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L Vitvitski

Publications and source records attributed to L Vitvitski.

At least 19 recordsLinked to original sources
PubMed2001

HCV infection in northeastern Brazil: unexpected high prevalence of genotype 3a and absence of African genotypes.

The genomic diversity of HCV embraces 6 genotypes and at least 52 subtypes with clinical and epidemiological correlations. There is a paucity of studies assessing HCV genotypes and biomolecular epidemiology in Brazil. We studied genotype distribution and epidemiological aspects in 232 HCV carriers, 133 (57.9%) males and 99 (42.1%) females, followed in the liver disease referral unit in Salvador, BA, northeastern Brazil. All of them were anti-HCV positive by 3rd generation ELISA assay, and HCV-RNA positive by RT-PCR. Genotyping was performed by INNOLIPA. Assessment of risk factors for HCV infection showed that 93 (40%) had past blood transfusion, 14 (6%) intravenous drug use, 19 (8%) inhalation of cocaine, 28 (12%) tattooing, 15 (7%) were health care workers, 5 (2%) had reused disposable syringes, 5 (2%) had multiple risk factors and in 53 (23%) no risk factor was determined. Genotype 1a was observed in 75 (32%), 1b in 72 (31%), 3a in 61 (26%), 2ab in 14 (6%); 5 (2.5%) had mixed genotypes and 5 (2.5%) were undetermined. Patients with genotype 1 had a higher mean age (P < 0.05) and no particular risk factors were associated with a specific genotype. Genotype 1 largely predominates in northeast Brazil followed by genotype 3 which, in this population, does not seem to be related to intravenous drug abuse, in contrast to some European studies. Although 80% of the Salvador population comprises African-Brazilians, no African genotype was identified, which may mean that HCV was introduced into this region via European immigration. This study demonstrated some peculiarities of HCV epidemiology in Brazil and strongly suggests that HCV introduction to this region was probably related to European immigration.

Adult↗
PubMed2000

Severe strongyloidiasis during interferon plus ribavirin therapy for chronic HCV infection.

Ribavirin is a nucleoside analogue, recently introduced in hepatitis C virus (HCV) therapy, that has postulated immunomodulatory and immunosuppressive action. Strongyloidiasis is an helmintic infection caused by Strongyloides stercoralis, endemic in tropical countries. Severe strongyloidiasis has been demonstrated after immunosuppression by corticosteroids evolving some fatal cases. Here, we describe two cases of severe strongyloidiasis coincident with ribavirin plus interferon therapy for treating HCV infection. The review of our monotherapy protocol with interferon did not disclose any case of symptomatic strongyloidiasis pointing to a possible role of ribavirin in modifying immune response to S. stercoralis. We propose a careful screening for S. stercoralis before initiating ribavirin therapy or even empiric antihelmintic treatment.

Adult↗
PubMed1999

Acute sporadic non-A, non-B hepatitis in Northeastern Brazil: etiology and natural history.

In a 4-year follow-up study, patients with acute sporadic non-A, non-B (NANB) hepatitis were evaluated to determine the etiology and natural history of the disease. Acute hepatitis C virus (HCV) was detected in 13 of 43 (30%) of patients, anti-hepatitis E virus (HEV) IgG in 5 (12%), and 25 (58%) were considered non-A-E. The HCV RNA was detected in all HCV patients but none of the non-A-E cases. The initial clinical and biochemical presentation of the HCV and non-A-E cases was quite similar, although 2 of the non-A-E patients had severe disease. The 5 patients who were found to be anti-HEV IgG-reactive recovered within 6 months of follow-up. Of the 13 HCV cases, alanine transaminase (ALT) levels returned to normal in 7 (53. 8%), while 6 (46.2%) continued to show abnormal ALT after 6 months of follow-up. However, 9 (69.2%) of them remained HCV-RNA-positive, denoting virological/biochemical dissociation. Long-term follow-up showed a reappearance of HCV RNA in 2 of the 4 patients who were in virological remission performing 84% of chronicity rate. Acute non-A-E hepatitis patients were less likely to evolve toward chronicity, as compared with acute HCV cases (16% vs. 84%; P =.0001). Only 4 (16%) of the non-A-E patients were hepatitis G virus (HGV)-RNA-positive. Concerning risk factors for acquiring parenterally transmitted viruses, tattooing was the only one that could be associated with HCV transmission (P =.002). No risk factors could be identified for putative non-A-E virus transmission. Liver biopsies performed for chronic HCV patients showed a variable degree of inflammation, while the non-A-E patients presented less severe histological disease.

Acute Disease↗
PubMed1998

Modulation of immune responses to hepatitis C virus envelope E2 protein following injection of plasmid DNA using single or combined delivery routes.

Different delivery routes of plasmid DNA may result in the induction of differential humoral and cellular immunity. We have studied the influence of two main routes of plasmid injection, performed intramuscularly and intraepidermally using a gene gun, for the induction of immune responses specific to hepatitis C virus (HCV) envelope protein E2. Three plasmids expressing different immunogenic domains of E2 (amino acids [aa] 384443, aa 504-555, and aa 384-746) were injected into BALB/c mice according to five different protocols using various combinations of intramuscular (i.m.) or intraepidermal (i.e.) primary and booster injections. Seroconversion rates, antibody titers and isotypes, epitope recognition, and T-helper (Th) release cytokine profiles were analyzed. Antibody titers and epitope recognition were linked to either or both the nature of the immunogen expressed and the delivery route chosen. In all cases, the lowest antibody titers were obtained using single i.m.-based protocols. Independently of the antibody titers generated, only some specific i.e.-combined delivery routes induced antibodies able to recognize determinants located in the N-terminal of E2 (aa 384411 and aa 411437) and mimicked by synthetic peptides. By contrast, the antibody isotypes and the splenic cytokine production identified were independent of the plasmids used and the delivery route implemented. All conditions resulted in Th-1 like responses suggested by the exclusive detection of IgG2a and 2b antibodies and the production of interferon gamma (INF-gamma) but no interleukin-4 (IL-4). Overall, our results suggest that the combination of i.m. and i.e. delivery routes provides the most efficient way to induce a broad immune response against HCV-E2.

Animals↗
PubMed1997

DNA vaccination for the induction of immune responses against hepatitis C virus proteins.

Recent analysis of clinical and experimental cases of hepatitis C virus (HCV) infection suggest the possible role of the viral nucléocapsid (C), the nonstructural protein 3 (NS3) and the envelope glycoproteins E1 and/or E2 in the mounting of immune responses capable to control infection (Botarelli et al., Gastroenterology, 1993, 104, 580-587; Choo et al., Proc. Natl Acad. Sci. USA, 1994, 91, 1294-1298). We have used DNA-based immunization to study the immune responses that can be induced by injecting DNA-derived immunogens encoding C and E2 sequences. Comparative analysis were performed in mice using expression plasmids containing full-length or partial gene sequences cloned in fusion with the hepatitis B virus surface antigen (HBV-HCV chimeras). The results obtained indicate that: (1) anti-C and anti-E2 antibodies can be induced with all constructs including the HBV-HCV chimeras; (2) titers range from 1:100 to 1:100000 depending on the antigen and nucleotide sequence context; (3) all HCV DNA immunogens are associated with a predominant Th1 response; (4) CTL can be detected against both HCV and HBV determinants.

Animals↗
PubMed1997

Plasmid DNA expressing a secreted or a nonsecreted form of hepatitis C virus nucleocapsid: comparative studies of antibody and T-helper responses following genetic immunization.

In a murine model, we have compared humoral and T-helper (Th) responses induced following genetic immunization with two hepatitis C virus (HCV) plasmid-derived immunogens: a plasmid expressing the full-length nucleocapsid (CAP) as a nonsecreted antigen (pCMVC2) and a plasmid expressing the amino-terminal part of CAP as a secreted antigen (pS2S.C2N). In BALB/c mice, intramuscular injection of either plasmid induced IgG2a antibodies associated with a Th1-like profile characterized by the in vitro splenic production of interleukin-2 (IL-2) and interferon-gamma (IFN-gamma). The pS2S.C2N plasmid induced antibody titers three- to five-fold higher than those obtained with the pCMVC2 plasmid (maximal titers 1:1,500 versus 1:500). In control experiments, immunization using purified CAP antigen induced a predominant, but not exclusive, Th2-like profile as determined by the splenic production of IL-4 and IL-10. Six putative Th determinants were identified using a panoply of overlapping synthetic peptides in in vitro stimulation assays: amino acids 20-44, 39-63, 79-113, 89-113, 118-142, and 138-152. For all CAP immunogens, MHC haplotype of immunized mice was found to influence seroconversion rates but not the type of cytokines produced in vitro. H-2d mice were faster responders and displayed recall T-cell activation by a larger number of peptides than H-2b mice, whereas H-2s mice were overall very poor responders. Splenic stimulation by at least one determinant, amino acids 79-103, appeared to be highly specific of the H-2b background and of DNA immunization only. These data indicate that DNA immunogens expressing different forms of HCV-CAP are not associated with different Th profiles but rather different seroconversion rates and antibody titers and that collaboration of distinct T-help epitopes can be restricted by the MHC background.

Animals↗
PubMed1997

Immunization with plasmid DNA encoding hepatitis C virus envelope E2 antigenic domains induces antibodies whose immune reactivity is linked to the injection mode.

Plasmids expressing different domains of the hepatis C virus (HCV) envelope E2 glycoprotein from a genotype 1a isolate were constructed to compare the immunogenic potential of E2 in nucleic acid-based immunizations. One plasmid, pCIE2t, expressed a C-terminally truncated form of E2, while others, pS2.SE2A to pS2.SE2E, encoded the adjacent 60-amino-acid (aa) sequences of E2 (inserts A to E) expressed as a fusion with the hepatitis B virus surface antigen. BALB/c mice were given injections of the plasmids intramuscularly (i.m.) or intraepidermally (i.e.) via a gene gun (biolistic introduction), and induced humoral immune responses were evaluated. The i.e. injections resulted in higher seroconversion rates and antibody titers, up to 100-fold, than did the i.m. injections (P = 0.01 to 0.04). Three restricted immunogenic domains, E2A (aa 384 to 443), E2C (aa 504 to 555), and E2E (aa 609 to 674), that yielded antibody titers ranging from 1:59 to > 1:43,700 could be identified. Subtype 1a- and 1b-derived E2 antigens and synthetic peptides were used in Western blot and enzyme-linked immunosorbent assay analyses, which revealed that the cross-reactivity of the plasmid-induced antibodies was linked both to the type of antigen expressed and to the injection mode. Induced anti-E2 antibodies could immunoprecipitate noncovalent E1E2 complexes believed to exist on the surface of HCV virions. This study allowed us to identify restricted immunogenic domains within E2 and demonstrated that different routes of injection of HCV E2 plasmids can result in quantitatively and qualitatively different humoral immune responses.

Animals↗
PubMed1997

[Efficacy of interferon alpha in primary prevention of preneoplastic lesions in a transgenic murine model of hepatocellular carcinoma related to the interaction between woodchuck hepatitis viruses and c-myc oncogene].

OBJECTIVES: C-myc oncogene overexpression by near insertion of hepatitis B virus is important in woodchuck hepatocarcinogenesis. This DNA fragment was transferred in mice who developed hepatocellular carcinoma via preneoplastic lesions. In the present study, we tested the preventive effect of alpha interferon on the incidence of hepatocyte dysplasia. METHODS: Human recombinant alpha interferon hybrid B/D was continuously administered at increasing doses (0 to 10,000 IU/g) in a transgenic mouse model. One cohort was treated from day 21 to day 80. A histological liver examination was performed and the transgene expression was assessed by hybridization with or without previous genic amplification, and by indirect immunofluorescence. RESULTS: At day 15, histological liver examination was normal. Interferon treatment decreased the expression of viral sequences, but not of c-myc. At day 80, interferon treatment resulted in a reduction of the incidence and severity of dysplasic lesions, and a marked decrease in c-myc overexpression. CONCLUSION: In this transgenic mouse model, alpha interferon treatment decreased the incidence and severity of precancerous lesions, due to a reduction in c-myc overexpression. This prophylaxis could be of interest in human hepatocarcinogenesis where c-myc overexpression is frequent.

Animals↗
PubMed1995

Single-step nested polymerase chain reaction for detection of different genotypes of hepatitis C virus.

Hepatitis C virus (HCV) exhibits considerable sequence variability and circulates in the blood at extremely low levels. Current methods for detecting HCV RNA are based mostly on nested polymerase chain reaction (PCR), in which part of the first amplification product is reamplified in the second tube by an internal primer pair. A novel nested PCR method was developed in which the two successive amplification processes are carried out in the same tube with a single step of physical manipulation. Careful selection of highly conserved sequences of the 5' noncoding region as primers enabled successful detection of all three major genotypes circulating in France, including the one with variation in this region. Retaining high sensitivity of the conventional nested PCR, the novel method reduced greatly the risk of carry-over contaminations. It was also cost- and time-saving. The one-step nested PCR method is especially suitable for routine diagnosis of HCV infection in clinical laboratories.

Base Sequence↗
PubMed1995

Serial transmission of spongiocytic hepatitis to woodchucks (possible association with a specific delta strain).

BACKGROUND/AIMS: Outbreaks of severe hepatitis have been reported from Africa and South America. Description of the cases has shown the histological hallmark to be the presence of ballooning hepatocytes with fat drops surrounding the nucleus (spongiocytes or morula cells). METHODS: Experimental reproduction of this syndrome for the verification of a possible role of a specific HDV strain was performed by the inoculation of serum and liver extracts from African patients (Bangui-Central African Republic), who died with this syndrome, into American woodchuck carriers of WHV (WC 231,144), the results of which were then compared with animals inoculated with a reference wild HDV strain (WC 300,173,154), and those which received material from a European fulminant HDV case (WC 88,93). RESULTS: Following the initial inoculation, the animals receiving African inocula had a delayed anti-HDV seroconversion, high mortality and showed the presence of spongiocytes, while the other animals had a classical evolution of HDV superinfection in woodchucks. Furthermore, the African inocula caused less inhibition of WHV replication, as well as a predominant cytoplasmic expression of HDAg, in contrast to the animals which received the other inocula. The second passage experiments gave similar results. CONCLUSIONS: We conclude that this peculiar form of HDV fulminant hepatitis can be experimentally reproduced and might be specifically related to a more pathogenic strain.

Animals↗
PubMed1995

DNA-based immunization with chimeric vectors for the induction of immune responses against the hepatitis C virus nucleocapsid.

Vectors expressing the first 58 amino acids of the hepatitis C virus (HCV) nucleocapsid alone or as a fusion protein with the middle (pre-S2 and S) or major (S) surface antigens of hepatitis B virus (HBV) were constructed. Intramuscular immunization of BALB/c mice with the chimeric constructs in the form of naked DNA elicited humoral responses to antigens from both viruses within 2 to 6 weeks postinjection. No anti-HCV responses were obtained in mice immunized with the vector expressing the HCV sequence in the nonfusion context. Sera from chimera-injected mice specifically recognized both HCV capsid and HBV surface antigens in enzyme-linked immunosorbent assay and immunoblot testing. Anti-HCV serum titers formed plateaus of approximately 1:3,000; these remained stable until the end of the study (18 weeks postinfection). Anti-HBV immune responses were found to be lower in the chimera-injected animals (< 200 mIU/ml) than in those immunized with the native HBV vector (> 2,000 mIU/ml). This is the first report of the use of DNA-based immunization for the generation of immune responses to an HCV protein. In addition, these findings show that it is possible to elicit responses to viral epitopes from two distinct viruses via DNA immunization with chimeric vectors.

Animals↗
PubMed1995

Characterization of the third most common genotype of hepatitis C virus in France.

We have previously identified the two major hepatitis C virus (HCV) genotypes prevalent in France (type I and type II). We report here the identification and partial characterization of a new HCV genotype with a highly divergent 5' noncoding (NC) region and a structural protein region. This genotype showed only 93-94% sequence identity with either type I or type II HCV in the 5' NC region. Sequence analysis of the structural protein region revealed extremely low sequence homology with all the four major HCV genotypes: 86-89% for the core protein and 56-69% for the envelope protein. However, further analysis revealed that this new genotype was very similar to the genotype 3a described most recently. Screening of 150 clinical samples with genotype-specific oligoprobes revealed prevalence of this genotype in 12% of the French samples with a significant association with drug addiction and a good response to interferon therapy. These results may have implications for the diagnosis of HCV infection and the design of HCV vaccines.

Amino Acid Sequence↗
PubMed1995

[Treatment of hepatitis C].

The treatment of hepatitis C virus (HCV) infections is essentially known for chronic hepatitis C and is mainly restricted to interferon alpha. Initial trials have indicated that around 50% of the patients with chronic hepatitis C respond to alpha interferon (administered at 3 MU, thrice weekly, during 6 months) by normalizing alanine aminotransferase at the end of therapy, although 25% were found to relapse after therapy. Normalization of biochemical tests is associated with an improvement in liver histological features and with decrease or loss of HCV from serum and liver. Response to therapy is influenced by both duration and dose levels of the treatment. Following studies which showed that higher doses and longer duration were more effective than the current recommendations of 3MU thrice weekly for 6 months have recently conducted to the recent recommendation of a 12 month course of therapy using 3 MU. The outcome of therapy was also shown to be negatively influenced by longer duration of disease and presence of cirrhosis. More recently, the critical role of virological markers has been emphasized with a lower rate of response in patients infected with the genotype 1 b and a high viral load. However, these factors do not certainly predict for an individual patient the quality of the response. Therapeutical goals are: to precisely define pre-treatment scores of response able to give each individual patient the optimal treatment regimen, non responders to interferon alpha and patients with a transient benefit of therapy. Thus, development of new treatments appears critical among which those with other interferons and above all the bitherapy using ribavirin and interferon alpha which may have a marked increase in efficacy in comparison with interferon alpha used as monotherapy.

Antiviral Agents↗
PubMed1994

Identification of the third major genotype of hepatitis C virus in France.

We have previously found type I and type II hepatitis C virus (HCV) as the predominant HCV genotypes in France. Here we report on the identification and partial characterization of a third major genotype there. This genotype showed only 93-94% sequence conservation to either type I or type II HCV in the 5' noncoding region. The point mutations changed the small open reading frames but not the proposed secondary structure of this region. Sequence of the structural protein region also differed significantly from other genotypes. The new genotype was found in 12% of HCV infections in France. Rapid method for the identification of this genotype was developed.

Amino Acid Sequence↗
PubMed1994

Detection of small and large genomes of hepatitis D virus in serum of patients with hepatitis D.

By combining the polymerase chain reaction (PCR) with restriction enzyme digestion technologies, we characterized the genomes for the small and large delta proteins of HDV in retrospective analysis of sera from 10 patients with varied clinical outcomes. Both small and large genomes of HDV were present in all 13 serum samples from the 6 acute and 4 chronic cases studied, while the specific HDV proteins (P24 and P27) could be detected by immunoblot analysis in only 4 of them. The relative amounts and ratios of the genomes for the large and the small proteins of HDV were different for each individual. The molecular ratio of large to small HDV genomes in serum correlated with viral replication. When the replication of HDV RNA increased, the ratio decreased and vice-versa. No specific correlation, however, was found between the ratio of both molecular forms and the clinical outcome.

Adolescent↗