Peripheral Merozoite Surface Proteins Are Targets of Naturally Acquired Immunity against Malaria in both India and Ghana.

Development of a successful blood-stage vaccine against malaria remains a high priority. Immune-epidemiological studies are effective tools for the identification of antigenic targets of naturally acquired immunity (NAI) against malaria. However, differences in study design and methodology may compromise interstudy comparisons.

The circumsporozoite protein produced in is pure and stable.

The circumsporozoite protein (PfCSP) is a sporozoite surface protein whose role in sporozoite motility and cell invasion has made it the leading candidate for a pre-erythrocytic malaria vaccine. However, production of high yields of soluble recombinant PfCSP, including its extensive NANP and NVDP repeats, has proven problematic. Here, we report on the development and characterization of a secreted, soluble, and stable full-length PfCSP (containing 4 NVDP and 38 NANP repeats) produced in the expression system.

Plasmodium falciparum Clag9-Associated PfRhopH Complex Is Involved in Merozoite Binding to Human Erythrocytes.

Cytoadherence-linked asexual gene 9 (Clag9), a conserved protein expressed during the asexual blood stages, is involved in the cytoadherence of infected red blood cells (RBCs) to the endothelial lining of blood vessels. Here, we show that Clag9 (PfClag9) is a component of the PfClag9-RhopH complex that is involved in merozoite binding to human erythrocytes. To characterize PfClag9, we expressed four fragments of PfClag9, encompassing the entire protein.

Plasmodium falciparum MSP3 Exists in a Complex on the Merozoite Surface and Generates Antibody Response during Natural Infection.

merozoite surface protein 3 (MSP3) is an abundantly expressed secreted merozoite surface protein and a leading malaria vaccine candidate antigen. However, it is unclear how MSP3 is retained on the surface of merozoites without a glycosylphosphatidylinositol (GPI) anchor or a transmembrane domain. In the present study, we identified an MSP3-associated network on the merozoite surface by immunoprecipitation of merozoite lysate using antibody to the N terminus of MSP3 (anti-MSP3N) followed by mass spectrometry analysis.

Cytophilic Antibodies Against Key Plasmodium falciparum Blood Stage Antigens Contribute to Protection Against Clinical Malaria in a High Transmission Region of Eastern India.

Background: The collection of clinical data from a tribal population in a malaria-endemic area of India suggests the occurrence of naturally acquired immunity (NAI) against Plasmodium falciparum malaria.

Methods: Quantity and functionality of immunoglobulin G (IgG) antibodies against intact merozoites and recombinant proteins were assessed in a 13-month longitudinal cohort study of 121 individuals, 3-60 years of age.

Results: Opsonic phagocytosis of merozoites activity was strongly associated (hazard ratio [HR] = 0.

Lactococcus lactis provides an efficient platform for production of disulfide-rich recombinant proteins from Plasmodium falciparum.

Background: The production of recombinant proteins with proper conformation, appropriate post-translational modifications in an easily scalable and cost-effective system is challenging. Lactococcus lactis has recently been identified as an efficient Gram positive cell factory for the production of recombinant protein. We and others have used this expression host for the production of selected malaria vaccine candidates.

Protein-protein interaction studies reveal the merozoite surface protein-1 region involved in a complex formation that binds to human erythrocytes.

merozoite surface protein (PfMSP) 1 has been studied extensively as a vaccine candidate antigen. PfMSP-1 undergoes proteolytic processing into four major products, such as p83, p30, p38, and p42, that are associated in the form of non-covalent complex(s) with other MSPs. To delineate MSP1 regions involved in the interaction with other MSPs, here we expressed recombinant proteins (PfMSP-1) encompassing part of p38 and p42 regions and PfMSP-1 PfMSP-1 interacted strongly with PfMSP-3, PfMSP-6, PfMSP-7, and PfMSP-9, whereas PfMSP-1 did not interact with any of these proteins.

Human Cyclophilin B forms part of a multi-protein complex during erythrocyte invasion by Plasmodium falciparum.

Invasion of human erythrocytes by Plasmodium falciparum merozoites involves multiple interactions between host receptors and their merozoite ligands. Here we report human Cyclophilin B as a receptor for PfRhopH3 during merozoite invasion. Localization and binding studies show that Cyclophilin B is present on the erythrocytes and binds strongly to merozoites.

Construct design, production, and characterization of Plasmodium falciparum 48/45 R0.6C subunit protein produced in Lactococcus lactis as candidate vaccine.

Background: The sexual stages of Plasmodium falciparum are responsible for the spread of the parasite in malaria endemic areas. The cysteine-rich Pfs48/45 protein, exposed on the surface of sexual stages, is one of the most advanced antigens for inclusion into a vaccine that will block transmission. However, clinical Pfs48/45 sub-unit vaccine development has been hampered by the inability to produce high yields of recombinant protein as the native structure is required for the induction of functional transmission-blocking (TB) antibodies.

Identification of an N-terminal 27 kDa fragment of Mycoplasma pneumoniae P116 protein as specific immunogen in M. pneumoniae infections.

Background: Mycoplasma pneumoniae is an important cause of respiratory tract infection and is increasingly being associated with other diseases such as asthma and extra-pulmonary complications. Considerable cross-reactivity is known to exist between the whole cell antigens used in the commercial serological testing assays. Identification of specific antigens is important to eliminate the risk of cross-reactions among different related organisms.