Chronic Viral Infections

The current issue of Viral Immunology features several articles on persistent viral infections. The issue opens with an interesting review article on the role of CCR5 during hepatitis B virus (HBV) infection. HBV can establish a persistent infection in the liver and lead to chronic liver diseases, such as cirrhosis or cancer. The World Health Organization estimates that 400 million people are infected with HBV worldwide, posing a global health crisis. From a research standpoint, it is critical to determine why many HBV-infected patients are unable to eradicate HBV from the liver. In this regard, the review by Sanchooli and colleagues addresses the role of CC chemokines (RANTES, MIP-1α, and MIP-1β) which act through CC chemokine receptor 5 (CCR5) on disease progression. Importantly, recent information regarding the status of CCR5 expression on the immune cells and the association of CCR5 promoter polymorphisms with HBV infected patients is discussed.

Another persistent virus infection is hepatitis C virus (HCV). The number of patients with detectable HCV infection has been increasing over the last 20 years to more than 185 million people worldwide. Serological screening is an important tool to counter the HCV endemic since the identification of silent infections can help reduce transmission. While HCV tests have improved over the years, a significant number of test results yield borderline signal-to-cut-off ratios and inconclusive data, resulting in time-consuming and expensive re-testing by immunoblot assays or real-time PCR. To further investigate this issue, Maasoumy and colleagues compared the concordance and performance of four licensed anti-HCV detection tests during routine clinical practice at a tertiary referral and transplant center. The data indicate that there were significant differences between the assays in classifying samples with low signal-to-cut-off ratios. The differential performance of these assays may have cost and management implications, as false-positive results were not infrequent.

The current issue also includes a pilot study on the relationship between plasmacytoid dendritic cells (pDCs), regulatory T-cells (Tregs), and human papillomavirus (HPV) persistence in women that were either infected, or uninfected, with human immunodeficiency virus (HIV). In their study, Strickler et al. point out that, although pDCs and Tregs may impact HIV pathogenesis and disease progression, their role in the control of HPV, the viral cause of cervical cancer, has not been carefully studied. Here they report for the first time that low pDC and high Treg levels may be significantly associated with HPV persistence in both HIV-positive and HIV-negative women, and suggest that larger studies are now warranted to investigate this relationship further.

Finally, the issue contains an article on swine influenza virus (SIV). SIV causes an acute respiratory disease in pigs and is responsible for regular outbreaks on hog farms. The disease poses a major economic problem for the swine industry throughout the world and also poses threats to the human population. Commercial vaccines, based on inactivated viruses, do not provide complete protection and require regular reformulation to protect against current SIV isolates. Therefore, there is a need to develop new and more effective vaccines. Wei and colleagues have begun to address this issue by developing a DNA epitope-based vaccine. The vaccine includes a B-cell epitope and multiple murine CD4⁺ and CD8⁺ T cell epitopes in a pcDNA3.1 plasmid. Intramuscular administration of the vaccine to mice was protective against a lethal challenge with swine influenza A virus H1N1. While these data are very preliminary, they provide hope that new vaccines against this pathogen can be developed.

The research papers presented in this issue of Viral Immunology highlight important advances in our understanding of persistent viral infections, assays, and vaccine development. I would like to thank the authors for their important contributions.