Dose-Response Model for Lassa Virus

This article develops dose-response models for Lassa fever virus using data sets found in the open literature. Dose-response data were drawn from two studies in which guinea pigs were given subcutaneous and aerosol exposure to Lassa virus. In one study, six groups of inbred guinea pigs were inoculated subcutaneously with doses of Lassa virus and five groups of out-bred guinea pigs were similarly treated. We found that the out-bred subcutaneously exposed guinea pig did not exhibit a dose-dependent trend in response. The inbred guinea pigs data were best fit by an exponential dose-response model. In a second study, four groups of out-bred guinea pigs were exposed to doses of Lassa virus via the aerosol route. In that study, aerosol diameter was less than 4.5 μ m and both mortality and morbidity were used as endpoints. The log-probit dose-response model provided a somewhat better fit than the Beta-Poisson model for data with mortality as the endpoint, but the Beta-Poisson is considered the best fit model because it can be derived using biological considerations. Morbidity data were best fit with an exponential dose-response model.     

Enhanced multiplication and transmission of Streptococcus pneumoniae in guinea pigs by Sendai virus infection

It was demonstrated that the transmission S. pneumoniae in guinea pigs was remarkably promoted by the combined infection with Sendai virus in the following experiments. When guinea pigs infected with S. pneumoniae alone (infector) were cagemated with non-treated guinea pigs (contact) for 2 and 4 weeks, only 2 of 30 contacts were infected with the organism. On the contrary, when the contact guinea pigs were infected with Sendai virus and immediately cage-mated with the infectors, the pneumococcal infection occurred in 25 of 30 contacts during 2 to 4 weeks period. In the experiment in which 30 non-treated contacts were cage-mated with pneumococcal infectors for 4 weeks and then infected with Sendai virus, no pneumococcal infection was demonstrated in the contacts, suggesting no presence of latent infection of the organism in the contact guinea pigs. Twenty-five of 30 contacts suffered from pneumococcal infection when they were exposed to Sendai virus for 2 weeks and then cage-mated with infectors. The multiplication of S. pneumoniae in the respiratory tract of the guinea pigs was remarkably enhanced by combined infection with Sendai virus. Namely, a 1000-fold increase in the number of organism resulted in the guinea pigs suffered from combined infection as compared with that in the animals received pneumococcal single infection.     

Effect of immunosuppression on experimental Argentine hemorrhagic fever in guinea pigs.

Immunosuppression with cyclosporin A or cyclophosphamide had no apparent effect on the disease course of guinea pigs infected with a virulent strain of Junin virus. Immunosuppression of guinea pigs infected with an attenuated strain of Junin virus led to fulminating Argentine hemorrhagic fever. All immunosuppressed infected animals died. Virus distribution patterns in target organs, as determined by plaque assay and fluorescent antibody procedures, were similar to those from non-immunosuppressed animals infected with a virulent strain. Histopathological lesions in immunosuppressed guinea pigs infected with an attenuated strain of virus were similar to those in non-immunosuppressed guinea pigs infected with a virulent strain. Histological changes attributable to the immunosuppressive drug(s) were regularly observed. Immunosuppressed animals infected with attenuated Junin virus and non-immunosuppressed animals infected with virulent virus failed to develop antibody or responded at a minimal level. Virus-specific cytotoxic spleen cell activity, previously shown to be antibody dependent, failed to develop in the same animals. The presence of a competent immune response, probably serum antibody, determined whether Argentine hemorrhagic fever infection of the guinea pig was lethal or whether recovery ensued; no evidence for harmful effects of the immune response was obtained.     

Characterization of a novel parainfluenza virus,caviid parainfluenza virus 3, from laboratory guinea pigs (Cavia porcellus)

A novel Respirovirus was isolated from nasopharyngeal swab specimens from clinically normal laboratory guinea pigs, and was characterized and named caviid parainfluenza virus 3 (CavPIV-3). The CavPIV-3 is enveloped, is 100 to 300 nm in diameter, and has a characteristic 15-nm-diameter chevron-shaped virus ribonucleocapsid protein. Sequence analysis of the fusion glycoprotein of CavPIV-3 revealed it to be 94% identical to human and guinea pig parainfluenza 3 (PIV-3) viruses and 80% identical to bovine PIV-3. To determine whether CavPIV-3 causes clinical disease in laboratory guinea pigs and to compare the serologic response of guinea pigs to CavPIV-3 and to other paramyxoviruses, an infection study was performed, in which groups of guinea pigs were inoculated with CavPIV-3, Sendai virus, simian virus 5 (SV-5), murine pneumonia virus (PVM), or bovine PIV-3 virus. During the course of the study, guinea pigs were maintained in an infectious disease suite, housed in Micro-Isolator cages, and were only manipulated under a laminar flow hood. Clinical signs of disease were not observed in any of the paramyxovirus-inoculated guinea pigs during the eight-week course of the study, and histologic signs of disease were not evident at necropsy eight weeks after inoculation. Guinea pigs inoculated with CavPIV-3, Sendai virus, PVM, and bovine PIV-3 developed robust homologous or heterologous serologic responses. In contrast, guinea pigs inoculated with SV-5 developed modest or equivocal serologic responses, as assessed by use of an enzyme-linked immunosorbent assay. Further, use of the SV-5 enzyme-linked immunosorbent assay resulted in the highest degree of non-specific reactivity among all of the paramyxovirus assays. In summary, CavPIV-3 is a novel guinea pig Respirovirus that subclinically infects laboratory guinea pigs, resulting in a robust serologic response, but no observed clinical or histologic disease. The CavPIV-3 fusion glycoprotein gene sequence is available from GenBank as accession No. AF394241, and the CavPIV-3 virus is available from the American Type Culture Collection as accession No. DR-1547.     

Fetal thermal dose considerations during the obstetrician's watch: Implications for the pediatrician's observations

There are a number of seemingly "usual" thermal episodes during pregnancy for which it is relatively easy to determine a rudimentary aspect of thermal dose; these episodes include fever, labor, labor plus epidural, and the normally-occurring 0.5 degrees C temperature elevation above maternal core temperature of the fetus during the entirety of the third trimester. Complications can involve, for instance, fever during the third trimester. We consider the thermal doses of five different but "usual" or "normal" hyperthermic episodes during human pregnancy and compare those doses with the thermal doses involved with both single and cohort exposures of pregnant guinea pigs throughout their gestational period. The end-point studied in the guinea pigs was microencephaly. In nine of the 10 comparisons (human fetal thermal dose vs. guinea pig fetal thermal dose) the human dose is substantially larger than that of the guinea pig thermal dose, which was substantially teratogenic. This situation is essentially the inverse of the type of information contained in the Physician's Desk Reference (PDR) on drugs, in which it is not unusual to discern that at high drug levels there may be teratogenic effects in laboratory animals, but such effects were not observed at "clinical" drug levels in animals or subsequent clinical trials. With hyperthermic events, however, it appears that the teratogenically-effective thermal dose levels associated with animal testing are quite low relative to those thermal doses associated with relatively "normal" obstetric observations during a pregnancy.     

The effect of urine from castrated male or female guinea pigs and rats on the estrous cycle of guinea pigs and rats, respectively]

A 24-hour reduced cycle duration was observed in 5-day cyclic female rats exposed to the odor of urine from male or female castrated rats. A decrease in the duration of the period of vaginal closure, ranging from 2 to 5 days, was observed in female guinea pigs exposed to the odor of urine from male or female castrated guinea pigs. The pheromonal activity of urine in both species was concluded to be no dependent upon the gonadal function.     

A live attenuated vaccine for Lassa fever made by reassortment of Lassa and Mopeia viruses

Lassa virus (LASV) and Mopeia virus (MOPV) are closely related Old World arenaviruses that can exchange genomic segments (reassort) during coinfection. Clone ML29, selected from a library of MOPV/LASV (MOP/LAS) reassortants, encodes the major antigens (nucleocapsid and glycoprotein) of LASV and the RNA polymerase and zinc-binding protein of MOPV. Replication of ML29 was attenuated in guinea pigs and nonhuman primates. In murine adoptive-transfer experiments, as little as 150 PFU of ML29 induced protective cell-mediated immunity. All strain 13 guinea pigs vaccinated with clone ML29 survived at least 70 days after LASV challenge without either disease signs or histological lesions. Rhesus macaques inoculated with clone ML29 developed primary virus-specific T cells capable of secreting gamma interferon in response to homologous MOP/LAS and heterologous MOPV and lymphocytic choriomeningitis virus. Detailed examination of two rhesus macaques infected with this MOPV/LAS reassortant revealed no histological lesions or disease signs. Thus, ML29 is a promising attenuated vaccine candidate for Lassa fever.     

The placenta as a site of cytomegalovirus infection in guinea pigs.

The development of cytomegalovirus (CMV) infection in the placenta was studied in Hartley guinea pigs inoculated at midgestation, and its role in determining the outcome of fetal CMV infection was assessed. A hematogenous spread of CMV from the mother to the placenta occurred early during the course of the infection. However, the virus remained present in placental tissues long after CMV had been cleared from maternal blood (i.e., 3 and 4 weeks postinoculation). At that time, the virus was able to replicate in placental tissues in the presence of specific maternal antibodies. Viral nucleocapsids were seen within nuclei of trophoblastic cells, and virions were present surrounding infected cells. In addition, typical CMV-induced histopathological lesions bearing CMV antigens were consistently localized at the transitional zone between the capillarized labyrinth and the noncapillarized interlobium. Whenever CMV infection of the fetus occurred, virus was isolated from the associated placenta. Among placental-fetal units with CMV-infected placentas, only 27% of the fetuses were found to be infected. In addition, there was a delay in the establishment of the infection in the fetus in relation to the placenta, although frequencies of virus isolation in placental and fetal tissues peaked at 3 weeks after CMV inoculation. These results suggest that during primary CMV infection of pregnant guinea pigs, the placenta not only serves as a reservoir for CMV but also acts to limit transmission of the virus to the fetus.     

Selection of classical swine fever virus with enhanced pathogenicity reveals synergistic virulence determinants in E2 and NS4B

Classical swine fever virus (CSFV) is the causative agent of classical swine fever (CSF), a highly contagious disease of pigs. There are numerous CSFV strains that differ in virulence, resulting in clinical disease with different degrees of severity. Low-virulent and moderately virulent isolates cause a mild and often chronic disease, while highly virulent isolates cause an acute and mostly lethal hemorrhagic fever. The live attenuated vaccine strain GPE(-) was produced by multiple passages of the virulent ALD strain in cells of swine, bovine, and guinea pig origin. With the aim of identifying the determinants responsible for the attenuation, the GPE(-) vaccine virus was readapted to pigs by serial passages of infected tonsil homogenates until prolonged viremia and typical signs of CSF were observed. The GPE(-)/P-11 virus isolated from the tonsils after the 11th passage in vivo had acquired 3 amino acid substitutions in E2 (T830A) and NS4B (V2475A and A2563V) compared with the virus before passages. Experimental infection of pigs with the mutants reconstructed by reverse genetics confirmed that these amino acid substitutions were responsible for the acquisition of pathogenicity. Studies in vitro indicated that the substitution in E2 influenced virus spreading and that the changes in NS4B enhanced the viral RNA replication. In conclusion, the present study identified residues in E2 and NS4B of CSFV that can act synergistically to influence virus replication efficiency in vitro and pathogenicity in pigs.     

The red blood cells in growing guinea pigs. (Cavia cobaya). II. Communication: erythropoiesis and red blood cells in the postnatal development period

Bone-marrow smears of 175 guinea pigs aged 1-27 days and venous blood samples of 351 animals aged 1-25 days were prepared for cell counting. A significant increase of erythroblasts were found between life day 1 and 2; normoblasts increased in number synchronously with a decrease of erythroblasts after the 5th day. The percentage of the erythroid bone marrow increased from 10 to 14 during the developmental period. Beyond the perinatal period the red blood picture is characterized by the following changes: a decrease of erythrocyte count, hematocrit, hemoglobin, mean corpuscular volume, and mean corpuscular hemoglobin; a constant mean corpuscular hemoglobin concentration; an increase of the reticulocyte count. The decrease of the red cell count is compensated by a decreasing oxygen affinity attained by an important increase of 2,3-DPG. Nevertheless, the stimulus for a raising erythropoiesis remains constant which can be shown by the growing percentage of erythroid cells and reticulocytes. The difference between the human postnatal development and that of the guinea pig becomes obvious. Cell counts in dependence of body masses in postnatally growing guinea pigs, veil the perinatal finding of the increase in erythrocytes up to the 5th day and the decrease of the mean corpuscular volume after the 3rd day.     

Follicle selection in cyclic guinea pigs with active immunization against inhibin alpha-subunit

Experiments were conducted to elucidate the mechanisms of active immunization against inhibin on ovarian follicular development and selection in guinea pigs. Estrous cycle was synchronized in experimental guinea pigs by implanting progesterone containing tubes. Antibodies that bound 125I-labeled bovine inhibin were produced by all guinea pigs receiving the inhibin vaccine (recombinant ovine alpha-subunit in oil emulsion) without any effects on duration of the estrous cycle. Active immunization against inhibin increased the plasma concentrations of progesterone during the luteal phase and the plasma concentrations of estradiol but failed to increase the plasma concentration of follicle-stimulating hormone (FSH) during preovulatory period. The treatment also increased the number of corpora lutea (from 1.3+/-0.3 to 7.0+/-1.6 per each ovary), and preovulatory sized follicles (from 1.8+/-0.6 to 7.0+/-1.6 per each ovary), and follicles stained positively for inhibin alpha-subunit (from 2.3+/-0.5 to 6.3+/-1.3 per each ovary) significantly. The results indicate that active immunization against inhibin enhances ovulation rate by affecting the follicle selection and only dominant follicle can be stained for inhibin alpha-subunit in guinea pigs. This study is firstly to provide direct evidence that inhibins play important role in follicle selections in guinea pigs.     

Detection of Soluble Antigen and DNA of Trypanosoma cruzi in Urine Is Independent of Renal Injury in the Guinea Pig Model

The diagnosis of Chagas disease in humans is generally limited to the detection of specific antibodies. Detection of T. cruzi antigens in urine has been reported previously, but is not used in the diagnosis. In this study, soluble T. cruzi antigens and DNA were detected in urine samples and were associated with kidney injury and systemic detection of the parasite. We used 72 guinea pigs infected with T. cruzi Y strain and 18 non-infected guinea pigs. Blood, kidney, heart and urine samples were collected during the acute phase and chronic phase. Urine samples were concentrated by ultrafiltration. Antigens were detected by Western Blot using a polyclonal antibody against trypomastigote excretory-secretory antigen (TESA). T. cruzi DNA was detected by PCR using primers 121/122 and TcZ1/TcZ2. Levels of T. cruzi DNA in blood, heart and kidney were determined by quantitative PCR. T. cruzi antigens (75 kDa, 80 kDa, 120 kDa, 150 kDa) were detected in the acute phase (67.5%) and the chronic phase (45%). Parasite DNA in urine was detected only in the acute phase (45%). Kidney injury was characterized by high levels of proteinuria, kidney injury molecule-1 (KIM-1) and urea, and some histopathological changes such as inflammation, necrosis, fibrosis and scarce parasites. The detection of antigens and DNA in urine was associated with the presence of parasite DNA in blood and heart and with high levels of parasite DNA in blood, but not with the presence of parasite in kidney or kidney injury. These results suggest that the detection of T. cruzi in urine could be improved to be a valuable method for the diagnosis of Chagas disease, particularly in congenital Chagas disease and in immunocompromised patients.     

Thermoregulatory responses of guinea pigs with anteroventral third ventricle lesions

Guinea pigs with anteroventral third ventricle region (AV3V) lesions fail to develop fever and the associated rise in acute-phase plasma protein levels following systemic injections of lipopolysaccharide (LPS). Since endogenous pyrogen (EP) injected directly into the preoptic area of animals with AV3V lesions causes appropriate elevations in core temperature (Tco) and acute-phase plasma proteins levels, the blocked responses to LPS probably are not due to damage to the adjacent preoptic area. We proposed, therefore, that EP may pass from blood into brain in the AV3V, presumably through the organum vasculosum laminae terminalis. However, the possibility that a more generalized impairment due to damaged pathways within the AV3V could account for the observed effects was not examined. To investigate this possibility, guinea pigs were given AV3V lesions. Pending histological verification of the ablated sites, AV3V lesions were presumed to be placed correctly if the animals did not develop fever following LPS (Salmonella enteritidis, 2 micrograms/kg i.p., at ambient temperature (Ta) 22 degrees C); those failing to meet this criterion were designated as sham-operated. Two experiments were conducted. In the first, metabolic rates, Tco, and two skin temperatures (Tsk) were measured at Ta 12 degrees, 22 degrees, and 32 degrees C over an 8-month postlesion period during which failure to fever persisted; the data were collected during a 30-min period after thermal balance had been achieved at any given Ta. There were no differences in the variables measured between sham-operated and AV3V-lesioned animals at Ta 22 degrees C.(ABSTRACT TRUNCATED AT 250 WORDS)     

Experimental study on the possibility of treatment of some hemorrhagic fevers

After intracerebral challenge with 100 PFU of Lassa virus (strain Josiah), all infected mice (CBA/calac) died (control group). Production of pro-inflammatory cytokines (IL-1beta, TNF-alpha) significantly increased in the blood of these mice during the infection. For neutralization of increasing concentrations of these cytokines recombinant IL-1RA was used intraperitonealy at a dose 100 microg kg(-1), everyday, within 5 days from the third day after the challenge. Injections of IL-1RA decreased the concentration of IL-1beta and TNF-alpha and resulted in survival of all infected mice (treatment group). Marburg fever (strain Popp) caused in guinea pigs by 5 LD(50) of virus lead to the significant increase of TNF-alpha in the animal's blood and caused a lethal outcome (control group). Treatment of infected guinea pigs by IL-1RA or anti-TNF serum decreased the concentration of TNF-alpha and resulted in survival of half of the animals (treatment group). For the treatment recombinant IL-1RA was used at a dose 100 microg kg(-1), intramuscularly, everyday, within 6 days from the third day after the challenge or anti-TNF serum, intramuscularly 0.5 ml (2000 U ml(-1); 1 U of the antiserum neutralises 0.03 ng of TNF-alpha), everyday, within 6 days from the third day after the challenge.     

Complexity of chemical communication in mammals: urinary components mediating sex discrimination by male guinea pigs

Male guinea pigs are more attracted to urine from female guinea pigs than to urine from males. Separation of urine into fractions characterized by molecular weight and functionality through several different methods established that this discrimination and preference is based on a pattern of components which have widely different chemical character. The active compounds range from macromolecules (MW >10,000) to small, relatively volatile molecules. These studies establish a complexity in chemical signals that has not been previously documented for any other species.     

Tryptophan metabolism in animals with dermatitis. II) In guinea pigs

Tryptophan load in guinea pigs after induction of a photodermatitis from psoralen caused marked increase of urinary excretion of total metabolites "via kynurenine" in comparison with that obtained before dermatitis. Xanthurenic acid is the metabolite which showed the most increased levels in urine during dermatitis. This dermatitis from furocoumarin caused an alteration of tryptophan metabolism in guinea pigs as well as rats, but species differences in the excretion of metabolites after amino acid load are observed.     

非洲钝缘蜱感染Q热立克次体敏感度的测定

Q热立克次体以10^-1—10^-12不同稀释度,用血腔注射法感染非洲钝缘蜱,感染35天,取蜱血淋巴液,分别用Gimenez染色法及免疫荧光技术检查,在10^-1—10^-5的稀释度,两种方法检出率基本相似。10^-6以下各组,免疫荧光尚可检出少数阳性标本,而Gimcnez法则无阳性,前者总阳性率为48.28%,后者为40.68%。感染的蜱悬液接种豚鼠,12组动物血清做Q热补体结合试验全部阳性。动物发病情况如潜伏期长短、发烧天数等似与蜱内立克次体的含量有关。     

Identification of swine influenza A virus and Stenotrophomonas maltophilia co-infection in Chinese pigs

ABSTRACT: BACKGROUND: Influenza virus virulence can be exacerbated by bacterial co-infections. Swine influenza virus (SIV) infection together with some bacteria is found to enhance pathogenicity. METHODS: SIV-positive samples suspected of containing bacteria were used for bacterial isolation and identification. Antimicrobial susceptibility testing was performed by disc diffusion methods. To investigate the interaction of SIV and the bacteria in vitro, guinea pigs were used as mammalian hosts to determine the effect on viral susceptibility and transmissibility. Differences in viral titers between groups were compared using Student's t-test. RESULTS: During surveillance for SIV in China from 2006 to 2009, seven isolates (24.14%) of 29 influenza A viruses were co-isolated with Stenotrophomonas maltophilia from nasal and tracheal swab samples of pigs. Antimicrobial susceptibility testing showed that the bacteria possessed a high level of resistance towards clinically used antibiotics. To investigate the interaction between these two microorganisms in influencing viral susceptibility and transmission in humans, guinea pigs were used as an infection model. Animals were inoculated with SIV or S. maltophilia alone or co-infected with SIV and S. maltophilia. The results showed that although no transmission among guinea pigs was observed, virus--bacteria co-infections resulted in higher virus titers in nasal washes and trachea and a longer virus shedding period. CONCLUSIONS: This is the first report of influenza virus co-infection with S. maltophilia in the Chinese swine population. Increased replication of virus by co-infection with multidrug resistant bacteria might increase the infection rate of SIV in humans. The control of S. maltophilia in clinics will contribute to reducing the spread of SIV in pigs and humans.     

The fate of cyclamate in man and other species

1. (14)C-labelled cyclamate has been administered to guinea pigs, rabbits, rats and humans. When given orally to these species on a cyclamate-free diet, cyclamate is excreted unchanged. In guinea pigs some 65% of a single dose is excreted in the urine and 30% in the faeces, the corresponding values for rats being 40 and 50%, for man, 30-50% and 40-60%, and for rabbits, 90 and 5%, the excretion being over a period of 2-3 days. 2. Cyclamate appears to be readily absorbed by rabbits but less readily by guinea pigs, rats and humans. 3. If these animals, including man, are placed on a diet containing cyclamate they develop the ability to convert orally administered cyclamate into cyclohexylamine and consequently into the metabolites of the latter. The extent to which this ability develops is variable, the development occurring more readily in rats than in rabbits or guinea pigs. In three human subjects, one developed the ability quite markedly in 10 days whereas two others did not in 30 days. Removal of the cyclamate from the diet caused a diminution in the ability to convert cyclamate into the amine. 4. In rats that had developed the ability to metabolize orally administered cyclamate, intraperitoneally injected cyclamate was not metabolized and was excreted unchanged in the urine. The biliary excretion of injected cyclamate in rats was very small, i.e. about 0.3% of the dose. 5. The ability of animals to convert cyclamate into cyclohexylamine appears to depend upon a continuous intake of cyclamate and on some factor in the gastrointestinal tract, probably the gut flora.