Search PubMed⌕ Search

Biomedical subjects

C B Cropp

Publications and source records attributed to C B Cropp.

At least 37 records · Page 2Linked to original sources
PubMed1988

Dengue 2 virus envelope protein expressed by a recombinant vaccinia virus fails to protect monkeys against dengue.

A cDNA copy of the dengue (DEN) 2 virus genome region encoding the virion capsid, membrane and envelope structural proteins has been inserted into vaccinia virus (VV) DNA under the control of its 11K late promoter. The DEN-2 envelope protein was expressed and processed in cells infected with the VV recombinant (VV/D2S). No DEN-2 virus antibody response was detected in mice, hamsters or monkeys vaccinated with VV/D2S. Furthermore, a viraemia was observed in recombinant-vaccinated monkeys after challenge with infectious DEN-2 virus.

Animals↗
PubMed1988

[IFE: a new African orbivirus isolated from Eidolon helvum bats captured in Nigeria, Cameroon and the Central African Republic].

Eight viral isolates were recovered from Eidolon helvum bats collected in Nigeria and Cameroon in 1971 and from the Central African Republic in 1974. Subsequent studies showed that the agents from the three countries were similar and were strains of a new virus of the Orbivirus genus, family Reoviridae. This new virus was characterized with respect to its sensitivity to lipid solvents and to pH, its relative size and morphology by electron microscopy, its effect on mice experimentally infected by various routes, the histopathology found in infected mice, and its antigenic relationship or lack of a relationship to other known orbiviruses.

Animals↗
PubMed1988

Effect of human gamma interferon on yellow fever virus infection.

We studied yellow fever virus infection in two species of monkey: Saimiri sciureus (squirrel monkeys) and Macaca mulatta (rhesus monkeys). Human gamma interferon was administered intravenously in five equal doses, one was given 24 hr before infection followed by four doses 24 hr apart. Interferon reduced the levels and duration of viremia and the severity of hepatitis in squirrel monkeys. Interferon prolonged survival time and delayed the appearance of viremia and hepatitis in infected rhesus monkeys, but it did not change overall mortality.

Alanine Transaminase↗
PubMed1987

Arbovirus isolations from mosquitoes collected during and after the 1982-1983 epizootic of western equine encephalitis in Argentina.

Mosquitoes were collected in Santa Fe and Rio Negro provinces, Argentina, in 1982-1983 during a western equine encephalitis (WEE) epizootic. Totals of 153,084 mosquitoes from Santa Fe Province and 484 from Rio Negro Province were tested for virus in 2,351 pools. Seventeen virus strains were isolated, all from Santa Fe collections, as follows: 4 WEE, 6 Venezuelan equine encephalitis, 1 St. Louis encephalitis, 2 Antequera, 1 Maguari, 1 Melao, 1 new vesiculovirus (Calchaqui), and 1 Gamboa. The WEE virus isolates were from Aedes albifasciatus, Anopheles albitarsis, Mansonia species, and Psorophora pallescens. Collections during the spring and summer (1983-1984) following the epizootic yielded 49,707 mosquitoes from Santa Fe, 15,961 from Rio Negro, and 2,019 from Chubut provinces. Twenty-two virus strains were isolated, all from Santa Fe mosquitoes, as follows: 3 strains of SLE virus and 19 strains of Turlock (TUR) virus. All but one of the TUR virus isolates appear to have come from mosquitoes that engorged on a viremic chicken following entry into a bait trap. The vector relationships of each virus isolated during and after the WEE epizootic are discussed.

Aedes↗
PubMed1987

A newly recognized vesiculovirus, Calchaqui virus, and subtypes of Melao and Maguari viruses from Argentina, with serologic evidence for infections of humans and horses.

In 1983, 17 virus strains were isolated from mosquitoes collected during an outbreak of western equine encephalitis in Santa Fe Province, Argentina. Strains of western equine encephalitis, Venezuelan equine encephalitis, St. Louis encephalitis, and Antequera viruses were isolated, as were several bunyaviruses of the California and Bunyamwera serogroups and a new vesiculovirus. Complement fixation and neutralization tests were used to identify the California serogroup virus as a subtype of Melao virus, the Bunyamwera serogroup virus as a subtype of both Maguari and Playas viruses, and the vesiculovirus as a newly recognized agent for which the name Calchaqui virus is proposed. A limited serosurvey of horses and humans in Santa Fe Province and horses from the adjacent Santiago del Estero Province was performed to determine the prevalence of neutralizing antibody to the subtypes of Melao and Maguari viruses and to Calchaqui virus. The high prevalence of antibodies to these three agents indicates the need for further studies of their disease potential in horses, because they are closely related to several other viruses that are known equine pathogens.

Animals↗
PubMed1986

Sensitive and specific monoclonal immunoassay for detecting yellow fever virus in laboratory and clinical specimens.

A solid-phase radioimmunoassay (RIA) was developed for the detection of yellow fever (YF) virus in infected cell culture supernatant fluid and clinical samples. The test employed a flavivirus group-reactive monoclonal antibody attached to a polystyrene bead support and a radiolabeled type-specific antibody probe in a simultaneous sandwich RIA format. Optimal assay conditions specified a 16-h incubation at high temperature (45 degrees C). Monoclonal antibody to tetanus toxoid was added to the radiolabeled probe to inhibit nonspecific binding. The sensitivity of the assay for cell culture-propagated virus was 2.0 log10 50% mosquito infectious doses per 100 microliters or 100 pg of gradient-purified virion protein per 100 microliters. Specificity, assessed with human sera from 512 patients with liver diseases other than YF, including acute viral hepatitis, showed a false-positive rate of 0.0 to 0.6%. Sera from experimentally infected rhesus macaques containing greater than 3.0 log10 units/100 microliter of YF virus were positive by RIA. Sera and liver tissue from human patients were found to be positive.

Animals↗
PubMed1985

LeDantec virus: identification as a rhabdovirus associated with human infection and formation of a new serogroup.

LeDantec virus, originally recovered in 1965 from a patient with a febrile illness in Senegal, was observed by thin section electron microscopy to be bullet-shaped, representative of members of the rhabdovirus group, with mean dimensions of 164 X 78 nm. Particles were observed budding from the plasma membrane and moderate numbers accumulated in the intercellular spaces. In three mammalian cell lines, LeDantec virus was rapidly cytopathic and replicated to moderately high titres. In complement fixation tests with other known rhabdoviruses, LeDantec was found to be related to Keuraliba virus, a previously ungrouped agent isolated from rodents in Senegal in 1968. We propose the formation of a new LeDantec serogroup comprising these two viruses.

Animals↗
PubMed1985

Arbovirus investigations in Argentina, 1977-1980. II. Arthropod collections and virus isolations from Argentine mosquitoes.

Prospective surveys for arboviruses were carried out in Santa Fe, Corrientes, and Chaco provinces, Argentina, aperiodically during 1977-1980. A total of 313,233 mosquitoes and 598 biting flies other than mosquitoes were collected and tested for virus in 5,197 and 45 pools, respectively. Forty virus strains were isolated, all from mosquitoes, as follows: Santa Fe Province: 4 Gamboa group viruses from Aedeomyia squamipennis, 1 strain each of St. Louis encephalitis virus from Culex pipiens quinquefasciatus and Culex (Culex) spp.; Corrientes Province: a single strain of a newly discovered Anopheles A serogroup virus, Las Maloyas, from Anopheles albitarsis; and Chaco Province: 4 Gamboa group viruses from Ad. squamipennis, 6 strains of new Bunyaviridae (1 Antequera, 1 Barranqueras, and 4 Resistencia) from Culex (Melanoconion) delpontei, 3 strains of a new subtype of western equine encephalitis virus and 1 strain of Para virus from the Cx. (Mel.) ocossa group, 12 strains of a newly discovered subtype (VI) of the Venezuelan equine encephalitis complex from Cx. (Mel.) delpontei, and 1 strain each from Ad. squamipennis, Aedes scapularis, Ae. spp., Cx. (Cux.) spp., Cx. (Mel.) ocossa group, Mansonia spp., and Psorophora spp. Bloodmeals from 265 engorged mosquitoes were identified by precipitin test. These data, coupled with data on engorgement rates for 25,995 mosquitoes from bait collections, provide information on the host feeding patterns of several mosquito species. This information is discussed, along with data on relative abundance of mosquito species, within the context of the vector relationships of the species from which viruses were isolated. The association of Cx. (Mel.) delpontei with 18 strains of 4 different viruses in Chaco Province, plus its catholic feeding habits, clearly indicate for the first time the importance of this species as an arbovirus vector.

Aedes↗
PubMed1985

Arbovirus investigations in Argentina, 1977-1980. III. Identification and characterization of viruses isolated, including new subtypes of western and Venezuelan equine encephalitis viruses and four new bunyaviruses (Las Maloyas, Resistencia, Barranqueras, and Antequera).

Forty viruses isolated from mosquitoes between 1977 and 1980 in Argentina have been identified and characterized. Nineteen strains of VEE virus, identical by neutralization (N) tests, were shown by hemagglutination-inhibition tests with anti-E2 glycoprotein sera to represent a new subtype VI of the VEE complex. RNA oligonucleotide fingerprints of this virus were distinct from subtype I viruses. The virus was not lethal for English short-haired guinea pigs, indicating that it is probably not equine-virulent. Three strains of a member of the WEE virus complex were shown to differ by N tests in 1 direction from prototype WEE virus. The new WEE subtype was also found to be distinct by RNA oligonucleotide mapping. Its vector relationships indicate that it is an enzootic virus, and it has not been associated with equine disease. A new member of the Anopheles A serogroup was identified, shown to be most closely related to Lukuni and Col An 57389 viruses, and given the name Las Maloyas virus. A strain of Para virus (Bunyaviridae, Bunyavirus) was identified. Six isolates, representing 3 new viruses morphologically resembling bunyaviruses are described; the names Antequera, Barranqueras, and Resistencia are proposed for these agents, which were all isolated from Culex (Melanoconion) delpontei in Chaco Province. No serologic relationships between these viruses and other bunyaviruses were found. Since they are antigenically interrelated, they form a new (Antequera) serogroup. Eight Gamboa serogroup viruses and 2 strains of St. Louis encephalitis virus were also identified.

Aedes↗
PubMed1985

Arbovirus investigations in Argentina, 1977-1980. IV. Serologic surveys and sentinel equine program.

Serologic surveys of wild and domestic birds, wild mammals, and horses were conducted during arbovirus field studies in Argentina from 1977 through 1980, a non-epizootic interval. The prevalence of neutralizing antibodies to eastern equine encephalitis (EEE) was consistently higher than to western equine encephalitis (WEE) virus in all species and all areas. The presence of antibodies in short-lived avian species and in young unvaccinated horses and the demonstration of seroconversions in horses during the period, indicated that these viruses are either enzootic in, or annually reintroduced into, Argentina. Antibodies to AG80-646, a new subtype of WEE virus isolated in the subtropical north (Chaco Province) from Culex (Melanoconion) mosquitoes, were found in horses and rodents in that region. Antibodies to the TC-83 strain of Venezuelan equine encephalitis (VEE) virus were found in all areas studied. The presence of antibodies in some horses was probably related to vaccination, but the demonstration of seroconversions in sentinel horses and of antibodies in birds and wild mammals indicates active transmission of VEE virus. In 1980 a new enzootic subtype of VEE virus (AG80-663) was isolated from mosquitoes in Chaco; neutralizing antibodies to this virus were prevalent in horses and rodents in this area. Infections with Aura and Una viruses were most common in the subtropical northern provinces. Infection with St. Louis encephalitis was prevalent and widespread, and birds, principally passerine and columbiform species, appear to be the principal hosts. An interesting and unexplained finding was the absence of arbovirus antibodies, in particular SLE antibodies in house sparrows (Passer domesticus). Antibody prevalences in horses exceeded 50% in all areas, and 12% of horses surveyed in Santa Fe Province developed antibody in a 17-month period. Antibodies to other flaviviruses were rare. A high prevalence of immunity to Maguari virus was found in horses; this agent is considered to be a potential equine pathogen. Antibodies to 2 new viruses, Barranqueras and Resistencia, which had been isolated from Cx. (Melanoconion) in Chaco Province, were found in rodents there. Immunity to Gamboa group viruses was prevalent, and birds were implicated as principal hosts.

Alphavirus↗
PubMed1984

Yellow fever monoclonal antibodies: type-specific and cross-reactive determinants identified by immunofluorescence.

Monoclonal antibodies directed against the envelope glycoprotein and the NV3 non-structural viral protein of yellow fever (YF) were tested by the indirect fluorescent antibody technique against a variety of YF virus strains and heterologous flaviviruses. Monoclonal antibodies directed against the envelope glycoprotein exhibited YF strain-specificity, YF type-specificity, broad group cross-reactivity, or limited subgroup reactivity (YF + Banzi or YF + Koutango + Zika + Usutu + Uganda S). Monoclonal antibodies directed against NV3 reacted either with YF + Koutango or with YF + Banzi. These findings generally correlated with the results of biological tests reported previously. Monoclonal antibodies that were type-specific to YF will be useful for the rapid specific identification of YF virus isolates and are available from the Centers for Disease Control on request.

Animals↗
PubMed1983

Identification of new Guama and Group C serogroup bunyaviruses and an ungrouped virus from Southern Brazil.

From 1975 to 1978, 36 viruses were recovered from humans, bats, birds, sentinel mice and hamsters, and from mosquitoes collected in Coastal Brazil in the state of São Paulo. Identifications of 22 of these 36 viruses have been reported. Six of the remaining 14 isolates were shown to be Guama serogroup bunyaviruses. Two of these six were strains of a newly recognized virus for which the name Cananeia virus is proposed; another is a second newly recognized Guama serogroup virus for which the name Itimirim virus is proposed; a fourth is a strain of Bertioga virus and the other two are strains of Guaratuba virus. Before these studies Guaratuba virus was considered an ungrouped bunyavirus, but cross testing by complement-fixation demonstrated that this virus, and Mirim virus as well, should be considered members of the Guama serogroup. Another six viruses were shown to be strains of a single, newly recognized Group C bunyavirus for which the name Bruconha virus is proposed. Two strains of a single virus were shown by electron microscopy to belong to the family Bunyaviridae, but serologic relationships with other members of this family of viruses were not found; the name Enseada virus is proposed for this newly recognized agent.

Animals↗
PubMed1983

Mode of entry of a neurotropic arbovirus into the central nervous system. Reinvestigation of an old controversy.

The mechanism by which neurotropic arboviruses gain access to the central nervous system remains uncertain, although it is generally assumed that viremic infection results in growth across or passive diffusion through brain capillaries. In contrast to the natural reservoir hosts of these arboviruses, clinical hosts (e.g., horses, humans) have viremias of very brief duration and low magnitude. We investigated the question of neuroinvasion in 5- to 6-week-old Syrian hamsters infected with St. Louis encephalitis virus (strain TBH-28). This model shares with the human disease low or undetectable viremia and many clinical and pathoanatomical features. The mortality rate after intraperitoneal inoculation of a moderate viral dose was 88%. No viremia was detectable by a sensitive assay in 31% of the animals. In the remaining hamsters, the mean peak viremia was 1.0 log10 plaque-forming units/0.05 ml and the mean duration 1 to 2 days. There was no correlation between viremia and outcome of infection, length of incubation period, or brain virus titer. Tissue infectivity studies showed a rise in titer in the olfactory neuroepithelium on day 4 postinoculation, then in the olfactory bulbs (day 5 postinoculation), and finally in the remainder of the brain (day 6 postinoculation). Specific immunofluorescence was demonstrated in the bipolar neurons of the olfactory epithelium, their dendrites, and in axon bundles of the olfactory nerves in the submucosa. By electron microscopy, virus particles and associated tubular structures were demonstrated within dendrites, perikarya, and axons of olfactory neurons, and to a lesser extent in macrophages and Bowman's gland cells in the lamina propria. In cells of Bowman's glands large numbers of virions were sequestered within secretory granules. Virus was recovered from nasal washings on day 4 postinoculation. Similar findings were obtained in weanling mice inoculated intraperitoneally with another (mouse-virulent) St. Louis encephalitis viral strain (77V-12908). These data taken together indicate that the olfactory pathway is the principal route of viral entry into the central nervous system. After peripheral inoculation a low-level viremia results in infection of highly susceptible cells in the olfactory neuroepithelium, allowing centripetal axonal transport of virus to the olfactory bulb, whence spread is unimpeded throughout the neuropil of the central nervous system. Infection of Bowman's gland cells in the olfactory mucosa and shedding of virus in nasal mucus may be an adaptation for nonarthropod-borne transmission, a feature of many flaviviruses.

Animals↗
PubMed1981

Indirect fluorescent antibody test for the diagnosis of yellow fever.

The indirect fluorescent antibody (FA) test was evaluated for the serodiagnosis of yellow fever (YF) cases and for detection of antibodies after 17D YF vaccination. Results were compared with those of standard serological tests, reactions with heterologous flaviviral antigens were determined, and both IgM and IgG antibodies were measured. Spot slides of infected Vero cells were used as antigen substrate. In cases of primary YF infection, the FA test for IgG antibodies provided clear diagnostic results. Indirect FA tests with anti-IgG were more sensitive than the complement-fixation (CF) test and showed specificity comparable to the CF and neutralization (N) test. Cases of YF infection superimposed upon pre-existing heterologous flaviviral immunity developed broadly-crossreactive IgG antibodies. IgM antibodies were highly specific in cases of both primary infection and superinfection but were not consistently present. Most individuals without previous flaviviral exposure who received 17D vaccine failed to develop detectable antibodies by the indirect FA test; of those with pre-existing immunity, 79% developed IgG antibodies. The indirect FA test provides a simple, rapid diagnostic procedure which should be especially useful in one-site epidemiological investigations of YF outbreaks.

Antibodies, Viral↗
PubMed1981

Arbovirus infections among laboratory personnel in Ibadan, Nigeria.

Laboratory-acquired infections encountered between 1963 and 1977 among personnel of the Virus Research Laboratory, Ibadan, Nigeria, are reported. Two cases of chikungunya infection occurred and one each with Dugbe, Wesselsbron, and dengue viruses. In each case, virus was isolated or development of antibody demonstrated. Among virus and two each to chikungunya and Rift Valley fever viruses, without experiencing any clinically recognized disease.

Adult↗