Gamma Delta T Cells

Gamma delta T cells (γδ T cells) are distinguished from alpha beta (αβ) T cells by their expression of a distinct T-cell receptor (TCR). They are present in the blood and tissues at lower frequencies than αβ T cells, and the antigens that activate them are largely unknown, although they include some lipid antigens and heat shock proteins. Importantly, the roles that γδ T cells play in the context of different viral infections remain to be determined. In the current issue of Viral Immunology, Conroy and colleagues explore the role of γδ T cells in asymptomatic hepatitis B virus (HBV) carriers by measuring the relative frequencies, surface phenotypes, and cytokine production of circulating γδ T cell subsets. The authors report that γδ T cells expressing Vδ1 and Vδ2 TCR and effector-memory phenotypes are expanded in these patients compared to healthy controls, and that Vδ2+ cells express interferon-γ (IFNγ) more frequently. Based on these findings, the authors suggest that effector-memory IFN-γ-producing Vδ2 T cells may contribute to control of HBV in patients with asymptomatic infection, without mediating liver pathology. Since Vδ2 T cells have already been identified as targets for immunotherapy, and they are already the focus of several clinical trials, the authors propose that they might be used as the basis for future immunotherapies to treat HBV patients with persistent symptomatic infection.

Two additional articles in this issue of Viral Immunology also investigate the immune response to HBV. Shaha and colleagues note that although the development of protective antibody to hepatitis B surface antigen (anti-HBs) is a common phenomenon after vaccination as well as natural infection, it isn't always induced by vaccination. Therefore, they investigated whether the impairment of anti-HB development in naturally infected or vaccinated individuals is associated with various risk factors (including age, gender, smoking, and diabetes) through a cross-sectional study. Their data demonstrate that anti-HB development is significantly lower in smokers and emphasize the necessity of checking the anti-HB status in smokers after vaccination. Ming et al. investigate the association between transforming growth factor-β1 (TGF-β1), interleukin-31 (IL-31), and disease severity of hepatitis B virus–related liver cirrhosis. The authors show that TGF-β1 and IL-31 are linked to progression from chronic hepatitis to hepatitis B virus–related liver cirrhosis, and correlated well with the severity of cirrhosis. These findings suggest possible roles of the TGF-β1/IL-31 pathway in the pathogenesis of liver fibrosis during chronic HBV infection.

Another virus that attacks the liver is hepatitis C virus (HCV). HCV has infected approximately 300 million individuals worldwide and poses significant health problems due to the fact that it causes chronic liver diseases, such as liver cirrhosis and hepato-cellular carcinoma. Azam and colleagues investigated the role of tumor necrosis factor–related apoptosis-inducing ligand receptor 1 (TRAIL-R1) and IFN-γ genetic mutations in the susceptibility and response to interferon-based therapy of HCV infection. The authors conclude that genetic variation of TRAIL-R1 is linked with response to interferon-based therapy of HCV infection, and genetic variation of IFN-γ is associated with natural clearance of HCV infection.

Several other articles in this issue of Viral Immunology address aspects of immunity to a number of different viruses in both human and animal. Papatsiros et al. have evaluated the effects of porcine reproductive and respiratory syndrome virus (PRRSV) vaccine on the reproductive systems of vaccinated and nonvaccinated pigs. The data indicate that PRRSV vaccination of 288 breeding stock with an inactivated vaccine had positive effects on their reproductive system. Specifically, PRRSV vaccination was linked with a reduction in the occurrence of cyst formation in the ovaries. Zhang et al. have investigated the role of CD163, a hemoglobin scavenger receptor that is expressed by monocytes and macrophages and is often shed in soluble form (sCD163), in the pathogenesis of hemorrhagic fever with renal syndrome. The study highlights a correlation between plasma sCD163 and renal dysfunction that suggests that sCD163 may play an important role in the development of acute renal failure in patients infected with Hantaan virus.

Doan et al. have examined the expression patterns of immune-associated genes in external genital and perianal warts treated with sinecatechins. Their data indicate that sinecatechins dampen both the immune response and inflammatory signaling with a concomitant activation of apoptosis and promoting the clearance of external genital and perianal warts. Barjesteh and colleagues have used an in ovo model to study the antiviral activities of TLR ligands against avian influenza virus in embryonated chicken eggs. The study demonstrated that the in ovo route is useful to determine the antiviral characteristics of TLR ligands against avian influenza virus.

Finally, I would like to thank all of the authors for their exceptional contributions to the journal and all of the reviewers for their help in ensuring that only high-quality articles are published.