From DCPD to NTCP: The long journey towards identifying a functional hepatitis B virus receptor

Hepatitis B virus (HBV) is the prototype of hepatotropic DNA viruses (hepadnaviruses) infecting a wide range of human and non-human hosts. Previous studies with duck hepatitis B virus (DHBV) identified duck carboxypeptidase D (dCPD) as a host specific binding partner for full-length large envelope protein, and p120 as a binding partner for several truncated versions of the large envelope protein. p120 is the P protein of duck glycine decarboxylase (dGLDC) with restricted expression in DHBV infectible tissues. Several lines of evidence suggest the importance of dCPD, and especially p120, in productive DHBV infection, although neither dCPD nor p120 cDNA could confer susceptibility to DHBV infection in any cell line. Recently, sodium taurocholate cotransporting polypeptide (NTCP) has been identified as a binding partner for the N-terminus of HBV large envelope protein. Importantly, knock down and reconstitution experiments unequivocally demonstrated that NTCP is both necessary and sufficient for in vitro infection by HBV and hepatitis delta virus (HDV), an RNA virus using HBV envelope proteins for its transmission. What remains unclear is whether NTCP is the major HBV receptor in vivo. The fact that some HBV patients are homozygous with an NTCP mutation known to abolish its receptor function suggests the existence of NTCP-independent pathways of HBV entry. Also, NTCP very likely mediates just one step of the HBV entry process, with additional co-factors for productive HBV infection still to be discovered. NTCP offers a novel therapeutic target for the control of chronic HBV infection.

High rate of mutation K103N causing resistance to nevirapine in Indian children with acquired immunodeficiency syndrome.

In north India the number of paediatric cases with acquired immunodeficiency syndrome (AIDS) is on the rise. Most drug combinations used for treatment of AIDS incorporate nevirapine, resistance to which develops very fast if given singly or because of unplanned interruptions. This paper investigates presence of mutations at codon 103 and codon 215 of the HIV pol gene causing resistance to nevirapine and zidovudine (AZT) respectively in 25 children with AIDS. Mutations T215Y and K103N were detected by a nested cum amplification refractory mutation system polymerase chain reaction (ARMS PCR) and the results were confirmed by direct sequencing in five randomly selected cases. Nineteen patients had received nevirapine containing regimen and six were drug naive. Mutation K103N was observed in 56% (14/25) of the children while mutation T215Y was found in none. Two of the six drug naïve children also showed K103N mutation. Thus, Indian children drug naïve or treated with nevirapine containing regimens show a high rate of mutation conferring resistance to nevirapine which calls for a judicious use of nevirapine both in antenatal and postnatal setting.

Natural YMDD Motif Mutations of HBV Polymerase in the Chronic Hepatitis B Virus Infected Patients / 대한간학회지

BACKGROUND/AIMS: Lamivudine, a nucleoside analogue has been widely used as an effective antiviral agent for the treatment of patients with chronic hepatitis B infection. However, the YMDD motif mutation of HBV polymerase resistant to lamivudine very frequently occurs after long-term use of lamivudine. It is well known that the mutation is selected by the lamivudine. We hypothesized that a few mutant strains of YMDD motif are present as quasispacies before the lamivudine treatment, are selected by the treatment, and breakthrough during treatment. We investigated the prevalence of the YMDD motif mutants in patients with chronic hepatitis B infection who had not been treated by antiviral agents before. METHODS: The study included the serums of 40 patients with chronic heptitis B infection, which stored at -70 degrees C. Thirty-four patients had chronic hepatitis and 6 patients had cirrhosis. Thirty-one patients were diagnosed by liver biopsy. The average age and range were 29 years and 13-57 years respectively. None had taken any antiviral agents before. To detect YMDD mutants, YVDD (M552V), and YIDD (M552I), we used direct sequencing and the restriction fragment length polymorphism (RFLP) method. RESULTS: The YMDD mutant was detected by RFLP method in 7.5% (3/40) of the patients with chronic hepatitis B infection, in two patients with chronic hepatitis and one with cirrhosis. All were YMDD+ YIDD mutants. CONCLUSIONS: The YMDD motif mutation occurs spontaneously without antiviral therapy in patients with chronic hepatitis B infection.

Adult T cell leukemia/lymphoma with lymphopenia in a Korean

We experienced a case of adult T cell leukemia/lymphoma (ATLL) in a 48-year-old Korean female, who has never been abroad since birth and no history of blood transfusion. The patient had hypercalcemia and multiple lymphadenopathy. Histopathologic study of left cervical lymph node (LN) and bone marrow (BM) revealed that infiltrates of malignant lymphoid cells were composed of small, medium and large cells with pleomorphic nuclei. Smears of peripheral blood (PB) showed lymphopenia (16%) with the appearance of a few atypical lymphoid cells (less than 2%), but not the typical clover leaf cells seen in ATLL. Immunophenotypic study of LN and BM revealed T cell phenotype. PB showed increased CD4+ T cell (T(H), CD3/CD4+, 57%) and decreased CD8+ T cell counts (T(S), CD3/CD8+, 6.7%). The sera of the patient and her family were reactive for HTLV-I antibody. The specific sequences of pol, env, and tax of HTLV-I DNA were detected in the lymphoma cells and peripheral blood mononuclear cells (PBMC) using polymerase chain reaction. Ultrastructural examination of PBMC confirmed numerous type c virus particles in extracellular space. This case was an acute type of ATLL without overt leukemic features in PB. Despite chemotherapy and intensive conservative treatment, she died 3 months after admission.