Macaca Cynomolgus Research Articles

The pressing need for study on the effects of Mpox on the progression of vascular inflammation: A well-timed call.

This article explored the possibility that the Mpox virus (MPXV) may initiate or stimulate the consequences of vascular inflammation. In 1970, it was discovered that Macaca cynomolgus primates infected with MPXV also infected humans in the Democratic Republic of the Congo. The study demonstrates that MPXV invades host cells via viral proteins and surface receptors, initiating the release of diverse inflammatory mediators such as IL-1, IL-6, TNF-α, CCL2, CXCL2, CXCL8, CXCL10, and so forth probably through endothelial dysfunction by reactive oxygen species production. In general, these mediators have been found to contribute to vascular inflammation and the formation of atherosclerotic plaque at a later stage, which may contribute to the onset of vascular inflammation. The discussed association between vascular inflammation and Mpox has the potential to be an important finding in the field of vascular biology research.

SCID mice as an animal model to evaluate the efficacy of antismallpox drugs

There is currently no animal model to evaluate the preventive efficacy of antiviral drugs for the treatment of smallpox in human patients with a weak immune system. Therefore, the possibility of using outbred severe combined immunodeficiency (SCID) mice as an animal model was examined by electron microscopy and virological, histological, and statistical methods. There were no clinical signs of disease after the intranasal infection of mice with the variola virus (VARV) at a dose of 5.2 log10 PFU (plaque forming unit). At the same time, the median infective dose (ID50) of VARV estimated by registering the presence of the virus in the lungs of animals four days after infection was 3.5 log10 PFU, and thus, was close to that theoretically determined in human patients by identifying the clinical picture of the disease. The reproduction of the virus was detected only in the respiratory organs of mice infected with VARV at a dose of 5.2 log10 PFU (50 ID50). The values of the VARV concentration in the lungs and nose were similar to those observed in human patients and well-known animal models such as Macaca cynomolgus and ICR mice respiratorily infected with almost the same doses of VARV. The known animal models were not shown to be significantly different from SCID mice in terms of the duration of the presence of the virus in the lungs. Moreover, the inflammatory and necrotic pathomorphological changes observed in the respiratory organs of SCID mice were similar to those occurring in other animal models and human patients. The use of SCID mice for evaluating the preventive efficacy of the NIOCH-14 and ST-246 antiviral drugs led to the results agreeing well with the previously reported data. Thus, SCID mice may be used as an experimental animal model for simulating smallpox to develop antiviral drugs for the treatment of human patients with a severe immunosuppressive state.

P.016 Successful transfection of macaca Cynomolgus with cloned human hepatitis B virus

Du fait d’interactions complexes entre le VIH et le virus de l’hépatite B (VHB), le système immunitaire et les traitements anti-rétroviraux, la prise en charge thérapeutique de l’infection par le VHB chez les patients infectés par le VIH doit considérer les deux infections virales. Chez les patients co-infectés VIH-VHB qui ne nécessitent pas de traitement anti-VIH, les molécules anti-VHB qui possèdent une double activité anti-VIH et anti-VHB ne sont pas recommandés (lamivudine, emtricitabine, entécavir, ténofovir disoproxil fumarate) en raison du risque de développement de résistance du VIH. Seul l’adéfovir dipivoxil et l’interféron alpha pégylé peuvent être utilisés. La telbivudine pourrait avoir un rôle en association avec l’adéfovir dipivoxil. En cas d’indication d’un traitement anti-VIH, l’inclusion dans le traitement anti-VIH du ténofovir en association avec la lamivudine ou l’emtricitabine est recommandée. Pour ce qui concerne les patients ayant développé une résistance à la lamivudine (ou emtricitabine), l’adjonction du ténofovir au traitement anti-rétroviral en maintenant la lamivudine ou l’emtricitabine est la solution de choix.Because of complex interactions between HIV, hepatitis B virus (HBV), immune system and antiretrovirals, treatment of HBV infection in HIV population should consider both viruses. In co-infected patients with no indication of antiretrovirals, drugs with dual activity against HBV and HIV are not recommended to avoid development of HIV resistance (lamivudine, emtricitabine, entecavir, tenofovir disoproxil fumarate). Adefovir dipivoxil or pegylated interferon may be used. Telbivudine may have a role in combination with adefovir dipivoxil in this situation. In patients with an indication of antiretroviral therapy, regimens should include tenofovir in association with lamivudine or emtricitabine. In patients who had developed HBV lamivudine (or emtricitabine) resistance addition of tenofovir to antiretroviral regimen including maintenance of lamivudine or emtricitabine is the preferred choice.

A primate model of renal ischemia-reperfusion injury for preclinical evaluation of the antileukocyte function associated antigen 1 monoclonal antibody odulimonab.

We established a primate model to investigate the effects of the antileukocyte function associated antigen 1 (CD 11a) mAb odulimomab (Imtix-Sangstad, Lyon, France) for preventing renal ischemia-reperfusion injury. We randomly divided 34 Macaca cynomolgus monkeys into groups 1 and 2, which received a renal autograft after 2 hours of cold ischemia, and groups 3 and 4, which received the autograft after 24 hours of cold ischemia. Before cold ischemia all harvested kidneys were subjected to 30 to 45 minutes of warm ischemia. Groups 1 and 3 monkeys were treated with an antileukocyte function associated antigen 1 mAb before cold ischemia and then for 3 days, while groups 2 and 4 monkeys received an IgG1 isotype control. In all groups renal function was investigated before warm ischemia and 72 hours after reperfusion. Serum creatinine and the leukocyte count were determined daily. Histological studies were done and lactoferrin was measured in the autotransplanted kidney 72 hours after reperfusion. A decrease in renal function was shown after 2 hours of cold ischemia with tubular necrosis and mild cell infiltration, while after 24 hours of cold ischemia there was severe renal failure with tubular and glomerular necrosis, and leukocyte infiltration. A significant improvement in renal function and decrease in kidney lactoferrin content was evident in group 1 compared to group 2 at 72 hours, while no significant difference was noted in groups 3 and 4. No difference in histological patterns was evident in treated and untreated animals. This study provides evidence for the validity of this ischemia-reperfusion injury model in primates. The protective effects of antileukocyte function associated antigen 1 mAb on renal injury was not as dramatic as in rodent models but a significant improvement in renal function was observed in treated animals after 2 hours of cold ischemia.

A PRIMATE MODEL OF RENAL ISCHEMIA-REPERFUSION INJURY FOR PRECLINICAL EVALUATION OF THE ANTILEUKOCYTE FUNCTION ASSOCIATED ANTIGEN 1 MONOCLONAL ANTIBODY ODULIMONAB

Purpose: We established a primate model to investigate the effects of the antileukocyte function associated antigen 1 (CD 11a) mAb odulimomab (Imtix-Sangstad, Lyon, France) for preventing renal ischemia-reperfusion injury.Materials and Methods: We randomly divided 34 Macaca cynomolgus monkeys into groups 1 and 2, which received a renal autograft after 2 hours of cold ischemia, and groups 3 and 4, which received the autograft after 24 hours of cold ischemia. Before cold ischemia all harvested kidneys were subjected to 30 to 45 minutes of warm ischemia. Groups 1 and 3 monkeys were treated with an antileukocyte function associated antigen 1 mAb before cold ischemia and then for 3 days, while groups 2 and 4 monkeys received an IgG1 isotype control. In all groups renal function was investigated before warm ischemia and 72 hours after reperfusion. Serum creatinine and the leukocyte count were determined daily. Histological studies were done and lactoferrin was measured in the autotransplanted kidney 72 hours af...

Fiber type population in limb muscles ofMicrocebus murinus

Populations and distributions of fiber types were studied in 19 limb muscles ofMicrocebus murinus. Proportions and cross-sectional areas of muscles fiber types were compared with data from the literature for other prosimians (Galago, Lemur, andNycticebus), another primate (Macaca cynomolgus), and the rat.

Significance of glycosidases and phosphatases in Cercopithecus and Macaca cells

1. 1. When selected ratios of different glycosidases and phosphatases from primary monkey kidney cells or from monkey kidney cell lines are presented graphically, characteristic patterns do evolve. 2. 2. Three different subtypes of Vero cells show similar glycosidase patterns. 3. 3. The Vero subtypes tested show glycosidase patterns that are closely similar to those of primary cells of Cercopithecus aethiops. 4. 4. Glycosidase patterns of BS-C-1 and CV-1 cells are less similar to those of primary Cercopithecus cells than are those of Vero cells. 5. 5. Primary kidney cells from Macaca cynomolgus show significantly different glycosidase patterns compared with those of different Cercopithecus cells. 6. 6. The distinct glycosidase patterns can be used to classify the tested cell lines in relation to each other.

Potentials for root resorption during periodontal wound healing.

The present study was undertaken to examine whether (1) the process of resorption, which invariably affects periodontitis involved reimplanted roots facing bone or gingival connective tissue during healing, is a transient phenomenon and, (2) root resorption can be prevented by permitting downgrowth of epithelium along the root surface. A total of 24 teeth in 2 monkeys (Macaca cynomolgus) was subjected to experimental periodontal tissue breakdown by the placement of elastic ligatures around the teeth. The ligatures were left in situ until about 50% of the supporting tissues had been lost. Following removal of the ligatures, the teeth were extracted and the denuded portions of the roots were scaled and planed. The crowns of the teeth were resected and the root canals filled with guttapercha. The roots were subsequently implanted into sockets prepared in the jaw bone in such a way that each root was embedded in bone except for a portion which was in contact with gingival connective tissue. 1 month prior to sacrifice of the animals, the cut surface of the coronal part of the roots was exposed by removal of the covering soft tissue. The epithelium was thereby allowed to migrate into the wound. Implantation of the roots was scheduled to provide healing periods of 1, 2, 3, 4, 8, 12, 16, 20 and 24 weeks before exposure of the roots. The histologic examination of the implant specimens disclosed that replacement resorption was a progressive process which eventually resulted in the elimination of the transplanted roots. It was possible to prevent root resorption in this model by permitting apical downgrowth of epithelium along the root surface during the initial phase of healing. The results are discussed in relation to procedures used in periodontal therapy.

Scaling and root planing in shallow pockets.

The present study was undertaken to enable histological assessment of attachment level alterations following repeated scaling and root planing in periodontal sites with "normal" sulcus/pocket depth. Two monkeys (Macaca cynomolgus) were used. During a period of 6 months, scaling was carried out once every 2 weeks at the buccal surfaces of premolars and molars on the right side of the jaws. The contralateral teeth served as untreated controls. Six months after the completion of treatment (1 year after the start of the experiment), the animals were sacrificed and histological sections of all test and control teeth were produced. In these sections the distances between the cemento-enamel junction (CEJ) and the apical extent of the junctional epithelium (JE) and between the JE and the alveolar bone crest (BC) were measured. The results revealed that repeated scaling and planing resulted in an average loss of connective tissue attachment amounting to 0.39 mm and in a corresponding recession of the alveolar bone crest. The findings are discussed in relation to recent observations from clinical trials demonstrating loss of clinical attachment following repeated scaling and root planing in sites with shallow gingival pockets.

Healing following surgical treatment and root demineralization in monkeys with periodontal disease.

Abstract The aim of the present investigation was to study the potential for new attachment to root surfaces which 1) had become devoid of attachment either by mechanical removal or in conjunction with experimental periodontal tissue breakdown and 2) subsequently had been conditioned with citric acid. Three adult monkeys (Macaca cynomolgus) were used. Periodontal pockets were produced during a 2–6‐month period around the maxillary central incisors and first and second premolars and around the mandibular central incisors by the placement of orthodontic elastics. Surgical treatment of the pockets was carried out with the use of a flap procedure. During surgery, the roots of the premolars on the right side of the jaws were first scaled and planed and subsequently treated with citric acid. Citric acid conditioning was not performed on the premolars of the left side. In the front tooth regions the surgical treatment included citric acid conditioning of the mandibular central incisors in two animals and of the maxillary central incisors in one animal.Surgical procedures were also carried out around the mandibular second premolars and first molars which had not been exposed to periodontal tissue breakdown. Folio wing flap elevation, the buccal bone plate was mechanically removed within an area corresponding to that of bone loss produced by the experimental periodontitis model in the maxillary premolars. The cementum layer of the surgically denuded portion of the roots was removed by root planing.In all treated teeth, a notch was prepared in the buccal root surfaces at the level of the alveolar bone crest. Six months following treatment the animals were sacrificed and histologic sections prepared. Linear measurements were made along the root surface from the apical border of the prepared notch to the apical termination of the junctional epithelium and to the crest of the alveolar bone.The results demonstrated that cementum formation and new connective tissue attachment did not occur on root surfaces previously exposed to periodontal pockets and subsequently subjected to scaling and root planing or on root surfaces surgically deprived of their supporting bone and previously “non‐exposed” cementum layer. Cementum formation and new connective tissue attachment also failed to occur following citric acid conditioning of root dentin surfaces. In all sections representing all three treatment groups, the attachment between the gingiva and the root was established by epithelium.

Urinary excretion of an uracilic metabolite from caffeine by rat, monkey and man

Caffeine (C) metabolism has been studied in rat, monkey ( Macaca cynomolgus) and man after oral administration of the compound. Eleven metabolites were quantified in urine; particular attention has been drawn to 4-amino [5-formyl methylamino]1,3-dimethyl uracil (ADMU) because of its structural analogies with 5-fluorouracil. The rat has been found to produce a much larger fraction of ADMU (about 30%) in respect to monkey and man (1–2%). The potential toxicological implications of this findings are discussed.

Healing following implantation of periodontitis-affected roots into gingival connective tissue.

The aim of the present investigation was to examine if a new connective tissue attachment can be established on a previously periodontitis involved root surface, located in contract with gingival connective tissue during healing. A total of 28 teeth in one dog (beagle) and two monkeys (Macaca cynomolgus) were subjected to experimental periodontal tissue breakdown by placing cotton floss ligatures or orthodontic elastics around the teeth. The ligatures were left in situ until about 50% of the supporting tissues had been lost. Following resection of the crowns, the teeth were root filled and the exposed parts of the roots thoroughly scaled and planed. Each root was extracted and implanted into grooves prepared in edentulous areas of the jaws in such a way that the root was embedded to half its circumference in bone, leaving the remaining part to be covered by the gingival connective tissue of the repositioned flap of the recipient site. Root implantation and sacrifice of the animals were scheduled to allow for observation periods of 2 and 3 months of healing. An analysis of histologic specimens, obtained from biopsies of the recipient site tissues, disclosed that a new fibrous attachment failed to form on a previously "exposed" root surface located in contact with gingival connective tissue. In areas of the roots where the periodontal ligament tissue was preserved prior to transplantation, a fibrous reattachment occurred between the root and the adjacent gingival tissue. The results indicate that gingival connective tissue does not possess the ability to establish conditions which enable the formation of a new connective tissue attachment.

Organization of somatic thalamus in monkeys with and without section of dorsal spinal tracts

In an attempt to understand the modifications which appear at the thalamic level when dorsal cord sections are performed, peripheral fields of thalamic units were studied in normal and dorsal-cord sectioned monkeys, totally awake and implanted with glass micropipettes. Six normal Macaca cynomolgus and 7 having received spinal sections, were studied. Ventricular radiography was performed and all the coordinates were related to new stereotaxic coordinates using the posterior commissure as the origin. Cell-bodies and axon units were recognized on the basis of the shape of the spikes. In normal animals, 972 units were studied; 307 were thalamic units with peripheral fields and 177 were derived from cell bodies. Localization of these cells was studied as a function of their peripheral field and response characteristics. The majority of ventralis posterior (VP) cell bodies were only activated by contralateral stimulation, their peripheral field being frequently found on the extremities. Somatotopic organization consisted of concentric layers rather than zones in apposition. Dorsoventral segregation of afferent modality sensitivity (movement, pressure, light touch) was observed. Somatosensory convergence was found in VP inferior (VPi) as well as convergence of different types of afferents on a few VP cells. Units responding to bilateral or ipsilateral stimulations were found only in posterior VP and in surrounding nuclei. A particular somatotopy was shown to exist in n. reticularis. A total of 838 units were studied in animals having had dorsal columns and Morin's bundle severed. Only a few cells (13) responded in VP1 to contralateral hindlimb stimulation. Their characteristics recall those noted in layer V spinal cord cells. The other cells (55) still driven by a hindlimb were dispersed in the nuclei just adjacent to VP1. The majority of cells found in the VP1 were activated from the forelimb. They were observed in their normal VP1 localization as well as in areas where hindlimb representation was found in normal animals. This change of afferent input is attributed to a reinnervaration of hindlimb cells (probably at the gracilis level) by sprouting from forelimb afferent.

Endotoxic activities of lipopolysaccharides of microorganisms isolated from an infected root canal in Macaca cynomolgus

Lipopolysaccharides (LPS) prepared from a strain of Bacteroides oralis, a strain of Fusobacterium necrophorum, and a strain of F. nucleatum, all isolated from an infected root canal in monkey (Macaca cynomolgus), were examined for endotoxic activities using primary skin reactions in rabbits and induction of leukocyte chemotaxis in rats. LPS of B. oralis showed considerably lower ability to cause skin inflammation than LPS of the fusobacteria. However, the leukotactic effect of the LPS preparations as determined by the wound chamber method in rats was approximately of the same proportion. In both tests the reactions were compared with those of commercial LPS of Salmonella typhi. This study shows that endotoxic LPS can be isolated from oral Gram-negative bacteria, which have infected the root canal. Therefore LPS may play a role in the development and maintenance of chronic inflammation of the periapical tissues.

Respiratory pathogens in non-human primates with special refererence to Corynebacterium ulcerans

An investigation of 272 non-human primates (75 Macacca cynomolgus, 97 Macacca mulatta and 100 Cercopithecus aethiops) revealed a high incidence of respiratory disease caused by Corynebacterium ulcerans, Staphylococci, Diplococci and Streptococci. Escherichia coli was also found as a secondary invader. Most of the infections occurred during winter in Macaca cynomolgus and were caused by Corynebacterium ulcerans and Diplococcus pneumoniae. The C. ulcerans strains were phage type VI G. A phage type III C strain was isolated from a Macacca mulatta. The high incidence of C. ulcerans suggests that this organism plays a significant role in the pathology of respiratory disease in the non-human primate.

Responses of subthalamic and pallidal neurons to striatal stimulation: an extracellular study on awake monkeys

The unitary activity of subthalamic neurons (corpus Luysii) and of GP neurons was recorded extracellularly on awake monkeys ( Macaca cynomolgus). Striatal stimulation induces in subthalamic (Sth) neurons a short latency spike discharge (10–15 msec) followed by a long lasting depression of the spontaneous activity. As, according to anatomical studies, the subthalamic nucleus is principally connected to the globus pallidus (GP), electrophysiological relations between striatal and GP neurons and between GP and Sth neurons were studied. Striatal stimulation induced an inhibitory-excitatory sequence in GP neurons and pallidal stimulation induced only a depression of the activity of Sth neurons. Since no GP neurons are excited at short latency by striatal stimulation, possible events along a striato-subthalamic pathway are discussed.

Experimental Dirofilariasis in Macaques

In this third of a series of studies on experimental dirofilariasis in primate hosts, 3 Macaca cynomolgus, 6 M. speciosa, and 2 M. mulatta were inoculated with infective larvae of Dirofilaria tenuis, a parasite of the raccoon, and were killed at periods ranging from 2 weeks to 13 months of infection. One M. mulatta and one M. speciosa were treated daily with prednisolone beginning 2 months after inoculation; worms were recovered from these and 5 other monkeys (7 of 11). Microfilaremia was detected during the 28th week of infection in a monkey under prednisolone treatment. Microfilaremia was found to be aperiodic in that monkey and in a raccoon. Eosinophilia and antibodies to the microfilaria reached appreciable levels in three monkeys harboring gravid worms. Development of D. tenuis in M. speciosa appeared to be comparable to that observed in man.

Evoked cortical responses to vagal, laryngeal and facial afferents in monkeys under chloralose anaesthesia

Previous experiments have studied the projection of spinal somatic inflows to monkey motor cortex, but vagal and superior laryngeal nerve projections had not been previously explored. They have been sought and placed among the projections of facial inflow to the motor and sensory cortices in Macaca cynomolgus under chloralose anaesthesia. 1. 1. With a macro-electrode evoked potential technique, somatotopy was found in the motor cortex, but to a lesser extent than in the sensory cortex; three areas of total convergence were present in motor cortex, but none in the inferior sensory cortex. 2. 2. The shortest latencies were found in the sensory cortex, but there was almost complete overlap in the range of latencies for motor and sensory cortices. The topography of response latencies was evenly distributed for the tongue and laryngeal nerves, whereas that for the hands, lip and vagus nerve showed clear patterns of short or long latency. 3. 3. Trains of stimuli were more effective in producing large evoked potentials in motor cortex, whereas single shocks were almost equally effective for sensory cortex. 4. 4. An area just anterior to the tip of the rolandic fissure, homologous to Broca's area in the human, showed convergence and interaction of short latency responses to stimulation of the vagus and laryngeal nerves, face, hands and tongue. 5. 5. Single cell responses to facial, tongue and anterior limb stimuli were examined in an area surrounding the base of the rolandic fissure in the monkey. Natural and electrical stimulation were used and recordings were taken from both the so-called motor and sensory sides of the fissure. The area antero-ventral to the tip of the rolandic fissure, around the frontal inferior sulcus and probably homologous to Broca's area in the human, was studied in particular. 6. 6. Cells in the motor cortex were primarily responsive to natural stimulation by pressing, pinching, moving and stretching tissue, and difficult to drive by electrical single shock stimulation; cells in the sensory cortex were in general equally responsive to electrical or natural stimulation of the tissue. 7. 7. Tonic responses prevailed on the motor side whereas phasic responses were the rule on the sensory side. 8. 8. The effective stimulus area was very localized for cells in the sensory cortex and much larger for cells in the motor cortex. 9. 9. Cells in the area homologous to Broca's responded to natural stimulation initiating movements generally associated with vocalization.

Studies on the metabolism of isoniazid in subhuman primates.

SummaryTests for a polymorphism of isoniazid acetylation were performed in rhesus (Macaca mulatto) and cynomolgus (Macaca cynomolgus) monkeys and in mangabeys (Cercocebus fulliginosus) by studying the urinary excretion of isoniazid and its metabolites after intramuscular injection. In general, the patterns of metabolites excreted in urine of these species were qualitatively similar to those found previously in man. However, neither rhesus nor cynomolgus monkeys exhibited a polymorphism for isoniazid acetylation that is characteristic of human populations. Furthermore, rhesus monkeys showed no parallelism in capacities to acetylate isoniazid and sulfamethazine. Other results suggested that mangabeys exhibited a polymorphism for isoniazid acetylation.

Comparative Susceptibility of Kidney Cells from Different Monkey Species to Enteric Viruses (Poliomyelitis, Coxsackie, and Echo Groups)

Summary Kidney tissue cultures of 13 species of monkeys and 4 species of baboons were tested for comparative susceptibility to the enteric viruses belonging to the poliomyelitis, Coxsackie and echo groups. Cells from sooty mangabey (Cercocebus fuliginosus), white-crowned mangabey (Cercocebus torquatus lunulatus), and diana (Cercopithecus diana roloway) monkeys from Africa, and cynomolgus (Macaca cynomolgus) monkeys from Singapore and the Philippine Islands, closely resembled the cells of rhesus monkeys (Macaca mulatta) from India in their high susceptibilities to the viruses tested. Cells from the African red grass monkey (Erythrocebus patas) were found to be twice as susceptible as rhesus cells to polioviruses, and about equally susceptible to echo types 7, 8, and 12, and Coxsackie group B viruses. However, patas cells were resistant to plaque production when exposed to Coxsackie A9, and echo virus types 1, 3, 4, 6′, 9, and 14. Similar results were obtained with African white-nosed (Cercopithecus nictitans buttikoferi), mona (Cercopithecus mona campbelli) and mustache (Cercopithecus cephus) monkeys. African green (Cercopithecus aethiops sabaeus) and tantalus (Cercopithecus aethiops tantalus) monkeys yielded cells highly susceptible to all three groups of viruses tested, showing even greater susceptibility than rhesus cultures to the echo viruses. Four species of baboon (Papio papio, P. cynocephalus, P. doguera, and Mandrillus leucophaeus) yielded kidney cultures almost equal to rhesus cultures in susceptibility to poliovirus. Coxsackie virus A9 and echo virus type 1 were not cytopathogenic in yellow baboon (P. cynocephalus) cultures, while drill baboon (M. leucophaeus) cells proved highly susceptible to echo viruses. Poliovirus plaques were produced in the lemur, Perodicticus potto. The suggestion is made that cells of differing susceptibilities might offer advantages for isolations of enteric viruses from clinical specimens; they might be used as differential media are in the isolation of enteric bacterial colonies. Because of the greater susceptibility of patas cells over those of rhesus or cynomolgus, they also offer an advantage for the detection of small amounts of poliovirus.