Improvement of Sensitivity and Speed of Virus Sensing Technologies Using nm- and μm-Scale Components

Various viral diseases can be widespread and cause severe disruption to global society. Highly sensitive virus detection methods are needed to take effective measures to prevent the spread of viral infection. This required the development of rapid virus detection technology to detect viruses at low concentrations, even in the biological fluid of patients in the early stages of the disease or environmental samples. This review describes an overview of various virus detection technologies and then refers to typical technologies such as beads-based assay, digital assay, and pore-based sensing, which are the three modern approaches to improve the performance of viral sensing in terms of speed and sensitivity.

Expression and immunogenic analysis of recombinant polypeptides derived from capsid protein VP1 for developing subunit vaccine material against hepatitis A virus

Three recombinant polypeptides, VP1-His, VP1-3N-His, and 3D2-His, were produced by Escherichia coli expression system. Recombinant VP1-His, VP1-3N-His, and 3D2-His were expressed as bands with molecular weights of 32, 38, and 30 kDa, respectively. These were purified by affinity chromatography using Ni-NTA Fast-flow resin and/or ion-exchange chromatography using DEAE-Sepharose Fast-flow resin. Intraperitoneal immunizations of recombinant polypeptides successfully elicited the productions of VP1-His, VP1-3N-His, and 3D2-His specific IgG antibodies (IgG subclass distribution of IgG1>IgG2a>IgG2b>IgG3) in sera and induced the secretions of cytokines IFN-γ and IL-6 in spleen cells. Sera from recombinant VP1-His-, VP1-3N-His-, and 3D2-His-immunized mice neutralized the propagation of HAV. The highest neutralizing activity was shown in sera from recombinant VP1-3N-His-immunized mice. These results suggest that recombinant VP1-3N-His can be a useful source for developing hepatitis A virus (HAV) subunit vaccine candidates.

Diagnosis of hepatitis a virus infection: a molecular approach

Current serologic tests provide the foundation for diagnosis of hepatitis A and hepatitis A virus (HAV) infection. Recent advances in methods to identify and characterize nucleic acid markers of viral infections have provided the foundation for the field of molecular epidemiology and increased our knowledge of the molecular biology and epidemiology of HAV. Although HAV is primarily shed in feces, there is a strong viremic phase during infection which has allowed easy access to virus isolates and the use of molecular markers to determine their genetic relatedness. Molecular epidemiologic studies have provided new information on the types and extent of HAV infection and transmission in the United States. In addition, these new diagnostic methods have provided tools for the rapid detection of food-borne HAV transmission and identification of the potential source of the food contamination.

Antigenic epitopes of the hepatitis A virus polyprotein

Forty-two antigenic domains were identified across the hepatitis A virus (HAV) polyprotein by using a set of 237 overlapping 20-mer synthetic peptides spanning the entire HAV polyprotein and a panel of serum samples from acutely HAV-infected patients. The term "antigenic domain" is used in this study to define a protein region spanned with consecutive overlapping immunoreactive peptides. Nineteen antigenic domains were found within the structural proteins, and 22 were found within the nonstructural proteins, with 1 domain spanning the junction of VP1 and P2A proteins. Five of these domains were considered immunodominant, as judged by both the breadth and the strength of their immunoreactivity. One domain is located within the VP2 protein at position 57-90 aa. A second domain, located at position 767-842 aa, contains the C-terminal part of the VP1 protein and the entire P2A protein. A third domain, located at position 1403-1456 aa, comprises the C-terminal part of the P2C protein and the N-terminal half of the P3A protein. The fourth domain, located at position 1500-1519 aa, includes almost the entire P3B, and the last domain, located at position 1719-1764 aa, contains the C-terminal region of the P3C protein and the N-terminal region of the P3D protein. It is interesting to note that four of the five most immunoreactive domains are derived from small HAV proteins and/or encompass protein cleavage sites separating different HAV proteins. The HAV-specific immunoreactivity of each antigenically reactive peptide was confirmed by using seven HAV seroconversion panels. Collectively, these data demonstrate that HAV structural and nonstructural proteins contain antigenic epitopes that can be efficiently modeled with short synthetic peptides.

Type A viral hepatitis: epidemiology, diagnosis, and prevention

Hepatitis A virus (HAV) infection occurs worldwide and is an important cause of acute viral hepatitis in the US. In this review, I cover the epidemiology, course of infection, clinical manifestations, serological responses, and prevention of this infection. Although most patients completely recover from this disease, elderly patients have a substantial mortality risk. Recently licensed vaccines are highly efficacious.

Early appearance of neutralizing antibodies after vaccination with an inactivated hepatitis A vaccine

Sera from 30 subjects vaccinated with the Pasteur Merieux Serums & Vaccins (PM) inactivated hepatitis A vaccine, and from 30 subjects vaccinated with the Smithkline Beecham (SB) inactivated hepatitis A vaccine, were tested in two laboratories in order to provide comparative data on neutralizing activities of vaccine-induced antibodies. Sera were also evaluated by a modified radioimmunoassay (mRIA) and results were compared to neutralization assays results. Neutralizing antibody titres provided by the two laboratories correlated well (coefficient or correlation 0.42, P < 0.001). Neutralizing antibodies were detected after vaccination with both vaccines, and the kinetics of neutralizing antibody were the same with both vaccines. The titres gradually increased between the second week after the first dose and the post-booster dose (week 28). A strong booster effect of the booster vaccine dose on neutralizing titres was observed. Significantly higher neutralizing antibody titres with the PM vaccine were observed as early immune response on week 2 titres on both series of results. Vaccine-induced neutralizing antibody titres and vaccine-induced antibody mRIA titres correlated well (coefficient of correlation 0.82 and 0.72, respectively, P < 0.0001 in both cases). These results demonstrate early appearance of neutralizing antibody at high titre with the PM vaccine.

Size and conformational stability of the hepatitis A virus used to prepare VAQTA, a highly purified inactivated vaccine

A variety of biophysical techniques have been employed to examine the size and conformational integrity of highly purified hepatitis A virus (HAV) in solution (purified HAV particles are subsequently formalin-inactivated and adsorbed to aluminum salts for use as the vaccine VAQTA). The size of HAV particles was assessed by a combination of electron microscopy, sedimentation velocity, and dynamic light scattering. The effect of ionic strength and temperature on the overall conformational stability of HAV was determined by a combination of intrinsic HAV protein fluorescence, fluorescent probes of both RNA and protein, and UV-visible spectroscopy. A major structural change in HAV occurs near 60 degrees C with the addition of 0.2 M magnesium chloride enhancing the thermal stability of HAV by approximately 10 degrees C. Salt concentrations above 0.2 M, however, decrease the solubility of HAV. The effect of pH on the physical properties of HAV particles was monitored by dynamic light scattering, analytical size exclusion HPLC, and interaction with fluorescent dyes. HAV particles undergo a substantially reversible association/aggregation at pH values below 6 with the concomitant exposure of previously buried hydrophobic surfaces below pH 4. These results are in good agreement with previous studies of HAV thermal stability under extreme conditions in which the irreversible inactivation of the viral particles was measured primarily by the loss of viral infectivity. The wide variety of biophysical measurements described in this work, however, directly monitor structural changes as they occur, thus providing a molecular basis with which to monitor HAV stability during purification and storage.

Relative importance of the enterically transmitted human hepatitis viruses type A and E as a cause of foreign travel associated hepatitis

Hepatitis contracted during a stay abroad may be caused by a wide range of pathogens including viruses, bacteria, protozoa or helminths. In many cases, the etiological agent primarily infects other target organs and tissues, involving the liver either as part of a disseminated infection or secondarily to mechanical biliary tract obstruction. The article focuses on enterically transmitted hepatitis caused by the primarily hepatotropic human hepatitis viruses type A and E and discusses their importance in travel-related disease.

Immunogenicity and safety of a new inactivated hepatitis A vaccine in a comparative study

A multicentre, controlled, randomised, open, comparative trial including 839 healthy adult volunteers was carried out in order to compare the immunogenicity and reactogenicity of two vaccines against hepatitis A virus (HAV) during primary immunization and after booster injection. The first vaccine was produced by Pasteur Mérieux (PM), and the second vaccine by Smith-Kline Beecham (SKB). The vaccination schedule consisted of 2 doses (months 0, 6) for PM and 3 doses (months 0, 1, and 6) for SKB. Two weeks after the first dose, the seroconversion rates among initially HAV seronegative subjects (n = 608) were 93.4% and 76.1% for the PM and SKB vaccines, respectively, the corresponding geometric mean titres (GMTs) were 59.0 mIU/ml versus 30.8 mlU/ml (modified RIA HAVAB assay, Abbott Laboratories). Two months after the beginning of immunization (one dose versus two doses) the GMTs were 138.4 and 161.6 mlU/ml, respectively. At month 7, the seroconversion rates were 100% for both vaccines, and the GMTs were 4,189 and 3,163 mlU/ml, respectively. After the first dose of vaccine, 24.6% and 19.6% of the PM and SKB vaccines reported local reactions. The rates for systemic reactions were 27.2% and 25.0%, respectively. Lower rates for local and systemic reactions were seen after booster injections and statistical differences were not observed between the two vaccines. The study also demonstrated that vaccination was as well tolerated in subjects with anti-HAV antibodies as in HAV seronegative subjects. Logistic regression analysis revealed a significant vaccine effect on seroconversion rates only at week 2 (P < 10(-4). The same conclusions were drawn from the analysis of GMT by multivariate regression.(ABSTRACT TRUNCATED AT 250 WORDS)

Good immunogenicity of GBM strain inactivated hepatitis A vaccine in healthy male adults

A formalin-inactivated aluminium hydroxide adsorbed hepatitis A vaccine was evaluated in a dose-response study on 195 healthy male adults (age range: 18-31 years) in two French hospitals (Lyon, Rouen). Four doses (20, 40, 80, 160 RIA antigen units) were administered intramuscularly (i.m.) in two injections over a 6-month period. At the time of the first vaccine injection, 32 subjects (16.4%) were found positive (> 20 mIU ml-1) for HAV antibody (total Ig RIA HAVAB assay, Abbott Laboratories) and were excluded from the analysis of immunogenicity criteria. Fourteen days after the first vaccine injection, 78.1% (95% confidence interval (CI): 62-90) of seronegative subjects who received the 160 RIA antigen unit dose seroconverted with a geometric mean titre (GMT) of 43 mIU ml-1 (95% CI: 33-56). Seroconversion was 100% (95% CI: 91-100) at 1 month with a GMT of 95 mIU ml-1 (95% CI: 79-112). Statistical analysis revealed a significant dose-related effect (p < 0.0001) on GMT by multivariate regression analysis of the results after the first injection. Biological safety was evaluated and alanine aminotransferase and aspartate aminotransferase levels were similar prior to and 14 days after the first injection in the four groups. Reactions after injection were similar in the four dosage groups: 6.2% of subjects reported immediate reactions after first vaccination (feeling sick, spontaneous pain, headache), 8.9% reported local reactions at the site of injection (spontaneous pain, haematoma, local adenopathy) and 13.5% reported general reactions ('flu-like' syndrome, gastrointestinal tract disorders, fatigue, headache).(ABSTRACT TRUNCATED AT 250 WORDS)

Artificial mosaic protein containing antigenic epitopes of hepatitis E virus

A synthetic gene encoding an artificial polypeptide composed of antigenic epitopes of the hepatitis E virus (HEV) proteins was constructed from short oligodeoxyribonucleotides by using PCR. The polypeptide comprises a mosaic of three antigenically active dominant regions from the protein encoded by open reading frame 2 (ORF2), one antigenically active region from the protein encoded by ORF3 of the Burmese HEV strain, and one antigenically active region from the protein encoded by ORF3 of the Mexican HEV strain. The mosaic protein was expressed in Escherichia coli as a chimera with glutathione S-transferase or beta-galactosidase. Guinea pig sera containing antibodies to the corresponding HEV synthetic peptides were used to demonstrate by Western immunoblot analysis and enzyme immunoassay the presence and accessibility of all HEV-specific antigenic epitopes introduced into the mosaic protein. Both the glutathione S-transferase and beta-galactosidase hybrid proteins were analyzed by using a panel of human anti-HEV-positive and -negative sera. The data obtained strongly indicate a diagnostic potential for the mosaic protein.

Current seroepidemiological status of hepatitis A with a comparison of antibody titers after infection and vaccination

The overall prevalence of anti-hepatitis A virus antibodies was 49.6% in 385 inhabitants in Honda City, Japan in 1991. An approximately 50% prevalence rate occurred between 40 and 49 years of age. The prevalence of anti-HAV antibodies was significantly lower in 1991 than in 1982 in the age groups 20 to 29 years and 30 to 39 years (p < 0.01), suggesting there has been no significant HAV infection since 1982. In addition, anti-HAV antibody titers of sera from convalescent hepatitis. A patients were compared with those from seropositive healthy subjects and from healthy subjects following administration of a lyophilized inactivated hepatitis A vaccine or immune serum globulin. Titers after vaccine administration were considerably higher than after immune serum globulin and, although lower than those obtained after natural infection, should be sufficient for protection against hepatitis A virus.

Rapid and efficient purification of hepatitis A virus from cell culture

Hepatitis A virus (HAV) characteristically remains strongly cell-associated when grown in culture, with only small yields in the culture supernatant. Cell factories (6000 cm2) of BS-C-1 cells infected with the cytopathic HM175A.Z strain of HAV for 3, 4 or 7 days were harvested using trypsin to disperse the infected cell monolayer, and cells were collected by low speed centrifugation. More than 70% of the yield of virus and viral antigen can thus be obtained in the packed cell pellet. Packed cell pellets were resuspended in 5 volumes of isotonic buffer and cell membranes lysed by the addition of a non-ionic detergent. After removal of nuclei by centrifugation, ionic detergent was added to the clarified cytoplasmic extract. Under these conditions, HAV particles (virions and empty capsids) are the only particulate material remaining in the sample, and were recovered in a single ultracentrifugation step through discontinuous sucrose/glycerol density gradients. In one day, this method yields viral antigen with minimal cellular contaminants, in a concentrated volume suitable for subsequent biochemical, vaccine or diagnostic uses. The yield of viral antigen over numerous batches varied from 200 to 1600 vaccine-equivalent doses per cell factory, with a titre of up to 1 x 10(10) infectious particles per ml.