Prevalence and molecular characterization of Rickettsia spp. from wild small mammals in public parks and urban areas of Bangkok Metropolitan, Thailand

Rural areas usually show a higher prevalence of rickettsial infection than urban areas. However, information on the rickettsial infection status in urban settings (e.g., built-up areas and city parks) is still limited, particularly in the Bangkok metropolitan area. In this study, we performed a molecular rickettsial survey of spleen samples of small mammals caught in public parks and built-up areas of Bangkok. Out of 198 samples, the Rattus rattus complex was found to be most prevalent. The amplification of rickettsial gltA fragment gene (338 bp) by nested PCR assay revealed positive results in four samples, yielding a low prevalence of infection of 2.02%. DNA sequencing results confirmed that three samples were matched with Rickettsia typhi, and one was identified as R. felis. It is noteworthy that this is the first report of the occurrence of R. felis DNA in rodents in Southeast Asia

Prevalence and Molecular Characterization of Rickettsia spp. from Wild Small Mammals in Public Parks and Urban Areas of Bangkok Metropolitan, Thailand

Rural areas usually show a higher prevalence of rickettsial infection than urban areas. However, information on the rickettsial infection status in urban settings (e.g., built-up areas and city parks) is still limited, particularly in the Bangkok metropolitan area. In this study, we performed a molecular rickettsial survey of spleen samples of small mammals caught in public parks and built-up areas of Bangkok. Out of 198 samples, the Rattus rattus complex was found to be most prevalent. The amplification of rickettsial gltA fragment gene (338 bp) by nested PCR assay revealed positive results in four samples, yielding a low prevalence of infection of 2.02%. DNA sequencing results confirmed that three samples were matched with Rickettsia typhi, and one was identified as R. felis. It is noteworthy that this is the first report of the occurrence of R. felis DNA in rodents in Southeast Asia.</jats:p

Prevalence and Molecular Characterization of Rickettsia spp. from Wild Small Mammals in Public Parks and Urban Areas of Bangkok Metropolitan, Thailand

International audienceRural areas usually show a higher prevalence of rickettsial infection than urban areas. However, information on the rickettsial infection status in urban settings (e.g., built-up areas and city parks) is still limited, particularly in the Bangkok metropolitan area. In this study, we performed a molecular rickettsial survey of spleen samples of small mammals caught in public parks and built-up areas of Bangkok. Out of 198 samples, the Rattus rattus complex was found to be most prevalent. The amplification of rickettsial gltA fragment gene (338 bp) by nested PCR assay revealed positive results in four samples, yielding a low prevalence of infection of 2.02%. DNA sequencing results confirmed that three samples were matched with Rickettsia typhi, and one was identified as R. felis. It is noteworthy that this is the first report of the occurrence of R. felis DNA in rodents in Southeast Asia

Differential Modulation of prM Cleavage, Extracellular Particle Distribution, and Virus Infectivity by Conserved Residues at Nonfurin Consensus Positions of the Dengue Virus pr-M Junction▿

In the generation of flavivirus particles, an internal cleavage of the envelope glycoprotein prM by furin is required for the acquisition of infectivity. Unlike cleavage of the prM of other flaviviruses, cleavage of dengue virus prM is incomplete in many cell lines; the partial cleavage reflects the influence of residues at furin nonconsensus positions of the pr-M junction, as flaviviruses share basic residues at positions P1, P2, and P4, recognized by furin. In this study, viruses harboring the alanine-scanning and other multiple-point mutations of the pr-M junction were generated, employing a dengue virus background that exhibited 60 to 70% prM cleavage and a preponderance of virion-sized extracellular particles. Analysis of prM and its cleavage products in viable mutants revealed a cleavage-suppressive effect at the conserved P3 Glu residue, as well as the cleavage-augmenting effects at the P5 Arg and P6 His residues, indicating an interplay between opposing modulatory influences mediated by these residues on the cleavage of the pr-M junction. Changes in the prM cleavage level were associated with altered proportions of extracellular virions and subviral particles; mutants with reduced cleavage were enriched with subviral particles and prM-containing virions, whereas the mutant with enhanced cleavage was deprived of these particles. Alterations of virus multiplication were detected in mutants with reduced prM cleavage and were correlated with their low specific infectivities. These findings define the functional roles of charged residues located adjacent to the furin consensus sequence in the cleavage of dengue virus prM and provide plausible mechanisms by which the reduction in the pr-M junction cleavability may affect virus replication

Influence of pr-M Cleavage on the Heterogeneity of Extracellular Dengue Virus Particles▿

During dengue virus replication, an incomplete cleavage of the envelope glycoprotein prM, generates a mixture of mature (prM-less) and prM-containing, immature extracellular particles. In this study, sequential immunoprecipitation and cryoelectron microscopy revealed a third type of extracellular particles, the partially mature particles, as the major prM-containing particles in a dengue serotype 2 virus. Changes in the proportion of viral particles in the pr-M junction mutants exhibiting altered levels of prM cleavage suggest that the partially mature particles may represent an intermediate subpopulation in the virus maturation pathway. These findings are consistent with a model suggesting the progressive mode of prM cleavage