Naturally acquired IgG antibodies against the C-terminal part of Plasmodium falciparum sporozoite threonine–asparagine-rich protein in a low endemic area

Abstract

Plasmodium falciparum sporozoite threonine-asparagine-rich protein (STARP), a 78-kDa surface protein, is considered a potential vaccine candidate. The C-terminal part of STARP has been evolved under positive selection, suggesting the presence of immunodominant epitopes. However, little is known about the immune responses against STARP among individuals upon natural malaria exposure. In this study, we have cloned and expressed in Escherichia coli the recombinant C-terminal part of STARP spanning 118 amino acids in order to examine the humoral immune response against this protein. Blood samples were randomly collected from 74 individuals living in a malaria endemic area of Thailand who were acutely infected with P. falciparum (n = 54) and with Plasmodium vivax (n = 20). Malaria-negative blood samples were also obtained from 27 individuals living in the same endemic area who had experienced prior infection with P. falciparum 6 months to 1 year before sample collection and 20 healthy subjects without history of malaria exposure. Western blot analysis revealed that IgG antibodies against this recombinant peptide were found in 23 of 54 serum samples (42.6%) from P. falciparum-infected individuals. All serum samples from P. vivax-infected cases, non-infected individuals, and those who experienced prior infection with P. falciparum gave negative results, indicating that naturally acquired IgG antibodies against the C-terminal part of STARP are species-specific and short-lived. Provided that antibodies against STARP could confer protection, it is likely that malaria vaccine derived from the C-terminal part of STARP could probably be boosted upon natural exposure to P. falciparum.

High-density Peptide Arrays Help to Identify Linear Immunogenic B-cell Epitopes in Individuals Naturally Exposed to Malaria Infection

“…Humoral responses to STARP are directed against the central repetitive domain and to the Rp10 region (54,76) which was also shown from our data to be highly immunogenic. Moreover, antibodies recognizing the C-terminal domain of STARP are generated during natural infection (77). By employing the peptide array technology and hence performing an epitope mapping, we discovered significant peptide hits within the C-terminal domain and the Rp45 region.…”

In silico design of knowledge-based Plasmodium falciparum epitope ensemble vaccines

“…RAP: Rhoptry-associated protein (Ghosh et al, 2017), UniProt: Q25730, Q25730_PLAFA. STRAP: Sporozoite threonine-asparagine-rich protein (Suwancharoen et al, 2011), UniProt: B0Z8E6, B0Z8E6_PLAFA.…”

High Sporozoite Antibody Titers in Conjunction with Microscopically Detectable Blood Infection Display Signatures of Protection from Clinical Malaria

“…In addition to NANP repeats, immune responses can also target regions in the amino- or carboxy-termini of CSP  (20–22) or additional sporozoite antigens, such as thrombospondin-related anonymous protein (23–25) or sporozoite threonine–asparagine-rich protein (26, 27). However, no single preerythrocytic antigen has yet been identified that serves as a correlate of naturally acquired protection against infection or clinical disease.…”