Let it B in viral hepatitis?

Subversion of the B-cell compartment during parasitic, bacterial, and viral infections

Recent studies on HIV infection have identified new human B-cell subsets with a potentially important impact on anti-viral immunity. Current work highlights the occurrence of similar B-cell alterations in other viral, bacterial, and parasitic infections, suggesting that common strategies have been developed by pathogens to counteract protective immunity. For this review, we have selected key examples of human infections for which B-cell alterations have been described, to highlight the similarities and differences in the immune responses to a variety of pathogens. We believe that further comparisons between these models will lead to critical progress in the understanding of B-cell mechanisms and will open new target avenues for therapeutic interventions.

Low prevalence of hepatitis B virus infection in patients with autoimmune diseases in a Chinese patient population

Hepatitis B is a very common communicable disease in China but the prevalence of hepatitis B virus (HBV) infection in patients with autoimmune diseases is unknown. We retrospectively investigated the prevalence of autoimmune diseases in patients with HBV infection. The medical records of 4060 patients with autoimmune or nonautoimmune diseases were reviewed. A positive test result for hepatitis B surface antigen (HBsAg) was used to indicate the presence of HBV infection. Autoimmune diseases included autoimmune hepatitis, primary biliary cirrhosis, systemic lupus erythematosus and ulcerative colitis. Nonautoimmune conditions included inguinal hernia, appendicitis and pregnant or postpartum women. The proportion of autoimmune disease patients who were HBsAg positive (2.24%) was significantly lower than that of nonautoimmune disease patients who were HBsAg positive (4.58%; P = 0.0014). Regarding hepatic autoimmune diseases, the positivity rates for HBsAg in autoimmune hepatitis patients (0.83%) and primary biliary cirrhosis patients (1.02%) were both significantly lower than in nonautoimmune patients (4.58%; P = 0.006 and 0.004, respectively). Patients with hepatic autoimmune disease were significantly less likely to be HBsAg positive (0.93%) than patients with non-hepatic autoimmune disease (3.99%; P = 0.002). Patients with autoimmune diseases, especially those with hepatic autoimmune disease, may more efficiently clear HBV than patients with nonautoimmune diseases.

Direct role of antibody-secreting B cells in the severity of chronic hepatitis B

Chronic hepatitis B involves different immune cells. The direct role of antibody-secreting B cells in the severity of chronic hepatitis B unclear. In this study, the number of plaque forming cells [PFC-(IgG, IgM, anti-HBc IgG, and anti-HBc IgM)], liver function tests (LFT) [alkaline phosphatase (ALP), alanine aminotransferase (ALT), and total serum bilirubin (TSB)], the levels of IL-10 in sera and in lymphocyte cultures, the number of CD4(+) and CD8(+) cells were measured in the peripheral blood of patients and in the controls. In addition, the hepatocytotoxic effect of anti-HBc and anti-HBe in vitro was studied. The largest number of PFCs was observed in the peripheral blood of patients with chronic hepatitis B. This was concomitant with a decrease in CD4(+) /CD8(+) ratio versus this ratio in asymptomatic HBV carriers and in healthy volunteers (P < 0.05). An increase in immunoglobulin (IgG and IgM) levels, anti-HBc IgG, and anti-HBc IgM levels and LFTs in peripheral blood of patients with chronic hepatitis B was seen. Anti-HBc induced hepatocytotoxicity in vitro. The expression of mRNA and protein for IL-10 production was observed at a significant level in culture of lymphocytes isolated from patients with chronic hepatitis B. In addition, a high level of IL-10 was found only in the sera of patients with chronic hepatitis B. It is concluded that the antibody-secreting B cells and the antibodies, which are produced, play an important role in the severity of chronic hepatitis B, which was related negatively with CD4(+) /CD8(+) ratio and positively with IL-10 expression.

Hepatitis B specific T cell immunity induced by primary vaccination persists independently of the protective serum antibody level

In 2005, in accordance with recommendations made by the European Medicines Agency, the Italian Drug Agency ordered withdrawal of the hexavalent Hexavac(®) vaccine (Sanofi Pasteur MSD) from the market. Concerns had been raised about the low immunogenicity of the hepatitis B virus component of the vaccine, assessed by measurement of serum antibody levels, and its potential consequences on long-term protection against hepatitis B infection. We evaluated memory T cell response to establish whether there are differences in the protective mechanisms among children who had received either Hexavac(®) or Infanrix-hexa(®) (GlaxoSmithKline) as their primary vaccination. Immunological memory was determined by measuring the ability of T cells to proliferate and secrete IFNγ by ELISA and intracellular cytokines (IFNγ and IL-2) when cultured with hepatitis B surface antigen (HBsAg). The different memory subsets of T cells were also measured. The results indicate that, although they generate different serum antibody levels, both vaccines are efficient in generating T recall responses in vitro five years after the primary vaccination. The less immunogenic Hexavac(®) vaccine induces a strong T antigen response, as indicated by increased blast proliferation and the enhanced presence of memory subsets after HBsAg recall stimulation. These findings suggest that cellular immune response should be considered alongside serological markers as a surrogate of protection.

B cell homeostasis in chronic hepatitis C virus-related mixed cryoglobulinemia is maintained through naïve B cell apoptosis

Mixed cryoglobulinemia (MC) is the most common extrahepatic manifestation of chronic hepatitis C virus (HCV) infection. Although the formation of inflammation-triggering immune complexes is driven by clonal expansions of autoreactive B cells, we found total B cell numbers paradoxically reduced in HCV-infected patients with MC. HCV patients with MC (n = 17) also displayed a reduced number and a reduced frequency of naïve B cells compared with HCV-infected patients without MC (n = 19), hepatitis B virus-infected patients (n = 10), and uninfected controls (n = 50). This was due to an increased sensitivity of naïve B cells to apoptosis resulting in a reduction in the size of the naïve B cell subset. In addition, 4-fold expansion and skewing (lower T1/T2-ratio) of the immature B cell subset was noted in MC patients, suggesting that apoptosis of naïve B cells triggered the release of B cell precursors from bone marrow in an attempt to maintain normal B cell numbers. Following treatment of MC with the B cell-depleting antibody rituximab, the size of all B cell subsets, the T1/T2-ratio, and the cyroglobulin levels all normalized. Cryoglobulin levels correlated with in vivo proliferation of T2 B cells, suggesting a link between the skewing of the T1/T2 ratio and the formation of immune complexes.

CONCLUSION

This study provides insight into the mechanisms maintaining B cell homeostasis in HCV-induced MC and the ability of rituximab therapy to restore normal B cell compartments. (HEPATOLOGY 2012;56:1602-1610).

Hepatitis B precore protein: pathogenic potential and therapeutic promise

Hepatitis B virus (HBV), a small and economically packaged double-stranded DNA virus, represents an enormous global health care burden. In spite of an effective vaccine, HBV is endemic in many countries. Chronic hepatitis B (CHB) results in the development of significant clinical outcomes such as liver disease and hepatocellular carcinoma (HCC), which are associated with high mortality rates. HBV is a non-cytopathic virus, with the host's immune response responsible for the associated liver damage. Indeed, HBV appears to be a master of manipulating and modulating the immune response to achieve persistent and chronic infection. The HBV precore protein or hepatitis B e antigen (HBeAg) is a key viral protein involved in these processes, for instance though the down-regulation of the innate immune response. The development of new therapies that target viral proteins, such as HBeAg, which regulates of the immune system, may offer a new wave of potential therapeutics to circumvent progression to CHB and liver disease.