Short report: elevated levels of alanine aminotransferase and hepatitis A in the context of a pediatric malaria vaccine trial in a village in Mali.

A Phase 1 study of the apical membrane antigen malaria vaccine AMA1-C1/Alhydrogel was conducted in 2-3-year-old children in a village in Mali. A high frequency of elevated levels of alanine aminotransferase (ALT) caused by hepatitis A was seen, with 8 of 36 children diagnosed by specific IgM antibody over the course of the study. Hepatitis A is a common cause of asymptomatic elevations of ALT levels in children, particularly in less-developed settings. Investigators should be aware of the frequency of hepatitis A in this age group to guard against inadvertently facilitating transmission at study facilities and to properly evaluate symptomatic or asymptomatic elevations of ALT levels.

Phase 1 study of a combination AMA1 blood stage malaria vaccine in Malian children.

BACKGROUND: Apical Membrane Antigen-1 (AMA1) is one of the leading blood stage malaria vaccine candidates. AMA1-C1/Alhydrogel consists of an equal mixture of recombinant AMA1 from FVO and 3D7 clones of P. falciparum, adsorbed onto Alhydrogel. A Phase 1 study in semi-immune adults in Mali showed that the vaccine was safe and immunogenic, with higher antibody responses in those who received the 80 microg dose. The aim of this study was to assess the safety and immunogenicity of this vaccine in young children in a malaria endemic area. DESIGN: This was a Phase 1 dose escalating study in 36 healthy children aged 2-3 years started in March 2006 in Donéguébougou, Mali. Eighteen children in the first cohort were randomized 2 ratio 1 to receive either 20 microg AMA1-C1/Alhydrogel or Haemophilus influenzae type b Hiberix vaccine. Two weeks later 18 children in the second cohort were randomized 2 ratio 1 to receive either 80 microg AMA1-C1/Alhydrogel or Haemophilus influenzae type b Hiberix vaccine. Vaccinations were administered on Days 0 and 28 and participants were examined on Days 1, 2, 3, 7, and 14 after vaccination and then about every two months. Results to Day 154 are reported in this manuscript. RESULTS: Of 36 volunteers enrolled, 33 received both vaccinations. There were 9 adverse events related to the vaccination in subjects who received AMA1-C1 vaccine and 7 in those who received Hiberix. All were mild to moderate. No vaccine-related serious or grade 3 adverse events were observed. There was no increase in adverse events with increasing dose of vaccine or number of immunizations. In subjects who received the test vaccine, antibodies to AMA1 increased on Day 14 and peaked at Day 42, with changes from baseline significantly different from subjects who received control vaccine. CONCLUSION: AMA-C1 vaccine is well tolerated and immunogenic in children in this endemic area although the antibody response was short lived. TRIAL REGISTRATION: Clinicaltrials.gov NCT00341250.

Impact of a Plasmodium falciparum AMA1 vaccine on antibody responses in adult Malians.

BACKGROUND: Apical Membrane Antigen 1 (AMA1) of Plasmodium falciparum merozoites is a leading blood-stage malaria vaccine candidate. Protection of Aotus monkeys after vaccination with AMA1 correlates with antibody responses. STUDY DESIGN/RESULTS: A randomized, controlled, double-blind phase 1 clinical trial was conducted in 54 healthy Malian adults living in an area of intense seasonal malaria transmission to assess the safety and immunogenicity of the AMA1-C1 malaria vaccine. AMA1-C1 contains an equal mixture of yeast-expressed recombinant proteins based on sequences from the FVO and 3D7 clones of P. falciparum, adsorbed on Alhydrogel. The control vaccine was the hepatitis B vaccine (Recombivax). Participants were enrolled into 1 of 3 dose cohorts (n = 18 per cohort) and randomized 2:1 to receive either AMA1-C1 or Recombivax. Participants in the first, second, and third cohorts randomized to receive AMA1-C1 were vaccinated with 5, 20 and 80 microg of AMA1-C1, respectively. Vaccinations were administered on days 0, 28, and 360, and participants were followed until 6 months after the final vaccination. AMA1-C1 was well tolerated; no vaccine-related severe or serious adverse events were observed. AMA1 antibody responses to the 80 microg dose increased rapidly from baseline levels by days 14 and 28 after the first vaccination and continued to increase after the second vaccination. After a peak 14 days following the second vaccination, antibody levels decreased to baseline levels one year later at the time of the third vaccination that induced little or no increase in antibody levels. CONCLUSIONS: Although the AMA1-C1 vaccine candidate was well-tolerated and induced antibody responses to both vaccine and non-vaccine alleles, the antibody response after a third dose given at one year was lower than the response to the initial vaccinations. Additionally, post-vaccination increases in anti-AMA1 antibody levels were not associated with significant changes in in vitro growth inhibition of P. falciparum. TRIAL REGISTRATION: ClinicalTrials.gov NCT00343005.

Year-to-year variation in the age-specific incidence of clinical malaria in two potential vaccine testing sites in Mali with different levels of malaria transmission intensity.

To explore the feasibility of field sites for malaria vaccine trials, we conducted a prospective study of clinical malaria incidence during two consecutive transmission seasons in children and young adults living in two areas of Mali with different entomologic inoculation rates (EIRs). Approximately 200 subjects (3 months to 2 years of age) were enrolled per site and followed weekly. Malaria smears were performed monthly in all participants and when symptoms or signs of malaria were present. In Sotuba (annual EIR < 15 infective bites per person), the incidence of clinical malaria was comparable across all age groups but varied significantly between the 2 years. In contrast, in Donéguébougou (annual EIR > 100 infective bites per person), incidence rates decreased significantly with increasing age but remained stable between years. Our results suggest that, although the age distribution of clinical malaria depends on transmission intensity, the total burden of disease may be similar or higher in settings of low transmission.

A randomized trial of artesunate-sulfamethoxypyrazine-pyrimethamine versus artemether-lumefantrine for the treatment of uncomplicated Plasmodium falciparum malaria in Mali.

The choice of artemisinin-based combination that is being adopted for malaria treatment in sub-Saharan Africa may depend on several factors, including cost, efficacy, side effects, and simplicity of administration. We tested the hypothesis that artesunate-sulfamethoxypyrazine-pyrimethamine is as efficacious as the four-dose regimen of artemether-lumefantrine for treatment of Plasmodium falciparum malaria. The study was carried out during two transmission seasons (2003 and 2004) in Sotuba, Mali. Participants at least 6 months of age with uncomplicated P. falciparum malaria were randomly assigned to receive artesunate-sulfamethoxypyrazine-pyrimethamine or artemether-lumefantrine. Treatment efficacy was assessed using the World Health Organization 28-day protocol. A total of 606 (303 in each arm) patients were enrolled. The cure rate was higher for artesunate-sulfamethoxypyrazine-pyrimethamine than for artemether-lumefantrine (98.7% versus 89.6%; P < 0.0001). After correction for cases of re-infection, the cure rates were 100% and 99.0%, respectively (P = 0.08). No serious adverse events occurred. Artesunate-sulfamethoxypyrazine-pyrimethamine is well-tolerated and effective against P. falciparum malaria. It showed an additional benefit of preventing new infections.

The etiology of severe anemia in a village and a periurban area in Mali.

Severe anemia is one of the major complications of malaria in Africa. We studied 2 populations, one in a village and the second in a periurban area in Mali, to understand the preventable factors in the disease. The 2 correlates of disease were parasitemia above 100 000 parasitized red blood cells per microliter (0.1 x 10(12)/L) and a low baseline hemoglobin level. All cases of moderate to severe anemia occurred in children under 3.2 years of age. Raising the baseline hemoglobin level and lowering peak parasitemia in infants and young children may reduce the incidence of severe anemia resulting from malarial infection.

Malaria incidence in relation to rice cultivation in the irrigated Sahel of Mali.

Seven repeated cross-sectional parasitological surveys, collecting a total of 13,912 blood samples, were carried out from September 1995 to February 1998 in three irrigated rice growing villages and three villages without irrigated agriculture in the area surrounding Niono, Mali. Parasite prevalence varied according to season and agricultural zone, but showed similar patterns for villages within the same zone. Overall, malaria prevalence was 47% in the villages without irrigated agriculture and 34% in the irrigated rice growing villages. In a village in the irrigated zone, and a village in the non-irrigated zone, 1067 and 608 children up to the age of 14 years, respectively, were followed in a passive malariological study for the period of 13 months. Fevers were attributed to malaria using a statistical method, taking into account the parasitaemia in afebrile controls from the cross-sectional surveys. The incidence of malaria fevers differed markedly between the two zones and over time. In the village in the irrigated zone, the incidence of malaria fevers was fairly constant over the year at 0.7 per 1000 children per day. In the village without irrigated agriculture, incidence was low during the dry season (at 0.6 per 1000 children per day), whereas it was high during the rainy season (at 3.2 per 1000 children per day). These results correspond well to the malaria transmission observed in a concurrent entomological survey. Rice cultivation in the semi-arid sub-Saharan environment altered the transmission pattern from seasonal to perennial, but reduced annual incidence more than two-fold.

A high malaria reinfection rate in children and young adults living under a low entomological inoculation rate in a periurban area of Bamako, Mali.

In areas of intense malaria parasite transmission, preliminary studies of the rate of reinfection after curative therapy suggest that small sample size studies of vaccine efficacy are feasible. However, the effect of transmission rate, which may vary considerably between transmission seasons, on reinfection rate has not been assessed in areas of mesoendemicity with seasonal transmission. To address this question, the Plasmodium falciparum reinfection rate after curative therapy was measured in Sotuba, a Malian village with historically low transmission rates, as estimated by the entomological inoculation rate (EIR). The reinfection rate after curative Fansidar (sulfadoxine-pyrimethamine) treatment was 80.7% (88/109). The EIR during the 13-week study period (seasonal transmission) varied between 1 and 4.5 infected bites/person/month. The finding that reinfection rates were high despite low EIRs suggests that a low EIR may be sufficient to support small sample size vaccine efficacy trials in mesoendemic areas.