Antiviral activity of 5'-O-carbonate-2',3'-dideoxy-3'-thiacytidine prodrugs against hepatitis B virus in HepG2 2.2.15 cells

Polymeric therapeutic delivery systems for the treatment of infectious diseases

Infectious diseases caused by germs, parasites, fungi, virus and bacteria are one of the leading causes of death worldwide. Polymeric therapeutics are nanomedicines that offer several advantages making them useful for the treatment of infectious diseases such as targeted drug release mechanism, ability to maintain the drug concentration within a therapeutic window for a desired duration, biocompatibility with low immunogenicity and reduced drug toxicity resulting in enhanced therapeutic efficacy of the incorporated drug. Although polymeric therapeutics have been evaluated for the treatment of infectious diseases in vitro and in vivo with improved therapeutic efficacy, most treatments for infectious disease have not been evaluated using polymeric therapeutics. This review will focus on the applications of polymeric therapeutics for the treatment of infectious diseases (preclinical studies and clinical trials), with particular focus on parasitic and viral infections.

Biological evaluation and molecular modelling of didanosine derivatives

These prodrugs of DDI with increased lipophilicity and good antiviral performance should be of interest in HIV therapy.

Expression of hepatitis B virus 1.3-fold genome plasmid in an SV40 T-antigen-immortalized mouse hepatic cell line

AIM: To investigate the expression of the hepatitis B virus (HBV) 1.3-fold genome plasmid (pHBV1.3) in an immortalized mouse hepatic cell line induced by SV40 T-antigen (SV40T) expression.

METHODS: Mouse hepatic cells were isolated from mouse liver tissue fragments from 3-5 d old Kunming mice by the direct collagenase digestion method and cultured in vitro. The pRSV-T plasmid was transfected into mouse hepatic cells to establish an SV40LT-immortalized mouse hepatic cell line. The SV40LT-immortalized mouse hepatic cells were identified and transfected with the pHBV1.3 plasmid. The levels of hepatitis B surface antigen (HBsAg) and hepatitis B e antigen (HBeAg) in the supernatant were determined by an electrochemiluminescence immunoassay at 24, 48, 72 and 96 h after transfection. The expressions of HBsAg and hepatitis B c antigen (HBcAg) in the cells were investigated by indirect immunofluorescence analysis. The presence of HBV DNA replication intermediates in the transfected cells and viral particles in the supernatant of the transfected cell cultures was monitored using the Southern hybridization assay and transmission electronic microscopy, respectively.

RESULTS: The pRSV-T plasmid was used to immortalize mouse hepatocytes and an SV40LT-immortalized mouse hepatic cell line was successfully established. SV40LT-immortalized mouse hepatic cells have the same morphology and growth characteristics as primary mouse hepatic cells can be subcultured and produce albumin and cytokeratin-18 in vitro. Immortalized mouse hepatic cells did not show the characteristics of tumor cells, as alpha-fetoprotein levels were comparable (0.58 ± 0.37 vs 0.61 ± 0.31, P = 0.37). SV40LT-immortalized mouse hepatic cells were then transfected with the pHBV1.3 plasmid, and it was found that the HBV genome replicated in SV40LT-immortalized mouse hepatic cells. The levels of HBsAg and HBeAg continuously increased in the supernatant after the transfection of pHBV1.3, and began to decrease 72 h after transfection. The expressions of HBsAg and HBcAg were observed in the pHBV1.3-transfected cells. HBV DNA replication intermediates were also observed at 72 h after transfection, including relaxed circular DNA, double-stranded DNA and single-stranded DNA. Furthermore, a few 42 nm Dane particles, as well as many 22 nm subviral particles with a spherical or filamentous shape, were detected in the supernatant.

CONCLUSION: SV40T expression can immortalize mouse hepatic cells, and the pHBV1.3-transfected SV40T-immortalized mouse hepatic cell line can be a new in vitro cell model.

Development and validation of a stability indicating method for seven novel derivatives of lamivudine with anti-HIV and anti-HBV activity in simulated gastric and intestinal fluids

A simple micellar liquid chromatography (MLC) method has been developed and validated for use in stability indicating studies of lamivudine and its carbonate derivatives with proved activity against human immunodeficiency and hepatitis B viruses (HIV and HBV, respectively), in simulated gastric (SGF) and intestinal (SIF) fluids samples. The optimized method involves a C18 column thermostated at 30°C, UV detection at 272 nm, a flow rate of 1.0 mL min(-1) and a micellar mobile phase composed by 0.15M sodium dodecyl sulphate (SDS) - 4% (v/v) 1-butanol - 0.01 M KH2PO4-Na2HPO4 (pH 7), using zidovudine (AZT) as internal standard. Validation under Food and Drug Administration (FDA) guideline of the analytical parameters include: linearity (r(2)>0.9996), LODs (1.6 × 10(-7)-6.9 × 10(-6)M) and LOQ (1 × 10(-5)M), intra (0.02-1.48%) and inter-day precision (0.04-1.66%) expressed as relative standard deviation (R.S.D.), and robustness parameters (less than 1.98%). Using this method, recoveries ranging from 92.9 to 119% were obtained for the eight substances. Thus, this method provides a simple, sensitive, accurate and precise assay for the determination of all compounds that can be readily adaptable to routine use by clinical laboratories with standard equipment. In addition, we evaluated the stability of carbonates of lamivudine in buffer pH 1.2 and 6.8; SGF (pH 1.2) and SIF one (pH 6.8), all as indicated in United States Pharmacopeia (USP) 32. Finally, this chromatographic method was applied to stability studies which resulted in all the compounds following a pseudo-first-order kinetics, and in the determination of its kinetic constant and half-life time.

Intestinal permeability of lamivudine (3TC) and two novel 3TC prodrugs. Experimental and theoretical analyses

Lamivudine (3TC) is an antiviral drug with a widely demonstrated clinical efficacy used to treat Acquired Immunodeficiency Syndrome (AIDS) in humans. However, since the rapid emergence of resistant viral strains has limited its effect, several new strategies such as the design of prodrugs have been applied to try to optimize its pharmacotherapeutic properties. The present study deals with the intestinal permeation of 3TC and two novel prodrugs of 3TC, namely 3TC-Etha and 3TC-Buta, by using rat intestinal segments and applying the gut sac in vitro technique. An adequate bioanalytical method (sample preparation and quantitative analysis) was fully developed and validated for the quantitation of these three compounds. A low permeability coefficient (P(app) 0.408 ± 0.049 × 10(-4) cm/min) was found for 3TC if compared to that previously reported for zidovudine (2.38 ± 0.12 × 10(-4) cm/min), while no statistically significant differences were observed in its apical-to-basal or basal-to-apical permeabilities. Our data suggests that 3TC permeates through the intestinal tissue by passive diffusion, with no intervention of efflux mechanism during this process as determined applying the gut sac technique. Regarding the prodrugs, both 3TC-Etha and 3TC-Buta were able to increase 3TC permeability (2 and 10 times, respectively), but none of these compounds were capable of crossing the intestinal tissue in their intact forms. In the case of 3TC-Etha, the permeability of the intact compound (P(app) 0.093 ± 0.010 × 10(-4) cm/min) was impaired by a P-glycoprotein (P-gp) mediated efflux, evidenced by the higher permeability coefficient (6.933 ± 0.586 × 10(-4) cm/min) determined in the presence of verapamil on the apical side of the enterocyte. In contrast, 3TC-Buta was not subjected to efflux mechanisms on the apical side of the enterocyte, but was efficiently converted to 3TC by enzymatic hydrolysis during the permeation process. In the light of these results, molecular modeling (docking and molecular dynamics) techniques were applied to study further the structural features that may confer the different behaviors of these two compounds with respect to P-gp mediated efflux. The results also highlight the potential of combining experimental and theoretical studies in the design of 3TC prodrugs with enhanced intestinal permeation properties.