Safety and Immunogenicity of Seven Dosing Regimens of the Candidate RTS,S/AS01E Malaria Vaccine Integrated Within an Expanded Program on Immunization Regimen: A Phase II, Single-Center, Open, Controlled Trial in Infants in Malawi

Malaria vaccine efficacy, safety, and community perception in Africa: a scoping review of recent empirical studies

AIM

The review summarizes the recent empirical evidence on the efficacy, safety, and community perception of malaria vaccines in Africa.

METHODS

Academic Search Complete, African Journals Online, CINAHL, Medline, PsychInfo, and two gray literature sources were searched in January 2023, and updated in June 2023. Relevant studies published from 2012 were included. Studies were screened, appraised, and synthesized in line with the review aim. Statistical results are presented as 95% Confidence Intervals and proportions/percentages.

RESULTS

Sixty-six (N = 66) studies met the inclusion criteria. Of the vaccines identified, overall efficacy at 12 months was highest for the R21 vaccine (N = 3) at 77.0%, compared to the RTS,S vaccine (N = 15) at 55%. The efficacy of other vaccines was BK-SE36 (11.0-50.0%, N = 1), ChAd63/MVA ME-TRAP (- 4.7-19.4%, N = 2), FMP2.1/AS02A (7.6-9.9%, N = 1), GMZ2 (0.6-60.0%, N = 5), PfPZ (20.0-100.0%, N = 5), and PfSPZ-CVac (24.8-33.6%, N = 1). Injection site pain and fever were the most common adverse events (N = 26), while febrile convulsion (N = 8) was the most reported, vaccine-related Serious Adverse Event. Mixed perceptions of malaria vaccines were found in African communities (N = 17); awareness was generally low, ranging from 11% in Tanzania to 60% in Nigeria (N = 9), compared to willingness to accept the vaccines, which varied from 32.3% in Ethiopia to 96% in Sierra Leone (N = 15). Other issues include availability, logistics, and misconceptions.

CONCLUSION

Malaria vaccines protect against malaria infection in varying degrees, with severe side effects rarely occurring. Further research is required to improve vaccine efficacy and community involvement is needed to ensure successful widespread use in African communities.

Systematic Review of Safety of RTS,S with AS01 and AS02 Adjuvant Systems Using Data from Randomized Controlled Trials in Infants, Children, and Adults

Background

Emergence of antimalarial drugs and insecticides resistance alarms scientists to develop a safe and effective malaria vaccine. A pre-erythrocytic malaria vaccine called RTS,S has made great strides.

Aim

The review was aimed to assess the safety of the candidate malaria vaccine RTS,S with AS01 and AS02 adjuvants using data from Phase I-III randomized controlled clinical trials (RCTs).

Methods

This systematic review was conducted based on PRISMA 2020. Regardless of time of publication year, all articles related with safety of RTS,S, RCTs published in the English language were included in the study. The last search of databases, and registry was conducted on 30 May, 2022. Pubmed, Google Scholar, Cochrane Library, Wiley Online Library, and Clinical trials.gov were thoroughly searched for accessible RCTs on the safety of RTS,S malaria vaccine. The studies were screened in three steps: duplicate removal, title and abstract screening, and full-text review. The included studies' bias risk was assessed using the Cochrane risk of bias tool for RCTs. This systematic review is registered at Prospero (registration number: CRD42021285888). The qualitative descriptive findings from the included published studies were reported stratified by clinical trial phases.

Findings

A total of thirty-five eligible safety studies were identified. Injection site pain and swelling, febrile convulsion, fever, headache, meningitis, fatigue, gastroenteritis, myalgia, pneumonia, reactogenicity, and anemia were the most commonly reported adverse events. Despite few clinical trials reported serious adverse events, none of them were related to vaccination.

Conclusion

Most of the adverse events observed from RTS,S/AS01 and RTS,S/AS02 malaria vaccines were reported in the control group and shared by other vaccines. Hence, the authors concluded that both RTS,S/AS01 and RTS,S/AS02 malaria vaccines are safe.

A chemokine-fusion vaccine targeting immature dendritic cells elicits elevated antibody responses to malaria sporozoites in infant macaques

Infants and young children are the groups at greatest risk for severe disease resulting from Plasmodium falciparum infection. We previously demonstrated in mice that a protein vaccine composed of the chemokine macrophage inflammatory protein 3α genetically fused to the minimally truncated circumsporozoite protein of P. falciparum (MCSP) elicits high concentrations of specific antibody and significant reduction of liver sporozoite load in a mouse model system. In the current study, a squalene based adjuvant (AddaVax, InvivoGen, San Diego, Ca) equivalent to the clinically approved MF59 (Seqiris, Maidenhead, UK) elicited greater antibody responses in mice than the previously employed adjuvant polyinosinic:polycytidylic acid, ((poly(I:C), InvivoGen, San Diego, Ca) and the clinically approved Aluminum hydroxide gel (Alum, Invivogen, San Diego, Ca) adjuvant. Use of the AddaVax adjuvant also expanded the range of IgG subtypes elicited by mouse vaccination. Sera passively transferred into mice from MCSP/AddaVax immunized 1 and 6 month old macaques significantly reduced liver sporozoite load upon sporozoite challenge. Protective antibody concentrations attained by passive transfer in the mice were equivalent to those observed in infant macaques 18 weeks after the final immunization. The efficacy of this vaccine in a relevant non-human primate model indicates its potential usefulness for the analogous high risk human population.

Immunization with full-length Plasmodium falciparum merozoite surface protein 1 is safe and elicits functional cytophilic antibodies in a randomized first-in-human trial

A vaccine remains a priority in the global fight against malaria. Here, we report on a single-center, randomized, double-blind, placebo and adjuvant-controlled, dose escalation phase 1a safety and immunogenicity clinical trial of full-length Plasmodium falciparum merozoite surface protein 1 (MSP1) in combination with GLA-SE adjuvant. Thirty-two healthy volunteers were vaccinated at least three times with MSP1 plus adjuvant, adjuvant alone, or placebo (24:4:4) to evaluate the safety and immunogenicity. MSP1 was safe, well tolerated and immunogenic, with all vaccinees sero-converting independent of the dose. The MSP1-specific IgG and IgM titers persisted above levels found in malaria semi-immune humans for at least 6 months after the last immunization. The antibodies were variant- and strain-transcending and stimulated respiratory activity in granulocytes. Furthermore, full-length MSP1 induced memory T-cells. Our findings encourage challenge studies as the next step to evaluate the efficacy of full-length MSP1 as a vaccine candidate against falciparum malaria (EudraCT 2016-002463-33).

PD-1 blockade promotes immune memory following Plasmodium berghei ANKA reinfection

The establishment of malaria immune memory is slow, incomplete, and short-lived. The mechanisms underpinning the generation and maintenance of anti-malarial immune memory remain unclear. This study evaluated the possible role of programmed cell death-1 (PD-1) in the establishment of malaria immune memory. Following infection by Plasmodium berghei ANKA (Pb ANKA) we compared natural immunity, acquired immunity, and immune memory between WT and mice lacking PD-1 via monoclonal antibody treatment. We found that parasitemia levels were significantly lower in the PD-1 knockdown group. After PD-1 elimination, dendritic cells, Th1, and T-follicular helper cells increased significantly. In addition, memory T, long-lived plasma cells, and serum antibody production also increased significantly. Therefore, PD-1 elimination induced stronger natural and acquired immune responses and enhanced immune memory against the parasite.

Immunomodulatory Nanosystems

Immunotherapy has emerged as an effective strategy for the prevention and treatment of a variety of diseases, including cancer, infectious diseases, inflammatory diseases, and autoimmune diseases. Immunomodulatory nanosystems can readily improve the therapeutic effects and simultaneously overcome many obstacles facing the treatment method, such as inadequate immune stimulation, off-target side effects, and bioactivity loss of immune agents during circulation. In recent years, researchers have continuously developed nanomaterials with new structures, properties, and functions. This Review provides the most recent advances of nanotechnology for immunostimulation and immunosuppression. In cancer immunotherapy, nanosystems play an essential role in immune cell activation and tumor microenvironment modulation, as well as combination with other antitumor approaches. In infectious diseases, many encouraging outcomes from using nanomaterial vaccines against viral and bacterial infections have been reported. In addition, nanoparticles also potentiate the effects of immunosuppressive immune cells for the treatment of inflammatory and autoimmune diseases. Finally, the challenges and prospects of applying nanotechnology to modulate immunotherapy are discussed.