Replication of human rotavirus in cell culture

Significantly Longer Shedding of Norovirus Compared to Rotavirus and Adenovirus in Children with Acute Gastroenteritis

Worldwide, acute gastroenteritis (AGE) is a major cause of morbidity and mortality in children under 5 years of age. Viruses, including norovirus, rotavirus, and enteric adenovirus, are the leading causes of pediatric AGE. In this prospective cohort study, we investigated the viral load and duration of shedding of norovirus, rotavirus, and adenovirus in stool samples collected from 173 children (median age: 15 months) with AGE who presented to emergency departments (EDs) across Canada on Day 0 (day of enrollment), and 5 and 28 days after enrollment. Quantitative RT-qPCR was performed to assess the viral load. On Day 0, norovirus viral load was significantly lower compared to that of rotavirus and adenovirus (p < 0.001). However, on Days 5 and 28, the viral load of norovirus was higher than that of adenovirus and rotavirus (p < 0.05). On Day 28, norovirus was detected in 70% (35/50) of children who submitted stool specimens, while rotavirus and adenovirus were detected in 52.4% (11/24) and 13.6% (3/22) of children (p < 0.001), respectively. Overall, in stool samples of children with AGE who presented to EDs, rotavirus and adenovirus had higher viral loads at presentation compared to norovirus; however, norovirus was shed in stool for the longest duration.

Ensuring Viral Safety of Equine Immunoglobulins during Production

Equine blood plasma/serum and intermediates must be monitored for the presence of live viruses pathogenic in humans during production of equine immunoglobulins. Information concerning low-cost and simple methods for the detection of live horse viruses pathogenic and non-pathogenic to humans was gained using data of modern domestic and foreign literature. These methods are based on cultivation of these viruses on sensitive biosystems. The presented information can be used to set up blood plasma/serum control of horses at different stages of immunoglobulin production, i.e., when taking blood from horses during their quarantine period, when collecting blood from immunized horses, and before bottling the medicinal intermediate in the primary package.

Reverse Genetics Approach for Developing Rotavirus Vaccine Candidates Carrying VP4 and VP7 Genes Cloned from Clinical Isolates of Human Rotavirus

Species A rotaviruses (RVs) are a leading cause of severe acute gastroenteritis in infants and children younger than 5 years. Currently available RV vaccines were adapted from wild-type RV strains by serial passage of cultured cells or by reassortment between human and animal RV strains. These traditional methods require large-scale screening and genotyping to obtain vaccine candidates. Reverse genetics is a tractable, rapid, and reproducible approach to generating recombinant RV vaccine candidates carrying any VP4 and VP7 genes that provide selected antigenicity. Here, we developed a vaccine platform by generating recombinant RVs carrying VP4 (P[4] and P[8]), VP7 (G1, G2, G3, G8, and G9), and/or VP6 genes cloned from human RV clinical samples using the simian RV SA11 strain (G3P[2]) as a backbone. Neutralization assays using monoclonal antibodies and murine antisera revealed that recombinant VP4 and VP7 monoreassortant viruses exhibited altered antigenicity. However, replication of VP4 monoreassortant viruses was severely impaired. Generation of recombinant RVs harboring a chimeric VP4 protein for SA11 and human RV gene components revealed that the VP8* fragment was responsible for efficient infectivity of recombinant RVs. Although this system must be improved because the yield of vaccine viruses directly affects vaccine manufacturing costs, reverse genetics requires less time than traditional methods and enables rapid production of safe and effective vaccine candidates.IMPORTANCE Although vaccines have reduced global RV-associated hospitalization and mortality over the past decade, the multisegmented genome of RVs allows reassortment of VP4 and VP7 genes from different RV species and strains. The evolutionary dynamics of novel RV genotypes and their constellations have led to great genomic and antigenic diversity. The reverse genetics system is a powerful tool for manipulating RV genes, thereby controlling viral antigenicity, growth capacity, and pathogenicity. Here, we generated recombinant simian RVs (strain SA11) carrying heterologous VP4 and VP7 genes cloned from clinical isolates and showed that VP4- or VP7-substituted chimeric viruses can be used for antigenic characterization of RV outer capsid proteins and as improved seed viruses for vaccine production.

Prevalence of rotavirus genotypes in South Korea in 1989-2009: implications for a nationwide rotavirus vaccine program

The epidemiology of human group A rotavirus was analyzed by examining genotypic data acquired from 1989 to 2009 in South Korea. This information was derived from all the available published articles on rotavirus studies in South Korea, retrieved from both the PubMed and KoreaMed databases. Four common G types (G1, G2, G3, and G4) and three common P types (P[8], P[4], and P[6]) accounted for approximately 93% and 99% of the rotavirus reports, respectively. The G9 type was frequently detected after 2000, and because of this prevalence, it is considered to be the fifth most important G type rotavirus after the G1.G4 genotypes. Less common G types of the virus such as G12, G11, and G10 were detected in some geographic settings, and it is important to consider the context of these subtypes and their epidemiological significance. The P[9] virus genotype was observed in the study and has been discussed in many other studies; however, the P[3], P[10] and P[25] genotypes were rarely detected in the epidemiological research. In general, the distributions of the G and P genotypes showed temporal and geographical fluctuations, and a nationwide rotavirus vaccine program that targeted these genotypes demonstrated effectiveness in protecting against the circulating rotavirus strains. However, further analysis is needed to determine the true long-term effectiveness of these vaccines; the analysis should also consider the unexpected effects of vaccinations, such as vaccine-induced diseases, herd immunity, and changes in host susceptibilities.

Detection and quantitation of infectious human adenoviruses and JC polyomaviruses in water by immunofluorescence assay

Human adenoviruses (HAdV) and JC polyomaviruses (JCPyV) have been proposed as markers of fecal/urine contamination of human origin. An indirect immunofluorescence assay has been developed to quantify infectious human adenoviruses types 2 and 41 and JC polyomaviruses strain Mad-4 in water samples. The immunofluorescence assay was compared with other quantitative techniques used commonly such as plaque assay, tissue culture infectious dose-50 and quantitative PCR (qPCR). The immunofluorescence assays showed to be specific for the detection of infectious viruses, obtaining negative results when UV or heat-inactivated viruses were analyzed. The assays required less time and showed higher sensitivity for the detection of infectious viral particles than other cell culture techniques (1 log(10) more) evaluated. River water samples spiked previously with human adenoviruses and raw sewage samples were also analyzed using the proposed immunofluorescence assay as well as by qPCR. The results show quantitations with 2 log(10) reduction in the numbers of infectious viruses compared with the number of genome copies detected by qPCR. The immunofluorescence assay developed is fast, sensitive, specific, and a standardizable technique for the quantitation and detection of infectious viruses in water samples.

Infection of HeLa cells by avian infectious bronchitis virus is dependent on cell status

To investigate the adaptation of avian infectious bronchitis virus (IBV) in a human cell line may be beneficial to understanding the potential mechanisms of coronavirus interspecies infection. The current study addressed the poor replication of IBV in the HeLa human cell line demonstrated in previous reports. We showed that IBV strains M41, H52, H120 and Gray could be propagated in HeLa cells with distinct cytopathic effect. The virus titre in freshly dispersed HeLa cells was 1000-fold higher than in cell monolayers. Trypsin was not the determinant for the viral replication, suggesting that the restriction of IBV replication in HeLa cells is the result of intracellular events rather than the binding to or fusion with host cells. These IBV strains replicated to an average titre of 10(3.4+/-0.2)/0.1 ml median tissue culture infectious doses in freshly dispersed HeLa cells and maintained this titre for the first 12 passages. Then an approximately 10-fold increase (10(4.20+/-0.19)/0.1 ml) occurred in passage 13, which was maintained to passage 16, after which there was another, bigger rise to 10(6.6+/-0.3)/0.1 ml in passage 17. This titre was maintained until passage 24 when the experiment was terminated. The IBV M41 S1 gene was amplified and sequenced for passages 0, 5 and 21. There was only one amino acid replacement in the S1 protein, in passage 21. The presence of sialic acid on HeLa cells contributed to efficient virus replication, while human aminopeptidase N was not involved in the infection. Haemagglutinin activity gradually reduced with increased passages. These results indicated that the virus adaptation would probably be determined by host cell modification such as receptor glycosylation and different receptor utilization instead of viral gene mutation.

Detection of adenoviruses in shellfish by means of conventional-PCR, nested-PCR, and integrated cell culture PCR (ICC/PCR)

We tested three PCR based methodologies to detect adenoviruses associated with cultivated oysters. Conventional-PCR, nested-PCR, and integrated cell culture-PCR (ICC/PCR) were first optimized using oysters seeded with know amounts of Adenovirus serotype 5 (Ad5). The maximum sensitivity for Ad5 detection was determined for each method, and then used to detect natural adenovirus contamination in oysters from three aquiculture farms in Florianopolis, Santa Catarina State, Brazil, over a period of 6 months. The results showed that the nested-PCR was more sensitive (limit of detection: 1.2 PFU/g of tissue) than conventional-PCR and ICC-PCR (limit of detection for both: 1.2 x 10(2)PFU/g of tissue) for detection of Ad5 in oyster extracts. Nested-PCR was able to detect 90% of Ad5 contamination in harvested oyster samples, while conventional-PCR was unable to detect Ad5 in any of the samples. The present work suggests that detection of human adenoviruses can be used as a tool to monitor the presence of human viruses in marine environments where shellfish grow, and that nested-PCR is the method of choice.

Rotavirus survival and stability in foods as determined by an optimised plaque assay procedure

Tissue culture adapted rotavirus strains were propagated in MA104 and CaCo2 cells using standard cell culture procedures. The progress of infection was monitored by examining for a cytopathic effect, and for the presence of viral RNA in the tissue culture supernatant as determined by a guanidinium-based method. Subsequently, an effective plaque assay for rotavirus was developed using MA104 cells by optimising the adsorption time (2 h) and the levels of fetal calf serum (2.5%) in the overlay medium. Tragacanth gum was used in the overlay medium to immobilize the virus, and plaques were subsequently stained with 1% crystal violet. Using this optimised plaque assay, the survival of rotavirus following exposure to heat and UV irradiation was evaluated by enumerating the clear plaques. It was shown that 60 degrees C for 10 min was sufficient to reduce the viral titer by at least 7 logs, and 50 mJ of UV irradiation was sufficient to reduce the initial viral titer by > 2.5 logs. This optimised plaque assay was also used to determine the survival and stability of rotavirus from a range of experimentally contaminated foods including fruit juice, formula milk and lettuce.

Development of a rapid and sensitive quantitative assay for rotavirus based on flow cytometry

A very sensitive and accurate flow cytometry (FC) based method have developed to quantitate rotavirus infection in MA104 cells. Confluent cell monolayers were infected with serial dilutions of rotavirus SA11. After infection, the cells were recovered with the aid of trypsin and then reacted with monoclonal antibody M60 (specific for the rotavirus outer capsid protein, VP7), followed by a second antibody (anti-mouse IgG-FITC). A FACScan FC was used to estimate the number of infected cells, as well as the level of infection. Viral infection was optimised by varying the concentration of trypsin used in the maintenance medium. The FC method enables many cells to be screened quickly for infectivity, and can detect low levels of virus. This method can be adapted to monitor the presence of other viruses in clinical and environmental samples without the need for prolonged periods of adaptation to growth in tissue culture.

Detection of viruses in environmental samples: suitability of commercial rotavirus and adenovirus test kits

Commercially marketed kits are now available for rapid viral assay of clinical specimens. This study was conducted to determine the suitability of these kits for use in environmental testing. Eight rotavirus kits and one enteric adenovirus kit were screened for sensitivity using simian rotavirus SA11, human rotavirus Wa, and adenovirus 41. The most sensitive rotavirus kit and the adenovirus kit were selected for further evaluation using virus-seeded and unseeded sewage samples. The selected rotavirus kit proved capable of detecting virus at the 10(1) PFU/ml level. The enteric adenovirus kit was similarly sensitive, detecting virus at the 10(1) TCID50/ml level. Neither kit was adversely affected by the presence of sewage. Kit assay revealed 3 of 30 unseeded sewage samples to be positive for rotavirus. Adenovirus positive samples were not detected among the 30 samples. These results were confirmed using electron microscopy. It was concluded that sensitive commercial kits could provide a reasonable alternative to cell culture for the presumptive testing of environmental samples.

Culture adaptation and characterization of group A rotaviruses causing diarrheal illnesses in Bangladesh from 1985 to 1986

Group A rotaviruses collected between 1985 and 1986 during comprehensive surveillance of treated diarrheal episodes occurring in a rural Bangladesh population were culture adapted and characterized by electropherotype, serotype, and subgroup. Of 454 episodes of rotavirus-associated diarrhea, rotaviruses were culture adapted from 381 (84%), and 335 contained 11 electrophoretically identical segments in unpassaged and cultured preparations. These 335 comprised 69 different electropherotypes with between 1 (32 isolates) and 79 representatives. The persistence of specific rotavirus strains within the study population, as defined by the detection of viruses with particular electropherotypes, was generally limited to a period of only a few months. All 335 isolates were serotyped by neutralization with hyperimmune antisera to prototype rotavirus strains representative of serotypes 1 to 4, i.e., Wa, DS-1, P, and ST-3. It was found that 80, 48, 119, and 88 isolates belonged to serotypes 1 to 4, respectively. The concentrations of hyperimmune antisera required to neutralize these isolates, however, were at least threefold greater than those needed to neutralize the homologous strains. Therefore, the isolates appeared to have altered neutralization epitopes from their prototype strains. Furthermore, the serotype 4 isolates were consistently shown to be much more closely related to the serotype 4B VA70 strain than the serotype 4A ST-3 strain. All but two isolates identified as serotypes 1, 3, or 4 had long electropherotypes and were subgroup II, and all but one serotype 2 isolate were subgroup I and had short electropherotypes. The three disparate strains appeared to be genetic reassortants. Evidence is presented that dual infections required for reassortant formation were not uncommon. Thus, formation of multiple reassortants may have been a cause for the observed rapid shift in viral strains within the study population.

HT-29 cells: a new substrate for rotavirus growth

Susceptibilities of a continuous rhesus monkey kidney cell line (MA-104) and that of a human colon carcinoma cell line (HT-29) to infection by different human and animal rotavirus strains were compared. HT-29 cells appeared to be more sensitive to human rotavirus infection than MA-104 cells, whereas the latter cell line was more susceptible to animal rotavirus replication. The greater sensitivity to human rotavirus infection of HT-29 cells was confirmed by the successful, direct isolation of these viruses from faecal specimens. Human rotavirus infection of HT-29 cells was also followed by transmission electron microscopy. In ultra-thin sections, unenveloped particles of rotaviruses, representing infectious mature virions, were observed in large number. Moreover, many "double-shelled" particles were detected in negative-stained supernatants from infected cultures. Scanning electron microscopy of uninfected HT-29 cells showed that in the presence of Ca++, required for rotavirus growth, they are able to express some of the features of mature intestinal cells. In view of these results, HT-29 cells appear to be a useful in vitro model for the study of rotavirus infection.

Rapid screening test for the diagnosis of rotavirus infection

The early diagnosis of human rotavirus infection is essential for effective patient management and infection control. We report here a rapid, easy-to-perform, and inexpensive test for rotavirus detection. The viral RNA is extracted directly from the stools and electrophoresed on 1% agarose gels. Currently available immunoassays for routine diagnostic purposes are directed at the common group A-specific antigen. As reports become available on human gastroenteritis caused by the atypical or novel rotaviruses, this technique presents an added advantage in that it can detect both group A and non-group A rotaviruses.

Efficiency of isolation of human rotavirus in primary African green monkey kidney cells

Out of 212 human rotavirus (HRV) containing fecal specimens, 173 (81.6%) yielded virus on first passage in primary African Green monkey kidney cells (AGMK), while additional 34 specimens, did not yield virus on first passage. However, following blind passages, 18 of the 34 yielded virus in passage levels 2-8, thus raising the overall isolation rate to 90.1%. The isolation rate of HRV strains obtained in embryonic Rhesus monkey kidney cell line (MA-104), was only 41.4%. ELISA tests performed on fluids from infected cell cultures proved to be an efficient tool to measure virus replication. No differences were encountered in the isolation rates between subgroup I and II strains, while viruses lacking the antigenic determinants of both subgroups did not grow at all. However, one of those unusual group A strains was isolated and grew well in AGMK cells. Primary AGMK and MA-104 cells supported the growth of tissue culture adapted virus most efficiently when compared with six human and primate cell types.

Human viral gastroenteritis

During the last 15 years, several different groups of fastidious viruses that are responsible for a large proportion of acute viral gastroenteritis cases have been discovered by the electron microscopic examination of stool specimens. This disease is one of the most prevalent and serious clinical syndromes seen around the world, especially in children. Rotaviruses, in the family Reoviridae, and fastidious fecal adenoviruses account for much of the viral gastroenteritis in infants and young children, whereas the small caliciviruses and unclassified astroviruses, and possibly enteric coronaviruses, are responsible for significantly fewer cases overall. In addition to electron microscopy, enzyme immunoassays and other rapid antigen detection systems have been developed to detect rotaviruses and fastidious fecal adenoviruses in the stool specimens of both nonhospitalized patients and those hospitalized for dehydration and electrolyte imbalance. Experimental rotavirus vaccines have also been developed, due to the prevalence and seriousness of rotavirus infection. The small, unclassified Norwalk virus and morphologically similar viruses are responsible for large and small outbreaks of acute gastroenteritis in older children, adolescents, and adults. Hospitalization of older patients infected with these viruses is usually not required, and their laboratory diagnoses have been limited primarily to research laboratories.

Synthesis of human rotavirus polypeptides in cell culture

The replication strategy of a human serotype 1 rotavirus, adapted to rapid growth in CV-1 cells, was investigated. A single cycle growth curve revealed eclipse and latent periods of 3 and 4 hours, respectively. Although the extent of reduction of host cell protein synthesis was directly related to the multiplicity of infection of the virus, incorporation of actinomycin D and excess NaCl into the medium resulted in significant reduction in host cell background and enabled observation of viral polypeptides as early as 2 hours post infection. Five polypeptides were found to be structural components of the virion, and a further eight appeared to be nonstructural proteins or intermediates. Five polypeptides were glycosylated during virus replication, but only one of these, VP7, was a definite structural glycoprotein. Pulse-chase experiments revealed that four low molecular weight polypeptides underwent post-translational modifications.

Use of serotype-specific monoclonal antibodies to study the epidemiology of rotavirus infection

The development of an enzyme immunoassay (EIA) capable of serotyping human rotavirus (HRV) in faecal extracts has enabled us to retrospectively study the epidemiology of rotavirus infection in Melbourne. Of 552 stored specimens obtained from individuals with rotavirus-associated gastroenteritis between 1975 and 1986, the serotype could be determined in 62%. Infection was most prevalent in two groups, neonates and children aged between 12 and 24 months. In these groups infection was due to different serotypes, type 1 in older children and an untypable virus in infants. Serotype 1 strains were detected in greater numbers than the other serotypes and circulated in each year of the study. Serotype 2 rotaviruses were associated with a large epidemic in 1978, but have been detected only rarely since.

Physicochemical stability and inactivation of human and simian rotaviruses

The effects of various physical and chemical treatments on the stability of a human serotype 1 rotavirus and simian agent 11 (SA11) were compared by using a fluorescence focus assay. The infectivity of both strains was retained after storage at room temperature for 14 days, 4 degree C for 22 days, and -20 degree C for 32 days; lyophilization; and treatment at pH 3 to 11. Both viruses were inactivated at pH 12, as was the human virus at pH 2, although this pH resulted in only partial inactivation of SA11. The human virus also appeared to be more sensitive than SA11 to the action of ether and chloroform. The infectivity of both viruses was lost after UV irradiation for 15 min and after treatment with 8% formaldehyde for 5 min, 70% (vol/vol) ethanol for 30 min, and 2% lysol, 2% phenol, and 1% H2O2 for 1 h each.

Isolation from faecal specimens of new strains of human rotavirus primarily cytopathic for stationary cell cultures without trypsin

Eight cytopathic human rotavirus strains were isolated in LLC-MK2 cells and in human embryo fibroblasts. The strains were isolated from faeces collected from pediatric and adult patients. Pretreatment of specimens with trypsin and trypsin incorporation in maintenance medium were not performed. Inoculated monolayers were not subjected to centrifugation and were incubated stationary at 36 degrees C. Viruses were identified by electron microscopy and by fluorescent antibody techniques. It is suggested that these rotaviruses are different from any previously recovered from man.

Radioimmunofocus assay for detection and quantitation of human rotavirus

A radioimmunofocus assay suitable for quantitation of cell culture-adapted human rotavirus was developed. The method was reproducible, more sensitive than plaque assay, and useful to detect and quantify strains of rotavirus which do not produce plaques. Preliminary results also suggested that the technique will be a useful means of serotyping cell culture-adapted strains of the virus.

Detection of rotavirus in human stools by using monoclonal antibody

A monoclonal antibody, 3F7, that reacts with the common rotavirus antigen on the sixth viral gene product was prepared. It was used in a direct monoclonal antibody radioimmunoassay (RIA) as a diagnostic reagent for detection, in 3.5 h, of rotavirus in human pediatric stool specimens. In the 177 samples tested, a concordance of 96% was seen between the monoclonal RIA and the well-established and commonly used commercially available Rotazyme test. Six discrepant specimens that were positive by monoclonal RIA but negative by Rotazyme were shown to be positive by either electron microscopy or confirmatory blocking immunoassay. A seventh discrepant specimen was positive by Rotazyme and negative by monoclonal RIA as well as by both direct and immune electron microscopy. The monoclonal RIA test appears to be highly sensitive and specific, and merits additional evaluation as a rapid, convenient diagnostic assay that can reduce currently encountered problems associated with diagnosing rotavirus infection by immunoassay.

Efficiency of human rotavirus propagation in cell culture

This study was designed to find methods to reproducibly propagate human rotaviruses from fecal specimens and to determine the relationship between particle numbers and infectivity. Growth of virus was initially compared in primary and continuous lines of monkey kidney cells. Primary cells (African green and cynomolgus monkey kidney) supported virus growth directly from fecal specimens much more efficiently than did continuous lines of African green (CV-1) or rhesus (MA104) monkey kidney cells. Rotaviruses were grown in primary cells from 14 of 14 fecal specimens of different individuals collected over a 3-year period. Although rotaviruses in fecal samples could not always be grown in the continuous cell lines, two passages in primary cells appeared to fully adapt the viruses for propagation in the continuous cell line tested (MA104). The efficiency of rotavirus growth was quantified with five of the fecal isolates. It was calculated that, on the average, 1 out of every 46,000 particles in fecal specimens infected monkey kidney cells. After three passages in primary cells, an average of 1 out of every 6,600 progeny virus particles appeared to be infectious. Thus, rotaviruses in fecal specimens were consistently grown in primary cells, and passage in these cells both increased virus infectivity and adapted the viruses for growth in continuous cell lines.