Biomedical subjects

C H Hoke

Publications and source records attributed to C H Hoke.

At least 55 records · Page 3Linked to original sources

PubMed1990

Preparation of an attenuated dengue 4 (341750 Carib) virus vaccine. II. Safety and immunogenicity in humans.

To determine safety and immunogenicity, a single 0.5 ml dose of a monovalent live-attenuated dengue (DEN) 4 (341750 Carib) vaccine was given sc to 3 groups of flavivirus nonimmune volunteers in increasing concentrations. Two recipients received 10(3) plaque forming units (PFU)/dose (1:100 dilution of stock vaccine). One remained asymptomatic, but became viremic between days 12 and 15, experienced a mild elevation of temperature (37.4 degrees C), and developed DEN-4 specific antibody. Neither recipient of the 10(4) PFU became infected. Eight volunteers then received undiluted vaccine (10(5) PFU). Viremia and antibody (neutralizing, hemagglutination inhibition, and IgM) developed in 5 of the 8 (63%). These 5 volunteers also developed a scarcely noticeable macular, blanching rash and minimal temperature elevations (37.3, 38.1, 37, 37.9, and 37.9 degrees C). Clinically insignificant decreases in total white blood cell, lymphocyte, and polymorphonuclear cell counts and an elevation in mononuclear cell counts occurred in association with viremia. This vaccine is safe, reasonably immunogenic, and suitable for further evaluation.

Adult↗

PubMed1989

Molecular characterization of a neutralizing domain of the Japanese encephalitis virus structural glycoprotein.

Expression of antigenic fragments of the Japanese encephalitis virus envelope protein (E) in Escherichia coli has been used to define the boundaries of an antigenic domain that contains the binding sites for 10 anti-E monoclonal antibodies (MAbs). All of these antibodies neutralized the virus in vitro and some of them passively protected mice from a fatal virus challenge. We have shown previously that nine of these antibodies react with the antigenic determinants encoded by a 405 bp fragment of viral cDNA. To determine the amino acid sequences of specific determinants, truncated polypeptides were expressed as fusion proteins in E. coli following progressive Bal 31 exonuclease digestion of the 5' and 3' ends of the cDNA fragment. Examination of the immunoreactivity of these polypeptides revealed that the region from methionine 303 to tryptophan 396 was the shortest sequence capable of reacting with any of the 10 MAbs or with a polyclonal, antiviral hyperimmune mouse ascitic fluid. Biochemical tests showed that an intramolecular disulphide cross-linkage between cysteine 304 and cysteine 335 of the E protein sequence was required for presentation of the binding site(s) for these MAbs. Although this 95 amino acid antigenic domain appeared to be capable of forming several conformational neutralizing epitopes, it was not an effective immunogen for inducing neutralizing or protective antibodies in mice.

Amino Acid Sequence↗

PubMed1989

An enzyme-linked immunosorbent assay to characterize dengue infections where dengue and Japanese encephalitis co-circulate.

The diagnostic sensitivity and specificity of detection of anti-dengue IgM by antibody capture enzyme-linked immunosorbent assay (ELISA) was investigated in dengue infections in a variety of clinical settings. Sera from uninfected controls were uniformly negative. Serial specimens from experimental and natural infections showed that viremia and fever terminated as anti-dengue IgM became detectable. Anti-dengue IgM appeared in most cases by the 3rd afebrile day of illness and declined to undetectable levels after 30-60 days. Assay sensitivity was 78% in admission sera (924/1,183; 95% CI = 75-81%) and 97% in paired sera (1,030/1,062; 95% CI = 96-98%) thus exceeding or matching the performance of the hemagglutination-inhibition assay. Measurement of the anti-dengue IgM to anti-Japanese encephalitis IgM ratio correctly identified all sera from 112 patients with strictly defined Japanese encephalitis and 98% (307/312; 95% CI = 96-99%) of sera from patients whose dengue infections were confirmed by virus isolation. Dengue infections could be classified as primary or secondary by determining the ratio of units of dengue IgM to IgG antibody. We propose that measurement of dengue and Japanese encephalitis IgM and IgG antibodies upon admission and discharge from hospital care should replace the hemagglutination inhibition assay as the standard dengue serologic technique in regions where these 2 viruses co-circulate.

Acute Disease↗

PubMed1988

Protection against Japanese encephalitis by inactivated vaccines.

Encephalitis caused by Japanese encephalitis virus occurs in annual epidemics throughout Asia, making it the principal cause of epidemic viral encephalitis in the world. No currently available vaccine has demonstrated efficacy in preventing this disease in a controlled trial. We performed a placebo-controlled, blinded, randomized trial in a northern Thai province, with two doses of monovalent (Nakayama strain) or bivalent (Nakayama plus Beijing strains) inactivated, purified Japanese encephalitis vaccine made from whole virus derived from mouse brain. We examined the effect of these vaccines on the incidence and severity of Japanese encephalitis and dengue hemorrhagic fever, a disease caused by a closely related flavivirus. Between November 1984 and March 1985, 65,224 children received two doses of monovalent Japanese encephalitis vaccine (n = 21,628), bivalent Japanese encephalitis vaccine (n = 22,080), or tetanus toxoid placebo (n = 21,516), with only minor side effects. The cumulative attack rate for encephalitis due to Japanese encephalitis virus was 51 per 100,000 in the placebo group and 5 per 100,000 in each vaccine group. The efficacy in both vaccine groups combined was 91 percent (95 percent confidence interval, 70 to 97 percent). Attack rates for dengue hemorrhagic fever declined, but not significantly. The severity of cases of dengue was also reduced. We conclude that two doses of inactivated Japanese encephalitis vaccine, either monovalent or bivalent, protect against encephalitis due to Japanese encephalitis virus and may have a limited beneficial effect on the severity of dengue hemorrhagic fever.

Adolescent↗

PubMed1988

Functional and antigenic domains of the dengue-2 virus nonstructural glycoprotein NS-1.

The gene coding for the nonstructural glycoprotein of dengue-2 virus was cloned, sequenced, and expressed in Escherichia coli. There was about 70% conservation at the amino acid level with dengue serotypes 1 and 4 suggesting an important common function for this protein. Conserved hydrophobic domains were found both before the amino-terminus and at the carboxy-terminus, consistent with transmembrane roles. Evidence for at least partial translocation of NS-1 through the inner membrane of E. coli was found. Also conserved were two signals for N-linked glycosylation located near the middle of NS-1. Various regions of NS-1 were tested for antigenicity with mouse and rabbit polyclonal and mouse monoclonal antibodies. The mouse polyclonal antibodies, made against a crude dengue-infected mouse brain immunogen, reacted most strongly with N-terminal regions of NS-1, whereas, the rabbit antiserum, made against purified NS-1 protein, reacted strongest with C-terminal regions. These findings suggest that immunogen presentation or species differences could be important. Although most of the monoclonals appeared to be unreactive in Western blots with expressed NS-1 proteins, two appeared to react strongly; the region from amino acid (a.a.) 273 to a.a. 346 was required for antibody binding. This region, located adjacent to the two conserved C-terminal hydrophobic domains, is highly charged and contains 5 of the 10 conserved cysteine residues of NS-1.

Amino Acid Sequence↗

PubMed1988

Rapid diagnosis of rabies and post-vaccinal encephalitides.

In an attempt to establish the diagnoses of rabies post-vaccinal encephalitis (PVE) and early rabies encephalitis, paired serum and CSF levels of rabies neutralizing antibody (Rab) and rabies specific-IgM (RIgM) were compared in 12 PVE, 10 rabies and five control patients with similar presenting clinical features. Rapid methods of rabies antigen detection were evaluated in 17 patients. All 12 PVE patients had Rab in their serum and in eight it was also present in the CSF. These same eight had RIgM in the serum, and in seven also in the CSF. The CSF antibodies may have originated in the plasma since six patients had a high albumin quotient indicating leakage across the blood-brain barrier. Among the rabies patients, only the two vaccinated ones had serum Rab; this was also detected in the CSF of one and RIgM was in the CSF of the other. A raised IgG Index, indicating intrathecal synthesis of IgG was seen in five of 12 PVE patients. This did not correlate with the presence of CSF rabies antibody, suggesting production of antibody to other vaccine antigens of neural origin. The diagnosis of rabies encephalitis in life was made by antigen detection in a skin biopsy. No false positive results occurred and the method was as efficient as immunofluorescence of a post-mortem brain biopsy.

Adolescent↗

PubMed1987

A longitudinal study of Japanese encephalitis in suburban Bangkok, Thailand.

A one-year study of Japanese encephalitis (JE) in a small focus of transmission was conducted in suburban Bangkok in 1985. Monthly data were collected on weather, vector density, sentinel pig and chick JE antibody seroconversions, and epidemiology as related to human JE cases. The primary vector species were found to be Culex gelidus and Culex tritaeniorhynchus; from which one isolate each was obtained in March and June, respectively. Pig JE antibody seroconversion peaked in April (the hottest month), with secondary peaks following in July and December. Chick seroconversions were found only in June and July. Human cases (7) in the primary focus occurred from May-July, and started 2 months following the finding of the first JEV isolate in mosquitoes and 1 month following mass JEV seroconversion in pigs. Overall, the attack rate in the focus (0.83/10(5] was greater than 4 times that of the rest of Bangkok (0.19/10(5]. Attack rates were highest in 0-9 and 10-19 year-old groups, respectively. Indications are that JEV is transmitted to humans in Bangkok at least 10 out of 12 months per year, but that cases are concentrated in the May to July period.

Adolescent↗

PubMed1986

Field trial of a Japanese encephalitis diagnostic kit.

Serum and cerebrospinal fluid (CSF) obtained from patients in rural Thailand during an encephalitis epidemic were assayed with a Japanese encephalitis rapid diagnosis kit. Japanese encephalitis was diagnosed by detection of virus-specific IgM (JEV IgM) in CSF (1:10 dilution) or serum (1:100 dilution) with an antibody capture enzyme-linked immunosorbent assay. Specimens were assayed immediately on site at the provincial hospital and scored by visual examination within 4 h. Each specimen was retested carefully later to accurately determine its activity (units) at a single screening dilution; each was tested also at serial dilutions to determine its end-point titer. On-site kit results showed close agreement with subsequent laboratory results for detection and quantitation of JEV IgM and JEV IgG in either serum or CSF. Using the kit on site, admission CSF from 35 (73%) of 48 laboratory-proven JEV-infected patients were scored as definitely positive for JEV IgM, while all 17 CSF specimens from non-JEV infected patients were read as negative (sensitivity 73%, specificity 100%). A rapid and early diagnosis of acute Japanese encephalitis can be accomplished almost anywhere.

Antigen-Antibody Complex↗

PubMed1986

Virus isolations from mosquitoes collected during the 1982 Japanese encephalitis epidemic in northern Thailand.

From 16 June to 15 August, 1982 CDC light traps were used to collect mosquitoes in the province of Kamphaengphet, N. Thailand. 353,042 mosquitoes comprising 59 species were collected and identified, and 345,173 were placed in pools for attempted virus isolation by inoculation of C6/36 Aedes albopictus mosquito cell cultures. Viruses were isolated from 63 mosquito pools. These comprised 56 flaviviruses, identified as 35 isolates of Japanese encephalitis (JE) virus strains, 18 strains of Tembusu (TEM) virus and three untyped flaviviruses (FLA); three alphaviruses, identified as the first isolates of Getah (GET) virus to have been made in Thailand; and four viruses which are still unidentified. Most virus isolates were from Culex tritaeniorhynchus mosquitoes collected in carbon dioxide baited light traps. JE virus was isolated only over a ten-day period and the last isolate was obtained one week before the peak of admission of human encephalitis cases at Kamphaengphet Provincial Hospital. Rapid screening of isolates grown on Ae. pseudoscutellaris (LSTM-AP-61) mosquito cells by indirect immunofluorescence using flavivirus group-specific and JE-specific monoclonal antibodies showed a high degree of correlation with plaque reduction neutralization tests. An antigen capture enzyme immunoassay (EIA) test successfully identified about 50% of the JE virus positive pools, but the method saved considerable processing time.

Alphavirus↗

PubMed1986

Isolation of Japanese encephalitis virus from clinical specimens using a continuous mosquito cell line.

During the 1983 Japanese encephalitis (JE) epidemic in northern Thailand, we systematically attempted to isolate JE virus (JEV) from clinical specimens collected from 49 consecutive JE patients at 1 provincial hospital. Fresh acute plasma and cerebrospinal fluid (CSF) samples and postmortem brain samples were immediately inoculated onto cultured monolayers of Aedes pseudoscutellaris (LSTM-AP-61) cells which had been shipped to the epidemic site. None of 49 plasma samples yielded virus. None of 30 fresh CSF samples from nonfatal cases yielded virus, but 5 of 15 (33%) CSF samples from fatal cases did. Inoculation of fresh brain specimens obtained at autopsy yielded virus in every case attempted (7 of 7), whereas postmortem needle biopsy specimens of brain yielded virus in only 1 of 4 cases. Isolates were most frequently successful using thalamic tissue (6 of 7 cases), but isolates were also commonly obtained from frontal cortex (4/7), occipital cortex (4/7), cerebellum (4/7), medulla (4/7) and pons (2/7).

Aedes↗

PubMed1986

Blood value changes in flavivirus-inoculated Macaca fascicularis monkeys.

Blood values were analysed in eighteen cynomolgus monkeys on pre-and post-neurovirulence testing of dengue-2 and yellow fever vaccine viruses, dengue-2 parental and Japanese encephalitis viruses. Certain changes between blood chemistry, hematology and serology were observed and briefly discussed.

Animals↗

PubMed1986

Anti-rabies virus IgM in serum and cerebrospinal fluid from rabid dogs.

An anti-rabies IgM antibody capture radio immunoassay was used to test serum and cerebrospinal fluid from 37 dogs held in quarantine for suspicion of rabies. Rabies was confirmed in dogs that died by mouse inoculation and subsequent examination of mouse brains by fluorescent antibody technique to detect rabies antigen. The mean counts per minute (CPM) of iodinated anti-rabies gamma globulin coupled IgM rabies antibody in CSF and serum from rabid dogs were significantly higher than in CSF and serum from non-rabid dogs. Mean CPM from rabid dogs was greater in CSF than in sera, in contrast with non-rabid dogs, from which mean cpm was higher in sera than CSF, suggesting that antibody may have been synthesized in the CSF. To evaluate this test further, a dog was infected by rabies virus, and serial serum and CSF specimens were collected until the time of death. IgM anti-rabies antibody developed in the CSF and serum 29 days following infection, and rose just before the dog died of rabies on day 34. The rabies MAC RIA is potentially useful as a diagnostic method in quarantined dogs with rabies-like illness. Perhaps more importantly, it may be applied to better understand the immunopathogenicity of rabies.

Animals↗

PubMed1985

Japanese encephalitis: immunocytochemical studies of viral antigen and inflammatory cells in fatal cases.

The distribution of virus and the composition of the mononuclear inflammatory response were studied in the brains of 7 children who died with Japanese encephalitis. Viral antigen was localized to neurons, with greatest involvement in the thalamus and brainstem. Quantitation of perivascular inflammatory responses showed a preponderance of T cells, but only 7 to 30% of these cells were T suppressor/cytotoxic cells. Inflammatory cells invading the parenchyma were predominantly macrophages with small numbers of T cells. B cells remained localized to perivascular cuffs. Viral antigen was progressively cleared in patients with survival of 6 days or more.

Antibodies, Viral↗

PubMed1985

Fatal outcome in Japanese encephalitis.

Forty-nine consecutive patients with laboratory-confirmed acute Japanese encephalitis were studied to identify risk factors present at hospital admission which were associated with a fatal outcome. Sixteen patients (33%) died. The following constellation of findings correlated with a fatal outcome: infectious virus in cerebrospinal fluid (CSF), low levels of Japanese encephalitis virus-specific IgG and IgM in both CSF and serum, and a severely depressed sensorium. Age, sex, days ill before admission, distance from home to the hospital, past medical history, CSF protein content, and CSF leukocyte count were not significant risk factors. Among patients hospitalized for acute Japanese encephalitis, a vigorous virus-specific immunoglobulin response, both systemically and locally within the central nervous system, is a good marker for survival, and may be an inherently important factor in recovery from illness.

Adolescent↗

PubMed1985

Improved surveillance of Japanese encephalitis by detection of virus-specific IgM in desiccated blood specimens.

An IgM antibody-capture type enzyme-linked immunoassay (MAC ELISA) was compared with the haemagglutination inhibition method (HI) for establishing a laboratory diagnosis of acute Japanese encephalitis (JE) virus infection using specimens of dried blood eluted from filter paper strips. Paired samples from 243 encephalitis patients, which had been obtained by mail through a national surveillance programme in Thailand, were tested. During the peak of the 1983 encephalitis epidemic, 72% of cases were diagnosed as Japanese encephalitis by MAC ELISA, compared with only 38% by HI. During non-epidemic periods, the proportions diagnosed as Japanese encephalitis by MAC ELISA or HI were 26% and 33%, respectively. Detection of IgM anti-JE activity by the antibody-capture immunoassay is superior to the HI method for establishing a diagnosis of acute Japanese encephalitis using dried blood specimens.

Blood Specimen Collection↗

PubMed1984

Dengue virus type 2 vaccine: reactogenicity and immunogenicity in soldiers.

A live dengue virus type 2 (dengue-2) vaccine (PR-159/S-1) was tested for reactogenicity and immunogenicity in a placebo-controlled, double-blind clinical trial involving 98 soldiers. Seroconversion rates based on the development of neutralizing antibody to dengue-2 were 90% in 70 recipients with immunity to yellow fever and 61% in 28 vaccinees without such immunity (P less than .01). Peak titers of neutralizing antibody were three times higher in recipients with antibody to yellow fever virus and persisted in most for at least 18 months. Individuals seroconverting to the vaccine virus more frequently experienced systemic symptoms than those who received placebo (P less than .02). Future users of this dengue-2 vaccine may wish to employ immunization schedules that include preliminary immunization against yellow fever and must be prepared to accept mild vaccine-related symptoms in some recipients.

Adolescent↗

PubMed1979

False-positive Gram-stained smears.

The rate per 1,000 smears showing nonviable Gram-negative bacilli (false-positive smears) increased from a baseline of 10.8 to 38.5 following purchase of new culture-collection devices; the rate decreased to 8.0 following replacement of contaminated culture sets. False-positive reports led to changes in therapy for five patients. In addition to being sterile, commercial culture-collection devices should be certified by the manufacturer as being free of stainable microorganisms or as unsuitable for preparation of Gram-stained smears.

Adolescent↗

PubMed1978

A comparison of a WI-38 vaccine and duck embryo vaccine for preexposure rabies prophylaxis.

Two types of rabies vaccine, WI-38 vaccine (WRV) and Duck Embryo Vaccine (DEV) were compared in rabies preexposure prophylaxis. Once group of veterinary students received four doses of DEV, a second group received four doses of WRV, and a third group received two doses of WRV. Adverse reactions were found to be similar for all three gorups. The antibody responses, however, differed markedly: the mean neutralizing titer after four doses of DEV was 1:75, after four doses of WRV was 1:1517, but was only 1:164 after two doses of WRV. All students who received three or four doses of WRV developed high titers of rabies antibody, making this vaccine very desirable for preexposure prophylaxis.

Adult↗