SPf66 malaria vaccine is safe and immunogenic in malaria naive adults in Thailand

The effect of chronic stress on the immunogenicity and immunoprotection of the M6-TT vaccine in female mice

Active vaccination is an effective therapeutic option to reduce the reinforcing effects of opioids. Several studies showed that chronic stress affects the immune system decreasing the efficiency of some vaccines. Heroin withdrawal is a stressor and it is a stage in which the patient who abuses heroin is vulnerable to stress affects the immune response and consequently its immunoprotective capacity, then, the objective was to determine the effect of heroin-withdrawal and heroin-withdrawal plus immobilization, on the immune (immunogenicity) and protective response (behavioral response) of morphine-6-hemisuccinate-tetanus toxoid (M6-TT) vaccine in animals of two inbred mice strains with different sensitivity to drug-opioid and stress. Female BALB/c and C57Bl/6 inbred mice were immunized with the M6-TT. A solid-phase antibody-capture ELISA was used to monitor antibody titer responses after each booster dose in vaccinated animals. During the vaccination period, the animals were subjected to two different stress conditions: drug-withdrawal (DW) and immobilization (IMM). The study used tail-flick testing to evaluate the heroin-induced antinociceptive effects. Additionally, heroin-induced locomotor activity was evaluated. Stress decreased the heroin-specific antibody titer generated by the M6-TT vaccine in the two inbred mouse strains evaluated. In the two stress conditions, the antibody titer was not able to decrease the heroin-induced antinociceptive effects and locomotor activity. These findings suggest that stress decreases the production of antibodies and the immunoprotective capacity of the M6-TT vaccine. This observation is important to determine the efficacy of active vaccination as a potential therapy for patients with opioid drug use disorder, since these patients during drug-withdrawal present stress disorders, which could affect the efficacy of therapy such as active vaccination.

Sex differences in concentrations of HMGB1 and numbers of pigmented monocytes in infants and young children with malaria

Sex remains a key biological variable affecting human innate and adaptive immune responses to infection and in pathogenesis of diseases. In malaria, females demonstrate higher concentrations of antibodies and rates of severe adverse events and mortality following malaria vaccination. Although monocytes/macrophages play a crucial role in disease and protection in malaria, no studies have investigated sex differences in their functions in production of proinflammatory cytokines and chemokines in malaria-infected subjects. Here, we show significant sex differences in serum concentrations of HMGB1, a non-histone chromatin-associated protein, and numbers of pigmented monocytes, which are both markers of severe malaria, in infants and young children <5 years old from a malaria endemic region in Northern Uganda. Female infants and young children with clinical malaria had significantly higher HMGB1 concentrations than males, and female infants and young children with asymptomatic malaria had significantly lower numbers of pigmented monocytes than males with asymptomatic malaria. There was (1) a significant correlation between HMGB1 concentrations and pigmented monocyte numbers in female but not male infants; and (2) a significant correlation between HMGB1 concentrations and parasite densities in female but not male infants. These findings suggest that female infants and young children with clinical malaria might be at a greater risk of morbidity characterized by higher serum HMGB1 levels.

Irradiated sporozoite vaccination induces sex-specific immune responses and protection against malaria in mice

In both preclinical animal studies and human clinical trials, adult females tend to develop greater adaptive immune responses than males following receipt of either viral or bacterial vaccines. While there is currently no approved malaria vaccine, several anti-sporozoite vaccines, including RTS,S/AS01 and attenuated sporozoite vaccines, are in development, but the impact of sex and age on their efficacy remains undefined. To examine sex differences in the efficacy of anti-sporozoite stage malaria vaccination, adult (10 weeks of age) or juvenile (11 days of age) male and female C3H mice were twice vaccinated with irradiated transgenic Plasmodium berghei sporozoites expressing the P. falciparum circumsporozoite (CSP) protein and 45 days post boost vaccination, mice were challenged with transgenic P. berghei via mosquito bite or intradermal challenge. Immunization with irradiated sporozoites resulted in greater protection against challenge in adult females, which was associated with greater anti-CSP antibody production and avidity, as well as greater hepatic, but not splenic, CD8+ T cell IFNƴ production in adult females than adult males. No sex differences in adaptive immune responses or protection were observed in mice vaccinated prior to puberty, suggesting a role for sex steroid hormones. Depletion of testosterone in males increased, whereas rescue of testosterone decreased, anti-CSP antibody production, the number of antigen-specific CD8+ T cells isolated from the liver, and protection following parasite challenge. Conversely, depletion of sex steroids in female mice did not alter vaccine-induced responses or protection following challenge. These data suggest that elevated testosterone concentrations in males reduce adaptive immunity and contribute to sex differences in malaria vaccine efficacy.

WITHDRAWN: Vaccines for preventing malaria

BACKGROUND

Four types of malaria vaccine, SPf66 and MSP/RESA vaccines (against the asexual stages of the Plasmodium parasite) and CS-NANP and RTS,S vaccines (against the sporozoite stages), have been tested in randomized controlled trials in endemic areas.

OBJECTIVES

To assess malaria vaccines against Plasmodium falciparum, P. vivax, P. malariae and P ovale in preventing infection, disease and death.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group Specialized Register (April 2004), CENTRAL (The Cochrane Library Issue 2, 2004), MEDLINE (1966 to April 2004), EMBASE (1980 to April 2004), Science Citation Index (1981 to April 2004), and reference lists of articles. We also contacted organizations and researchers in the field.

SELECTION CRITERIA

Randomized controlled trials comparing vaccines against Plasmodium falciparum, P. vivax, P. malariae or P. ovale with placebo or routine antimalarial control measures in people of any age receiving a challenge malaria infection.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data.

MAIN RESULTS

Eighteen efficacy trials involving 10,971 participants were included. There were ten trials of SPf66 vaccine, four trials of CS-NANP vaccines, two trials of RTS,S vaccine, and two of MSP/RESA vaccine. Results with SPf66 in reducing new malaria infections (P. falciparum) were heterogeneous: it was not effective in four African trials (Peto odds ratio (OR) 0.96, 95% confidence interval (CI) 0.81 to 1.14), but in five trials outside Africa the number of first attacks was reduced (Peto OR 0.77, 95% CI 0.67 to 0.88). Trials to date have not indicated any serious adverse events with SPf66 vaccine. In three trials of CS-NANP vaccines, there was no evidence for protection by these vaccines against P. falciparum malaria (Peto OR 1.12, 95% CI 0.64 to 1.93). In a small trial in non-immune adults in the USA, RTS,S gave strong protection against experimental infection with P. falciparum. In a trial in an endemic area of the Gambia in semi-immune people, there was a reduction in clinical malaria episodes in the second year of follow up, corresponding to a vaccine efficacy of 66% (CI 14% to 85%). In a trial in Papua New Guinea, MSP/RESA had no protective effect against episodes of clinical malaria. There was evidence of an effect on parasite density, but this differed according to whether the participants had been pretreated with sulfadoxine/pyrimethamine or not. The prevalence of infections with the parasite subtype of MSP2 in the vaccine was reduced compared with the other subtype (Peto OR 0.35, CI 0.23 to 0.53).

AUTHORS' CONCLUSIONS

There is no evidence for protection by SPf66 vaccines against P. falciparum in Africa. There is a modest reduction in attacks of P. falciparum malaria following vaccination with SPf66 in other regions. Further research with SPf66 vaccines in South America or with new formulations of SPf66 may be justified. There was not enough evidence to evaluate the use of CS-NANP vaccines. The RTS,S vaccine showed promising result, as did the MSP/RESA vaccine, but it should include the other main allelic form of MSP2. The MSP/RESA trial demonstrated that chemotherapy during a vaccine trial may reduce vaccine efficacy, and trials should consider very carefully whether this practice is justified.

Short-term reactogenicity and gender effect of anthrax vaccine: analysis of a 1967–1972 study and review of the 1955–2005 medical literature

PURPOSE

In the 1960s, the Centers for Disease Control and Prevention (CDC) held the investigational new drug (IND) application for the anthrax vaccine and collected short-term safety data from approximately 16,000 doses administered to almost 7000 individuals. While some recent anthrax vaccine safety studies have suggested that women experience more injection site reactions (ISRs), to our knowledge the IND safety data were not previously examined for a gender-specific difference.

METHODS

We identified and analyzed a subset of the IND study data representing a total of 1749 persons who received 3592 doses from 1967 to 1972. Original data collection forms were located and information extracted, including: vaccine recipient's name, age at vaccination, gender, dose number, date of vaccination, lot number, grading of ISR, presence and type of systemic reactions. Overall and gender-specific rates for adverse reactions to anthrax vaccine were calculated and we performed a multivariable analysis.

RESULTS

We found an ISR was associated with 28% of anthrax vaccine doses; however, 87% of these were considered mild. Systemic reactions were uncommon (<1%) and most (70%) accompanied an ISR. Our dose-specific analysis by gender found women had at least twice the risk of having a vaccine reaction compared to men. Our age-adjusted relative risk for ISR in women compared to men was 2.78 (95%CI: 2.29, 3.38).

CONCLUSIONS

Our results for both overall and gender-specific reactogenicity are consistent with other anthrax safety studies. To date, possible implications of these gender differences observed for anthrax and other vaccines are unknown and deserve further study.

Glutamate-rich protein (GLURP) induces antibodies that inhibit in vitro growth of Plasmodium falciparum in a phase 1 malaria vaccine trial

The glutamate-rich protein (GLURP) of P. falciparum is the target of cytophilic antibodies which are significantly associated with protection against clinical malaria. A phase 1 clinical trial was conducted in healthy adult volunteers with the long synthetic peptide (LSP) GLURP(85-213) combined with either Aluminum Hydroxide (Alum, 18 volunteers) or Montanide ISA 720 (ISA, 18 volunteers) as adjuvants. Immunizations with 10, 30 or 100 microg GLURP(85-213) were administered subcutaneously at days 0, 30, and 120. Adverse events occurred more frequently with increasing dosage of GLURP(85-213) LSP and were more prevalent in the ISA group. Serious vaccine-related adverse events were not observed. The vaccine induced dose-dependent cellular and humoral immune responses, with high levels of (mainly cytophilic IgG1) antibodies that recognize parasites by immunofluorescence (IFA). Plasma samples collected 30 days after the last immunization induced a dose-dependent inhibition of parasite growth in vitro in the presence of monocytes. In conclusion, immunizations with GLURP(85-213) LSP formulations induce adverse events but can be administered safely, generating antibodies with capacity to mediate growth-inhibitory activity against P. falciparum in vitro.

Vaccines for preventing malaria (SPf66)

BACKGROUND

A malaria vaccine is badly needed. SPf66 was one of the earliest vaccines developed. It is a synthetic peptide vaccine containing antigens from the blood stages of malaria linked together with an antigen from the sporozoite stage, and is targeted mainly against the blood (asexual) stages.

OBJECTIVES

To assess the effect of SPf66 malaria vaccines against Plasmodium falciparum, P. vivax, P. malariae, and P. ovale in preventing infection, disease, and death.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group Specialized Register (September 2005), CENTRAL (The Cochrane Library 2005, Issue 3), MEDLINE (1966 to September 2005), EMBASE (1980 to September 2005), LILACS (1982 to September 2005), Science Citation Index (1981 to September 2005), and reference lists of articles. We also contacted organizations and researchers in the field.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials comparing SPf66 vaccine with placebo or routine antimalarial control measures in people of any age receiving an artificial challenge or natural exposure to malaria infection (any species).

DATA COLLECTION AND ANALYSIS

Two people independently assessed trial quality and extracted data, including adverse events. Results were expressed as relative risks (RR) with 95% confidence intervals (CI).

MAIN RESULTS

Ten efficacy trials of SPf66 involving 9698 participants were included. Results with SPf66 in reducing new episodes of P. falciparum malaria were heterogeneous: it was not effective in four African trials (RR 0.98, 95% CI 0.90 to 1.07; 2371 participants) or in one Asian trial (RR 1.06, 95% CI 0.90 to 1.25; 1221 participants). In four trials in South America the number of first attacks with P. falciparum was reduced by 28% (RR 0.72, 95% CI 0.63 to 0.82; 3807 participants). It did not reduce episodes of P. vivax malaria or admission to hospital with severe malaria. Trials have not indicated any serious adverse events with SPf66 vaccine.

AUTHORS' CONCLUSIONS

There is no evidence for protection by SPf66 vaccines against P. falciparum in Africa. There is a modest reduction in attacks of P. falciparum malaria following vaccination with SPf66 in South America. There is no justification for further trials of SPf66 in its current formulation. Further research with SPf66 vaccines in South America or with new formulations of SPf66 may be justified.

A malaria vaccine that elicits in humans antibodies able to kill Plasmodium falciparum

BACKGROUND

Plasmodium falciparum merozoite surface protein 3 is a malaria vaccine candidate that was identified, characterised, and developed based on a unique immuno-clinical approach. The vaccine construct was derived from regions fully conserved among various strains and containing B cell epitopes targeted by human antibodies (from malaria-immune adults) that are able to mediate a monocyte-dependent parasite killing effect. The corresponding long synthetic peptide was administered to 36 volunteers, with either alum or Montanide ISA720 as adjuvant.

METHODS AND FINDINGS

Both formulations induced cellular and humoral immune responses. With alum, the responses lasted up to 12 mo. The vaccine-induced antibodies were predominantly of cytophilic classes, i.e., able to cooperate with effector cells. In vitro, the antibodies induced an inhibition of the P. falciparum erythrocytic growth in a monocyte-dependent manner, which was in most instances as high as or greater than that induced by natural antibodies from immune African adults. In vivo transfer of the volunteers' sera into P. falciparum-infected humanized SCID mice profoundly reduced or abrogated parasitaemia. These inhibitory effects were related to the antibody reactivity with the parasite native protein, which was seen in 60% of the volunteers, and remained in samples taken 12 mo postimmunisation.

CONCLUSION

This is the first malaria vaccine clinical trial to clearly demonstrate antiparasitic activity by vaccine-induced antibodies by both in vitro and in vivo methods. The results, showing the induction of long-lasting antibodies directed to a fully conserved polypeptide, also challenge current concepts about malaria vaccines, such as unavoidable polymorphism, low antigenicity, and poor induction of immune memory.

Current status of malaria vaccine development

There is an urgent need to develop an effective vaccine against malaria--a disease that has approximately 10% of the world population at risk of infection at any given time. The economic burden this disease puts on the medico-social set-up of countries in Sub-Saharan Africa and South East Asia is phenomenal. Increasing drug resistance and failure of vector control strategies have necessitated the search for a suitable vaccine that could be integrated into the extended program of immunization for countries in the endemic regions. Malaria vaccine development has seen a surge of activity in the last decade or so owing largely to the advances made in the fields of genetic engineering and biotechnology. This revolution has brought sweeping changes in the understanding of the biology of the parasite and has helped formulate newer more effective strategies to combat the disease. Latest developments in the field of malaria vaccine development will be discussed in this chapter.

Vaccines for preventing malaria

BACKGROUND

Four types of malaria vaccine, SPf66 and MSP/RESA vaccines (against the asexual stages of the Plasmodium parasite) and CS-NANP and RTS,S vaccines (against the sporozoite stages), have been tested in randomized controlled trials in endemic areas.

OBJECTIVES

To assess malaria vaccines against Plasmodium falciparum, P. vivax, P. malariae and P ovale in preventing infection, disease and death.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group trials register (July 2002), the Cochrane Controlled Trials Register (The Cochrane Library Issue 2, 2002), MEDLINE (1966 to July 2002), EMBASE (1980 to May 2002), Science Citation Index (1981 to July 2002), and reference lists of articles. We also contacted organizations and researchers in the field.

SELECTION CRITERIA

Randomized controlled trials comparing vaccines against Plasmodium falciparum, P. vivax, P. malariae or P. ovale with placebo or routine antimalarial control measures in people of any age receiving a challenge malaria infection.

DATA COLLECTION AND ANALYSIS

Two reviewers independently assessed trial quality and extracted data.

MAIN RESULTS

Eighteen efficacy trials involving 10,971 participants were included. There were ten trials of SPf66 vaccine, four trials of CS-NANP vaccines, two trials of RTS,S vaccine, and two of MSP/RESA vaccine. Results with SPf66 in reducing new malaria infections (P. falciparum) were heterogeneous: it was not effective in four African trials (Peto odds ratio (OR) 0.96, 95% confidence interval (CI) 0.81 to 1.14), but in five trials outside Africa the number of first attacks was reduced (Peto OR 0.77, 95% CI 0.67 to 0.88). Trials to date have not indicated any serious adverse events with SPf66 vaccine. In three trials of CS-NANP vaccines, there was no evidence for protection by these vaccines against P. falciparum malaria (Peto OR 1.12, 95% CI 0.64 to 1.93). In a small trial in non-immune adults in the USA, RTS,S gave strong protection against experimental infection with P. falciparum. In a trial in an endemic area of the Gambia in semi-immune people, there was a reduction in clinical malaria episodes in the second year of follow up, corresponding to a vaccine efficacy of 66% (CI 14% to 85%). In a trial in Papua New Guinea, MSP/RESA had no protective effect against episodes of clinical malaria. There was evidence of an effect on parasite density, but this differed according to whether the participants had been pretreated with sulfadoxine/pyrimethamine or not. The prevalence of infections with the parasite subtype of MSP2 in the vaccine was reduced compared with the other subtype (Peto OR 0.35, CI 0.23 to 0.53).

REVIEWER'S CONCLUSIONS

There is no evidence for protection by SPf66 vaccines against P. falciparum in Africa. There is a modest reduction in attacks of P. falciparum malaria following vaccination with SPf66 in other regions. Further research with SPf66 vaccines in South America or with new formulations of SPf66 may be justified. There was not enough evidence to evaluate the use of CS-NANP vaccines. The RTS,S vaccine showed promising result, as did the MSP/RESA vaccine, but it should include the other main allelic form of MSP2. The MSP/RESA trial demonstrated that chemotherapy during a vaccine trial may reduce vaccine efficacy, and trials should consider very carefully whether this practice is justified.