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T M Daly

Publications and source records attributed to T M Daly.

31 records · Page 2Linked to original sources
PubMed1995

Humoral response to a carboxyl-terminal region of the merozoite surface protein-1 plays a predominant role in controlling blood-stage infection in rodent malaria.

The developmental stages of malaria parasites that infect E are responsible for the morbidity and mortality associated with this disease. One of the leading candidates for a blood-stage vaccine against malaria is a surface protein of merozoites, the infectious stages for E, designated merozoite surface protein-1 (MSP-1). The rodent malarial parasite Plasmodium yoelii yoelii (Py) has provided a model system for the study of this Ag, and previous studies from our laboratory had demonstrated that the carboxyl-terminal, cysteine-rich region of MSP-1, when expressed in a native configuration, could immunize mice against a normally lethal challenge infection with Py. We have now prepared a new fusion construct with the glutathione-S-transferase gene of Schistosoma japonicum joined to the carboxyl-terminal 11 kDa of Py MSP-1. This includes only the two epidermal growth factor-like domains of the MSP-1 protein. When expressed in recombinant Escherichia coli, the fusion protein induces a strong protective response in BALB/c mice as judged by the resistance of immunized animals to a virulent challenge infection. Moreover, we demonstrate that this resistance can be transferred passively by immune serum or by purified Ig, establishing a significant role for humoral immunity in protection. No role for CD4+ or CD8+ T cells could be identified in the first 12 days after challenge infection in immune mice selectively depleted of these cells; however, after this time, parasitemias gradually increased in mice depleted of CD4+ T cells, suggesting an active host response is necessary to completely eliminate the infection.

Animals↗
PubMed1994

Immunity to erythrocytic stages of malarial parasites.

In those individuals who live in endemic areas, immunity to malaria is slow to develop and stage-specific. The nature and antigenic specificity of this response, which may involve components of both cell-mediated and humoral immunity, is not well understood. Rodent models provide useful systems to explore the spectrum of host responses that may contribute to resolution of erythrocytic-stage infection or possibly to pathogenesis. Moreover, these models allow identification of plasmodial molecules that can induce different types of host responses. Two different mouse model systems, Plasmodium yoelii yoelii and P. chabaudi adami are presented. These have been selected because resolution of infection by P. yoelii yoelii has been shown to require B cell-dependent mechanisms, while control of acute P. chabaudi adami infection can be achieved by T cell-dependent mechanisms. A monoclonal antibody that provides passive protection to P. yoelii challenge infection has been shown to recognize the cysteine-rich, carboxyl-terminal region of the merozoite surface protein-1. This region, obtained in an appropriate configuration from recombinant Escherichia coli, can induce significant protective immune responses in naive mice. In contrast, cell-mediated immune mechanisms make a major contribution to resolution of asexual-stage P. chabaudi adami infection. An empirical approach using continuous flow electrophoresis has identified several low molecular weight plasmodial proteins that can induce partial protective responses in susceptible hosts. These observations are briefly discussed with respect to human malaria.

Animals↗
PubMed1993

A recombinant 15-kilodalton carboxyl-terminal fragment of Plasmodium yoelii yoelii 17XL merozoite surface protein 1 induces a protective immune response in mice.

Since the developmental stages of malarial parasites which replicate within erythrocytes are responsible for the morbidity and mortality associated with this disease, antigens produced by these stages have been proposed as candidates for a vaccine. One surface protein of merozoites (MSP-1) has been shown to immunize both rodents and primates against virulent challenge infection in experimental systems. However, little is known of relevant epitopes on the molecule, and attempts to obtain recombinant MSP-1 polypeptides in a native configuration have proven difficult. We have found that the cysteine-rich, carboxyl-terminal region of the MSP-1 protein from the rodent malarial parasite Plasmodium yoelii yoelii can be expressed in a native configuration as a fusion protein in Escherichia coli. This recombinant polypeptide containing 15 kDa of the predicted 197-kDa protein elicits antibodies in mice which recognize the native parasite MSP-1. Most significantly, both inbred and outbred mice immunized with the fusion protein in Ribi adjuvant are partially and in some cases completely protected against challenge infection with an otherwise lethal parasite strain. This is the first observation of such significant protection obtained with a small portion of the MSP-1 produced in recombinant systems.

Animals↗
PubMed1989

A protective monoclonal antibody recognizes an epitope in the carboxyl-terminal cysteine-rich domain in the precursor of the major merozoite surface antigen of the rodent malarial parasite, Plasmodium yoelii.

The 195-kDa major merozoite surface antigen of Plasmodium falciparum (Pf PMMSA) is a potential candidate for the development of a blood-stage malarial vaccine. We have focused on an analogous 230-kDa Ag of the rodent malarial parasite, Plasmodium yoelii, in an effort to study this protein in an experimental model system. Previously we reported the cloning and sequencing of a 2.1-kb portion of the gene encoding the carboxyl-terminal 77 kDa of the Py PMMSA. This region contained the B cell epitope recognized by mAb 302, a mAb shown to protect mice passively against P. yoelii challenge infection. To localize this B cell epitope, we have inserted various restriction fragments of the cloned Py PMMSA sequence into the bacterial expression vector pMG27NSTerm. Recombinant peptides of 74, 40, 34, 17, and 10 kDa have been produced which bear the epitope recognized by mAb 302. The results demonstrate that this B cell epitope is located within the most carboxyl-region of the Py PMMSA which contains a series of ten cysteine residues, also found in the PMMSA of P. falciparum. Further analysis showed that the reduction of disulfide bonds as well as the deletion of CYS-607 of the cloned sequence, resulted in the loss of the expression of this epitope. It is of interest that this epitope does not appear to be a dominant B cell determinant of the Py PMMSA molecule during infection. Inasmuch as this cysteine-rich domain of Py PMMSA displays considerable homology with that of Pf PMMSA, our data suggest that this region of the Pf PMMSA should be considered for inclusion in the development of a blood-stage vaccine.

Amino Acid Sequence↗
PubMed1989

A protective monoclonal antibody recognizes a variant-specific epitope in the precursor of the major merozoite surface antigen of the rodent malarial parasite Plasmodium yoelii.

The precursor of the major merozoite surface Ag (PMMSA) represents one of the principal molecules of the erythrocytic stages of malarial parasites. Previously we reported that mAb 302 recognizing the 230-kDa PMMSA of Plasmodium yoelii provided passive protection to mice challenged with this parasite. We now report that the protective capacity of mAb 302 is variant specific, affording protection against infection with only three of five P. yoelii lines. Immunoprecipitation analyses of their PMMSA revealed that the expression of the epitope recognized by mAb 302 also varied and correlated completely with the results of the passive protection studies. Although this specific determinant was not present on the merozoite Ag of all P. yoelii lines, the common expression of other B cell epitopes was noted by the demonstration of serologic cross-reactivity between these molecules. Furthermore, the relatedness of the genes encoding the PMMSA of several murine plasmodial strains and species was clearly shown in nucleic acid hybridization studies. Although strain-common and strain-variable epitopes have been observed in the PMMSA of the human parasite, Plasmodium falciparum, little is known concerning the variability of its biologically relevant epitopes. The current studies using the P. yoelii model system demonstrate that the epitope recognized by a protective mAb is strain variable. Because of the similarities between these antigens of P. falciparum and P. yoelii, this information may impact on the construction of an effective blood-stage malarial vaccine.

Animals↗
PubMed1988

Plasmodium yoelii: characterization of a protective idiotype during malarial infection in mice.

We have previously identified and characterized a monoclonal antibody (McAb 302) with potent passive protective activity in mice infected with Plasmodium yoelii, a murine malarial parasite which depends on antibodies for resolution. To further study the appearance and regulation of this antibody during infection, we prepared syngeneic monoclonal antibodies specific for idiotopes present on McAb 302. Three hybridomas were established which synthesized antibodies that bound only to the homologous idiotype but which did not recognize isotypic specificities. All three of these antibodies were found to recognize distinct 302 idiotopes and two of these were shown to be specific for determinants associated with the antibody combining site of McAb 302. One of these monoclonal anti-idiotypic antibodies was used to develop an enzyme-linked immunosorbent assay for the 302 idiotype. When serum samples taken at different times from mice undergoing a primary infection with P. yoelii were tested in this assay, the 302 idiotype could not be detected even though the host was mounting a significant humoral response to the 230-kDa antigen recognized by McAb 302. These studies suggest that the idiotype of the protective McAb 302 is not a predominant one involved in the resolution of a P. yoelii infection and that only some idiotypes of antibodies directed to relevant plasmodial antigens possess significant biological activity. Therefore, protective immunization with plasmodial antigens may require the elicitation of selected idiotypes. Attempts to alter the course of P. yoelii infection by preimmunization with monoclonal or polyclonal anti-idiotypic reagents were unsuccessful.

Animals↗
PubMed1988

The 3' portion of the gene for a Plasmodium yoelii merozoite surface antigen encodes the epitope recognized by a protective monoclonal antibody.

The 230-kDa merozoite antigen of the murine malarial parasite Plasmodium yoelii provides a potential model system for the development of a protective erythrocytic stage vaccine. To characterize this antigen at the molecular level, isolated P. yoelii 17XL DNA was used to construct a genomic library in the expression vector lambda gt11. A monoclonal antibody, mAb 302, which passively protected mice against P. yoelii challenge infection, was used to identify a lambda gt11 recombinant clone encoding a portion of the 230-kDa antigen of this parasite. Using this clone as a probe, we identified an mRNA of 7.6 kilobases by RNA blot analysis. Nucleic acid sequence analysis of the clone showed that the epitope recognized by the protective mAb 302 is encoded by the 3' portion of the gene for the 230-kDa antigen. The deduced amino acid sequence revealed that this antigen also contains the tandemly repeated tetrapeptide Gly-Ala-Val-Pro, a series of 10 cysteine residues located within the terminal 110 amino acids, and a potential membrane anchor of 18 hydrophobic residues. Comparison of this C-terminal sequence with the carboxyl segment of the 195-kDa merozoite antigen of Plasmodium falciparum revealed nucleic acid and amino acid sequence similarities ranging from 40% to 70%. The localization of a B-cell epitope recognized by the protective mAb 302 to this carboxyl region of the P. yoelii antigen, combined with the limited strain variability in this region of the homologous 195-kDa antigen of P. falciparum, has implications for the development of an effective erythrocytic stage malarial vaccine.

Amino Acid Sequence↗
PubMed1984

Analysis of mRNA coding for blood-stage antigens of a rodent malarial parasite, Plasmodium yoelii: mRNA coding for a possible protective antigen purify as poly A-.

We have analyzed mRNA coding for blood-stage antigens of Plasmodium yoelii by using cellfree translation of poly A+ and poly A- RNA in conjunction with immunoprecipitations. Most of the antigens recognized by mouse hyperimmune serum to P. yoelii were coded by poly A+ mRNA ranging in size from 15S to 28S. However, certain P. yoelii antigens, notably those with m.w. greater than 150 kilodaltons (kd), were coded by mRNA that purified as being poly A-. Antigens recognized by a protective monoclonal antibody (McAb) were coded by such operationally poly A- RNA. Three polypeptides apparently coded by different poly A- RNA were immunoprecipitated by this McAb. With the use of another McAb, a poly A+ mRNA of about 19S was identified as coding for a polypeptide of 46 kd synthesized in cellfree translation reactions. The same McAb recognized a 34 kd polypeptide in metabolically labeled polypeptides of P. yoelii. This antigen appeared to be processed in vivo but not in vitro. The observation that some mRNA of P. yoelii purify as being poly A- has significant implications for the construction of cDNA libraries that employ poly A+ mRNA of malarial parasites: if it applies to other species of plasmodia, some potentially important operationally poly A- mRNA may not be represented in such libraries.

Animals↗
PubMed1984

Passive immunization against murine malaria with an IgG3 monoclonal antibody.

Spleen cells of BALB/c mice that were immune to the 17X strain of P. yoelii were fused with P3X63Ag8 myeloma cells. Two hundred fifty-three of 1053 hybrid cells produced antibodies reactive with disrupted 17X parasites in a solid phase radioimmunoassay. One of these antibodies, McAb 302, reacted with the merozoites of the 17X (nonlethal) and 17XL (lethal) variants of P. yoelii. Of greater significance, McAb 302 passively protected mice against challenge infection with the lethal variant. Mice treated with this antibody before infection developed low-grade parasitemia (less than 0.3%) of short duration when challenged with P. yoelii 17XL . In contrast, control mice that had been untreated or injected with ascites fluid lacking McAb 302 uniformly died with fulminating malaria upon challenge with the same parasite. In other experiments, McAb 302 was shown capable of controlling blood parasite levels when administered to mice with patent P. yoelii 17XL infections. Although all control mice died, mice protected with a single dose of McAb 302 ultimately cleared their infections. Regardless of how passive immunization was performed, mice given McAb 302 were resistant to subsequent challenge with P. yoelii 17XL , indicating they had developed significant immunity during their initial controlled infections. McAb 302 also showed pronounced passive protective activity against the nonlethal 17X strain of P. yoelii, which is a parasite of reticulocytes. The protection afforded by McAb 302 was specific, because mice passively immunized with this antibody died when challenged with the unrelated P. vinckei. McAb 302 was shown to possess the IgG3 isotype and precipitated a 230-kd protein plus several smaller polypeptides from metabolically labeled parasite antigen preparation derived from both variants of P. yoelii. It did not react with similar preparations of other murine plasmodial species.

Animals↗
PubMed1976

Effect of trypsin on mouse mammary tumor virus.

Undisrupted mouse mammary tumor virus (MuMTV) derived from the milk of of RIII mice has been analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and electron microscopy after treatment with insolubilized trypsin. No alterations were found in viral fine structure by either freeze-etch or negative-stain electron microscopy. No alterations were found in the ability of trypsinized virus to compete in a radioimmune assay for viral antigens. Infectivity experiments indicate no significant differences in the ability of treated virus to infect C57Bl mice. However, significant differences were observed in polypeptide composition. The intensely periodic acid-Schiff-positive band, gp140, was shown by galactose oxidase-borotritide labeling to be degraded into a fragment of 125,000 molecular weight. The major glycoprotein, gp55, was split into fragments of 36,000 and 23,000 molecular weight, both of which stained with periodic acid-Schiff stain. Gp68 was removed from the virus. Experiments with purified, iodinated gp55 showed that the trypsin-induced fragments of gp55 were immunologically active. We conclude that: (i) certain glycoproteins at the surface of MuMTV are accessible to an insoluble form of trypsin, (ii) the trypsin causes a nick in the polypeptide chain without affecting the configuration of the molecule; (iii) the nicked molecules remain bound to the virus; and (iv) the presence of these nicked molecules does not interfere with the biological or antigenic expression of virus function.

Animals↗