Strong HLA class I--restricted T cell responses in dengue hemorrhagic fever: a double-edged sword?

Dengue is an increasingly important cause of morbidity and mortality in the tropics, but vaccine development has been impeded by a poor understanding of disease pathogenesis and, in particular, of immunologic enhancement. In a large case-control study of Vietnamese patients with dengue hemorrhagic fever (DHF), variation at the HLA-A locus was significantly associated with susceptibility to DHF (P=.02), and specific HLA-A susceptibility and resistance alleles were identified. HLA-A-specific epitopes were predicted from binding motifs, and ELISPOT analyses of patients with DHF revealed high frequencies of circulating CD8 T lymphocytes that recognized both serotype-specific and -cross-reactive dengue virus epitopes. Thus, strong CD8 T cell responses are induced by natural dengue virus infection, and HLA class I genetic variation is a risk factor for DHF. These genetic and immunologic data support both protective and pathogenic roles for dengue virus-specific CD8 T cell responses in severe disease. The potentially pathogenic role of serotype-cross-reactive CD8 T cells poses yet another obstacle to successful dengue vaccine development.

Noninvasive measurement of microvascular leakage in patients with dengue hemorrhagic fever.

Dengue shock syndrome (DSS) is a potentially lethal complication of dengue virus infection associated with hypotension and leakage of plasma water into the extravascular space. To determine whether the underlying pathophysiology of DSS is distinct from that in milder forms of the disease, we assessed microvascular permeability, by use of strain gauge plethysmography, in Vietnamese children with DSS (n=19), or dengue hemorrhagic fever (DHF) without shock (n=16), and in healthy control children (n=15). At admission and after fluid resuscitation, the mean coefficient of microvascular permeability (K(f)) for the patients with dengue was approximately 50% higher than that for the control patients (P=.02). There was no significant difference in K(f) between the 2 groups of patients with dengue; this suggests the same underlying pathophysiology. We hypothesize that in patients with DSS, the fluctuations in K(f) are larger than those in patients with DHF, which leads to short-lived peaks of markedly increased microvascular permeability and consequent hemodynamic shock.

Effects of dopamine and epinephrine infusions on renal hemodynamics in severe malaria and severe sepsis.

OBJECTIVE: To describe and compare the effects of dopamine and epinephrine in various doses on renal hemodynamics and oxygen transport in patients with severe malaria and severe sepsis. DESIGN: Prospective, controlled, crossover trial. SETTING: The intensive care unit of an infectious diseases hospital in Viet Nam. PATIENTS: Fourteen patients with severe falciparum malaria and five with severe sepsis. INTERVENTIONS: In an open, crossover design, we observed the effects on renal and systemic hemodynamics and oxygen transport of separate stepped infusions of epinephrine and dopamine. We measured renal blood flow (RBF) and cardiac output by the thermodilution method using fluoroscopically guided catheters. Creatinine clearance at each time point was calculated from the renal plasma flow and the renal arteriovenous difference in plasma creatinine. MEASUREMENTS AND MAIN RESULTS: Dopamine at a "renal" dose (2.5 microg/kg/min) was associated with a mean (95% confidence interval) fractional increase in the absolute renal blood flow index (RBFI) of 37% (13% to 61%) and in RBF as a fraction of cardiac output (RBF/CO) of 35% (10% to 59%; p = .007 and p = .014, respectively). The consequent 39% (14% to 64%) increase in renal oxygen supply (p = .002) was accompanied by a 32% (20% to 44%) decrease in the renal oxygen extraction ratio (p = .0003), leading to no net change in renal oxygen consumption. At higher doses (10 microg/kg/min), both RBF and RBF/CO were not significantly different from baseline values and decreased further as the dose was reduced again. There was no obvious explanation for this hysteresis. There was no change in renal oxygen consumption throughout the study. Because lactic acidosis developed, epinephrine was only given to eight of the 19 patients, and the full stepped epinephrine infusion was given to four patients. Epinephrine infusion was associated, both in absolute terms and when compared with dopamine, with a significant increase in renal vascular resistance (p = .0008 and .0005, respectively), a decrease in RBF/CO (p = .002 and .03), and a compensatory increase in the renal oxygen extraction ratio (p = .005 and .0001). RBFI and renal oxygen consumption remained constant throughout the epinephrine infusion profile. Neither epinephrine nor dopamine significantly affected creatinine clearance or urine output. Twelve patients (63%) were in established renal failure (plasma creatinine, >3 mg/dL) at the time of the study, although the presence or absence of renal failure did not significantly influence the effects of the study drugs. However, overall, the presence of renal failure was associated with a lower mean renal oxygen consumption, a lower mean renal oxygen consumption as a fraction of systemic oxygen consumption, and a higher mean renal vascular resistance. CONCLUSION: Although dopamine increased and epinephrine decreased fractional renal blood flow, there was no evidence that either drug produced either a beneficial or a deleterious effect on renal oxygen metabolism or function at any of the doses investigated.

Fluid replacement in dengue shock syndrome: a randomized, double-blind comparison of four intravenous-fluid regimens.

Dengue hemorrhagic fever and dengue shock syndrome (DSS) are major causes of childhood morbidity and mortality in many tropical countries. Increased intravascular permeability leading to shock is the cardinal feature of DSS. Fluid resuscitation to counteract massive plasma leakage is the mainstay of treatment. A double-blind, randomized trial comparing four intravenous-fluid regimens for acute resuscitation of 50 children with DSS was conducted. Colloids (dextran 70 or the protein digest gelafundin 35,000) restored cardiac index and blood pressure and normalized hematocrit more rapidly than crystalloids (Ringer's lactate or 0.9%-weight/volume saline). Dextran 70 provided the most rapid normalization of the hematocrit and restoration of the cardiac index, without adverse effects, and may be the preferred solution for acute resuscitation in DSS. Further large-scale double-blind trials are required to provide an evidence-based approach to the management of DSS.

Pathophysiologic and prognostic role of cytokines in dengue hemorrhagic fever.

Dengue shock syndrome is a severe complication of dengue hemorrhagic fever (DHF), characterized by a massive increase in vascular permeability. Plasma cytokine concentrations were prospectively studied in 443 Vietnamese children with DHF, of whom 6 died. Shock was present in 188 children on admission to hospital, and in 71 children it developed later. Contrary to expectations, certain inflammatory markers (interleukin-6 and soluble intercellular adhesion molecule-1) were lower in the group with shock, and this may reflect the general loss of protein from the circulation due to capillary leakage. Only soluble tumor necrosis factor receptor (TNFR) levels showed a consistent positive relationship with disease severity. In patients with suspected DHF without shock, admission levels of sTNFR-75 in excess of 55 pg/mL predicted the subsequent development of shock, with a relative risk of 5.5 (95% confidence interval, 2.3-13.2). Large-scale release of soluble TNFR may be an early and specific marker of the endothelial changes that cause dengue shock syndrome.

Comparison of artemisinin suppositories, intramuscular artesunate and intravenous quinine for the treatment of severe childhood malaria.

Severe malaria remains a major cause of mortality and morbidity for children living in many tropical regions. With the emergence of strains of Plasmodium falciparum resistant to both chloroquine and quinine, alternative antimalarial agents are required. The artemisinin group of compounds are rapidly effective in severe disease when given by intramuscular or intravenous injection. However, these routes of administration are not always available in rural areas. In an open, randomized comparison 109 Vietnamese children, aged between 3 months and 14 years, with severe P.falciparum malaria, were allocated at random to receive artemisinin suppositories followed by mefloquine (n = 37), intramuscular artesunate followed by mefloquine (n = 37), or intravenous quinine followed by pyrimethamine/sulfadoxine (n = 35). There were 9 deaths: 2 artemisinin, 4 artesunate and 5 quinine-treated children. There was no difference in fever clearance time, coma recovery, or length of hospital stay among the 3 groups. However, parasite clearance times were significantly faster in artemisinin and artesunate-treated patients than in those who received quinine (P < 0.0001). Both artemisinin and artesunate were very well tolerated, but children receiving these drugs had lower peripheral reticulocyte counts by day 5 of treatment than those in the quinine group (P = 0.011). No other adverse effect or toxicity was found. There was no treatment failure in these 2 groups, but 4 patients in the quinine group failed to clear their parasites within 7 d of starting treatment and required alternative antimalarial therapy. Artemisinin suppositories are easy to administer, cheap, and very effective for treating children with severe malaria. In rural areas where medical facilities are lacking these drugs will allow antimalarial therapy to be instituted earlier in the course of the disease and may therefore save lives.

Pharmacokinetics of oral artesunate in children with moderately severe Plasmodium falciparum malaria.

The pharmacokinetic properties of oral artesunate (3 mg/kg) were determined in 10 Vietnamese children, aged from 6 to 15 years, with acute falciparum malaria of moderate severity. Plasma concentrations were measured using a bioassay and expressed in terms of antimalarial activity equivalent to dihydroartemisinin, the principal biologically active metabolite. Oral artesunate was absorbed rapidly with a mean time to peak plasma bioactivity of 1.7 h (95% confidence interval [95% CI] 0.8-2.6). There was wide variation in peak plasma concentrations with a mean value equivalent to 664 ng of dihydroartemisinin/mL (95% CI 387-9410, range 179-1395) and a four-fold variation in the area under the plasma concentration-time curves. Elimination from plasma was rapid with a mean (95% CI) half-life of 1.0 h (95% CI 0.8-1.4). Plasma antimalarial levels were below the limit of detection in all cases by 12 h, despite the relatively high dose of artesunate used. Oral artesunate is rapidly absorbed and rapidly eliminated in children with moderately severe malaria but there is considerable variation between individuals.

Blackwater fever in southern Vietnam: a prospective descriptive study of 50 cases.

We prospectively studied 50 Vietnamese patients with blackwater fever (BWF). All patients had fever and hemoglobinuria, 40 (80%) were jaundiced, 25 (50%) had hepatomegaly, 15 (34%) had splenomegaly, and 9 (18%) had hepatosplenomegaly. Twenty-one patients (42%) had impaired renal function, with creatinine clearances of < 50 mL/min/m2; however, only four (8%) developed oliguric renal failure, three (6%) of whom required dialysis. Forty-four patients (88%) developed anemia, which was severe (hematocrit, < 20% in 32 (64%). One patient died, representing a death rate for this once-feared disease that is considerably lower than that reported by earlier investigators. BWF was associated with quinine ingestion in 28 patients (56%), glucose-6-phosphate dehydrogenase (G6PD) deficiency in 27 (54%), and concurrent malaria infection in 16 (32%). There was no statistically significant difference in the severity of BWF associated with each of these three factors, as assessed by creatinine clearance and the hematocrit value on admission and by the number of units of blood transfused. There was considerable overlap in the occurrence of G6PD deficiency, quinine ingestion, and malaria, suggesting that these factors may interact and that it may not be justifiable to regard hemoglobinuria caused by G6PD deficiency as a separate syndrome.

Clearance kinetics of parasites and pigment-containing leukocytes in severe malaria.

In tropical areas, where unsupervised use of antimalarial drugs is common, patients with an illness consistent clinically with severe malaria but with negative blood smears pose a management dilemma. Malaria pigment is evident in peripheral blood leukocytes in greater than 90% of patients with severe malaria. To characterize the clearance kinetics of parasitized erythrocytes and malaria pigment-containing leukocytes, sequential peripheral blood and intradermal smears were assessed in 27 adult Vietnamese patients with severe falciparum malaria. The clearance of parasitized erythrocytes and pigment-containing monocytes (PCMs) followed first order kinetics. The elimination of pigment-containing neutrophils (PCNs) was first order initially, but deviated from this when counts were low. Clearance of peripheral blood PCMs (median clearance time, 216 hours; range, 84 to 492 hours) was significantly slower than that of parasitized erythrocytes (median, 96 hours; range, 36 to 168 hours) or PCNs (median, 72 hours; range, 0 to 168 hours; P < .0001). Intradermal PCM clearance times were the longest of all (median, 12 days; range, 6 to 23 days; significantly longer than peripheral blood PCM clearance, P < .001). Twenty-one (88%) patients still had signs, symptoms, or laboratory features of severe malaria after parasite clearance but before phagocyte pigment clearance. Sixteen of the 23 surviving patients (70%; 95% confidence interval, 50% to 87%) still had intraleukocytic malaria pigment on peripheral blood films 72 hours after parasite clearance. Thus, by determining the distribution of malaria pigment in peripheral blood and intradermal phagocytes, the time since effective antimalarial treatment started can be estimated. Microscopy for intraleukocytic pigment is valuable in the differential diagnosis of severe febrile illnesses in malarious areas where uncontrolled use of antimalarial drugs is widespread.

Post-malaria neurological syndrome.

BACKGROUND: Neurological signs and symptoms are common in malaria, but observations in Vietnam and Thailand have pointed to a discrete transient neurological syndrome after recovery from severe infections. METHODS: A prospective study of the post-malaria neurological syndrome (PMNS) was conducted at two centres in Vietnam over four years. Criteria for inclusion were recent symptomatic malaria infection with parasites cleared from blood (and in cases of cerebral malaria full recovery of consciousness), and development of neurological or psychiatric symptoms within two months after the acute illness. Half of the patients with severe falciparum malaria had been taking part in a randomised trial of antimalarials. FINDINGS: Of 18,124 patients with falciparum malaria treated (1176 of whom had severe infections) 19 adults and three children had subsequent PMNS; in one patient it followed uncomplicated malaria and in 21 it followed severe malaria. The overall incidence (95% confidence interval) of PMNS after falciparum malaria at the main study centre was 1.2 per 1000 (0.7 to 1.8 per 1000) and relative risk (95% CI) for developing PMNS after severe versus uncomplicated falciparum malaria was 299 (40 to 2223). 13 patients had an acute confusional state or psychosis, six had one or more generalised convulsions, two had generalised convulsions followed by a long period of acute confusion, and one developed a fine tremor. At the time of PMNS diagnosis all patients were aparasitaemic. The syndrome was self-limiting, median duration 60 h (range 24-240). PMNS was associated with the use of oral mefloquine. In the randomised trial 4.4% (10/228) of patients with severe malaria who received mefloquine after parenteral treatment developed PMNS compared with 0.5% (1/210) of those who received quinine; relative risk 9.2 (95% CI 1.2 to 71.3, p = 0.012). INTERPRETATION: Mefloquine is not the only risk factor for PMNS but it is a strong one. Where an effective alternative drug is available, mefloquine should not be used after treatment of severe malaria.

Pharmacokinetics of oral and intravenous ofloxacin in children with multidrug-resistant typhoid fever.

The pharmacokinetics of oral and intravenous ofloxacin (7.5 mg.kg of body weight-1 given over 30 min) were studied in an open crossover study of 17 Vietnamese children, aged between 5 and 14 years, with acute uncomplicated typhoid fever. Following oral administration, the median (95% confidence interval [CI]) time to peak concentration of ofloxacin in serum (Cmax) was 1.7 h (1.4 to 1.9 h) and the mean (95% CI) Cmax was 5.5 mg.liter-1 (4.7 to 6.3 mg.liter-1) compared with a Cmax of 8.7 mg.liter-1 (7.6 to 9.7 mg.liter-1) following the intravenous infusion. The median (95% CI) total apparent volume of distribution following the first intravenous dose, 1.35 liter.kg-1 (1.17 to 1.73 liter.kg-1), was significantly larger than that following the second dose, 0.99 liter.kg-1 (0.86 to 1.17 liter.kg-1; P < 0.0005), although the estimates for systemic clearance were similar: 0.255 liter.kg-1 h-1 (0.147 to 0.325 liter.kg-1 h-1) compared with 0.172 liter.kg-1 h-1 (0.127 to 0.292 liter.kg-1 h-1; P = 0.14). The mean residence times (95% CI) following intravenous and oral administration were similar: 5.24 h (4.84 to 6.58 h) and 6.24 h (5.32 to 7.85 h), respectively. The mean (95% CI) oral bioavailability was 91% (74 to 109%). The peak concentrations in serum were 10 to 100 times higher than the maximum MICs for ofloxacin against multidrug-resistant Salmonella typhi isolated in this area. Although the systemic clearance values were higher than those reported previously for adults, these data overall suggest that weight-or area-adjusted dose regimens for the treatment of typhoid in older children should be the same as those for adults.

Electrocardiographic monitoring in severe falciparum malaria.

Electrocardiographic monitoring over 24 h was performed with 53 patients with severe Plasmodium falciparum malaria (11 adults and 42 children) to assess the frequency of unrecognized cardiac arrhythmias. Nine patients (17%) died, 5 during the monitoring period and 4 afterwards. Pauses lasting 2-3 s were observed in 3 children, a single couplet in one, and a further child experienced frequent supraventricular ectopic beats which had not been detected clinically. In none of the patients who died could death be attributed to cardiac arrhythmia. Furthermore, no abnormality was detected which could have resulted from the often large doses of quinine, chloroquine or the artemisinin derivatives used for treatment. These results suggest that the heart is remarkably resilient even in the face of heavy parasite sequestration and other vital organ dysfunction, and that deaths from cardiac arrhythmias in severe malaria are rare. The need for routine cardiac monitoring of patients with severe and complicated P. falciparum malaria is questionable.

Effects on growth of single short courses of fluoroquinolones.

The aim of the study was to document the effects of short courses of fluoroquinolones given during an outbreak of multidrug resistant typhoid fever in southern Viet Nam on the growth of children over a period of two years. In a prospective cohort study, 326 Vietnamese children aged between 1 and 14 years were followed up for two years after receiving either ciprofloxacin (70 mg/kg given over 7 d) (n = 173) or ofloxacin (45-50 mg/kg given over 3-5 d) (n = 153) for suspected typhoid fever. Growth velocity and weight for height were compared with an age matched control group of children from the same locality (n = 223) who had not contracted typhoid or received any fluoroquinolones. In the ofloxacin and ciprofloxacin treated patients there was no evidence of acute joint toxicity, nor of any joint symptoms attributable to either of the fluoroquinolones. There was no difference in expected weight for height measurements between the three groups of children over the two year period. During the first year, height velocity in ciprofloxacin treated children was greater than in either ofloxacin treated children or untreated controls. Height velocity in the latter two groups was not significantly different. After two years height velocity was similar in the three groups. The results support the use of short course fluoroquinolone treatment in childhood typhoid, especially when caused by strains resistant to other antibiotics.

Prognostic value of electrocardiographic monitoring of patients with severe diphtheria.

The clinical, the 12-lead, and the 24-hour electrocardiographic findings in 15 consecutively studied Vietnamese children (aged 7 months to 16 years) with severe diphtheria were documented. Five patients died, three from respiratory arrest and two from cardiogenic shock; one of these two patients had complete heart block that necessitated insertion of a pacemaker. Electrocardiographic abnormalities were detected by 24-hour monitoring in all 15 cases, even though most patients had no clinical signs of myocarditis. Rates of supraventricular and ventricular ectopy were elevated and remained high long after other clinical manifestations were no longer noted. The degree of ventricular ectopy at the time of presentation was significantly associated with fatal outcome. In this series, more than two ventricular ectopic beats on a recording upon admission to the hospital predicted fatal outcome with 100% sensitivity and 100% specificity. A variety of nonsustained bradyarrhythmias and tachyarrhythmias were also observed up until discharge from the hospital. The time course of recovery from diphtheritic myocarditis is longer than has been appreciated previously.

Short course of ofloxacin for treatment of multidrug-resistant typhoid.

In recent years, multiresistant strains of Salmonella typhi have emerged in many tropical countries. These strains remain highly sensitive to the fluoroquinolone antibiotics, although use of these drugs by children is considered contraindicated because of their reported toxicity in the cartilage of experimental animals. In a paired, open, randomized study during an epidemic of multidrug-resistant typhoid in southern Vietnam, two short-course ofloxacin regimens (15 mg/kg daily for 3 days and 10 mg/kg daily for 5 days) were compared for the treatment of uncomplicated typhoid fever. Of 438 patients enrolled (of whom 286 were < or = 14 years old), 228 had blood cultures positive for Salmonella species (S. typhi, 207; S. paratyphi A, 19; and S. choleraesuis, 2). There was one treatment failure in a patient who took only one dose of ofloxacin. Otherwise, both regimens were completely effective; there were no proven carriers, and there was no evidence of toxicity, particularly in children. A 3-day course of ofloxacin proved to be safe and highly effective in the treatment of uncomplicated, multidrug-resistant typhoid fever.

Role of quinine in the high mortality of intramuscular injection tetanus.

There has been considerable uncertainty about the risks and severity of tetanus after intramuscular quinine, a widely used treatment of severe malaria in the rural tropics. We have compared the clinical features and outcome of tetanus in which injection was the only apparent site of infection with tetanus acquired by other routes in patients admitted to the Centre for Tropical Diseases, Ho Chi Minh City, Vietnam. In 1081 consecutive patients with tetanus treated between Jan 26, 1989, and May 27, 1991, 27 followed intramuscular quinine and 15 followed injections of other drugs. Overall mortality was 26% (285/1081). Mortality in patients who had not had preceding injections was 24% (250/1039) compared with 96% (26/27) in the quinine group (relative risk 4.0, 95% CI 3.5-4.6) (p < 0.0001), and 60% (9/15) in the other injections group (2.5, 1.6-3.8) (p < 0.005). 21 patients (78%) in the quinine group died within 72 h of admission compared with 5 (33%) in the other intramuscular injections group (p < 0.01) and 4 (7%) of 54 matched controls (p < 0.0001). Tetanus that follows intramuscular injections has a poor prognosis, but when it follows intramuscular quinine it is usually rapidly fatal.