Why are T cells tolerant to hepatitis B virus?

The level of PD-1 expression has been proved by recent studies to be positively correlated with the extent of HBV-specific T cell impairments. However, the degree of T cell exhaustion which affects the disease statuses of hepatitis B patients has so far been only evaluated in restricted and small groups of patients between those with established chronicity and subjects with acute HBV infection. Besides, whether levels of PD-1 expression on T cells differ between acute exacerbation of hepatitis B and chronic HBV infected patients is still unknown.

A research article to be published on July 28, 2008 in the World Journal of Gastroenterology addresses this question. The research team led by Shu-Ling Zhang from Tongji Medical College of Huazhong University of Science and Technology in China examined the expression of PD-1 on antigen specific CD8+ T cells in peripheral blood of chronic hepatitis B (CHB) and acute exacerbation of hepatitis B (AEHB) patients.

They found that the levels of PD-1 on total CD8+ T cells in CHB patients were significantly higher than those in AEHB patients and healthy individuals. Conversely, lower frequencies of HBV-specific CD8+ T cells were detected in samples from chronic patients compared to AEHB patients. Our results confirmed reports that HBV specific CD8+ T-cell responses in peripheral blood were intensified in samples from AEHB patients than in those from patients with chronic hepatitis who remains viral persistence. Besides, there was a significant positive correlation between HBV viral load and percentage of PD-1 expression on CD8+ T cells in CHB and AEHB group of subjects. However, PD-1 expression was not in association with disease flare-ups indicator alanine aminotransferase (ALT). This study clarified the correlation between PD-1 expression and two different HBV infection statuses.

Reference: Ye P, Weng ZH, Zhang SL, Zhang JA, Zhao L, Dong JH, Jie SH, Pang R, Wei RH. PD-1 expression is associated with the disease statuses of hepatitis B virus infection. World J Gastroenterol 2008; 14(28): 4551-4557 http://www.wjgnet.com/1007-9327/14/4551.asp

Correspondence to: Shu-Ling Zhang, Department of hepatology and infectious disease, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan 430022, Hubei Province, China. yp_breezy@yahoo.com.cn Telephone: +86-27-62629209 Fax: +86-27-85756636

World Journal of Gastroenterology (WJG), a leading international journal in gastroenterology and hepatology, has established a reputation for publishing first class research on esophageal cancer, gastric cancer, liver cancer, viral hepatitis, colorectal cancer, and H pylori infection and provides a forum for both clinicians and scientists. WJG has been indexed and abstracted in Current Contents/Clinical Medicine, Science Citation Index Expanded (also known as SciSearch) and Journal Citation Reports/Science Edition, Index Medicus, MEDLINE and PubMed, Chemical Abstracts, EMBASE/Excerpta Medica, Abstracts Journals, Nature Clinical Practice Gastroenterology and Hepatology, CAB Abstracts and Global Health. ISI JCR 2003-2000 IF: 3.318, 2.532, 1.445 and 0.993. WJG is a weekly journal published by WJG Press. The publication dates are the 7th, 14th, 21st, and 28th day of every month. WJG is supported by The National Natural Science Foundation of China, No. 30224801 and No. 30424812, and was founded with the name of China National Journal of New Gastroenterology on October 1, 1995, and renamed WJG on January 25, 1998.

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