Publications by authors named "Samira Achkar"

14 Publications

  • Page 1 of 1

Detection of rabies virus antigen by the indirect rapid immunohistochemistry test in equines and comparisons with other diagnostic techniques.

Zoonoses Public Health 2020 09 14;67(6):651-657. Epub 2020 Jun 14.

Instituto Pasteur, São Paulo, Brazil.

Laboratory diagnosis of rabies in equines is essential for distinguishing the disease from other sources of encephalitis. Diagnosis by conventional techniques such as a direct fluorescent antibody test (dFAT) or viral isolation in mice or cell culture can be difficult, and the application of molecular biological methods may be necessary. We performed an indirect rapid immunohistochemistry test (iRIT) for the detection of the rabies virus (RABV) antigen in the central nervous system (CNS) of equines and compared the results with those of other diagnostic techniques. We reviewed result records from the Rabies Diagnosis Laboratory at Instituto Pasteur, São Paulo, Brazil, of 174 samples of equine CNS from July 2014 to June 2016, which were investigated by dFAT, rabies tissue culture infection test (RTCIT), mouse inoculation test (MIT) and reverse transcription-polymerase chain reaction (RT-PCR) followed by genetic sequencing. These samples, 29 presented divergent results among techniques and were selected for the performed in the iRIT. The detected positivity rate was 4/29 (14%) by dFAT, 5/28 (18%) by RTCIT, 10/29 (35%) by MIT and 26/27 (96%) by RT-PCR. We analysed 29 samples through imprints of the cortex, hippocampus, cerebellum and brainstem in slides fixed in 10% buffered formaldehyde. Eighteen samples were identified as positive (62%) by iRIT assay, representing a greater number of positive cases than that detected by dFAT, MIT and RTCIT but not by RT-PCR. Among the brain regions, the brainstem presented the highest positivity (78%), followed by the hippocampus (69%), cerebellum (67%) and cortex (67%). Our results provide evidence that iRIT can contribute to a rapid diagnosis of rabies in equines and that complementary tests should be used to improve diagnostic accuracy in this species.
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http://dx.doi.org/10.1111/zph.12745DOI Listing
September 2020

Analysis of rabies diagnosis in dogs and cats in the state of São Paulo, Brazil.

Arch Virol 2018 Sep 8;163(9):2369-2376. Epub 2018 May 8.

Pasteur Institute, Av. Paulista 393, São Paulo, SP, CEP 01311-000, Brazil.

The genetic lineage of rabies virus (RABV) associated with dogs has not been found in the state of São Paulo since 1998, and all cases of rabies in domestic animals reported since then have involved the RABV lineage that circulates in bats. As there has been a change in the rabies transmission cycle in cats and dogs, we decided to analyze the tests used to diagnose rabies in these animals in the 15-year period from 2002 to 2016 in the state of São Paulo. During this period, 85,508 central nervous system (CNS) samples from dogs and cats were submitted to the Rabies Diagnosis Section at the Pasteur Institute of São Paulo for testing. All of the samples were tested by the fluorescent antibody test (FAT) and at least one of the following three tests: mouse inoculation test (MIT), rabies tissue culture infection test (RTCIT) and reverse transcription polymerase chain reaction (RT-PCR). Of all the samples tested, twenty were positive in at least one of these assays. Four other positive samples were identified at other institutions in the state of São Paulo. Of the twenty samples that tested positive at the Pasteur Institute of São Paulo, nine were tested by FAT, and the results were subsequently confirmed by other techniques; five gave inconclusive results, and therefore, other techniques had to be used as soon as possible in case the samples were positive; and six were negative by FAT and positive by one or more of the following tests: RTCIT, MIT and RT-PCR. Genetic typing of isolates from eighteen samples identified them as the lineage circulating in bats. In light of this finding, which indicates that genetic lineages associated with bats are circulating in domestic animals in the state of São Paulo, when the results of FAT carried out with samples from aggressive cats and dogs are inconclusive, complementary tests should be used. Decomposing samples and samples for which FAT was inconclusive should be tested using molecular techniques so that a definitive result can be obtained quickly and timely post-exposure prophylaxis can be administered to exposed individuals.
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http://dx.doi.org/10.1007/s00705-018-3829-3DOI Listing
September 2018

A rabies virus vampire bat variant shows increased neuroinvasiveness in mice when compared to a carnivore variant.

Arch Virol 2017 Dec 22;162(12):3671-3679. Epub 2017 Aug 22.

Department of Pathology, School of Veterinary Medicine and Animal Science, University of Sao Paulo, São Paulo, SP, Brazil.

Rabies is one of the most important zoonotic diseases and is caused by several rabies virus (RABV) variants. These variants can exhibit differences in neurovirulence, and few studies have attempted to evaluate the neuroinvasiveness of variants derived from vampire bats and wild carnivores. The aim of this study was to evaluate the neuropathogenesis of infection with two Brazilian RABV street variants (variant 3 and crab-eating fox) in mice. BALB/c mice were inoculated with RABV through the footpad, with the 50% mouse lethal dose (LD) determined by intracranial inoculation. The morbidity of rabies in mice infected with variant 3 and the crab-eating fox strain was 100% and 50%, respectively, with an incubation period of 7 and 6 days post-inoculation (dpi), respectively. The clinical disease in mice was similar with both strains, and it was characterized initially by weight loss, ruffled fur, hunched posture, and hind limb paralysis progressing to quadriplegia and recumbency at 9 to 12 dpi. Histological lesions within the central nervous system (CNS) characterized by nonsuppurative encephalomyelitis with neuronal degeneration and necrosis were observed in mice infected with variant 3 and those infected with the crab-eating fox variant. However, lesions and the presence of RABV antigen, were more widespread within the CNS of variant-3-infected mice, whereas in crab-eating fox-variant-infected mice, RABV antigens were more restricted to caudal areas of the CNS, such as the spinal cord and brainstem. In conclusion, the results shown here demonstrate that the RABV vampire bat strain (variant 3) has a higher potential for neuroinvasiveness than the carnivore variant.
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http://dx.doi.org/10.1007/s00705-017-3530-yDOI Listing
December 2017

Phylogenetic analysis of rabies virus isolated from canids in North and Northeast Brazil.

Arch Virol 2017 Jan 26;162(1):71-77. Epub 2016 Sep 26.

Pasteur Institute, Av. Paulista 393, São Paulo, SP, 01311-000, Brazil.

Cases of canine rabies continue to occur in North and Northeast Brazil, and the number of notifications of rabies cases in wild canids has increased as a result of the expansion of urban areas at the expense of areas with native vegetation. In light of this, we performed molecular characterization of rabies virus isolates from dogs and Cerdocyon thous from various states in North and Northeast Brazil. In all, 102 samples from dogs (n = 56) and Cerdocyon thous (n = 46) collected between 2006 and 2012 were used. The nucleotide sequences obtained for the N gene of rabies virus were analyzed, and phylogenetic analysis revealed the presence of two distinct genetic lineages, one associated with canids and one with bats, and, within the canid cluster, two distinct sublineages circulating among dogs and Cerdocyon thous. In addition, phylogenetic groups associated with geographic region and fourteen cases of interspecific infection were observed among the isolates from canids. Our findings show that analysis of rabies virus lineages isolated from reservoirs such as canids must be constantly evaluated because the mutation rate is high.
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http://dx.doi.org/10.1007/s00705-016-3079-1DOI Listing
January 2017

Monoclonal antibodies for characterization of rabies virus isolated from non-hematophagous bats in Brazil.

J Infect Dev Ctries 2015 Nov 30;9(11):1238-49. Epub 2015 Nov 30.

Instituto Pasteur, São Paulo, SP, Brasil.

Introduction: In Brazil, various isolates of rabies virus (RABV) show antigenic profiles distinct from those established by the reduced panel of eight monoclonal antibodies (MAbs) determined by the Centers for Disease Control and Prevention (CDC), utilized for the antigenic characterization of RABV in the Americas. The objective of this study was to produce MAbs from RABV isolates from insectivorous bats with an antigenic profile incompatible with the pre-established one.

Methodology: An isolate of RABV from the species Eptesicus furinalis that showed an antigenic profile incompatible with the panel utilized was selected. Hybridomas were produced utilizing the popliteal lymph nodes of mice immunized with ribonucleoproteins purified from the isolate.

Results: Two MAbs-producing clones were obtained, BR/IP1-3A7 and BR/IP2-4E10. Fifty-seven isolates of RABV from different species of animals and different regions of Brazil were analyzed utilizing the MAbs obtained. In the analysis of 23 RABV isolates from non-hematophagous bats, the MAbs cross-reacted with ten isolates, of which four were of the species Nyctinomops laticaudatus, one of the species Eptesicus furinalis, and five of the genus Artibeus. Of the nine isolates of non-hematophagous isolates that displayed an incompatible profile analyzed, characteristic of insectivorous bats, BR/IP1-3A7 reacted with five (55.55%) and BR/IP2-4E10 with four (44.44%).

Conclusions: The MAbs obtained were able to recognize epitopes common between the three genera, Artibeus, Eptesicus, and Nyctinomops, thereby allowing the antigenic characterization of RABV isolates in Brazil.
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http://dx.doi.org/10.3855/jidc.6959DOI Listing
November 2015

[Hematophagous bats as reservoirs of rabies].

Rev Peru Med Exp Salud Publica 2014 Apr;31(2):302-9

Instituto Pasteur, São Paulo, Brasil.

Rabies continues to be a challenge for public health authorities and a constraint to the livestock industry in Latin America. Wild and domestic canines and vampire bats are the main transmitter species and reservoirs of the disease. Currently, variations observed in the epidemiological profile of rabies, where the species of hematophagous bat Desmodus rotundus constitutes the main transmitting species. Over the years, knowledge has accumulated about the ecology, biology and behavior of this species and the natural history of rabies, which should lead to continuous development of methods of population control of d. Rotundus as well as prevention and diagnostic tools for rabies. Ecological relationships of this species with other hematophagous and non-hematophagous bats is unknown, and there is much room for improvement in reporting systems and surveillance, as well as creating greater awareness among the farming community. Understanding the impact of human-induced environmental changes on the rabies virus in bats should be cause for further investigation. This will require a combination of field studies with mathematical models and new diagnostic tools. This review aims to present the most relevant issues on the role of hematophagous bats as reservoirs and transmitters of the rabies virus.
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April 2014

Eastern equine encephalitis cases among horses in Brazil between 2005 and 2009.

Arch Virol 2014 Oct 27;159(10):2615-20. Epub 2014 May 27.

Seção de Diagnóstico da Raiva, Instituto Pasteur, Av. Paulista, 393-Cerqueira César, São Paulo, SP, CEP 01311-000, Brazil,

Eastern equine encephalitis is a viral zoonosis that exhibits complex distribution and epidemiology, and greater importance should be given to this disease by the public-health authorities. In Brazil, although eastern equine encephalitis virus (EEEV) has been identified in vectors and antibodies are sometimes detected in horses and humans, there have been no records of equine encephalitis in horses caused by this virus during the last 24 years. This study describes eighteen cases of eastern equine encephalomyelitis that occurred in six Brazilian states between 2005 and 2009. Viral RNA was identified using semi-nested RT-PCR to detect members of the genus Alphavirus, and by genetic sequencing. The gene encoding NSP1 was partially amplified, and after genetic sequencing, eighteen sequences were generated. All eighteen strains were classified as belonging to lineage III of American EEEV. These findings could be an indication of the importance of this virus in animal and human public health.
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http://dx.doi.org/10.1007/s00705-014-2121-4DOI Listing
October 2014

In vitro and in vivo inhibition of rabies virus replication by RNA interference.

Braz J Microbiol 2013 15;44(3):879-82. Epub 2013 Nov 15.

Faculdade de Medicina Veterinária, Universidade de São Paulo, São Paulo, SP, Brazil.

Rabies is a zoonotic disease that affects all mammals and leads to more than 55,000 human deaths every year, caused by rabies virus (RABV) (Mononegavirales: Rhabdoviridae: Lyssavirus). Currently, human rabies treatment is based on the Milwaukee Protocol which consists on the induction of coma and massive antiviral therapy. The aim of this study was to assess the decrease in the titer of rabies virus both in vitro and in vivo using short-interfering RNAs. To this end, three siRNAs were used with antisense strands complementary to rabies virus nucleoprotein (N) mRNA. BHK-21 cells monolayers were infected with 1000 to 0.1 TCID50 of PV and after 2 hours the cells were transfected with each of tree RNAs in separate using Lipofectamine-2000. All three siRNAs reduced the titer of PV strain in a least 0.72 logTCID50/mL and no cytotoxic effect was observed in the monolayers treated with Lipofectamine-2000. Swiss albino mice infected with 10.000 to 1 LD of PV strain by the intracerebral route were also transfected after two hours of infection with a pool 3 siRNAs with Lipofectamine-2000 by the intracerebral route, resulting in a survival rate of 30% in mice inoculated with 100 LD50, while the same dose led to 100% mortality in untreated animals. Lipofectamine-2000 showed no toxic effect in control mice. These results suggest that intracerebral administration of siRNAs might be an effective antiviral strategy for rabies.
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http://dx.doi.org/10.1590/S1517-83822013005000050DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3910205PMC
February 2015

Outbreaks of Eastern equine encephalitis in northeastern Brazil.

J Vet Diagn Invest 2011 May;23(3):570-5

Veterinary Hospital, Federal University of Campina Grande (UFCG), Campus of Patos, 58700-000 Patos, Paraíba, Brazil.

Outbreaks of eastern equine encephalitis observed from May 2008 to August 2009 in the Brazilian states of Pernambuco, Ceará, and Paraíba are reported. The disease occurred in 93 farms affecting 229 equids with a case fatality rate of 72.92%. Main clinical signs were circling, depression or hyperexcitability, ataxia, and progressive paralysis with a clinical manifestation period of 3-15 days. Main histologic lesions were a diffuse lymphocytic encephalomyelitis with neuronal death, satellitosis, neuronophagia, and hemorrhages being more severe in the cerebral gray matter of the telencephalon, diencephalon, and mesencephalon. Some animals also had areas of malacia in the telencephalon, thalamus, and basal nuclei. From 1 case, the virus was isolated by mice inoculation, and in other 13 cases was identified as Eastern equine encephalitis virus by semi-nested reverse transcription polymerase chain reaction. After DNA sequencing, all samples were identified as eastern equine encephalitis through the BLASTn analysis, but samples from the Ceará and Paraíba states corresponded to the same cluster, while the sample from the state of Pernambuco corresponded to a different cluster.
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http://dx.doi.org/10.1177/1040638711403414DOI Listing
May 2011

Rabies virus in insectivorous bats: implications of the diversity of the nucleoprotein and glycoprotein genes for molecular epidemiology.

Virology 2010 Sep 6;405(2):352-60. Epub 2010 Jul 6.

Instituto Pasteur of São Paulo, CEP 01311-000, São Paulo, SP, Brazil.

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.
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http://dx.doi.org/10.1016/j.virol.2010.05.030DOI Listing
September 2010

Genetic characterization of rabies virus isolated from bovines and equines between 2007 and 2008, in the States of São Paulo and Minas Gerais.

Rev Soc Bras Med Trop 2010 Mar-Apr;43(2):116-20

Institute Pasteur, Virology Department, São Paulo, SP, Brazil.

Introduction: Rabies is an acute disease of the central nervous system and is responsible for the deaths of thousands of humans, wild animals and livestock, particularly cattle, as well as causing major economic losses. This study describes the genetic characterization of rabies virus variants that circulate in Desmodus rotundus populations and are transmitted to herbivores.

Methods: Fifty rabies virus isolates from bovines and equines in the States of São Paulo and Minas Gerais, Brazil, were genetically characterized and compared with sequences retrieved from GenBank.

Results: Two clusters (I and II) with mean nucleotide identities of 99.1 and 97.6% were found. The first of these contained nearly all the samples analyzed. Lineages from other Brazilian states grouped in cluster II.

Conclusions: Analysis of the amino acid sequences of the N proteins revealed the existence of genetic markers that may indicate possible variations between geographic regions, although the biologically active regions are conserved within the species over space and time.
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http://dx.doi.org/10.1590/s0037-86822010000200002DOI Listing
August 2010

A coronavirus detected in the vampire bat Desmodus rotundus.

Braz J Infect Dis 2008 Dec;12(6):466-8

Department of Preventive Veterinary Medicine and Animal Health, College of Veterinary Medicine, University of São Paulo, São Paulo, SP, Brazil.

This article reports on the identification of a group 2 coronavirus (BatCoV DR/2007) in a Desmodus rotundus vampire bat in Brazil. Phylogenetic analysis of ORF1b revealed that BatCoV DR/2007 originates from a unique lineage in the archetypical group 2 coronaviruses, as described for bat species elsewhere with putative importance in Public Health.
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http://dx.doi.org/10.1590/s1413-86702008000600003DOI Listing
December 2008

Antigenic and genetic characterization of the first rabies virus isolated from the bat Eumops perotis in Brazil.

Rev Inst Med Trop Sao Paulo 2008 Mar-Apr;50(2):95-9

Pasteur Institute, São Paulo, SP, Brasil.

Although the main transmitters of rabies in Brazil are dogs and vampire bats, the role of other species such as insectivorous and frugivorous bats deserves special attention, as the rabies virus has been isolated from 36 bat species. This study describes the first isolation of the rabies virus from the insectivorous bat Eumops perotis. The infected animal was found in the city of Ribeirão Preto, São Paulo. The virus was identified by immunofluorescence antibody test (FAT) in central nervous system (CNS) samples, and the isolation was carried out in N2A cell culture and adult mice. The sample was submitted to antigenic typing using a panel of monoclonal antibodies (CDC/Atlanta/USA). The DNA sequence of the nucleoprotein gene located between nucleotides 102 and 1385 was aligned with homologous sequences from GenBank using the CLUSTAL/W method, and the alignment was used to build a neighbor-joining distance-based phylogenetic tree with the K-2-P model. CNS was negative by FAT, and only one mouse died after inoculation with a suspension from the bat's CNS. Antigenic typing gave a result that was not compatible with the patterns defined by the panel. Phylogenetic analysis showed that the virus isolated segregated into the same cluster related to other viruses isolated from insectivorous bats belonging to genus Nyctinomops ssp. (98.8% nucleotide identity with each other).
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http://dx.doi.org/10.1590/s0036-46652008000200006DOI Listing
August 2008

First report of rabies in vampire bats (Desmodus rotundus) in an urban area, Ubatuba, São Paulo state, Brazil.

Rev Inst Med Trop Sao Paulo 2007 Nov-Dec;49(6):389-90

Ubatuba Zoonosis Control Center, São Paulo, Brazil.

The purpose of this report is to record the first case of a hematophagous bat (Desmodus rotundus) infected with rabies virus in an urban area in Brazil. To the authors' knowledge, this is the first such case in Latin America. After discovering a bat in his garden at 10 o'clock in the morning, a resident of Ubatuba municipality asked the Zoonosis Control Center team to visit his home. The animal was caught alive on the same day and sent to the Pasteur Institute laboratory, where it was identified as a Desmodus rotundus specimen. Standard tests for rabies diagnosis were carried out (direct immunofluorescence and viral isolation), and the results were positive. The presence of different species of (primarily insectivorous) bats in urban areas represents a serious public health problem. This case, however, is indicative of a much greater risk because the species in question has hematophagous habits, what means this animals has a low energy reserves and, therefore, its need to feed daily.
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http://dx.doi.org/10.1590/s0036-46652007000600010DOI Listing
June 2008