Seropositive Rats Research Articles

Deciphering the Hantavirus Host Range Combining Virology and Species Distribution Models with an Emphasis on the Yellow Pygmy Rice Rat (Oligoryzomys flavescens)

Hantaviruses are the causative agents of hantavirus pulmonary syndrome (HPS) in the Americas. In Central and South America, 28 hantavirus lineages were associated with different Sigmodontinae rodents. Of these, Lechiguanas hantavirus was initially described as a lineage associated with HPS cases in the central region of Argentina. Initial studies on the rodent hosts and viral lineages performed between 1999 and 2005 showed that HPS cases in Uruguay were distributed mostly in the southern region of the country, and that the Lechiguanas hantavirus (LECV) and the closely related Andes Central Plata hantaviruses were the viral lineages most frequently associated with HPS cases, both carried by the yellow pygmy rice rat (Oligoryzomys flavescens). Although these rodents are present all across the Uruguayan territory, determining the extent of the risk areas for hantavirus transmission based on the distribution of the infected rodents may be a useful tool for disease control and prevention. Distribution models are positioned as an effective instrument in the prediction of diseases affecting human health. Assessment of the potential distribution of rodent reservoir hosts and analysis of the influence of environmental factors on hantavirus transmission can help to understand the spatial patterns of disease transmission risk. In the present study, virological studies and species distribution models were integrated to understand the hantavirus infection risk pattern in Uruguay. Virological analyses confirmed that in Uruguay, the primary hantavirus reservoir host for both viral lineages is the yellow pygmy rice rat. Additionally, we report an Azara’s grass mouse (Akodon azarae) infected with the Andes Central Plata viral lineage. Based on the seropositive and nonseropositive yellow pygmy rice rats tested, the distribution models emphasized that favorable environmental conditions for the infected rodents are mainly related to the availability of human-disturbed rural environments with high humidity. We conclude that the innovative application of the methodologies reported herein allowed for the assessment of the current risk territory for HPS in Uruguay.

Toxoplasma gondii in invasive animals on the Island of Fernando de Noronha in Brazil: Molecular characterization and mouse virulence studies of new genotypes

This study aimed to genetically characterize and to determine virulence from Toxoplasma gondii samples from invasive animals in the Island of Fernando de Noronha, Brazil. Blood samples were collected from 21 tegu-lizard (Salvator merianae), 12 rock-cavies (Kerodon rupestris) and 154 black-rats (Rattus rattus) from the Island and MAT (cutoff 1:25) detected anti-T. gondii antibodies in 0% of the tegus (0/21); 58.3% of the rock-cavies (7/12) and 22.7% of rats (35/154). Tissue samples (brain, heart, liver and lung) from positive animals in MAT were collected for molecular analysis and for bioassay in Swiss Webster mice. After observation period, mice were euthanized, and serological detection and tissue cyst search in the brain were performed. The brain of positive animals for serological detection or tissue cyst search was cultured in MARC-145 cells for maintenance of the T. gondii isolate. No isolate was obtained from rock cavies. Nine isolates were obtained by bioassay of 35 seropositive black rats. DNA samples were extracted from rat tissues and from parasite isolates in cell culture, and genotyped using 10 PCR-RFLP markers. ToxoDB genotypes #78 (1) from rat tissue and #146 (4), #163 (2), #260 (2) and #291 (1) from cell culture were detected. Markers of genes ROP18 and ROP5 were analyzed and in vivo virulence test was conducted in mice. Analysis revealed two allele combinations, 3/1 and 3/3, indicating non-lethal T. gondii strains, which is supported by mouse virulence test.

Detection of serum antibodies against Leptospira spp. in brown rats (Rattus norvegicus) from Grenada, West Indies.

Background and Aim:Leptospirosis is an emerging disease of animals and humans. Among rodents brown rats (Rattus norvegicus) are an important reservoir of bacteria Leptospira. There is a paucity of information on reservoirs of Leptospira in Grenada. This study was conducted to estimate the prevalence of antibodies against Leptospira spp. in brown rats in a densely human populated area of Grenada.Materials and Methods:Blood samples from 169 brown rats were collected and sera screened for antibodies against Leptospira spp. using enzyme-linked immunosorbent assay.Results:Among a total of 169 brown rats trapped in two parishes in Grenada, 77/169 (45.5%) were positive for Leptospira spp. antibodies. A significant difference in seropositive population of brown rats between two collection sites was observed. No differences were found between sex and age of seropositive rats.Conclusion:Due to the close contact of brown rats with humans in Grenada, rats should be considered a high-risk factor in transmission of Leptospira to humans. Appropriate preventive measures should be instituted to prevent the transmission of Leptospira infection to humans.

Noninvasive, Targeted Creation of Neuromyelitis Optica Pathology in AQP4-IgG Seropositive Rats by Pulsed Focused Ultrasound.

Neuromyelitis optica spectrum disorders (herein called NMO) is an autoimmune disease of the CNS characterized by astrocyte injury, inflammation, and demyelination. In seropositive NMO, immunoglobulin G autoantibodies against aquaporin-4 (AQP4-IgG) cause primary astrocyte injury. A passive transfer model of NMO was developed in which spatially targeted access of AQP4-IgG into the CNS of seropositive rats was accomplished by pulsed focused ultrasound through intact skin. Following intravenous administration of microbubbles, pulsed ultrasound at 0.5 MPa peak acoustic pressure was applied using a 1 MHz transducer with 6-cm focal length. In brain, the transient opening of the blood-brain barrier (BBB) in an approximately prolate ellipsoidal volume of diameter ∼3.5 mm and length ∼44 mm allowed entry of IgG-size molecules for up to 3-6 hours. The ultrasound treatment did not cause erythrocyte extravasation or inflammation. Ultrasound treatment in AQP4-IgG seropositive rats produced localized NMO pathology in brain, with characteristic astrocyte injury, inflammation, and demyelination after 5 days. Pathology was not seen when complement was inhibited, when non-NMO human IgG was administered instead of AQP4-IgG, or in AQP4-IgG seropositive AQP4 knockout rats. NMO pathology was similarly created in cervical spinal cord in seropositive rats. These results establish a noninvasive, spatially targeted model of NMO in rats, and demonstrate that BBB permeabilization, without underlying injury or inflammation, is sufficient to create NMO pathology in AQP4-IgG seropositive rats.

Role of Rats ( Rattus norvegicus) in the Epidemiology of Toxoplasma gondii Infection in Grenada, West Indies.

Rodents are known to be reservoir hosts of Toxoplasma gondii infection for other animals, such as cats and pigs. From February to July 2017, 167 rats ( Rattus norvegicus) were trapped in Grenada, and serum, heart, skeletal muscle, and brain were examined for T. gondii infection by serological examination (modified agglutination test, 1:25) for T. gondii antibodies and for viable parasites by bioassay in mice. Samples of heart, skeletal muscle, and brain of all rats were bioassayed in Swiss Webster (SW) outbred albino mice and interferon gamma gene knockout (KO) mice. Toxoplasma gondii was isolated from heart and brain from 1 rat; this was the only seropositive rat. The T. gondii strain was avirulent for SW mice but killed KO mice. Tissue cysts were detected in the brains of SW mice, and tachyzoites were detected in the lungs of KO mice that died of acute toxoplasmosis. The strain was propagated in cell culture, and DNA derived from cell-cultured tachyzoites was genotyped using the 10 PCR restriction fragment length polymorphisms (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). The strain was a clonal Type III (ToxoDB genotype no. 2) strain. Although the prevalence of T. gondii in humans and animals in Grenada is high, rats seem to have little importance in the transmission of T. gondii on this island.

Abiotic and Biotic Contributors to Support Inter-Epidemic Francisella tularensis in an Agricultural Peri-Urban Environment.

To characterize the inter-epidemic ecology of Francisella tularensis, we surveyed vertebrates and invertebrates for the abundance, spatial distribution, and status of infection at a site in northern California that had evidence of endemic type B tularemia. We collected 2910 mosquitoes, 77 biting flies, 704 ticks, 115 mammals, and 1911 aquatic invertebrates in 2013-2014. Real-time PCR on all mosquitoes, 40 biting flies, 113 aquatic invertebrates, and 650 ticks did not detect F. tularensis DNA. Indirect enzyme linked immunosorbent assay (ELISA) on 109 mammals revealed 2 (of 2, 100%) seropositive feral cats, 1 (of 24, 4.5%) seropositive black rat, and 5 (of 10, 50%) seropositive Virginia opossums. A riparian reserve, ∼1 km from the primate research center, had the highest seroprevalence in mammals and the highest capture success for invertebrate vectors whereas opossums, cats, and ground squirrels in close proximity to the primate center had high seroprevalence and abundant fleas. Well-vegetated regions with standing water appeared to be ideal habitats for biotic components of tularemia enzootic persistence. Mesocarnivores may facilitate the spread of F. tularensis, and high densities of rodents and their fleas may be a mechanism for amplification and spillover.

First Observation of Leptospira interrogans in the Lungs of Rattus norvegicus.

We report the first two cases of pulmonary presence of leptospires in apparently healthy rats captured in a city park in Lyon (France). Only renal carriage of Leptospira has been described in the literature. Blood serology was performed in parallel with molecular and histological analyses of the kidney and lung samples. We isolated leptospires from the kidneys of two out of three seropositive wild rats. These results were confirmed by specific detection of pathogenic Leptospira by real-time PCR. Moreover, Leptospira DNA was detected in lung tissues. Immunohistochemistry and Warthin-Starry staining revealed that leptospires were present on the surface of the ciliated epithelium of the bronchi. Using PCR of the rrs (16S) gene and Multispacer Sequence Typing, DNA extracts of the kidney and lung were identified as belonging to Leptospira interrogans serovar Icterohaemorrhagiae “CHU Réunion.” This first observation of the presence Leptospira in the lung with simultaneous renal carriage will require further study in future on several target organs to gain a better understanding of the Leptospira infection in wild rat.

Transcriptome markers of viral persistence in naturally-infected Andes Hantavirus (Bunyaviridae) seropositive rice rats

The long-tailed pygmy rice rat ( Oligoryzomys longicaudatus ) is the reservoir host of Andes (ANDV) and Oran hantaviruses ( Bunyaviridae ). To examine transcriptome features of persistently infected rice rats, spleens from ANDV sero-positive wild-caught rice rats were assessed. RNA-seq analysis, de novo reference-independent assembly and stringent orthology assignments produced 17,756 unique coding and non-coding RNAs. Differential expression analysis of persistently-infected seropositive rice rat spleens revealed 18 differentially expressed transcripts from 16 unique genes. A three-pronged effect on the immune response were observed in 1) suppression of the JAK-STAT pathway at Stat5b and Ccnot1, as well as 2) a bias toward a TH2 response in the enrichment of caspase-1 and 3) stimulation of RIG-I pathway factors Ppp1cc and MFF. Two of these differentially expressed transcripts, caspase-1 and STAT5b, code for proteins expected to stimulate T helper follicular (T FH ) cell development, a phenomenon that has also been described for hantavirus-infected P. maniculatus . Differential expression of a single seropositive rice rat with a higher viral load revealed a robust response of 243 differentially expressed transcripts, suggesting an acute infection. Together, these data help define the fundamental features of the immune response in a hantavirus reservoir host.

Neuromyelitis optica pathology in rats following intraperitoneal injection of NMO-IgG and intracerebral needle injury.

IntroductionAnimal models of neuromyelitis optica (NMO) are needed for drug testing and evaluation of NMO disease pathogenesis mechanisms.ResultsWe describe a novel passive-transfer model of NMO in which rats made seropositive for human anti-aquaporin-4 (AQP4) immunoglobulin G antibody (NMO-IgG) by intraperitoneal (IP) injections were subject to intracerebral needle injury. Following a single IP injection, NMO-IgG distributed rapidly to peripheral AQP4-expressing cells (kidney collecting duct, gastric glands, airways, skeletal muscle) and area postrema in brain, but not elsewhere in the central nervous system; however, no pathology was seen in brain, spinal cord, optic nerve or peripheral tissues. After testing various maneuvers to produce NMO-IgG-dependent pathology in brain, we found that transient puncture of brain parenchyma with a 28-gauge needle in NMO-IgG seropositive rats produced robust NMO pathology around the needle track, with loss of AQP4 and glial fibrillary acidic protein, granulocyte and macrophage infiltration, centrovascular deposition of activated complement, and blood–brain barrier disruption, with demyelination by 5 days. Pathology was not seen in rats receiving control (non-NMO) human IgG or in NMO-IgG-seropositive rats made complement-deficient by cobra venom factor. Interestingly, at 1 day a reversible, multifocal astrocytopathy was seen with loss of AQP4 and GFAP (but not myelin) in areas away from the needle track.ConclusionsNMO-IgG-seropositivity alone is not sufficient to cause NMO pathology in rats, but a single intracerebral needle insertion, without pre-existing inflammation or infusion of pro-inflammatory factors, was sufficient to produce robust NMO pathology in seropositive rats.

Intrastriatal injection of interleukin-1 beta triggers the formation of neuromyelitis optica-like lesions in NMO-IgG seropositive rats.

BackgroundNeuromyelitis optica (NMO) is a severe, disabling disease of the central nervous system (CNS) characterized by the formation of astrocyte-destructive, neutrophil-dominated inflammatory lesions in the spinal cord and optic nerves. These lesions are initiated by the binding of pathogenic aquaporin 4 (AQP4)-specific autoantibodies to astrocytes and subsequent complement-mediated lysis of these cells. Typically, these lesions form in a setting of CNS inflammation, where the blood–brain barrier is open for the entry of antibodies and complement. However, it remained unclear to which extent pro-inflammatory cytokines and chemokines contribute to the formation of NMO lesions. To specifically address this question, we injected the cytokines interleukin-1 beta, tumor necrosis factor alpha, interleukin-6, interferon gamma and the chemokine CXCL2 into the striatum of NMO-IgG seropositive rats and analyzed the tissue 24 hours later by immunohistochemistry.ResultsAll injected cytokines and chemokines led to profound leakage of immunoglobulins into the injected hemisphere, but only interleukin-1 beta induced the formation of perivascular, neutrophil-infiltrated lesions with AQP4 loss and complement-mediated astrocyte destruction distant from the needle tract. Treatment of rat brain endothelial cells with interleukin-1 beta, but not with any other cytokine or chemokine applied at the same concentration and over the same period of time, caused profound upregulation of granulocyte-recruiting and supporting molecules. Injection of interleukin-1 beta caused higher numbers of blood vessels with perivascular, cellular C1q reactivity than any other cytokine tested. Finally, the screening of a large sample of CNS lesions from NMO and multiple sclerosis patients revealed large numbers of interleukin-1 beta-reactive macrophages/activated microglial cells in active NMO lesions but not in MS lesions with comparable lesion activity and location.ConclusionsOur data strongly suggest that interleukin-1 beta released in NMO lesions and interleukin-1 beta-induced production/accumulation of complement factors (like C1q) facilitate neutrophil entry and BBB breakdown in the vicinity of NMO lesions, and might thus be an important secondary factor for lesion formation, possibly by paving the ground for rapid lesion growth and amplified immune cell recruitment to this site.

Partial genetic characterization of Seoul hantavirus in rats from Buenos Aires City, Argentina, and generation of a Seoul recombinant nucleoprotein antigen

Hemorrhagic fever with renal syndrome (HFRS) is a severe infectious disease characterized by fever, hemorrhage, renal impairment, and thrombocytopenia. At least seven hantaviruses cause HFRS: Hantaan, Seoul (SEOV) (distributed worldwide), Dobrava/Belgrade, Saaremaa, Amur, Thailand and Puumala. To investigate the epidemiology of HFRS and virus transmission in Argentina, we constructed a prokaryotic plasmid encoding the SEOV rNP, of 430 amino acids. After expression, the rNP was tested as an antigen for use in an enzyme-linked immunosorbent assay for infection diagnosis. To determine the current level of virus transmission in wild brown rats or Norway rats (Rattus norvegicus) captured in Buenos Aires City, Argentina, we tested tissues from rats that were determined to be serologically positive for the SEOV, and the viral genome were detected by RT-PCR using specific primers for two fragments of M segment-encoding Gn and Gc proteins. The viral genome was detected in 11 of 21 seropositive rats (52.4%) captured in two parklands. Sequence analysis of a 333-nt region of the Gc-encoding M segment revealed 97% and 96% identity with strains of SEOV from Baltimore and Brazil, respectively. Our genetic data confirm a very low diversity among SEOV virus strains.

Human T-lymphotropic virus type-1 (HTLV-1) in Israeli patients and their family relatives and its transmission to rats

We tested the possibility that lymphocytes, sera and saliva, obtained directly from healthy human T-lymphotropic virus type 1 (HTLV-1) carriers and patients with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) of Iranian Mashhadi origin, as well as lymphocytes from patients with mycosis fungoides (MF) and their family relatives (MFR), may be infective. Peripheral blood mononuclear cells (PBMC), sera, PBMC cultured with phytohaemagglutinin A and phorbol myristate acetate, cell-free supernatant from these cultures, saliva cells and cell-free saliva were injected into adult WKA (n=107) and F344 (n=47) female rats. The appearance of anti-HTLV-1 antibodies in the rat sera was tested by particle agglutination assay and ELISA, and positive results were confirmed by western blot assay. Higher titers (1:1024) of anti-HTLV-1 antibodies were found in the F344 rats as compared to the WKA rats (1:256). The PA agglutination test was the most sensitive for the detection of HTLV-1 antibody. The HTLV-1 provirus was detected in both strains of rats infected with body fluids and cells from the Iranian Mashhadi Jews, in various organs (PBMC, spleen, thymus, salivary glands, spinal cord, kidney and brain) by nested PCR. However, the HTLV-1 provirus was not detected in 100% of the rats. The negative rats were only immunized and not infected. The spleen, thymus, spinal cord and salivary glands of the seropositive rats were found to be infectious and to transmit the HTLV-1 to healthy rats. F344 rats infected with PBMC cultures obtained from HTLV-1 antibody positive MF patients and their MFR who were only 20% positive showed anti-HTLV-1 antibodies, but only in 20% of rats without showing the HTLV-1 provirus; these rats were probably not infected but only immunized. This is one of the few studies on the transmission of HTLV-1 to rats by inoculation with human infectious fluids or cells from HTLV-1 infected healthy carriers (42%), HAM/TSP patients of Iranian Mashhadi origin (58%) as well as lymphocyte cultures obtained from HTLV-1 antibody positive MF and MFR of nonIranian origin.

Finding of Neospora caninum in the wild brown rat (Rattus norvegicus).

Nine rats (16.4%) out of 55 (Rattus norvegicus) from cattle farms were seropositive to Neospora caninum. Two of the seropositive rats were also PCR positive but all were negative by immunohistochemistry and PAS staining. The brains of all the captured rats were homogenized and initially inoculated intraperitoneally into nude mice or into SPF ICR mice, which had been immunosuppressed with prednisolone. One mouse that was inoculated with brain material from a seropositive rat became infected with N. caninum, as demonstrated by the presence of a tissue cyst in the brain and confirmed by immunohistochemistry and PCR. This is the first finding of N. caninum in naturally infected farm rats. The findings show that natural N. caninum infection occurs in wild brown rats and thus rats may serve as a reservoir for the protozoan on the cattle farm.

Evidence for widespread infection of hepatitis E virus among wild rats in Japan

Sporadic cases of hepatitis E have been reported in industrialized countries, including Japan. The source of hepatitis E virus (HEV) in these patients is unknown, although zoonotic transmission has been suggested. To investigate whether or not rodents might be a reservoir of HEV, we conducted an epidemiological survey for the antibody to a recombinant capsid protein of HEV using serum samples from wild rodents in Japan. One hundred and fourteen of 362 (31.5%) Norway rats ( Rattus norvegicus) and 12 of 90 (13.3%) black rats ( Rattus rattus) were positive for anti-HEV IgG. In contrast, all of the sera from 55 mice were negative for anti-HEV IgG. The rate of antibody positivity increased with weight among Norway rats. Seropositive rats were found in all five districts surveyed in this study, but the prevalence of anti-HEV IgG in wild rats differed among these prefectures. Despite the fact that Japan is a non-endemic country of hepatitis E, widespread infection of HEV was observed among wild rats in Japan. Our results suggested that HEV or a closely related virus is circulating among wild rats in Japan.

Persistent infection in Neotoma fuscipes (Muridae: Sigmodontinae) with Ehrlichia phagocytophila sensu lato.

Dusky-footed wood rats (Neotoma fuscipes Baird) and two species of Peromyscus mice (P. maniculatus Wagner and P. truei Shufeldt) were collected over a 16-month period from three sites in Sonoma County, California. Blood was collected from 93 wood rats and 177 mice and serum or plasma was tested for seroreactivity with Ehrlichia phagocytophila sensu lato (also known as the human granulocytic ehrlichiosis agent). Thirty-five (37.6%) wood rats and 15 (8.5%) mice were seropositive. Positive Neotoma serology by site ranged from 9.4% to 62.1%. Polymerase chain reaction (PCR) testing for the Ehrlichia groESL heat shock operon was performed on all the seropositive and selected seronegative wood rats; 24 (68.6%) seropositive animals were PCR positive. Two seroconversions and no seroreversions were detected among 18 of the seropositive wood rats that were recaptured and tested multiple times (range = 2-6). Fourteen (77.8%) of the 18 were also PCR positive with six of these positive at every testing point (range = 2-6). One wood rat remained serologically and PCR positive in six specimens collected over a 14-month period. One male of 84 questing adult Ixodes pacificus Cooley & Kohls collected was PCR-positive for E. phagocytophila. Borrelia burgdorferi, the agent of Lyme disease, was cultured from ear punch biopsies from six of seven E. phagocytophila seropositive and one of four seronegative wood rats.

Dusky-footed wood rats (Neotoma fuscipes) as reservoirs of granulocytic Ehrlichiae (Rickettsiales: Ehrlichieae) in northern California.

Dusky-footed wood rats (Neotoma fuscipes) and Peromyscus sp. mice (P. maniculatus and P. truei) were collected from one site in Placer County, one site in Santa Cruz County, and two sites in Sonoma County in northern California. Serum or plasma samples from 260 rodents were tested for antibodies to the agent of human granulocytic ehrlichiosis. Of these, samples from 25 wood rats (34% of those tested) and 10 (8%) Peromyscus sp. mice were found to be seropositive, but only those from one site. PCR assays targeting the groESL heat shock operon were conducted on all seropositive specimens and a subset of seronegative blood specimens. Ehrlichial DNA was identified in 17 (68%) of the 25 seropositive wood rat blood samples and in 1 of the 10 (10%) Peromyscus sp. specimens. None of 40 seronegative blood samples was PCR positive. Both seropositive and PCR-positive animals were collected during each trapping period. One male tick out of 84 Ixodes pacificus adults collected was PCR positive; samples of Dermacentor occidentalis nymphs and adults were negative. Nucleotide sequences of amplicons from three wood rat blood specimens and from the single PCR-positive tick differed by one and two bases, respectively, from a sequence previously obtained from Ehrlichia equi. At one site in Sonoma County, wood rats had a concurrent high prevalence of seropositivity and PCR positivity, while other sigmodontine rodents collected at the site were only occasionally infected. We suggest that dusky-footed wood rats serve as reservoirs of granulocytic ehrlichial agents in certain areas of northern California. The tick species involved in the transmission of granulocytic ehrlichiae among wood rats remains unknown.

Black Creek Canal Virus infection in Sigmodon hispidus in southern Florida.

A total of 1,500 small mammals were collected and tested for antibodies cross-reactive to Sin Nombre virus (Hantavirus: Bunyaviridae) at 89 sites in a 1,600 km2 study area of southern Florida. More than 95% of the 123 seropositive animals were cotton rats (Sigmodon hispidus), suggesting infection by Black Creek Canal Virus, although seroreactive Rattus rattus (5 of 294) and Peromyscus gossypinus (1 of 39) also were captured. Crude seroprevalence in S. hispidus was 11%. Seroprevalence increased with body size and was more common in male (18%; n=451) than in female (6%; n=593) cotton rats. Infection within S. hispidus populations was widespread throughout the study area. Prevalence ranged from 0% to 60% at sites where more than five cotton rats were sampled but was not only a function of sample size. Sites with seropositive cotton rats were geographically clustered compared with sites with no seropositive cotton rats. Clustering was not due to the spatial distribution of sites with few animals, season of collection, or sex bias of animals captured at these sites. However, sites with no seropositive animals had an excess of animals in the intermediate size class (60-99 g) and a deficit of the largest and smallest animals. These data suggest that population structure within the habitat mosaic may play a significant role in the spatial distribution of hantavirus infection in local populations of reservoir species.

A 17-Mer self-peptide of acetylcholine receptor binds to B cell MHC class II, activates helper T cells, and stimulates autoantibody production and electrophysiologic signs of myasthenia gravis.

We have identified in an extracellular segment of the alpha1 subunit of nicotinic acetylcholine receptor (AChR) of homologous muscle a 17-residue autoantigen that, without conjugation to a carrier, activates Th lymphocytes and induces production of autoantibodies that cause electrophysiologic signs of experimental autoimmune myasthenia gravis. A panel of overlapping synthetic peptides revealed two T cell epitopes, one encompassed by residues 121-136 and the other by 129-145. Residues 129 (glutamic acid) and 130 (isoleucine) were implicated in a pathogenic B cell epitope. Peptide 129-145 (Glu-Ile-Ile-Val-Thr-His-Phe-Pro-Phe-Asp-Glu-Gln-Asn-Cys-Ser-Met-Lys, a conserved sequence in rat and human AChR) induced autoantibody production in 76% of rats. All seropositive rats had evidence of experimental autoimmune myasthenia gravis; five of five tested had electrophysiologic signs, and all had loss of immunochemically measured autologous muscle AChR. Analogues of 129-145, with single residues substituted by alanine, revealed phenylalanine 135, phenylalanine 137, and glutamic acid 139 as most important determinants of Ag/MHC-II/TCR interactions; phenylalanine 137 is critical for T cell activation. B cells were the major MHC-II-positive cell type to which the self-peptide 129-145 bound in a population of nonimmune splenic cells. More efficient processing and presentation of the Th cell epitope by an expanded population of immune B cells selected by specifically binding another epitope of the same peptide would greatly amplify the production of autoantibodies. Peptide autoantigens of this type could plausibly perpetuate the autoantibody response in myasthenia gravis, and are a rational target for strategies aimed at Ag-specific therapeutic intervention.

Isolation of black creek canal virus, a new hantavirus from Sigmodon hispidus in Florida.

Numerous rodents were trapped for serologic and virologic studies following the identification of a hantavirus pulmonary syndrome (HPS) case in Dade County, Florida. Cotton rats (Sigmodon hispidus) were the most frequently capture rodent and displayed the highest seroprevalence to a variety of hantavirus antigens. Hantavirus genome RNA was detected in all the seropositive cotton rats tested, using a reverse transcriptase-polymerase chain reaction (RT-PCR) assay. A virus was isolated from tissues of two seropositive cotton rats by cultivation of lung and spleen homogenates on Vero E6 cells. Nucleotide sequence information obtained by direct RT-PCR and the serologic relationships of this virus with the other hantaviruses indicate that this virus, Black Creek Canal virus, represents a new hantavirus distinct from the previously known serotypes.

A rat model of HTLV-I infection: development of chronic progressive myeloneuropathy in seropositive WKAH rats and related apoptosis

A rat model of HTLV-I infection: development of chronic progressive myeloneuropathy in seropositive WKAH rats and related apoptosis