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W E Collins

Publications and source records attributed to W E Collins.

At least 19 recordsLinked to original sources
PubMed1992

Inhibitory activity against sporozoites induced by antibodies directed against nonrepetitive regions of the circumsporozoite protein of Plasmodium vivax.

In previous studies, Saimiri sciureus boliviensis monkeys have been immunized with four recombinant proteins reproducing part of the circumsporozoite (CS) protein of Plasmodium vivax sporozoites (NS1(81) V20, rPvCS-1, rPvCS-2, rPv-CS-3), or with irradiated sporozoites of P. vivax Salvador I strain. To analyze the antibody response elicited against epitopes located outside the immunodominant repeat region of the CS protein, serum samples from these animals were tested for their ability to inhibit the in vitro development of liver stages of P. vivax VK247 strain, characterized from the other strains only by a specific repeat region on the CS protein. Results indicated that there is at least one protective B-cell epitope outside the repeat region of the CS protein of P. vivax sporozoites, and that this epitope can be expressed by irradiated sporozoites, rPvCS-1 and -3, but not by rPvCS-1 or NS1(81)V20. Therefore, we designed peptides from the amino acid sequences present both in rPvCS-2 and -3, but not included in the recombinant proteins rPvCS-1 and NS1(81)V20. Anti-peptide antibodies had no activity on the development of sporozoites of P. vivax Salvador I strain, into schizonts in primary culture of Saimiri monkey hepatocytes. In addition, antisporozoite antibodies did not react with any of the peptides. These results suggest that the in vitro inhibition observed in this study could depend upon the conformation of the CS protein. This study also demonstrates that antibody response to unnatural linear epitopes can be induced by immunization with recombinant proteins.

Amino Acid Sequence↗
PubMed1992

A monoclonal antibody directed against the sporozoite stage of Plasmodium vivax binds to liver parenchymal cells.

The circumsporozoite (CS) protein of malaria parasites is a major surface protein of the sporozoite stage. In the process of investigating the immunogenicity of this protein in the Plasmodium vivax complex, we found that a monoclonal antibody (mAb) directed against the CS protein of isolates of P. vivax recognizes New World monkey hepatocytes and human hepatoma cells HepG2A16 in Western blot and by immunoelectron microscopy. The mAb NVS3 binds to the amino acid sequence AGDR, which is also shared with the alpha 3 domain of the human and primate major histocompatibility complex class I. In addition, in vitro experiments suggest that the binding of the mAb NVS3 to hepatocytes from Saimiri monkey enhances the invasion or development of malaria sporozoites. These results form the basis for investigating the relationships between parasite surface proteins and host-cell receptors.

Amino Acid Sequence↗
PubMed1992

Structure and expression of the gene for Pv200, a major blood-stage surface antigen of Plasmodium vivax.

Molecular cloning and structure analysis of the gene encoding the Pv200 protein of the Sal-1 strain of Plasmodium vivax revealed an overall identity of 34-37% when the deduced amino acid sequence was compared with the sequences of various major merozoite surface antigens of Plasmodium falciparum, Plasmodium yoelii and Plasmodium chabaudi. When the Sal-1 Pv200 sequence was compared with the corresponding sequence from the Belèm strain of P. vivax, it was found that the two merozoite surface antigens were relatively well conserved with an overall amino acid sequence identity of 81%. A region of 23 repeated glutamine residues, found in the sequence of the Belèm isolate was not found, however, in the Sal-1 sequence. Amino- and carboxy-terminal domains of the Pv200 protein were expressed in the yeast Saccharomyces cerevisiae. Each recombinant protein was shown to react with antibodies in sera from splenectomized Bolivian Saimiri monkeys that had been infected previously with P. vivax, and in human sera from individuals with a history of exposure to vivax malaria. The availability of recombinant DNA-derived Pv200 proteins will now allow a full assessment of their utility in the diagnosis and immunoprophylaxis of the benign tertian malaria associated with P. vivax infection.

Amino Acid Sequence↗
PubMed1992

Effect of adjuvant formulations on the selection of B-cell epitopes expressed by a malaria peptide vaccine.

Because subunit vaccines may create artificial epitopes, the goal of this study was to concentrate the immune response toward protective epitopes contained in a peptide, [(NAGG)5]Y. This peptide consisted of five repeat sequences of the immunodominant epitope of the circumsporozoite protein of the simian malaria parasite Plasmodium cynomolgi and a terminal tyrosine. It was conjugated to bovine serum albumin and mixed with various adjuvant formulations, including block copolymers L121, L141, L180.5 and a lipopolysaccharide (LPS). Outbred mice were vaccinated with seven vaccine formulations. Postvaccination sera from each group of mice were then pooled, and antibody responses against peptide [(NAGG)5]Y or (NAGG)5 were tested in an enzyme-linked immunosorbent assay and against sporozoites of P. cynomolgi in an indirect fluorescent antibody assay. Although all groups elicited a high antibody response to the peptide [(NAGG)5Y], the presence of the tyrosine induced a different antibody response to the peptide (NAGG)5, and formulations containing LPS alone did not induce an antibody response to either (NAGG)5 or P. cynomolgi sporozoites. The formulation including both LPS and the copolymer L121 was the only one to inhibit the development of P. cynomolgi sporozoites in rhesus monkey hepatocytes by 50%. These results suggest that vaccine formulations influence B-cell epitope selection.

Animals↗
PubMed1992

Impaired renal function in owl monkeys (Aotus nancymai) infected with Plasmodium falciparum.

Impaired renal function was observed in sixteen Aotus nancymai 25 and 3 months following infection with the Uganda Palo Alto strain of Plasmodium falciparum. Decrease were noted in the clearance of endogenous creatinine, creatinine excretion, and urine volume while increases were observed in serum urea nitrogen, urine protein, urine potassium, fractional excretion of phosphorus and potassium, and activities of urinary enzymes. The results were suggestive of glomerulonephropathy and chronic renal disease.

Animals↗
PubMed1992

Plasmodium coatneyi-infected rhesus monkeys: a primate model for human cerebral malaria.

Although several animal models for human cerebral malaria have been proposed in the past, none have shown pathological findings that are similar to those seen in humans. In order to develop an animal model for human cerebral malaria, we studied the pathology of brains of Plasmodium coatneyi (primate malaria parasite)-infected rhesus monkeys. Our study demonstrated parasitized erythrocyte (PRBC) sequestration and cytoadherence of knobs on PRBC to endothelial cells in cerebral microvessels of these monkeys. This is similar to the findings seen in human cerebral malaria. Cerebral microvessels with sequestered PRBC were shown by immunohistochemistry to possess CD36, TSP and ICAM-1. These proteins were not evident in cerebral microvessels of uninfected control monkeys. Our study indicates, for the first time, that rhesus monkeys infected with P. coatneyi can be used as a primate model to study human cerebral malaria.

Animals↗
PubMed1992

Reinforcement of immunity in Saimiri monkeys following immunization with irradiated sporozoites of Plasmodium vivax.

To determine the duration of immunity to Plasmodium vivax following immunization, six Saimiri sciureus boliviensis monkeys were vaccinated with irradiated sporozoites of P. vivax and challenged multiple times with sporozoites. Over a period of almost four years, complete protection from repeated challenge with infective sporozoites was demonstrated in one monkey; protection in two monkeys was obtained on eight of nine occasions, in one monkey on seven of nine occasions, in one monkey on six or nine occasions, and in one monkey on four of eight occasions. Five of six monkeys were protected against infection during the last six challenges. Inoculation with blood-stage parasites at the end of the trial indicated that all animals were susceptible to infection. These results suggest that protection against sporozoite challenge may be strongly reinforced by subsequent exposure to viable sporozoites.

Animals↗
PubMed1992

A primate model for human cerebral malaria: Plasmodium coatneyi-infected rhesus monkeys.

A major factor in the pathogenesis of human cerebral malaria is blockage of cerebral microvessels by the sequestration of parasitized human red blood cells (PRBC). In vitro studies indicate that sequestration of PRBC in the microvessels is mediated by the attachment of knobs on PRBC to receptors on the endothelial cell surface such as CD36, thrombospondin (TSP), and intercellular adhesion molecule-1 (ICAM-1). However, it is difficult to test this theory in vivo because fresh human brain tissues from cerebral malarial autopsy cases are not easy to obtain. Although several animal models for human cerebral malaria have been proposed, none have shown pathologic findings that are similar to those seen in humans. In order to develop an animal model for human cerebral malaria, we studied brains of rhesus monkeys infected with the primate malaria parasite, Plasmodium coatneyi. Our study demonstrated PRBC sequestration and cytoadherence of knobs on PRBC to endothelial cells in the cerebral microvessels of these monkeys. Cerebral microvessels with sequestered PRBC were shown by immunohistochemical analysis to possess CD36, TSP, and ICAM-1. These proteins were not evident in the cerebral microvessels of uninfected control monkeys. Thus, our study indicates, for the first time, that rhesus monkeys infected with P. coatneyi can be used as a primate model to study human cerebral malaria. By using this animal model, we may be able to evaluate strategies for the development of vaccines to prevent human cerebral malaria.

Animals↗
PubMed1992

Renal pathology in owl monkeys vaccinated with Plasmodium falciparum asexual blood-stage synthetic peptide antigens.

Renal specimens from Aotus monkeys were studied by light microscopy and immunohistochemistry to examine pathologic changes following vaccination with synthetic peptides corresponding to the 35-kD, 55-kD, and 83-kD asexual blood stage antigens of Plasmodium falciparum. The monkeys were vaccinated and later challenged with P. falciparum. In the monkeys vaccinated with Centers for Disease Control peptides (group I), specimens from four of six postvaccinated animals had mild to severe mesangial proliferation and two had diffuse interstitial nephritis. Specimens from three monkeys vaccinated with Colombia peptides (group II) had mild to severe mesangial proliferation and one had interstitial nephritis. In the hybrid polymer-vaccinated monkeys (group III), specimens from three animals had mild to moderate mesangial proliferation and one had severe interstitial nephritis. On the other hand, the control group immunized with bovine serum albumin (group IV) showed that specimens from three animals had mild to severe mesangial proliferation and two had severe interstitial nephritis. In the nonimmunized group (group V), specimens from three animals had moderate to severe mesangial proliferation and two had severe and mild interstitial nephritis. Immunohistochemical analysis using the peroxidase-antiperoxidase method revealed mesangial deposits of P. falciparum antigens in 11 of 14 vaccinated monkeys and in five of 10 unvaccinated controls. These results show that treatment of monkeys with prospective malaria vaccines does not increase the frequency of occurrence or of the severity of renal lesions. These data thus provide a baseline for assessing the safety of synthetic malarial vaccines in the future.

Animals↗
PubMed1992

The susceptibility of the Indonesian I/CDC strain of Plasmodium vivax to chloroquine.

A strain of Plasmodium vivax from Indonesia was adapted to splenectomized Aotus and Saimiri monkeys and tested for its susceptibility to chloroquine. Animals were infected by intravenous inoculation of heparinized parasitized blood and subsequently treated with 8 or 15 mg (base) of chloroquine by oral intubation. Recrudescence of infection occurred in 4 of 4 Aotus and 5 of 6 Saimiri monkeys treated with 15 mg base of chloroquine, indicating a level of resistance between that of the standard Chesson strain of P. vivax and the recently reported resistant strains from Papua New Guinea.

Animals↗
PubMed1992

Development of a polymorphic strain of Plasmodium vivax in monkeys.

A strain of Plasmodium vivax from Thailand with a polymorphic repeat unit of the circumsporozoite protein was established in Saimiri sciureus boliviensis and 3 species of Aotus monkeys. All 11 attempts to transmit infection via sporozoite inoculation, 4 times to splenectomized S. sciureus boliviensis, 2 times to splenectomized Aotus nancymai, and 5 times to intact Saimiri monkeys, were successful. Anopheles freeborni, Anopheles stephensi, Anopheles dirus, and Anopheles gambiae mosquitoes were infected by feeding on parasitemic blood from a chimpanzee and an Aotus azarae boliviensis monkey. Our results indicate that this strain may be useful in antisporozoite vaccine trials.

Amino Acid Sequence↗
PubMed1992

Susceptibility of Macaca fascicularis monkeys from Mauritius to different species of Plasmodium.

Macaca fascicularis monkeys from Mauritius were shown to be susceptible via sporozoite inoculation to 7 species of Plasmodium (P. fragile, P. coatneyi, P. gonderi, P. inui, P. cynomolgi, P. knowlesi, and P. fieldi), indigenous to macaques in southeastern Asia. Four monkeys were sequentially infected with different species of Plasmodium to determine maximum and course of parasitemia. In 2 nonsplenectomized monkeys, P. fragile developed maximum parasite counts of only 134 and 155/microliters. For Plasmodium knowlesi, a parasite that is life-threatening to rhesus monkeys, maximum parasite counts were 4,278 and 7,440/microliters. Plasmodium coatneyi developed to what must be considered as moderate levels. After animals underwent splenectomy, parasite counts of P. coatneyi were 58,280, 89,094, 4,464, and 43,524/microliters. The maximum parasite counts for P. gonderi (13,508 and 21,576/microliters) and P. fieldi (1,767 and 17,836/microliters) were lower than would be expected in M. mulatta. In 2 monkeys that developed patent parasitemia with P. inui, the maximum parasite counts (95,046 and 728,748/microliters) indicated that this parasite may be the best adapted species for development in these animals once infection is established. Finally, the reinfection of 2 monkeys with P. cynomolgi suggested that some animals may be basically more resistant than others, whether splenectomized or not, to the production of high-density parasitemia.

Animals↗
PubMed1991

Inability of malaria vaccine to induce antibodies to a protective epitope within its sequence.

Saimiri monkeys immunized with a recombinant protein containing 20 copies of the nine amino acid repeat of the Plasmodium vivax circumsporozoite (CS) protein developed high concentrations of antibodies to the repeat sequence and to sporozoites, but were not protected against challenge. After intravenous injection of an immunoglobulin G3 monoclonal antibody (NVS3) against irradiated P. vivax sporozoites, four of six monkeys were protected against sporozoite-induced malaria, and the remaining two animals took significantly longer to become parasitemic. Epitope mapping demonstrated that NVS3 recognizes only four (AGDR) of the nine amino acids within the repeat region of the P. vivax CS protein. The monkeys immunized with (DRAADGQPAG)20 did not produce antibodies to the protective epitope AGDR. Thus, determination of the fine specificity of protective immune responses may be critical to the construction of successful subunit vaccines.

Amino Acid Sequence↗
PubMed1991

Induction of antigen-specific CD8+ cytolytic T cells by the exogenous bacterial antigen streptolysin O in rhesus monkeys.

We have characterized the T cell responses induced by streptolysin O (SLO), a sulfhydryl-activated hemolysin secreted by streptococci, by applying long-term in vitro culture and cloning rhesus monkey (Macaca mulatta) T cells. T cell lines specific for SLO were obtained from three rhesus monkeys. These T cell lines required autologous antigen-presenting cells (APC) to proliferate in response to SLO and did not respond to purified protein derivative. Phenotypic analysis showed that the cells from two of three SLO-specific T cell lines were more than 85% CD3+CD4-CD8+ after prolonged in vitro culture. The rh 1842 CD8+ T cell line proliferative response to SLO was inhibited by the addition of anti-major histocompatibility complex (MHC) class I and anti-CD8 but not of anti-MHC class II and anti-CD4 monoclonal antibody (mAb). This cell line was able to lyse P815 target cells in the presence of anti-CD3 mAb and did not show natural killer activity. Moreover, specific lysis of autologous but not allogeneic non-rosetting E- cell targets pulsed with SLO was observed. Such lysis was inhibited by the addition of anti-MHC class I mAb. In the attempt to identify the restriction elements involved in SLO presentation APC from six unrelated rhesus monkeys and three humans were used. A CD4+ rh 1842 T cell clone responded when SLO was presented by one of six, and a CD8+ rh 1842 T cell clone by four of six rhesus monkeys APC. Both CD4+ and CD8+ T cell clones did not respond when SLO was presented by human APC. However, both clones responded when APC from all donors were used in conjunction with anti-CD3 mb. Furthermore, SLO required active processing to be presented to CD4+ and CD8+ T cell clones as glutaraldehyde fixation of APC before but not after antigen pulsing inhibited T cell proliferation. The SLO-specific CD8+ cytolytic T cells described here could play a role in the regulation of the immune response occurring during streptococcal infections and/or could participate in the pathogenesis of poststreptococcal nonsuppurative sequelae.

Animals↗
PubMed1991

Plasmodium cynomolgi: immunization of a rhesus monkey with exoerythrocytic stages cultured in autologous hepatocytes.

To investigate the immune response to exoerythrocytic stages of malaria parasites, a rhesus monkey was immunized with autologous primary hepatocyte cultures infected with 7-day-old liver stage parasites of Plasmodium cynomolgi. A primary antibody response against EE stage antigens was obtained, and boosted after injection of homologous viable sporozoites. Antibodies directed against sporozoites and blood stages were also detected. The polyvalent immune response observed demonstrates the antigenicity of the liver stages and suggests their involvement in the general immune response against malaria.

Animals↗
PubMed1991

Evaluation of monoclonal antibodies against Plasmodium vivax sporozoites for ELISA development.

Nine monoclonal antibodies (MAbs) developed against Plasmodium vivax (Grassi & Feletti) salivary gland sporozoites were evaluated for use in an enzyme-linked immunosorbent assay (ELISA), using sporozoites developed in Anopheles dirus Peyton & Harrison An. gambiae Giles and An.maculatus Theobald. Four of the antibodies were unsuitable due to the low sensitivity of the resulting assays or the requirement for high concentrations of capture antibody. An additional two MAbs were rejected because they resulted in assays with high background absorbance, attributed to self-binding. Of the three remaining MAbs, the use of Navy vivax sporozoite (NVS) 3 resulted in an ELISA with the highest sensitivity and the lowest concentration requirement for capture antibody. Assay sensitivity varied with sporozoite strain indicating possible quantitative epitope heterogeneity. None of the MAbs cross-reacted with the heterologous sporozoites tested by immunofluorescence antibody assay (IFA). The IFA activity was not an indicator of ELISA sensitivity. The use of MAb NVS 3 in a standardized ELISA method resulted in an assay 10 times more sensitive than reported previously for P. vivax sporozoites, with a detection limit of fewer than 100 sporozoites per mosquito.

Animals↗
PubMed1991

Epstein-Barr virus transformation of Saimiri sciureus (squirrel monkey) B cells and generation of a Plasmodium brasilianum-specific monoclonal antibody in P. brasilianum-infected monkeys.

The new-world monkeys Saimiri sciureus (squirrel monkeys) are currently used as a model to test the efficacy of vaccines against human malaria. To improve our knowledge on this model, we tested the susceptibility of S. sciureus B cells to Epstein-Barr virus (EBV) infection. B-lymphoblastoid cell lines were obtained from six of six healthy animals after infection with the B95-8 source of EBV. The frequency distributions of spleen B cells clonally committed to the production of immunoglobulins M and G, as measured by limiting dilution analysis, were from 1 in 179 to 1 in 1,085 and from 1 in 45 to 1 in 60, respectively, in three monkeys naturally infected with Plasmodium brasilianum. In the same three animals, the frequency of spleen B cells committed to the production of P. brasilianum-specific antibody ranged from 1 in 2,211 to 1 in 9,099. One B-lymphoblastoid cell line producing anti-P. brasilianum-specific antibody was cloned twice, and the immunoglobulin G produced was purified. This monoclonal antibody recognized a parasite component of 197 kDa and was specific for Plasmodium malariae and P. brasilianum parasites. These data document that squirrel monkey B cells naturally primed by an infectious agent can be efficiently used to produce monospecific antibodies against the infectious agent.

Animals↗