Development of an effective vaccine is critically needed for the prevention of malaria. One of the key antigens for malaria vaccines is the apical membrane antigen 1 (AMA-1) of the human malaria parasite Plasmodium falciparum, the surface protein for erythrocyte invasion of the parasite. The gene encoding AMA-1 has been sequenced from populations of P. falciparum worldwide, but the haplotype diversity of the gene in P. falciparum populations in the Greater Mekong Subregion (GMS), including Thailand, remains to be characterized. In the present study, the AMA-1 gene was PCR amplified and sequenced from the genomic DNA of 65 P. falciparum isolates from 5 endemic areas in Thailand. The nearly full-length 1,848 nucleotide sequence of AMA-1 was subjected to molecular analyses, including nucleotide sequence diversity, haplotype diversity and deduced amino acid sequence diversity and neutrality tests. Phylogenetic analysis and pairwise population differentiation (F( st) indices) were performed to infer the population structure. The analyses identified 60 single nucleotide polymorphic loci, predominately located in domain I of AMA-1. A total of 31 unique AMA-1 haplotypes were identified, which included 11 novel ones. The phylogenetic tree of the AMA-1 haplotypes revealed multiple clades of AMA-1, each of which contained parasites of multiple geographical origins, consistent with the F(st) indices indicating genetic homogeneity or gene flow among geographically distinct populations of P. falciparum in Thailand's borders with Myanmar, Laos and Cambodia. In summary, the study revealed novel haplotypes and population structure needed for the further advancement of AMA-1-based malaria vaccines in the GMS.
Amino Acid Sequence ; Base Sequence ; Cambodia ; DNA ; Erythrocytes ; Gene Flow ; Haplotypes ; Humans ; Laos ; Malaria ; Malaria Vaccines ; Membranes ; Myanmar ; Parasites ; Plasmodium falciparum ; Plasmodium ; Polymerase Chain Reaction ; Polymorphism, Genetic ; Thailand ; Trees

Malaria is an infectious disease affecting humans, which is transmitted by the bite of Anopheles mosquitoes harboring sporozoites of parasitic protozoans belonging to the genus Plasmodium. Despite past achievements to control the protozoan disease, malaria still remains a significant health threat up to now. In this study, we cloned and characterized the full-unit Plasmodium yoelii genes encoding merozoite surface protein 1 (MSP1), circumsporozoite protein (CSP), and Duffy-binding protein (DBP), each of which can be applied for investigations to obtain potent protective vaccines in the rodent malaria model, due to their specific expression patterns during the parasite life cycle. Recombinant fragments corresponding to the middle and C-terminal regions of PyMSP1 and PyCSP, respectively, displayed strong reactivity against P. yoelii-infected mice sera. Specific native antigens invoking strong humoral immune response during the primary and secondary infections of P. yoelii were also abundantly detected in experimental ICR mice. The low or negligible parasitemia observed in the secondary infected mice was likely to result from the neutralizing action of the protective antibodies. Identification of these antigenic proteins might provide the necessary information and means to characterize additional vaccine candidate antigens, selected solely on their ability to produce the protective antibodies.
Animals ; Anopheles ; Antibodies ; Clone Cells ; Coinfection ; Communicable Diseases ; Culicidae ; Humans ; Immunity, Humoral ; Life Cycle Stages ; Malaria ; Merozoite Surface Protein 1* ; Mice ; Mice, Inbred ICR ; Parasitemia ; Parasites ; Plasmodium yoelii* ; Plasmodium* ; Rodentia ; Sporozoites ; Vaccines

Travel-related health problems such as febrile illness have been reported in many travelers going to developing countries. With the emergence of new infectious diseases occurring in many parts of the world and their spread worldwide, early diagnosis of emerging infectious diseases or tropical diseases has become a very important part of controlling these diseases. In doing so, the itinerary of the ill returning traveler is crucial to formulating a differential diagnosis because exposure to pathogens differs depending on the area of travel. With up-to-date information on infectious diseases occurring worldwide, a differential diagnosis can be made by adding information on duration of travel, incubation period, underlying medical illness, history of prophylactic vaccines received, and knowledge of the patient's exposures during travel including insect bites, contaminated food or water, or freshwater swimming. Some travelers may have specific symptoms and signs such as fever, rash, or hemorrhagic manifestations. For example, eosinophilia suggests a possible helminth infection. In this article, the general approach to returnning travelers with suspected tropical disease will be described.
Communicable Diseases ; Communicable Diseases, Emerging ; Dengue ; Developing Countries ; Diagnosis, Differential* ; Early Diagnosis ; Eosinophilia ; Exanthema ; Fever ; Fresh Water ; Helminths ; Insect Bites and Stings ; Malaria ; Swimming ; Travel Medicine ; Vaccines ; Water

BACKGROUND: Travel-related risks for infectious diseases vary depending on travel patterns such as purpose, destination, and duration. In this study, we describe the patterns of travel and prescription of vaccines as well as malaria prophylaxis medication (MPM) at a travel clinic in South Korea to identify the gaps to fill for the optimization of pre-travel consultation. MATERIALS AND METHODS: A cohort of travel clinic visitors in 2011 was constructed and early one-third of the visitors of each month were reviewed. During the study period, 10,009 visited the travel clinic and a retrospective chart review was performed for 3,332 cases for analysis of travel patterns and prescriptions. RESULTS: People receiving yellow fever vaccine (YFV) (n = 2,933) were traveling more frequently for business and tourism and less frequently for providing non-medical service or research/education compared to the 399 people who did not receive the YFV. Overall, most people were traveling to Eastern Africa, South America, and Western Africa, while South-Eastern Asia was the most common destination for the non-YFV group. Besides YFV, the typhoid vaccine was the most commonly prescribed (54.2%), while hepatitis A presented the highest coverage (74.7%) considering the natural immunity, prior and current vaccination history. Additionally, 402 (82.5%) individuals received a prescription for MPM among the 487 individuals travelling to areas with high-risk of malaria infection. Age over 55 was independently associated with receiving MPM prescription, while purpose of providing service and travel duration over 10 days were associated with no MPM prescription, despite travelling to high-risk areas. CONCLUSION: Eastern Africa and South America were common travel destinations among the visitors to a travel clinic for YFV, and most of them were travelling for tourism and business. For the individuals who are traveling to areas with high-risk for malaria, more proactive approach might be required in case of younger age travelers, longer duration, and travel purpose of providing service to minimize the risk of malaria infection.
Africa, Eastern ; Africa, Western ; Antibiotic Prophylaxis ; Asia ; Cohort Studies ; Commerce ; Communicable Diseases ; Hepatitis A ; Immunity, Innate ; Korea* ; Malaria ; Prescriptions* ; Retrospective Studies ; South America ; Travel Medicine ; Typhoid-Paratyphoid Vaccines ; Vaccination* ; Vaccines ; Yellow Fever Vaccine ; Yellow Fever*

Malaria is a major cause of mortality and morbidity globally. Great efforts have been made in the prevention and the elimination of malaria, especially in controlling the malaria vector, the mosquito. Another promising approach would be the development of malaria vaccines. Malaria vaccine studies can be focused on the pre-erythrocytic-stage antigens and the blood-stage antigens, and on the transmission blocking agents targeting the malaria gametocytes. The blood-stage antigens are the leading candidates in malaria vaccine development, as the blood-stage parasites are responsible for causing symptomatic malaria. Human acquired immunity largely targets on blood-stage antigens. This review focuses on one of the most extensively studied blood-stage antigen, the merozoite surface protein-1 (MSP-1), specifically on its evaluation and immunogenicity in rodents and primate models, and its safety and immunogenicity in human clinical trials.
Malaria Vaccines

Vaccines are considered as one of the major contributions of the 20th century and one of the most cost effective public health interventions. The International Vaccine Institute has as a mission to discover, develop and deliver new and improved vaccines against infectious diseases that affects developing nations. If Louis Pasteur is known across the globe, vaccinologists like Maurice Hilleman, Jonas Salk and Charles Merieux are known among experts only despite their contribution to global health. Thanks to a vaccine, smallpox has been eradicated, polio has nearly disappeared, Haemophilus influenzae B, measles and more recently meningitis A are controlled in many countries. While a malaria vaccine is undergoing phase 3, International Vaccine Institute, in collaboration with an Indian manufacturer has brought an oral inactivated cholera vaccine to pre-qualification. The field of vaccinology has undergone major changes thanks to philanthropists such as Bill and Melinda Gates, initiatives like the Decade of Vaccines and public private partnerships. Current researches on vaccines have more challenging targets like the dengue viruses, malaria, human immunodeficiency virus, the respiratory syncytial virus and nosocomial diseases. Exciting research is taking place on new adjuvants, nanoparticles, virus like particles and new route of administration. An overcrowded infant immunization program, anti-vaccine groups, immunizing a growing number of elderlies and delivering vaccines to difficult places are among challenges faced by vaccinologists and global health experts.
Cholera ; Communicable Diseases ; Cooperative Behavior ; Dengue Virus ; Developing Countries ; Haemophilus influenzae ; HIV ; Humans ; Hypogonadism ; Immunization Programs ; Infant ; Malaria ; Measles ; Meningitis ; Missions and Missionaries ; Mitochondrial Diseases ; Nanoparticles ; Ophthalmoplegia ; Poliomyelitis ; Public Health ; Public-Private Sector Partnerships ; Respiratory Syncytial Viruses ; Smallpox Vaccine ; Vaccines ; Viruses

The current status of malaria vaccine approaches has the background of a long and arduous path of malaria disease control and vaccine development. Here, we critically review with regard to unilateral interventional approaches and highlight the impact of socioeconomic elements of malaria endemicity. The necessity of re-energizing basic research of malaria life-cycle and Plasmodium developmental biology to provide the basis for promising and cost-effective vaccine approaches and to reach eradication goals is more urgent than previously believed. We closely analyse the flaws of various vaccine approaches, outline future directions and challenges that still face us and conclude that the focus of the field must be shifted to the basic research efforts including findings on the skin stage of infection. We also reflect on economic factors of vaccine development and the impact of public perception when it comes to vaccine uptake.
Biomedical Research ; Humans ; Malaria ; prevention & control ; Malaria Vaccines

Relatively little has been studied on the AMA-1 vaccine against Plasmodium vivax and on the plasmid DNA vaccine encoding P. vivax AMA-1 (PvAMA-1). In the present study, a plasmid DNA vaccine encoding AMA-1 of the reemerging Korean P. vivax has been constructed and a preliminary study was done on its cellular immunogenicity to recipient BALB/c mice. The PvAMA-1 gene was cloned and expressed in the plasmid vector UBpcAMA-1, and a protein band of approximately 56.8 kDa was obtained from the transfected COS7 cells. BALB/c mice were immunized intramuscularly or using a gene gun 4 times with the vaccine, and the proportions of splenic T-cell subsets were examined by fluorocytometry at week 2 after the last injection. The spleen cells from intramuscularly injected mice revealed no significant changes in the proportions of CD8+ T-cells and CD4+ T-cells. However, in mice immunized using a gene gun, significantly higher (P<0.05) proportions of CD8+ cells were observed compared to UB vector-injected control mice. The results indicated that cellular immunogenicity of the plasmid DNA vaccine encoding AMA-1 of the reemerging Korean P. vivax was weak when it was injected intramuscularly; however, a promising effect was observed using the gene gun injection technique.
Animals ; Antigens, Protozoan/administration & dosage/genetics/*immunology ; CD8-Positive T-Lymphocytes/*immunology ; COS Cells ; Cercopithecus aethiops ; Humans ; Lymphocyte Activation ; Malaria, Vivax/*immunology/parasitology ; Membrane Proteins/administration & dosage/genetics/*immunology ; Mice ; Mice, Inbred BALB C ; Plasmodium vivax/genetics/*immunology ; Protozoan Proteins/administration & dosage/genetics/*immunology ; Protozoan Vaccines/administration & dosage/genetics/*immunology ; Vaccines, DNA/administration & dosage/genetics/*immunology

Although the development of vaccines has been one of the most important contributions of immunology to medicine and public health, and despite vaccination having been proven as the most effective and cheapest medical practice to prevent infectious diseases, infectious diseases still remain the main cause of human deaths and new infectious diseases continue to emerge. Furthermore, we face an unprecedented succession of new pathogens able to jump species barriers and infect humans, even as we continue to be frustrated in our efforts to control devastating diseases such as HIV, malaria and tuberculosis. Hence the need to develop new vaccines and improve existing vaccines. Other challenges for scientists include rapid identification and response to emerging diseases and successful intervention in re-emerging infectious diseases. Remarkable progress in molecular biology and biotechnology is making possible the development and improvement of new and old vaccines. Recombinant DNA technology, genetic attenuation of viral and bacterial pathogens and their use as vectors for heterologous proteins, naked DNA vaccines and peptide vaccines represent the most popular approaches hitherto adopted. Reverse genetics and reverse vaccinology are now used to investigate new vaccines. Genome-based reverse vaccinology is very useful and a major tool in vaccine development. The rapid identification of the genome sequence to new pathogens enables the speedy development of diagnostic tools as well as recombinant expression of targets for vaccine. Strengthening research and development in vaccines, including international cooperation, may be the most effective next step to control and prevent infectious diseases worldwide.
Allergy and Immunology ; Biotechnology ; Communicable Diseases ; Communicable Diseases, Emerging* ; DNA, Recombinant ; Genome ; HIV ; Humans ; International Cooperation ; Malaria ; Molecular Biology ; Public Health ; Reverse Genetics ; Tuberculosis ; Vaccination ; Vaccines ; Vaccines, DNA ; Vaccines, Subunit

OBJECTIVETo study the expression of green fluorescent protein gene and immunogenicity of ES312 vaccine both mediated by Starburst polyamidoamine (PAMAM) dendrimers in vivo.

METHODSThe complex of green fluorescent protein or ES312 gene with Starburst PAMAM dendrimers were injected intramuscularly in Balb/c mice. The expression level and distribution of green fluorescent protein gene was detected by flow cytometer, Western blot and immunofluorescence assay. The immunogenicity of DNA vaccine was detected by enzyme-linked immunosorbent assay.

RESULTSThe expression of green fluorescent protein mediated by Starburst PAMAM dendrimers was found in heart, liver, spleen, lung, kidney, brain and injected muscle from 2 hours to 7 days after the vaccination. The highest expression level of the gene was detected in kidney, as well as in endothelial cells. The antibody response evoked by the DNA vaccine carried by the Starburst PAMAM dendrimers was significantly higher than that of the net DNA vaccination. Vaccination with Starburst PAMAM dendrimers elicited higher expression level of the gene in brain and kidney than with the net gene itself.

CONCLUSIONAs a novel non-viral DNA carrier with low self-antigenicity, Starburst PAMAM dendrimers have potential to mediate DNA transfer and expression in vivo.

Animals ; Biocompatible Materials ; pharmacology ; Dendrimers ; Drug Carriers ; pharmacology ; Female ; Green Fluorescent Proteins ; genetics ; pharmacokinetics ; Malaria Vaccines ; immunology ; Mice ; Mice, Inbred BALB C ; Polyamines ; pharmacology ; Vaccination ; Vaccines, DNA ; immunology