Lack of an association between the ASN-108 mutation in the dihydrofolate reductase gene and in vivo resistance to sulfadoxine/pyrimethamine in Plasmodium falciparum.

Sulfadoxine/pyrimethamine (SP) is considered an alternative treatment for acute uncomplicated malaria caused by Plasmodium falciparum resistant to chloroquine. However, the appearance of resistance to this drug has been reported since its initial use in Colombia. Molecular analysis of the dihydrofolate reductase gene indicates a correlation between in vitro resistance to SP and the Asn-108 point mutation. Little is known about the association of this point mutation and in vivo resistance to SP. We used a mutation-specific polymerase chain reaction strategy to analyze the presence of the Asn-108 point mutation in 48 clinical samples with adequate clinical response (ACR), 2 early treatment failures (ETF), and 1 late treatment failure (LTF). The Asn-108 mutation was detected in 36 of the ACR samples and in all of the ETF and LTF samples. Eleven ACR samples amplified with the wild-type-specific primer and one amplified with the primer for the Thr-108 mutation described for resistance to cycloguanil. These results suggest that the Asn-108 marker may not be useful in predicting SP treatment failure.

Positive IgG Western blot for Borrelia burgdorferi in Colombia.

In order to evaluate the presence of specific IgG antibodies to Borrelia burgdorferi in patients with clinical manifestations associated with Lyme borreliosis in Cali, Colombia, 20 serum samples from patients with dermatologic signs, one cerebrospinal fluid (CSF) sample from a patient with chronic neurologic and arthritic manifestations, and twelve serum samples from individuals without clinical signs associated with Lyme borreliosis were analyzed by IgG Western blot. The results were interpreted following the recommendations of the Centers for Diseases Control and Prevention (CDC) for IgG Western blots. Four samples fulfilled the CDC criteria: two serum specimens from patients with morphea (localized scleroderma), the CSF from the patient with neurologic and arthritic manifestations, and one of the controls. Interpretation of positive serology for Lyme disease in non-endemic countries must be cautious. However these results suggest that the putative "Lyme-like" disease may correlate with positivity on Western blots, thus raising the possibility that a spirochete genospecies distinct from B. burgdorferi sensu stricto, or a Borrelia species other than B. burgdorferi sensu lato is the causative agent. Future work will focus on a survey of the local tick and rodent population for evidence of spirochete species that could be incriminated as the etiologic agent.

Characterization of a Plasmodium chabaudi gene encoding a protein with glutamate-rich tandem repeats.

Several highly antigenic proteins containing tandem repeats rich in glutamic acid residues have been described in Plasmodium falciparum. However, relatively little information is available about analogous genes in rodent parasites. This report describes a 4.2-kb genomic DNA fragment from P. chabaudi with a deduced amino acid sequence that is predominantly glutamate-rich tandem repeats. Several different monoclonal antibodies raised against a 93-kDa P. chabaudi protein, which does not correspond to the cloned DNA fragment, recognize a recombinant protein expressed from the 4.2-kb DNA fragment. The only sequence similarities between these two genes are tandem repeats with a predominance of glutamate pairs followed by a hydrophobic residue. This repetitious-sequence motif may be the basis for the observed cross-reactivity. A similar motif has been demonstrated to be the basis for antibody cross-reactivity between glutamate-rich proteins of P. falciparum. The expression of multiple glutamate-rich proteins with cross-reacting epitopes may be a general phenomenon in Plasmodium species.

Assessment of therapeutic response of Plasmodium falciparum to chloroquine and sulfadoxine-pyrimethamine in an area of low malaria transmission in Colombia.

Although chloroquine (CQ) resistance was first reported in Colombia in 1961 and sulfadoxine-pyrimethamine (SP) resistance in 1981, the frequency of treatment failures to these drugs in Colombia is unclear. A modified World Health Organization 14-day in vivo drug efficacy test for uncomplicated Plasmodium falciparum malaria in areas with intense malaria transmission was adapted to reflect the clinical and epidemiologic features of a low-intensity malaria transmission area in the Pacific Coast Region of Colombia. Patients > or =1 year of age with a parasite density > or =1,000 asexual parasites per microliter were enrolled in this study. Forty-four percent (24 of 54) of the CQ-treated patients were therapeutic failures, including 7 early treatment failures (ETFs) and 17 late treatment failures (LTFs). Four (6%) of 67 SP-treated patients were therapeutic failures (2 ETFs and 2 LTFs). Therapeutic failure in the CQ-treated group was associated with an age <15 years old (P < 0.01), but was not associated with initial parasite density, the presence of CQ or sulfa-containing drugs in urine, or a history of malaria. The high level of therapeutic failures to CQ detected in this study underscores the need and importance of drug efficacy evaluation in the development of a rational national antimalarial drug policy. The relatively low level of therapeutic failures to SP compared with other South American countries raises further questions regarding factors that might have prevented the rapid development of in vivo resistance to this drug combination.

Molecular characterization of a Plasmodium chabaudi erythrocyte membrane-associated protein with glutamate-rich tandem repeats.

The malarial parasite dramatically affects the structure and function of the erythrocyte membrane by exporting proteins that specifically interact with the host membrane. This report describes the complete sequence and some biochemical properties of a 93-kDa Plasmodium chabaudi chabaudi protein that interacts with the host erythrocyte membrane. Approximately 40% of the deduced protein sequence consists of tandem repeats of 14 amino acids that are rich in glutamic acid residues. Comparison of the repeat sequences from two different P. c. chabaudi strains derived from the same initial isolate revealed an exact duplication of 294 nucleotides suggesting a recent unequal crossing-over event. However, in spite of this potentially high level of intragenic recombination activity, the repeat sequences from P. c. adami are rather conserved suggesting structural or functional constraints on the protein and tandem repeats. The 93-kDa protein exists in an oligomeric form as revealed by gel filtration chromatography and non-denaturing gel electrophoresis. A predominantly alpha-helical predicted secondary structure and a discrepancy between the estimated molecular sizes determined from non-denaturing gel electrophoresis and gel filtration chromatography suggest that the protein is a long rod-shaped or fibrillar, protein. Attributes shared between the 93-kDa protein, some P. falciparum proteins with glutamate-rich tandem repeats, and cytoskeletal proteins suggest that these parasite proteins function as cytoskeletal proteins that possibly stabilize the erythrocyte membrane.

Frequency of the Asn-108 and Thr-108 point mutations in the dihydrofolate reductase gene in Plasmodium falciparum from southwest Colombia.

Several point mutations in the dihydrofolate reductase (DHFR) gene of Plasmodium falciparum have been correlated with in vitro anti-folate drug resistance of laboratory and field isolates. Furthermore, two different point mutations that generate amino acid substitutions at the same position of the enzyme have been observed in all the isolates studied to date. These point mutations change a serine (Ser-108) in the wild type to an asparagine (Asn-108 mutation) or to a threonine (Thr-108 mutation). Using the polymerase chain reaction (PCR), it is possible to identify isolates that present these mutations. We used a mutation-specific PCR to screen 71 samples from several geographic locations of Colombia for the Asn-108 mutation (pyrimethamine resistance). In this initial screening 53 of 71 yielded amplification product with the DHFR mutation-specific primers. We further analyzed the 18 samples that did not amplify using a mutation-specific nested PCR. Of those 18 samples, seven amplified with primers specific for the Thr-108 mutation (proguanil resistance), one with the wild type (Ser-108), and 10 did not amplify. Of these 10 samples, three were identified as P. falciparum using a species-specific diagnostic nested PCR base on sequences from the small ribosomal RNA subunit gene. Overall, 51.6% of the samples amplified for the Asn-108 mutation, 10.9% for the Thr-108 mutation, 35.9% with the wild type specific primer, and 4.8% did not amplify with any of the DHFR primers. We observed variability in the frequency of the mutation between the different geographic location. The frequency of the Asn-108 and Thr-108 mutations in the state of Narifio was 25% each, while in Valle del Cauca the frequencies were 59% and 11%, respectively. These results contrast with observations in Brazil in which the Asn-108 mutation was found in 90% of the blood samples screened.

Plasmodium chabaudi: immunogenicity of a highly antigenic glutamate-rich protein.

The immunogenicity of a 93-kDa Plasmodium chabaudi protein that contains glutamate-rich tandem repeats was investigated in this study. Immunoblotting with various monoclonal antibodies indicates that this 93-kDa protein is equivalent to a potential P. chabaudi RESA analogue. However, the sequence of the P. chabaudi protein does not exhibit any significant homology to Pf155/RESA. Antibodies against the 93-kDa protein appear early during P. chabaudi infection and reach high titers. The highest antibody titers are found when the parasitemia is descending, suggesting that this protein may play some role in immunity. Immunization of mice with the recombinant protein also results in high antibody titers, indicating that the protein is quite immunogenic. However, mice immunized with recombinant protein and challenged with P. chabaudi do not exhibit a delayed appearance of parasitemia, a reduced parasitemia, or a shortened duration of parasitemia. Glutamate-rich P. falciparum proteins such as Pf155/RESA, are being considered as vaccine candidates. The studies with P. chabaudi suggest that interpretation of serological data using glutamate-rich proteins should proceed with caution. The glutamate-rich repeats, although highly immunogenic, may not be important in host immunity against malaria. However, antibodies that appear late in the P. chabaudi infection do appear to play a role in anti-malarial immunity.

[Continuing education in health in Latin America]. / La educación permanente en salud en América Latina.

The article considers continuing education as instruction to update knowledge and provide personal training. The first part defines concepts, terms, education, learning, socialization, critical awareness, and personal training. The underlying principles of continuing education are spelled out: Education is a continuing process; every social group is educational; continuing education is comprehensive; education is a dynamic process; education is an orderly process of thought; the education system is integrative in character; and education is an innovative process. The second section examines the relationship between work and continuing education, and views work as a social institution that completes the education process. A consideration of continuing education, health services, and the purposes of continuing education completes this part. The third part compares the new continuing education with the traditional variety. The former centers on the student, learning, and work, and the latter on the teacher and verbalization. The fourth part discusses methods, research, and evaluation and the existing kinds of continuing education in relation to their objectives. Continuing education in Latin America is the subject of the fifth part, which summarizes the disparate purposes, methods, and concepts of 155 continuing education program in the region. It is concluded that continuing education is a means, not an end, the end being to meet the public's health needs.