8. Effect of iron supplementation and malaria prophylaxis in infants on Plasmodium falciparum genotypes and multiplicity of infection

During a randomized placebo-controlled trial of chemoprophylaxis against Plasmodium falciparum malaria and iron supplementation, in infants living under conditions of intense transmission, all samples of P. falciparum obtained from children aged 5 and 8 months were genotyped by polymerase chain reaction-restriction fragment length polymorphism analysis for the msp2 locus. One hundred and six blood samples were analysed for the number of concurrent infections (multiplicity), and the allelic family of each msp2 genotype was determined. Mean multiplicity of infection was, overall, 2·76 infections/child, and it was significantly reduced in infants receiving chemoprophylaxis. This finding might help to explain the rebound effect in morbidity observed after prophylaxis was ended. Iron supplementation did not affect multiplicity of infection. In infants receiving placebo only, or placebo and iron supplementation, a significant positive association was observed between the number of infections and parasite densities (Spearman's ϱ = 0·25, P − 0·047). This association was lost in the group receiving chemoprophylaxis alone, or in combination with iron. This study showed a significant association of FC27-like msp2 alleles with prospective risk of clinical malaria in children (relative risk = 1·487, P = 0·013). Such an association was also found for the present risk of clinical malaria in infants receiving prophylaxis (odds ratio = 3·84, P = 0·026), which might imply that chemoprophylaxis may impair the development of premunition.     

New guidelines for the prevention of imported malaria in France

Prevention of malaria is based on personal vector-control measures (PVCMs) to avoid mosquito bites at night and chemoprophylaxis if justified by the risk of contracting the disease. The most effective PVCM is the use of insecticide-treated mosquito nets. The decision to prescribe chemoprophylaxis, mainly to prevent Plasmodium falciparum infection, depends on the benefit-risk ratio. Overall, the risk of contracting malaria is 1,000-fold lower during a stay in the tropical regions of Asia or the Americas than in sub-Saharan Africa. For “conventional” stays (less than one month with nights spent in urban areas) in low-risk settings in tropical Asia and America, the risk of being infected with Plasmodium parasites (≤1/100,000) is equivalent or lower than that of experiencing serious adverse effects caused by chemoprophylaxis. Preventive medication is therefore no longer recommended. By contrast, in other settings and particularly in sub-Saharan Africa, chemoprophylaxis is the most effective measure against malaria. However, it is worth noting that no single preventive measure provides full protection. Regardless of the level of risk or chemoprophylaxis-related indication, protection against mosquito bites and rapid management of febrile illness after returning from an endemic area are also critical to prevent malaria. Finally, migrants of sub-Saharan origin visiting friends and relatives in their country of origin form a high-risk group who should be recommended chemoprophylaxis in the same way as any other travelers—with a preference for the least expensive molecules (doxycycline).     

Common Epidemiology of Rickettsia felis Infection and Malaria,Africa

This study aimed to compare the epidemiology of Rickettsia felis infection and malaria in France, North Africa, and sub-Saharan Africa and to identify a common vector. Blood specimens from 3,122 febrile patients and from 500 nonfebrile persons were analyzed for R. felis and Plasmodium spp. We observed a significant linear trend (p<0.0001) of increasing risk for R. felis infection. The risks were lowest in France, Tunisia, and Algeria (1%), and highest in rural Senegal (15%). Co-infections with R. felis and Plasmodium spp. and occurrences of R. felis relapses or reinfections were identified. This study demonstrates a correlation between malaria and R. felis infection regarding geographic distribution, seasonality, asymptomatic infections, and a potential vector. R. felis infection should be suspected in these geographical areas where malaria is endemic. Doxycycline chemoprophylaxis against malaria in travelers to sub-Saharan Africa also protects against rickettsioses; thus, empirical treatment strategies for febrile illness for travelers and residents in sub-Saharan Africa may require reevaluation.     

The effect of diethylcarbamazine in a murine model of Brugia malayi microfilaraemia.

The effect of diethylcarbamazine was tested in a murine model of Brugia malayi microfilaraemia. A course of therapy similar to that used to treat human infection led to more than a 90% decrease in circulating parasites. Experiments in which different amounts of diethylcarbamazine were given as a single dose indicated that its microfilaricidal activity is dose-dependent. The animal model of B. malayi microfilaraemia may be useful for studies of the mechanism of action and pharmacology of diethylcarbamazine and may be applied to the screening of new microfilaricidal drugs.     

Protection against malaria by immunization with non-attenuated sporozoites under single-dose piperaquine-tetraphosphate chemoprophylaxis

Experimental whole-parasite immunization through concurrent administration of infectious Plasmodium sporozoites with drugs that prevent pathogenic blood-stage infection represents the current benchmark in malaria vaccine development. Key questions concerning translation remain, including the requirement for single-dose drug regimens that can reliably prevent breakthrough infections. We assessed the feasibility and efficacy of immunization with single-dose piperaquine chemoprophylaxis and concurrent sporozoite administration (PPQ-CPS) in the murine P. berghei ANKA/C57BL/6 infection model. We demonstrate that PPQ-CPS is protective with an efficacy comparable to previous findings using whole-parasite immunization under chloroquine chemoprophylaxis. PPQ-CPS immunization resulted in an expansion of intrahepatic and intrasplenic effector memory CD8⁺ T cells. In summary, PPQ-CPS appears to be a safe and efficacious immunization regimen in the rodent malaria model and may thus become an important improvement regarding the translation of whole-parasite immunization toward a human malaria vaccine.     

Studies on the toxicity and action of diaminodiphenylsulfone (DDS) in avian and simian malaria

Interest in the schizontocidal activity of diaminodiphenylsulfone (DDS) and in its possible use in malaria chemoprophylaxis has recently been revived. Studies on its toxicity and action in avian and simian malaria show that its chronic toxicity in monkeys is similar to that of the established antimalarials and that it lacks causal prophylactic, gametocidal and sporontocidal activity against Plasmodium gallinaceum.     

Variations in chemoprophylaxis for meningococcal disease: a retrospective case note review, analysis of routine prescribing data and questionnaire of general practitioners

Background  

Invasive meningococcal disease is a significant cause of mortality and morbidity in the UK. Administration of chemoprophylaxis to close contacts reduces the risk of a secondary case. However, unnecessary chemoprophylaxis may be associated with adverse reactions, increased antibiotic resistance and removal of organisms, such as Neisseria lactamica, which help to protect against meningococcal disease. Limited evidence exists to suggest that overuse of chemoprophylaxis may occur. This study aimed to evaluate prescribing of chemoprophylaxis for contacts of meningococcal disease by general practitioners and hospital staff.     

Long incubation of Plasmodium vivax multinucleatum as demonstrated in three experimental human cases

Three human volunteers infected in the laboratory with sporozoites of Plasmodium vivax multinucleatum from Henan Province, China, displayed long-term delayed primary attacks. All three volunteers first showed parasitaemia and symptoms between 312 and 323 days after being bitten by infected Anopheles balabacensis. The characteristics which define the subspecies were retained throughout the infections.     

Observations on the pathogenicity for white rats of a strain of Trypanosoma rhodesiense

White rats were used as test animals in an experiment to see whether a strain of T. rhodesiense would lose its infectivity to man or undergo other changes in its characters during maintenance in ruminant animals. The rats were infected by the bites of isolated G. morsitans and also by inoculation from the infected animals and volunteers. No change in virulence was observed.The infections in rats produced by inoculation and by the bites of flies which had fed on the same hosts were similar, but those produced by the flies appeared to be rather more acute.The infections of a reedbuck and a Thomson's gazelle were apparently similar, as tested in white rats; but when G. morsitans were fed on these animals those which fed on the reedbuck showed a large proportion with infected salivary glands, which no fly with infected salivary glands was found among those which fed on the gazelle.     

Sustainability of soil-transmitted helminth control following a single-dose co-administration of albendazole and diethylcarbamazine

We evaluated the long-term impact of single-dose diethylcarbamazine plus albendazole combination therapy with that of diethylcarbamazine alone on the control of soil-transmitted helminths (STH) in 2 blocks (revenue units) of Villupuram district, south India, as part of an ongoing mass drug administration (MDA) campaign for the elimination of lymphatic filariasis in 2001. The prevalence and intensities of STHs were studied in 287 children, aged 9 and 10 years (136 in the combination therapy cohort and 151 in the diethylcarbamazine alone cohort), using the Kato-Katz technique to examine stool samples at 4 time-points (baseline, and 3 weeks, 6 months and 11 months after MDA). The combination therapy showed long-term efficacy against STHs and the magnitude of control remained at a moderate and significant level for 11 months after MDA compared with the moderate gains of diethylcarbamazine alone. Single-dose MDA with albendazole and diethylcarbamazine combination therapy may prove to be a good strategy in treating multiple parasitic infections in endemic communities.     

Safety,immunogenicity and dose response of VLA84, a new vaccine candidate against Clostridium difficile,in healthy volunteers

BackgroundClostridium difficile infection (CDI) is the leading cause of antibiotic-associated diarrhoea and colitis and the most common pathogen of health care-associated infections. In the US, CDI causes approximately half a million infections and close to 30,000 deaths. Despite antibiotic treatment of C. difficile associated diarrhoea, the disease is complicated by its recurrence in up to 30% of patients.MethodsAn open-label, partially randomized, dose-escalation Phase I trial was performed in two parts. Sixty volunteers aged ≥18 to <65 years were randomized into five treatment groups to receive three immunizations (Day 0, 7, 21) of VLA84 (20 μg with Alum, 75 μg with or without Alum, 200 μg with or without Alum). Eighty-one volunteers aged ≥65 were randomized into four treatment groups (75 μg with or without Alum, 200 μg with or without Alum) and received four immunizations (Day 0, 7, 28 and 56). All subjects were followed for safety and immunogenicity for six months.ResultsVLA84 was safe and well tolerated. Fifty-one adult volunteers (85%) and 50 elderly (62%) experienced at least one solicited or unsolicited adverse event (AE). Forty-eight adult volunteers (80%) and 40 elderly (49%) experienced related AEs which were mostly mild or moderate. No related serious adverse event and no death occurred. The vaccine induced high antibody titres against Toxin A and Toxin B in both study populations.ConclusionVLA84 was safe, well tolerated and highly immunogenic in adult volunteers aged ≥18 to <65 years and elderly volunteers aged ≥65 years.This study is registered at ClinicalTrials.gov under registration number NCT01296386.     

11. Premunition in Plasmodium falciparum infection: insights from the epidemiology of multiple infections

Epidemiological studies of multiple clone infections by Plasmodium falciparum in highly endemic areas have demonstrated age dependence in both the multiplicity of infection and the relationships between this multiplicity and the risk of acute illness. We hypothesize that, in infants, host defence against blood-stage infections with P falciparum relies mainly on fever and cytokine activities, and the infections are of short duration. In older children, a high multiplicity of infection is characteristic of low-level chronic parasitaemia. This appears to confer cross-protection against newly inoculated parasites, via partially genotype-specific responses which are short-term, lasting little longer than the infections themselves. This has important implications for our understanding of immunity against P. falciparum, its ecological niche, and the epidemiological impact of interventions against it.     

Exploring immunological mechanisms of the whole sporozoite vaccination against P. falciparum malaria

Great progress has been made in the development of whole sporozoite vaccines including the manufacturing of cryopreserved Plasmodium falciparum sporozoites (PfSPZ) suitable for clinical application. Such whole sporozoites are being used for clinical studies of controlled human malaria infection (CHMI) as well as for evaluation of candidate vaccine approaches (both attenuated sporozoites and infectious sporozoites administered with chemoprophylaxis) and as reagents for immunology and cell biology assays. CHMI studies with whole sporozoites provide a great opportunity to better understand the intrinsic mechanisms of resistance to P. falciparum (e.g. due to sickle cell trait and other hemoglobinopathies) as well as host responses to an initial P. falciparum infection. High-level protective efficacy has been demonstrated in a small number of volunteers after intravenous (IV) inoculation of radiation-attenuated PfSPZ or in those who were exposed to live PfSPZ while on malaria chemoprophylaxis. These advances and data warrant further investigations of the immunological mechanism(s) whereby whole sporozoite inoculation elicits protective immunity in order to facilitate whole sporozoite vaccine development. The National Institute of Allergy and Infectious Diseases (NIAID) convened a workshop on Sept. 2–3, 2014 involving participation of international experts in the field of malaria vaccine development, and in basic and clinical immunology research. The workshop discussed the current understanding of host immune responses to whole malaria sporozoite inoculation, identified gaps in knowledge, resources to facilitate progress, and applicable new technologies and approaches to accelerate immunologic and vaccinologic studies and biomarker identification. This report summarizes the discussions and major conclusions from the workshop participants.     

Tanzania Filariasis Project: a provocative day test with diethylcarbamazine for the detection of microfilariae of nocturnally periodic Wuchereria bancrofti in the blood.

In coastal Tanzania, an area where the microfilariae (mf) of Wuchereria bancrofti exhibit nocturnal periodicity, the administration of 2 mg diethylcarbamazine (DEC) per kg body weight in the daytime provoked mf to enter the peripheral blood. In persons on normal daily activities the daytime DEC provocative method proved to be as sensitive in detecting microfilaraemia as was the examination of night blood. Its use in routine surveys is therefore justified. Although mf densities by day and night were highly correlated (r = 0.83) they tended to be lower after provocative daytime DEC than in the corresponding night blood, except in very light infections. This method was also useful in assessing the parasitological response to mass chemotherapy with DEC, but, in comparison with the results of the night blood examinations, the sensitivity and magnitude of the counts in persons remaining positive progressively decreased as the period of DEC administration increased. A correction factor has to be calculated to take account of this, and/or additional night blood samples must be taken.     

Drug trials with levamisole hydrochloride and diethylcarbamazine citrate in Bancroftian and Malayan filariasis

Seventy-eight microfilaraemic patients with Wuchereria bancrofti and Brugia malayi infections were treated with various oral levamisole hydrochloride total dosage regimes of 150 to 3,150 mg and total diethylcarbamazine citrate (DEC) of 36 and 126 mg per kg body-weight. Significant microfilaricidal and probable macrofilaricidal effects were seen at total levamisole hydrochloride dosages of 300 to 3,150 mg and the DEC dosages. The optimum dosage regime with levamisole hydrochloride recommended for treatment of microfilaraemic patients is 100 mg initially followed by 100 mg twice daily for 10 days. This dosage regime was as effective as a total oral dosage of DEC at 126 mg per kg body-weight. Side reactions were dose-dependent, mild and transient, with fever being the most common. One patient developed fits after 150 mg levemisole hydrochloride. The pathophysiology of these side reactions is discussed and it is recommended that levamisole hydrochloride, as a probable alternative for the treatment of patent and occult filariasis, should be used only under close medical supervision.     

Antigens of Setaria digitata: cross-reaction with surface antigens of Wuchereria bancrofti microfilariae and serum antibodies of W. bancrofti-infected subjects

Extracts of Setaria digitata have been fractionated by DEAE-Sephadex A50 chromatography and the fractions obtained were used in the inhibition of indirect immunofluorescence of Wuchereria bancrofti microfilariae. The fractions were also tested by an enzyme-linked immunosorbent assay (ELISA) technique for reactivity against antibodies in the serum of patients with W. bancrofti infections. The results indicate that S. digitata contains several antigenic fractions that show cross-reactivity against filariasis sera; two of these fractions cross-reacted with surface antigens of W. bancrofti microfilariae but, when tested by the ELISA technique, these antigens did not show the highest reactivity against serum antibodies.     

The activity against Trypanosoma cruzi and cutaneous leishmaniasis,and toxicity,of moxipraquine (349C59)

A novel 8-aminoquinoline compound, 8{6-4′ (3 — hydroxybutyl)piperazin — 1′ — ylhexylamino} — 6 —methoxyquinoline di(hydrogen maleate), moxipraquine, 349C59, was shown to be active against experimental infections with Trypanosoma cruzi. It was effective in suppressing parasitaemia but did not eradicate the infection from mice or guinea-pigs. Other clinically tested drugs, including nifurtimox, were likewise incapable of eradicating the parasite from infected mice. Moxipraquine was less potent against mouse infections with strain Peru than it was against other strains of T. cruzi. In limited tests, moxipraquine was effective on experimental infections of Leishmania major, L. mexicana mexicana and L. brasiliensis panamensis but not L.b. brasiliensis. Significant foetal toxicity, observed experimentally in rats and rabbits, resulted in the termination of clinical trials.     

OmpW is a potential target for eliciting protective immunity against Acinetobacter baumannii infections

Acinetobacter baumannii (A. baumannii) is an important conditioned pathogen that causes nosocomial and community-associated infections. In this study, we sought to investigate whether outer membrane protein W (OmpW) is a potential target for eliciting protective immunity against A. baumannii infections. Mice immunized with the fusion protein thioredoxin-OmpW generated strong OmpW-specific IgG responses. In a sepsis model, both active and passive immunizations against OmpW effectively protected mice from A. baumannii infections. This protection was demonstrated by a significantly improved survival rate, reduced bacterial burdens within organs, and the suppressed accumulation of inflammatory cytokines and chemokines in sera. Opsonophagocytic assays with murine macrophage RAW264.7 cells indicated that the bactericidal effects of the antisera derived from the immunized mice are mediated synergistically by specific antibodies and complement components. The antisera presented significant opsonophagocytic activities against homologous strains and clonally distinct clinical isolates in vitro. Protein data analysis showed that the sequence of OmpW, which has a molecule length of 183 amino acids, is more than 91% conserved in reported A. baumannii strains. In conclusion, we identified OmpW as a highly immunogenic and conserved protein as a valuable antigen candidate for the development of an effective vaccine or the preparation of antisera to control A. baumannii infections.     

Analysis of the coverage capacity of the StreptInCor candidate vaccine against Streptococcus pyogenes

Streptococcus pyogenes is responsible for infections as pharyngitis, sepsis, necrotizing fasciitis and streptococcal toxic shock syndrome. The M protein is the major bacterial antigen and consists of both polymorphic N-terminal portion and a conserved region. In the present study, we analyzed the in vitro ability of StreptInCor a C-terminal candidate vaccine against S. pyogenes to induce antibodies to neutralize/opsonize the most common S. pyogenes strains in Sao Paulo by examining the recognition by sera from StreptInCor immunized mice. We also evaluated the presence of cross-reactive antibodies against human heart valve tissue. Anti-StreptInCor antibodies were able to neutralize/opsonize at least 5 strains, showing that immunization with StreptInCor is effective against several S. pyogenes strains and can prevent infection and subsequent sequelae without causing autoimmune reactions.     

Probiotic bacteria stimulate virus–specific neutralizing antibodies following a booster polio vaccination

Summary Background Orally ingested probiotic bacteria may modulate the immune response and increase antibody titers against enteric infections by bacteria or viruses. Even though positive effects of probiotics on respiratory tract infections have been reported, overall only few studies have examined effects on virus infections concerning organs other than the gastrointestinal tract. Aim of the study It was the aim of the study to investigate whether and how probiotics affect the immune response to a standardized enterovirus challenge (polio) and infections not limited to the gastrointestinal tract in healthy adults. Methods In a randomized, controlled and double–blind study 64 volunteers consumed for 5 weeks chemically acidified clotted milk without bacteria or with 10¹⁰/serving ^{Lactobacillus rhamnosus} GG or Lactobacillus acidophilus CRL431 added. In the second week subjects were vaccinated orally against polio 1, 2 and 3. Polio virus neutralizing serum activity, the primary parameter, was determined by the standard neutralization test (WHO) before and three times after vaccination. Polio–specific IgA, IgG and IgM were detected by ELISAs. Results Probiotics increased poliovirus neutralizing antibody titers (NT) and affected the formation of poliovirus–specific IgA and IgG in serum. The maximum increase after immunization was about 2, 2.2, or 4–fold higher, respectively, for NT, IgG or, IgA, in volunteers consuming probiotics instead of placebo. No consistent difference was noted between bacterial strains. Conclusions Probiotics induce an immunologic response that may provide enhanced systemic protection of cells from virus infections by increasing production of virus neutralizing antibodies. The work was supported by the German Academy of Nutritional Medicine, Freiburg, Germany; by MONA, division of Campina Melkunie, Woerden, The Netherlands and by Chr. Hansen, H?rsholm, Denmark.