Monoclonal Antibody-based Enzyme Immunoassay Research Articles

Polymorphism rs652438 of gene <i>mmp12</i> and oxidative DNA damage in bronchial asthma: An experimental non-randomised study

Background. Personalised medicine is an avenue to create technologies for individual prognosis of the disease onset and development. The identification of individual gene haplotypes is prerequisite to detecting predispositions to multifactorial diseases. The level of serum 8-oxoguanine is an indicator of genotoxic stress underlying many pathologies.Objectives. A study of associations of mmp12 gene’s polymorphic variant rs652438 and the nature of genome oxidative damage in bronchial asthma.Methods. Genotyping of polymorphic variant rs652438 of gene mmp12 was performed using TaqMan-probe real-time PCR assays. The gene variant association with disease was assessed by odds ratio. The degree of DNA oxidative damage was estimated by 8-oxoguanine serum concentrations determined in monoclonal antibody-based enzyme immunoassays. The StatPro software package with StatTools (Palisade Corporation, USA) was used for statistical data processing.Results. The haplotype and allele frequencies were established for polymorphic locus rs652438 of the mmp12 gene in the control and bronchial asthma cohorts. Heterozygotes were shown to differ significantly; the estimate was 2.3-fold higher in the control vs. bronchial asthma (BA) cohort (p < 0.05). The AA and GG haplotype frequencies did not differ significantly. The minor allele G odds ratio (OR = 0.362, CI 95% 0.134–0.975) suggests its protective effect. This may be associated with a lowering activity of the encoded macrophage metalloelastase enzyme, which results in a poorer extracellular matrix destruction in the bronchial tree. The baseline 8-oxoG levels in the control and BA samples were 6.4 and 9.4 ng/mL, respectively (U = 25, Ucut-off = 23; p >0.05). An in vitro electromagnetic exposure of varying frequency leads to a significant oxidative genomic damage in both cohorts and an earlier reparative depletion in bronchial asthma vs. control.Conclusion. A protective effect of minor allele G against pathology has been demonstrated. Adaptations to oxidative genomic stress in bronchial asthma manifest by an impaired resistance to in vitro high-intensity electromagnetic exposures.

Development of monoclonal antibody-based enzyme immunoassay for tetranor-Prostaglandin D Metabolite

Development of monoclonal antibody-based enzyme immunoassay for tetranor-Prostaglandin D Metabolite

Development of Monoclonal Antibody-Based EIA for Tetranor-PGDM which Reflects PGD2 Production in the Body.

Tetranor-PGDM is a metabolite of PGD2. Urinary tetranor-PGDM levels were reported to be increased in some diseases, including food allergy, Duchenne muscular dystrophy, and aspirin-intolerant asthma. In this study, we developed a monoclonal antibody (MAb) and a competitive enzyme immunoassay (EIA) for measuring tetranor-PGDM. Spleen cells isolated from mice immunized with tetranor-PGDM were utilized to generate Ab-producing hybridomas. We chose hybridomas and purified MAb against tetranor-PGDM to develop competitive EIA. The assay evaluated the optimal ionic strength, pH, precision, and reliability. Specificity was determined by cross-reactivity to tetranor-PGEM, tetranor-PGFM, and tetranor-PGAM. Recovery was determined by spiking experiments on artificial urine. Optimal ionic strength was 150 mM NaCl, and optimal pH was pH 7.5. Metabolites other than tetranor-PGDM did not show any significant cross-reactivity in the EIA. The assay exhibited a half-maximal inhibition concentration (IC50) of 1.79 ng/mL, limit of detection (LOD) of 0.0498 ng/mL, and range of quantitation (ROQ) value of 0.252 to 20.2 ng/mL. The intra- and inter-assay variation for tetranor-PGDM was 3.9–6.0% and 5.7–10.4%, respectively. The linearity-dilution effect showed excellent linearity under dilution when artificial urine samples were applied to solid-phase extraction (SPE). After SPE, recovery of tetranor-PGDM in artificial urine averaged from 82.3% to 113.5% and was within acceptable limits (80%–120%). We successfully generated one monoclonal antibody and developed a sensitive competitive EIA. The established EIA would be useful for routine detection and monitoring of tetranor-PGDM in research or diagnostic body fluids.

Monoclonal antibody-based enzyme immunoassay for detection of porcine plasma in fish surimi

ABSTRACTDetection of porcine plasma using indirect ELISA was developed using mAb B4E1 for the prevention of their usage in human food that creates religious and health conflicts. The immunoassay has a CV < 20% and did not cross-react to other meat and non-meat proteins. The sensitivity of the assay is 0.25% (w/w) of porcine plasma in spiked raw and cooked fish surimi. The assay did not produce a false positive result for any of the commercial fish surimi tested that were not contain porcine plasma. Determination of a 60-kDa antigenic protein of porcine blood using Western blot confirmed its presence in the plasma fraction of the porcine blood. Further proteomic analysis involving liquid chromatography–tandem mass spectrometry (LC-MS/MS) revealed the 60-kDa protein to be porcine serum albumin.

Specific Monoclonal Antibody-Based Enzyme Immunoassay for Sensitive and Reliable Detection of Alternaria Mycotoxin Iso-Tenuazonic Acid in Food Products

In this paper, we report the development of a sensitive and specific monoclonal antibody-based immunodiagnostic method for the detection of iso-tenuazonic acid (ITeA), an Alternaria mycotoxin, in food samples. The ITeA was derivatized with hydrazine hydrate to produce the antigen (E)-3-(1-hydrazonoethyl)-4-hydroxy-5-isobutyl-1H-pyrrol-2(5H)-one (ITeAH) which was further reacted with glyoxalic acid to generate the hapten (E)-2-((Z)-(1-(4-hydroxy-5-isobutyl-2-oxo-2,5-dihydro-1H-pyrrol-3-yl)ethylidene) (ITeAHGA) which was used as an immunogen after conjugation to bovine serum albumin (BSA). A highly specific monoclonal antibody selectively binding to ITeAH was generated via the hybridoma technique and subsequently used to construct a heterologous indirect competitive enzyme-linked immunosorbent assay (icELISA) using ITeAH as the competitive antigen for the detection of ITeA with a limit of detection (LOD) of 0.5 ng/mL. Under the optimum conditions, the developed icELISA is highly sensitive (IC50 = 7.8 ng/mL) with recovery rates ranged from 82.3 to 109.8% for spiked food samples. The comparative analysis of results revealed a good correlation between the icELISA and the standard HPLC-MS/MS method, confirming the suitability of the developed icELISA for screening and detection of mycotoxin ITeA in food samples.

Specific allergen profiles of peanut foods and diagnostic or therapeutic allergenic products

Generic immunoassays for peanut cannot discriminate between allergen levels in peanut-derived food products or therapeutics. Clinical trials of oral immunotherapy (OIT) are strengthened by using standardized peanut preparations with defined doses of major allergens. This article describes measurement of Ara h 1, Ara h 2, and Ara h 6 in peanut foods and in peanut flour extracts used for allergy diagnosis and OIT. Monoclonal antibody-based enzyme immunoassays for Ara h 1, Ara h 2, and Ara h 6 were used to compare allergen levels in peanut (n=16) and tree nut (n=16) butter, peanut flour (n=11), oils (n=8), extracts used for diagnosis and OIT (n=5), and the National Institute for Standards and Technology Peanut Butter Standard Reference Material 2387. Roasted peanut butters contained 991 to 21,406μg/g Ara h 1 and exceeded Ara h 2 and Ara h 6 levels by 2- to 4-fold. Similarly, National Institute for Standards and Technology Peanut Butter Standard Reference Material 2387 contained 11,275μg/g Ara h 1, 2,522μg/g Ara h 2, and 2,036μg/g Ara h 6. In contrast, peanut flours contained 787 to 14,631μg/g Ara h 2 and exceeded Ara h 1 levels by 2- to 20-fold. Flour extracts used for OIT contained 394 to 505μg/mL Ara h 1, 1,187 to 5,270μg/mL Ara h 2, and 1,104 to 8,092μg/mL Ara h 6. In most cases specific peanut allergens were not detected in tree nut butters or peanut oils. The results show marked differences in specific peanut allergen profiles in peanut butter and flour and peanut preparations for clinical use. Roasting can increase Ara h 1 levels in peanut butter. Variability in allergen levels could affect the outcome of clinical trials of peanut OIT, especially with respect to Ara h 1. Specific allergen measurements will improve standardization and provide accurate dosing of peanut preparations that are being used for OIT.

Prevalence of viral gastroenteritis in children with acute gastroenteritis in Babol, Iran

Viral gastroenteritis is considered a significant cause of death and is a common cause of hospitalization worldwide. This study was performed to assess the role of rota, adeno and astrovirus in children with acute diarrhea in one main children's hospital in Amirkola, Babol North of Iran. In this cross-sectional study, stool specimens from 208 children suffering from acute diarrhea referred to Amirkola children's hospital were tested for the presence of rota, adeno and astrovirus by a monoclonal antibody-based enzyme immunoassay. Demographic data were gathered by a questionnaire. The prevalence of viral causes of acute gastroenteritis was reported by relative frequency. Rota, adeno and astrovirus antigens were detected in 61.1%, 2.9% and 2.4% of patients respectively. Infants between 6 and 12 months of age were most frequently affected by rotavirus (29.8%) ( P< 0.03). Rotavirus infection was significantly less frequent in summer and spring than winter and autumn ( P< 0.0001). No significant difference was observed in rotavirus infection between male and female but the prevalence of adenovirus in girls was significantly higher than boys ( P< 0.05). Rotavirus can be regarded as a major etiologic agent of acute diarrhea in children less than two years old at Amirkola children's hospital, Babol. Immunization may protect the children before their first symptomatic infection.

An ultra-sensitive monoclonal antibody-based competitive enzyme immunoassay for sterigmatocystin in cereal and oil products.

Sterigmatocystin (STG), a biosynthesis precursor of aflatoxin B1, is well known for its toxic and carcinogenic effects in humans and animals. STG derivatives and protein conjugates are needed for generation of monoclonal antibodies (mAbs). This work describes a reliable and fast synthesis of novel STG derivatives, based on which novel STG bovine serum albumin conjugates were prepared. With the novel STG bovine serum albumin conjugates, three sensitive and specific mAbs against STG, named VerA 3, VerA 4, and VerA 6, were prepared by semi-solid hypoxanthine/aminopterin/thymidine (HAT) medium using a modified two-step screening procedure. They exhibited high affinity for STG and no cross-reactivity (CR) with aflatoxins B1, B2, G1, G2, and M1. Based on the most sensitive antibody VerA 3, an ultra-sensitive competitive enzyme-linked immunosorbent assay (ELISA) was developed for STG in wheat, maize, and peanuts. Assays were performed in the STG-GA-BSA-coated (0.5 µg·mL−1) ELISA format, in which the antibody was diluted to 1∶80,000. Several physicochemical factors influencing assay performance, such as pH, ionic strength, blocking solution, and diluting solution, were optimized. The final results showed that the assays had the detection limits of 0.08 ng·g−1 for wheat, 0.06 ng·g−1 for maize, and 0.1 ng·g−1 for peanuts, inter-assay and intra-assay variations of less than 10%, and recoveries ranging from 83% to 110%. These recoveries were in good agreement with those obtained by using HPLC-MS/MS method (90–104%), indicating the importance of the mAb VerA 3 in the study of STG in crude agricultural products.

Circulation of group A rotaviruses among neonates of human, cow and pig: study from Assam, a north eastern state of India

Rotavirus (RV) infections are worldwide in distribution causing high morbidity and mortality in human and animal neonates. Human settlements in close proximity of animals aids for genetic re-assortment of the virus by interspecies transmission and consequent emergence of new viral antigenic strain. Therefore, the present study was designed to explore RV incidence in a single approach from human and animal neonates sharing similar environment. Altogether, 200 diarrheal samples from children (50), piglets (80) and calves (70) were collected during the year of 2010-2012 from various locality, farms and hospitals, initially screened through monoclonal antibody based enzyme immunoassay followed by RNA-PAGE and VP7 gene amplification by Reverse transcription PCR. The overall prevalence of rotavirus was found to be 41.5% (83/200) where maximum numbers of positive cases were found in piglets (46.3%) followed by human (40%) and cow (37.1%). Majority of samples demonstrated characteristic group A rotavirus (RVA) electropherotype of 4:2:3:2 pattern. Moreover, RNA profiles of seven samples from piglets and calves revealed variation in the migration pattern of class II, III and class IV segments. The study, for the first time from the valley, detected 43.7% of neonatal RVA positive cases from human and animal sharing similar setting. The variation in RNA migration pattern in seven cases signifies tentative cases of gene re-assortment that warrant further evaluation.

Detection and partial characterization of norovirus among children with acute gastroenteritis in Lagos, Nigeria

Norovirus (NoV) has captured increasing attention as an agent of childhood diarrhea, but its incidence in developing countries such as Nigeria has been underreported. This study was conducted to investigate the role of NoVs in sporadic cases of acute diarrhea among hospitalized children. One hundred and eighty-eight (188) specimens comprising 161 diarrheic and 27 non-diarrheic stools were randomly selected from 668 stools previously screened for rotaviruses. These specimens were collected from children under 5 years of age who were hospitalized between November 2007 and May 2008 in Lagos, Nigeria. The specimens were examined for NoV antigen using monoclonal antibody-based enzyme immunoassay (EIA), and the positive specimens were further characterized for norovirus genogroups using reverse transcription-Polymerase chain reactions (RT-PCR) technique. NoV was detected in 60/161 (37.3%) of diarrhoeal and 1(3.7%) of non diarrhoeal children tested. Noroviruses were detected throughout the study period with most patients infected in age group 6 - 12 months. More males were infected with NoV than females however, the difference was not significant (χ2 = 0.983, p ≥ 0.05). Sixteen among the positive samples were amplified by PCR using specific primers, of these, 5 (31%) were typed to be GI, 8 (50%) were GII and three samples (19%) showed a mixed infection of norovirus GI and GII genogroups. This study confirmed the relevance of NoV as a causative agent of pediatric diarrhoea and reported norovirus genogroup GII as the predominant type in circulation in Lagos, Nigeria. Key words: Diarrhoea, norovirus, RT-PCR, children, Nigeria.

Determination of Alt a 1 (Alternaria alternata) in poultry farms and a sawmill using ELISA

Farm and sawmill workers are exposed to high levels of allergenic fungi, such as Alternaria alternata, which are associated with respiratory diseases and asthma. The aim of this study was to measure the concentration of Alt a 1, a major allergen of A. alternata, in indoor dust samples collected in poultry farms and a sawmill using a monoclonal antibody-based enzyme immunoassay. A total of 45 dust samples were collected in poultry farms (30) and the sawmill (15) in Zagreb County (Croatia). The Alt a 1 allergen was detected in all dust samples (100%) collected in three poultry farms. The levels of Alt a 1 were in the range of 0.1–14 μg/g, and the median value was 0.37 μg/g. About 86% of dust samples contained Alt a 1 in the range of 0.1–1.0 μg/g. In the sawmill, no detectable level of Alt a 1 was found (limit of detection =0.12 μg/g). This study has shown that occupational exposure to Alt a 1 allergen in poultry farms deserves monitoring.

Rotavirus-associated neonatal necrotizing enterocolitis

Purpose : This study aimed to test whether rotavirus-associated necrotizing enterocolitis (RV+NEC) produced different clinical findings or outcomes from those of non-rotavirus necrotizing enterocolitis (RV-NEC). Methods : Eight patients from the RV+NEC group and 22 patients from the RV-NEC group diagnosed with modified Bell stage II or higher NEC were selected for this study. Fecal specimens from all infants were tested for rotavirus infection using a monoclonal antibody-based enzyme immunoassay (EIA). Clinical, radiographic, and clinical outcome data were analyzed retrospectively. Results : RV+NEC infants had a significantly higher birth weight and were born at a significantly higher gestational age (33.53.3 weeks vs. 29.34.4 weeks; P=0.01). There were no differences in the occurrence of thrombocytopenia, mural gas, and pneumoperitoneum between the 2 groups. However, portal vein gas was more common in the RV+NEC group (88% vs. 9%; P

Determination of Alt a 1 (Alternaria alternata) in poultry farms and a sawmill using ELISA

Farm and sawmill workers are exposed to high levels of allergenic fungi, such as Alternaria alternata, which are associated with respiratory diseases and asthma. The aim of this study was to measure the concentration of Alt a 1, a major allergen of A. alternata, in indoor dust samples collected in poultry farms and a sawmill using a monoclonal antibody-based enzyme immunoassay. A total of 45 dust samples were collected in poultry farms (30) and the sawmill (15) in Zagreb County (Croatia). The Alt a 1 allergen was detected in all dust samples (100%) collected in three poultry farms. The levels of Alt a 1 were in the range of 0.1-14 microg/g, and the median value was 0.37 microg/g. About 86% of dust samples contained Alt a 1 in the range of 0.1-1.0 microg/g. In the sawmill, no detectable level of Alt a 1 was found (limit of detection =0.12 microg/g). This study has shown that occupational exposure to Alt a 1 allergen in poultry farms deserves monitoring.

Diagnosis of human rotavirus in stool specimens: comparison of different methods

A total of 345 stool specimens of hospitalized children below 5 years of age with acute gastroenteritis were tested for the presence of rotavirus by Polyacrylamide gel electrophoresis (PAGE), a monoclonal antibody based enzyme immunoassay (EIA) and a latex agglutination test (LAT). Detection rate for PAGE and EIA were 24.9% (345/86) and 20.9% (345/70) respectively. Using PAGE as the standard, the sensitivity and specificity of EIA were 75.6% and 98.1% respectively. The sensitivity of LAT was 70.9% with 100% specificity (LAT was done in only PAGE positive specimens). LAT appeared as the simplest and economic for both bed side and field use.

Adenovirus infection in children with diarrhea disease in Northwestern Nigeria

Adenoviruses, particularly enteric adenoviruses (EAds) type 40 (Ad40) and type 41(Ad41), can cause acute and severe diarrhea in young children worldwide. This study was conducted to delineate the epidemiological features of adenoviruses identified in children with gastroenteritis in Northwestern Nigeria. All 282 specimens comprising 248 diarrheic and 34 non-diarrheic stools were randomly selected from 1063 stools previously analyzed for rotaviruses. These specimens were collected between July 2002 and July 2004 from children < 5 years of age. The specimens were screened for the presence of adenoviruses using monoclonal antibody-based Enzyme Immuno Assay (EIA), (Adenovirus RIDASCREEN r-Biopharm, UK) and the positive specimens were further examined for Ad40 and Ad41 using Premier Adenoclone -Type 40/41 EIA (Meridian Biosciences, USA). Negative staining electron microscopy was performed on selected specimens to confirm the presence of adenovirus particles. Adenovirus antigen was detected in 63/282 (23%) of the diarrheic diarrheic and in 6/34 (17.6%) of the non-diarrheic specimens. Adenoviruses were detected throughout the study period with most patients infected in the age group 25-36 months. The male-to-female ratio was 2.2:1 (43/20). Clinical features included fever (60%: 38/63), vomiting (56%: 35/63), mild dehydration (49%: 31/63), symptoms of upper respiratory tract infection (13%: 8/63) and abdominal pain (5%: 3/63). Analysis of stool specimen in adenovirus infected patients showed watery diarrhea in 87% (55/63), diarrhea with mucus in 19% (12/63) and diarrhea with mucus and blood in 3% (2/63). Ten (10) percent of the children were hospitalized due to gastroenteritis while 9 patients (14.3%) had co-infections with rotavirus. Human EAds were detected in 8% of specimens mainly in the dry season and among children older than 2 years. The principal symptoms were diarrhea (100%), dehydration (80%) and fever (80%). The findings of this study suggest that adenoviruses are important etiologic agents of gastroenteritis in Northwestern Nigerian children.

Sensitization and exposure to house dust and storage mites in high-altitude areas of Ecuador

Few studies have addressed exposure and sensitization to mite allergens in Andean countries. To identify the main mite species in 3 locations at different altitudes in Ecuador and to verify skin test reactivity to various mite species in allergic individuals in Quito, Ecuador. Mattress dust samples were collected in Quito (2,800 m above sea level), Cuenca (2,500 m above sea level), and Guayaquil (sea level). Mite species present in the samples were isolated, identified, and counted. Der p 1 and Der f 1 levels were measured using monoclonal antibody-based enzyme immunoassays. Four hundred thirty-five patients in Quito diagnosed as having allergic rhinitis or asthma underwent skin testing with commercial extracts of Dermatophagoides pteronyssinus, Dermatophagoides farinae, Blomia tropicalis, Tyrophagus putrescentiae, and Lepidoglyphus destructor. In addition, Glycyphagus domesticus, Acarus siro, and Aleuroglyphus ovatus were tested in 362, 262, and 279 patients, respectively. Twenty-one mite species were identified. Large populations of mites were detected above 2,500 m of altitude. All the dust samples contained detectable levels of Der p 1 or Der f 1. Positive skin prick test reactions to D. pteronyssinus, D. farinae, B. tropicalis, L. destructor, T. putrescentiae, A. ovatus, A. siro, and G. domesticus were obtained in 60.9%, 56.8%, 17.0%, 19.3%, 10.6%, 15.8%, 8.8%, and 11.0% of the patients, respectively. Most analyzed mattresses contained several species of mites. Mite allergen levels were high. This study confirms the importance of house dust and storage mite allergens in Ecuador in areas above 2,500 m of altitude, where humidity remains high year round.

Stool antigen tests for the detection of Helicobacter pylori in children

Stool specimens from 102 children (median age = 6.0 years; Helicobacter pylori in biopsy specimens, n = 43) were tested for H. pylori with the monoclonal antibody–based enzyme immunoassay HpStar. In 28 cases, the specimen was obtained with a rectal cotton swab during endoscopy. The sensitivity and specificity of the HpStar were 0.95 and 0.90, respectively, as compared with biopsy-based methods. The rectal cotton swab specimen gave accurate results in 24 of the 28 cases. Storage of specimens for 1, 3, or 7 days ( n = 6) had a minor effect on the results, but one specimen's originally positive value on borderline turned negative when it was kept in room temperature. Forty-eight specimens were tested in parallel with all 3 tests used: HpStar, Premium Platinum HpSA, and the rapid test ImmunoCardSTAT! The accuracy rates of the tests were 98% for the HpSA and HpStar and 96% for the ImmunoCardSTAT! The performance of the stool antigen tests was excellent in young children.

Role of rotaviruses in children with acute diarrhea in Tehran, Iran.

Rotavirus illness is associated with significant cause of morbidity and is a common cause of hospitalization worldwide. This study was performed to assess the role of rotaviruses in children presenting with acute diarrhea in two main Children's Medical Centers and one general hospital in Tehran. Stool specimens from 704 children less than 5 years of age suffering from diarrhea were tested for the presence of rotaviruses by a monoclonal antibody-based enzyme immunoassay. A total of 176 fecal specimens collected from healthy children in similar age group were studied as controls. Rotavirus antigen was detected in 15.3% of patients. Infants between 6 and 12 months of age were most frequently affected. Rotavirus infection was significantly less frequent in breast-fed than among bottle-fed babies. Watery diarrhea was present in 68.5% of children. Detection rate was highest in the spring and lowest in summer. Rotavirus can be regarded as a major etiologic agent of acute diarrhea in infants and children up to 5-years-old in Iran, immunization at birth may protect the children before their first symptomatic infection.

An ELISA procedure for human Lp(a) quantitation using monoclonal antibodies.

The present study describes a monoclonal antibody-based enzyme immunoassay (ELISA) for the quantitation of lipoprotein(a), Lp(a), in human plasma. Two antibodies to Lp(a), 2F4E7 and 8G12G7, were produced and characterized as specific and high affinity antibodies against Lp(a). A reference control serum was utilized to prepare the standard curve in a Lp(a) concentration range from 0.015 to 0.5 ug/ml. A biotinylated monoclonal antibody against apoB-LDL was used as the second antibody. The comparison of the standardized ELISA using mAb 2F4E7 with an ELISA using a characterized mAb against Lp(a) (clone KO9) as capture antibody showed that the Lp(a) concentration of two standard sera was similar with both assays. Furthermore, when compared with an electroimmunoassay kit, similar Lp(a) concentrations for the standard were also obtained.

Neonatal rotavirus infection in Belém, northern Brazil: nosocomial transmission of a P[6] G2 strain.

A total of 614 fecal specimens were obtained during a survey for rotavirus infection conducted between May 1996 and May 1998 among 437 newborns admitted to special care nurseries at a public hospital in the urban area of Belém, Brazil. Routine stool samples were taken weekly from all babies up to the age of 28 days. Overall, 51 (11.7%) of the neonates excreted rotaviruses while in hospital, of whom 42 (82.3%) developed asymptomatic nosocomial infection; nosocomial infection was also proved in five of the nine patients with diarrhea. Three distinct RNA profiles were detected, of which one short electropherotyping pattern was far more frequent ( approximately 90% of the strains). Using monoclonal antibody-based enzyme immunoassays, 32 (62.7%) of the rotavirus-positive strains were classified as G2, and 1 (1.9%) as mixed G1 and G2. A G serotype could not be assigned to 18 (35.3%) of the isolates. A reverse transcription-polymerase chain reaction was used for determining the VP4 type-specificity of a subset of 28 rotavirus-positive samples. Characterization of the VP7-genotype specificity was also sought for 18 of these latter strains. Overall, P[6] and G2 genotypes were identified in 93% and 94% of tested samples respectively, with results being further confirmed by Southern hybridization. Although surveillance was conducted during a 25-month period, 50 (98%) of 51 rotavirus isolates clustered between January and December 1997. The earliest [P6]G2 rotavirus infections were detected by late January 1997, involving two (13- and 14-day-old) babies admitted with acute diarrhea. Thereafter, strains bearing these genotype specificities were identified among five infants with hospital-acquired gastroenteritis, followed by 16 others who were infected asymptomatically. This is the first report from Brazil describing nosocomial transmission of P[6]G2 rotavirus strains among neonates.