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Malaria caused by Plasmodium falciparum remains the leading single-agent cause of mortality in children 1 , yet the promise of an effective vaccine has not been fulfilled. Here, using our previously described differential screening method to analyse the proteome of blood-stage P. falciparum parasites 2 , we identify P. falciparum glutamic-acid-rich protein (PfGARP) as a parasite antigen that is recognized by antibodies in the plasma of children who are relatively resistant-but not those who are susceptible-to malaria caused by P. falciparum. PfGARP is a parasite antigen of 80 kDa that is expressed on the exofacial surface of erythrocytes infected by early-to-late-trophozoite-stage parasites. We demonstrate that antibodies against PfGARP kill trophozoite-infected erythrocytes in culture by inducing programmed cell death in the parasites, and that vaccinating non-human primates with PfGARP partially protects against a challenge with P. falciparum. Furthermore, our longitudinal cohort studies showed that, compared to individuals who had naturally occurring anti-PfGARP antibodies, Tanzanian children without anti-PfGARP antibodies had a 2.5-fold-higher risk of severe malaria and Kenyan adolescents and adults without these antibodies had a twofold-higher parasite density. By killing trophozoite-infected erythrocytes, PfGARP could synergize with other vaccines that target parasite invasion of hepatocytes or the invasion of and egress from erythrocytes.

Transmission of malaria parasites from humans to Anopheles mosquitoes can be inhibited by specific antibodies elicited during malaria infection, which target surface Plasmodium gametocyte/gamete proteins. Some of these proteins may have potential for vaccine development. Pvs48/45 is a P. vivax gametocyte surface antigen orthologous to Pfs48/45, which may play a role during parasite fertilization and thus has potential for transmission blocking (TB) activity. Here we describe the expression of a recombinant Pvs48/45 protein expressed in Escherichia coli as a ∼60kDa construct which we tested for antigenicity using human sera and for its immunogenicity and transmission blocking activity of specific anti-mouse and anti-monkey Pvs48/45 antibodies. The protein reacted with sera of individuals from malaria-endemic areas and in addition induced specific IgG antibody responses in BALB/c mice and Aotus l. griseimembra monkeys. Sera from both immunized animal species recognized native P. vivax protein in Western blot (WB) and immunofluorescence assays. Moreover, sera from immunized mice and monkeys produced significant inhibition of parasite transmission to An. Albimanus mosquitoes as shown by membrane feeding assays. Results indicate the presence of reactive epitopes in the Pvs48/45 recombinant product that induce antibodies with TB activity. Further testing of this protein is ongoing to determine its vaccine potential.

We have previously reported that Vivax Malaria Protein 001 (VMP001), a vaccine candidate based on the circumsporozoite protein of Plasmodium vivax, is immunogenic in mice and rhesus monkeys in the presence of various adjuvants. In the present study, we evaluated the immunogenicity and efficacy of VMP001 formulated with a TLR9 agonist in a water-in-oil emulsion. Following immunization, the vaccine efficacy was assessed by challenging Aotus nancymaae monkeys with P. vivax sporozoites. Monkeys from both the low- and high-dose vaccine groups generated strong humoral immune responses to the vaccine (peak median titers of 291,622), and its subunits (peak median titers to the N-term, central repeat and C-term regions of 22,188; 66,120 and 179,947, respectively). 66.7% of vaccinated monkeys demonstrated sterile protection following challenge. Protection was associated with antibodies directed against the central repeat region. The protected monkeys had a median anti-repeat titer of 97,841 compared to 14,822 in the non-protected monkeys. This is the first report demonstrating P. vivax CSP vaccine-induced protection of Aotus monkeys challenged with P. vivax sporozoites.

American Cutaneous Leishmaniasis (ACL) is caused by protozoan parasites of the Leishmania genus, and transmitted by females of the Phlebotominae family. The role of wild and domestic hosts in the cycle of Leishmania is still unknown. ACL is endemic in the province of Formosa where Nyssomyia neivai was the most abundant species in several captures and 31 cumulative ACL human cases were reported between 2005 and 2011 in the province. The present report describes the detection, by PCR-RFLP and confirmed by sequencing, of subgenus Leishmania (Viannia) DNA in four free-ranging owl monkeys (Aotus azarai azarai) from Formosa Province. The sequence amplified was the mini-exon gene present in tandem repeats in all species of the Leishmania genus from buffy coat samples. The absence of inhibitors in the samples was checked by a β-globin protocol originally designed to amplify the human β-globin gene. However, other free-ranging primates were found with natural infections of L. (V) braziliensis complex and Leishmania (Viannia) subgenus by parasitological means in America. To the best of our knowledge, there are no published reports on detection of subgenus Leishmania (Viannia) DNA by PCR-RFLP in argentinean free-ranging primates. Additional eco-epidemiological and parasitological studies are necessary to confirm owl monkeys, or any other natural infected mammal species detected by PCR, as a reservoir, incidental host or to propose it as an animal model for research on this topic., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Oocyst counts were compared between mosquitoes that fed on humans versus mosquitoes that fed on Aotus monkeys, both of which were infected with the Chesson strain of Plasmodium vivax. Oocyst counts obtained from mosquitoes fed on humans were almost 10-fold higher in number. Mosquitoes were more likely to be infected and with a higher rate of infection when they fed on monkeys before the peak in the asexual parasite count. Mosquitoes that fed on humans were more likely to be more heavily infected when fed after the peak in the asexual count. Of several species of owl monkeys, Aotus vociferans was infected at a higher frequency. On the basis of oocyst counts, Anopheles dirus were the most susceptible and An. maculatus were the least susceptible of the mosquito species tested.

Splenectomized Aotus lemurinus griseimembra, A. azarae boliviensis, A. nancymaae, A. vociferans, and Saimiri boliviensis monkeys were infected with the Uganda I/CDC strain of Plasmodium malariae. The maximum parasite counts were lower if the animals had been previously infected with Plasmodium vivax. Mosquito infection was concentrated in the 12 days following the rise in count above 1,000/microl. Mosquito infection and parasite counts were highest with A. l. griseimembra. Anopheles freeborni was more readily infected than An. gambiae, which was more readily infected than An. stephensi. Parasite counts and mosquito infection with P. brasilianum were much higher in S. boliviensis monkeys than with the Uganda I strain of P. malariae in this host, suggesting marked differences between the host-parasite-vector relationships and indicating that P. brasilianum in S. boliviensis monkeys may be a better reflection of the relationship of P. malariae in the human host.

Plasmodium vivax is the second leading cause of malaria worldwide. Invasion of human erythrocytes by P. vivax merozoites is dependent upon the interaction between the parasite Duffy binding protein (PvDBP) and the erythrocyte Duffy antigen receptor. Therefore, disruption of this vital interaction is an attractive target for therapeutic intervention. Although Aotus nancymaae is a commonly used primate model for human P. vivax infections, it has not been confirmed that the interaction between Ao. nancymaae erythrocytes and P. vivax is Duffy antigen dependent. Our results indicate that normal Ao. nancymaae erythrocytes readily bind to PvDBPII and that this binding is completely abolished with chymotrypsin treatment of the erythrocytes. Furthermore, the results of our inhibition assays show a dose-dependent decrease in binding with increasing amounts of anti-PvDBPII polyclonal rabbit sera or anti-Fy6 monoclonal antibody. These data indicate that the interaction between Ao. nancymaae erythrocytes and P. vivax DBPII is Duffy antigen dependent, validating this model system for in vivo studies of anti-PvDBP inhibition.

The objective of the present study was to report the occurrence of Trypanoxyuris in owl monkeys, using data from clinical and haematological examinations, as well as clinical chemistry (blood urea nitrogen (BUN), creatinine, alanine aminotransferase (ALT) and aspartate aminotransferase (AST)) of infected and uninfected animals. Twenty animals in apparently good clinical health were studied. The coproparasitological examinations showed eggs compatible with Trypanoxyuris sp. in 50% of animals. The number of red blood cells, haematocrit and haemoglobin levels were significantly higher in the males, compared to the females, irrespective of parasitism. However, comparing segmented neutrophils in infected males and females, a significant difference (P < 0.05) was observed. All blood chemistry values were considered normal for the species pattern, even though significant differences were observed for BUN and ALT in infected males. The infection by Trypanoxyuris sp. did not appear to interfere with the clinical condition of animals.

Of 1,004 positive lots of mosquitoes fed on 229 humans infected with Plasmodium falciparum, 46.2% had 1-10 oocysts/(+)gut, 21.2% had 10-30 oocysts/(+)gut, 22.2% had 30-100 oocysts/(+)gut, and 10.4% had > 100 oocysts/(+) gut. The highest levels of infection occurred between 6 and 15 days after the peak in the asexual parasite count. Of 2,281 lots of Anopheles freeborni mosquitoes fed on splenectomized Aotus monkeys infected with the Santa Lucia strain of P. falciparum, 1,191 were infected (52.2%). The highest intensity infections ranged from 2.78 oocysts per positive gut in mosquitoes fed on Aotus vociferans to 6.08 oocysts per positive gut for those fed on A. lemurinus griseimembra to 10.4 oocysts per positive gut for those fed on A. nancymaae. The pattern of infection for mosquitoes fed on splenectomized Aotus monkeys was similar to that obtained by feeding on humans, but the intensity, based on oocyst/(+)gut, was much lower.

Forty-four splenectomized Aotus nancymaae monkeys were infected with 6 different strains of Plasmodium cynomolgi, 11 via trophozoites and 33 via sporozoites. Sporozoites from Anopheles dirus, Anopheles freeborni, Anopheles gambiae, Anopheles maculatus, and Anopheles stephensi resulted in prepatent periods ranging from 9 to 39 days (median of 15 days). Importantly, relapse was demonstrated in 5 of 5 sporozoite-induced infections with the Rossan strain following treatment with chloroquine.

The Santa Lucia strain of Plasmodium falciparum was studied in 150 Aotus lemurinus griseimembra, 30 A. azarae boliviensis, 103 A. nancymaae, and 121 A. vociferans monkeys. All four of these splenectomized hosts supported the production of gametocytes infective to Anopheles freeborni mosquitoes. Transmission through sporozoites from An. freeborni, An. stephensi, An. maculatus, and An. albimanus mosquitoes was successful to all four species of Aotus on a total of 100 occasions with a median pre-patent period of 21 days. For the production of infective mosquitoes for vaccine challenge studies, A. l. griseimembra and A. vociferans were the most predictable hosts.

In this study, we provide phylogenetic and biogeographic evidence that the Trypanosoma cruzi lineages T. cruzi I (TCI) and T. cruzi IIa (TCIIa) circulate amongst non-human primates in Brazilian Amazonia, and are transmitted by Rhodnius species in overlapping arboreal transmission cycles, sporadically infecting humans. TCI presented higher prevalence rates, and no lineages other than TCI and TCIIa were found in this study in wild monkeys and Rhodnius from the Amazonian region. We characterised TCI and TCIIa from wild primates (16 TCI and five TCIIa), Rhodnius spp. (13 TCI and nine TCIIa), and humans with Chagas disease associated with oral transmission (14 TCI and five TCIIa) in Brazilian Amazonia. To our knowledge, TCIIa had not been associated with wild monkeys until now. Polymorphisms of ssrDNA, cytochrome b gene sequences and randomly amplified polymorphic DNA (RAPD) patterns clearly separated TCIIa from TCIIb-e and TCI lineages, and disclosed small intra-lineage polymorphisms amongst isolates from Amazonia. These data are important in understanding the complexity of the transmission cycles, genetic structure, and evolutionary history of T. cruzi populations circulating in Amazonia, and they contribute to both the unravelling of human infection routes and the pathological peculiarities of Chagas disease in this region.

A review is presented on studies conducted in New World monkeys and chimpanzees with the Salvador I strain of Plasmodium vivax. This isolate has been adapted to Aotus and Saimiri (squirrel) monkeys and developed as a model for the testing of antimalarial vaccines. After the injection of 10,000 sporozoites, the median prepatent period in S. boliviensis monkeys was 21.5 days. In 103 sporozoite-induced infections in splenectomized monkeys, the median maximum parasite count ranged from 2,139 to 202,368/microL, with a median maximum parasite count of 48,174/microL. Median maximum parasite counts in Aotus lemurinus griseimembra, A. nancymaae, A. azarae boliviensis, and A. vociferans monkeys were 19,902, 18,390, 21,420, and 18,210/microL, respectively and ranged from 124 to 156,000/microL. Mosquito infections were readily obtained in different species of Anopheles mosquitoes. The S. boliviensis monkey and Salvador I strain seems suitable for the testing of sporozoite and liver stage vaccines but not for blood-stage vaccines against P. vivax unless adapted further in spleen-intact Saimiri boliviensis monkeys.

Plasmodium inui shortti was studied in monkeys (66 Macaca mulatta, 2 M. fascicularis, 12 Saimiri boliviensis, 4 Aotus lemurinus griseimembra, and 1 A. nancymaae). Prepatent periods for 30 sporozoite transmissions by Anopheles stephensi, An. dirus, and An. maculatus mosquitoes ranged from 10 to 48 days with a median of 15.5 days. In rhesus monkeys, mean maximum parasite counts for intact animals were 181,970/muL; for splenectomized animals, the mean maximum parasite count was 1,167,890/muL.

Comparison was made between the parasitemia of Chesson strain Plasmodium vivax in humans and in splenectomized Aotus lemurinus griseimembra, A. nancymaae, A. vociferans, and A. azarae boliviensis monkeys. In the monkeys, 56.3% of the animals had maximum counts > 25,000/muL and in humans 59.6% were above this peak parasitemia. In humans, it took an average of 9.3 days to reach the maximum parasite count. In monkeys with no previous infections, it took an average of 18.9 days to reach the maximum parasite count; for those with previous infections, it took an average of 15 days. Human and nonhuman primate data on this parasite suggest that splenectomized Aotus monkeys, particularly A. lemurinus griseimembra, and to a somewhat lesser extent A. vociferans, can mimic the course of Chesson malaria in humans regarding parasitemia and mosquito infection.

Some human malaria Plasmodium falciparum parasites, but not others, also cause disease in Aotus monkeys. To identify the basis for this variation, we crossed two clones that differ in Aotus nancymaae virulence and mapped inherited traits of infectivity to erythrocyte invasion by linkage analysis. A major pathway of invasion was linked to polymorphisms in a putative erythrocyte binding protein, PfRH5, found in the apical region of merozoites. Polymorphisms of PfRH5 from the A. nancymaae-virulent parent transformed the nonvirulent parent to a virulent parasite. Conversely, replacements that removed these polymorphisms from PfRH5 converted a virulent progeny clone to a nonvirulent parasite. Further, a proteolytic fragment of PfRH5 from the infective parasites bound to A. nancymaae erythrocytes. Our results also suggest that PfRH5 is a parasite ligand for human infection, and that amino acid substitutions can cause its binding domain to recognize different human erythrocyte surface receptors.

Trypanoxyuris microon is a pinworm that infects New World nonhuman primates, including Aotus nancymae. Although it typically is clinically insignificant, infection may serve as a significant variable during experimental data analysis. In this study we sought to determine the most effective anthelmintic therapy for eradication of T. microon infection in A. nancymae. Animals confirmed to be infected with T. microon by perianal tape test were treated twice (on days 0 and 14) with pyrantel pamoate, ivermectin, or thiabendazole and evaluated for eggs by daily perianal tape test throughout the entire 28-d period. Successful clearance of eggs was defined as 5 consecutive negative perianal tape tests. Pyrantel pamoate and ivermectin were significantly more effective at egg clearance than were thiabendazole and no treatment. Overall, 100% of the pyrantel pamoate and ivermectin treatment groups were cleared of infection after 2 treatments, whereas only 60% of the thiabendazole group became negative for pinworm eggs. In addition, the time after treatment until clearance was 1 to 2 d for pyrantel pamoate, 2 to 4 d for thiabendazole, and 4 to 6.5 d for ivermectin. These results indicate that pyrantel pamoate was the most effective and rapidly acting anthelmintic for the treatment of adult T. microon infection, with ivermectin as a suitable alternative. However because of the potential for continued development of immature stages or reinfection, anthelmintic doses should be repeated after 1 to 2 wk, in combination with effective environmental sanitation.

Plasmodium fragile continues to be investigated because of its biologic similarities to the human malaria parasite, Plasmodium falciparum. Two strains of P. fragile are available for study; one strain is able to infect mosquitoes, whereas the other strain is transmissible only by blood inoculation. The Sri Lanka strain of P. fragile was transmitted to Macaca mulatta, Macaca fascicularis, Aotus lemurinus griseimembra, Aotus nancymaae, Aotus vociferans, and Saimiri boliviensis monkeys via sporozoites that developed to maturity only in Anopheles dirus mosquitoes. The prepatent periods ranged from 12 to 35 days for macaques and from 15 to 30 days for New World monkeys after intravenous injection of sporozoites. Eight rhesus monkeys were infected with the Nilgiri strain and followed for 482 days. Parasitemia in 6 animals persisted at relatively high density through the period of observation. Erythrocyte, hematocrit, and hemoglobin values reached their lowest levels 3 wk after infection and slowly recovered; however, the values did not approach preinfection levels as long as parasitemia persisted in the monkeys. The mean corpuscular volume and corpuscular hemoglobin concentration reached their peak and lowest values, respectively, at day 38 and then returned to the preinfection level. The mean corpuscular hemoglobin value decreased to its lowest level at day 87 and then returned to preinfection level.

Parastrongylus (=Angiostrongylus) costaricensis was first reported in the United States from cotton rats, Sigmodon hispidus, in Texas in 1979. Here, we report the findings of P. costaricensis in a siamang (Hylobates syndactylus) from the Miami MetroZoo, in 2 Ma's night monkeys (Aotus nancymaae) from the DuMond Conservancy located at Monkey Jungle in Miami, in 4 raccoons (Procyon lotor) trapped near the MetroZoo, and in an opossum (Didelphis virginiana) trapped at the MetroZoo. These records are the first records of P. costaricensis from all 4 species of hosts. All of the primates were zoo-born, and the raccoons and opossum were native, indicating that this parasite is now endemic at these 2 sites.

Sporozoites of 3 isolates of Plasmodium cynomolgi dissected from the salivary glands of Anopheles dirus and Anopheles quadrimaculatus were injected intravenously into 9 New World monkeys. Liver stage parasites were demonstrated in all 9 animals; 7 of these animals also produced blood stages after prepatent periods of 9 to 23 days.

The purpose of this study was reactivation and adaptation of a strain of Plasmodium vivax to Aotus nancymai monkeys. A need arose for malarial parasites for use in serologic and molecular studies and for teaching slides. This particular strain of parasite had been characterized previously as producing high-density parasitemia in splenectomized New World monkeys and therefore represented a good candidate for reactivation. P. vivax (Vietnam II), isolated in 1970, was reactivated after adaptation in Aotus lemurinus griseimembra monkeys nearly 33 years earlier and adapted to A. nancymai monkeys. Passage was achieved by intravenous inoculation of parasite blood stages into splenectomized A. nancymai monkeys. Parasitemia was determined by analyzing daily blood smears stained with Giemsa. Maximum parasite counts ranged from 10,630 to 94,000 parasites/microl; the mean maximum parasite count for the four animals was 39,565 parasites/microl. Parasite counts of > 10,000/microl were maintained for 2 to 64 days. After only three passages of the parasite, attempts to reactive were successful. A. nancymai proved a suitable animal model for the recovery of this parasite. In conclusion, successful reactivation and adaptation of this parasite offers the capability to perform a series of diagnostic, immunologic, and molecular studies as well as to provide otherwise potentially unavailable teaching materials to healthcare professionals.

Thirty-three splenectomized Aotus lemurinus griseimembra monkeys with no previous experience with malaria were infected with the Vietnam Palo Alto strain of Plasmodium vivax. The median maximum parasite count was 280,000/microl. Nine splenectomized monkeys with previous infection with Plasmodium falciparum had median maximum parasite counts of 120,000/microl. Splenectomized Aotus nancymai monkeys supported infections at a lower level. Transmission via the bites of Anopheles dirus mosquitoes was obtained in a splenectomized A. lemurinus griseimembra, with a prepatent period of 31 days. It is estimated that between 1.5 x 10(8) and 1.6 x 10(9) parasites can be removed from an infected animal for molecular or diagnostic antigenic studies.

A colony of Anopheles farauti, originally from the island of New Britain in Papua New Guinea, was tested for its receptivity to infection with different species of Plasmodium in comparison with An. freeborni and An. stephensi. This colony adapted well to feeding on monkeys and was infected with New World and Old World strains of P. vivax and P. falciparum, P. ovale, P. cynomolgi, and P. brasilianum.

An archived strain of Plasmodium vivax, isolated from Rio Meta, northern Colombia, in 1972 was adapted to grow in splenectomized Aotus lemurinus griseimembra and A. nancymai monkeys. Anopheles freeborni, An. maculatus, An. dirus, An. culicifacies, and An. albimanus were shown to be susceptible to infection by feeding on infected monkeys. Infections were more readily obtained by feeding on A. L. griseimembra than on A. nancymai. Transmission through sporozoites was obtained in an A. l. griseimembra monkey after a prepatent period of 24 days.

A strain of Plasmodium falciparum from Ghana was adapted to Aotus lemurinus griseimembra, A. nancymai, and A. vociferans monkeys. Gametocytes in splenectomized A. nancymai were infective to Anopheles freeborni mosquitoes. Sporozoite transmission was accomplished in two splenectomized A. nancymai with prepatent periods of 22 and 25 days. The Ghana III/CDC strain of P. falciparum is susceptible to treatment with chloroquine and mefloquine.

Severe anemia is the earliest and a frequently fatal complication of Plasmodium falciparum infection. Here we describe Aotus infulatus as a primate model suitable to study this malaria complication. Both non-splenectomized and splenectomized monkeys receiving different inocula of P. falciparum FVO strain presented large (> 50%) decreases in hematocrit values during infection. Non-splenectomized animals were able to control parasite growth (parasitemia did not exceed 4%), but they had to be treated because of severe anemia. Three of 4 splenectomized monkeys did not control parasitemia and were treated, but developed severe anemia after treatment when presenting a negative blood film. Destruction of parasitized red blood cells alone cannot account for the degree of anemia. Non-splenectomized monkeys repeatedly infected with homologous parasites became rapidly and progressively resistant to reinfection and to the development of severe anemia. The data presented here point to A. infulatus as a suitable model for studying the pathogenesis of severe malarial infection.

Aotus monkeys were infected with a strain of Plasmodium vivax from Panama to determine its potential for the testing of malarial vaccines. After sporozoite inoculation, 3 splenectomized Aotus nancymai that had been infected previously with Plasmodium falciparum and P. vivax had prepatent periods of 13, 15, and 15 days with maximum parasite counts of 12,726/microl, 5,310/microl, and 9,180/microl. Three other A. nancymai previously infected with P. falciparum only had prepatent periods of 17, 15, and 15 days with maximum parasite counts of 44,460/microl, 31,500/microl, and 42,660/microl. One monkey with no previous history of infection had a prepatent period of 14 days after sporozoite inoculation, and a maximum parasite count of 100,000/microl; detectable parasitemia persisted for almost 500 days with 13 recognizable peaks in the parasite count. Anopheles dirus, Anopheles freeborni, Anopheles stephensi, and Anopheles quadrimaculatus mosquitoes were readily infected with the Panama strain.

A strain of Plasmodium vivax from India was adapted to develop in splenectomized Saimiri boliviensis, Aotus lemurinus griseimembra, A vociferans, A. nancymai, A. azarae boliviensis, hybrid Aotus monkeys, and splenectomized chimpanzees. Infections were induced via the inoculation of sporozoites dissected from the salivary glands of Anopheles stephensi and An. dirus mosquitoes to 12 Aotus and 8 Saimiri monkeys; transmission via the bites of infected An. stephensi was made to 1 Aotus monkey and 1 chimpanzee. The intravenous passage of infected erythrocytes was made to 9 Aotus monkeys and 4 chimpanzees. Gametocytes in 13 Aotus monkeys and 4 chimpanzees were infectious to mosquitoes. Infection rates were markedly higher in mosquitoes fed on chimpanzees. PCR studies on 10 monkeys injected with sporozoites revealed the presence of parasites before their detection by microscopic examination. The India VII strain of P. vivax develops in Aotus and Saimiri monkeys and chimpanzees following the injection of parasitized erythrocytes, or sporozoites, or both. The transmission rate via sporozoites to New World monkeys of approximately 50% may be too low for the testing of sporozoite vaccines or drugs directed against the exoerythrocytic stages. However, the strain is highly infectious to commonly available laboratory-maintained anopheline mosquitoes. Mosquito infection is especially high when feedings are made with gametocytes from splenectomized chimpanzees.

The immunogenicity and protective efficacy of four versions of recombinant C-terminal 19-kDa epidermal growth factor-like region of the major surface protein 1 (rMSP1(19)) of Plasmodium falciparum was studied in Aotus monkeys. Vaccination with each of the four rMSP1(19) constructs elicited high levels of antibodies to MSP1(19) but only one construct, the 19-kDa fragment expressed as a secreted fusion protein from Saccharomyces cerevisiae (yP30P2MSP1(19)), induced a high degree of protective immunity in Aotus nancymai against lethal P. falciparum challenge. Protective formulation required Freund's adjuvant; vaccination with yP30P2MSP1(19) in six other adjuvants that are suitable for human use induced lower levels of antibody response and no protection. These results emphasize the need to continue the search for an adjuvant that is comparable to Freund's adjuvant in potency and is safe for use in humans.

Detailed parasitologic, serologic, clinical and histopathologic studies were conducted in owl monkeys (Aotus nancymai) exposed to varying numbers of cercariae of Schistosoma mansoni. All the experimental animals had clinical symptoms suggestive of infection (weight loss diarrhoea, mucus in stools, etc.) which were not seen in uninfected individuals. The only A. vociferans included in this study passed S. mansoni eggs 8 weeks after infection. None of the A. nancymai passed eggs in their faeces. No adult worms were recovered following perfusion of the sacrificed experimental monkeys, suggesting that they were early eliminated. Serological techniques (ELISA-SEA and COPT) allowed diagnosis of infection, starting 9 weeks post challenge, in all but one A. nancymai exposed to 100 cercariae. Granulomas containing eggs were observed predominantly in liver and less extensively in intestine, suggesting that adult worms were mainly lodged in the intrahepatic portal system. We conclude that A. nancymai is susceptible to infection with S. mansoi, with the worms reaching sexual maturity, but being eliminated shortly after oviposition.

Infections with the Salvador II strain of Plasmodium vivax in Aotus lemurinus griseimambra monkeys were fed upon by Anopheles freeborni mosquitoes. Periods of mosquito infectivity were determined to establish a model system for the testing of transmission-blocking vaccines. The highest levels of mosquito infection were associated with the ascending asexual parasitemia after reaching 1,000/microl, and before the peak asexual parasite count. Sporozoite-induced infections were more infectious than were trophozoite-induced infections. Secondary episodes of parasitemia were also infectious, indicating the lack of development of naturally developing transmission-blocking immunity to this strain of P. vivax in splenectomized Aotus monkeys following single infections.

A strain of Plasmodium vivax from Mauritania was adapted to develop in Aotus lemurinus griseimembra, Aotus nancymai, Saimiri boliviensis, and hybrid Aotus monkeys. Infections were induced via the inoculation of sporozoites dissected from the salivary glands of Anopheles gambiae, Anopheles freeborni, and Anopheles stephensi mosquitoes or the intravenous passage of infected erythrocytes. Infections in 3 A. lemurinus griseimembra monkeys readily infected mosquitoes. Four lines of the Mauritania parasites have been stored frozen for further reference.

Aotus lemurinus griseimembra monkeys inoculated with parasitized erythrocytes of the N-3 strain of Plasmodiumfieldi had transient low-density parasitemia. Exoerythrocytic stages of this strain of parasite were demonstrated in sections of liver from Aotus vociferans monkeys taken 8 days after the intravenous inoculation of sporozoites dissected from the salivary glands of Anopheles dirus mosquitoes; no blood-stage infections were observed.

A strain of Plasmodium falciparum from a Montagnard refugee was shown to produce large numbers of gametocytes in culture. Attempts were made to establish this strain in Aotus monkeys via trophozoite and sporozoite inoculation. The Montagnard S-1 strain was readily adapted to A. l. griseimembra monkeys via trophozoite inoculation. Other species of Aotus failed to support the development of high density parasitemia. None of 12 attempts to transmit the infection via sporozoites from Anopheles freeborni or An. dirus mosquitoes was successful; however, developing exoerythrocytic stages were demonstrated in hepatocytes of an A. lemurinus griseimembra monkey.

A nonimmune American acquired an infection of Plasmodium vivax Type 1 malaria in Brazil in 1994. After returning to the U.S.A., he had a primary attack followed by 3 relapses. The primary attack and first 2 relapses were treated with a standard regimen of chloroquine, followed by 14 days of primaquine (15 mg/day). Following the third relapse, the primaquine treatment was extended to 28 days. No further relapses occurred. The lack of response to primaquine by this strain may recommend it as a suitable candidate for chemotherapeutic study if it can be adapted to an animal model. Anopheles quadrimaculatus mosquitoes infected by feeding on the patient during the first relapse were used to establish the strain in Aotus and Saimiri monkeys. Monkeys supported well the development of long-lasting parasitemia. Anopheles freeborni, Anopheles stephensi, and Anopheles gambiae mosquitoes were readily infected by feeding on the monkeys and by membrane feeding on diluted blood. Monkey-to-monkey transmission was obtained via the bites of infected mosquitoes and the intravenous injection of sporozoites dissected from salivary glands. This parasite is designated as the Brazil I/CDC strain of P. vivax.

One of the major constraints for studies on the sporogonic cycle of the parasites causing human malaria, and on the protective efficacy of pre-erythrocytic vaccines, is the scarcity of laboratory-reared Anopheles mosquitoes as a source of infective sporozoites. The aim of the present study was to reproduce the life-cycles of Plasmodium falciparum and P. vivax in the laboratory and so develop the ability to produce infective sporozoites of these two species regularly under laboratory conditions. Colonized Anopheles albimanus, of Buenaventura and Tecojate strains, were infected by feeding either on Plasmodium-infected blood, from human patients or experimentally inoculated Aotus monkeys, or on gametocytes of the P. falciparum NF-54 isolate grown in vitro. The monkeys were infected with the blood stages of a Colombian P. vivax isolate and then, after recovery, with the Santa Lucia strain of P. falciparum from El Salvador. Although both of the mosquito strains used were successfully infected with both parasite species, the Buenaventura strain of mosquito was generally more susceptible to infection than the Tecojate strain, and particularly to infection with the parasites from the patients, who lived where this strain of mosquitoes was originally isolated. Monkeys injected intravenously with the P. vivax sporozoites produced in the mosquitoes developed patent sexual and asexual parasitaemias; the gametocytes that developed could then be used to infect mosquitoes, allowing the development of more sporozoites. However, experimental infections failed to establish after the P. falciparum sporozoites were used to inoculate monkeys. The ability to reproduce the complete life cycle of P. vivax in the laboratory, from human to mosquito and then to monkey, should greatly facilitate many studies on vivax malaria and on the efficacy of candidate malaria vaccines. The availability of the sporogonic cycles of P. falciparum from three different sources should also permit a variety of biological studies.

A Plasmodium falciparum glycophorin binding protein (GBP-130) has been implicated in protective immunity to malaria. The gene for GBP-130 encodes a protein containing 11 tandemly repetitive 50 amino acid units. We report an immunization trial in Aotus monkeys using a recombinant DNA protein containing three of these 50 amino acid repeats. When administered with aluminum hydroxide, this antigen induced low levels of antibodies that reacted with the recombinant protein by ELISA and with parasite antigens in immunoblot and immunofluorescence assays, but not by immunoprecipitation. When administered with Freund's complete adjuvant, this antigen induced high levels of antibodies that reacted in ELISA, immunoblot, immunofluorescence, and immunoprecipitation assays. Serum from immunized monkeys did not inhibit parasite growth, and protection from intravenous challenge with P. falciparum-infected erythrocytes was not observed in any experimental group. These results suggest that the repetitive region of GBP-130 is not a useful vaccine candidate.