Prevalence of serum neutralizing antibodies against chimpanzee adenovirus 63 and human adenovirus 5 in Kenyan children, in the context of vaccine vector efficacy

Vaccination against Plasmodium falciparum malaria could reduce the worldwide burden of this disease, and decrease its high mortality in children. Replication-defective recombinant adenovirus vectors carrying P. falciparum epitopes may be useful as part of a vaccine that raises cellular immunity to the pre-erythrocytic stage of malaria infection. However, existing immunity to the adenovirus vector results in antibody-mediated neutralization of the vaccine vector, and reduced vaccine immunogenicity. Our aim was to examine a population of children who are at risk from P. falciparum malaria for neutralizing immunity to replication-deficient recombinant chimpanzee adenovirus 63 vector (AdC63), compared to human adenovirus 5 vector (AdHu5). We measured 50% and 90% vector neutralization titers in 200 individual sera, taken from a cohort of children from Kenya, using a secreted alkaline phosphatase neutralization assay. We found that 23% of the children (aged 1-6 years) had high-titer neutralizing antibodies to AdHu5, and 4% had high-titer neutralizing antibodies to AdC63. Immunity to both vectors was age-dependent. Low-level neutralization of AdC63 was significantly less frequent than AdHu5 neutralization at the 90% neutralization level. We conclude that AdC63 may be a useful vector as part of a prime-boost malaria vaccine in children.

A novel chimpanzee serotype-based adenoviral vector as delivery tool for cancer vaccines

The use of adenovirus (Ad) as vaccine vectors is hindered by pre-existing immunity to human Ads in most of the human population. In order to overcome this limitation, uncommon alternative Ad serotypes need to be utilized. In this study, an E1-E3 deleted recombinant Ad based on the chimpanzee serotype 3 (ChAd3) was engineered to express human carcinoembryonic antigen (CEA) protein or rat neu extracellular/transmembrane domains (ECD.TM). ChAd3 vectors were tested in CEA transgenic (CEA.Tg) and BALB/NeuT mice, which show immunologic tolerance to these antigens. ChAd3 is capable of inducing an immune response comparable to that of hAd5 serotype-based vectors, thus breaking tolerance to tumor associated antigens (TAAs) and achieving anti-tumor effects. Of importance is that ChAd3 can overcome hAd5 pre-existing immunity and work in conjunction with DNA electroporation (DNA-EP) and other Ad vaccines based on common human serotypes.

Influence of specific CD4+ T cells and antibodies on evolution of hypervariable region 1 during acute HCV infection

BACKGROUND/AIMS

Several studies suggest that the evolutionary rate of HVR1 sequence in acute HCV hepatitis derives from the action of a continuous immune-driven positive selection. However, these studies have not been performed examining the relationship between HVR1 evolution and the development of specific immunity to autologous HVR1 sequences.

METHODS

We performed a longitudinal analysis of HVR1 sequences and specific antibodies and CD4+ T cells in ten HCV acutely infected patients with different clinical outcomes (recovery versus persistence).

RESULTS

We showed that although both recovered and chronically evolving individuals developed IFN-gamma+ T cells specific for Core and NS sequences, HVR1-specific CD4+ T cells were detected only in patients clearing the virus. On the contrary, all patients displayed anti-HVR1 antibodies that recognized sequences exclusively carried by autologous viruses. Measurements of genetic diversity and the number of non-synonymous per synonymous substitutions within HVR1 sequences before and after antibody appearance showed an increase of these parameters only in concomitance with the appearance of anti-HVR1 antibodies.

CONCLUSIONS

The evidence that anti-HVR1 antibodies favor HVR1 variant selection suggests that viral complexity in chronically infected patients could represent a virus adaptive strategy to escape the continuous selective process mediated by anti-HVR1 antibodies.

Differential screening of phage-ab libraries by oligonucleotide microarray technology

A novel and efficient tagArray technology was developed that allows rapid identification of antibodies which bind to receptors with a specific expression profile, in the absence of biological information. This method is based on the cloning of a specific, short nucleotide sequence (tag) in the phagemid coding for each phage-displayed antibody fragment (phage-Ab) present in a library. In order to set up and validate the method we identified about 10,000 different phage-Abs binding to receptors expressed in their native form on the cell surface (10 k Membranome collection) and tagged each individual phage-Ab. The frequency of each phage-Ab in a given population can at this point be inferred by measuring the frequency of its associated tag sequence through standard DNA hybridization methods. Using tiny amounts of biological samples we identified phage-Abs binding to receptors preferentially expressed on primary tumor cells rather than on cells obtained from matched normal tissues. These antibodies inhibited cell proliferation in vitro and tumor development in vivo, thus representing therapeutic lead candidates.

High-resolution ultrasonography (HRUS) of the meniscal cyst of the knee: our experience

PURPOSE

This study was undertaken to assess the diagnostic accuracy of high-resolution ultrasonography (HRUS) in the detection of meniscal cysts.

MATERIALS AND METHODS

Over a 2-year period, 1,857 patients underwent magnetic resonance imaging (MRI) of the knee for traumatic or degenerative disorders. All patients with MRI evidence of a meniscal cyst were studied by HRUS. HRUS was also performed on an equal number of patients without MRI evidence of meniscal cyst who were used as a control group. All HRUS examinations were conducted by a radiologist blinded to the MRI findings. Sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of HRUS were assessed with reference to MRI. All patients underwent surgery, and the resected masses were studied by histological examination.

RESULTS

MRI allowed identification of a meniscal cyst in 52 patients. HRUS enabled correct detection of the meniscal cyst in 49/52 cases. In the control group, HRUS excluded the presence of meniscal cysts in all cases. HRUS had a sensitivity, specificity, PPV and NPV of 94.23%, 100%, 100% and 94.54%, respectively, for the detection of meniscal cysts.

CONCLUSIONS

HRUS is a fairly reliable technique in the detection, characterisation and differentiation of the different forms of meniscal cyst.

High-avidity monoclonal antibodies against the human scavenger class B type I receptor efficiently block hepatitis C virus infection in the presence of high-density lipoprotein

The human scavenger class B type 1 receptor (SR-B1/Cla1) was identified as a putative receptor for hepatitis C virus (HCV) because it binds to soluble recombinant HCV envelope glycoprotein E2 (sE2). High-density lipoprotein (HDL), a natural SR-B1 ligand, was shown to increase the in vitro infectivity of retroviral pseudoparticles bearing HCV envelope glycoproteins and of cell culture-derived HCV (HCVcc), suggesting that SR-B1 promotes viral entry in an HDL-dependent manner. To determine whether SR-B1 participates directly in HCV infection or facilitates HCV entry through lipoprotein uptake, we generated a panel of monoclonal antibodies (MAbs) against native human SR-B1. Two of them, 3D5 and C167, bound to conformation-dependent SR-B1 determinants and inhibited the interaction of sE2 with SR-B1. These antibodies efficiently blocked HCVcc infection of Huh-7.5 hepatoma cells in a dose-dependent manner. To examine the role of HDL in SR-B1-mediated HCVcc infection, we set up conditions for HCVcc production and infection in serum-free medium. HCVcc efficiently infected Huh-7.5 cells in the absence of serum lipoproteins, and addition of HDL led to a twofold increase in infectivity. However, the HDL-induced enhancement of infection had no impact on the neutralization potency of MAb C167, despite its ability to inhibit both HDL binding to cells and SR-B1-mediated lipid transfer. Of note, MAb C167 also potently blocked Huh-7.5 infection by an HCV strain recovered from HCVcc-infected chimpanzees. These results demonstrate that SR-B1 is essential for infection with HCV produced in vitro and in vivo and suggest the possible use of anti-SR-B1 antibodies as therapeutic agents.

Modulation of the immune response induced by gene electrotransfer of a hepatitis C virus DNA vaccine in nonhuman primates

Induction of multispecific, functional CD4+ and CD8+ T cells is the immunological hallmark of acute self-limiting hepatitis C virus (HCV) infection in humans. In the present study, we showed that gene electrotransfer (GET) of a novel candidate DNA vaccine encoding an optimized version of the nonstructural region of HCV (from NS3 to NS5B) induced substantially more potent, broad, and long-lasting CD4+ and CD8+ cellular immunity than naked DNA injection in mice and in rhesus macaques as measured by a combination of assays, including IFN-gamma ELISPOT, intracellular cytokine staining, and cytotoxic T cell assays. A protocol based on three injections of DNA with GET induced a substantially higher CD4+ T cell response than an adenovirus 6-based viral vector encoding the same Ag. To better evaluate the immunological potency and probability of success of this vaccine, we have immunized two chimpanzees and have compared vaccine-induced cell-mediated immunity to that measured in acute self-limiting infection in humans. GET of the candidate HCV vaccine led to vigorous, multispecific IFN-gamma+CD8+ and CD4+ T lymphocyte responses in chimpanzees, which were comparable to those measured in five individuals that cleared spontaneously HCV infection. These data support the hypothesis that T cell responses elicited by the present strategy could be beneficial in prophylactic vaccine approaches against HCV.

Early impairment of hepatitis C virus specific T cell proliferation during acute infection leads to failure of viral clearance

BACKGROUND AND AIMS

Cellular mediated immunity (CMI) is thought to play a key role in resolution of primary hepatitis C virus (HCV) infection. However, CD4+ and CD8+ T cell responses are also generated during acute infection in individuals who become chronic, suggesting that they developed a defective CMI. The aim of this study was to verify if and when such immune dysfunction is established by measuring the breadth, magnitude, function, and duration of CMI in a large cohort of subjects during the natural course of acute HCV infection.

METHODS

CMI was comprehensively studied by prospective sampling of 31 HCV acutely infected subjects enrolled at the onset of infection and followed for a median period of one year.

RESULTS

Our results indicated that while at the onset of acute HCV infection a measurable CMI with effector function was detected in the majority of subjects, after approximately six months less than 10% of chronically infected individuals displayed significant CMI compared with 70% of subjects who cleared the virus. We showed that progressive disappearance of HCV specific T cells from the peripheral blood of chronic patients was due to an impaired ability to proliferate that could be rescued in vitro by concomitant exposure to interleukin 2 and the antigen.

CONCLUSION

Our data provide evidence of strong and multispecific T cell responses with a sustained ability to proliferate in response to antigen stimulation as reliable pharmacodynamic measures of a protective CMI during acute infection, and suggest that early impairment of proliferation may contribute to loss of T cell response and chronic HCV persistence.

Hepatitis C virus carriers with persistently normal ALT levels: biological peculiarities and update of the natural history of liver disease at 10 years

Some chronic hepatitis C (CHC) patients exhibit persistently normal alanine aminotransferase (ALT) levels (PNAL). Patients with PNAL experience significantly milder disease. In order to understand the differences between CHC patients with elevated ALT levels compared with those with PNAL better, we compared epidemiological, immunological and histological findings, in particular, the value of proliferating hepatocyte activity (PCNA) between the two groups of patients. We studied 40 chronic hepatitis C virus (HCV) carriers with increased ALT who underwent liver biopsy for histological diagnosis and determination of clinical prognosis, and 24 PNAL patients under follow-up for 10 years. Immunological response to different HCV genomic epitopes was tested in both the control group and in PNAL subjects. PCNA values from liver specimens of all patients as well as liver biopsies of PNAL patients at time points 0 and 5 years were calculated according to Hall et al.Age, sex and body mass index (BMI) were not significantly different between the two groups. The median liver histology stage was significantly higher in HCV carriers vs the PNAL group (2.5, range = 2-6 vs 1.5, range = 1-2; P < 0.01). Among PNAL patients, histological stage was not statistically different at the three time points considered. Interferon (IFN)-gamma production was comparable in the two groups. PCNA was significantly higher in the group with elevated ALT levels vs the PNAL group (8%, range = 4-15%vs 5% range = 3-8%; P < 0.05) and no statistically significant differences were found in PNAL patients at time points 0, 5 and 10 years. This study confirms that progression to cirrhosis is slow or absent in PNAL patients after 10 years of follow-up. Accordingly, the hepatic proliferative activity index is low and seems to be stable over time.

Efficient immunization of rhesus macaques with an HCV candidate vaccine by heterologous priming-boosting with novel adenoviral vectors based on different serotypes

Efficient vaccination against viral agents requires a strong T-cell-mediated immune response to clear viral-infected cells. Optimal vaccination can be achieved by administration of recombinant viral vectors encoding phatogen antigens. Adenoviral vectors have attracted considerable attention as potential viral vectors for genetic vaccination owing to their favorable safety profile and potent transduction efficiency following intramuscular injection. However, the neutralizing antibody response against adenoviral capsid proteins following adenoviral vectors injection limits the success of vaccination protocols based on multiple administrations of the same adenoviral serotype. In this work, we describe efficient immunization of rhesus macaques, the preferred model for preclinical assessment, with an HCV candidate vaccine by heterologous priming-boosting with adenoviral vectors based on different serotypes. The induced responses are broad and show significant cross-strain reactivity. Boosting can be delayed for over 2 years after priming, indicating that there is long-term maintenance of resting memory cells.

A T-cell HCV vaccine eliciting effective immunity against heterologous virus challenge in chimpanzees

Three percent of the world's population is chronically infected with the hepatitis C virus (HCV) and at risk of developing liver cancer. Effective cellular immune responses are deemed essential for spontaneous resolution of acute hepatitis C and long-term protection. Here we describe a new T-cell HCV genetic vaccine capable of protecting chimpanzees from acute hepatitis induced by challenge with heterologous virus. Suppression of acute viremia in vaccinated chimpanzees occurred as a result of massive expansion of peripheral and intrahepatic HCV-specific CD8(+) T lymphocytes that cross-reacted with vaccine and virus epitopes. These findings show that it is possible to elicit effective immunity against heterologous HCV strains by stimulating only the cellular arm of the immune system, and suggest a path for new immunotherapy against highly variable human pathogens like HCV, HIV or malaria, which can evade humoral responses.

A novel adenovirus type 6 (Ad6)-based hepatitis C virus vector that overcomes preexisting anti-ad5 immunity and induces potent and broad cellular immune responses in rhesus macaques

Success in resolving hepatitis C virus (HCV) infection has been correlated to vigorous, multispecific, and sustained CD8(+) T-cell response in humans and chimpanzees. The efficacy of inducing T-cell-mediated immunity by recombinant serotype 5 adenovirus vector has been proven in many animal models of infectious diseases, but its immunogenicity can be negatively influenced by preexisting immunity against the vector itself. To evaluate the less prevalent adenovirus serotype 6 (Ad6) as an alternative vector for and HCV vaccine development, we have generated serotype 5 and 6 adenoviral vectors directing expression of the nonstructural region of HCV (MRKAd5-NSmut and MRKAd6-NSmut). Immunogenicity studies in mice showed that the two vectors induced comparable T-cell responses but that only MRKAd6-NSmut was not suppressed in the presence of anti-Ad5 immunity. In contrast, preexisting anti-Ad5 immunity dramatically blunted the immunogenicity of the serotype 5-based HCV vector. Furthermore, MRKAd6-NSmut showed equivalent potency, breadth, and longevity of HCV-specific T-cell responses in rhesus macaques as the corresponding Ad5-based vector over a wide range of doses and was capable of boosting DNA-primed animals even if administered at low doses. These data support the use of the MRKAd6-NSmut for anti-HCV immunotherapy and, more generally, for the Ad6 serotype as a better genetic vaccine vehicle than Ad5.

Positive selection of cytotoxic T lymphocyte escape variants during acute hepatitis C virus infection

Cellular immune responses are induced during hepatitis C virus (HCV) infection and acute-phase CD8+ T cells are supposed to play an important role in controlling viral replication. In chimpanzees, failure of CD8+ T cells to control HCV replication has been associated with acquisition of mutations in MHC class I-restricted epitopes. In humans, although selection of escape mutations in an immunodominant CTL epitope has been recently described, the overall impact of immune escape during acute HCV infection is unclear. Here, by performing an in depth analysis of the relationship between early cellular immune responses and viral evolution in a chronically evolving HCV acutely infected individual, we demonstrate: (i) the presence of a potent and focused CD8(+ T cell response against a novel epitope in the NS3 protein, (ii) the elimination of the quasi-species harboring the original amino acid sequence within this epitope, and (iii) the selection for a virus population bearing amino acid changes at a single residue within the cytotoxic T cell epitope that strongly diminished T cell recognition. These results support the view that acute-phase CD8+ T cell responses exert a biologically relevant pressure on HCV replication and that viruses escaping this host response could have a significant survival advantage.

Exposure to hepatitis C virus induces cellular immune responses without detectable viremia or seroconversion

Sporadic cases of cell-mediated immunity (CMI) in persons exposed to hepatitis C (HCV) but evidently uninfected have been reported. To further define this, we measured CMI in individuals without evidence of HCV infection, that is, negative for HCV-antibodies (anti-HCV) and RNA, residing in a rural Egyptian community where prevalence of anti-HCV was 24%. Cell-mediated immunity (CMI) measured by interferon-gamma (IFN-gamma) enzyme-linked immunospot (ELISPOT) assay, confirmed by intracellular staining using flow cytometry, against HCV peptides was measured in seronegative individuals with high-risk (HR) and low-risk (LR) exposures to HCV. Thirteen of 71 (18.3%) HR subjects but only 1 of 35 (2.9%) LR subjects had detectable CMI (P = 0.032). These data are compatible with the hypothesis that exposures to HCV may lead to development of HCV-specific CMI without anti-HCV and ongoing viral replication. We speculate induced CMI clears HCV sometimes when anti-HCV is not detectable, and HCV-specific CMI is a useful surrogate marker for exposure to HCV.

An adenovirus type 5 (Ad5) amplicon-based packaging cell line for production of high-capacity helper-independent deltaE1-E2-E3-E4 Ad5 vectors

Production of multiply deleted adenoviral (Ad) vectors with increased cloning capacity and reduced immunogenicity to adenovirus gene products requires the concomitant generation of efficient packaging cell lines. High expression levels of the complementing genes must be achieved in a coordinated fashion with viral replication. This is a particularly difficult task in light of the significant cytotoxicity displayed by adenoviral proteins. To this end, we developed a novel adenovirus-based amplicon with an Epstein-Barr virus origin of replication, Ad type 5 (Ad5) inverted terminal repeats, all Ad5 early region 2 (E2) genes, and the early region 4 (E4) open reading frame 6 (ORF6) under the control of a tetracycline-dependent promoter. The amplicon (pE2) was stably maintained in multiple copies in the nuclei of 293 cells stably expressing the Epstein-Barr virus nuclear antigen 1 (EBNA1) and allowed replication as a linear DNA upon induction of E2 and ORF6 gene expression. A stable cell line (2E2) was generated by introducing pE2 into 293EBNATet cells expressing the tetracycline-dependent transcriptional silencer and the reverse Tet transactivator (rtTA2). Upon induction with doxicycline, 2E2 cells produced higher levels of polymerase, precursor terminal protein (pTP), and DNA binding protein than noninduced 2E2 cells infected with first-generation Ad5 vector and supported efficient amplification of a multiply deleted Ad5 vector lacking E1, E2, E3, and E4 genes (Ad5DeltaE(1-4)). The high cloning capacity of Ad5DeltaE(1-4) (up to 12.6 kb) was exploited to construct a vector encoding the entire hepatitis C virus (HCV) polyprotein. Infection of HeLa cells by the resulting vector showed high levels of correctly processed HCV proteins.

MR findings in lipoma arborescens of the knee: our experience

PURPOSE

This paper describes the role of MR imaging in the identification of the different macroscopic patterns of lipoma arborescens.

MATERIALS AND METHODS

Between June 1995 and January 2004, a total of 6387 MR examinations of the knee were retrospectively assessed for the presence of lipoma arborescens. The MR examinations were performed using a superconductive 0.5 T MR unit with a transmitting/ receiving coil dedicated for the extremities. The MR images were acquired with SE T1-weighted, GE T2-weighted and STIR sequences in sagittal, coronal and axial planes with 3-mm thickness and 1-mm gap.

RESULTS

Lipoma arborescens was identified in 9 patients (mean age: 36 years). In 2/9 cases a localized lipoma arborescens was detected as a well-marginated single nodule on the suprapatellar bursa without irregularity or synovial hyperplasia. In the remaining 7 cases diffuse lipoma arborescens was identified on the wall of the suprapatellar bursa. In one case of diffuse lipoma arborescens there was involvement of both knees. In all cases the MR findings were verified at surgery and the final diagnosis was made by histological examination.

CONCLUSIONS

MR imaging shows a high accuracy in the identification and characterization of lipoma arborescens, due to its multiplanar capabilities and high contrast resolution. MRI allows correct evaluation of size and grade, accurate treatment planning and effective follow-up, avoiding the need for synovial biopsy.

In vivo DNA gene electro-transfer: a systematic analysis of different electrical parameters

BACKGROUND

Intramuscular plasmid injection followed by electroporation is an efficient method for gene therapy or vaccination. Several protocols have been described that give good transduction levels with several reporter genes.

METHODS

In this work we have explored the efficiency of gene delivery upon variation of the different electrical parameters such as pulse length frequency and voltage monitoring both on short- and long-term protein production.

RESULTS

Having defined the best performing parameters, we have designed a short electric treatment that gives good levels of plasmid-encoded protein in different species such as mice, rabbits and monkeys.

Multispecific T cell response and negative HCV RNA tests during acute HCV infection are early prognostic factors of spontaneous clearance

BACKGROUND/AIMS

Hepatitis C virus (HCV) infection results in a high frequency of chronic disease. The aim of this study was to identify early prognostic markers of disease resolution by performing a comprehensive analysis of viral and host factors during the natural course of acute HCV infection.

METHODS

The clinical course of acute hepatitis C was determined in 34 consecutive patients. Epidemiological and virological parameters, as well as cell mediated immunity (CMI) and distribution of human leukocyte antigens (HLA) alleles were analysed.

RESULTS

Ten out of 34 patients experienced self-limiting infection, with most resolving patients showing fast kinetics of viral clearance: at least one negative HCV RNA test during this phase predicted a favourable outcome. Among other clinical epidemiological parameters measured, the self-limiting course was significantly associated with higher median peak bilirubin levels at the onset of disease, and with the female sex, but only the latter parameter was independently associated after multivariate analysis. No significant differences between self-limiting or chronic course were observed for the distribution of DRB1 and DQB1 alleles. HCV specific T cell response was more frequently detected during acute HCV infection, than in patients with chronic HCV disease. A significantly broader T cell response was found in patients with self-limiting infection than in those with chronic evolving acute hepatitis C.

CONCLUSION

The results suggest that host related factors, in particular sex and CMI, play a crucial role in the spontaneous clearance of this virus. Most importantly, a negative HCV RNA test and broad CMI within the first month after onset of the symptoms represent very efficacious predictors of viral clearance and could thus be used as criteria in selecting candidates for early antiviral treatment.

Riluzole restores motor activity in rats with post-traumatic peripheral neuropathy

Riluzole is a presynaptic inhibitor of glutamate release with neuroprotective properties. In order to evaluate the effects of riluzole on motor activity in post-traumatic peripheral neuropathy (PTPN), the sciatic nerve of Wistar male rats was exposed monolaterally and subjected to crushing for one min by a surgical forceps. Animals received an intraperitoneal treatment with riluzole (2, 4 or 8 mg/kg per day), diclofenac (5, 10 or 20 mg/kg) or with vehicle for 3 days. Motor activity and coordination was evaluated in a circular open field and in the rotorod test. The treatment with riluzole stimulated ambulation in PTPN rats and improved their motor performance and coordination. The effect of treatment with riluzole on locomotor activity was greater than that of treatment with diclofenac and was dose-dependent. Furthermore, in contrast to vehicle- and diclofenac-treated rats, animals treated with riluzole showed a long-lasting improvement of locomotor activity as it was assessed 7 days after the end of treatment. These findings suggest that riluzole may improve motor performance in PTPN, and this does not depend on its antinociceptive activity. Its neuroprotective properties are possibly involved in this effect.