developed anti-HCV, so the actual infection rate is higher than the detection rate, and anti-HCV negative can not exclude HCV infection.
Hepatitis C is more clear after transfusion, and there are four manifestations of human reactions after HCV infection:
1 Passive input of high titer anti-HCV positive blood, anti-HCV positive after transfusion, turned negative after 5 weeks, and then appeared anti-HCV autoantibodies, sustainable positive.
2 delayed anti-HCV reaction and continued to be positive, generally 20 to 22 weeks after transfusion or 14 to 16 weeks after the onset of anti-HCV positive conversion, rapid peak, sustained positive more than 10 years.
3 Delayed short-term anti-HCV response, anti-HCV positive conversion after 19 to 21 weeks after transfusion or 9 to 11 weeks after the disease, and negative after 1 year.
4 no response, more common transient HCV infection, anti-HCV is always negative.
The current anti-HCV IgM is different from other viruses in IgM: 1IgM is later than IgG; 2IgM is long, at least 3 to 8 years or longer; 3IgM is positively correlated with IgG titer; 4 is secondary The IgM antibody response indicates that anti-HCV IgM cannot be used as an early diagnostic indicator for HCV infection. It cannot distinguish between recent and previous infections, but may reflect chronic or viral infection, and can be used as an indicator for prognosis and efficacy.
2.HCV-RNA
Due to the low HCV content in the blood of patients with hepatitis C, it is difficult to find HCV-RNA directly by nucleic acid hybridization. It must be determined by nucleic acid amplification and determined by semi-quantitative polymerase chain reaction (HCV cDNA/PCR, abbreviated as cPCR). HCV herbal RNA in liver and serum has the advantages of high specificity, high sensitivity and rapidity. HCV RNA positive is the direct evidence of HCV infection, HCV replication index, infectious, because HCV RNA is earlier than anti-HCV, so It can be used for early diagnosis and screening of blood donors. HCV RNA is negative, indicating that HCV is cleared. Therefore, it can also be used as an indicator to judge prognosis and efficacy.
Diagnosis
Diagnosis and identification of hepatitis C virus
1. Epidemiological history: close contact history (acute hepatitis patients and contaminated items) and blood transfusion or blood product injection history have certain reference value for diagnosis.
2. Laboratory testing
(1) Detection of serum anti-HCV by enzyme-linked immunosorbent assay (ELISA): Various anti-HCV assays have been established using various HCV recombinant proteins in vitro, and the first generation ELISA is 5-1-1 and C-100. Antigen, second-generation ELISA increased C22 and C33 protein, its sensitivity was 10% to 30% higher than that of the first generation. Generally, anti-C22 appeared first and most common, C22 immunogenicity was better, and C type after acute transfusion Hepatitis test showed that anti-HCV was negative in the latent and acute phase, and anti-HCV was positive in 2 to 52 weeks after ALT elevation. A third-generation ELISA was used to detect anti-HCV. This reagent increased NS5 protein. The second generation ELISA is more sensitive.
Due to the late appearance of IgG antibodies, even 1 year after HCV infection, it is not possible to estimate the state of viral replication. Therefore, Quiroga is equivalent to the detection of IgM anti-HCV in 1991, and has been reported in the following. It is currently believed that IgM anti-HCV is acute. The detection rate of hepatitis was slightly higher than that of IgG antibody (64% for IgM anti-HCV and 57% for IgG anti-HCV). In self-limiting cases, IgM anti-HCV disappeared, but still positive in chronic cases. It suggests that IgM anti-HCV can be used as an indicator of evolution to chronicity and has certain value for guiding antiviral therapy.
(2) Recombinant immunoblotting (RIBA) detection of HCV antibodies: The first generation of ELISA was established shortly. To exclude ELISA for anti-C100 false positives, Chiron provided an immunoblot test for confirmatory testing, also known as the first generation RIBA. The specificity of RIBA is higher than that of ELISA, but the sensitivity is significantly reduced. At present, the second generation and third generation RIBA have been established, and the positive rate is significantly higher than that of the first generation RIBA.
(3) Detection of HCV antigen: Krawczynski et al. extracted IgG fraction from HCV-infected chimpanzee or patient serum, labeled with fluorescein isothiocyanate as a probe, and detected HCV antigen in liver tissue by direct immunofluorescence. Four acute and three chronic hepatitis C chimpanzee liver tissues were detected, and HCV antigens were positive. The blocking test and adsorption test demonstrated that HCV antigen in hepatocytes is associated with viral hepatitis caused by HCV, which is HCV-infected. A specific morphological marker that can be used as one of the laboratory diagnostic methods for HCV infection. In addition, immunohistochemical ABC method can be used to detect HCV antigen in liver tissue.
(4) Detection of HCV RNA: HCV infection, serum virus content is extremely low, it is difficult to detect HCV RNA by conventional molecular hybridization technology, PCR technology is currently the most sensitive detection technology in the field of molecular biology, has been used In the detection of HCV RNA, this method is the most reliable indicator for determining whether or not HCV infection is contagious. It has good specificity and high sensitivity, which is conducive to the early diagnosis and evaluation of HCV infection, but it should also be noted that due to high sensitivity, operation The process is complicated, and it is easy to pollute and cause false positives.
3. Liver biopsy light microscopy and electron microscopy have certain reference value.
The disease should be associated with elevated levels of serum transaminases or serum bilirubin caused by toxic hepatitis, cholecystitis, infectious mononucleosis, leptospirosis, epidemic hemorrhagic fever, fatty liver, and amoebic liver disease. Identification, cholestatic hepatitis should be differentiated from extrahepatic obstructive jaundice (such as pancreatic head cancer, cholelithiasis, etc.).
