Showing papers on "Viremia published in 1974"
TL;DR: In this model neutralizing antibody appears to play a critical role in recovery from potentially fatal encephalitis, and immune lymphoid cells may act primarily through production of antibody.
Abstract: Intraperitoneal inoculation of 106 LD50 of West Nile virus produces an inapparent infection in the central nervous system of the mouse; the infection is converted into lethal encephalitis by a single dose of cyclophosphamide (150 mg/kg) given 24 hr after infection. Cyclophosphamide-potentiated infection is characterized by suppressed response of neutralizing antibody, prolonged viremia, enhanced titers of virus in the brain, and concomitant histologic encephalitis; death occurs eight to 16 days after infection. A single intraperitoneal injection of immune serum given as late as six days after infection reduces mortality to 15%. A comparable reduction in mortality follows the transfer of 108 syngeneic splenocytes from mice immune to West Nile virus. However, these cells are effective only when given within two days after infection. In this model neutralizing antibody appears to play a critical role in recovery from potentially fatal encephalitis, and immune lymphoid cells may act primarily through production of antibody.
109 citations
TL;DR: The viruses of bluetongue and epizootic hemorrhagic disease produced cell associated viremias in white-tailed deer and antibodies failed to confer protection against challenge with virulent heterologous virus.
Abstract: The viruses of bluetongue and epizootic hemorrhagic disease produced cell associated viremias in white-tailed deer (Odocoileus Virginianus). Highest virus titers were associated with the erythrocytes. The titers of virus in the erythrocyte fraction of blood were consistently higher than those in the leukocyte fraction, although virus persisted in both fractions for approximately the same length of time. All detectable viremia disappeared within 6 to 8 days following the development of virus-specific neutralizing antibodies. These antibodies failed to confer protection against challenge with virulent heterologous virus, although the time of death was delayed 3 to 11 days in comparison with control deer.
32 citations
TL;DR: The hypothesis that enzootic VEE subtypes are less pathogenic than subtypes responsible for major epizootics is supported, because high titers of circulating virus were detected in the sera of all animals.
Abstract: Adult rhesus monkeys were infected with five subtypes of Venezuelan equine encephalitis (VEE) virus (IA, IB, IC, ID, and IE). The animals were studied clinically, and samples of serum were taken for determinations of viremia and antibody, leukocyte counts, and biochemical studies. Only monkeys inoculated with VEE subtype IA, IB, or IC developed fever and signs of illness, although high titers of circulating virus were detected in the sera of all animals. Viremia appeared on day 1 after inoculation and disappeared by days 4-6. Most animals, including those infected with subtype ID or IE, were leukopenic. The concentration of glutamic-oxalacetic transaminase in serum was elevated only in monkeys infected with subtype IA or IC. Sera obtained 12 and 47 days after inoculation were tested by serum dilution neutralization and by conventional and "kinetic" HAI tests. The ability of these sera to distinguish among VEE subtypes was somewhat limited; the antigenic differences observed were nevertheless in general agreement with those described by previous workers. This study supports the hypothesis that enzootic VEE subtypes are less pathogenic than subtypes responsible for major epizootics.
32 citations
TL;DR: Data indicate that, for treatment to be successful, the interferon inducer had to be administered sufficiently early during infection to prevent development of detectable viremia and subsequent seeding of target organs.
Abstract: Mice inoculated with encephalomyocarditis virus develop an infection that in many respects simulates human disease caused by enteroviruses. The effect of treatment with a single dose of either polyriboinosinic-polyribocytidylic acid (poly I:poly C) or tilorone hydrochloride on the pathogenesis of the infection with encephalomyocarditis virus in individual mice was correlated with the outcome of the disease in the same animals. Both poly I:poly C and tilorone protected animals from the lethal consequences of the disease when administered prophylactically but were progressively less effective as the infection developed. Successful treatment with either interferon inducer was characterized in every case by complete suppression of detectable viremia. The viremic phase of infection was partially suppressed or delayed by treatment, but detection of circulating virus was always followed by the death of the animal involved. Seeding and subsequent replication of the virus in a target organ (the central nervous system) apparently resulted from the viremia. These data indicate that, for treatment to be successful, the interferon inducer had to be administered sufficiently early during infection to prevent development of detectable viremia and subsequent seeding of target organs. The importance of examining samples from individual animals when investigating the alterations of pathogenesis associated with antiviral chemotherapy was also demonstrated.
30 citations
TL;DR: Adult Syrian hamsters were readily infected by intranasal inoculation with Modoc virus and vertical viral transmission was not demonstrated from five chronically infected female hamsters to their 34 offspring, and if primary infection occurred during pregnancy, the progeny were either stillborn or died shortly after birth, and thus appeared to represent transplacental viral transmission.
Abstract: Adult Syrian hamsters were readily infected by intranasal inoculation with Modoc virus. Viremias were detected 2 to 6 days after infection and peak viremia titers (106.2 plaque-forming units/ml of blood) occurred 4 days postinoculation. All infected animals developed neutralizing and hemagglutination-inhibiting antibodies by 7 days, and complement-fixing antibodies by 14 days postinoculation. High titers of antibodies persisted for at least 4 months. Modoc virus was recovered from throat swabs at 7 days postinoculation, but not at 14 days or later. Urine samples were positive for virus throughout a 12-week observation period. Isolation of virus from lungs and kidneys of one and three animals, respectively, at 151 to 221 days after inoculation confirmed chronic infection. Viral isolations were made only when organs were cultivated in vitro and were unsuccessful by tests on 10% homogenates of the organs. Horizontal viral transmission of virus by infected hamsters that were viruric was demonstrated in only 1 of 27 normal hamsters that were cocaged for 4 weeks under crowded conditions. General failure to obtain horizontal viral transmission may relate to rapid inactivation of virus in excreted urine. Vertical viral transmission was not demonstrated from five chronically infected female hamsters to their 34 offspring. However, if primary infection occurred during pregnancy, the progeny were either stillborn or died shortly after birth, and thus appeared to represent transplacental viral transmission.
21 citations
TL;DR: The results indicated that suppression of a detectable viremia was essential to the successful protection of mice from the lethal consequences of infection, and animals that received the most effective regimen of the interferon inducer were not protected against a second infection with the same virus.
Abstract: These studies were designed to evaluate the therapeutic efficacy of multiple doses of an interferon inducer, polyriboinosinic-polyribocytidylic acid, in encephalomyocarditis virus infection of mice. The results indicated that suppression of a detectable viremia was essential to the successful protection of mice from the lethal consequences of infection. The viremic phase of the infection could be delayed or partially suppressed without protection. The data strongly suggest that once the central nervous system had been seeded and virus replication had begun, inducer therapy was ineffective in altering the outcome of infection. This fact could be attributed in part to the low levels of interferon found in brain tissue after intraperitoneal administration of polyriboinosinic-polyribocytidylic acid. Also, animals that received the most effective regimen of the interferon inducer and that survived the infection were not protected against a second infection with the same virus, an observation suggesting that the incidence of circulating antibody to encephalomyocarditis virus is reduced after the initial infection.
12 citations
TL;DR: In this paper, the authors found that the teratogenic Parvovirus was associated with the erythrocyte fraction of the blood of infected mice, with peak viremia occurring on day 5 or 6 after intraperitoneal inoculation.
Abstract: SummaryMinute virus of mice was found to be closely associated with the erythrocyte fraction of the blood of infected mice, with peak viremia occurring on day 5 or 6 after intraperitoneal inoculation. The association with erythrocytes suggests a common mechanism of transplacental transport for the teratogenic Parvoviruses. In addition, MVM was found to be a relatively poor inducer of interferon and to be very sensitive to the inhibiting action of interferon.
12 citations
TL;DR: Determination of interferon levels in the fetal rhesus monkey 2 days after Chikungunya virus infection showed that during the first third of gestation the fetus was incapable of producing measurable amounts ofInterferon.
Abstract: SummaryDetermination of interferon levels in the fetal rhesus monkey 2 days after Chikungunya virus infection showed that during the first third of gestation the fetus was incapable of producing measurable amounts of interferon. During the second and third periods substantial amounts of circulating interferon (600/900 units/ml) were detected. Viremia was present in all fetuses inoculated with Chikungunya ranging from 103.5 to 104.0 mouse LD50/ml. Control fetuses inoculated with normal saline did not produce circulating interferon. The possible importance of the interferon system in controlling transplacental viral infections in primates is suggested.
5 citations