Biomedical subjects

R Rico-Hesse

Publications and source records attributed to R Rico-Hesse.

24 records · Page 2Linked to original sources

PubMed1991

Molecular evolution of eastern equine encephalomyelitis virus in North America.

We examined the rate and spatial pattern of eastern equine encephalomyelitis virus (EEEV) evolution in North America using primer-extension sequencing of viral RNA. Nucleotide sequences of the entire 26 S structural gene region of four EEEV strains revealed remarkable conservation between 1933 and 1985, with an estimated 0.7% divergence or 1.4 x 10(-4) nucleotide substitutions per site per year. Sequences from smaller 26 S regions of nine additional strains suggested that EEEV evolves in North America in a single lineage, with genetic exchange regularly occurring among enzootic transmission foci. In these limited 26 S genome regions, only synonymous nucleotide substitutions became fixed between 1933 and 1988, implying a high degree of conservation in protein structure. Short nucleotide sequences from a Panamanian, South American variety isolate revealed a relatively distant relationship to North American serotype viruses. This suggested genetic divergence between antigenic varieties, and independent evolution of EEEV in North and South America. Factors related to replication and epidemiology of EEEV, which may constrain its evolution in nature, are discussed. Possible mechanisms of genetic exchange among enzootic foci are also considered.

Amino Acid Sequence↗

PubMed1990

Molecular evolution and distribution of dengue viruses type 1 and 2 in nature.

During the past several decades, dengue viruses have progressively extended their geographic distribution, and are currently some of the most important mosquito-borne viruses associated with human illness. Determining the genetic variability and transmission patterns of these RNA viruses is crucial in developing effective control strategies for the disease. Primer-extension sequencing of less than 3% of the dengue genome (across the E/NS1 gene junction) provided sufficient information for estimating genetic relationships among 40 dengue type 1 and 40 type 2 virus isolates from diverse geographic areas and hosts. A quantitative comparison of these 240-nucleotide-long sequences revealed previously unrecognized evolutionary relationships between disease outbreaks. Five distinct virus genotypic groups were detected for each of the two serotypes. The evolutionary rates of epidemic dengue viruses of types 1 and 2 were similar, although the transmission pathways of these viruses around the world are different. For dengue type 2, one genotypic group represents an isolated, forest virus cycle which seems to have evolved independently in West Africa. This is the first genetic evidence of the existence of a sylvatic cycle of dengue virus, which is clearly distinct from outbreak viruses.

Amino Acid Sequence↗

PubMed1990

Genetic variation of Japanese encephalitis virus in nature.

Forty-six strains of Japanese encephalitis (JE) virus from a variety of geographic areas in Asia were examined by primer-extension sequencing of the RNA template. A 240 nucleotide sequence from the pre-M gene region was selected for study because it provided sufficient information for determining genetic relationships among the virus isolates. Using 12% divergence as a cutoff point for virus relationships, the 46 isolates fell into three distinct genotypic groups. One genotypic group consisted of JE virus isolates from northern Thailand and Cambodia. A second group was composed of isolates from southern Thailand, Malaysia, Sarawak and Indonesia. The remainder of the isolates, from Japan, China, Taiwan, the Philippines, Sri Lanka, India and Nepal, made up a third group. The implications of these findings in relation to the epidemiology of JE are discussed. Results of this study demonstrate that the comparison of short nucleotide sequences can provide insight into JE virus evolution, transmission and, possibly, pathogenesis.

Animals↗

PubMed1988

Monoclonal antibodies define antigenic variation in the ID variety of Venezuelan equine encephalitis virus.

Three monoclonal antibodies were generated that are specific for the E2 glycoprotein of Venezuelan equine encephalitis (VEE) virus and have useful reactivities in an enzyme-linked immunosorbent assay (ELISA). Antibody 1A1B-9 distinguished between the IC (epizootic) and ID (enzootic) varieties of VEE virus by ELISA. Clone 7A1A-1 antibody distinguished the Panamanian prototype virus (3880) from Colombian ID isolates by a 500-fold difference in titer by endpoint ELISA, and it detected antigenic variation in ID isolates from southern Colombia and Ecuador. Antibody 7A3A-4 defined a cryptic antigenic site on the latter two isolates. These monoclonal antibodies complement others in identifying VEE isolates by a simple ELISA.

Animals↗

PubMed1988

Genetic variation of Venezuelan equine encephalitis virus strains of the ID variety in Colombia.

To determine the degree of genetic variation within one serologic group of Venezuelan equine encephalitis virus and the relatedness of viruses with different epidemiologic backgrounds isolated within the same country, virion RNA from 16 isolates belonging to subtype I were compared by RNase T1 oligonucleotide fingerprinting. RNA fingerprints of 12 enzootic isolates showed a large degree of heterogeneity, even though they were serologically indistinguishable. A reference enzootic strain from Colombia showed more genetic relatedness to three epizootic strains isolated in the same country, than to its own serogroup prototype strain isolated in Panama. Thus, genetic relatedness within Venezuelan equine encephalitis strains in Colombia seems to be a function of geography rather than epidemiology.

Animals↗

PubMed1987

Geographic distribution of wild poliovirus type 1 genotypes.

Determination of the patterns of genomic variation among RNA virus isolates is a powerful approach for establishing their epidemiologic interrelationships. The standard technique for such studies, ribonuclease T1 oligonucleotide fingerprinting, can detect similarities only among very closely related isolates. The rapid evolution of the poliovirus genome during transmission in humans requires the application of alternate methods to identify more distant relationships. To obtain a substantially broader view of the distribution of wild poliovirus type 1 genotypes in nature, we compared 150 bases of genomic sequence information (encoding parts of the capsid protein VP1 and the noncapsid protein 2A) from 62 isolates obtained from poliomyelitis patients in five continents. The partial sequence information allowed us to (1) identify numerous geographic foci of endemic circulation of wild type 1 polioviruses, (2) reveal previously unsuspected links between cases in distant communities, (3) monitor the displacement from the environment of preexisting polioviruses by viruses from other regions, and (4) recognize the recombinant (vaccine-wild; wild-wild) origins of some epidemic polioviruses.

Base Sequence↗