Diagnosis of fastidious enteric adenoviruses 40 and 41 in stool specimens

Efficient amplification of chimeric adenovirus 5/40S vectors carrying the short fiber protein of Ad40 in suspension cell cultures

The human adenovirus 40 (Ad40) is a promising tool for gene therapy of intestinal diseases. Since the production of Ad40 in vitro is extremely inefficient, chimeric Adenovirus 5/40S vectors carrying the Ad40 short fiber on the Ad5 capsid have been developed. However, Ad5/40S productivity is low. We hypothesized that low productivity was a result of inefficient viral entry into producer cells during amplification. To this end, we have developed a production strategy based on using 211B cells (expressing Ad5 fiber) during amplification steps, while Ad5/40S infectivity is further improved by adding polybrene during infections. In addition, the optimal harvesting time was determined by evaluating the Ad5/40S viral cycle. The developed production strategy significantly reduces the number of amplification cycles and duration of the process. Finally, to further facilitate Ad5/40S production, 211B cells were adapted to suspension thus allowing to easily upscale the production process in bioreactors.

Effect of host cells on low- and medium-pressure UV inactivation of adenoviruses

UV disinfection is highly effective against most pathogens, with the exception of the adenoviruses (AD). To date, many studies have focused on low-pressure (LP) UV inactivation of AD, but little is known about the effect of medium-pressure (MP) UV inactivation of AD. Despite numerous studies of LP UV inactivation of AD, extreme variabilities in the LP UV dose requirements of AD had been observed because of differing experimental conditions used, such as the types of cell lines used for AD enumeration. This study therefore investigates the effect of three different host cell lines (PLC/PRF/5, human embryonic kidney 293 [HEK293], and XP17BE) on the LP and MP UV dose requirements of AD serotype 5 (AD5), AD40, and AD41 under similar experimental settings. Results showed that for 4-log inactivation of AD, LP UV and MP UV doses needed to be in the ranges of 123 to 182 mJ/cm² and 65 to 90 mJ/cm², respectively, when HEK293 and PLC/PRF/5 cells were used for enumeration. The UV doses required for MP UV inactivation of AD were significantly lower than those required for LP UV inactivation (P value < 0.05). When different cell lines were used for enumeration, UV dose requirements for AD differed. AD were portrayed to be most susceptible to UV (LP UV doses of <57 mJ/cm² and MP UV doses of <42 mJ/cm² for 4-log AD inactivation) when the XP17BE cells were used as the host cell. The use of different cell lines for AD enumeration affected LP UV dose results more significantly than MP UV dose results (P value < 0.05). Cell line variability factors for LP UV disinfection (CL(LP)) and MP UV disinfection (CL(MP)) for AD5, AD40, and AD41 enumerated with HEK293, PLC/PRF/5, and XP17BE cells were in the ranges of 1.0 to 3.2 and 1.0 to 2.5, respectively.

Computational analysis of human adenovirus serotype 18

The genome of the sole remaining unsequenced member of species A, human adenovirus type 18 (HAdV-A18), has been sequenced and analyzed. Members of species A are implicated as gastrointestinal pathogens and were shown to be tumorigenic in rodents. These whole genome and in silico proteome data are important as references for reexamining and integrating earlier work and observations based on lower resolution techniques, such as restriction enzyme digestion patterns, particularly for hypotheses based on pre-genomics data. Additionally, the genome of HAdV-A18 will also serve as reference for current studies examining the molecular evolution and origins of human and simian adenoviruses, particularly genome recombination studies. Applications of this virus as a potential vector for gene delivery protocols may be practical as data accumulate on this and other adenovirus genomes.

Infection kinetics of human adenovirus serotype 41 in HEK 293 cells

The purpose of this work was to acquire an overview of the infectious cycle of HAdV-41 in permissive HEK 293 cells and compare it to that observed with the prototype of the genus, Human adenovirus C HAdV-2. HEK 293 cells were infected with each virus separately and were harvested every 12 h for seven days. Infection kinetics were analysed using confocal and electronic microscopy. The results show that, when properly cultivated, HAdV-41 was not fastidious. It had a longer multiplication cycle, which resulted in the release of complete viral particles and viral stocks reached high titres. After 60 h of infection, the export of viral proteins from the infected cell to the extracellular milieu was observed, with a pattern similar to that previously described for HAdV-2 penton-base trafficking after 30 h of infection. HAdV-41 had a non-lytic cycle and the infection spread from the first infected cell to its neighbours. The release process of the viral particles is unknown. The results observed for HAdV-41 infection in HEK 293 cells show how different this virus is from the prototype HAdV-2 and provides information for the development of this vector for use in gene therapy.

Adenoviruses associated with acute gastroenteritis in hospitalized and community children up to 5 years old in Rio de Janeiro and Salvador, Brazil

Acute gastroenteritis is a major source of morbidity and mortality among young children in developed and developing countries. Human adenoviruses (HAdVs), and in particular species F, are related to childhood diarrhoea worldwide. This study presents the results obtained during an investigation of HAdVs causing acute gastroenteritis in children hospitalized in Rio de Janeiro, RJ, Brazil, from April 1996 to September 2003, as well as in children with diarrhoea living in the slums of Salvador, BA, Brazil, from October 2001 to September 2003. A total of 3060 stool samples was analysed by an enzyme immunoassay for rotavirus and adenovirus (EIARA) and 61 (2%) were found to be positive. HAdV presented with low prevalence throughout the year, with a slight but not significant increase in incidence in late summer and early autumn. Children up to 2 years of age were the most frequently affected (79% of all positive samples). All positive samples were analysed further by generic and species-specific HAdV PCR protocols, confirming 100% specificity of this rapid and inexpensive EIARA. Species F was the most prevalent (65%), despite the occurrence of species A (12%), C, D and co-infection F/D (5% each) and species B and co-infections F/A, F/C and B/D (2% each). In order to type the species F strains as HAdV-40 or -41, generic PCR and a HinfI restriction digest were performed. HAdV-40 and -41 were found to represent 62% (23/37) and 38% (14/37), respectively. These results demonstrated that a combination of generic and species-specific PCRs is useful and reliable for HAdV species and type identification directly from faecal specimens. The results confirmed the endemism of human adenoviruses, mainly species F, in children as aetiological agents of diarrhoea, although the limited sensitivity of EIARA as a screening method may have underestimated their prevalence.

Transfer of the alpha 5(IV) collagen chain gene to smooth muscle restores in vivo expression of the alpha 6(IV) collagen chain in a canine model of Alport syndrome

X-linked Alport syndrome is a progressive renal disease caused by mutations in the COL4A5 gene, which encodes the alpha 5(IV) collagen chain. As an initial step toward gene therapy for Alport syndrome, we report on the expression of recombinant alpha 5(IV) collagen in vitro and in vivo. A full-length cDNA-encoding canine alpha 5(IV) collagen was cloned and expressed in vitro by transfection of HEK293 cells that synthesize the alpha1(IV) and alpha2(IV), but not the alpha 3(IV) to alpha 6(IV) collagen chains. By Northern blotting, an alpha 5(IV) mRNA transcript of 5.2 kb was expressed and the recombinant protein was detected by immunocytochemistry. The chain was secreted into the medium as a 190-kd monomer; no triple helical species were detected. Transfected cells synthesized an extracellular matrix containing the alpha1(IV) and alpha2(IV) chains but the recombinant alpha 5(IV) chain was not incorporated. These findings are consistent with the concept that the alpha 5(IV) chain requires one or more of the alpha 3(IV), alpha 4(IV), or alpha 6(IV) chains for triple helical assembly. In vivo studies were performed in dogs with X-linked Alport syndrome. An adenoviral vector containing the alpha 5(IV) transgene was injected into bladder smooth muscle that lacks both the alpha 5(IV) and alpha 6(IV) chains in these animals. At 5 weeks after injection, there was expression of both the alpha 5(IV) and alpha 6(IV) chains by smooth muscle cells at the injection site in a basement membrane distribution. Thus, this recombinant alpha 5(IV) chain is capable of restoring expression of a second alpha(IV) chain that requires the presence of the alpha 5(IV) chain for incorporation into collagen trimers. This vector will serve as a useful tool to further explore gene therapy for Alport syndrome.

Prevalence of enteric adenoviruses among children with diarrhea in four Brazilian cities

BACKGROUND

Enteric adenoviruses are related to child diarrhea and appear to be spread worldwide.

OBJECTIVES

The aim of the present study was to determine the prevalence of enteric adenovirus infection among children in four Brazilian cities.

STUDY DESIGN

stool specimens were collected from children under 5 years of age with acute diarrhea.

RESULTS AND CONCLUSIONS

Enteric adenoviruses were detected in 1.55% (n=1420) of the samples analyzed indicating the circulation of these viruses among Brazilian children in association to diarrheal disease. These agents were isolated throughout the year demonstrating no specific seasonal distribution. Also, no pattern of serotype distribution between the cities was observed.

The molecular epidemiological study on enteric adenovirus in stool specimens collected from Wuhan area by using digoxigenin labeled DNA probes

A summer-autumn (1994) molecular epidemiological study of enteric adenoviruses (EAds) in stool specimens collected in Wuhan area was conducted by using Digoxigenin-labelled DNA probes specific to EAd40 and EAd41 respectively. 44 of 602 specimens were positive, among which 23 cases were identified as EAd40, 14 were EAd41 infection and 7 were dual infection. The ratio of males to females for the positive specimens was 1. 44. The infection rate of EAd40 and EAd41 each displayed no marked difference in seasons (summer and autumn) and similar age distribution was found between them. All of the two types of EAds infections predominated in patients with diarrhea under 3 years old. The results indicated that the Digoxigenin probe could detect DNA quantities as low as 1 pg with satisfactory specificity and the technique can be used for both clinical and experimental purposes.

Detection and typing of subgroup F adenoviruses using the polymerase chain reaction

A DNA amplification test was developed for the sensitive detection of the diarrhoea-associated subgroup F adenoviruses in clinical specimens. The test was made highly specific for serotypes 40 and 41 by using a region of the genome (the long-fiber gene) which is not significantly homologous to other human adenoviruses, but which is highly conserved between Ad40 and Ad41. A positive subgroup F adenovirus diagnosis was characterized by the presence of an amplification product of 152 base pairs, which could be digested into products of predictable length by restriction enzymes XbaI and SpeI. The viruses were typed as either Ad40 or Ad41 by digestion of the amplification product with a restriction enzyme which digested only Ad40 DNA. The specificity of the test was assessed using DNA from other adenoviruses, from human and simian cells, and from bacteria commonly found in the human intestine. There was a strong correlation between results of typing obtained with PCR and restriction enzyme typing of Ad40 and Ad41, and also positivity using subgroup F specific probes in dot blot hybridizations.

Structural features unique to enteric adenoviruses

Enteric adenoviruses are important agents of pediatric gastroenteritis. Characterization of monoclonal antibodies against human adenovirus 41 (h-41) identified an epitope of interest on protein VI, an internal virion protein. The epitope is common to enteric adenoviruses (subgenus A: h-12, h-18, h-31 and subgenus F: h-40, h-41) but is not shared by non-enteric serotypes (subgenera B, C, D or E). By expressing random oligonucleotide fragments of the protein VI gene as T7 gene 10 fusion proteins in the pTope vector (Novagen), the epitope was mapped within the central domain of protein VI, to the region corresponding to aa 114-125 of the Ad2 protein. Identification of this epitope reflects the close evolutionary relationship of subgenus A and subgenus F adenoviruses and draws attention to structural features of enteric adenoviruses as potential determinants of tropism. Furthermore, this epitope may be valuable for identification of enteric adenoviruses in clinical specimens.

Prevention by alpha-tocopherol and rutin of glutathione and ATP depletion induced by oxidized LDL in cultured endothelial cells

1. Oxidized low density lipoproteins (LDL) are thought to play an important role in atherogenesis. Mildly oxidized LDL are cytotoxic to cultured endothelial cells. Toxic doses of oxidized LDL promote the peroxidation of cellular lipids (beginning at 6 h and being maximal after 12 h of pulse with oxidized LDL) and glutathione and ATP depletion (beginning after 15 h of pulse and evolving concurrently with the cytotoxicity). 2. Antioxidants from 3 different classes (rutin, ascorbic acid and alpha-tocopherol) were compared as to their ability to inhibit the cytotoxic effect of oxidized LDL to endothelial cells. 3. Effective concentrations of alpha-tocopherol inhibited cellular lipid peroxidation, glutathione and ATP depletion and the cytotoxic effect. 4. Ascorbic acid was less effective than alpha-tocopherol and rutin, and exhibited a dose-dependent biphasic effect in the presence of oxidized LDL. 5. Effective concentrations of rutin inhibited glutathione and ATP depletion as well as cytotoxicity, but did not block cellular lipid peroxidation. This suggests that the glutathione and ATP depletion is directly correlated to the cytotoxicity of oxidized LDL, whereas cellular lipid peroxidation is probably not directly the cause of cellular damage leading to cell death. 6. The association of antioxidants of 3 different classes allowed the suppression of the biphasic effect of ascorbic acid and increased the efficacy of the protective effect. The potential consequences for prevention of the pathogenic role of oxidized LDL in endothelial injury are discussed.

Adenovirus genome types isolated from stools of children with gastroenteritis in São Paulo, Brazil

In a prospective one-year study of acute gastroenteritis in hospitalized children less than 2 years of age, in São Paulo (Brazil), adenoviruses were detected by specific enzyme immunoassay (El-ARA) in 7 of 67 (10%) ill children and in 9 of 79 (11.4%) controls. They were the sole recognizable agent of diarrhea in 6 ill children. In another child these viruses were detected in a dual infection with astrovirus. Enteric adenoviruses (Ad40/41) were the most common serotypes detected in children with diarrhea (3/7) and Ad7 the serotype most detected in the controls (5/9), associated with lower respiratory tract infection. Thirteen adenovirus strains, isolated in HEp2 or HEK-293 cells, were characterized by seroneutralization and restriction enzyme analysis. The established adenoviruses were typed as AV-7-D5 (five associated to lower respiratory tract infection and one to diarrhea), AV-1-D10 (one diarrhea case), AV-31-D2 (two controls with respiratory infection), and two isolates as AV-12-D7, a new genome type. One subgenus D isolate, serotype 28, with restriction patterns different from those of the prototype, remained untyped. Only one enteric adenovirus could be typed. The restriction patterns of this isolated were similar to those of the prototype AV-41-D1. The genome type of the other three enteric adenoviruses could not be determined.

Adenoviruses isolated in the Stockholm area during 1987-1992: restriction endonuclease analysis and molecular epidemiology

Adenoviruses recovered from the northern Stockholm area during 1987-1992 have been subjected to restriction endonuclease analysis. Adenoviruses of all subgenera (A-F) were represented and a considerable degree of serotype variation was seen, e.g. the rarely encountered subgenus A viruses were frequently isolated in the present study. Of 16 subgenus A isolates, Ad31 predominated with 12 strains which were equally distributed into the DNA-variants D2 and D7. Analysis of 38 Ad3 isolates revealed four DNA-variants: D1, D3, D10, and "Sto1". The ten Ad7 isolates belonged all to the DNA-variant D5 of Ad7. Of 27 Ad1 strains, 11 belonged to D10, followed by the DNA-variants D4 and D7 with four strains each. Among Ad2 isolates, D2 or D2-like strains prevailed (23/28). Of six Ad5 strains, three belonged to the DNA-variant D2. The most notable subgenus D event was a nosocomial outbreak of keratokonjunctivitis due ot Ad19a. In addition, a collection of heterogenous subgenus D strains was detected, most of which untypable by RE-analysis. Among the six Ad4 isolates of subgenus E, both genomic clusters (p and a, respectively) of Ad4 were recognized. Concerning the clinical important subgenus F adenoviruses, only two strains of Ad40 were detected as compared to 12 strains of Ad41, all of which ascribed to the DNA-variant D12 of Ad41.

Adenovirus type 40 and 41 growth in vitro: host range diversity reflected by differences in patterns of DNA replication

Subgroup F adenoviruses adapt poorly to cell culture, but the reasons for their fastidious nature are as yet ill defined. In an attempt to gain an overview of the differences in replication between adenovirus type 2 (Ad2) and representative strains of Ad40 and Ad41, cell lines which show different degrees of permissiveness to Ad40 and Ad41 were infected and examined with respect to three key functions in the Ad2 life cycle: host protein shutoff, DNA synthesis, and late antigen synthesis. The complexity of growth patterns exhibited by the subgroup F adenoviruses suggests that defectiveness is a multifactorial phenomenon not easily explainable by a single aberrant function. Furthermore, results suggest that there may be replicative defects in subgroup F adenoviruses which are not shared by both serotypes or by all strains.

Type- and group-specific polymerase chain reaction for adenovirus detection

We report on a 1,551-base-pair-long DNA sequence, encoding the variable region and parts of the flanking conserved regions of the human adenovirus type 8 (AV8) hexon, and a sequence comprising 1,404 base pairs, encoding the corresponding regions of the human adenovirus type 31 (AV31). Comparison of the hexon sequences showed that the major sequence changes were located in loops I1 and I2 of the hexon polypeptides which form the surface of the virion. We established a type-specific polymerase chain reaction (PCR), using a combination of a group-specific (general) primer, located in a conserved region of the hexon gene, and type-specific primers located in the region that encodes for loop I2 of the AV8 (subgroup D), AV31 (subgroup A) and AV40 and 41 (both subgroup F) hexon polypeptides. We performed PCR directly from several different clinical specimens or from isolates (AV31). Type-specificity was confirmed by restriction analysis. We also carried out several PCR directly from faecal specimens, using a group-specific primer pair and compared the sensitivity of PCR with that of electron microscopy and enzyme immuno assay.

Characterization of two divergent adenovirus 31 strains

Two divergent strains of adenovirus type 31 were analyzed by neutralization test and restriction endonuclease (RE) patterns in an effort to find the basis for their genetic variability. One strain, isolated from the throat of a child in Maryland during an upper respiratory illness in 1968, was partially neutralized by Ad 31 antisera (to 16-fold lower than homologous titer) while its own antiserum fully neutralized prototype Ad 31 virus, but shared only 9% of comigrating RE fragments with Ad 31 prototype (vs. 30% with Ad 18 prototype); however, PCR tests specific for the inverted terminal repeat (ITR) sequence of Ads 12 and 18 were negative. The other strain, recovered from a stool sample from an infant with diarrhea in Georgia in 1979, was inhibited by Ad 31 antiserum to within 4-fold homologous titer, but shared only 15% of comigrating fragments with Ad 31 prototype (vs. 91% with Ad 18 prototype); ITR-specific PCR tests with this virus were positive for Ad 12/Ad 18. These data suggest that both strains are from separate evolutionary lines of Ad 31 unrelated to all other isolates studied to date by RE analysis, and that the partial neutralization by prototype Ad 31 antisera might represent small mutations in the hexon gene.

Sensitivity of subgroup F adenoviruses to interferon

The subgroup F adenoviruses were tested for their ability to induce interferon in semi-permissive human cells (Chang conjunctiva) and non-permissive cells (HEF, human embryo lung fibroblasts). These cells did not produce interferon spontaneously or in response to infection by either of these adenoviruses. It was concluded that interferon induction in response to subgroup F adenovirus infection is not a likely explanation of limited virus growth in culture. Adenovirus 40 and Ad41, unlike Ad2, were found to be sensitive to human lymphoblastoid interferon in Chang conjunctival cells. The addition of Ad2 to cells before pretreatment with interferon resulted in the partial and complete abrogation of Ad40 and Ad41 interferon sensitivity, respectively. The suppressive effect of Ad2 on the inhibitory action of interferon and the modulatory function of Ad2 in mixed infection with either Ad40 or Ad41 suggests the inadequate functioning of a subgroup F adenovirus gene product or products involved in suppression of the interferon-induced antiviral state.

Restriction endonuclease patterns of adenovirus type 12 and 18

Restriction endonuclease analysis using 10 restriction enzymes was performed on six and three wild isolates of adenovirus (Ad) type 12 and 18, respectively. Among the Ad12 strains, five DNA variants could be identified. The degree of pairwise comigration of restriction fragments suggests a high degree of genomic diversity within Ad12. The wild isolates of Ad18, on the other hand, displayed a low degree of genetic variability and comprised one DNA variant closely related to the prototype strain. The BglII, BstEII, and HindIII restriction endonuclease patterns of Ad18 were inconsistent with those originally presented. Identical RE-patterns among Ad18 prototype strains (DC) obtained from four different sources, including directly from the American Type Culture Collection, verify that the genuine Ad18 prototype was used in the present study. Using the revised restriction patterns of BglII, BstEII, and HindIII, a proper identification of Ad18 will be facilitated.

Adenovirus infection and specific secretory IgA responses in the intestine of infants

We investigated adenovirus (Ad) infection of the intestine and Ad group-specific fecal IgA antibody responses in seven infants who were followed up from birth to 16 months to seven years of age. We isolated in tissue culture from fecal samples not only enteric Ad type 41 but also other Ads (types 2, 3, 5, 6, and 12). We also detected Ad antigens in the feces by ELISA at the times of infection with even non-enteric Ads, suggesting that a large amount of antigens were produced in the intestine. We found that repeated Ad infections with different serotypes were occurring and there were good fecal IgA antibody responses at each time. The infection seemed usually mild or asymptomatic: only one out of 23 occasions of the detected infections required hospitalization.

A block in release of progeny virus and a high particle-to-infectious unit ratio contribute to poor growth of enteric adenovirus types 40 and 41 in cell culture

The fastidious enteric adenovirus (FEAd) types 40 (Ad40) and 41 (Ad41) are found in stool specimens of infants and young children in association with gastroenteritis. Although they can be isolated routinely from clinical specimens by using 293 cells, they are propagated with variable success in cell lines which support the replication of other adenovirus serotypes. HeLa cells are generally considered to be nonpermissive for the replication of FEAds, but in this study, Ad40 and Ad41 grew to comparable titers in individual 293 and HeLa cells. However, virus was not efficiently released from infected HeLa cells and thus did not undergo multiple cycles of infection in HeLa cell cultures. The block in virus release was not overcome in KB18 cells which, like 293 cells, constitutively express proteins encoded by the E1B region of a subgroup C adenovirus (in this case Ad2). Moreover, it was apparent from these studies that Ad40 and Ad41 have particle-to-infectious unit ratios several orders of magnitude greater than that for Ad5, even in 293 cells which express the E1A and E1B proteins of Ad5 and are considered to be permissive for replication of the FEAds. Neither the block in release of progeny virus nor the high particle-to-infectious unit ratio is explained solely by the defect in expression of the E1B 55K protein identified by Mautner et al. (V. Mautner, N. MacKay, and V. Steinthorsdottir, Virology 171:619-622, 1989; V. Mautner, N. MacKay, and K. Morris, Virology 179:129-138, 1990).

Fastidious human adenovirus type 40 can propagate efficiently and produce plaques on a human cell line, A549, derived from lung carcinoma

Human adenovirus type 40 (Ad40) cannot propagate in conventional established human cell lines such as KB or HeLa cells. However, it has been shown that Ad40 DNA replicates in KB18 cells which express Ad2 E1B genes, suggesting that Ad40 is defective in the E1B gene function in KB or HeLa cells. We show here that Ad40 can propagate and produce plaques on A549 cells which do not contain Ad E1B genes. Our experiments show that the levels of replication of Ad40 DNA and production of infectious Ad40 virus in A549 cells are the same as or higher than those in 293 or KB18 cells. Dot blot analysis shows that the levels of Ad40 E1A and E1B mRNAs expressed in A549 cells at early to intermediate times postinfection are at least 10-fold higher than those in KB or KB18 cells. Northern (RNA) blot analysis shows that large E1B mRNA species (approximately 24S to 26S) are synthesized prior to the onset of DNA replication in A549 cells. No E1B mRNA species are synthesized in KB or KB18 cells at early times postinfection, and no differences in the expression of E1B mRNAs are seen between KB and KB18 cells. The experiment suggests that A549 cells have a cellular factor(s) which activates Ad40 E1B mRNA synthesis and that the E1B mRNA synthesis helps Ad40 propagation. In contrast, Ad40 can propagate in KB18 cells by using Ad2 E1B gene products that are constitutively expressed in this cell line. Furthermore, this result shows that Ad40 cannot propagate in KB cells because of the failure in the expression of E1B genes at early times postinfection.

Epidemiology of enteric adenoviruses 40 and 41 in acute gastroenteritis in infants and young children in the Tokyo area

82/2,223 stool specimens, collected 1982-1988, from children with enteritis (3.7%) were found to contain adenoviruses; 17 adenovirus-positive samples were provided from other institutes. 89 adenoviruses were isolated in Graham 293 cells from these 99 specimens and were typed by DNA restriction enzyme analysis with Sma I. 37 strains were typed as adenovirus 40 (AD40), and 37 strains as adenovirus 41 (Ad41). Although most strains had the same DNA profiles, a few strains had 3 kinds of different electropherotypes generated by Sma I. Five strains were identified as adenovirus 31. The remaining 10 strains were adenovirus 1 (2 strains), adenovirus 2 (3 strains), adenovirus 3 (1 strain), adenovirus 5 (1 strain), and a non-classified adenovirus (3 strains). Ad40 and Ad41 infections were found throughout the year, but peaked between September and November. 80% of the children with adenovirus infections were less than or equal to 2 years of age. The highest incidence of diarrhea caused by Ad40 or Ad41 was in 6-11 months old children. 1982-1984, the rate of Ad40 infection was 91.7%, while the rate of Ad41 infection was only 8.3%. The prevalence of Ad40 infection gradually diminished from 1985. During 1987 and 1988 the reverse ratios, 20.6% and 79.4%, respectively, of Ad40 and Ad41 infections were observed. Thereafter, Ad41 infection became predominant.

Prevalent enteric adenovirus variant not detected by commercial monoclonal antibody enzyme immunoassay

A commercial monoclonal antibody enzyme immunoassay for the detection of enteric adenovirus type 40 and 41 (Ad40 and Ad41) in stool specimens was evaluated. Twenty-one stool specimens from children with gastroenteritis, with adenovirus particles visible by electron microscopy, and reference strains Ad40 Dugan and Ad41 Tak were tested by Ad40- and Ad41-specific and adenovirus group-reactive immunoassays. All stool specimens tested positive in the group-reactive immunoassay. However, only six specimens, containing isolates of Ad40 strain Hovi-X, an Ad40 genomic variant, and Ad41 strain Tak, reacted with the specific immunoassay, besides the reference strains. Fifteen stool specimens determined by restriction analysis to contain a genomic variant of Ad41 were negative by specific immunoassay. The positions of restriction site differences from the prototype strain Ad41 Tak were analyzed, and four mutations were mapped within the hexon gene; two others may occur in the fiber gene. The Ad41 genomic variant not detected by the enteric test is presently the most frequent cause of local adenoviral gastroenteritis. Highly specific monoclonal antibodies can fail to detect genomic variants of enteric adenoviruses, probably because of alteration of external neutralizable epitopes under immunological pressure to vary.

Enzyme-linked immunosorbent assay employing monoclonal antibodies for direct identification of enteric adenoviruses (Ad40,41) in feces

For detection and identification of enteric adenovirus (Ad) types 40 and 41 in stool specimens, enzyme-linked immunosorbent assay (ELISA) was developed with the use of three monoclonal antibodies: Ad group-specific, Ad40 type-specific, and Ad41 type-specific antibodies. Of 860 fecal samples from patients with acute gastroenteritis, 44 strains of Ad were isolated using Graham 293 cell cultures. Of these isolates, 20 were typed as Ad40, 18 were Ad41, and 6 were other Ads by neutralization tests with cell cultures. Results of the ELISA tests on these 860 fecal samples resulted in good agreement to those with the cell culture method. The ELISA tests using Ad type-specific monoclonal antibodies proved to be a specific and rapid technique for laboratory diagnosis of acute gastroenteritis caused by enteric Ads.

Adenovirus 41 growth in semi-permissive cells shows multiple-hit kinetics

Adenovirus type 41 infection of semi-permissive Chang conjunctival cells, monitored by fluorescent focus assay, followed multiple-hit kinetics. In non-permissive human cells, type 41 showed infectivity with two-hit kinetics in the presence of type 2. Type 41 infectivity was seen to be directly proportional to input concentration (one-hit) only in 293 cells, a continuous human line expressing Ad 5 E1 products.

Enteric adenoviruses

Human adenoviruses are classified into 47 serotypes and six subgenera (A-F) with different tropisms. In recent years adenovirus type 40 (Ad40) and 41 (Ad41) of subgenus F have been shown to be causative agents in enteric infections, which is second in importance only to rotaviruses as a cause of infantile gastroenteritis. Infection with EAds occurs worldwide and has been associated with 4-17% of cases of diarrhoea in children. AD40 and Ad41 primarily affect young children less than 2 years of age and occur throughout the year. The clinical characteristics include watery diarrhoea accompanied by vomiting, low grade fever and mild dehydration. A distinct feature of EAds infection is the protracted diarrhoea (mean 8.6 and 12.2 days for Ad40 and Ad41, respectively). Respiratory symptoms are infrequent. Serotypes Ad40 and Ad41 differ from all other (established) adenoviruses by being unable to replicate in conventional cell cultures. These fastidious viruses only grow in selected cell lines, 293 cells being the most commonly used. In spite of the difficulty of isolating Ad40 and Ad41, they can be directly identified and typed by ELISA and solid-phase immune electron microscopy. The amount of viral DNA in stool specimens is sufficient for identification by DNA restriction and dot-blot assays. The recent development of highly sensitive and specific monoclonal antibody-based ELISAs enable accurate diagnosis of adenovirus gastroenteritis in routine work and make possible the evaluation of the role of the enteric adenoviruses in diarrhoeal disease in the developing countries.

Laboratory identification of adenoviruses associated with gastroenteritis in Canada from 1983 to 1986

A retrospective analysis of adenovirus serotypes associated with gastroenteritis involved the examination of 143 stool specimens collected between 1983 and 1986 from symptomatic patients whose stools were positive for adenovirus by electron microscopy. The virus isolates obtained from 140 of the specimens were typed according to the SmaI cleavage pattern of the viral DNA and by neutralization with specific antisera. The predominant types were adenovirus type 31 (Ad31) (18%), Ad40 (16.9%), and Ad41 (38%), which together accounted for more than 70% of the isolates. The remaining virus isolates were typed as Ad1, 2, 3, 5, 7, and 12. DNA restriction analysis proved to be better than serum neutralization for identification of the enteric adenovirus serotypes in stool specimens. HindIII cleavage identified four Ad41 variants, none of which had a HindIII restriction pattern identical to that of the prototype strain Tak. Over the time period of the study, the incidence of Ad40 showed an overall decrease accompanied by an increased incidence of Ad41, while the incidence of Ad31 was relatively stable.

Time-resolved fluoroimmunoassay for enteric adenoviruses using the europium chelator 4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid

A time-resolved fluoroimmunoassay (TR FIA) was developed for the direct detection of adenovirus types 40 (Ad40) and 41 (Ad41) in stool specimens by using a monoclonal antibody (5D8/2C2) which recognizes both Ad40 and Ad41 but does not cross-react with other adenovirus serotypes. In this assay, the detector antibody is biotinylated directly rather than labeled with europium, and the fluorescent signal is generated on a solid phase in the presence of excess europium (Eu3+). The strength of the signal is dependent on the amount of a Eu3+ chelator [4,7-bis(chlorosulfophenyl)-1,10-phenanthroline-2,9-dicarboxylic acid (BCPDA)]-streptavidin complex bound by the biotinylated detector antibody (5D8/2C2). In a pilot study with 41 specimens, this TR FIA demonstrated a maximum sensitivity and specificity of 88% compared with SmaI restriction analysis of adenovirus isolates from the same specimens. TR FIA using the europium chelator BCPDA represents a feasible approach for the direct identification of specific adenovirus serotypes in stool specimens.

Detection of adenovirus type41 in stool samples by a latex agglutination method

We have developed a simple agglutination (LA) method for the detection of enteric adenovirus (EAd) in stool samples from infants with acute gastroenteritis. Ad type 41 (Ad41) was detected with high sensitivity and specificity by a slide agglutination test using latex particles coated with antiAd41 antibody (LA-antiAd41). The agglutination of LA-antiAd41 with Ad41 on a glass slide was evident macroscopically within 2 min. The sensitivity of the LA method was four times higher than that of the EM method.

Characterization of two genome types of adenovirus type 31 isolated in Stockholm during 1987

The authors isolated during 1987 seven adenovirus type 31 (Ad31) within a 9-month period. The isolates were obtained from urine, throat, and feces, implying a systemic spread of the infection. Most patients displayed gastrointestinal symptoms, but some had respiratory symptoms and fever. All of the strains differed by restriction endonuclease analysis from the prototype strain (1315) by an additional Bgl II restriction site. Ad31 isolates 1-6 could be divided into two groups by the enzymes Bam HI, Msp I, and Xho I. Each enzyme gave rise to the same group distribution: isolates 1-3 and 4-6, respectively. Digestion with Bst EII, Hind III, Kpn I, and Sma I resulted in identical patterns for isolates 1-6. Isolate 7, however, demonstrated a DNA deletion of approximately 0.8 kbp, but it was otherwise identical to isolates 4-6. In conclusion, two separate genome types of Ad31 were isolated, one of which included a DNA deletion mutant. The increased isolation rate may reflect an epidemiological situation, as the same isolation procedure had been used both before and after this period.

Genome type analysis of adenovirus 31, a potential causative agent of infants' enteritis

DNA restriction analysis with 7 endonucleases was performed on 21 adenovirus type 31 strains, isolated from faeces of infants from 1974 to 1987 in different parts of Germany. The strains could be grouped into five genome types, differing from the prototype in two to four endonucleases. BglII was the most discriminative enzyme. The D2 genome type was found 16 times; all others only once or twice. No serological differences were found between the strains.

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.

Rapid and accurate viral diagnosis

In recent years, there has been increased recognition of the importance of viral infections. In addition, new antiviral agents have become available. These factors have led to a marked increase in utilization of viral diagnostic services. In this review, both conventional and rapid methods for viral diagnosis are presented, with emphasis on recent advances. The antiviral agents currently available and the major drugs under investigation are also briefly discussed. It is hoped that this review will serve as a useful adjunct for the management of patients with virus infections.

Restriction enzyme analysis of faecal adenoviruses in Newcastle upon Tyne

Adenovirus DNA was isolated directly from virus-containing stools and digested with restriction endonucleases. The resulting fragments were separated by polyacrylamide gel electrophoresis (PAGE) and visualized by silver staining. This enabled us to assign most of the viruses detected to subgenus, serotype and, sometimes, unique strains. Although less sensitive than electron microscopy, the method allowed more information about the infecting virus to be obtained and no cultivation was necessary. Comparison with culture also allowed dual infections to be recognized. A 2-year survey of faecal adenoviruses in Newcastle upon Tyne showed that type 41 (strain 41a) was the predominant type and strain 41p was not recorded. Heterogeneity in strain 41a was also noted as found elsewhere. Adenovirus type 40 was common prior to 1985 but was absent during the last 2 years.

Helper function of adenovirus 2 for adenovirus 41 antigen synthesis in semi-permissive and non-permissive cells

Using a fluorescent focus assay, complementation and interference effects of Ad2 and Ad41 on each other in mixed infection were investigated. Ad2 provided a helper function for Ad41 late antigen synthesis in cells normally non-permissive for Ad41 growth (HEF cells), and enhanced Ad41 late antigen synthesis in semi-permissive Chang conjunctival cells. The degree of complementation by Ad2 was dependent on its input concentration. In addition, interference by Ad41 on Ad2 replication was seen in HEF cells. The degree of interference by Ad41 was dependent on the relative time of infection by each serotype. The complementation results in HEF cells suggest an absolute dependency of Ad41 on an adenovirus helper function in these cells. The results presented are consistent with the postulated helper function provided in trans by 293 cells, which are transformed by Ad5 early region 1.

Isolation and propagation of enteric adenoviruses in HEp-2 cells

Eighty-two stool samples from children with gastroenteritis in Canada, England, and Thailand which had been shown to contain adenovirus antigen (by a group-specific enzyme-linked immunosorbent assay) or adenovirus particles (by electron microscopy) or both, were tested for primary isolation of enteric adenoviruses in HEp-2 and Graham 293 cells. Graham 293 cells are known to support the replication of enteric adenovirus types (Ad40 and Ad41) on primary isolation, whereas HEp-2 cells reportedly do not. Of the 82 adenovirus isolates, 73 could be typed as Ad40 or Ad41 by type-specific monoclonal antibody enzyme-linked immunosorbent assay and by analysis of SmaI endonuclease digests. Of these 73, 30 (41%) could be isolated in HEp-2 cells, which included 43% (9/21) of those typed as Ad40 and 40% (21/52) of those typed as Ad41. On the basis of these results, the growth characteristics of adenoviruses in HEp-2 cell cultures, commonly used to distinguish enteric from nonenteric adenovirus types, are not valid for either diagnosis or epidemiological studies. For the samples studied here, use of these nondefinitive criteria would result in underestimation of the incidence of enteric adenoviruses in viral gastroenteritis.

Comparison of enteric adenovirus infection in various human cell lines

Growth of the fastidious enteric adenoviruses 40 and 41 was compared in different human cell lines. Purified virions were used to infect the following cell lines: A549; KB; Chang's conjunctiva; 293; HeLa. Both types of enteric adenovirus were infectious for each cell line, with the exception of adenovirus 40 in HeLa cells. Relatively low infectious titers were obtained from each cell type following infection with adenovirus 40 (TCID50 average = 10(-1.5)), whereas adenovirus 41 replicated to significantly higher titer (TCID50 average = 10(-3.0)). For both viruses, the highest infectious titers were obtained with A549 and KB cells. A time course experiment performed to quantitate the amount of hexon present in A549 and KB cells infected with each virus indicated that while the kinetics of accumulation were similar for both viruses, the concentration of type 41 hexon was significantly greater than that for type 40 in either cell line. The concentration of type 41 hexon was similar in each cell type; for type 40, a greater concentration of hexon was obtained in the A549 cell line than in the KB cells. The results indicate the distinct replication characteristics exhibited by adenovirus 40 are not due to a restriction in a specific host cell, and, because purified virions were used, not attributable to interference that might occur with co-infection from multiple viruses present in the same clinical specimen. We conclude the differences observed in the replication of these viruses are independent of host cell type and are associated, uniquely, with each virus.

A study of adenovirus gastroenteritis in the Tokyo area

Probable serotypes of faecal adenoviruses 40, 41, 31, 2 and 1 were found in the Tokyo area by rapid DNA restriction endonuclease analyses directly of stool specimens or after primary culture in Graham 293 cells. Some variations were found in both adenoviruses 40 and 41 by this method.

DNA hybridization for diagnosis of enteric adenovirus infection from directly spotted human fecal specimens

By using a genomic probe, DNA hybridization for adenovirus type 41 (Ad41) showed equivalent sensitivity with a direct spot method from clinical specimens compared with a more laborious DNA phenol extraction procedure. By using this direct spot preparation method, fecal specimens of 67 patients were examined under code for blind testing for the presence of adenovirus by DNA hybridization by using two Ad41 probes (genomic and cloned BglII-D) and an adenovirus type 2 genomic probe. Identical results were obtained with both of the Ad41 probes. Of the fecal specimens from 42 children with adenovirus gastroenteritis studied prospectively (16 of whom had enteric adenoviruses), 13 specimens (81%) were detected by DNA hybridization with a cloned Ad41 BglII-D probe. There were 14 fecal specimens that were positive by electron microscopy (EM) and culture for nonenteric adenovirus, and 2 specimens were positive by DNA hybridization (87% specificity); these 2 specimens may have been from a mixed enteric adenovirus and nonenteric adenovirus infection. None of 26 specimens from age-matched healthy control patients was positive for adenovirus by EM or DNA hybridization. Our data indicated that DNA hybridization gives highly reproducible results. The direct spot technique is the method of choice for specimen preparation in the diagnostic laboratory, since it requires only the simplest manipulations in specimen preparation. By using DNA hybridization with the BglII D fragment of a cloned enteric Ad41, both adenovirus type 40 and Ad41 were detected directly from fecal specimens, but it was less sensitive than EM following direct ultracentrifugation of specimens. The Bg1II-D Ad41 DNA probe was highly specific for enteric adenoviruses, and DNA hybridization with this probe could be a useful diagnostic test for these fastidious adenoviruses.

Detection of adenovirus types 40 and 41 in stool specimens by immune electron microscopy

An immune electron microscope (IEM) test was developed that allowed the direct detection of adenovirus type 40 (ad 40) or ad 41 in stools specimens. The polyclonal rabbit antisera used differentiated ad 40 and 41 from other ad serotypes but not from each other. The method was evaluated in a 13 month prospective study of stools from children with gastroenteritis. Seventy-two specimens found to contain ad by conventional electron microscope screening were retested by IEM. Results were typically obtained within 2 hr and showed that 55 (76%) viruses typed as ad 40/41. No ads were recovered from conventional virus isolation attempts on these specimens. Additionally, 39 of these 55 viruses were tested by restriction endonuclease analysis (REA) after growth in 293 cells, and results showed that all produced digest patterns typical of ad 40 (seven cases) or ad 41 (32 cases). Twenty-four percent (17/72) of viruses could not be typed by IEM; 9/17 (53%) yielded ads [ad 1 (1), ad 2 (4), ad 5 (1), ad 6 (1), ad 7 (2)] in routine culture, whereas REA identified the other eight as ad 2 (6), ad 1 (1), and ad 41 (1). The concordance between IEM and the reference methods was therefore 100% specificity and 97.5% sensitivity. The method described allows the clinically useful diagnosis of ad 40/41 infection to be rapidly made and will be a particularly useful technique in laboratories screening faeces by electron microscopy.

Development and application of monoclonal antibodies for specific detection of human enteric adenoviruses

Monoclonal antibodies were prepared against enteric adenovirus by fusing P3-NS1/-Ag4-1 mouse myeloma cells with lymphocytes from BALB/c mice immunized with enteric adenovirus 40 (Ad40) G2297. Of the several putative clones secreting antibodies to adenovirus, five were found to react specifically to the enteric adenovirus. The specificity of two of these monoclones which recognize a single antigen of a molecular size of 17 kilodaltons was evaluated against 78 clinical isolates. One monoclone (5D8/2C2) reacted with both Ad40 and Ad41, and the other monoclone (2H6/C11) recognized Ad40 only in an enzyme-linked immunosorbent assay (ELISA). These ELISA results correlated well with those of the specific neutralization test or DNA restriction endonuclease analysis or both. The use of this rapid ELISA with these monoclones will find applications in the diagnosis of enteric adenovirus and should facilitate the epidemiologic studies of enteric adenovirus gastroenteritis.

Evaluation of cell line 293 for virus isolation in routine viral diagnosis

Cell line 293, a continuous line of transformed human embryonic kidney cells, has been recognized for its sensitivity in the isolation of adenoviruses, particularly the fastidious species 40 and 41, from stool specimens. To explore the possibility of using this cell line for the isolation of other viruses from clinical specimens, 293 cells were tested for their susceptibility to a variety of viruses including herpes simplex virus, parainfluenza viruses, respiratory syncytial virus, and the enteroviruses ECHO 11, coxsackie B5, and coxsackie B6. All of the viruses induced a cytopathic effect in 293 cells. Consequently, 293 cells were introduced into the diagnostic laboratory and used along with primary African green monkey kidney (AGMK) cell cultures for the inoculation of all respiratory and stool specimens. The study represents a retrospective analysis of the performance of 293 cells over a 22-month period. It was confirmed that 293 cells were more sensitive than AGMK cells for the isolation of adenoviruses from both respiratory and stool specimens. The 293 cells were also sensitive for the isolation of enteroviruses (untyped) but more so from stool specimens than from respiratory specimens. Parainfluenza virus and respiratory syncytial virus were only rarely isolated in 293 cells. Herpesvirus isolates were obtained with equal frequency in both 293 and AGMK cells. This retrospective analysis confirms the value of 293 cells for the isolation of adenoviruses and demonstrates that 293 cells are also useful for the isolation of certain enteroviruses from both respiratory and stool specimens.

Studies on fastidious adenoviruses in Ontario: a distinct strain associated with gastroenteritis

From 100 cases of gastroenteritis among children caused by adenovirus infection in Ontario, 33 virus isolates were divided into three categories according to their biological behavior in tissue cultures. So far, the results of neutralization tests, structural protein analysis, and DNA restriction patterns showed that the virus of category 1 was similar to adenovirus type 40. However, the adenovirus of category 2 was a distinct adenovirus which shared some similarities with adenovirus type 5. Viruses of category 3 are still under investigation.