A Nonintegrative Lentiviral Vector-Based Vaccine Provides Long-Term Sterile Protection against Malaria

Unité Virologie Moléculaire et Vaccinologie, Department of Virology, Institut Pasteur and CNRS URA3015, Institut Pasteur, Paris, France.
PLoS ONE (Impact Factor: 3.23). 11/2012; 7(11):e48644. DOI: 10.1371/journal.pone.0048644
Source: PubMed


Trials testing the RTS,S candidate malaria vaccine and radiation-attenuated sporozoites (RAS) have shown that protective immunity against malaria can be induced and that an effective vaccine is not out of reach. However, longer-term protection and higher protection rates are required to eradicate malaria from the endemic regions. It implies that there is still a need to explore new vaccine strategies. Lentiviral vectors are very potent at inducing strong immunological memory. However their integrative status challenges their safety profile. Eliminating the integration step obviates the risk of insertional oncogenesis. Providing they confer sterile immunity, nonintegrative lentiviral vectors (NILV) hold promise as mass pediatric vaccine by meeting high safety standards. In this study, we have assessed the protective efficacy of NILV against malaria in a robust pre-clinical model. Mice were immunized with NILV encoding Plasmodium yoelii Circumsporozoite Protein (Py CSP) and challenged with sporozoites one month later. In two independent protective efficacy studies, 50% (37.5-62.5) of the animals were fully protected (p = 0.0072 and p = 0.0008 respectively when compared to naive mice). The remaining mice with detectable parasitized red blood cells exhibited a prolonged patency and reduced parasitemia. Moreover, protection was long-lasting with 42.8% sterile protection six months after the last immunization (p = 0.0042). Post-challenge CD8+ T cells to CSP, in contrast to anti-CSP antibodies, were associated with protection (r = -0.6615 and p = 0.0004 between the frequency of IFN-g secreting specific T cells in spleen and parasitemia). However, while NILV and RAS immunizations elicited comparable immunity to CSP, only RAS conferred 100% of sterile protection. Given that a better protection can be anticipated from a multi-antigen vaccine and an optimized vector design, NILV appear as a promising malaria vaccine.

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    • "For the sake of increased safety, lentiviral vaccine vectors were mutated to abolish integration of their genome into that of the hosts. This type of vectors was not only developed as prototypes for HIV vaccination [59] [60] but also malaria [61], Hepatatis [62] and human papilliomavirus [63]. "
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    • "IDLV was effective at eradicating established tumors in mice [17]. Recently, IDLV vaccination has also been shown to provide sterilizing immunity against malaria [18]. "
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    • "NILV are also being considered for gene transfer into slowly growing or non-dividing tissues where persistent episomal expression can provide a long-lasting therapeutic effect. An overview of vector components for many of these applications is provided in Table 1.[134]Vaccination is an application where only transient expression is required and NILVs have been shown to stimulate an efficient and sustained immune response[112,119,135,136]. Preclinical studies of NILVs have demonstrated immune responses against human papillomavirus (HPV), malaria, HIV-1 and the hepatitis B and C viruses[93,114,116117118120]thus showing their potential for use in vaccine development. One application where transient expression is preferred over sustained expression is in cell reprogramming. "

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