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Query: UMLS:C0009450 (infectious diseases)
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An international seminar on the treatment and laboratory diagnosis of yellow fever, sponsored by the Pan American Health Organization (PAHO) and held in 1984, differed from previous meetings on yellow fever because of its emphasis on the care and management of patients and because the participants included specialists from several branches of medicine, such as hepatology, haematology, cardiology, infectious diseases, pathology and nephrology. The meeting reviewed the current status of yellow fever and problems associated with case-finding and notification; features of yellow fever in individual countries of Latin America; health services and facilities for medical care as they relate to diagnosis and management of cases; prevention strategies for and current status of immunization programmes; clinical and pathological aspects of yellow fever in humans; pathogenesis and pathophysiology of yellow fever in experimental animal models; clinical and specific laboratory diagnosis; treatment of the disease and of complications in the functioning of individual organ systems; prognosis and prognostic indicators; and directions for future clinical and experimental research on pathophysiology and treatment.
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PMID:Present status of yellow fever: memorandum from a PAHO meeting. 349 Sep 22

The effect of successive lytic passage of yellow fever virus on mosquito infection and transmission rates in the vector, Aedes aegypti, was determined. Three strains of yellow fever virus from Trinidad and Peru were passaged five times in suckling mouse brains and seven times in BHK-21 cells. Mosquitoes were fed meals containing passaged and unpassaged viruses and infection and transmission rates were compared. Rates were similar for all but one of the three virus strains grown in both substrates with the exception of virus strain 1899/81 (human isolate from Peru) passaged seven times in BHK-21 cells. Infection rates declined from 62% (109/177) to 35% (61/176), and transmission rates declined from 64% (60/94) to 45% (22/49). The oligonucleotide fingerprint of strain 1899/81 passaged seven times in BHK-21 cells shared 98% (45/46) of its large, T1-resistant oligonucleotides with the parent strain, indicating limited biochemical differences. The data suggest that uncloned yellow fever virus populations, passaged a limited number of times, and exhibiting some phenotypic changes, are representative of the original virus strain and can be used with a reasonable degree of confidence in vector competence studies.
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PMID:Passage of yellow fever virus: its effect on infection and transmission rates in Aedes aegypti. 378 77

Twenty-eight populations representing a worldwide distribution of Aedes aegypti were tested for their ability to become orally infected with yellow fever virus (YFV). Populations had been analyzed for genetic variations at 11 isozyme loci and assigned to one of 8 genetic geographic groups of Ae. aegypti. Infection rates suggest that populations showing isozyme genetic relatedness also demonstrate similarity to oral infection rates with YFV. The findings support the hypothesis that genetic variation exists for oral susceptibility to YFV in Ae. aegypti.
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PMID:Oral infection of Aedes aegypti with yellow fever virus: geographic variation and genetic considerations. 383 4

Animal virology has made outstanding contributions to preventive medicine by the development of vaccines for the control of infectious disease in man and animals. Cost-benefit analysis indicates substantial savings in health care costs from the control of diseases such as smallpox, poliomyelitis, yellow fever and measels. Areas for further development include vaccines for influenza (living, attenuated virus), the herpes group (varicella: cytomegalovirus), respiratory syncytial virus, rotavirus and hepatitis A, B, and non A/non B. The general options for vaccine formulation are discussed with particular emphasis on approaches with the use of viral genetics to 'tailor make' vaccine viruses with defined growth potential in laboratory systems, low pathogenicity, and defined antigens. Current progress with the development of an inactivated hepatitis B vaccine is reviewed as a case study in vaccine development. The impact of recent experiments in cloning hepatitis B virus DNA in E. coli on the production of a purified viral polypeptide vaccine is assessed.
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PMID:Prospects for new viral vaccines. 610 50

Earlier epidemiological concepts are discussed briefly. Attention is focussed on several of the puzzling problems in the epidemiology of the disease as seen today. The recurring outbreaks of yellow fever in regions where it has been absent, as well as the absence of yellow fever in regions where the vectors exist are discussed. Features of vaccination are discussed, including the long persistence of humoral antibodies and long duration of effective protection. The possibility of changes in virulence of yellow fever strains is mentioned. In some of the modern outbreaks, virulence for human beings appears to be lower than virulence noted some centuries ago, and a hypothesis is advanced. The possible influence of virus-protecting antibodies acquired by infection by other flaviviruses is mentioned. With respect to the vectors of yellow fever, the possibility of differing susceptibility and of different behaviour of various strains is discussed. Transovarial transmission of the virus in the vector mosquito is mentioned as a possible mechanism for long persistence of the virus in nature. Infection of ticks and transovarial transmission of virus in ticks are also mentioned. The need for a diagnostic test to differentiate immunity produced by a naturally acquired infection from immunity induced by vaccination is stressed.
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PMID:The known and the unknown in yellow fever ecology and epidemiology. 614 30

A three-part epidemiological investigation was made on flaviviruses:1. As a preliminary to tests on cattle sera from the field, the antigenic cross-reactivity of Wesselsbron, Spondweni, Usutu, Banzi, West Nile and yellow fever flaviviruses was studied in antisera prepared in guinea pigs. As described earlier for flaviviruses, sera were found to be highly cross-reactive in haemagglutination-inhibition (HAI) tests, less cross-reactive in complement-fixation (CF) tests and were virtually monospecific in microneutralization (NT) tests in Vero cell cultures.2. Infection with Wesselsbron (WSL) virus produced mild febrile illness and viraemia in 5 out of 6 newborn calves, 3 out of 4 pregnant heifers and 3 out of 4 ewes. One heifer produced a weak calf which died soon after birth with WSL antibodies in its serum, indicating that infection had occurred in utero. The 3 other heifers produced healthy calves which lacked antibody in pre-colostral serum. Pathological changes occurred in the foetus in 2 out of 3 pregnant ewes and the ewe produced a healthy lamb which had antibodies to WSL virus in pre-colostral serum.Unlike the situation in guinea pigs, cattle sera were monospecific for WSL virus in CF tests, but sheep sera cross-reacted with Banzi and yellow fever viruses. Re-infection of the cattle with Banzi, West Nile, Spondweni and Usutu viruses failed to induce marked antibody responses. The results suggest that antibodies to WSL virus in cattle sera from the field can be distinguished from those induced by other flaviviruses by quantitative serological tests.3. HAI antibodies to WSL virus were detected in 2648/14395 cattle sera tested over 11 years from 1967 to 1978 in the course of investigation of abortion, infertility and other diseases. Results of quantitative HAI, CF and NT tests with six flaviviruses on 409 selected sera confirmed that infection was due to WSL virus. Serological evidence failed to implicate WSL virus as a cause of abortion in cattle. In a prospective study, abortion occurred in only one out of 21 heifers observed to gain WSL infection during pregnancy in the field, but abortion also occurred in five out of 207 heifers which did not become infected with WSL. No histopathological lesions diagnostic of WSL disease were observed in 1998 specimens from cattle, sheep and goats examined over 44 months prior to October 1972, and WSL virus was isolated once, from the organs of a cow, out of 2106 specimens from cattle sheep and goats tested virologically over six years from October 1972 to September 1978. HAI antibodies to WSL virus were detected in one out of 374 sera from aborted cattle foetuses. It was concluded that WSL virus is not an important cause of disease in cattle, despite widespread occurrence of infection.
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PMID:An investigation of flavivirus infections of cattle in Zimbabwe Rhodesia with particular reference to Wesselsbron virus. 630 Feb 26

Strains of yellow fever virus isolated since 1927 in Africa and the Americas, and strains derived from them, have been differentiated by the responses of mice of different ages to intraperitoneal (i.p.) or intracerebral (i.c.) infection. Infection, antibody conversion, protection and death have been presented on age-dose response phase diagrams that serve as in vivo 'fingerprints' for the differentiation of virus strains and their modifications through passage and selection. Correlations between marker characteristics are discussed in terms of the efficiency of infection, regulatory (pre-challenge) and protective (post-challenge) immunity, and the expression of virulence. The requirement in virus strain specification for the resolution of events on pathogenic and immunogenic pathways is discussed.
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PMID:The in vivo differentiation of strains of yellow fever virus in mice. 676 76

Premunition, infection immunity and virus persistence are notions of the theory of immunity, which, on account of their communities lead to the conclusion that the intracellular inclusion of the living agent is the basis of every acquired immunity. The antibodies of the vertebratae have an exclusively sensory function. They are no immune bodies. Acquired immunity is the ability to prevent a repetition of the same disease. But it does not protect from a local infection with the same agent. Local infections arise by the fact that specific antibodies were acquired already before the infection or were preformed in the genome of the host cells and may be called at once. Their germs lead to an inflammation at the entrance. Cyclic infectious diseases with particularly reliable immunity are certain virus diseases, such as measles, poliomyelitis and yellow fever. The viruses increase in the intracellular space may persist there and may later on evoke local recidivations, like the viruses of the herpes group. As a purely sensory substrate antibodies only evoke the inflammatory disease, but they are not carriers of the acquired immunity, but in certain cases only a mediator for these. Only in a prophylactic dosage antibodies may have an effect preventing disease. The gradual change of the contents of the notion of immunity in the course of this century has led the theoretical research to large difficulties, even to contradictions, respectively. Their correction by retroreflection to the original contents of the notion is necessary, in order to create clear fundaments for the future.
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PMID:[Critical backward glance at the development of the science of immunity]. 702 78

Growth characteristics of 17D yellow fever virus (17D-YF) and conditions for infection were studied in U937, a macrophage-like, Fc receptor-bearing continuous human cell line. Antibody to 17D-YF was obtained by immunization of normal subjects with 17D-YF vaccine. Cells were infected in the presence or absence of immune whole sera or immunoglobulin fractions. Infection of U937 was temperature dependent; the yield of virus was variable but at low temperature viral titers were consistently higher when infection was established in the presence of antibody. Results of infectious center assays indicated that the increased yield of virus was largely or entirely due to an increase in the number of cells producing virus early in the course of infection. Enhancement of viral growth was mediated by IgG but not IgM fractions of immune sera. Trypsinization of U937 resulted in a 90 to 95% reduction of infection in the absence of antibody but in the presence of antibody viral titers were higher in trypsinized than in nontrypsinized cells. Antibody to 17D-YF, contained in the whole IgG fraction of sera, bound to U937 to mediate infection without first being complexed to virus. Preincubation of U937 with IgG1 but not IgG2 myeloma proteins abrogated antibody-mediated infection. This result is compatible with the known affinities of U937 Fc receptors for specific subclasses of IgG and provides evidence for the role of the Fc receptor in antibody-mediated enhancement of viral growth. Persistent infection characterized by a lack of detectable cytopathogenic effect was established in long-term cultures of U937. This pattern of infection might be related to the unique effectiveness of the 17D-YF vaccine.
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PMID:Growth of 17D yellow fever virus in a macrophage-like cell line, U937: role of Fc and viral receptors in antibody-mediated infection. 725 55

The 17D vaccine strain of yellow fever virus (17D-YF) produces a safe human arboviral infection that can provide antisera of well-defined specificity under chronologically defined conditions. We studied 17D-YF growth in human peripheral blood macrophages and in two continuous Fc receptor-bearing, macrophage-like cell lines, P388D1 of mouse origin and U937 of human origin. Cells were infected with virus in the presence or absence of antibody to 17D-YF and to two related flaviviruses, St. Louis encephalitis (SLE) and dengue 2 (D2V). The virus 17D-YF grew in the three cell types when infection was established without antibody; viral yields were increased by addition of antibody to 17D-YF, SLE, and D2V. Increased titers of virus were accompanied by an increased number of infected cells by immunofluorescent assay. Enhancing activity was present in the IgG but not the IgM fractions of immune sera. Infection without cytopathic effect was observed in U937.
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PMID:Antibody-mediated infection of macrophages and macrophage-like cell lines with 17D-yellow fever virus. 729 76


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