J Flores

Bio: J Flores is an academic researcher from Centers for Disease Control and Prevention. The author has contributed to research in topics: Gene & Typing. The author has an hindex of 1, co-authored 1 publications receiving 1297 citations.

Identification of group A rotavirus gene 4 types by polymerase chain reaction.

Abstract: Five genetically distinct human rotavirus (HRV) gene 4 groups have been described on the basis of comparative nucleotide sequencing and the predicted amino acid sequences, and at least four of them represent distinct VP4 antigenic types. To identify each gene 4 type and investigate its distribution in HRV isolates from patients with diarrhea, we developed a polymerase chain reaction (PCR) typing method using sequence information available for four genetically distinct gene 4 types. Rotavirus double-stranded RNAs (dsRNAs) isolated from stool samples were first reverse transcribed and amplified by PCR by using two oligonucleotide primers that correspond to regions that are highly conserved among all known HRV gene 4 types. The 876-bp dsDNA products were then reamplified by PCR in the presence of a cocktail containing one conserved plus-sense primer and four type-specific minus-sense primers (selected from the hypervariable region of gene 4), resulting in products of 345, 483, 267, and 391 bp corresponding to gene 4 types 1, 2, 3, and 4, respectively. This method reliably identified the gene 4 types of 16 well-characterized HRV isolates. Our results were independently confirmed for all 16 strains by reverse transcription and PCR amplification of HRV dsRNA in the presence of alternate type-specific primer pairs. For direct gene 4 typing of HRV in stool samples, we developed a method to extract rotavirus dsRNA from stool specimens by using glass powder. Our results suggest that gene 4 typing will be useful in providing more a complete characterization of HRV strains of epidemiologic or vaccine-related interest.

Serotype diversity and reassortment between human and animal rotavirus strains: implications for rotavirus vaccine programs.

Abstract: The development of rotavirus vaccines that are based on heterotypic or serotype-specific immunity has prompted many countries to establish programs to assess the disease burden associated with rotavirus infection and the distribution of rotavirus strains. Strain surveillance helps to determine whether the most prevalent local strains are likely to be covered by the serotype antigens found in current vaccines. After introduction of a vaccine, this surveillance could detect which strains might not be covered by the vaccine. Almost 2 decades ago, studies demonstrated that 4 globally common rotavirus serotypes (G1-G4) represent >90% of the rotavirus strains in circulation. Subsequently, these 4 serotypes were used in the development of reassortant vaccines predicated on serotype-specific immunity. More recently, the application of reverse-transcription polymerase chain reaction genotyping, nucleotide sequencing, and antigenic characterization methods has confirmed the importance of the 4 globally common types, but a much greater strain diversity has also been identified (we now recognize strains with at least 42 P-G combinations). These studies also identified globally (G9) or regionally (G5, G8, and P2A[6]) common serotype antigens not covered by the reassortant vaccines that have undergone efficacy trials. The enormous diversity and capacity of human rotaviruses for change suggest that rotavirus vaccines must provide good heterotypic protection to be optimally effective.

Characterization of rotavirus strains from newborns in New Delhi, India.

Abstract: Between 1986 and 1993, 72% of rotavirus strains isolated from newborns at five hospitals in New Delhi, India, had long electropherotypes, subgroup II VP6 antigens, and G and P genotypes (G9P11) identical to those of prototype strain 116E A novel strain with a G9P6 genotype, representing 13% of the isolates, was identified These results demonstrate that G9P11 and G9P6 rotavirus strains are common in nurseries in New Delhi

Review Of G And P Typing Results From A Global Collection Of Rotavirus Strains: Implications For Vaccine Development

Abstract: Candidate rotavirus vaccines have been prepared with reassortant strains specifically to protect against the 4 major rotavirus G serotypes (G1 -4). Many studies using P (VP4) genotyping methods have indicated that, worldwide, rotavirus strains of the 4 common G serotypes are each associated with 1 P genotype: GI, G3, and G4 are associated with P[8], and G2 is associated with P[4]. In contrast, G and P genotyping of rotavirus in specimens from India revealed that a high percentage of the childhood diarrhea strains belong to genotype P[6], and the most common strain had an unusual G serotype, G9. Similarly, in all regions surveyed in Brazil, apparent reassortants of genotype P[8], G5 were found in children with gastroenteritis. These studies indicate that while rotavirus strains have limited diversity in many settings, reassortment between common and uncommon serotypes or animal strains can arise in some settings and, thus, lead to unusual diversity.