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S B Halstead

Publications and source records attributed to S B Halstead.

At least 55 records · Page 3Linked to original sources
PubMed1984

Risk factors in dengue shock syndrome: a prospective epidemiologic study in Rayong, Thailand. I. The 1980 outbreak.

In January 1980, the municipal area of Rayong, Thailand, and contiguous suburban villages were chosen for a long-term study on dengue epidemiology. From 3,185 children randomly sampled in schools and households, the population prevalence of neutralizing antibody to the four dengue serotypes was estimated. To estimate the incidence of infection with each dengue virus serotype (dengue seroconversions), first grade children were re-bled in January 1981 (cohort study). Children admitted to hospital were studied for dengue virus isolation and antibody responses in paired sera. An epidemic of dengue occurred in 1980. Plaque reduction neutralization tests of 1,009 pre-epidemic sera from children aged less than 1-10 years of age determined that 3.3% were immune to dengue 1, 13.2% to dengue 2, 6.4% to dengue 3, and 5.8% to dengue 4. Examination of pre- and post-epidemic cohort blood samples revealed that the incidence of dengue infection in 251 seronegative children was 39.4% (15.1% dengue 1, 11.1% dengue 2, 2.0% dengue 3, 4.8% dengue 4, and 6.4% two or more dengue viruses). Among the 52,935 residents of the study area, there were 22 cases of virologically and clinically confirmed dengue shock syndrome, in children 15 years or younger. All 22 shock syndrome cases had secondary type antibody responses. Eight of 22 had been included in the random serologic sample prior to onset of shock; five had been immune to dengue 1, two to dengue 3, one to dengue 4, and none to dengue 2. Despite the high rate of dengue 1 infections in 1980, only dengue 2 viruses were recovered from dengue shock syndrome cases, including two dengue 1 immune children with pre-illness serum specimens. Although the pre-epidemic prevalence of antibodies to dengue 1 was the lowest to any type, children with this immunologic background contributed disproportionately to shock cases. In descending order of magnitude, risk factors for dengue shock syndrome in Rayong were secondary infections with dengue 2 which followed primary infections with dengue 1, dengue 3, or dengue 4.

Adolescent↗
PubMed1984

Absence of dengue 2 infection enhancement in human sera containing Japanese encephalitis antibodies.

Sera from 52 young adults resident in a rural area in North Thailand were studied for plaque-reducing neutralizing antibodies against dengue (DEN) viruses types 1-4 and Japanese encephalitis (JE), and for DEN-2 infection-enhancing antibodies using a newly described microtest in the human monocyte cell line, U-937. Infection-enhancing antibody titers in U-937 cells using a simplified micromethod were similar to results obtained by published methods using human peripheral blood leukocytes and a macrotest using U-937 cells. In the sample, there were 23 with antibodies to one or more DEN viruses with or without accompanying JE antibodies; 16 sera demonstrated antibodies only to JE and 13 had no detectable antibodies to any flavivirus. All but two DEN antibody-containing sera enhanced DEN-2 infections in U-937 cells, often to titers of 1:10,000 or greater. By contrast, only one of 16 JE-immune sera enhanced DEN-2 infection in monocytes, and that at a dilution of 1:100. None of the flavivirus-negative sera had DEN-2 enhancing activity. The failure of human anti-JE contrasts with the ability of rabbit anti-JE to enhance DEN-2 infections, but correlates with the absence of recorded instances of dengue shock syndrome in human beings sequentially infected with JE and then a DEN virus. This report seemingly reconciles in vitro and in vivo phenomena, and may provide an opportunity to study mechanisms involved.

Adult↗
PubMed1984

Selection of attenuated dengue 4 viruses by serial passage in primary kidney cells. I. Attributes of uncloned virus at different passage levels.

Attempts were made to attenuate prototype dengue (DEN) 4 (H-241) virus. The original viremic human serum was passed once in a susceptible monkey and twice in Aedes albopictus mosquitoes and then serially passed in primary dog kidney (PDK) and African green monkey kidney (GMK) cells. Weekly transfers of undiluted virus were carried to the 50th passage in both primary cell cultures. Biological markers were studied at passages 7, 15, 30 and 50. Parental DEN-4 phenotype characteristics included large plaque formation in LLC-MK2 cells, plaque formation in GMK cells, cytopathic effect in LLC-MK2 cells, growth in human monocyte cultures, growth at 39 degrees C, consistent production of viremia in monkeys and short-incubation neurovirulence in mice. At the seventh passage in both PDK and GMK cell cultures, DEN-4 viruses exhibited reduced plaque-size in LLC-MK2, and failed to plaque in GMK, to produce cytopathic effect in LLC-MK2, or to grow in human monocytes. Serial passage in PDK, as opposed to GMK, resulted in a graduated loss of monkey virulence. Rhesus monkeys inoculated with the PDK 50 strain failed to develop detectable viremia and only 1 of 4 developed an antibody response. Also, replication of PDK 50 was completely shut-off at 39 degrees C. The graduated change in biological properties noted, particularly those in PDK cells, provide a range of potential vaccine candidates for evaluation in human beings.

Aedes↗
PubMed1984

Selection of attenuated dengue 4 viruses by serial passage in primary kidney cells. II. Attributes of virus cloned at different dog kidney passage levels.

Uncloned dengue (DEN) 4 (H-241) which had been passaged 15, 30 and 50 times in primary dog kidney (PDK) cells were subjected to two successive terminal dilution procedures. In the first (3Cl), virus was diluted in 10-fold steps in 10 replicate tubes. An infected tube from a dilution row with three or fewer virus-infected tubes was selected for two further passages. In the second (TD3), virus was triple terminal diluted using 2-fold dilution steps and selecting one positive tube out of 10. Both procedures selected virus population which differed from antecedents. Plaque size of PDK 15 was medium, PDK 30, small and PDK 50, pin-point. PDK 19-3Cl were medium and 56-3Cl, 24-TD3, 35-TD3 and 61-TD3 were all small. All cloned virus replication was completely shut-off at 38.5 degrees C; PDK 15 and 30 continued to replicate at this temperature. Uncloned viruses showed a graduated decrease in monkey virulence with PDK passage; cloned viruses were either avirulent for monkeys (19-3Cl, 56-31Cl, 24-TD3 and 35-TD3) or produced revertant large plaque parental-type viremia (35-3Cl and 61-TD3). Those cloned viruses which exhibited temperature sensitivity, reduced monkey virulence and stability after monkey passage may be suitable as vaccine candidates for evaluation in human beings.

Animals↗
PubMed1984

Selection of attenuated dengue 4 viruses by serial passage in primary kidney cells. III. Reversion to virulence by passage of cloned virus in fetal rhesus lung cells.

Two strains of primary dog kidney-passaged dengue (DEN) 4 (H-241) virus cloned by terminal dilution (PDK 24-TD3 and 35-TD3) were propagated in fetal rhesus lung (FRhL) cells to produce candidate vaccine virus seeds. Both serial passage and prolonged replication of PDK 24-TD3 in FRhL resulted in appearance of medium and large plaques in LLC-MK2 assays. When picked, these plaques proved to contain temperature-resistant, monkey-virulent revertants. Serial passage and prolonged replication of PDK 24-TD3 in LLC-MK2 cells did not result in reversion; but, prolonged replication in PDK cells did. Passage of PDK 35-TD3 in FRhL cells resulted in appearance of medium size plaques which, when picked, yielded temperature sensitive (ts) (38.5 degrees C) viruses of low monkey-virulence. Because of its stability in monkeys and FRhL cells, reduced monkey virulence and ts property. PDK 35-TD3 is a promising candidate for trial in man.

Animals↗
PubMed1984

Selection of attenuated dengue 4 viruses by serial passage in primary kidney cells. IV. Characterization of a vaccine candidate in fetal rhesus lung cells.

A strain of primary dog kidney (PDK)-passaged dengue (DEN) 4 (H-241) virus cloned by terminal dilution (PDK 35-TD3) was propagated in large volumes in fetal rhesus lung (FRhL) cells to produce a candidate vaccine for evaluation in man. Production seed (FRhL p2) and candidate vaccine (FRhL p3) were subjected to rigorous safety tests to exclude contaminating microbial agents. There was no significant monkey neurovirulence of parental or PDK-passaged DEN-4 virus or of control fluid cultures. FRhL-passaged viruses retained the phenotypic characteristics: small (occasional medium) plaque; temperature sensitivity at 38.5 degrees C; and absence of plaque formation in African green monkey kidney cells, cytopathic effect in LLC-MK2 cells, and viral growth in human monocytes. FRhL p2 virus displayed low virulence for monkeys; only one of four animals was viremic and three of four developed low-titered antibody. FRhL p3 virus produced viremia in three monkeys and moderate to high hemagglutination-inhibition and neutralizing antibody titers in all animals. Virus at both passages in FRhL exhibited reduced neurovirulence in suckling mice as compared to parental DEN-4. Because of its safety and desirable monkey virulence attributes PDK 35-TD3 FRhL p3 is recommended for human phase I trial.

Animals↗
PubMed1984

Selection of attenuated dengue 4 viruses by serial passage in primary kidney cells. V. Human response to immunization with a candidate vaccine prepared in fetal rhesus lung cells.

A dengue 4 (strain H241, PDK35-TD3 FRhL p3) vaccine attenuated by passage in primary dog kidney cells followed by passage and final vaccine preparation in DBS-FRhL-2 cells was tested in five yellow fever-immune volunteers. Only two volunteers seroconverted by producing hemagglutination-inhibiting and neutralizing antibodies. Mild illness, compatible with dengue infection was found only in the individuals who later developed antibodies. Both volunteers developed a rash by the 8th day following vaccination, coinciding with a slight elevation in temperature and leukopenia. Additionally, several serum enzymes were elevated during the observation period. Dengue 4 virus was isolated from the blood of the two infected volunteers starting as early as day 5 post vaccination. During the viremic period, which lasted 5 days, phenotypically-changed virus was recovered, indicating genetic instability of the vaccine virus. The clinical disease and immune response in the two infected individuals was probably related to replication of the variant virus. Further testing of this vaccine in its present form is not indicated.

Adult↗
PubMed1984

Heterogeneity of infection enhancement of dengue 2 strains by monoclonal antibodies.

Seven dengue (DEN) 2 virus strains were studied for antibody-dependent enhancement (ADE) of infection in P388D1 mouse macrophage-like cells by using a panel of five DEN 2 monoclonal antibodies. DEN 2 strains were of diverse temporal, geographic, and disease origins. By hemagglutination inhibition and a plaque-reduction neutralization test in LLC-MK2 cells, two of the monoclonal antibodies were type specific and three were flavivirus group reactive. In LLC-MK2 cells, the seven DEN 2 viruses each were neutralized by all five monoclonal antibodies. In P388D1 cells, two DEN 2 strains were enhanced by only three monoclonal antibodies, two by four antibodies, and three by all five antibodies, demonstrating that in some instances enhancement is epitope related and not a concentration-dependent function of virus-antibody interactions. However, ADE did not segregate with determinants exhibiting either the flavivirus group or the dengue type specificity. The presence or absence of enhancement determinants on DEN 2 strains did not correlate with the geographic origin of virus or the severity of disease yielding the strain. The heterogeneous distribution of enhancement determinants may provide a valence mechanism contributing to a multiple increase of infection enhancement in macrophages.

Animals↗
PubMed1983

Treatment of intracranial dengue virus infections in mice with a lipophilic derivative of ribavirin.

Rimantadine, ribavirin, and 6-mercapto-9-(tetrahydro-2-furyl)purine, administered intraperitoneally every 8 h for 7 days starting minutes after virus challenge, had no effect on survival and mean survival time of BALB/c mice inoculated intracranially with dengue virus type 2. In contrast, intraperitoneal treatment with ribavirin 2',3',5'-triacetate, a lipophilic analog of ribavirin, effected significant increases in both mean survival time and survival rate, suggesting that ribavirin 2',3',5'-triacetate may be superior to rabavirin for treatment of viral diseases of the brain.

Adamantane↗
PubMed1983

Role of antibodies and host cells in plaque enhancement of Murray Valley encephalitis virus.

Chicken antisera to Murray Valley encephalitis (MVE) virus, when incubated with virus and assayed for plaques on chicken embryo (CE) monolayers, neutralized MVE virus at high concentrations of antibody, but caused increases in plaque counts at low concentrations of antibody. Plaque enhancement did not occur when the same virus-antibody mixtures were assayed on a continuous line of rhesus monkey kidney cells (LLC-MK2), nor when the anti-MVE antibody was of mammalian origin and the assay system was CE monolayers. Correspondingly, chicken anti-MVE did not enhance the plaque formation of MVE virus in a stable line of mouse macrophages, P-388D1, whereas rabbit and mouse anti-MVE did enhance plaque formation. This enhancing activity was associated with noncytophilic immunoglobulin G (IgG). The Fc terminus of the IgG molecule was required, as no plaque enhancement occurred with chicken anti-MVE Fab. These data indicate that there is a requirement for taxonomic complementarity between Fc termini and Fc receptors in the above systems. CE cell monolayers were found to contain approximately 2% of Fc receptor-bearing cells among the fibroblast-like cells. Fc receptor-bearing cells in CE monolayers were isolated and found to be of the mononuclear phagocytic lineage. These mononuclear phagocytes, which originate in lymphoid tissues and blood associated with CE tissue fragments, are integrated into primary CE monolayers and form infectious centers in the presence of virus and low dilutions of antibody.

Animals↗
PubMed1983

Original antigenic sin in dengue.

Sequential blood samples were obtained from eight Thai children before, during and 3-5 months after hospitalization for dengue shock syndrome. All patients experienced a secondary-type antibody response as evidenced by hemagglutination-inhibition antibody responses in acute and convalescent sera. Dengue 2 viruses were recovered from two patients. In their pre-illness blood sample, all children had monotypic neutralizing antibodies; five to dengue 1, two to dengue 3 and one to dengue 4. The highest neutralizing antibody titers in acute phase and late convalescent sera were to the initial infecting virus type. This report documents for sequential dengue infections the existence of an original antigenic sin antibody response. It may be possible to apply this phenomenon to identify initial dengue serotype infection in individuals experiencing secondary dengue infections, thus helping to clarify the antecedents to dengue shock syndrome.

Adolescent↗
PubMed1983

Comparison of P388D1 mouse macrophage cell line and human monocytes for assay of dengue-2 infection-enhancing antibodies.

Tissue culture-adapted dengue 2 virus (DEN 2), strain 16681, exhibits antibody-dependent enhancement of infection (ADE) in P388D1 cells, a mouse macrophage-like cell line. ADE is dependent upon maintaining DEN 2 multiplicity of infection at between 0.1 and 0.001, and can be simply measured in multi-well plastic plates. The assay uses either trypsinized or non-trypsinized P388D1 cells at 5 x 10(5) cells per ml, an appropriate dilution of DEN 2 virus, and a source of antibody, and is most conveniently performed without further washing of stationary cultures, which are incubated in 5% CO2. Trypsinization of P388D1 cells prior to the addition of virus-serum mixtures reduced infection in control cultures thus increasing ADE. When cells were washed after incubation of virus-serum mixtures for 1 hour, a paradoxical increase of infection in cultures exposed to virus plus normal serum was noted, which reduced the sensitivity of the ADE assay. Using human cord blood sera, ADE titers measured in human monocytes and P388D1 cells were closely similar. This convenient and economical assay will facilitate large scale biological and epidemiological studies of dengue virus enhancing antibodies.

Animals↗
PubMed1983

Cell-mediated immune response to respiratory syncytial virus infection in owl monkeys.

The suitability of owl monkeys as experimental models to study the cellular immune response to respiratory syncytial virus (RSV) infection was examined. Seronegative owl monkeys inoculated intranasally with RSV shed large quantities of virus and developed clinically evident upper respiratory disease. RSV infected monkeys had significant lymphoproliferative responses to RSV antigen by 4 weeks post-infection. In contrast, no positive blastogenic responses were elicited during the acute phase of illness. An in vitro 51Cr release assay was developed to study owl monkey antibody-dependent cellular cytoxicity (ADCC) against RSV infected Hep-2 cells. Peripheral blood mononuclear cells from owl monkeys in the presence of RSV specific antibody caused lysis of RSV infected target cells. The effector cell for ADCC was found to be non-adherent to plastic. The owl monkey RSV ADCC system was found to closely parallel RSV specific ADCC observed with human effector cells. In addition, it was found that heterologous matches of human effector cells with monkey sera and monkey effector cells with human sera were equally efficient in mediating RSV specific ADCC. These studies demonstrate the value of the owl monkey as a model to study the pathogenesis or RSV infections.

Animals↗
PubMed1982

Rubella antibody persistence after immunization.

A comparative field trial of three live, attenuated rubella virus vaccines (Cendehill, HPV 77 DE-5, and HPV-77 DK-12) was initiated in 1969 on the islands of Kauai and Hawaii in the state of Hawaii. Following initial seroconversion rates of more than 98%, periodic serological testing of the study population was conducted to assess the durability of vaccine-induced immunity. In February 1980, ten years after the initiation of the study, 741 of the 5,153 original susceptible vaccinees were still enrolled in the study. After a drop of approximately 50% in mean hemagglutination-inhibition (HI) titer for each of the vaccine groups during the first four years following vaccination, the HI titer levels for all three groups have been generally stable between years 4 and 10. The frequency of reversion to an HI titer of less than 10 has remained less than 0.5% per year. A measurable HI antibody level has persisted in more than 97% of all vaccines over the ten-year period. This study indicates that when potent rubella vaccine is administered properly, a high seroconversion rate and a high rate of antibody persistence should be expected.

Antibodies, Viral↗
PubMed1982

Antiviral effects if ribavirin and 6-mercapto-9-tetrahydro-2-furylpurine against dengue viruses in vitro.

The antiviral effects of ribavirin (1-beta-D-ribofuranosyl-1,2,4-triazole-3-carboxamide) and 6-mercapto-9-tetrahydro-2-furylpurine (6-MPTF) against dengue viruses were examined in vitro. Ribavirin significantly reduced the growth of dengue virus types 1-4 in LLC-MK2 cells at concentrations well below cytotoxic levels (cell viability was determined by trypan blue dye exclusion) Addition of guanosine to ribavirin-treated dengue virus-infected cell cultures completely reversed the antiviral effect of the drug. In contrast, ribavirin had no effect on dengue virus replication in human peripheral blood leukocytes (PBL). 6-MPIF, a specific inhibitor of hypoxanthine-guanine phosphoribosyltransferase, did not significantly reduce the growth of dengue viruses in either LIC-MK2 cells or human PBL. However, synergistic effects of 6-MPTF and ribavirin were observed, as combined treatment of the drugs markedly suppressed the replication of dengue viruses in human PBL. The successful demonstration that dengue virus replication in mononuclear leukocytes is markedly suppressed by the combined treatment of ribavirin and 6-MPTF signals a need to evaluate the efficacy of this treatment against dengue virus infections in vivo.

Animals↗