Multiple high-risk HPV genotypes are grouped by type and are associated with viral load and risk factors.

Investigating whether high-risk human papillomavirus (HR-HPV) types tend to become grouped in a particular way and whether factors are associated with such grouping is important for measuring the real impact of vaccination. In total, 219 women proving positive for HPV as detected by real-time PCR were included in the study. Each sample was analysed for detecting and quantifying six viral types and the hydroxymethylbilane synthase gene. Multiple correspondence analysis led to determining grouping patterns for six HR-HPV types and simultaneous association with multiple variables and whether viral load was related to the coexistence of other viral types. Two grouping profiles were identified: the first included HPV-16 and HPV-45 and the second profile was represented by HPV-31, HPV-33 and HPV-58. Variables such as origin, contraceptive method, births and pregnancies, educational level, healthcare affiliation regime, atypical squamous cells of undetermined significance and viral load were associated with these grouping profiles. Different socio-demographic characteristics were found when coinfection occurred by phylogenetically related HPV types and when coinfection was due to non-related types. Biological characteristics, the number of viral copies, temporality regarding acquiring infection and competition between viral types could influence the configuration of grouping patterns. Characteristics related to women and HPV, influence such interactions between coexisting HPV types reflecting the importance of their evaluation.

Peptides derived from Mycobacterium tuberculosis Rv2301 protein are involved in invasion to human epithelial cells and macrophages.

The specific function of putative cut2 protein (or CFP25), encoded by the Rv2301 gene from Mycobacterium tuberculosis H37Rv, has not been identified yet. The aim of this study was to assess some of CFP25 characteristics and its possible biological role in Mycobacterium tuberculosis H37Rv invasion process to target cells. Molecular assays indicated that the gene encoding Rv2301 is present and transcribed in M. tuberculosis complex strains. The presence of Rv2301 protein over the bacilli surface was confirmed by Western blot and immunoelectron microscopy analyses, using goats sera inoculated with synthetic peptides derived from Rv2301 protein. Receptor-ligand binding assays with carcinomic human alveolar basal epithelial cells (A549) and macrophages derived from human histolytic lymphoma monocytes (U937) allowed us to identify five high activity binding peptides (HABPs) in both cell lines, and two additional HABPs only in A549 cells. U937 HABPs binding interactions were characterized by saturation assays, finding dissociation constants (Kd) within the nanomolar range and positive cooperativity (nH>1). Inhibition assays were performed to assess the possible biological role of Rv2301 identified HABPs, finding that some of them were able to inhibit invasion at a 5 µM concentration, compared with the cytochalasin control. On the other hand, HABPs, and especially HABP 36507 located at the N-terminus of the protein, facilitated the internalization of fluorescent latex beads into A549 cells. These findings are of vital importance for the rational selection of Rv2301 HABPs, to be included as components of an antituberculosis vaccine.

Antibodies in malarial sera to parasite antigens in the membrane of erythrocytes infected with early asexual stages of Plasmodium falciparum.

Monolayers of human erythrocytes (E) infected with Plasmodium falciparum were briefly fixed with 1% glutaraldehyde and air dried. They were then exposed to sera from patients with P. falciparum malaria or from donors immune to this parasite and tested in an indirect immunofluorescence assay (IFA). Parasites in infected E were made visible by counterstaining with ethidium bromide. Immunofluorescence (IF) was restricted to the surface of infected E. No antibody binding was detected unless the E were dried, suggesting that the relevant antigens were not available on the outer layers of the E surface. Staining over large parts of the E surface was seen already when the merozoite penetrated noninfected cells and was strong in E containing early stages of the parasite (rings, trophozoites). It was weak or absent from E containing schizonts. Antibodies in sera from different parts of Africa, Colombia, or Sweden reacted similarly with E infected with a Tanzanian P. falciparum strain kept in culture for many years and with parasitized E freshly drawn from African, Swedish, or Colombian patients. All sera from residents of a holoendemic area (Liberia) were IFA positive. In contrast, some sera from Colombian or Swedish patients with primary infection gave negative results. The results of the IFA and of an enzyme-linked immunosorbent assay in which fixed and dried E were the targets were well-correlated, suggesting that the same antibodies were detected by these assays. The antigens involved in the IFA were susceptible to pronase but not to trypsin or neuraminidase. E surface IF was inhibited by lysates of infected E, merozoite extracts, or soluble antigens present in P. falciparum culture supernatants but not by lysates of normal E or ghost extracts. The inhibitory antigens were heat stable (100 degrees C, 5 min). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis followed by immunoblotting of either antigen-enriched preparations from culture supernatants or merozoite extracts showed that antibodies eluted from monolayers of infected E reacted consistently with a predominant polypeptide of Mr 155,000 and two to four minor polypeptides of lower molecular weights. Metabolic labeling of the parasites with 75Se-methionine indicated that these antigens were parasite derived. We conclude that the antigens involved in these reactions are released from bursting schizonts or merozoites and are deposited in the E membrane in the course of invasion.(ABSTRACT TRUNCATED AT 400 WORDS)

An analysis of in vitro T cell responsiveness in lepromatous leprosy.

In lepromatous leprosy, there is extensive replication of Mycobacterium leprae (M. leprae) within dermal macrophages. This lack of microbial resistance has been attributed to a defective cell-mediated immune response to M. leprae antigens. We have examined the in vitro response of T cells to M. leprae to determine if hyporesponsiveness could be reversed. The study included 40 unselected patients from New York and from Colombia, most with the severe lepromatous form of the disease. We first noted that lepromatous leprosy patients were of two types: those unable to respond, as assessed by T cell proliferation and immune (gamma) interferon (IFN-gamma) release, and a second group, exhibiting low but detectable responses relative to tuberculoid controls. When the effect of exogenous recombinant interleukin-2 (IL-2) on the response to M. leprae antigens was compared in the two groups, many of the low responders, but not the nonresponders, showed enhanced proliferation and IFN-gamma release. To evaluate a possible suppressive effect of monocytes, these cells were eliminated with a cell-specific monoclonal antibody and complement. Depletion of monocytes often expanded preexisting weak responses but did not reverse the anergy of the M. leprae nonresponders. The enhancement was not M. leprae-specific, since it was also observed when bacillus Calmette-Guerin was the antigenic stimulus for proliferation and IFN-gamma production. Removal of the suppressor T cell subset, with OKT8 antibody and complement, also did not restore responses in nonresponder patients. We conclude that a sizable number of lepromatous leprosy patients exhibit a low degree of responsiveness to M. leprae and that the responses can be enhanced in vitro with IL-2 or with monocyte depletion. Nonresponsiveness, however, cannot be reversed. Since currently available assays measure the function of previously sensitized T cells, suppressor mechanisms may yet contribute to defective cell-mediated immunity by impairing the initial sensitization to M. leprae antigens.

Shifting the polarity of some critical residues in malarial peptides' binding to host cells is a key factor in breaking conserved antigens' code of silence.

As microbes use many mechanisms for avoiding immunological pressure, new strategies must be developed to bypass the immunological code of silence of conserved, functionally-important amino acid sequences, such as those involved in high activity binding peptides' (HABPs) attaching to their host cells. Hundreds of experiments in large numbers of Aotus monkeys revealed that this immunological code of silence could be broken by shifting the polarity of some critical host cell binding residues in these HABPs by substituting F for R and vice versa, Y<-->W, L<-->H, I<-->N, P<-->D, M<-->K or E, C<-->T, V<-->N or S; there are special rules for A, G and S. (1)H-nuclear magnetic resonance of these modified, immunogenic, protection-inducing HABPs and molecular modelling revealed that such modifications induced appropriate fitting into specific HLA-DRbeta1 Pockets, suggesting the presence of new pockets and a haplotype- and allele-specific conscious TCR. A highly immunogenic and protection-inducing anti-malarial vaccine can thus be produced.

Immunological and structural characterization of an epitope from the Trypanosoma cruzi KMP-11 protein.

The K1 peptide is an HLA-A*0201-restricted cytotoxic epitope derived from the Trypanosoma cruzi KMP-11 protein, this being the etiological agent of Chagas' disease. This work describes the K1 peptide's secondary structure and its recognition by sera from chagasic patients. Circular dichroism and NMR spectroscopy analysis revealed that the K1 peptide adopts an alpha-helical conformation. Fifty-six percent of individuals had anti-K1 and 86% anti-KMP-11 antibodies by ELISA in the chronic Chagas' group and 28 and 68% in the indeterminate Chagas' group, respectively. By contrast, no reactivity was observed in sera from healthy individuals and tuberculosis patients. Antibody response subclass specificity to the K1 peptide was IgG1 and IgG3. Taken together these results support the idea that the K1 peptide acts as a B-cell-inducer epitope during Chagas' disease.

Synthetic peptides from Plasmodium falciparum apical membrane antigen 1 (AMA-1) specifically interacting with human hepatocytes.

Plasmodium falciparum apical membrane antigen 1 (AMA-1) is expressed during both the sporozoite and merozoite stage of the parasite's life cycle. The role placed by AMA-1 during sporozoite invasion of hepatocytes has not been made sufficiently clear to date. Identifying the sequences involved in binding to hepatocytes is an important step towards understanding the structural basis for sporozoite-hepatocyte interaction. Binding assays between P. falciparum AMA-1 peptides and HepG2 cell were performed in this study to identify possible AMA-1 functional regions. Four AMA-1 high activity binding peptides (HABPs) bound specifically to hepatocytes: 4310 ((74)QHAYPIDHEGAEPAPQEQNL(93)), 4316 ((194)TLDEMRHFYKDNKYVKNLDE(213)), 4321 ((294)VVDNWEKVCPRKNLQNAKFGY(313)) and 4332 ((514)AEVTSNNEVVVKEEYKDEYA(533)). Their binding to these cells became saturable and resistant to treatment with neuraminidase. Most of these peptides were located in AMA-1 domains I and III, these being target regions for protective antibody responses. These peptides interacted with 36 and 58 kDa proteins on the erythrocyte surface. Some of the peptides were found in exposed regions of the AMA-1 protein, thereby facilitating their interaction with host cells. It is thus probable that AMA-1 regions defined by the four peptides mentioned above are involved in sporozoite-hepatocyte interaction.

Based on HLA-DR beta1* allele binding specificities, striking differences in distance and TCR Contacting Residue Orientation can be observed in modified protection-inducing malarial synthetic peptides.

An anti-malarial vaccine is urgently needed, especially against P. falciparum which causes 2 to 3 million deaths each year, mostly in Sub-Saharan African children. This vaccine should contain molecules from the parasite's different developmental stages due to the parasite's remarkable complexity and genetic variability. The first approach using synthetic peptides from different parasite stage molecules (the SPf66 malaria vaccine) conferred limited protective efficacy in Aotus monkeys and in large field-trials carried out in different parts of the world SPf66 contains red blood cell (RBC) binding merozoite peptides for which immune responses against them are genetically controlled by HLA-DR region. Therefore, a systematic search of conserved high activity binding peptides (HABP) was undertaken aimed at using them as immunogens. However, these peptides were poorly immunogenic and had poor protection-inducing capacity against experimental challenge with a P. falciparum strain highly infective for Aotus monkeys an experimental model with an immune system quite similar to humans. Modifications were thus made to key residues to render them immunogenic and protection-inducing. These native and modified HABPs' three-dimensional structure was determined by (1)H-NMR studies and their ability in forming stable Major Histocompatibility Class II - peptide (MHCII-peptide) complexes was correlated with their ability to bind in vitro to purified HLA-DR beta1* molecules. Our experimental data suggests a correlation between modified HABPs' three-dimensional structure, HLA-DR beta1* binding preferences and their protection-inducing capacity in monkeys. Furthermore, the data presented here indicates that a synthetic peptide vaccine's three-dimensional structural features dictate both HLA-DR beta1* allele binding preference (imposing genetic restriction on the immune response) and on these vaccines' protection-inducing value. Basic knowledge of a parasite's functionally active peptides, their 3D structure and their interaction for forming the MHC II- peptide-TCR complex will thus contribute towards designing fully effective multi-component, multi-stage subunit-based malarial vaccines.

Mapping of antigenic determinants of the T. cruzi hsp70 in chagasic and healthy individuals.

In the present paper we describe the analysis of the immunological recognition by sera of healthy individuals and chagasic patients of the Trypanosoma cruzi heat shock 70 kDa protein. By a Falcon Assay Screening Test, using as antigen an ATP-agarose purified T. cruzi hsp70, it has been found that the sera of infected patients as well as of that of healthy individuals show reactivity against the hsp70 protein but that the reactivity of the sera of patients is in general significantly higher than that of healthy individuals. The analysis of the reactivity of the chagasic sera against a collection of peptides covering 92% of the protein has shown that more than 50% of the peptides gave a positive response but only against a few peptides did we observe high reactivity in a wide spectrum of sera. Only four peptides (numbers 9, 12, 14 and 47) were recognized by all sera tested with high reactivity values. The sera of healthy individuals also showed reactivity against a large percentage of peptides but with lower values. It was observed that particular peptides showing high reactivity against the sera of healthy donors also show high reactivity against patients' sera. However, the general pattern of reactivity against the peptides is different in chagasic and healthy sera. The immunodominant peptides map in the highly conserved as well as in the less conserved part of the hsp70 molecule. The 1/3 C-terminal, being the least conserved part of the molecule, seems to be the least immunogenic. Mapping of the epitopes led to the identification of particular immunogenic motifs within individual peptides.

Alpha helix shortening in 1522 MSP-1 conserved peptide analogs is associated with immunogenicity and protection against P. falciparum malaria.

1522 is a nonimmunogenic conserved high-activity binding peptide (HABP) belonging to Plasmodium falciparum MSP-1 protein N-terminal fragment. The key amino acids in binding to red blood cells (RBC) were identified and replaced by others having similar mass but different charge. Because conserved HABPs are not antigenic nor immunogenic, immunogenicity and protectivity studies were then conducted on them in the Aotus monkey. 1H-NMR studies included the lead peptide 1522 as well as the analogs 9782, 13446, 13448, and 13442 to relate their structure to biological function. All the peptides presented alpha-helical structure, with differences observed in helix location and extension. The nonprotective 1522 peptide was totally helical from the N- to the C-terminus, very similar to nonprotective 13442 and 13448 peptides whose extension was almost totally helical. The 9782 and 13446 protective peptides, however, possessed a shorter helical region where modified critical binding residues were not included. A more flexible region was generated at the C-terminus in those peptides with a shorter helical region, leading to a greater number of conformers. These data suggest that peptide flexibility results in increased interaction with immune system molecules, generating protective immunity.

Immunodiagnosis of parasitic diseases with synthetic peptides.

Parasitic diseases remain as a major public health problem worldwide, not only based on their historically high morbidity and mortality rates, but also because risk factors associated with their transmission are increasing. Laboratory diagnosis and particularly immunodiagnosis is a basic tool for the demonstration, clinical management and control of these infections. Classically, the serological tests for the detection of antibodies or antigens are based on the use of crude and purified antigens. Synthetic peptides have opened a new field and perspectives, as the source of pure epitopes and molecules for diagnosis of malaria, Chagas' disease, leishmaniasis, schistosomiasis, hidatidosis, cysticercosis and fasciolosis based on the detection of antibodies and circulating antigens. Herein, are critically reviewed the relevant advances and applications of the synthetic peptides on immunodiagnosis of parasitic diseases. A variety of sequences, constructs (monomers, polymers, MAPs), immunological methods and samples have been used, demonstrating their diagnostic potential. However, in most parasitic infections it is necessary to use more than a single peptide in order to avoid the genetic restriction against certain epitopes, as well as to test them in well characteized groups of patients, in order to confirm their sensitivity and specificity. The concept of multidiagnosis with synthetic peptides, using a novel multi-dot blot assay is introduced. Finally, the chemical imitation of antigens, offers a tremendous posibilities in the diagnosis of parasitic infections in developing countries since this strategy is cheaper, simpler, reproducible, useful for large scale testing and in most cases, specific and sensitive.

Regulation of hsp70 expression in Trypanosoma cruzi by temperature and growth phase.

The steady-state level of the hsp70 mRNAs of Trypanosoma cruzi cultured at different temperatures and growth conditions has been analyzed by Northern blotting. We show that only one size class of hsp70 mRNA, of about 2.2 kb, is transcribed from the hsp70 cluster and that its transcription is constitutive at 28 degrees C. However, after a heat shock treatment at 37 degrees C for 2 h of logarithmically growing parasites, the abundance of the hsp70 mRNA increased about 4-fold. A similar increase was observed at 28 degrees C when the parasite culture reached the stationary phase of growth. On the other hand, a heat shock at 42 degrees C did not change the steady state level of the 2.2-kb size class of hsp70 mRNA. However, accumulation of transcripts of high molecular weight was detected when stationary growing parasites were cultured at 42 degrees C for 2 h. Also at 37 degrees C the steady state level of the alpha- and beta-tubulin mRNAs of logarithmically growing parasites exhibited a slight increase but only after a period of 24 h. Analysis by one-dimensional immunoblots of the Hsp70 levels showed that at 37 degrees C the abundance of the protein was 4-fold higher than at 28 degrees C. Immunoblots of high-resolution two-dimensional gel electrophoresis showed, moreover, that various isoforms of this protein are constitutively expressed at 28 degrees C and that some of them have a specific pattern of induction at 37 degrees C. We observed, moreover, that the heat shock induces the expression of a series of proteins while it causes repression of others.

Identification of the Leishmania infantum P0 ribosomal protein epitope in canine visceral leishmaniasis.

In the present work we show that a high percentage of the sera from dogs naturally affected with viscero-cutaneous leishmaniasis contain antibodies reacting with the Leishmania infantum P0 ribosomal protein. In order to map the antigenic determinants of the LiP0 protein during Leishmania-infection, the complete amino acid sequence of the protein was synthesized as overlapping 20-mer peptides. We have identified the sequence AAKEEPEESDEDDFGMG, located adjacent to the C-terminal end of the protein, as the major antigenic determinant. The anti-LiP0 antibodies present in the sera of the infected dogs do not cross-react with a relatively similar antigenic determinant of the LiP2 acidic proteins as an indication that the Leishmania P0 protein is an independent immunogenically functional antigen in the canine form of the infection.

Mapping of the linear antigenic determinants from the Leishmania infantum histone H2A recognized by sera from dogs with leishmaniasis.

Antibodies reacting against the H2A histone protein were frequently observed in the sera from dogs naturally infected with the protozoan parasite Leishmania infantum. Using synthetic peptides covering the complete sequence of the protein we have identified the amino terminal region, comprising from amino acids 1 to 20, and the carboxyl terminal region, comprising from amino acids 106 to 132, as conforming the antigenic determinants of the protein. Those regions, exposed in the nucleosome surface, are highly divergent in sequence relative to the mammalian H2A histones. The anti-H2A histone antibodies present in the sera of these dogs specifically recognize the L. infantum H2A histone and they do not react with mammalian histones. The present data indicate that, in spite of the evolutionary conservation of the H2A histone protein among eukaryotic organisms, the humoral response against this protein during natural infection is specifically triggered by the parasite protein antigenic determinants.

Mapping of the linear antigenic determinants of the Leishmania infantum hsp70 recognized by leishmaniasis sera.

Mapping of antigenic determinants of the Leishmania infantum Hsp70 was studied by analysis of the reactivity of sera from dogs with natural visceral leishmaniasis against a collection of peptides representing overlapping sequences of the Hsp70. Despite the considerable variation in the immune response among individuals three immunodominant regions were revealed encompassing residues 241 to 260 (region I), 435 to 469 (region II) and from amino acid 601 to the carboxyl-terminal end of the protein (region II. Since anti-peptide H17 antibodies purified from a pool of leishmaniasis sera recognized the L. infantum Hsp70 and since they did not react with the homologous Hsp70s from other trypanosomatids, such as Trypanosoma cruzi, Trypanosoma rangeli and Leishmania panamensis, it was concluded that peptide H17 (region II contains an immunodominant B cell species-specific epitope. Our data indicate, however, that the complete recombinant L infantum Hsp70 protein cannot be used as a disease-specific tool for serodiagnosis since it is also recognized by the sera from patients with Chagas' disease.

Studies in owl monkeys leading to the development of a synthetic vaccine against the asexual blood stages of Plasmodium falciparum.

During the development of a synthetic vaccine for human use against the asexual blood stages of Plasmodium falciparum, monkey trials were performed to assess safety, immunogenicity, and protectivity. We determined the minimal infective dose of the P. falciparum FVO strain, the kinetics of the immune response induced by vaccination with the synthetic peptide mixture (S7 + S12 + S17) or the synthetic hybrid polymeric protein SPf66, and the induction of protective immunity against the experimental challenge with 2 P. falciparum strains. A clear boosting effect was observed, determined by the increased antibody titers against synthetic peptides S7, S12, S17, and SPf66, and by improvement in the protective immune response against the challenge. These studies suggest that either the peptide mixture or the synthetic hybrid polymeric protein are excellent choices for the development of a vaccine against P. falciparum.

Immunization of owl monkeys with a combination of Plasmodium falciparum asexual blood-stage synthetic peptide antigens.

A mixture of 3 synthetic peptides (35.1, 55.1, and 83.1) corresponding to portions of the 35 kDa, 55 kDa, and 83 kDa proteins from the asexual blood stages of Plasmodium falciparum and a polymer of a syntheic peptide incorporating the 3 individual peptides (SPf66) were tested as candidate malaria vaccine antigens in Aotus nancymai. Monkeys were immunized with combinations of the 3 peptides from 2 separate sources (Centers for Disease Control [CDC], Atlanta, GA or Colombia) or with the synthetic polymer. Animals immunized with a combination of the 3 peptides from CDC had higher antibody titers to the 35.1 and 55.1 peptides than to the 83.1 peptide. Monkeys immunized with a combination of the 3 peptides produced in Colombia developed higher levels of antibody to the 55.1 than to the 83.1 and 35.1 peptides. Animals immunized with the polymer produced detectable antibodies to the 55.1 peptide alone. Following challenge with P. falciparum, no differences were observed between the 3 vaccine groups and 2 control groups with respect to the number of animals with parasitemias greater than or equal to 10%. The inconsistency of serologic response to all 3 peptides in these animals contrasted with previous trials performed in Colombia where the monkeys developed high antibody titers against the 3 peptides and were protected against the experimental infection.

Cultivation and characterization of stable Leishmania guyanensis complex axenic amastigotes derived from infected U937 cells.

The study of the differential regulation of several genes, in both Leishmania parasite life cycle forms, has been simplified by the development of in vitro axenic amastigote culture. Different reports have described extracellular amastigote production and maintenance from several Leishmania spp. A general approach to induce amastigote-like transformation includes progressive pH and temperature changes. Production of axenic amastigotes in continuous cultures using amastigotes recovered from macrophages is described in this report. Leishmania (Viannia) panamensis (M/HOM/PA/71/LS94) and Leishmania (V). guyanensis (M/HOM/BR/75/M4147) intracellular amastigotes were recovered from the human macrophage-like U937 cell line previously infected with promastigotes. The parasites were immediately adapted for growth and kept as axenic amastigotes at 34 degrees C and acidic pH. These organisms were able to infect macrophage cell lines, maintain amastigote morphologic features, and express stage-specific transcripts. The relevance of axenic amastigotes in characterizing virulence factors in American leishmaniasis is discussed.

Geographical distribution of Plasmodium falciparum erythrocyte rosetting and frequency of rosetting antibodies in human sera.

Uninfected erythrocytes bind spontaneously to those infected with certain strains of Plasmodium falciparum. This is known as spontaneous erythrocyte rosetting. We have studied the occurrence and frequency of rosetting in 75 fresh patient isolates and have identified rosetting strains from Africa, South America, and Asia. Rosetting was present in 49% of the isolates tested; the frequency of rosetting red blood cells (RBC) in individual isolates was 0-75% when scored during the first cycle of in vitro growth. Rosetting antibodies were found in 15 out of 73 (21%) Liberian sera as measured by disruption of rosettes in vitro. However, antibodies able to inhibit CD36 dependent cytoadherence of P. falciparum-infected RBC were not detected in these sera. Erythrocyte rosetting is a geographically widespread phenomenon. Rosetting antibodies seem to be induced by natural infection and the molecular mechanism of rosette formation seems distinct from that of endothelial cytoadherence.

Agglutination of Plasmodium falciparum-infected erythrocytes from east and west African isolates by human sera from distant geographic regions.

Plasmodium falciparum-infected erythrocytes (PfE) were collected from acutely infected children in The Gambia and Tanzania and cultured for more than 30 hr until the parasites were mature trophozoites. Sera collected from these countries, other African countries, Asia, and South America were used in the PfE microagglutination test to determine whether PfE from East and West Africa share surface antigens. From the patterns of agglutination reactivity, we identified extensive antigenic diversity in surface antigens, but obtained no evidence for greater differences between isolates from East or West Africa and those within one region. The majority of sera from immune adults from The Gambia, Tanzania, Sudan, Nigeria, or Ghana were pan-agglutinating, and agglutinated all PfE isolates from The Gambia and Tanzania. Some sera from immune adults of Irian Jaya also agglutinated each of the seven African isolates, while others agglutinated many but not all of the isolates, similar to sera from immune adults of Flores, Indonesia. In contrast, sera from nonimmune adults from Colombia agglutinated few of the African isolates. It was remarkable, however, that sera from nonimmune Colombians agglutinated any African isolates. Our results are consistent with the following conclusions: some PfE surface antigen(s) are very diverse; this diversity is a feature of the parasite worldwide; the repertoire of isolate-specific surface antigens, although large, includes antigens that are either identical or antigenically cross-reactive in geographically very distant parasite populations; and African adults have pan-agglutinating antibodies that may contribute to protective immunity. Such pan-agglutinating antibodies could reflect the accumulation of a large repertoire of isolate-specific antibodies. The contribution of antibody against any shared PfE surface antigen to the pan-agglutinating reactivities is unknown and awaits development of the appropriate reagents.