Susan D. Rouster

Mechanism of indinavir-induced hyperbilirubinemia

Indinavir is a viral protease inhibitor used for the treatment of HIV infection. Unconjugated hyperbilirubinemia develops in up to 25% of patients receiving indinavir, prompting drug discontinuation and further clinical evaluation in some instances. We postulated that this side-effect is due to indinavir-mediated impairment of bilirubin UDP-glucuronosyltransferase (UGT) activity and would be most pronounced in individuals with reduced hepatic enzyme levels, as occurs in ≈10% of the population manifesting Gilberts syndrome. This hypothesis was tested in vitro, in the Gunn rat model of UGT deficiency, and in HIV-infected patients with and without the Gilberts polymorphism. Indinavir was found to competitively inhibit UGT enzymatic activity (KI = 183 μM) while concomitantly inducing hepatic bilirubin UGT mRNA and protein expression. Although oral indinavir increased plasma bilirubin levels in wild-type and heterozygous Gunn rats, the mean rise was significantly greater in the latter group of animals. Similarly, serum bilirubin increased by a mean of 0.34 mg/dl in indinavir-treated HIV patients lacking the Gilberts polymorphism versus 1.45 mg/dl in those who were either heterozygous or homozygous for the mutant allele. Whereas saquinavir also competitively inhibits UGT activity, this drug has not been associated with hyperbilirubinemia, most likely because of the higher KI (360 μM) and substantially lower therapeutic levels as compared with indinavir. Taken together, these findings indicate that elevations in serum-unconjugated bilirubin associated with indinavir treatment result from direct inhibition of bilirubin-conjugating activity.

OCCULT HEPATITIS B IN HIV-INFECTED PATIENTS

Prevalence of hepatitis B virus (HBV) markers, including occult HBV, has not been described in diverse cohorts among HIV-infected patients. The objective of this study was to assess prevalence and significance of active and occult HBV infection in an HIV-positive US cohort. A random sample was taken from 2 prospective multicenter treatment intervention cohorts. The sample population (n = 240) was HIV-1 infected and highly active antiretroviral therapy–naive. Prevalence of HBV serologic markers and quantitative HBV DNA were determined. Serum alanine aminotransferase (ALT) levels were measured to evaluate correlates of hepatocyte injury. A total of 64.6% of subjects demonstrated reactivity for any marker of current or past HBV infection or prior vaccination. Chronic HBV infection characterized by hepatitis B surface antigen (HBsAg) reactivity was present in 7.1% while 15.8% exhibited HB anticore IgG only. Approximately 10% of the latter group was HBV DNA positive by a polymerase chain reaction–based assay. Only patients with a serologic pattern of HBsAg or HB anticore alone reactivity had HBV DNA. Occult HBV was observed in approximately 10% of HIV-infected patients with HB anticore IgG antibody in a geographically representative national cohort. Though viral titers and serum ALT levels were low, screening of this subset of HIV-infected patients may have implications in terms of antiretroviral therapy and risk of immune reconstitution–associated flares.

The prevalence and significance of occult hepatitis B virus in a prospective cohort of HIV-infected patients.

Background:Occult hepatitis B virus (HBV) is defined as low-level HBV DNA without hepatitis B surface antigen (HBsAg). Prevalence estimates vary widely. We determined the prevalence of occult HBV at the University of Cincinnati Infectious Diseases Center (IDC). Methods:Patients in the IDC HIV database (n = 3867) were randomly selected using a 25% sampling fraction. Samples were pooled for HBV nucleic acid extraction. Pools were tested for HBV DNA by a real-time polymerase chain reaction (PCR) assay to coamplify core/surface protein regions. The PCR assay was run on all individual samples from each DNA+ pool. DNA+ samples were tested for HBV serologic markers. Results:A total of 909 patients without known HBV were selected. The mean CD4 count was 384 cells/mm3. Forty-three patients were HBV DNA+. Twelve of 43 were DNA+/HBsAg− (95% confidence interval for database: 0.58% to 1.90%). Five of 12 were negative for all serologic markers. Alanine aminotransferase, aspartate aminotransferase, and HBV DNA titers were elevated in HBsAg+ patients versus occult patients and versus HIV-monoinfected patients. No other significant differences were detected. No occult HBV patient was on treatment with anti-HBV activity. Conclusions:Forty-three percent of those with HBV were not previously identified as HBV+, indicating the need for ongoing screening in high-risk populations. Occult HBV may occur in persons with all negative serologic markers, representing a challenge for identification.

Biphasic in vivo immune function after low- versus high-dose alcohol consumption

A series of experiments was performed to assess the alterations in immune status in vivo that are associated with differences in the amount and duration of ethanol intake. Using a nonspecific delayed cutaneous hypersensitivity-like response to the intradermal injection of phytohemagglutinin, the area of induration (skin test response) was significantly enhanced (p = 0.008) after low-dose ethanol (0.5 g/kg) administered daily by gastric gavage for 5 days. High-dose ethanol (6.0 g/kg) significantly diminished this response (p = 0.03). Using an experimental model of Mycobacterium bovis hepatitis, the host immune response was also altered in a biphasic manner after chronic, 28-day ethanol consumption. With this model 0.43 +/- 0.03 g/kg/day (mean +/- SEM) of ethanol (low dose) was associated with a 40% improvement in the removal of the organisms from liver tissue (p = 0.002). High dose (12.1 +/- 0.5 g/kg/day) impaired removal, resulting in a 55% increase in the number of viable organisms (p = 0.001). The levels of three cytokines, MIF, TNF-alpha, and IL-2, known to be involved in the modulation of the host response to mycobacterial infections, were measured in sera after the infection. The serum levels of these cytokines in response to infection did not correlate with this biphasic response to different alcohol dose levels.

Genotypic characterization of symptomatic hepatitis E virus (HEV) infections in Egypt

BACKGROUND Hepatitis E virus (HEV) is a common cause of acute viral hepatitis (AVH) in many developing countries. In Egypt, HEV seroprevalence is among the highest in the world; however, only a very limited number of Egyptian HEV sequences are currently available. OBJECTIVES The objectives were to determine the HEV genotype(s) currently circulating in Egypt. STUDY DESIGN AVH patients without serologic evidence of hepatitis A, B, and C viruses were evaluated for possible HEV infection using serologic assays for anti-HEV IgM and anti-HEV IgG and real-time PCR for HEV RNA. Stool suspensions from suspected cases were inoculated into rhesus macaques to confirm the presence of HEV. Sequence analysis was utilized to determine HEV genotype. RESULTS Of 287 subjects with AVH enrolled, 58 had serologic evidence of acute HEV infection. Stool samples for two of these patients were repeatedly positive for HEV RNA by real-time PCR. Macaques experimentally inoculated with these human stools also developed viremia. Sequence analysis of open reading frame (ORF) 1 demonstrated that these isolates belonged to HEV genotype 1 and were 3.9-9.5% divergent from other genotype 1 isolates. ORF2 was 5.3-8.7% divergent from previously reported Egyptian isolates. CONCLUSIONS This study strongly suggests that genotype 1 HEV related to other North African isolates is circulating in acute symptomatic patients in Egypt. Further evaluation of genotypic variability is underway in this highly endemic cohort and is considered an important component of our increased understanding of HEV pathogenesis.

HCV kinetics, quasispecies, and clearance in treated HCV-infected and HCV/HIV-1-coinfected patients with hemophilia†

Hepatitis C virus (HCV) treatment response rates remain low in HCV/HIV‐1‐coinfected individuals compared with those with HCV alone. Persons with inherited coagulation disorders have high rates of HCV and HIV‐1 infection, but HCV treatment trials in this patient population are scarce. We hypothesized that differences by infection status in HCV viral kinetics would be associated with differences in HCV quasispecies complexity over time and with treatment response disparities. Coinfected and monoinfected patients were enrolled in a treatment trial for pegylated‐interferon alpha‐2a (peg‐IFN) + ribavirin. Patients were treated for 48 weeks and followed for an additional 24. Quantitative HCV RNA was tested at multiple times during and after treatment. Viral kinetic parameters associated with response were estimated with a mathematical model. Quasispecies emergence was determined via heteroduplex complexity assay. Twenty‐two patients were HCV RNA‐positive at baseline, with no significant demographic or virological differences by infection status. Five of eleven (45%) of monoinfected and 3 of 11 (27%) of coinfected patients achieved sustained viral response (SVR). Peg‐IFN efficacy (ε) of 90% or greater was associated with probability of end‐of‐treatment response (ETR) (P = .001) and SVR (P = .06). Patients with SVR had lower baseline quasispecies complexity than those without SVR (P = .07). Those with ε of 90% or greater also had lower baseline complexity (P = .07). Coinfection status mediated changes in complexity over time (P = .04). In conclusion, low pretreatment quasispecies complexity may predict peg‐IFN response; early peg‐IFN response is critical for sustained HCV clearance and is altered in coinfection. Further studies are warranted. (HEPATOLOGY 2006;44:1146–1157.)

Liver Injury and Changes in Hepatitis C Virus (HCV) RNA Load Associated with Protease Inhibitor–Based Antiretroviral Therapy for Treatment-Naive HCV-HIV–Coinfected Patients: Lopinavir-Ritonavir versus Nelfinavir

BACKGROUND Highly active antiretroviral therapy (HAART) initiation in patients coinfected with human immunodeficiency virus type 1 (HIV-1) and hepatitis C virus (HCV) has been associated with transaminase and HCV viral load flares. Previous studies have included highly variable antiretroviral regimens. We compared effects of 2 protease inhibitor-based regimens on alanine aminotransferase (ALT) levels and HCV loads in HCV-HIV-coinfected patients initiating HAART. METHODS Seventy HIV-infected patients with positive baseline results of HCV enzyme-linked immunosorbant assay from a treatment trial comparing lopinavir-ritonavir with nelfinavir were evaluated during a 48-week period. HCV and HIV titers were analyzed at baseline, at weeks 24 and 48 of treatment, and during flares in the ALT level of >5 times the upper limit of normal. RESULTS A total of 57 of 70 patients tested positive for HCV RNA at baseline. HCV titers for patients in lopinavir-ritonavir and nelfinavir groups, respectively, were as follows: baseline, 6.07 and 6.22 log IU/mL; week 24 of treatment, 6.68 and 6.48 log IU/mL; and week 48 of treatment, 6.32 and 6.44 log IU/mL. Of patients with a CD4+ cell count of <100 cells/mm3 at baseline, 5 of 11 in the nelfinavir group and 0 of 10 in the lopinavir-ritonavir group had an increase in the HCV load of >0.5 log IU/mL from baseline to week 48. The mean ALT level increased by 45 U/L at 24 weeks and 18 U/L at 48 weeks in the nelfinavir group but decreased by 18 U/L at 24 weeks and 7 U/L at 48 weeks in the lopinavir-ritonavir group. Eight patients in the nelfinavir group and 2 patients in the lopinavir-ritonavir group had grade 3 or 4 flares in the ALT level. CONCLUSIONS HAART initiation is associated with increased HCV loads and ALT levels. A low baseline CD4+ cell count is associated with persistent increases in the HCV RNA load in nelfinavir-treated patients. These results warrant careful interpretation of abnormalities in the ALT load after HAART initiation in HCV-HIV-coinfected patients to prevent premature discontinuation of treatment.

Mutations Associated with Occult Hepatitis B Virus Infection Result in Decreased Surface Antigen Expression In Vitro

Summary.  Occult hepatitis B virus (HBV) infection is characterized by the absence of detectable hepatitis B surface antigen (HBsAg) in the serum, despite detectable HBV DNA. Investigations of the mechanisms underlying the development of occult HBV infection are lacking in the current literature, although viral mutations in the surface region, resulting in decreased HBsAg expression or secretion, represent one potential mechanism. Wild‐type HBsAg expression vectors were constructed from genotype‐matched chronic HBV sequences. Site‐directed mutagenesis was then utilized to introduce three genotype A mutations – M103I, K122R and G145A – associated with occult HBV infection in vivo, alone and in combination, into the wild‐type HBsAg vectors. Transfection of Huh7 and HepG2 cell lines was performed, and cell culture supernatants and cell lysates were collected over 7 days to assess the effects of these mutations on extracellular and intracellular HBsAg levels. The G145A mutation resulted in significantly decreased extracellular and intracellular HBsAg expression in vitro. The most pronounced reduction in HBsAg expression was observed when all three mutations were present. The mutations evaluated in vitro in the current study resulted in decreased HBsAg expression and potentially increased hepatic retention and/or decreased hepatic secretion of synthesized HBsAg, which could explain the lack of HBsAg detection that is characteristic of occult HBV infection in vivo.

Genomic variability associated with the presence of occult hepatitis B virus in HIV co-infected individuals.

Summary.  Occult hepatitis B virus (O‐HBV) infection is characterized by the presence of HBV DNA without detectable hepatitis B surface antigen (HBV DNA+/HBsAg−) in the serum. Although O‐HBV is more prevalent during HBV/HIV co‐infection, analysis of HBV mutations in co‐infected patients is limited. In this preliminary study, HBV PreSurface (PreS) and surface (S) regions were amplified from 33 HIV‐positive patient serum samples – 27 chronic HBV (C‐HBV) and six O‐HBV infections. HBV genotype was determined by phylogenetic analysis, while quasispecies diversity was quantified for the PreS, S and overlapping polymerase regions. C‐HBV infections harboured genotypes A, D and G, compared to A, E, G and one mixed A/G infection for O‐HBV. Interestingly, nonsynonymous–synonymous mutation values indicated positive immune selection in three regions for O‐HBV vs one for C‐HBV. Sequence analysis further identified new O‐HBV mutations, in addition to several previously reported mutations within the HBsAg antigenic determinant. Several of these O‐HBV mutations likely contribute to the lack of detectable HBsAg in O‐HBV infection by interfering with detection in serologic assays, altering antigen secretion and/or decreasing replicative fitness.

Hepatitis E Virus Antibodies in Patients with Chronic Liver Disease

In the United States, the seroprevalence rate for hepatitis E virus (HEV) is ≈20%. This study examined HEV seroprevalence in persons with and without chronic liver disease. Our data indicate that HEV seropositivity is high in patients with chronic liver disease and that HEV seroprevalence increases significantly with age.