A phase IIa, randomized, double-blind, safety, immunogenicity and efficacy trial of Plasmodium falciparum vaccine antigens merozoite surface protein 1 and RTS,S formulated with AS02 adjuvant in healthy, malaria-naïve adults

BACKGROUND

To improve the efficacy of Plasmodium falciparum malaria vaccine RTS,S/AS02, we conducted a study in 2001 in healthy, malaria-naïve adults administered RTS,S/AS02 in combination with FMP1, a recombinant merozoite surface-protein-1, C-terminal 42kD fragment.

METHODS

A double-blind Phase I/IIa study randomized N = 60 subjects 1:1:1:1 to one of four groups, N = 15/group, to evaluate safety, immunogenicity, and efficacy of intra-deltoid half-doses of RTS,S/AS02 and FMP1/AS02 administered in the contralateral (RTS,S + FMP1-separate) or same (RTS,S + FMP1-same) sites, or FMP1/AS02 alone (FMP1-alone), or RTS,S/AS02 alone (RTS,S-alone) on a 0-, 1-, 3-month schedule. Subjects receiving three doses of vaccine and non-immunized controls (N = 11) were infected with homologous P. falciparum 3D7 sporozoites by Controlled Human Malaria Infection (CHMI).

RESULTS

Subjects in all vaccination groups experienced mostly mild or moderate local and general adverse events that resolved within eight days. Anti-circumsporozoite antibody levels were lower when FMP1 and RTS,S were co-administered at the same site (35.0 µg/mL: 95 % CI 20.3-63), versus separate arms (57.4 µg/mL: 95 % CI 32.3-102) or RTS,S alone (62.0 µg/mL: 95 % CI: 37.8-101.8). RTS,S-specific lymphoproliferative responses and ex vivo ELISpot CSP-specific interferon-gamma (IFN-γ) responses were indistinguishable among groups receiving RTS,S/AS02. There was no difference in antibody to FMP1 among groups receiving FMP1/AS02. After CHMI, groups immunized with a RTS,S-containing regimen had ∼ 30 % sterile protection against parasitemia, and equivalent delays in time-to-parasitemia. The FMP1/AS02 alone group showed no sterile immunity or delay in parasitemia.

CONCLUSION

Co-administration of RTS,S and FMP1/AS02 reduced anti-RTS,S antibody, but did not affect tolerability, cellular immunity, or efficacy in a stringent CHMI model. Absence of efficacy or delay of patency in the sporozoite challenge model in the FMP1/AS02 group did not rule out efficacy of FMP1/AS02 in an endemic population. However, a Phase IIb trial of FMP1/AS02 in children in malaria-endemic Kenya did not demonstrate efficacy against natural infection.

CLINICALTRIALS

gov identifier: NCT01556945.

Malaria rapid diagnostic devices: performance characteristics of the ParaSight F device determined in a multisite field study

Microscopic detection of parasites has been the reference standard for malaria diagnosis for decades. However, difficulty in maintaining required technical skills and infrastructure has spurred the development of several nonmicroscopic malaria rapid diagnostic devices based on the detection of malaria parasite antigen in whole blood. The ParaSight F test is one such device. It detects the presence of Plasmodium falciparum-specific histidine-rich protein 2 by using an antigen-capture immunochromatographic strip format. The present study was conducted at outpatient malaria clinics in Iquitos, Peru, and Maesod, Thailand. Duplicate, blinded, expert microscopy was employed as the reference standard for evaluating device performance. Of 2,988 eligible patients, microscopy showed that 547 (18%) had P. falciparum, 658 (22%) had P. vivax, 2 (0.07%) had P. malariae, and 1,750 (59%) were negative for Plasmodium. Mixed infections (P. falciparum and P. vivax) were identified in 31 patients (1%). The overall sensitivity of ParaSight F for P. falciparum was 95%. When stratified by magnitude of parasitemia (no. of asexual parasites per microliter of whole blood), sensitivities were 83% (>0 to 500 parasites/microl), 87% (501 to 1,000/microl), 98% (1,001 to 5,000/microl), and 98% (>5,000/microl). Device specificity was 86%.

Comparison of IsoCode STIX and FTA Gene Guard collection matrices as whole-blood storage and processing devices for diagnosis of malaria by PCR

We compared two collection devices, IsoCode and FTA, with whole blood for the diagnosis of malaria by PCR (n = 100). Using whole blood as the reference standard, both devices were sensitive for the detection of single-species malaria infections by PCR (> or =96%). However, the detection of mixed infections was suboptimal (IsoCode was 42% sensitive, and FTA was 63% sensitive).

Safety and efficacy of intravenous sodium stibogluconate in the treatment of leishmaniasis: recent U.S. military experience

The efficacy and toxicity of sodium stibogluconate (SSG) at a dosage of 20 mg/(kg.d) for either 20 days (for cutaneous disease) or 28 days (for visceral, mucosal, or viscerotropic disease) in the treatment of leishmaniasis is reported. Ninety-six U.S. Department of Defense health care beneficiaries with parasitologically confirmed leishmaniasis were prospectively followed for 1 year. One patient was infected with human immunodeficiency virus; otherwise, comorbidity was absent. Clinical cure occurred in 91% of 83 cases of cutaneous disease and 93% of 13 cases of visceral/viscerotropic disease. Adverse effects were common and necessitated interruption of treatment in 28% of cases, but they were generally reversible. These included arthralgias and myalgias (58%), pancreatitis (97%), transaminitis (67%), headache (22%), hematologic suppression (44%), and rash (9%). No subsequent mucosal leishmaniasis was identified, and there were no deaths attributable to SSG or leishmaniasis.

Infection due to Mycobacterium haemophilum identified by whole cell lipid analysis and nucleic acid sequencing

A patient with indolent, non-Hodgkin's lymphoma developed a pretibial soft tissue abscess caused by a fastidious mycobacterium. Because the organism could not be definitively identified by standard microbiologic testing, whole cell fatty acid analysis and 16S rDNA sequencing were performed. These procedures identified the organism as Mycobacterium haemophilum. We review the diagnostic considerations with regard to this pathogen.

Pancreatitis induced by pentavalent antimonial agents during treatment of leishmaniasis

Pentavalent antimony (Sbv), formulated as sodium stibogluconate or meglumine antimoniate, is the standard treatment for the leishmaniases. In 16 of 17 consecutive, prospectively observed patients in Washington D.C., serum levels of amylase and lipase rose to abnormal values after therapy with sodium stibogluconate was started; 12 of 17 had symptoms of pancreatitis. Sbv therapy was continued to completion in 7 of 17 patients and interrupted in 10 of 17. Pancreatitis improved in every patient after Sbv therapy was stopped. Sbv treatment was resumed after brief interruptions in 6 of 10 patients. All six of these patients had flares of pancreatitis, but each completed therapy. Subsequently, we measured amylase and lipase levels in stored sera from 32 patients treated in Peru with either sodium stibogluconate or meglumine antimoniate for mucosal leishmaniasis. In all 32 Peruvian patients, serum amylase and lipase rose to abnormal levels during Sbv therapy; 11 of 32 had symptoms of pancreatitis. Standard Sbv regimens induce pancreatitis in almost all patients, but continued therapy is often tolerated; pancreatitis subsides when therapy is stopped, and rechallenge may be tolerated after a brief halt in treatment.

Visceral infection caused by Leishmania tropica in veterans of Operation Desert Storm

BACKGROUND

Visceral leishmaniasis, usually caused by Leishmania donovani, has rarely been reported from eastern Saudi Arabia, so it was not expected to affect the soldiers of Operation Desert Storm.

METHODS

We evaluated eight soldiers with visceral leishmanial infection, examining their serum with an immunofluorescent-antibody assay, examining their marrow or biopsy tissue for amastigotes with an indirect immunofluorescent-monoclonal-antibody assay, and culturing the parasites. Cultured promastigotes were isolated and characterized by isoenzyme analysis.

RESULTS

None of the eight soldiers had classic signs or symptoms of visceral leishmaniasis (kala-azar). Seven soldiers had unexplained fever, chronic fatigue, malaise, cough, intermittent diarrhea, or abdominal pain that began up to seven months after they returned to the United States; one had no symptoms. Five had adenopathy or mild, transient hepatosplenomegaly. None had cutaneous manifestations. Diagnoses were made by bone marrow aspiration (seven patients) or lymph-node biopsy (one patient). Six isolates have been identified as L. tropica, which usually causes only cutaneous disease. Of the six patients treated with sodium stibogluconate, five improved and one remained symptomatic.

CONCLUSIONS

L. tropica can produce visceral infection that can cause unexplained systemic illness in persons returning from areas where this organism is endemic.

Pasteurella multocida pneumonia in a man with AIDS and nontraumatic feline exposure

A case of acute pneumonia due to Pasteurella multocida ssp multocida occurred in a young man with AIDS and chronic sinusitis. The pneumonia was diagnosed by bronchoscopy and responded to treatment with aztreonam. Epidemiologic investigation revealed the case was temporally related to nontraumatic exposure to cat secretions that the patient presumably had acquired via an aerosol. The cat's oral cavity was cultured and an isolate of P multocida ssp multocida with identical biochemical reactions, DNA restriction patterns, and nearly identical fatty acid profile to that of the patient's isolate was obtained suggesting they were identical strains and therefore epidemiologically linked. A control strain with identical biochemical reactions and antibiotic sensitivities exhibited different patterns. To our knowledge, this is the first such reported infection in a patient infected with human immunodeficiency virus.

Prolonged recurrence of pentamidine-induced torsades de pointes

OBJECTIVE

To report a case of recurrent pentamidine-induced torsades de pointes (TdP) and to review previously reported cases in the literature.

DATA SOURCES

Medical records of the subject patient, case reports, and relevant studies identified by MEDLINE.

DATA EXTRACTION

Data were abstracted from pertinent published sources by one author and reviewed by the remaining authors.

DATA SYNTHESIS

A 43-year-old woman with AIDS experienced pentamidine-induced TdP. TdP and other cardiac arrhythmias recurred repeatedly for 13 days after pentamidine therapy was discontinued and in the presence of normal magnesium and potassium serum concentrations. Infusions of magnesium, lidocaine, and isoproterenol were used to treat the arrhythmias. The exact mechanism of pentamidine-induced TdP has not been clearly established. It is postulated, however, that the similarity of pentamidine's structure to procainamide may contribute to its proarrhythmic effects. The tissue-binding capacity of pentamidine may result in a prolongation of its effects. No distinctive characteristic appears to predispose people to the development of cardiac arrhythmias. Laboratory values that should be monitored include serum magnesium, potassium, and creatinine. The corrected QT interval also should be monitored.

CONCLUSIONS

Recurrent arrhythmias may be seen for many days after intravenous administration of pentamidine has been discontinued. Clinicians should consider this phenomenon as they decide how to monitor patients who have received this drug.