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In this study, we examined various brain suspension concentrations and viral loads in Neuro-2a cell cultures using 20 rabies-positive bovine samples. The reproducibility of results varied: 65% showed consistent outcomes across all concentrations, while 35% disagreed in at least one. Viral titers ranged from less than 25 × 10 1 to 25 × 10 3.50 TCID 50 /mL, with 20% below 25 × 10 1 TCID 50 /mL. Concentrations between 5% and 20% yielded over 90% agreement in positive results, but at 30%, agreement dropped from 85% to 50%. Cell confluence was successfully maintained at 5%, 10%, and 20%, while concentrations of 30% and above led to confluence loss. Low viral loads also negatively impacted reproducibility. These results suggest that sample concentration has a direct influence on preservation of cell confluence and that low viral loads may influence the reproducibility of the rabies tissue culture infection test (RTCIT)., (© 2023. The Author(s), under exclusive licence to Springer-Verlag GmbH Austria, part of Springer Nature.)

Serum samples of 638 free-ranging wild mammals from São Paulo state, Brazil, were tested for neutralizing antibodies against rabies virus by the rapid fluorescent focus inhibition test. Overall seroprevalence was 1.7% among 24 species surveyed, with individuals of six species having positive results indicating exposure to rabies virus., (© Wildlife Disease Association 2022.)

Here, we compared the growth kinetics, cell-to-cell spread, and virus internalization kinetics in N2a cells of RABV variants isolated from vampire bats (V-3), domestic dogs (V-2) and marmosets (V-M) as well as the clinical symptoms and mortality caused by these variants. The replication rate of V-3 was significantly higher than those of V-2 and V-M. However, the uptake and spread of these RABV variants into N2a cells were inversely proportional. Nevertheless, V-3 had longer incubation and evolution periods. Our results provide evidence that the clinical manifestations of infection with bat RABV variant occur at a later time when compared to what was observed with canine and marmoset rabies virus variants.

This study describes the results of the sequencing and analysis of segments of Blocks II and III of the RNA polymerase L gene of Rabies virus isolates from different reservoir species of Brazil. The phylogenetic relations of the virus were determined and a variety of species-specific nucleotides were found in the analyzed areas, but the majority of these mutations were found to be synonymous. However, an analysis of the putative amino acid sequences were shown to have some characteristic mutations between some reservoir species of Brazil, indicating that there was positive selection in the RNA polymerase L gene of Rabies virus. On comparing the putative viral sequences obtained from the Brazilian isolates and other Lyssavirus, it was determined that amino acid mutations occurred in low-restriction areas. This study of the L gene of Rabies virus is the first to be conducted with samples of virus isolates from Brazil, and the results obtained will help in the determination of the phylogenetic relations of the virus.

Insectivorous bats are the main reservoirs of rabies virus (RABV) in various regions of the world. The aims of this study were to (a) establish genealogies for RABV strains from different species of Brazilian insectivorous bats based on the nucleoprotein (N) and glycoprotein (G) genes, (b) investigate specific RABV lineages associated with certain genera of bats and (c) identify molecular markers that can distinguish between these lineages. The genealogic analysis of N and G from 57 RABV strains revealed seven genus-specific clusters related to the insectivorous bats Myotis, Eptesicus, Nyctinomops, Molossus, Tadarida, Histiotus and Lasiurus. Molecular markers in the amino acid sequences were identified which were specific to the seven clusters. These results, which constitute a novel finding for this pathogen, show that there are at least seven independent epidemiological rabies cycles maintained by seven genera of insectivorous bats in Brazil., (Copyright 2010 Elsevier Inc. All rights reserved.)

Objective: To identify the species of bats involved in maintaining the rabies cycle; to investigate the distribution of the rabies virus in the tissues and organs of bats and the time taken for mortality among inoculated mice., Methods: From April 2002 to November 2003, bats from municipalities in the State of São Paulo were screened for the presence of the rabies virus, by means of direct immunofluorescence. The virus distribution in the bats was evaluated by inoculating mice and N2A cells with 20% suspensions prepared from fragments of different organs and tissues, plus the brain and salivary glands. The time taken for mortality among the mice was monitored daily, following intracerebral inoculation., Results: Out of the 4,395 bats received, 1.9% were found positive for the rabies virus. They belonged to ten genera, with predominance of insectivores. The maximum mean times taken for mortality among the mice following inoculation with brain and salivary gland material were 15.33+/-2.08 days and 11.33+/-2.30 days for vampire bats, 16.45+/-4.48 days and 18.91+/-6.12 days for insectivorous bats, and 12.60+/-2.13 days and 15.67+/-4.82 days for frugivorous bats, respectively., Conclusions: The species infected with the rabies virus were: Artibeus lituratus, Artibeus sp., Myotis nigricans, Myotis sp., Eptesicus sp., Lasiurus ega, Lasiurus cinereus, Nyctinomops laticaudatus, Tadarida brasiliensis, Histiotus velatus, Molossus rufus, Eumops sp. and Desmodus rotundus. Virus investigation in the different tissues and organs showed that the brain and salivary glands were the most suitable sites for virus isolation.

In this study, we examined various brain suspension concentrations and viral loads in Neuro-2a cell cultures using 20 rabies-positive bovine samples. The reproducibility of results varied: 65% showed consistent outcomes across all concentrations, while 35% disagreed in at least one. Viral titers ranged from less than 25 × 101 to 25 × 103.50 TCID50/mL, with 20% below 25 × 101 TCID50/mL. Concentrations between 5% and 20% yielded over 90% agreement in positive results, but at 30%, agreement dropped from 85% to 50%. Cell confluence was successfully maintained at 5%, 10%, and 20%, while concentrations of 30% and above led to confluence loss. Low viral loads also negatively impacted reproducibility. These results suggest that sample concentration has a direct influence on preservation of cell confluence and that low viral loads may influence the reproducibility of the rabies tissue culture infection test (RTCIT). [ABSTRACT FROM AUTHOR]