Ante mortem diagnosis of human rabies using saliva samples: comparison of real time and conventional RT-PCR techniques

Ante-mortem and Post-mortem Diagnosis Modalities and Phylogenetic Analysis of Rabies Virus in Domestic and Wild Animals of Gujarat, India

In the present study, total of 32 ante-mortem (AM) samples (saliva = 18 and corneal smears = 14) from six animal species (cattle = 5; camel = 1; goat = 1; horse = 1; buffalo = 4; dog = 6) and 28 post-mortem (PM) samples of domestic (cattle = 6; camel = 1; goat = 1; buffalo = 5; dog = 7) and wild animals (lion = 4, mongoose = 2; bear = 1; leopard = 1) were examined for rabies diagnosis in Gujarat, India. Direct fluorescent antibody test (dFAT) and reverse transcriptase polymerase chain reaction (RT-PCR) were applied on AM samples, whereas along with dFAT and RT-PCR, histopathological examination, immunohistochemistry (IHC) and real time PCR (qPCR) were used for PM diagnosis. Nucleotide sequencing of full nucleoprotein (N) and glycoprotein (G) genes were carried out upon representative amplicons. In AM examination, 7/18 saliva and 5/14 corneal impressions samples were found positive in dFAT and 8/18 saliva samples were found positive in RT-PCR. In PM examination, 14/28 samples showed positive results in dFAT and IHC with unusual large fluorescent foci in two samples. In histopathology, 11/28 samples showed appreciable lesion and Negri bodies were visible in 6 samples, only. Out of 23 brain samples examined. 12 samples were found positive in N gene RT-PCR and qPCR, and 10 samples in G gene RT-PCR. Phylogenetic analysis of N gene revealed that test isolates (except sample ID: lion-1; lion, Gir) form a close group with sequence ID, KM099393.1 (Mongoose, Hyderabad) and KF660246.1 (Water Buffalo, Hyderabad) which was far from some south Indian and Sri Lankan isolates but similar to Indian isolates from rest of India and neighboring countries. In G gene analysis, the test isolates form a close group with sequence ID, KP019943.1.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-023-01126-0.

Large-scale phylogenetic analysis reveals genetic diversity and geographic distribution of rabies virus in South-East and South Asia

South-East Asia (SEA) and South Asia (SA) are two important geographic regions with the most severe enzootic rabies in the world. In these regions, phylogenetic analysis of rabies virus (RABV) has been conducted only at a country level; the results obtained from different countries are scattered and unequal, with a non-uniform system to name RABV genotypes. Therefore, it is difficult to undertake origin-tracking and compare inter-country RABV evolution and transmission. To avoid the confusion in understanding and to generate a panoramic picture of RABV genetic diversity, distribution, and transmission in SEA and SA, the present study conducted a systematic phylogenetic analysis by combining all sequences representing 2368 RABV strains submitted to GenBank by 14 rabies endemic SEA and SA countries. The results showed that RABVs circulating in two regions were classified into four major clades and many subclades: the Asia clade is circulating only in SEA, the Indian subcontinent, and Arctic-like clades only in SA, while the Cosmopolitan clade has been detected in both regions. The results also showed a wide range of hosts were infected by divergent RABV subclades, with dogs being the major transmission source. However, wildlife rabies was also found to be an important issue with 6 wild carnivore species identified as potential sources of spillover risk for sylvatic rabies to humans, domestic animals, and other wild animals. Current findings indicate that the two regions have separate virus clades circulating thus indicating the absence of cross-transmission between the regions. The study emphasizes the importance of phylogenetic analysis in the regions using uniform genotyping and naming systems for rabies surveillance, to coordinate actions of member countries to eliminate dog-mediated human rabies by 2030.

Micro/nano biomedical devices for point-of-care diagnosis of infectious respiratory diseases

Corona Virus Disease 2019 (COVID-19) has developed into a global pandemic in the last two years, causing significant impacts on our daily life in many countries. Rapid and accurate detection of COVID-19 is of great importance to both treatments and pandemic management. Till now, a variety of point-of-care testing (POCT) approaches devices, including nucleic acid-based test and immunological detection, have been developed and some of them has been rapidly ruled out for clinical diagnosis of COVID-19 due to the requirement of mass testing. In this review, we provide a summary and commentary on the methods and biomedical devices innovated or renovated for the quick and early diagnosis of COVID-19. In particular, some of micro and nano devices with miniaturized structures, showing outstanding analytical performances such as ultra-sensitivity, rapidness, accuracy and low cost, are discussed in this paper. We also provide our insights on the further implementation of biomedical devices using advanced micro and nano technologies to meet the demand of point-of-care diagnosis and home testing to facilitate pandemic management. In general, our paper provides a comprehensive overview of the latest advances on the POCT device for diagnosis of COVID-19, which may provide insightful knowledge for researcher to further develop novel diagnostic technologies for rapid and on-site detection of pathogens including SARS-CoV-2.

Roles of apoptosis and autophagy in natural rabies infections

The aim of this study was to investigate the activity of apoptosis and autophagy in animals (cows, horses, donkeys, dogs and cats) naturally infected with rabies by using immunohistochemistry, immunofluorescence, and qPCR. The mRNA transcript levels of caspase-3, Bax, Bcl2 and LC3B were determined with qPCR. Caspase-3 and AIF immunopositivity were not observed in the immunohistochemical and immunofluorescence staining, whereas LC3B immunopositivity was determined intensively in the infected animals compared to the control groups. LC3B immunopositivity was detected in the cytoplasm of the Purkinje cells in the cerebellum of the cows, horses and donkeys, and also in the cytoplasm of the neurons in the cornu ammonis of the dogs and cats. While the expression levels of caspase-3 and Bax were downregulated, the Bcl2 expression was up-regulated in the infected animals compared to the uninfected animals. In addition, the LC3B levels were found to be significantly higher in the infected animals. To the best of our knowledge, this work represents the first report of neuronal death in the central nervous system by autophagy, rather than by caspase-dependent or AIF-containing caspase-independent apoptosis.

Evolutionary analysis of rabies virus using the partial Nucleoprotein and Glycoprotein gene in Mumbai region of India

Nearly 1.7 million cases of dog bites are reported every year in India and many cases of animal rabies are left unattended and undiagnosed. Therefore, a mere diagnosis of rabies is not sufficient to understand the epidemiology and the spread of the rabies virus (RV) in animals. There is a paucity of information about the evolutionary dynamics of RV in dogs and its biodiversity patterns in India. In total, 50 dog-brain samples suspected of rabies were screened by the nucleoprotein- (N) and glycoprotein- (G) gene PCR. The N and G genes were subsequently sequenced to understand the molecular evolution in these genes. The phylogenetic analysis of the N gene revealed that six isolates in the Mumbai region belonged to a single Arctic lineage. Time-scaled phylogeny by Bayesian coalescent analysis of the partial N gene revealed that the time to the most recent common ancestor (TMRCA) for the sequences belonged to the cluster from 2006.68 with a highest posterior density of 95 % betweeen 2005-2008, which is assigned to Indian lineage I. Migration pattern revealed a strong Bayes factor between Mumbai to Delhi, Panji to Hyderabad, Delhi to Chennai, and Chennai to Chandigarh. Phylogenetic analysis of the G gene revealed that the RVs circulating in the Mumbai region are divided into three lineages. Time-scaled phylogeny by the Bayesian coalescent analysis method estimated that the TMRCA for sequences under study was from 1993 and Indian clusters was from 1962. In conclusion, the phylogenetic analysis of the N gene revealed that six isolates belonged to single Arctic lineages along with other Indian isolates and they were clustered into a single lineage but divided into three clades based on the G-gene sequences. The present study highlights and enhances the current molecular epidemiology and evolution of RV and revealed strong location bias and geographical clustering within Indian isolates on the basis of N and G genes.

[Сases of human convalescence from rabies and lifetime diagnostics of lyssavirus encephalitis.]

Notwithstanding the availability of effective vaccines, 40 - 60 thousand rabies cases in humans are reported every year. Almost always the disease is fatal because therapeutic treatment of lyssavirus encephalitis has not been developed. Since 1970 the number of reports on rare cases of convalescence including those using experimental treatment protocols has been gradually increasing 20 cases of convalescence, "partial" convalescence or long-term survival of humans (1970-2015) were selected as they were complaint with laboratory criteria of active lyssavirus infection. Children and teenagers were predominant in the analyzed group (85%). The cases were irregularly spread between the continents: Asia - 6 cases, North America - 6 cases, Africa - 2 cases and Europe - 1 case. India and the USA were on the top of the list of countries by the number of described cases. More than 60% humans were infected from dogs, three cases got infection from bats and 2 cases were allegedly associated with an unknown lyssavirus and an unidentified infection source. 70% cases were vaccinated and 10% cases were treated with gamma globulin before the disease onset. Serological tests for detection of antibodies to lyssaviruses in cerebrospinal fluid of infected humans were typically used for diagnostic laboratory verification. Less than 30% IFA and PCR positives were obtained. Lyssaviruses were never detected. Only 4 convalescent patients were treated using experimental protocols. 80% cases demonstrated severe neurological consequences, four (may be more) patients died afterwards within the period from two months to four years. Different perspectives on prospects of Milwaukee protocol use and other therapeutic techniques are given.

Multi-site evaluation of the LN34 pan-lyssavirus real-time RT-PCR assay for post-mortem rabies diagnostics

Rabies is a fatal zoonotic disease that requires fast, accurate diagnosis to prevent disease in an exposed individual. The current gold standard for post-mortem diagnosis of human and animal rabies is the direct fluorescent antibody (DFA) test. While the DFA test has proven sensitive and reliable, it requires high quality antibody conjugates, a skilled technician, a fluorescence microscope and diagnostic specimen of sufficient quality. The LN34 pan-lyssavirus real-time RT-PCR assay represents a strong candidate for rabies post-mortem diagnostics due to its ability to detect RNA across the diverse Lyssavirus genus, its high sensitivity, its potential for use with deteriorated tissues, and its simple, easy to implement design. Here, we present data from a multi-site evaluation of the LN34 assay in 14 laboratories. A total of 2,978 samples (1,049 DFA positive) from Africa, the Americas, Asia, Europe, and the Middle East were tested. The LN34 assay exhibited low variability in repeatability and reproducibility studies and was capable of detecting viral RNA in fresh, frozen, archived, deteriorated and formalin-fixed brain tissue. The LN34 assay displayed high diagnostic specificity (99.68%) and sensitivity (99.90%) when compared to the DFA test, and no DFA positive samples were negative by the LN34 assay. The LN34 assay produced definitive findings for 80 samples that were inconclusive or untestable by DFA; 29 were positive. Five samples were inconclusive by the LN34 assay, and only one sample was inconclusive by both tests. Furthermore, use of the LN34 assay led to the identification of one false negative and 11 false positive DFA results. Together, these results demonstrate the reliability and robustness of the LN34 assay and support a role for the LN34 assay in improving rabies diagnostics and surveillance.

Saliva and viral infections

Over the last 10 years there have been only a handful of publications dealing with the oral virome, which is in contrast to the oral microbiome, an area that has seen considerable interest. Here, we survey viral infections in general and then focus on those viruses that are found in and/or are transmitted via the oral cavity; norovirus, rabies, human papillomavirus, Epstein‐Barr virus, herpes simplex viruses, hepatitis C virus, and HIV. Increasingly, viral infections have been diagnosed using an oral sample (e.g. saliva mucosal transudate or an oral swab) instead of blood or urine. The results of two studies using a rapid and semi‐quantitative lateral flow assay format demonstrating the correlation of HIV anti‐IgG/sIgA detection with saliva and serum samples are presented. When immediate detection of infection is important, point‐of‐care devices that obtain a non‐invasive sample from the oral cavity can be used to provide a first line diagnosis to assist in determining appropriate counselling and therapeutic path for an increasing number of diseases.

Diagnostic difficulties in human rabies: A case report and review of the literature

Rabies is a zoonotic disease with the highest fatality rate of any infectious disease. The clinical features of rabies encephalopathy are highly nonspecific at the onset and clinicians from low endemic areas usually face difficulties in recognizing cases during the early stages. The need for establishing a rapid and accurate test to identify rabies during the ante-mortem period is important. However, in actual clinical practice, the latter may remain difficult for various reasons. In human rabies, positively identifying the antigen, antibody or genetic material by various diagnostic methods during the symptomatic period is affected by the unpredictable nature of viremia, levels of antibody immune response of the host, and the virulence of the infecting strain. Also, more advanced testing with greater sensitivity may not be readily available at all centers. Here we describe a case of a young male who was bitten by a rabid dog and developed progressive encephalopathy with a fatal outcome, with negative antibodies in the cerebrospinal fluid (CSF). A review of the literature on the clinical features, diagnostic tests, treatment and prevention of rabies is also presented.

Molecular characterization of nucleoprotein gene of rabies virus from Maharashtra, India

Context:

Rabies poses a serious public health concern in developing countries such as India. Aims: The study focuses on molecular diagnosis of street rabies virus (RABV) from human clinical specimens received from Maharashtra, India.

Materials and Methods:

Nucleoprotein gene from eight (of total 20 suspected samples) rabies cases that tested positive for rabies antigen using reverse transcriptase-polymerase chain reaction (RT-PCR) were sequenced.

Results:

Sequence analysis using basic local alignment search tool (BLAST) and multiple sequence alignment (MSA) and phylogenetic analysis showed similarity to previously reported sequences from India and those of Arctic lineages.

Conclusions:

The circulating RABV strains in Maharashtra, India show genetic relatedness to RABV strains reported from Indo-Arctic lineages and India-South and Japan.

Evaluation of In vitro Antiviral Activity of Datura metel Linn. Against Rabies Virus

Objective:

The soxhlet and cold extracts of Datura metel Linn. were evaluated for in vitro antirabies activity.

Materials and Methods:

Soxhlet and cold extraction method were used to extract Datura (fruit and seed) extracts. In vitro cytotoxicity assay was performed by 3-(4,5-dimethylthiazolyl-2)-2,5-diphenyltetrazolium bromide assay. Based on the CC50 range, the in vitro antirabies activity of the extracts was screened by rapid fluorescent focus inhibition test and molecular method.

Results:

The Datura (fruit and seed) extracts were not cytotoxic below 5 mg/ml (CC50). Titer of 10⁻⁴ rabies virus challenge virus standard (RV CVS) (1 50% tissue culture infective dose [1 TCID50]) was obtained by RFFT method and the challenge dose of 10 TCID50 was used for antirabies assay. Datura fruit and seed (soxhlet and cold) extracts showed 50% inhibition of RV CVS at 2.5 mg/ml and 1.25 mg/ml (inhibitory concentration 50% [IC50]), respectively. The tested extracts showed selectivity index (CC50/IC50) ranging from 2 to 4. The viral RNA was extracted and real-time reverse transcription-polymerase chain reaction was performed which also revealed a 2-fold reduction of viral load at 1.25 mg/ml of the Datura seed (soxhlet methanolic and cold aqueous) extracts.

Conclusion:

To the best of our knowledge, this is the first study of in vitro antiviral activity of D. metel Linn. against rabies virus. Datura seed extracts have a potential in vitro antirabies activity and, in future, can be further screened for in vivo activity against rabies virus in murine model.

SUMMARY

In the present study, Datura metel. Linn showed and in-vitro anti rabies activity in Vero cell line which was determined by RFFIT method and PCR method

Instructive even after a decade: Complete results of initial virological diagnostics and re-evaluation of molecular data in the German rabies virus "outbreak" caused by transplantations

In 2005, six patients in Germany received solid organs and both corneas from a donor with an unrecognized rabies infection. Initial virological diagnostics with the machinery available at the two national reference laboratories could quickly clarify the situation. Rabies virus antigen was detected in the organ donor's brain. In two of the three recipients with neurological alterations, intra vitam diagnosis was achieved by conventional RT-PCRs. Comparison of the phylogenetic relatedness of the different viral isolates proved transmission from the donor and, consequently, also established the diagnosis for the third patient. As indicated by the titre of neutralizing antibodies, the liver transplant recipient was protected from the lethal infection due to a vaccination against rabies virus, which he had received more than 15 years ago. All samples from the recipients of the corneas were invariably negative. Re-evaluation of the molecular data by real-time PCR did not lead to an improvement of intra vitam diagnosis but provided intriguing insights regarding the relative amounts of rabies virus RNA in different body fluids and peripheral organs. In saliva and skin, they were 250-200,000 times lower than in the infected patient's brains. Furthermore, in saliva samples taken serially from the same patient fluctuations by a factor of 160-500 were recorded. These findings highlight the problems of intra vitam diagnosis of rabies virus infections and make understandable why the virus can escape from all diagnostic attempts. Finally, in this context one should recall an almost trivial fact: Simple and appropriate postexposure prophylaxis could not only have saved the young organ donor's life but would also have prevented the whole transplantation-associated rabies "outbreak" in Germany.

Exogenous interferon prolongs survival of rabies infected mice

Rabies is an acute viral infection that causes encephalomyelitis in almost all warm blooded animals and is invariably fatal once the clinical signs appear. The present study was carried out to assess the effect of recombinant human interferon alpha (rhIFN α-2A) treatment on the survival of rabies infected mice and its correlation with cytokines expression. The gene expression of TNF-α and IL-6 was measured by SYBR Green Real Time PCR for two groups-"Pre-exposure" (mice were inoculated with rhIFN α-2A prior to rabies infection) and "Post-exposure" (mice were inoculated with rhIFN α-2A post rabies virus infection). Delayed mortality was observed in interferon treated infected groups. In addition, statistically significant decrease (P < 0.0001) in the expression of TNF-α and IL-6 was observed, both in the pre-exposure and post-exposure groups. These findings indicate that modulation of cytokine secretion using exogenous biologicals such as rhIFN may offer novel therapeutic approaches to treat diseases such as rabies.

Cross-platform evaluation of commercial real-time SYBR green RT-PCR kits for sensitive and rapid detection of European bat Lyssavirus type 1

This study evaluates the performance of five two-step SYBR Green RT-qPCR kits and five one-step SYBR Green qRT-PCR kits using real-time PCR assays. Two real-time thermocyclers showing different throughput capacities were used. The analysed performance evaluation criteria included the generation of standard curve, reaction efficiency, analytical sensitivity, intra- and interassay repeatability as well as the costs and the practicability of kits, and thermocycling times. We found that the optimised one-step PCR assays had a higher detection sensitivity than the optimised two-step assays regardless of the machine used, while no difference was detected in reaction efficiency, R (2) values, and intra- and interreproducibility between the two methods. The limit of detection at the 95% confidence level varied between 15 to 981 copies/µL and 41 to 171 for one-step kits and two-step kits, respectively. Of the ten kits tested, the most efficient kit was the Quantitect SYBR Green qRT-PCR with a limit of detection at 95% of confidence of 20 and 22 copies/µL on the thermocyclers Rotor gene Q MDx and MX3005P, respectively. The study demonstrated the pivotal influence of the thermocycler on PCR performance for the detection of rabies RNA, as well as that of the master mixes.

Characterisation and quantification of F8 transcripts of ten putative splice site mutations

Mutations affecting splice sites comprise approximately 7.5 % of the known F8 gene mutations but only a few were verified at mRNA level. In the present study, 10 putative splice site mutations were characterised by mRNA analysis using reverse transcription PCR (RT-PCR). Quantitative real-time RT-PCR (RT-qPCR) and co-amplification fluorescent PCR were used in combination to quantify the amount of each of multiple F8 transcripts. All of the mutations resulted in aberrant splicing. One of them (c.6187+1del1) generated one form of F8 transcript with exon skipping, and the remaining nine mutations (c.602-6T>C, c.1752+5_1752+6insGTTAG, c.1903+5G>A, c.5219+3A>G, c.5586+3A>T, c.969A>T, c.265+4A>G, c.601+1_601+5del5 and c.1444-8_1444del9) produced multiple F8 transcripts with exon skipping, activation of cryptic splice site and/or normal splicing. Residual wild-type F8 transcripts were produced by the first six of the nine mutations with amounts of 3.9 %, 14.2 %, 5.2 %, 19.2 %, 1.8 % and 2.5 % of normal levels, respectively, which were basically consistent with coagulation phenotypes in the related patients. In comparison with the mRNA findings, software Alamut v2.3 had values in the prediction of pathogenic effects on native splice sites but was not reliable in the prediction of activation of cryptic splice sites. Our quantification of F8 transcripts may provide an alternative way to evaluate the low expression levels of residue wild-type F8 transcripts and help to explain the severity of haemophilia A caused by splicing site mutations.

Real-Time RT-PCR for the Detection of Lyssavirus Species

The causative agents of rabies are single-stranded, negative-sense RNA viruses in the genus Lyssavirus of Rhabdoviridae, consisting of twelve classified and three as yet unclassified species including classical rabies virus (RABV). Highly neurotropic RABV causes rapidly progressive encephalomyelitis with nearly invariable fatal outcome. Rapid and reliable diagnosis of rabies is highly relevant for public and veterinary health. Due to growing variety of the genus Lyssavirus observed, the development of suitable molecular assays for diagnosis and differentiation is challenging. This work focused on the establishment of a suitable real-time RT-PCR technique for rabies diagnosis as a complement to fluorescent antibody test and rabies tissue culture infection test as gold standard for diagnosis and confirmation. The real-time RT-PCR was adapted with the goal to detect the whole spectrum of lyssavirus species, for nine of which synthesized DNA fragments were used. For the detection of species, seven probes were developed. Serial dilutions of the rabies virus strain CVS-11 showed a 100-fold higher sensitivity of real-time PCR compared to heminested RT-PCR. Using a panel of thirty-one lyssaviruses representing four species, the suitability of the protocol could be shown. Phylogenetic analysis of the sequences obtained by heminested PCR allowed correct classification of all viruses used.

Laboratory diagnosis of human rabies: recent advances

Rabies, an acute progressive, fatal encephalomyelitis, transmitted most commonly through the bite of a rabid animal, is responsible for an estimated 61,000 human deaths worldwide. The true disease burden and public health impact due to rabies remain underestimated due to lack of sensitive laboratory diagnostic methods. Rapid diagnosis of rabies can help initiate prompt infection control and public health measures, obviate the need for unnecessary treatment/medical tests, and assist in timely administration of pre- or postexposure prophylactic vaccination to family members and medical staff. Antemortem diagnosis of human rabies provides an impetus for clinicians to attempt experimental therapeutic approaches in some patients, especially after the reported survival of a few cases of human rabies. Traditional methods for antemortem and postmortem rabies diagnosis have several limitations. Recent advances in technology have led to the improvement or development of several diagnostic assays which include methods for rabies viral antigen and antibody detection and assays for viral nucleic acid detection and identification of specific biomarkers. These assays which complement traditional methods have the potential to revolutionize rabies diagnosis in future.

Utility of real-time Taqman PCR for antemortem and postmortem diagnosis of human rabies

Rabies, a fatal zoonotic viral encephalitis remains a neglected disease in India despite a high disease burden. Laboratory confirmation is essential, especially in patients with paralytic rabies who pose a diagnostic dilemma. However, conventional tests for diagnosis of rabies have several limitations. In the present study the utility of a real-time TaqMan PCR assay was evaluated for antemortem/postmortem diagnosis of rabies. Human clinical samples received for antemortem rabies diagnosis (CSF, saliva, nuchal skin biopsy, serum), and samples obtained postmortem from laboratory confirmed rabies in humans (brain tissue, CSF, serum) and animals (brain tissue) were included in the study. All CSF and sera were tested for rabies viral neutralizing antibodies (RVNA) by rapid fluorescent focus inhibition test (RFFIT) and all samples (except sera) were processed for detection of rabies viral RNA by real-time TaqMan PCR. All the 29 (100%) brain tissues from confirmed cases of human and animal rabies, and 11/14 (78.5%) CSF samples obtained postmortem from confirmed human rabies cases were positive by real-time TaqMan PCR. Rabies viral RNA was detected in 5/11 (45.4%) CSF samples, 6/10 (60%) nuchal skin biopsies, and 6/7 (85.7%) saliva samples received for antemortem diagnosis. Real-time TaqMan PCR alone could achieve antemortem rabies diagnosis in 11/13 (84.6%) cases; combined with RVNA detection in CSF antemortem rabies diagnosis could be achieved in all 13 (100%) cases. Real-time TaqMan PCR should be made available widely as an adjunctive test for diagnosis of human rabies in high disease burden countries like India.

A step forward in molecular diagnostics of lyssaviruses--results of a ring trial among European laboratories

Rabies is a lethal and notifiable zoonotic disease for which diagnostics have to meet the highest standards. In recent years, an evolution was especially seen in molecular diagnostics with a wide variety of different detection methods published. Therefore, a first international ring trial specifically designed on the use of reverse transcription polymerase chain reaction (RT-PCR) for detection of lyssavirus genomic RNA was organized. The trial focussed on assessment and comparison of the performance of conventional and real-time assays. In total, 16 European laboratories participated. All participants were asked to investigate a panel of defined lyssavirus RNAs, consisting of Rabies virus (RABV) and European bat lyssavirus 1 and 2 (EBLV-1 and -2) RNA samples, with systems available in their laboratory.

The ring trial allowed the important conclusion that conventional RT-PCR assays were really robust assays tested with a high concordance between different laboratories and assays. The real-time RT-PCR system by Wakeley et al. (2005) in combination with an intercalating dye, and the combined version by Hoffmann and co-workers (2010) showed good sensitivity for the detection of all RABV samples included in this test panel. Furthermore, all used EBLV-specific assays, real-time RT-PCRs as well as conventional RT-PCR systems, were shown to be suitable for a reliable detection of EBLVs. It has to be mentioned that differences were seen in the performance between both the individual RT-PCR systems and the laboratories. Laboratories which used more than one molecular assay for testing the sample panel always concluded a correct sample result.

Due to the markedly high genetic diversity of lyssaviruses, the application of different assays in diagnostics is needed to achieve a maximum of diagnostic accuracy. To improve the knowledge about the diagnostic performance proficiency testing at an international level is recommended before using lyssavirus molecular diagnostics e.g. for confirmatory testing.

Detection of rabies viral RNA by TaqMan real-time RT-PCR using non-neural specimens from dogs infected with rabies virus

To determine the burden of rabies in developing countries, a reliable and accurate diagnostic test for the examination of the brains of animals is needed. Recently, the number of samples and carcasses submitted to rabies diagnostic units has been declining. Methods for obtaining tissues from different regions of the brain are even more difficult, and direct florescent antibody examination may fail if the samples decomposed. The spread of rabies virus to peripheral non-nervous tissues starts early during the pre-clinical phase. It has been shown that saliva and skin biopsies taken at the neck and containing hair follicles can be used in the ante-mortem diagnosis of rabies in humans. Obtaining oral swab samples, whisker or hair follicles from the heads of canines is easy and practical and can be performed without special equipment. The objective of this study was to determine whether these non-neural specimens can be used for the detection of rabies viral RNA. The RNAs extracted from these specimens were tested using a real-time reverse transcriptase polymerase chain reaction (RT-PCR). The sensitivity of the TaqMan real-time RT-PCR analysis using samples from dogs confirmed to be infected with rabies virus was 84.6% (55/65), 81.8% (54/66) and 66.7% (44/66) when using oral swab samples, extracted whisker follicles and extracted hair follicles; the specificity of all specimen types was 100%. The negative predictive values were 77.8%, 74.4% and 61.4%, respectively. Although the rate of positivity when combining the three non-neural specimen types was increased to 86.4%, this level of sensitivity was not sufficient to help physicians whether to administer post exposure prophylaxis. However, these oral swab and whisker specimens may serve to enhance epidemiological surveillance; such data will contribute in the planning of rabies control programs.

Susceptibility and lack of evidence for a viremic state of rabies in the night owl monkey, Aotus nancymaae

BACKGROUND

Rabies causes an acute fatal encephalomyelitis in most mammals following infection with rhabdovirus of the genus Lyssavirus. Little is known about rabies virus infection in species of New World non-human Primates (NHP). To investigate the suitability of the owl monkey Aotus nancymaae asissue sections examined were unremarkable for inflammation or other histologic signs of rabies a viable animal model for rabies virus candidate vaccine testing, we used clinical presentation, serology, viral isolation, and PCR to evaluate the incubation period, immunity, and pathogenesis of infected animals. We tested the hypothesis that no viremic state exists for rabies virus.

METHODS

Eight monkeys divided into two equal groups were inoculated intramuscularly either in the neck or footpad with 105 pfu of rabies virus (Pasteur/V-13R) and observed for >130 days. Oral and blood samples were collected and analyzed.

RESULTS

Two monkeys inoculated in the neck displayed classic paralytic rabies. The mean incubation period was 11.5 days. The average maximum IgG response (antibody titer >0.200 O.D.) was achieved at day 10.0 and 62.3 in the clinical rabies and non-clinical rabies cases, respectively (p = 0.0429). No difference in IgM or IgG time to seroconversion or average maximum IgM level was observed between neck versus footpad inoculation groups. No viremia or viral shedding was detected by PCR or viral isolation during the observation period, including within the two symptomatic animals three days after disease onset. Tissue sections examined were unremarkable for inflammation or other histologic signs of rabies within the asymptomatic animal. Similarly none of the brain sections exhibited immunoreactivity for rabies virus antibody.

DISCUSSION

This study demonstrates there is no difference in time to immune response between inoculation sites and distance to the brain; however, immune response tends to be more rapid in cases of clinically apparent disease and prolonged in cases infected at sites further from the brain.

CONCLUSIONS

Our findings support the hypothesis that a viremic state for rabies does not exist in the New World Monkey, Aotus nancymaae, and it appears that this species may be refractory to infection. The species does provide a suitable model to assess post infection immune responses. Additional studies that address the limitations of sample size, length of observation, and lack of measurable infection should be conducted.

Pathology of tropical diseases

Tropical diseases affecting the central nervous system include infections, infestations, and nutritional deficiency disorders. This article discusses the commonly encountered diseases. The infections include bacterial, mycobacterial, fungal, parasitic, and viral infections with varied clinical manifestations. Imaging sensitivity and specificity for the prediction of the cause of infections has improved with application of advanced techniques. Microbial demonstration and histology remain the gold standard for diagnosis. Understanding the basis of imaging changes is mandatory for better evaluation of images. Nutritional disorders present with generalized and nonspecific imaging manifestations. The pathology of commonly encountered vitamin deficiencies is also discussed.

Evaluation of a rapid immunochromatographic test strip for detection of Rabies virus in dog saliva samples

An immunochromatographic test strip for Rabies virus was evaluated with dog saliva samples. The test was initially validated against 237 dogs of known infection status, and then evaluated in the field with 1,290 live dogs. By validation of paired saliva-brain specimens obtained from dogs at necropsy, the saliva strip test was 94.4% specific and 93.0% sensitive when compared to the gold standard fluorescent antibody test (FAT) on brain smears. The sensitivity and specificity of a nested polymerase chain reaction (nPCR) assay using saliva were 100% compared to the FAT results. The performance of strip test with field saliva samples from street dogs had a specificity of 98.7% in comparison to nPCR as the reference method. As the strip test kit can potentially be used outside the laboratory and be applicable as an on-site testing assay, it represents a powerful screening tool for epidemiological surveys and disease control. The test could be useful for the surveillance of rabies in dogs and, in particular, be used to monitor the success of rabies control programs.

Risco de transmissão do vírus da raiva oriundo de sagui (Callithrix jacchus), domiciliado e semidomiciliado, para o homem na região metropolitana de Fortaleza, estado do Ceará

INTRODUÇÃO: Uma variante do vírus da raivafoi identificadaem associação a casos de raiva humanos, no Estado do Ceará, transmitidos por saguis (Callithrix jacchus), primatas frequentemente criados como animais de estimação. Essa variante não apresenta proximidade antigênica ou relação genética com as variantes do vírus encontradas em morcegos e mamíferos terrestres das Américas. O objetivo do estudo foi avaliar os fatores de risco de transmissão do vírus da raiva oriundo de sagui (C. jacchus), criado como animal de estimação, para o homem na região metropolitana de Fortaleza, Ceará. MÉTODOS: Foi aplicado um questionário estruturado aos criadores de saguis, residentes nos municípios de Aquiraz e Maranguape, Ceará, enfocando o manejo e a interação desses primatas com humanos. Para avaliação da ocorrência de antígenos rábicos, através do teste de imunofluorescência direta (IFD), foram coletadas amostras de saliva dos saguis domiciliados e semidomiciliados. Com base nos resultados obtidos desses espécimes, foram analisadas amostras de sistema nervoso central (SNC). RESULTADOS: Na análise dos questionários, observou-se a proximidade dos criadores de saguis durante o manejo desses animais nos domicílios, bem como, seus conhecimentos limitados sobre a raiva, demonstrando haver risco quanto à transmissão do vírus. De 29 amostras de saliva de saguis reavaliadas, uma (3,4%) apresentou reação de IFD positiva. De 11 amostras de SNC, três (27,3%) apresentaram positividade. CONCLUSÕES: Os dados laboratoriais estão de acordo com os achados dos questionários, confirmando haver risco da transmissão do vírus da raiva devido à convivência de humanos com saguis (C. jacchus).

Improved safety for molecular diagnosis of classical rabies viruses by use of a TaqMan real-time reverse transcription-PCR "double check" strategy

To improve the diagnosis of classical rabies virus with molecular methods, a validated, ready-to-use, real-time reverse transcription-PCR (RT-PCR) assay was developed. In a first step, primers and 6-carboxyfluorescien-labeled TaqMan probes specific for rabies virus were selected from the consensus sequence of the nucleoprotein gene of 203 different rabies virus sequences derived from GenBank. The selected primer-probe combination was highly specific and sensitive. During validation using a sample set of rabies virus strains from the virus archives of the Friedrich-Loeffler-Institut (FLI; Germany), the Veterinary Laboratories Agency (VLA; United Kingdom), and the DTU National Veterinary Institute (Lindholm, Denmark), covering the global diversity of rabies virus lineages, it was shown that both the newly developed assay and a previously described one had some detection failures. This was overcome by a combined assay that detected all samples as positive. In addition, the introduction of labeled positive controls (LPC) increased the diagnostic safety of the single as well as the combined assay. Based on the newly developed, alternative assay for the detection of rabies virus and the application of LPCs, an improved diagnostic sensitivity and reliability can be ascertained for postmortem and intra vitam real-time RT-PCR analyses in rabies reference laboratories.

Immunovirological correlates in human rabies treated with therapeutic coma

A 37-year-old woman was admitted to hospital and over the next 5 days developed a progressive encephalitis. Nuchal skin biopsy, analyzed using a Rabies TaqMan(c) PCR, demonstrated rabies virus RNA. She had a history in keeping with exposure to rabies whilst in South Africa, but had not received pre- or post-exposure prophylaxis. She was treated with a therapeutic coma according to the "Milwaukee protocol," which failed to prevent the death of the patient. Rabies virus was isolated from CSF and saliva, and rabies antibody was demonstrated in serum (from day 11 onwards) and cerebrospinal fluid (day 13 onwards). She died on day-35 of hospitalization. Autopsy specimens demonstrated the presence of rabies antigen, viral RNA, and viable rabies virus in the central nervous system.

Ante- and post-mortem diagnosis of rabies using nucleic acid-amplification tests

Sensitivity, specificity and short turn-around time nucleic acid-amplification tests (NATs) have been steadily improving. NATs have been employed in the diagnosis of rabies to distinct different strains, as well as to identify new lyssaviruses. NATs have advantages over traditional methods, such as the direct fluorescence antibody test. They can be applied to fluid samples and brain tissue that is substantially decomposed. NATs can be used as an alternative method for confirmation or exclusion of the diagnosis in a suspected rabies patient. Real-time PCR methods are more favored than conventional reverse-transcription PCR methods by several laboratories. Second-round PCR, either nested or heminested, has been used for ante-mortem diagnosis to detect low levels of RNA. This review the details obstacles in making a diagnosis, how to properly utilize NATs (sample preparation, nucleic amplification techniques, amplification targets and primer design); and interprets the results obtained in recent studies.

Emerging technologies for the detection of rabies virus: challenges and hopes in the 21st century

The diagnosis of rabies is routinely based on clinical and epidemiological information, especially when exposures are reported in rabies-endemic countries. Diagnostic tests using conventional assays that appear to be negative, even when undertaken late in the disease and despite the clinical diagnosis, have a tendency, at times, to be unreliable. These tests are rarely optimal and entirely dependent on the nature and quality of the sample supplied. In the course of the past three decades, the application of molecular biology has aided in the development of tests that result in a more rapid detection of rabies virus. These tests enable viral strain identification from clinical specimens. Currently, there are a number of molecular tests that can be used to complement conventional tests in rabies diagnosis. Indeed the challenges in the 21st century for the development of rabies diagnostics are not of a technical nature; these tests are available now. The challenges in the 21st century for diagnostic test developers are two-fold: firstly, to achieve internationally accepted validation of a test that will then lead to its acceptance by organisations globally. Secondly, the areas of the world where such tests are needed are mainly in developing regions where financial and logistical barriers prevent their implementation. Although developing countries with a poor healthcare infrastructure recognise that molecular-based diagnostic assays will be unaffordable for routine use, the cost/benefit ratio should still be measured. Adoption of rapid and affordable rabies diagnostic tests for use in developing countries highlights the importance of sharing and transferring technology through laboratory twinning between the developed and the developing countries. Importantly for developing countries, the benefit of molecular methods as tools is the capability for a differential diagnosis of human diseases that present with similar clinical symptoms. Antemortem testing for human rabies is now possible using molecular techniques. These barriers are not insurmountable and it is our expectation that if such tests are accepted and implemented where they are most needed, they will provide substantial improvements for rabies diagnosis and surveillance. The advent of molecular biology and new technological initiatives that combine advances in biology with other disciplines will support the development of techniques capable of high throughput testing with a low turnaround time for rabies diagnosis.

Development of real-time reverse transcriptase polymerase chain reaction methods for human rabies diagnosis

To improve timely ante-mortem human rabies diagnosis, methods to detect viral RNA by TaqMan-based quantitative reverse transcriptase polymerase chain reactions (qRT-PCRs) have been developed. Three sets of two primers and one internal dual-labeled probe for each primer set that target distinct conserved regions of the rabies virus N gene were designed and evaluated. Using a collection of 203 isolates representative of the world-wide diversity of rabies virus, all three primers/probe sets were shown to detect a wide range of rabies virus strains with very few detection failures; the RABVD1 set in particular was the most broadly reactive. These qRT-PCR assays were shown to be quantitative over a wide range of viral titer and were 100-1,000 times more sensitive than nested RT-PCR; however, both the standard and real-time PCR methods yielded concordant results when used to test a collection of archived human suspect samples. The qRT-PCR assay was employed to monitor virus load in the saliva of a rabies virus-infected patient undergoing the Milwaukee treatment protocol. However in this case it would appear that reduction of the viral load in the patient's saliva over time did not appear to correlate well with clearance of viral components from the brain.

Furious rabies after an atypical exposure

Heiman Wertheim and colleagues describe the diagnosis and management of two patients who developed rabies after butchering and consuming a dog or a cat.

The management of encephalitis: clinical practice guidelines by the Infectious Diseases Society of America

Guidelines for the diagnosis and treatment of patients with encephalitis were prepared by an Expert Panel of the Infectious Diseases Society of America. The guidelines are intended for use by health care providers who care for patients with encephalitis. The guideline includes data on the epidemiology, clinical features, diagnosis, and treatment of many viral, bacterial, fungal, protozoal, and helminthic etiologies of encephalitis and provides information on when specific etiologic agents should be considered in individual patients with encephalitis.

Neuropathology of viral infections of the central nervous system

Many viral infections of the nervous system cause stereotyped pathologic features and overlapping clinical and imaging features. Neuroimaging usually offers neuroanatomical localization of the pathology, degree of involvement of the nervous system, and response to therapy during follow up in a few instances. Neuroimaging is a useful adjunct for diagnosis.

Lyssaviruses: current trends

Various technological developments have revitalized the approaches employed to study the disease of rabies. In particular, reverse genetics has facilitated the generation of novel viruses used to improve our understanding of the fundamental aspects of rabies virus (RABV) biology and pathogenicity and yielded novel constructs potentially useful as vaccines against rabies and other diseases. Other techniques such as high throughput methods to examine the impact of rabies virus infection on host cell gene expression and two hybrid systems to explore detailed protein-protein interactions also contribute substantially to our understanding of virus-host interactions. This review summarizes much of the increased knowledge about rabies that has resulted from such studies but acknowledges that this is still insufficient to allow rational attempts at curing those who present with clinical disease.

Antemortem diagnosis and prevention of human rabies

Human rabies still continues to be a significant health problem in India and other developing countries where dogs are the major vectors of transmission. Rabies in humans can present in two clinical forms, i.e., furious and paralytic. While diagnosis of furious rabies can be made based on the typical symptoms and signs, paralytic rabies poses a diagnostic dilemma to the neurologists who may encounter these cases in their practice. Although there are certain clinical features that distinguish this disease from other forms of Guillain-Barre syndromes, confirmation of diagnosis may require laboratory assistance. Conventional techniques such as antigen detection, antibody assays and virus isolation have limited success. The recently introduced molecular techniques show more promise in confirming the cases of paralytic rabies. There has not been much success in the treatment of confirmed rabies cases and recovery from rabies is extremely rare. Therefore, preventive measures of this dreaded disease after an exposure become extremely important. The present article reviews the current status of human rabies with regard to antemortem diagnosis, disease management and post-exposure prophylaxis.

Analysis of multiple exon-skipping mRNA splice variants using SYBR Green real-time RT-PCR

Fluorescence-based PCR techniques are becoming an increasingly popular method for measuring low-abundance alternatively spliced mRNA transcripts. The dynamic range of real-time RT-PCR affords high sensitivity for the measurement of gene expression, but this mandates the need for strict controls to ensure assay validity. Primer design, reverse transcription, and cycling conditions need to be optimized to ensure an accurate and reproducible assay. Here, we describe a procedure for creating a cost effective and reliable method for the absolute quantification of several exon-skipping variants of human excitatory amino acid transporter-2 (EAAT2). We show that the cycling conditions can be adjusted to increase the specificity of primers that span exon-exon junctions, and that differences in the reverse transcription reaction can be minimized. Standard curves are stable and produce accurate absolute copy number data. We report that exon-skipping transcripts, EAAT2Delta7 and EAAT2Delta9, account for 5.8% of EAAT2 mRNA in autopsy human neocortex.