Effects of interferon and adenine arabinoside treatment of hepatitis B virus infection on cellular immune responses

Immunological studies before and during interferon therapy in chronic HBV infection: identification of factors predicting response

Lymphoblastoid interferon is effective therapy in some but not all patients with chronic hepatitis B virus infection. To assess whether immunological parameters were predictive of response to interferon therapy, we determined the human leukocyte antigen type, CD4/CD8 ratio, natural killer cell activity, IgM anti-HBc antibody levels and concanavalin A-induced lymphocyte proliferative response in 30 patients before treatment. In addition, to investigate the mechanisms of action of interferon in promoting hepatitis B virus clearance, we serially measured the CD4/CD8 ratios, natural killer activity and lymphocyte proliferative response at wk 4, 8 and 12 of treatment. A beneficial response to therapy was defined as the sustained clearance of HBeAg and serum hepatitis B virus DNA within 1 yr of commencing therapy. Elevated IgM anti-HBc levels were associated with a beneficial response to therapy, but there was no correlation observed between response and pretreatment CD4/CD8 ratio, natural killer activity or lymphocyte proliferative response. Six of seven human leukocyte antigen DR3-positive patients responded. No measurable changes in the immunological parameters studied were observed in the nonresponder group, whereas a significant rise in CD4/CD8 ratio, associated with a fall in peripheral CD8 number and a decline in measurable NK activity, was seen in the responder group. These changes were maximal at the time of hepatitis B virus DNA clearance, which was associated with a transient increase in hepatic inflammation.(ABSTRACT TRUNCATED AT 250 WORDS)

Inhibition of hepatitis B virus replication by vidarabine monophosphate conjugated with lactosaminated serum albumin

Vidarabine (ara A) produces severe dose-dependent side-effects. To examine whether its monophosphate ester (ara-AMP) can be effective in the treatment of chronic hepatitis B when given in reduced dosage as a conjugate with lactosaminated human serum albumin (L-HSA), which selectively enters hepatocytes, five patients with chronic type B hepatitis (HBsAg/HBV-DNA positive for at least 2 years) were treated with the conjugate. The daily dose of conjugate given (35 mg/kg) contains 1.5 mg ara-AMP, whereas the usual daily dose of free ara-AMP is 5-10 mg/kg. In three patients HBV-DNA fell to undetectable levels and remained negative in two; in one of them anti-HBe developed. In the other two patients HBV-DNA decreased but was detectable during treatment--one received three cycles of therapy, and became HBV-DNA negative and anti-HBe positive 45 days after the end of treatment; the other remained HBeAg/HBV-DNA positive. No adverse effects were observed, and biochemical variables (including aminotransferases) remained unchanged or decreased with viraemia. No antibodies (IgM and IgG classes) that bound the conjugate were detected. Thus L-HSA-ara-AMP inhibits HBV replication as well as free ara-AMP but at a third to a sixth of the dose.

Effects of adenine arabinoside on serum and intrahepatic replicative forms of duck hepatitis B virus in chronic infection

Adenine arabinoside is an antiviral agent which has been used in a number of clinical studies for the treatment of chronic infections with hepatitis B virus. In order to better understand its effects and mode of action, we treated ducks chronically infected with duck hepatitis B virus with a 2-week course and monitored the effects of the drug on viral replication by studying duck hepatitis B virus DNA in liver and serum using molecular biological techniques. We found the drug to be effective in ducks only at much higher doses than those used in humans. At high doses, adenine arabinoside had a dose-related inhibitory effect on viral replication during treatment, but there was a rapid return toward baseline values soon after the cessation of treatment. The supercoiled form of viral DNA was found to be most resistant to adenine arabinoside therapy, and the drug had a disproportionate inhibitory effect on viral plus (noncoding) strand synthesis. We conclude that adenine arabinoside likely exerts its effect in hepadna virus infections predominantly through inhibition of viral DNA polymerase. On the basis of our current study and previous trials in hepatitis B virus-infected patients, we predict that adenine arabinoside will not efficiently eliminate viral replication in chronic hepadna virus infection, when used as the sole therapeutic modality. Adenine arabinoside may have a role to play as an adjunct to immunomodulation or interferon therapy in chronic hepatitis B virus infection in man.

Effects of adenine arabinoside on cellular immune responses in patients with chronic hepatitis B

The lymphocyte subsets in the peripheral blood and in liver biopsies from 4 patients with chronic hepatitis B obtained about 2-7 weeks before and after treatment with adenine arabinoside (Ara-A) were studied by a peroxidase-labeled antibody method using monoclonal antibodies against Leu-1, Leu-2a, Leu-3a, Leu-7 and Leu-10 antigens. In the peripheral blood, the percentage of Leu-2a+ (cytotoxic/suppressor) cells was significantly reduced and the ratio of Leu-3a+ (helper/inducer) to Leu-2a+ cells was increased after the treatment with Ara-A. In the liver biopsies, the numbers of Leu-1+ (pan T) and Leu-2a+ cells were significantly decreased after the treatment with Ara-A. As a result, the Leu-3a+/Leu-2a+ ratio was significantly elevated in the liver after the therapy. The majority of lymphocytes distributed at sites of hepatocytic necrosis were positive for Leu-2a. The reduced numbers of Leu-1+ and Leu-2a+ cells after the treatment were mainly due to the decrease of these cells infiltrating to the sites of hepatocytic necrosis. The numbers of other subsets (Leu-3a+, Leu-7+ and Leu-10+) changed without any specific tendency both in the peripheral blood and in the liver biopsies after the treatment. With respect to viral replication, most of the patients showed a decrease of serum DNA polymerase activity or demonstrable intrahepatic HBsAg and HBcAg after the treatment. These data suggest that T cell-mediated cytotoxicity against HBV-infected hepatocytes is diminished after treatment with Ara-A.

Drug targeting in antiviral chemotherapy. A chemically stable conjugate of 9-beta-D-arabinofuranosyl-adenine 5'-monophosphate with lactosaminated albumin accomplishes a selective delivery of the drug to liver cells

With the aim of improving the chemotherapeutic index of 9-beta-D-arabinofuranosyl-adenine 5' monophosphate (ara-AMP) in the treatment of chronic hepatitis B, this drug was conjugated with lactosaminated serum albumin (L-SA), a neoglycoprotein which only enters into hepatocytes. We used a L-SA-ara-AMP conjugate which, in contrast to those previously employed, has the advantage of remaining soluble after lyophilization. We found in mice that: (I) this new conjugate was quite stable in the bloodstream where only a small part of ara-AMP was released; (II) after administration of the conjugate labelled in the drug moiety both acid insoluble and soluble radioactivities were several times higher in liver than in other organs; (III) in mice with Ectromelia virus hepatitis, the conjugate inhibited virus DNA synthesis in liver without affecting cellular DNA synthesis in intestine and bone marrow; (IV) the conjugate did not display any recognizable sign of acute toxicity even at doses several fold higher than those pharmacologically active; and (V) when prepared with homologous albumin it was not immunogenic.

Clinicopathological response of HBsAg-positive chronic active hepatitis to adenine arabinoside: lack of correlation with DNA polymerase response

Fifteen patients with HBsAg-positive, severe chronic active hepatitis, nine DNA polymerase (DNAP)-positive and six negative were treated with intravenous adenine arabinoside (Ara-A) in a dose of 10 mg/kg/day for five consecutive days during each of two consecutive weeks. Of the DNAP-positive patients, two responded with histological and clinical remission as well as permanent loss of DNAP. However, histological and clinical remission were also observed in patients with unsatisfactory DNAP response and even in DNAP-negative patients. It is suggested that, in addition to its antiviral effect, Ara-A might have another mechanism, such as immunosuppression, that induced histological and clinical remission. Alternatively, the discrepancy of response might relate to the natural course of chronic type B hepatitis. Accordingly, controlled trial is mandatory for assessing the effect of Ara-A or any other agent in the treatment of chronic type B hepatitis.

Effect of prolonged administration of interferon-alpha on pharmacokinetics, fever, lymphocyte proliferative response, and NK cell activity

Over a 60-week period, a patient with multiple warts received a total of 281 x 10(6) units of human leukocyte interferon (IFN-alpha) by intramuscular (IM) or intralesional (IL) injections. Circulating IFN was significantly higher following IM administration than after IL administration. These pharmacokinetics did not change. The patient's body temperature was always significantly elevated after administration of IFN. However, hyporeactivity to the febrile response developed when the interval between repeated injections of IFN was less than six days. The lymphocyte count was significantly decreased within 5-7 h after administration of IFN and had returned to normal by 24 hours, whereas total WBC, platelet, and monocyte counts were not altered. There was a depression of specific lymphocyte proliferative response to herpes simplex virus after multiple daily injections, but not after prolonged therapy. Circulating natural killer (NK) levels were not elevated during the first two months of IFN therapy. After the patient had received about 100 x 10(6) units of IFN, however, the NK cell level became elevated and remained elevated upon cessation of treatment. NK activity was stimulated by in vitro incubation of peripheral mononuclear cells with 1000 units of IFN during the initial phase of treatment. A decline of in vitro stimulation of NK activity by interferon developed during two subsequent periods of treatment with mean daily doses of 2.46 and 1.07 x 10(6) units of IFN. Long-term therapy in our patient with an average of 4.7 x 10(6) units of IFN/week was well tolerated, did not irreversibly affect platelet or white cell counts or nonspecific or virus-specific cell mediated immune responses, and enhanced circulating NK levels.

Inactivation of S-adenosylhomocysteine hydrolase during adenine arabinoside therapy

To assess for possible inhibition of cellular transmethylation during adenine arabinoside (ara-A) therapy, S-adenosylhomocysteine hydrolase activity was analyzed in 10 patients with chronic hepatitis B virus infection. In six patients receiving ara-A, enzyme activity was suppressed to 0-2% of control erythrocyte enzyme activity. This decrease in enzyme activity was evident within 4 h of starting the drug infusion and continued for 7 d after cessation of therapy. S-adenosylhomocysteine hydrolase activity of peripheral mononuclear cells was also measured in two patients receiving ara-A. Suppression to as low as 3.5% of pretreatment levels was found; however, marked fluctuations with partial return of enzyme activity during therapy was also observed in mononuclear cells. Inhibition of an enzyme involved in transmethylation reactions was observed in patients during ara-A therapy. This could contribute to the side effects and antiviral properties of ara-A.

Proposed explanation for S-adenosylhomocysteine hydrolase deficiency in purine nucleoside phosphorylase and hypoxanthine-guanine phosphoribosyltransferase-deficient patients

We have examined the basis for the recently reported, but unexplained deficiency of S-adenosylhomocysteine hydrolase (AdoHcyase) in the erythrocytes of patients with genetic deficiencies of purine nucleoside phosphorylase and hypoxanthine-guanine phosphoribosyltransferase. We found that a hemolysate from a patient with purine nucleoside phosphorylase deficiency had only 7% of control AdoHcyase activity, conforming the original observation. Of the purine nucleosides known to accumulate in nucleoside phosphorylase-deficient patients, inosine alone caused the phosphate-dependent, irreversible inactivation of purified human placental AdoHcyase, and of AdoHcyase in intact erythrocytes and cultured lymphoblastoid cells. Hypoxanthine did not inactivate purified AdoHcyase, but potentiated the effect of inosine in intact hypoxanthine-guanine phosphoribosyltransferase-deficient human lymphoblastoid cells. This presumably resulted from the ability of hypoxanthine to shift the equilibrium of the nucleoside phosphorylase reaction, preventing inosine breakdown. This could account for the partial AdoHcyase deficiency reported in hypoxanthine-guanine phosphoribosyltransferase-deficient patients. We have also demonstrated the AdoHycase-catalyzed synthesis of S-inosylhomocysteine from inosine and L-homocysteine, a reaction which may occur in nucleoside phosphorylase-deficient patients.

Effect of interferon therapy on circulating lymphocytes in humans

The effect of interferon treatment on both lymphocyte subpopulation numbers and function was studied in two groups of patients who were being treated systemically with 0.5 to 1.0 x 10(7) units of human leukocyte-derived interferon (HulFN-alpha) daily. Patients with nodular lymphocytic, poorly differentiated non-Hodgkin's lymphoma (NLPD) were given interferon for 30 days and those with chronic hepatitis B infection were treated in cycles for 4 to 7 days. In both patient groups, B lymphocytes numbers were reduced during treatment, but T lymphocyte numbers were unaffected. T lymphocyte responses, measured by blast transformation to herpesvirus antigens were generally low before treatment in NLPD patients. The responses were restored after termination of therapy. In two NLPD patients given two courses of treatment separated by a 3 month interval, the restored T lymphocyte responses were inhibited during the second course of treatment. In patients with chronic hepatitis B virus infection, lymphocyte blast transformation to the viral antigens were also depressed during treatment compared to pretreatment responses. Changes in lymphocyte responses to phytohemagglutinin and pokeweed mitogen were not observed in either patient group.