Biomedical subjects

B L Innis

Publications and source records attributed to B L Innis.

At least 55 records · Page 3Linked to original sources

PubMed1997

Dengue in the early febrile phase: viremia and antibody responses.

A multicenter effort was begun in 1994 to characterize the pathophysiology of dengue using a study design that minimized patient selection bias by offering enrollment to all children with undifferentiated fever for <72 h. In the first year, 189 children were enrolled (age range, 8 months to 14 years). Thirty-two percent of these children had dengue infections (60 volunteers). The percentage of children with a secondary dengue infection was 93%, with only 4 (7%) having a primary dengue infection. The virus isolation rate from the plasma of children with dengue was 98%. Viremia correlated highly with temperature. All four dengue virus serotypes were isolated at both study sites. This study demonstrates that all four serotypes of dengue virus can cause dengue hemorrhagic fever, that all dengue patients as defined by serology experience viremia during the febrile phase, and that as fever subsides, so does viremia.

Acute Disease↗

PubMed1997

Rates of hepatitis E virus infection and disease among adolescents and adults in Kathmandu, Nepal.

To determine hepatitis E virus (HEV) infection and disease rates in the Kathmandu Valley of Nepal, serum was collected from 757 healthy Nepalese (ages 12-48 years) during March and September 1992 and September 1993. At each visit, reports of interval illness were obtained. Sera were examined for IgG to HEV, using a commercially available kit. Seroconversion was used as a marker for HEV infection, and an episode of hepatitis E was defined as a history of jaundice with seroconversion. Seroprevalence ranged from 16% to 31% and increased with age, whereas both infection and disease rates decreased with age. Infection and disease rates were as high as 99/1000 and 45/1000 person-years, respectively. These results highlight the importance of sporadic hepatitis E as a public health problem among adolescents and young adults in this region.

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

A cluster of acute hepatitis E infection in United Nations Bangladeshi peacekeepers in Haiti.

In the fall of 1995, within a month of deployment to Haiti for peacekeeping duty, four Bangladeshi soldiers developed acute icteric hepatitis in rapid succession. Hepatitis E virus (HEV) was found to be the etiology by demonstrating HEV genomic sequences in serum samples by the polymerase chain reaction (PCR) and serologically by the detection of elevated IgM titers to HEV. No case had serologic evidence of acute hepatitis A or C infection. The soldiers had probably acquired their infection while living in a cantonment area outside Dhaka, Bangladesh for one month prior to deployment. Cloning and sequencing of amplified PCR products demonstrated a single strain suggestive of a common source of infection. Furthermore, high genomic identity with Asian strains of HEV and dissimilarity with the Mexican strain was demonstrated, verifying that the strain had indeed been imported. Human waste management from the Bangladesh camp in Haiti was strictly controlled and no secondary cases were observed. A convenience sample of 105 (12%) soldiers from the Bangladesh battalion (850 men) revealed anicteric or asymptomatic HEV infection in seven (7%) of 105. This report contains the first demonstration of acute hepatitis E in natives of Bangladesh and demonstrates the power of the PCR in the rapid diagnosis and epidemiologic analysis of HEV infection. More importantly, this cluster demonstrates the importation of an important infectious disease by multinational peacekeepers to a potentially susceptible host country.

Acute Disease↗

PubMed1996

Experimental infection of the laboratory rat with the hepatitis E virus.

To confirm an earlier report that laboratory rats are susceptible to infection with the hepatitis E virus (HEV), we inoculated 27 Wistar rats intravenously with a suspension of a human stool known to contain infectious HEV. Stool, sera, and various tissues were collected from three rats each on days 0 (preinoculation) and 4, 7, 11, 14, 18, 21, 25, 28, and 35 postinoculation. Stool and sera specimens were examined by reverse transcription-polymerase chain reaction for the presence of HEV genomic sequences. Tissues were examined by light microscopy for detection of histopathological changes and by direct immunofluorescence for detection of HEV antigens. We detected HEV RNA in stools on day 7 in all three animals and in serum intermittently between days 4 and 35. We found HEV antigens in liver, peripheral blood mononuclear cells, spleen, mesenteric lymph nodes, and small intestine. We detected histopathology attributable to the inoculum in liver, spleen, and lymph nodes. The results confirm that HEV can replicate in laboratory rats and suggest new tissue sites for HEV replication.

Adult↗

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

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↗

PubMed1995

Antibody-enhanced binding of dengue-2 virus to human platelets.

The mechanisms underlying severe thrombocytopenia in dengue hemorrhagic fever/dengue shock syndrome (DHF/DSS) are not completely understood. We present here the first evidence that dengue type 2 virus binds to human platelets only in the presence of virus-specific antibody, supporting a role for immune-mediated clearance of platelets in the pathogenesis of thrombocytopenia in DHF/DSS. Antibody-enhanced binding of virus of platelets was also demonstrated with a panel of eight murine monoclonal antibodies specific for the dengue E protein. The degree of binding was dependent on the antibody used but not on the antibody IgG subclass, indicating that factors other than the platelet Fc receptor are involved in binding of virus-antibody complexes to the platelet surface. Confirmation that antibody-dependent virus binding to platelets is not primarily mediated by the platelet Fc receptor was obtained by demonstrating good binding even when platelets were pretreated with the Fc gamma RII-specific antibody IV.3.

Animals↗

PubMed1995

Antibodies that block virus attachment to Vero cells are a major component of the human neutralizing antibody response against dengue virus type 2.

Epidemiological data strongly implicate a role for the host humoral immune response in both protection against and exacerbation of dengue virus-caused disease. In an effort to characterize elements of the normal human immune response against dengue virus we have addressed the issue of antibody-mediated neutralization of dengue virus. We show here the ability of both mouse monoclonal antibody 3H5 and human anti-dengue neutralizing sera to block binding of dengue-2 virus to monkey kidney (Vero) cells. Since Vero cells possess virus receptors but not Fc receptors we conclude that the major effect of host neutralizing antibodies is to block virus attachment to Vero cell dengue virus receptors. Analysis of 61 patient antisera yielded good correlation (Pearson's coefficient = 0.90; P < 0.001) between neutralizing activity and ability to block virus-cell attachment suggesting that antibody-mediated neutralization of dengue virus occurs primarily extracellularly and less by a postattachment mechanism as has been described for certain other viruses.

Adolescent↗

PubMed1995

Mechanisms of dengue virus-induced bone marrow suppression.

Infection with many flaviviruses is associated with transient suppression of haematopoiesis. Of the flaviviruses of man, none are more accessible to clinical and laboratory study than dengue. Consequently, the clinical syndrome of dengue-associated bone marrow suppression has been well documented. A review of experimental dengue infections of volunteers and histopathological studies of bone marrow from patients with severe dengue virus infection suggests that marrow suppression evolves rapidly through several phases: (1) onset of marrow suppression within 3-4 days of infection; (2) onset of host inflammatory responses in the marrow and of fever shortly thereafter; (3) occurrence of a neutrophil nadir on the fourth to fifth day after onset of fever; (4) almost simultaneously, immune activation sufficient to neutralize viraemia and accelerate elimination of infected cells; (5) remission of symptoms; and (6) resolution of cytopenias. Clinical observations and experimental data bear on possible mechanisms of dengue virus-mediated marrow suppression. Work from the authors' laboratory in which long-term bone marrow cultures were used to investigate interactions between dengue virus and bone marrow cells (stromal elements and haematopoietic progenitors) is also reviewed. Long-term marrow culture (LTMC) was a useful experimental system. In vitro, early blast cells as well as the more differentiated haematopoietic elements were abortively infected, killed and eliminated by phagocytosis by specialized marrow macrophages called dendritic cells. Moreover, the ARC from stroma rather than haematopoietic precursors were productively infected. When ARC were infected, stroma failed to support haematopoiesis. Cytokine production by virus-infected stromal cells was altered. A hypothesis is proposed to account for dengue virus-induced marrow suppression. Down-regulation of haematopoiesis is probably a protective mechanism of the microenvironment that limits injury to the marrow stem/progenitor cell compartment during the subsequent process of elimination of infected cells.

Bone Marrow↗

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

Japanese encephalitis virus-specific proliferative responses of human peripheral blood T lymphocytes.

The T lymphocytes play an important role in prevention and recovery from viral infections. To characterize T lymphocyte responses to Japanese encephalitis (JE) virus infections, we analyzed JE virus-specific T lymphocytes in peripheral blood mononuclear cells (PBMC) obtained from seven JE patients and 10 vaccinees who had received a formalin-inactivated, purified JE virus vaccine (Biken vaccine). These PBMC were examined for proliferative responses against live JE virus, a glutaraldehyde-fixed lysate of cells infected with JE virus, and extracellular particles (EPs; subviral membrane vesicles released from cells infected with recombinant vaccinia viruses encoding the JE virus premembrane and envelope proteins). Japanese encephalitis virus-specific T cell proliferation was demonstrated with PBMC from both patients and vaccinees after stimulation with infectious JE virus or the lysate of JE virus-infected cells. Proliferating PBMC included CD4+ T lymphocytes and CD8+ T lymphocytes in responses to either form of JE viral antigens. Responses to EPs were observed only with PBMC from some American vaccinees whose PBMC also responded to the virus and lysate. These results indicate that JE virus infection and immunization with an inactivated JE vaccine induce JE virus-specific CD4+ and CD8+ T memory lymphocytes that can be induced to proliferate by infectious JE virus and noninfectious JE antigens.

Antibodies, Viral↗

PubMed1995

T cell activation in vivo by dengue virus infection.

It is accepted that T cells play a critical role during virus infections; however, T cell responses in vivo in acute stage of virus infection are not understood. We examined T cell activation in vivo in two volunteers who developed dengue fever in response to vaccination with a candidate live dengue vaccine. Serial plasma collected from the volunteers from day 0 (before infection) to day 17 after infection were examined for levels of soluble interleukin-2 receptor (sIL-2R), soluble CD4 (sCD4), soluble CD8 (sCD8), interleukin-2 (IL-2) and interferon gamma (INF gamma). Elevation of the levels of sIL-2R, IFN gamma, sCD4 and IL-2 became obvious during the period of viremia and was followed by a later increase in the level of sCD8. The levels of IFN gamma and sIL-2R declined after the end of the period of viremia. These results indicate that i. T cells are activated in vivo by dengue virus infection ii. activation of CD4+ T cells occurs during the period of viremia iii. activation of CD8+ T cells follows CD4+ T cell activation. These results suggest that activation of T cells in vivo may contribute to controlling acute dengue virus infections.

Adult↗

PubMed1994

Protection against hepatitis A by an inactivated vaccine.

OBJECTIVE: To evaluate the safety and efficacy of a new inactivated hepatitis A vaccine. DESIGN: Double-blind randomized controlled trial stratified by community. SETTING: Community-based in Thailand. STUDY PARTICIPANTS: A total of 40,119 children, aged 1 to 16 years, attending 148 primary schools: 38,157 (95%) entered surveillance a mean of 138 days after receiving vaccine dose 1; 33,586 (84%) completed the controlled trial of 532 days; and 31,075 (81%) received crossover vaccine and remained under surveillance until day 844. INTERVENTION: Participants received hepatitis A vaccine or control hepatitis B vaccine starting January 7, 1991 (doses in months 0, 1, and 12), and crossed over to the alternate vaccine 18 months later. MAIN OUTCOME MEASURE: Cases of hepatitis A (symptoms, alanine aminotransferase levels of 45 U/L or higher, and IgM to hepatitis A virus) were identified by evaluating school absences of 2 or more days. RESULTS: There were no serious adverse reactions despite administration of more than 109,000 doses of hepatitis A vaccine. Among initially seronegative recipients of two doses of hepatitis A vaccine, the proportion with 20 mIU/mL or more of antibody to hepatitis A virus before and 5 months after a 1-year booster was 94% and 99%, respectively. Of 6976 episodes of illness during the controlled trial, there were 40 cases of hepatitis A; 38 were in the control group. Of the 40 cases, six, all in controls, occurred after the 1-year booster dose. Following two doses of hepatitis A vaccine (days 138 through 386), protective efficacy was 94% (95% confidence interval, 79% to 99%); cumulative efficacy including the postbooster period (days 138 to 532) was 95% (95% confidence interval, 82% to 99%). The two hepatitis A vaccine recipients who had symptomatic infections (257 and 267 days after dose 1) appeared to have been partially protected since their illnesses were brief and associated with only slight increases in alanine aminotransferase. CONCLUSIONS: Inactivated hepatitis A vaccine is safe; when administered in two doses, it protects against hepatitis A for at least 1 year.

Adolescent↗

PubMed1994

Immunopathologic mechanisms of dengue hemorrhagic fever and dengue shock syndrome.

Dengue virus infections are a major cause of morbidity and mortality in tropical and subtropical areas of the world. The immunopathological mechanisms that result in severe complications of dengue virus infection, i.e. dengue hemorrhagic fever (DHF), are important to determine. Primary dengue virus infections induce serotype-specific and serotype-cross-reactive, CD4+ and CD8+ memory cytotoxic T lymphocytes (CTL). In secondary infections with a virus of a different serotype from that which caused primary infections, the presence of cross-reactive non-neutralizing antibodies results in an increased number of infected monocytes by dengue virus--antibody complexes. This in turn results in marked activation of serotype cross-reactive CD4+ and CD8+ memory CTL. We hypothesize that the rapid release of cytokines and chemical mediators caused by T cell activation and by CTL-mediated lysis of dengue virus-infected monocytes triggers the plasma leakage and hemorrhage that occurs in DHF.

Cross Reactions↗

PubMed1994

ELISA for detecting dengue and Japanese encephalitis viral antigen in mosquitoes.

An indirect ELISA has been developed for detecting two viruses in triturated, experimentally infected mosquitoes: dengue (DEN) in Aedes aegypti (L.) and Ae. albopictus (Skuse) and Japanese encephalitis (JE) viral antigen in Culex tritaeniorhynchus Giles. DEN antigen from four strains of the virus, representing each of the four serotypes, and JE antigen were captured with a polyclonal anti-flavivirus IgG and detected with a monoclonal antibody (4G2) that reacts with all flaviviruses. Minimum viral titres detectable by the flavivirus antigen-capture ELISA, measured as multiples of the dose infecting 50% of mosquitoes (MID50), were 10(6.4), 10(4.5), 10(6.3), 10(6.9) and < or = 10(6.9) MID50/ml for DEN 1, DEN 2, DEN 3, DEN 4 and JE, respectively. Pools of up to 100 larvae or adults of Ae. aegypti and Ae. albopictus did not reduce the sensitivity of the ELISA to DEN 1, 2, 3 or 4. The results indicate that the antigen-capture ELISA could readily screen for DEN antigen in individual and pooled mosquitoes.

Aedes↗