Biomedical subjects

D W Vaughn

Publications and source records attributed to D W Vaughn.

At least 73 records · Page 4Linked to original sources

PubMed1997

Evaluation of a dipstick enzyme-linked immunosorbent assay for detection of antibodies to dengue virus.

Accurate serological confirmation of dengue (DEN) infection is difficult, because simple reliable assays for the detection of DEN antibodies are not available. To address this problem, a dipstick enzyme-linked immunosorbent assay (ELISA) was evaluated. The dipstick contained dots of serially diluted DEN 2 antigen. To detect immunoglobulin G (IgG), the dipstick was processed through four reaction cuvettes containing test serum, enhancer, enzyme-conjugated anti-human IgG and IgM antibody, and substrate. Total assay time was 45 min. To detect IgM, the serum was passed through a protein G device to remove IgG. The dipstick was then processed as before, except that the incubation times were longer and enzyme-conjugated anti-human IgM was used. The total assay time was 3 h. The dipstick ELISA results were compared with results from microplate ELISA. The IgG dipstick ELISA showed a sensitivity of 95.2% and a specificity of 100% compared to an IgG microplate ELISA with serum samples from 125 individuals living in an area in which DEN is endemic. In tests with 75 serum samples from patients with clinically suspected acute DEN infections, the IgM dipstick ELISA showed a sensitivity of 97.9% and specificity of 100% compared to those of an IgM antibody capture microplate ELISA. These results showed that the dipstick ELISA was a sensitive and specific test for the detection of either DEN IgM or IgG in human serum. The dipstick ELISA was also shown to be useful for detecting seroconversions to DEN IgM or IgG in paired serum samples from 20 patients with virus isolation-confirmed acute DEN infections.

Animals↗

PubMed1997

Rapid diagnosis of dengue viremia by reverse transcriptase-polymerase chain reaction using 3'-noncoding region universal primers.

A reverse transcriptase-polymerase chain reaction (RT-PCR) method was developed as a rapid diagnostic test of dengue viremia. To detect dengue viruses in serum or plasma specimens, a pair of universal primers was designed for use in the RT-PCR. Using these primers, the 3'-noncoding region of dengue virus types 1, 2, 3, and 4 could be amplified, but not those of other flaviviruses, such as West Nile virus, Japanese encephalitis virus, and yellow fever virus, or the alphavirus Sindbis virus. The sensitivity of the RT-PCR assay was similar to that of a quantitative fluorescent focus assay of dengue viruses in cell culture. Combining a silica method for RNA isolation and RT-PCR dengue virus could be detected in a 6-hr assay. In a preliminary study using this method, we detected dengue virus in 38 of 39 plasma specimens from which dengue virus had been isolated by mosquito inoculation. We then applied this method for detecting dengue viremia to 117 plasma samples from 62 children with acute febrile illnesses in a dengue-endemic area. We detected dengue viremia in 19 of 20 samples obtained on the day of presentation, which had been confirmed as acute dengue infection by mosquito inoculation and antibody responses. The overall sensitivity of this method was 91.4% (32 of 35; 95% confidence interval [CI] = 82.2-100%). The results from testing plasma samples from febrile nondengue patients showed a specificity of 95.4% (42 of 44; 95% CI = 89.3-100%).

Acute Disease↗

PubMed1997

Recognition of synthetic oligopeptides from nonstructural proteins NS1 and NS3 of dengue-4 virus by sera from dengue virus-infected children.

The nonstructural proteins NS1 and NS3 from dengue virus are involved in the immune response during natural infection in humans. To analyze the immunogeneity of some epitopes present in NS1 and NS3 proteins from dengue virus type-4, six oligopeptides were synthesized; five from NS1 (NS1.1, NS1.2, NS1.3, NS1.4, and NS1.5) and one from NS3 (NS3.1). Peptides NS1.1, NS1.2, NS1.3, NS1.5, and NS3.1 were recognized by sera from dengue virus-infected children, suggesting that they represent exposed epitopes during natural dengue virus infection.

Adolescent↗

PubMed1997

Impact of dengue virus infection on feeding behavior of Aedes aegypti.

In addition to heavily infecting the salivary glands of Aedes aegypti (L.) mosquitoes, dengue viruses produce a significant infection of the nervous system, involving the brain, Johnston's organ, compound eye, and thoracic and abdominal ganglion. To determine if dengue infection affects feeding behavior of Ae. aegypti we measured feeding times, counted the number of feeding delays or interruptions, and by in situ immunocytochemistry techniques determined the spatial and temporal distribution of dengue infections in females parenterally infected with dengue 3 virus. The mean of the total time required for feeding by infected mosquitoes was significantly longer than the time required by uninfected mosquitoes. Similarly, the mean of the time spent probing was significantly longer in infected mosquitoes than in uninfected mosquitoes when day after inoculation was considered. Significant increases in the length of feeding activity in infected mosquitoes corresponded to virus infection in organs that are known to control or influence activities associated with blood feeding. Sequential infections of the salivary glands (five days postinoculation [PI]), brain and compound eye (eight days PI), and Johnston's organ and midgut and abdominal ganglion (11 days PI) of most mosquitoes were observed. The increased time required by infected Ae. aegypti mosquitoes to acquire a blood meal may contribute to the efficiency of Ae. aegypti as a vector of dengue virus. Longer feeding periods are more likely to be interrupted by the host, which increases the chance that an infected mosquito will probe or feed on additional hosts.

Aedes↗

PubMed1997

Short report: an outbreak of Japanese encephalitis in Kathmandu, Nepal.

We report the first proven outbreak of Japanese encephalitis (JE) occurring in the Kathmandu Valley of Nepal. During September and October 1995, we treated 15 patients with meningo-encephalitis. All of the patients were Nepalese, all but one lived in the Kathmandu Valley, and their overall mortality was 53%. Anti-JE virus (JEV) IgM in the cerebrospinal fluid was found in the two cases for whom it was tested. The two tested patients were similar to the other patients in clinical presentation and in home location. We recommend immunization against JEV for those traveling to Kathmandu during the months of August to October.

Aged↗

PubMed1997

Hemorrhagic fever in Cambodia is caused by dengue viruses: evidence for transmission of all four serotypes.

Hemorrhagic fever (HF) has been widespread in Cambodia and thought to be due to dengue virus although laboratory confirmation has been lacking. Between 1980 and 1995, 49,420 cases of HF and 3,032 deaths were reported. Cases increased during this period; large epidemics of HF occurred every two to three years. In 1995 there were 10,208 cases of HF with 424 deaths. Over a two day period in August 1995, 40 consecutive cases were investigated at the National Pediatric Hospital in Phnom Penh, Cambodia. All 40 cases were confirmed as dengue by virus identification and/or serology. Mean age was 6.5 years. Of 39 patients with complete medical records, the diagnoses were: dengue fever (n = 3), dengue hemorrhagic fever (DHF) grade 2 (n = 21), DHF grade 3 (n = 10), and DHF grade 4 (n = 5). The serologic response was secondary in 95%. Dengue virus was identified in 13 of 40 cases. All four dengue serotypes were identified. The high frequency of secondary infections, the low mean age of admission, and identification of all four dengue serotypes support the national statistics to show that DHF is highly endemic in Cambodia.

Adolescent↗

PubMed1997

Herpes simplex virus type-2, cytomegalovirus and Epstein-Barr virus infection in acute non A to E hepatitis Thai patients.

A significant number of acute non A to E hepatitis cases are reported in Thailand every year, and the etiologies of these cases are unknown. Members of the herpesviridae family have been reported to cause either a self limited or fatal hepatitis in a small proportion of patients in other parts of the world. To determine whether herpesviruses may play a role in acute non A to E hepatitis, sera from 32 acute hepatitis patients without markers for acute hepatitis A to E virus infection were examined for IgM to herpesvirus type 2 (HSV-2), cytomegalovirus (CMV), and Epstein-Barr virus (EBV) using commercially available assays. IgM to HSV-2 was detected in four sera, IgM to CMV was detected in one serum, and IgM to EBV was detected in one serum. All of the acute non A to E hepatitis patients recovered and none had underlying conditions associated with impaired immunity. These results suggest that herpesviruses should be considered in the differential diagnosis for Thai patients with hepatitis.

Acute Disease↗

PubMed1996

Testing of a dengue 2 live-attenuated vaccine (strain 16681 PDK 53) in ten American volunteers.

A live-attenuated dengue 2 vaccine (strain 16681 PDK 53) developed at Mahidol University, Thailand was evaluated for safety and immunogenicity by administering 10(4) p.f.u. subcutaneously to ten flavivirus non-immune American volunteers. The vaccine was safe; there were no serious adverse reactions. Eight recipients experienced no or mild side effects. One recipient reported headaches on 7 separate days. One volunteer, who had a fracture of the humerus 1 day after vaccination requiring surgical repair, experienced generalized malaise with fever (maximum temperature = 38.9 degrees C), headache, eye pain and myalgia lasting less than 24 h. The vaccine was highly immunogenic; all recipients developed neutralizing antibody that persisted for two years.

Adolescent↗

PubMed1996

Multicentre evaluation of dengue IgM dot enzyme immunoassay.

BACKGROUND: The traditional methods used in the diagnosis of dengue infection do not lend themselves to field application. As such, clinical specimens have to be sent to a central laboratory for processing which invariably leads to delay. This affects patient management and disease control. The development of the dengue IgM dot enzyme immunoassay has opened up the possibility of carrying out the test in peripheral health settings. OBJECTIVES: This multicentre study was conducted to evaluate a new, commercial nitrocellulose membrane based IgM capture enzyme immunoassay. STUDY DESIGN: The sensitivity and specificity of the test were compared with in-house dengue IgM enzyme-linked immunoassays routinely performed by each of the selected centres. Known positive and negative dengue specimens, as well as specimens from non-dengue cases, were included in the evaluation. RESULTS: Based on 402 specimens tested by the six centres, the sensitivity was 92.1% and specificity 88.1%, with an overall agreement of 92.8% when compared with IgM EIA assays performed on microplates. CONCLUSIONS: The results suggest that this commercial kit has a role to play in the diagnosis of dengue infection, especially in peripheral health settings.

Antibodies, Viral↗

PubMed1996

Dengue 3 virus distribution in the mosquito Aedes aegypti: an immunocytochemical study.

The dissemination of dengue (DEN) 3 virus in parenterally infected female Aedes aegypti mosquitoes was studied immunocytochemically. Antigen was first detected in fat body cells near the thoracic site of virus inoculation. The intussuscepted foregut, salivary glands and nervous tissue were the first major tissues infected. Nervous tissue appeared to be the primary site of amplification. Muscles, tracheae, Malphigian tubules and the posterior midgut did not become infected. The only part of the reproductive system to be infected was the calyx (71% of specimens 16-22 days post-infection) consistent with low rates of vertical transmission. After 7 days post-inoculation the salivary glands of 100% of the specimens examined were infected. Virus dissemination was slow and the most common sequence of infection following intrathoracic inoculation was as follows: thoracic fat body, intussuscepted foregut, salivary glands, cardial epithelium, thoracic ganglion, brain, compound eye, anterior midgut, intermediate midgut/anterior abdominal ganglia, and calyx/hindgut/posterior abdominal ganglia. Fat body and intussuscepted foregut tissues lost infections after 16 days post-inoculation.

Aedes↗

PubMed1996

Protective antibody after a 'one dollar' hepatitis B vaccine.

The seropositivity rate of anti-HBs after hepatitis B vaccines, "Hepavax B", a one-dollar per dose vaccine produced by Korean Green Cross Corporation, Korea which were widely distributed and used for the first few years in the National Expanded Program on Immunization in Thailand were assessed in children who regularly came for immunization at the Well Baby Clinic at the Children's Hospital between June to December 1994. The schedule for hepatitis B immunization is at birth, 2 and 6 months of age. The seropositivity rate of anti-HBs at 6 months after the last dose were 86.3% and 87.7% at 12 months which was comparable to the seropositivity rate after other more expensive hepatitis B vaccines at 2 years (88.1%). This result should convince people that a one-dollar hepatitis B vaccine, "Hepavax" is immunogenic and expected to be as effective as other expensive hepatitis B vaccines. The marked reduce in the cost of hepatitis B vaccines will enable us to prevent and ultimately control of worldwide hepatitis B infections in the future.

Costs and Cost Analysis↗

PubMed1996

Etiology of acute non-A, B, C hepatitis in Thai patients: preliminary study.

To better characterize the etiology of acute non-A, B, C hepatitis, 24 sera from 50 acute hepatitis without acute markers for hepatitis A, B, and C were examined for acute markers for the hepatitis E virus (HEV), cytomegalovirus (CMV), herpes simplex virus type 2 (HSV-2), and Epstein-Barr virus. Immunoglobulin M (IgM) specific for HEV, HSV-2, and CMV was detected using ELISA and total Ig specific to EBV was determined by standard indirect immunofluorescence. IgM to CMV was not observed in sera from any of the patients; whereas, IgM to HEV was detected in sera from 2 patients and IgM to HSV-2 was detected in 5 of 24 acute hepatitis patients. In addition, high titer of antibody was found in 2 of the patients. This results indicate that HSV-2 and HEV circulate in Thailand and are responsible for a small proportion of non-A, B, C hepatitis in Thailand.

Hepatitis Antibodies↗

PubMed1995

Viremia, fecal shedding, and IgM and IgG responses in patients with hepatitis E.

Viremia, fecal shedding and antibody responses to hepatitis E virus (HEV) infections are poorly understood. To better characterize HEV infections, these responses were examined in 67 patients with acute markers for hepatitis E who were admitted to the Infectious Disease Hospital in Kathmandu, Nepal in 1993. A single stool and multiple sera from each patient were examined using polymerase chain reaction to detect HEV RNA. Sera were also examined for antibodies to HEV. Viremia, fecal shedding, and IgM and IgG to HEV were detected in 93%, 70%, 79%, and 87% of 67 patients, respectively. Viremia or fecal shedding (or both) were detected in 14 patients from whom IgM and IgG to HEV were not detected. Viremia lasted at least 2 weeks in nearly all subjects and at least 39 days in 1 subject. Our results suggest that viremia is a common occurrence in patients infected with HEV.

Adolescent↗

PubMed1995

Short report: relative risk of hepatitis A and E among foreigners in Nepal.

Sera from two groups of patients in Nepal with acute hepatitis were examined for the presence of antibodies to the hepatitis A, B, C, and E viruses to determine the etiology of viral hepatitis. The first group consisted of 43 consecutive acute hepatitis patients presenting at a clinic for tourists and foreign residents in Kathmandu from January 1987 to June 1988. The other group consisted of 95 consecutive acute hepatitis patients admitted during the same period at a hospital used predominantly by adult Nepalese residents of Kathmandu. Hepatitis A was diagnosed in 39 (91%) of the foreign patients and in one of the 95 Nepalese patients, whereas hepatitis E was diagnosed in four of the 43 foreign patients and in 90 (95%) of the Nepalese patients. No cases of hepatitis B or C were identified in either group, nor were any cases of dual infection with the hepatitis A virus (HAV) and hepatitis E virus (HEV) identified. These results suggest that in the Kathmandu Valley, hepatitis A is the predominant form of hepatitis among foreigners, hepatitis E is the predominant form of hepatitis among adult Nepalese, and both HAV and HEV are endemic to the Kathmandu Valley.

Enzyme-Linked Immunosorbent Assay↗

PubMed1995

Detection of hepatitis E virus infections among domestic swine in the Kathmandu Valley of Nepal.

The prevalence of hepatitis E virus (HEV) infections among 55 domestic swine living in the Kathmandu Valley of Nepal was investigated. Sera and stool specimens were collected from 47 free-roaming swine and examined for the presence of HEV genomic sequences by the reverse transcription-polymerase chain reaction. Sera from these animals, as well as sera from eight other swine, were also examined for the presence of HEV-specific antibodies by an enzyme-linked immunosorbent assay and by a fluorescent antibody blocking assay. Hepatitis E virus RNA was detected in the sera and/or stool of three of 47 swine, while HEV-specific antibodies were detected in 18 of 55 swine. These results indicate that HEV is a zoonotic virus, and that swine are among its natural hosts.

Adolescent↗

PubMed1995

Age-specific prevalence of hepatitis A antibody in Thai children.

Age-specific prevalence of anti-HAV was determined for 3 groups of children whose mean ages were 12.6, 20.7 and 52.5 months. There were 41, 43 and 99 children in the respective age groups. All children were healthy, from middle to low socioeconomic families in Bangkok and vicinity. None of the children in the two younger age groups had anti-HAV antibody while 2 of 99 children in the oldest age group did. One of them resided in central Bangkok (Amphoe Dusit) and the other in Nonthaburi Province. The overall prevalence of anti-HAV in children under 5 years old was 1.1%. This demonstrates that hepatitis A transmission rates in Bangkok are very low when compared to ten years ago when prevalence rates were as high as 50-65%. From this study hepatitis A vaccine is recommended for 4-5 years old children in Bangkok. We need more epidemiologic data concerning hepatitis A transmission in Thailand before we can consider hepatitis A immunization for the whole country.

Age Distribution↗

PubMed1994

Quantitative relationship between oral temperature and severity of illness following inoculation with candidate attenuated dengue virus vaccines.

The relationship between oral temperature and other parameters of illness was examined in 51 adult volunteers who were inoculated experimentally with partially attenuated candidate dengue virus vaccines. In subjects who developed clinical illness, the peak illness temperature, mean illness temperature, and peak 6:00 A.M. illness temperature all correlated positively with the total number of signs and symptoms other than fever and with a fall in the white blood cell count (the latter was the only laboratory abnormality significantly associated with clinical illness [P = .02]). Of these factors, the peak 6:00 A.M. oral temperature exhibited the strongest correlations with the two parameters used to estimate severity of illness (rxy = .58 and P < .01 for signs and symptoms; rxy = .37 and P = .01 for fall in white blood cell count).

Adolescent↗

PubMed1994

Dengue virus-specific memory T cell responses in human volunteers receiving a live attenuated dengue virus type 2 candidate vaccine.

A live attenuated dengue virus type 2 candidate vaccine (16681-PDK53) was evaluated in a phase I trial in 10 nonimmune adult volunteers. The dengue virus-specific memory T cell responses were analyzed as part of this study. Dengue virus-specific T cell proliferative responses were observed in all subjects after stimulating their peripheral blood mononuclear cells with live viruses or noninfectious viral antigens. The highest proliferative response was against dengue virus type 2, although cross-reactivity with other flaviviruses was detected to a lesser degree in some subjects. Dengue virus type 2-specific CD4+ and CD8+ cytotoxic T lymphocytes were generated in all vaccinees. This study investigated whether the candidate vaccine was efficacious in inducing dengue virus-specific CD4+ and CD8+ T cell memory after a single immunization in nonimmune recipients.

Adult↗