Presence of HCV-RNA after ultracentrifugation of serum samples during the follow-up of chronic hepatitis C patients with a sustained virological response may predict reactivation of hepatitis C virus infection

BACKGROUND

Concentration of viral particles by ultracentrifugation of serum prior to PCR allows detection of hepatitis C virus (HCV) RNA in patients with undetectable viral RNA by conventional PCR assays.

AIM

To analyse if HCV-RNA is detected after serum ultracentrifugation in chronic hepatitis C patients with a sustained virological response to antiviral therapy (defined as serum HCV-RNA negativity by conventional assays 6 months after the end of therapy).

METHODS

HCV-RNA was tested using real-time PCR in ultracentrifuged sera collected during the post-treatment follow-up (mean: 42 +/- 27 months) in 57 sustained virological responders (SVR).

RESULTS

After serum ultracentrifugation, HCV-RNA was detected on at least one occasion during the follow-up in 29/57 (51%) SVR. Thirteen (23%) of these 57 SVR suffered a reactivation 18 +/- 8 months after the end of therapy (reappearance of serum HCV-RNA detectable by conventional assays). Among reactivated patients, 11/13 (85%) had HCV-RNA in ultracentrifuged serum samples (detectable 10 +/- 5 months before reactivation), while HCV-RNA was positive after ultracentrifugation in 18/44 (41%) long-term SVR (P = 0.01). Persistence of detectable HCV-RNA after serum ultracentrifugation was associated with reactivation (P = 0.001).

CONCLUSIONS

Serum ultracentrifugation prior to PCR allows detection of HCV-RNA in SVR and its persistence may predict late reactivation.

The role of genomic and antigenomic HCV-RNA strands as predictive factors of response to pegylated interferon plus ribavirin therapy

BACKGROUND

Hepatitis C virus replicates by the synthesis of an antigenomic HCV-RNA. As the end point of anti-viral therapy is to decrease viral replication, the amount of antigenomic HCV-RNA could influence the response.

AIM

To study if amounts of genomic and antigenomic HCV-RNA in the baseline liver biopsy are predictive factors of response to anti-viral therapy.

METHODS

Eighty-eight patients with chronic HCV infection (anti-HIV-negative) treated with pegyltaed-interferon-alpha2b plus ribavirin for 12 months were included. Intrahepatic genomic and antigenomic HCV-RNA concentrations were determined by real-time polymerase chain reaction and percentage of infected hepatocytes by in situ hybridization.

RESULTS

Of the 88 patients, 31% were responders while 69% were not. Median of antigenomic HCV-RNA in liver of responders and non-responders was 120 000 copies/microg RNA (range: 10,000-775,000) vs. 150,000 copies/microg RNA (range: 100-3,200,000; P = 0.38). Median of genomic HCV-RNA in liver of responders was 1,250,000 copies/microg RNA (range: 5000-9,000,000) and in non-responders 3,180,000 copies/microg RNA (range: 4600-18,000,000; P = 0.0191). Predictive factors of response in the logistic regression were: intrahepatic amount of genomic HCV-RNA, percentage of infected hepatocytes and previous therapy.

CONCLUSION

Response to 12 months of therapy with pegylated interferon-alpha2b plus ribavirin depends on the amount of genomic HCV-RNA in the pre-treatment liver biopsy.

Disposable sample holder for high temperature measurements in MPMS superconducting quantum interference device magnetometers

A sample holder for high temperature (300 K<T<800 K) measurements in superconducting quantum interference device magnetometers is presented. It is fabricated using aluminum foil and it is appropriate for samples in either solid or powder form. The holder is homogeneous for the gradiometer coil, and this results in a contribution to the background signal that is below the instrument noise at any field (<10(-9) A m2 at mu(0)H=200 mT). Further it is inexpensive and simple to fabricate, and it can be considered as a disposable sample holder that avoids eventual contamination between different samples.

Effect of biostimulation on the expression of estrus in postpartum Angus cows

The objective of this study was to evaluate the effect of biostimulation by bull exposure on the expression of estrus in postpartum Angus cows. Ninety Angus cows and their calves were allocated by parity and body frame to three pens (30/pen). From 1-week post partum, one epididectomized mature Angus bull was placed with Groups A and B (BE), whereas Group C served as a Control (NE). Data for duration of estrus (DE), total mounts received (TMR), and intensity of estrus (IE) were recorded using HeatWatch. At either the first or second postpartum estrus, there were no differences between BE and NE cows for DE, TMR and IE. However, the period after onset of estrus, cow within treatment and the interaction treatment by period exerted a significant influence on IE. Overall, the greatest IE (P<0.0001) was observed during the first two periods (6h). At the first postpartum estrus, IE tended (P<0.11) to be greater in BE than NE cows during the first 3h after onset of estrus. However, IE was greater (P<0.02) in NE cows than BE cows during 4-6h after onset of estrus. At the second postpartum estrus, IE did not differ between BE and NE cows during the first 3h after onset of estrus. However, from 4 to 9h after onset of estrus, IE was greater (P<006) in NE cows than BE cows. From the results of this study, it was concluded that DE, TMR and IE were not influenced by biostimulation. However, the manner in which mounting activities were distributed across the duration of estrus was influenced by the presence of bulls.

Hepatitis C virus (HCV) and hepatitis B virus (HBV) can coinfect the same hepatocyte in the liver of patients with chronic HCV and occult HBV infection

In this work, we have shown that hepatitis C virus (HCV) and hepatitis B virus (HBV) can coexist in the same hepatocyte using double fluorescent in situ hybridization in liver biopsy samples from patients with chronic HCV infection with occult HBV infection. Digital image analysis of hybridization signals showed that the HBV DNA levels in coinfected hepatocytes were lower than those in cells infected only with HBV. This finding supports the hypothesis of inhibition of HBV replication by HCV. Furthermore, HCV RNA levels were lower in coinfected cells than in cells infected only with HCV, suggesting that HBV may also inhibit HCV replication.

Hepatitis C virus replicates in peripheral blood mononuclear cells of patients with occult hepatitis C virus infection

BACKGROUND

Occult hepatitis C virus (HCV) infection is characterised by the presence of HCV-RNA in the liver in the absence of anti-HCV, and serum viral RNA. Up to 70% of these patients also have HCV-RNA in peripheral blood mononuclear cells (PBMC) but it is not known if HCV is replicating in these cells.

AIM

We studied possible HCV replication in PBMC of 18 patients with an occult HCV infection who were selected on the basis of HCV-RNA positivity in PBMC.

METHODS

Detection of HCV-RNA positive and negative strands in PBMC was done by strand specific reverse transcriptase-polymerase chain reaction (RT-PCR) and by in situ hybridisation.

RESULTS

The presence of HCV-RNA positive strand in PBMC was confirmed in all patients by strand specific RT-PCR and by in situ hybridisation. Mean percentage of PBMC which had the HCV-RNA positive strand was 3.3% (95% confidence interval (CI) 2.1-4.4) The HCV-RNA negative strand was found in the PBMC of 11/18 (61%) patients by strand specific RT-PCR and confirmed by in situ hybridisation, and the percentage of PBMC harbouring the HCV-RNA negative strand was 3.1% (95% CI 0.8-5.5). There was a significant correlation (p = 0.001, r = 0.84) between the percentage of PBMC with the HCV-RNA positive strand and that of PBMC with the HCV-RNA negative strand.

CONCLUSION

HCV replicates in the PBMC of patients with occult HCV infection and thus, although these patients do not have serum HCV-RNA, they could be potentially infectious.

Effect of biostimulation on uterine involution, early ovarian activity and first postpartum estrous cycle in beef cows

The objective was to determine the effect of biostimulation (bull-exposure) on uterine involution (UI), plasma progesterone concentration (P4), size of largest follicle (LF), number of follicles larger than 5 mm ( F > or = 5 ), presence of fluid in uterine lumen (PF), presence of luteal tissue (LT), and length of the first estrous cycle postpartum (LEC). Ninety Angus cows with calves were allocated by parity and body frame into three groups (30 per group) 1 week postpartum. Two groups were exposed to bulls (BE) and one non-exposed group (NE) served as a control. Data were collected during weekly sessions of palpation per rectum, ultrasonography and bleeding on a subgroup of 30 cows (10 cows per group) for 6 weeks, and permanent surveillance of estrus with HeatWatch on all 90 cows. There were no significant differences between BE and NE cows for UI ( 17.1+/-1.1 days versus 20.1+/-1.6 days), LF ( 9.5+/-1.7 mm versus 11.0+/-2.4 mm), F > or = 5 ( 1.20+/-0.3 versus 1.47+/-0.09 ), and PF. However, LT was detected in more BE than NE cows (13 versus 2; P<0.001 ). Overall differences in P4 were found between BE and NE cows with detected LT ( 2.00+/-0.3 ng/ml versus 1.05+/-0.4 ng/ml, respectively; P<0.05 ). More BE cows resumed reproductive cyclicity with estrous cycles normal in length compared with NE cows (16/30, 53%; 16/30, 53%; and 8/30, 26.6%, for the two BE groups and the NE group, respectively; P<0.01 ). In conclusion, BE hastened luteal function but did not affect uterine involution.

Ribozymes as antiviral agents

Ribozymes are RNA molecules with cleavage activity that can be engineered to specifically target a given RNA molecule. The hammerhead, hairpin and hepatitis delta virus ribozymes have been widely studied for their use as therapeutical agents. This review discusses the structure and properties of these ribozymes, along with the advances made in the development of these molecules for their application in the treatment of hepatitis B, hepatitis C and human immunodeficiency virus infections.

[Recurrent episodes of acidosis with encephalopathy in a hemodialysis program patient with short bowel syndrome]

We present a case of a patient with short bowel syndrome in a hemodialysis program, with recurrent episodes of serious acidosis. The presence of a D-lactic acidosis peak secondary to bacterial overgrowth in the intestine was discovered during an acute episode of acidosis, with neurological affection. The detection of acidosis in predialysis measurements and the acute episodes of acidosis, made it necessary to administer bicarbonate to the patient and give him additional hemodialysis sessions.

In vitro infection of human peripheral blood mononuclear cells by a defective hepatitis B virus with a deletion in the PreS1 region of the viral genome

Previously, we identified a defective hepatitis B virus (HBV) which contains a 183 nucleotide deletion in the PreS1 region of the viral genome affecting the S gene promoter in sera from hepatitis B surface antigen (HBsAg)-negative patients with serum HBV-DNA. The aim of this study was to analyse the infectivity of this mutant. Peripheral blood mononuclear cells (PBMC) from a healthy donor were incubated with serum samples from 2 HBsAg-negative patients with serum HBV-DNA (infected with wild-type and deletion mutant HBV), from an HBsAg carrier (infected with wild-type HBV) and from a healthy donor. After 1 week, HBV-DNA was detected by polymerase chain reaction (PCR) in all supernatants and cells incubated with the HBV-DNA-positive inocula. DNase and trypsin pretreatment confirmed intracellular localization of HBV-DNA in cells. HBV-RNA and covalently closed circular HBV-DNA were also detected in PBMC, indicating that the viral DNA infecting these cells was transcriptionally active. Deletion mutant and wild-type HBV were detected in the supernatants and cells infected with the two HBsAg-negative sera, while only wild-type HBV was detected in the supernatant and cells incubated with the serum from the HBsAg-carrier. In conclusion, this HBV deletion mutant can infect, replicate and release viral particles in in vitro infected PBMC.

Magnetic relaxation of interacting co clusters: crossover from two- to three-dimensional lattices

The influence that dipole-dipole interactions exert on the dynamics of the magnetization of nanometer-sized Co clusters has been studied by means of ac and dc susceptibility experiments. These clusters grow in a quasiordered layered structure, where all relevant parameters can be tailored and measured independently. Our data show without ambiguity that the magnetic relaxation becomes slower as the degree of interaction increases. The effective activation energy increases linearly with the number of nearest neighbor clusters, evolving from the value for a 2D layer to the fully 3D behavior, which is nearly reached for five layers. The experimental results agree quantitatively with the predictions of a simple model.

B cell function after haploidentical in utero bone marrow transplantation in a patient with severe combined immunodeficiency

An in utero paternal CD34(+) cell transplant was performed in a T-B+NK+ SCID fetus. We report here the results of the 3-year humoral immune reconstitution study. The methods used were ApoB VNTR typing, flow cytometry, nephelometry, hemagglutination, ELISA, ELISPOT and lymphoproliferative assays. The T cells were of donor origin whereas monocytes, B and NK cells were of host origin. Peripheral B cell counts and IgM levels were normal since birth. IVIG therapy was required at 5 months of age until 2 years old. IgA levels > or =20 mg/dl were detected from month 17 post transplantation. Isohemagglutinins were present since month 8 post transplantation, the highest titers (anti-A:1/128, anti-B:1/32) were obtained at month 33 post-transplantation. After immunization with rHBsAg, circulating anti-HBsAg IgG secreting cells and a 7.8-fold increase in serum anti-HBsAg Ab were detected. We conclude that split chimerism following in utero haploidentical BMT allows complete humoral immune reconstitution in a T-B+NK+ SCID patient.

Distribution of hepatitis C virus infection in liver biopsies from children and adults with chronic hepatitis C

Chronic hepatitis C in children is characterized by milder forms of liver damage than those found in adults. Such a difference has been attributed to a low viral load in children that may lead to poor recognition of infected cells by the immune system. One approach that could be used to confirm this hypothesis may be to examine the number of infected hepatocytes in liver biopsies. Paraffin embedded liver biopsies from 21 children and 15 adults with chronic hepatitis C virus (HCV) infection (with a similar duration of the infection) were hybridized in situ and the percentage of infected hepatocytes was correlated with the histological activity index, alanine aminotransferase levels and HCV viraemia levels. Histological activity index and HCV viraemia levels were statistically higher (P < 0.05 and P < 0.01 respectively) in adults than in children, and the percentage of infected hepatocytes was higher in adults (11.0 +/- 19.7%) than in children (4.6 +/- 3.6%), although it did not reach statistical significance. Also, the percentage of infected hepatocytes correlated with HCV-RNA concentration in serum in both children (r = 0.683, P = 0.001) and adults (r = 0.768, P = 0.001). The results show that liver damage in children with chronic hepatitis C is not related to the extent of infection in the liver. This findings support the hypothesis of that liver injury in chronic HCV infection is mediated by the host immune response.

TT virus detection in oral lichen planus lesions

Epidemiological studies have demonstrated a correlation between oral lichen planus and different liver diseases. The new virus termed TT virus (TTV) is highly prevalent in patients with chronic hepatitis of different etiology and it may be speculated that TT virus may be involved in the pathogenesis of oral lichen planus. This study examined the presence of TT virus DNA in serum by PCR and in oral mucosa biopsies by in situ hybridization from 20 patients with oral lichen planus (13 with chronic hepatitis and seven without liver disease). Serum and oral mucosa biopsies from six patients all with chronic hepatitis with leukoplakia were also studied as controls. TT virus DNA was positive in the serum of 17/20 (85%) of the patients with oral lichen planus and in all the controls. TT virus DNA hybridization signals were detected in mucosa biopsies from all the patients with TT virus DNA in serum but in none of the three cases without this marker. The percentage of positive cells ranged from 1.6-80%. No differences were found in the percentage of positive cells between TT virus positive patients with and without oral lichen planus and there was no relationship between the number of positive cells and the intensity of the inflammatory infiltrate. In conclusion, TT virus infects oral epithelial cells but the results do not support a role for TT virus in causing oral lichen planus.

Expression of factor VII in the liver of patients with liver disease: correlations with the disease severity and impairment in the hemostasis

Factor VII (FVII) plasma levels in patients with liver disease may be below the normal range. However, no data are available on FVII expression in liver biopsies from patients with liver diseases other than cirrhosis. We have analyzed the expression of FVII by in situ hybridization in liver biopsies from 50 patients in comparison with the procoagulant activity of FVII, and with the plasma levels as activated FVII (FVIIa) and FVII antigen. The level of FVIIa was significantly lower in stage 4 liver fibrosis patients than in the remaining ones (P < 0.05). The percentage of hepatocytes expressing FVII was significantly lower in stage 4 liver fibrosis patients (4.1+/-1.3%) than in stage 3 (22.7+/-6.1%), stage 2 (31.5+/-6.1%), stage 1 (43.7+/-8.2%) and stage 0 patients (63.8+/-4.4%) (P < 0.001). These percentages correlated inversely in a statistically significant way with the histological activity index and the liver function tests. We have demonstrated that the FVIIa plasma levels in patients with chronic liver disease other than cirrhosis may be below the normal range in the absence of blood coagulation impairment. The percentage of hepatocytes expressing FVII decreases as the severity of liver damage increases.

Prevalence of hepatitis B, hepatitis C, GB virus C/hepatitis G and TT viruses in predialysis and hemodialysis patients

Patients with chronic renal failure on hemodialysis have a high risk of infections with viruses such as hepatitis B (HBV), hepatitis C (HCV), GB virus C/hepatitis G (GBV-C/HGV) and TT (TTV) viruses. The prevalence of HBV, HCV, GBV-C/HGV and TTV in patients with chronic renal failure who are on conservative management before entering into a hemodialysis program (predialysis) in comparison with hemodialyzed patients was studied to elucidate whether the high prevalence of these viruses is influenced by that observed in the predialysis stage. The presence of hepatitis B virus surface antigen (HBsAg), HCV RNA, GBV-C/HGV RNA and TTV DNA was analyzed in sera from 80 patients with chronic renal failure (35 on predialysis and 45 on hemodialysis). HBsAg, HCV RNA, GBV-C/HGV RNA and TTV DNA were detected in one (2.8%), six (17.1%), eight (22.5%) and 16 (45.7%) of the 35 patients on predialysis. Two (5.7%) of these patients were coinfected with HCV and GBV-C/HGV, whereas six (17.1%) had GBV-C/HGV and TTV coinfection. In the 45 hemodialyzed patients, HBsAg, HCV RNA, GBV-C/HGV RNA and TTV DNA were detected in one (2.2%), two (4.4%), seven (15.5%) and 26 (57.7%). One (2.2%) patient had HBV and TTV coinfection, two (4.4%) HCV and TTV coinfection whereas four (8.8%) were coinfected with GBV-C/HGV and TTV. No differences regarding age, gender, previous surgery and number of transfusions were found between infected and uninfected patients within and between both groups. In conclusion, the prevalence of the viruses studied in predialysis may influence their prevalence in dialysis units.

In situ detection of hepatitis C virus RNA in salivary glands

Chronic hepatitis C virus (HCV) infection has been associated with several extrahepatic manifestations, among these, to diseases with oral manifestations such as Sjögren's syndrome or sialadenitis. HCV-RNA has been detected in saliva and in salivary glands from patients with sialadenitis by polymerase chain reaction. However, morphological evidence of HCV replication in salivary gland cells is needed to support a role for HCV in causing sialadenitis or Sjögren's syndrome. We have used in situ hybridization and immunohistochemistry to analyze the presence of HCV-RNA of sense and antisense polarity and HCV core antigen, respectively, in salivary gland biopsies from 19 patients with chronic sialadenitis or Sjögren's syndrome (eight anti-HCV-positive; 11 anti-HCV-negative). HCV-RNA of both positive and negative polarity as well as HCV core antigen were detected in the epithelial cells of the salivary gland biopsies from all of the anti-HCV-positive patients but in none of the anti-HCV-negative cases. The percentage of HCV-infected cells ranged from 25 to 48.8% in the patients studied. In conclusion, we have shown that HCV infects and replicates in the epithelial cells from salivary glands of patients with Sjögren's syndrome or chronic sialadenitis. However, its implication in the pathogenesis of these diseases deserves future research.

Increased levels of activated subsets of CD4 T cells add to the prognostic value of low CD4 T cell counts in a cohort of HIV-infected drug users

OBJECTIVE

To identify subsets of CD4 T lymphocytes that can predict the development of AIDS and to assess whether increased levels of these cellular markers could provide additional independent prognostic information to the CD4 T cell count and plasma HIV-1-RNA levels.

DESIGN AND METHODS

In a prospective study, a cohort of 85 HIV-positive intravenous drug users [clinical categories of the CDC classification A (n = 48) and B (n = 37)] were followed for a period of 37+/-13 months. Memory and activated CD4 and CD8 T cells were quantitated by three-colour flow cytometry at baseline and expressed as a percentage of total CD4 and CD8 lymphocytes. Clinical evaluations were performed at 6 month intervals. The relationships between these lymphocyte subsets and progression to AIDS were studied using Kaplan-Meier plots and proportional hazards regression models.

RESULTS

After adjustment for the level of CD4 T cells and plasma HIV-1-RNA levels, the elevation in the subset CD4+CD38+DR+ was the marker within the functionally distinct subsets of CD4 T lymphocytes with additional prognostic value in bivariate Cox regression models. In multivariate models, increased percentages of CD4+CD38+DR+ T cells provided the strongest independent prognostic information for progression to AIDS (relative hazard, 1.07; P < 0.0001).

CONCLUSION

Our results suggest that high levels of CD4+CD38+HLA-DR+ T cells reflect the increasing degree of CD4 T cell activation during the progression of HIV infection, and could be used together with the CD4 T cell and HIV-RNA levels to evaluate more accurately the progressive cellular immune impairment associated with the risk of progression to AIDS.

Presence of TTV DNA in serum, liver and peripheral blood mononuclear cells from patients with chronic hepatitis

The main site of TT virus (TTV) replication remains unknown. Therefore, we have studied the presence and titres of TTV DNA in paired serum, liver and PBMC samples from 50 patients with liver disease (32 with chronic hepatitis B or C, seven with cryptogenic hepatitis and 11 with nonviral liver disease) were included. TTV DNA was analysed by polymerase chain reaction (PCR) using primers from the open reading frame 1 (ORF 1) and from the untranslated region (UTR) and titres were semiquantified by PCR using an external standard. TTV DNA was detected in 26% of serum, 24% of liver and 14% of PBMC samples with ORF 1 primers. When UTR primers were used, 70% of serum and liver samples and 64% of PBMC were TTV DNA positive. No differences between TTV positive and negative patients were found regarding epidemiological or biochemical parameters. Trypsin treatment and fluorescent in situ hybridization confirm the intracellular location of TTV in PBMC. The mean of TTV DNA titres was statistically higher in liver than in serum or PBMC. TTV titres in serum correlated with those in PBMC but not with those in liver. In conclusion, although the liver seems to be the main site for TTV replication, this virus is also able to infect PBMC.

Existence of distinct GB virus C/hepatitis G virus variants with different tropism

To study the existence of GB virus C/hepatitis G virus (GBV-C/HGV) variants with different tropism, we have analyzed the heterogeneity and quasispecies composition of GBV-C/HGV isolated from in vitro-infected peripheral blood mononuclear cells (PBMC) and from sera, livers, and PBMC from two chronically infected patients. For this purpose, the GBV-C/HGV 5' noncoding region (5'NCR) was amplified by reverse transcription-PCR and the amplified products were cloned and sequenced. These analyses showed that the master 5'NCR sequences isolated from the in vitro-infected PBMC and from the PBMC isolated from the patient whose serum was used as the inoculum were identical but different from that of the inoculum. Furthermore, phylogenetic analysis revealed that all PBMC sequences grouped together into a branch which was separate from those of the inoculum. For one of the two chronically infected patients, all the sequences from the PBMC and one from the liver clustered into a single branch while the sequences from the serum and all the other liver sequences grouped together in the other branch. For the other patient, the sequences from the serum and PBMC and three sequences from the liver grouped together into one branch, while the remaining five sequences from the liver were separated in a different cluster. In conclusion, our results support the existence of different GBV-C/HGV variants with different tissue tropism.

Molecular analysis of hepatitis B virus DNA in serum and peripheral blood mononuclear cells from hepatitis B surface antigen-negative cases

We have analyzed the molecular bases of the persistence of hepatitis B virus (HBV) DNA in serum and peripheral blood mononuclear cells (PBMC) in the absence of detectable hepatitis B surface antigen (HBsAg) in hemodialysis patients and dialysis-unit staff members who had suffered acute hepatitis B that resolved previously. HBV DNA was found in both compartments by polymerase chain reaction (PCR) using primers of the pre-S/S region. Viral DNA was transcriptionally active in PBMC, because the covalently closed circular (ccc) HBV DNA, the template for the viral RNA transcription, was detected in 47% of the samples. Furthermore, all PBMC had HBV RNA. HBsAg-negative cases had statistically lower levels of HBV DNA in serum and PBMC than a control group of chronic HBsAg carriers. We have also studied the presence of immune complexes and the existence of mutations in the pre-S/S gene to explain the lack of detection of HBsAg in these cases. No serum HBsAg/hepatitis B surface antigen antibody (anti-HBs) immune complexes or mutations in the "a determinant of the S gene were found. However, we have observed that all HBsAg-negative cases were infected by a mixture of the wild-type virus and a deletion mutant in the pre-S1 region. This deletion (amino acids 58-118) affects the S gene promoter, and previous in vitro studies have shown that it produces a reduction of the HBsAg synthesis. In conclusion, this work shows that the lack of detection of HBsAg in the presence of low viral levels of replication may be caused by the existence of viral genomes harboring deletions in the pre-S1 region that affect the S promoter.