Andre van der Ven

Protection against a Malaria Challenge by Sporozoite Inoculation

BACKGROUND An effective vaccine for malaria is urgently needed. Naturally acquired immunity to malaria develops slowly, and induction of protection in humans can be achieved artificially by the inoculation of radiation-attenuated sporozoites by means of more than 1000 infective mosquito bites. METHODS We exposed 15 healthy volunteers--with 10 assigned to a vaccine group and 5 assigned to a control group--to bites of mosquitoes once a month for 3 months while they were receiving a prophylactic regimen of chloroquine. The vaccine group was exposed to mosquitoes that were infected with Plasmodium falciparum, and the control group was exposed to mosquitoes that were not infected with the malaria parasite. One month after the discontinuation of chloroquine, protection was assessed by homologous challenge with five mosquitoes infected with P. falciparum. We assessed humoral and cellular responses before vaccination and before the challenge to investigate correlates of protection. RESULTS All 10 subjects in the vaccine group were protected against a malaria challenge with the infected mosquitoes. In contrast, patent parasitemia (i.e., parasites found in the blood on microscopical examination) developed in all five control subjects. Adverse events were mainly reported by vaccinees after the first immunization and by control subjects after the challenge; no serious adverse events occurred. In this model, we identified the induction of parasite-specific pluripotent effector memory T cells producing interferon-gamma, tumor necrosis factor alpha, and interleukin-2 as a promising immunologic marker of protection. CONCLUSIONS Protection against a homologous malaria challenge can be induced by the inoculation of intact sporozoites. (ClinicalTrials.gov number, NCT00442377.)

Antituberculosis drug‐induced hepatotoxicity: Concise up‐to‐date review

The cornerstone of tuberculosis management is a 6‐month course of isoniazid, rifampicin, pyrazinamide and ethambutol. Compliance is crucial for curing tuberculosis. Adverse effects often negatively affect the compliance, because they frequently require a change of treatment, which may have negative consequences for treatment outcome. In this paper we review the incidence, pathology and clinical features of antituberculosis drug‐induced hepatotoxicity, discuss the metabolism and mechanisms of toxicity of isoniazid, rifampicin and pyrazinamide, and describe risk factors and management of antituberculosis drug‐induced hepatotoxicity. The reported incidence of antituberculosis drug‐induced hepatotoxicity, the most serious and potentially fatal adverse reaction, varies between 2% and 28%. Risk factors are advanced age, female sex, slow acetylator status, malnutrition, HIV and pre‐existent liver disease. Still, it is difficult to predict what patient will develop hepatotoxicity during tuberculosis treatment. The exact mechanism of antituberculosis drug‐induced hepatotoxicity is unknown, but toxic metabolites are suggested to play a crucial role in the development, at least in the case of isoniazid. Priorities for future studies include basic studies to elucidate the mechanism of antituberculosis drug‐induced hepatotoxicity, genetic risk factor studies and the development of shorter and safer tuberculosis drug regimens.

TLR4 polymorphisms, infectious diseases, and evolutionary pressure during migration of modern humans.

Infectious diseases exert a constant evolutionary pressure on the genetic makeup of our innate immune system. Polymorphisms in Toll-like receptor 4 (TLR4) have been related to susceptibility to Gram-negative infections and septic shock. Here we show that two polymorphisms of TLR4, Asp299Gly and Thr399Ile, have unique distributions in populations from Africa, Asia, and Europe. Genetic and functional studies are compatible with a model in which the nonsynonymous polymorphism Asp299Gly has evolved as a protective allele against malaria, explaining its high prevalence in subSaharan Africa. However, the same allele could have been disadvantageous after migration of modern humans into Eurasia, putatively because of increased susceptibility to severe bacterial infections. In contrast, the Asp299Gly allele, when present in cosegregation with Thr399Ile to form the Asp299Gly/Thr399Ile haplotype, shows selective neutrality. Polymorphisms in TLR4 exemplify how the interaction between our innate immune system and the infectious pressures in particular environments may have shaped the genetic variations and function of our immune system during the out-of-Africa migration of modern humans.

Long-term protection against malaria after experimental sporozoite inoculation: an open-label follow-up study

BACKGROUND We have shown that immunity to infection with Plasmodium falciparum can be induced experimentally in malaria-naive volunteers through immunisation by bites of infected mosquitoes while simultaneously preventing disease with chloroquine prophylaxis. This immunity was associated with parasite-specific production of interferon γ and interleukin 2 by pluripotent effector memory cells in vitro. We aim to explore the persistence of protection and immune responses in the same volunteers. METHODS In an open-label study at the Radboud University Nijmegen Medical Centre (Nijmegen, Netherlands), from November to December, 2009, we rechallenged previously immune volunteers (28 months after immunisation) with the bites of five mosquitoes infected with P falciparum. Newly recruited malaria-naive volunteers served as infection controls. Our primary outcome was the detection of blood-stage parasitaemia by microscopy. We assessed the kinetics of parasitaemia with real-time quantitative PCR (rtPCR) and recorded clinical signs and symptoms. In-vitro production of interferon γ and interleukin 2 by effector memory T cells was studied after stimulation with sporozoites and red blood cells infected with P falciparum. Differences in cellular immune responses between the study groups were assessed with the Mann-Whitney test. This study is registered with ClinicalTrials.gov, number NCT00757887. FINDINGS Four of six immune volunteers were microscopically negative after rechallenge. rtPCR-based detection of blood-stage parasites in these individuals was negative throughout follow-up. Patent parasitaemia was delayed in the remaining two immunised volunteers. In-vitro assays showed the long-term persistence of parasite-specific pluripotent effector memory T-cell responses in protected volunteers. The four protected volunteers reported several mild to moderate adverse events, of which the most commonly reported symptom was headache (one to three episodes per volunteer). The two patients with delayed patency had adverse events similar to those in the control group. INTERPRETATION Artificially induced immunity lasts longer than generally recorded after natural exposure; providing a new avenue of research into the mechanisms of malaria immunity. FUNDING Dioraphte Foundation.

Vitamin D Deficiency among HIV Type 1-Infected Individuals in the Netherlands: Effects of Antiretroviral Therapy

Vitamin D regulates bone metabolism but has also immunoregulatory properties. In HIV-infected patients bone disorders are increasingly observed. Furthermore, low 1,25(OH)(2)D(3) levels have been associated with low CD4(+) counts, immunological hyperactivity, and AIDS progression rates. Few studies have examined the vitamin D status in HIV-infected patients. This study will specifically focus on the effects of antiretroviral agents on vitamin D status. Furthermore, the effect of vitamin D status on CD4 cell recovery after initiation of HAART will be evaluated. Among 252 included patients the prevalence of vitamin D deficiency (<35 nmol/liter from April to September and <25 nmol/liter from October to March) was 29%. Female sex, younger age, dark skin, and NNRTI treatment were significant risk factors in univariate analysis, although in multivariate analyses skin pigmentation remained the only independent risk factor. Median 25(OH)D(3) levels were significantly lower in white NNRTI-treated patients [54.5(27.9-73.8) nmol/liter] compared to white PI-treated patients [77.3 (46.6-100.0) nmol/liter, p = 0.007], while among nonwhites no difference was observed. Both PI- and NNRTI-treated patients had significantly higher blood PTH levels than patients without treatment. Moreover, NNRTI treatment puts patients at risk of elevated PTH levels (>6.5 pmol/liter). Linear regression analysis showed that vitamin D status did not affect CD4 cell recovery after initiation of HAART. In conclusion, 29% of the HIV-1-infected patients had vitamin D deficiency, with skin color as an independent risk factor. NNRTI treatment may add more risk for vitamin D deficiency. Both PI- and NNRTI-treated patients showed higher PTH levels and might therefore be at risk of bone problems. Evaluation of 25(OH)D(3) and PTH levels, especially in NNRTI-treated and dark skinned HIV-1-infected patients, is necessary to detect and treat vitamin D deficiency early.

Barriers to access to antiretroviral treatment in developing countries: a review.

Objective  To present a review of barriers impeding people living with HIV/AIDS in developing countries from accessing treatment, and to make recommendations for further studies.

Intensified regimen containing rifampicin and moxifloxacin for tuberculous meningitis: an open-label, randomised controlled phase 2 trial.

BACKGROUND Intensified antibiotic treatment might improve the outcome of tuberculous meningitis. We assessed pharmacokinetics, safety, and survival benefit of several treatment regimens containing high-dose rifampicin and moxifloxacin in patients with tuberculous meningitis in a hospital setting. METHODS In an open-label, phase 2 trial with a factorial design in one hospital in Indonesia, patients (aged >14 years) with tuberculous meningitis were randomly assigned to receive, according to a computer-generated schedule, first rifampicin standard dose (450 mg, about 10 mg/kg) orally or high dose (600 mg, about 13 mg/kg) intravenously, and second oral moxifloxacin 400 mg, moxifloxacin 800 mg, or ethambutol 750 mg once daily. All patients were given standard-dose isoniazid, pyrazinamide, and adjunctive corticosteroids. After 14 days of treatment all patients continued with standard treatment for tuberculosis. Endpoints included pharmacokinetic analyses of the blood and cerebrospinal fluid, adverse events attributable to tuberculosis treatment, and survival. Analysis was by intention to treat. This trial is registered with ClinicalTrials.gov, number NCT01158755. FINDINGS 60 patients were randomly assigned to receive rifampicin standard dose (12 no moxifloxacin, ten moxifloxacin 400 mg, and nine moxifloxacin 800 mg) and high dose (ten no moxifloxacin, nine moxifloxacin 400 mg, and ten moxifloxacin 800 mg). A 33% higher dose of rifampicin, intravenously, led to a three times higher geometric mean area under the time-concentration curve up to 6 h after dose (AUC(0-6); 78·7 mg.h/L [95% CI 71·0-87·3] vs 26·0 mg.h/L [19·0-35·6]), maximum plasma concentrations (C(max); 22·1 mg/L [19·9-24·6] vs 6·3 mg/L [4·9-8·3]), and concentrations in cerebrospinal fluid (0·60 mg/L [0·46-0·78] vs 0·21 mg/L [0·16-0·27]). Doubling the dose of moxifloxacin resulted in a proportional increase in plasma AUC(0-6) (31·5 mg.h/L [24·1-41·1] vs 15·1 mg.h/L [12·8-17·7]), C(max) (7·4 mg/L [5·6-9·6] vs 3·9 mg/L [3·2-4·8]), and drug concentrations in the cerebrospinal fluid (2·43 mg/L [1·81-3·27] vs 1·52 mg/L [1·28-1·82]). Intensified treatment did not result in increased toxicity. 6 month mortality was substantially lower in patients given high-dose rifampicin intravenously (ten [35%] vs 20 [65%]), which could not be explained by HIV status or severity of disease at the time of presentation (adjusted HR 0·42; 95% CI 0·20-0·91; p=0·03). INTERPRETATION These data suggest that treatment containing a higher dose of rifampicin and standard-dose or high-dose moxifloxacin during the first 2 weeks is safe in patients with tuberculous meningitis, and that high-dose intravenous rifampicin could be associated with a survival benefit in patients with severe disease. FUNDING Royal Dutch Academy of Arts and Sciences, Netherlands Foundation for Scientific Research, and Padjadjaran University, Bandung, Indonesia.

Exposure to Rifampicin Is Strongly Reduced in Patients with Tuberculosis and Type 2 Diabetes

BACKGROUND Type 2 diabetes (DM) is a strong risk factor for tuberculosis (TB) and is associated with a slower response to TB treatment and a higher mortality rate. Because lower concentrations of anti-TB drugs may be a contributing factor, we compared the pharmacokinetics of rifampicin in patients with TB, with and without DM. METHODS Seventeen adult Indonesian patients with TB and DM and 17 age- and sex-matched patients with TB and without DM were included in the study during the continuation phase of TB treatment. All patients received 450 mg of rifampicin (10 mg/kg) and 600 mg of isoniazid 3 times weekly. Steady-state plasma concentrations of rifampicin and its metabolite desacetylrifampicin were assessed at 0, 2, 4, and 6 h after drug intake. RESULTS Geometric means of rifampicin exposure (AUC(0-6 h)) were 12.3 mg x h/L (95% confidence interval [CI], 8.0-24.2) in patients with TB and DM, and 25.9 mg x h/L (95% CI, 21.4-40.2) in patients with TB only (P=.003). Similar differences were found for the maximum concentration of rifampicin. No significant differences in time to maximum concentration of rifampicin were observed. The AUC(0-6 h) of desacetylrifampicin was also much lower in patients with TB and DM versus patients with TB only (geometric mean, 0.60 vs. 3.2 mg x h/L; P=.001). Linear regression analysis revealed that higher body weight (P<.001), the presence of DM (P=.06), and plasma glucose concentration (P=.016) were correlated with exposure to rifampicin. CONCLUSION Exposure (AUC(0-6 h)) to rifampicin was 53% lower in Indonesian patients with TB and DM, compared with patients with TB only. Patients with TB and DM who have a higher body weight may need a higher dose of rifampicin.

Implications of the global increase of diabetes for tuberculosis control and patient care

Objectives  To review the current knowledge about tuberculosis (TB) and diabetes, assessing the implication of the global increase of diabetes for TB control and patient care.

Protection against malaria after immunization by chloroquine prophylaxis and sporozoites is mediated by preerythrocytic immunity

Volunteers immunized under chloroquine chemoprophylaxis with Plasmodium falciparum sporozoites (CPS) develop complete, long-lasting protection against homologous sporozoite challenge. Chloroquine affects neither sporozoites nor liver-stages, but kills only asexual forms in erythrocytes once released from the liver into the circulation. Consequently, CPS immunization exposes the host to antigens from both preerythrocytic and blood stages, and induced immunity might target either of these stages. We therefore explored the life cycle stage specificity of CPS-induced protection. Twenty-five malaria-naïve volunteers were enrolled in a clinical trial, 15 of whom received CPS immunization. Five immunized subjects and five controls received a sporozoite challenge by mosquito bites, whereas nine immunized and five control subjects received an i.v. challenge with P. falciparum-infected erythrocytes. The latter approach completely bypasses preerythrocytic stages, enabling a direct comparison of protection against either life cycle stage. CPS-immunized subjects (13 of 14) developed anticircumsporozoite antibodies, whereas only one volunteer generated minimal titers against typical blood-stage antigens. IgG from CPS-immunized volunteers did not inhibit asexual blood-stage growth in vitro. All CPS-immunized subjects (5 of 5) were protected against sporozoite challenge. In contrast, nine of nine CPS-immunized subjects developed parasitemia after blood-stage challenge, with identical prepatent periods and blood-stage multiplication rates compared with controls. Intravenously challenged CPS-immunized subjects showed earlier fever and increased plasma concentrations of inflammatory markers D-dimer, IFN-γ, and monokine induced by IFN-γ than i.v. challenged controls. The complete lack of protection against blood-stage challenge indicates that CPS-induced protection is mediated by immunity against preerythrocytic stages. However, evidence is presented for immune recognition of P. falciparum-infected erythrocytes, suggesting memory responses unable to generate functional immunity.