PubMed Health⌕ Search

Biomedical subjects

D C Kaslow

Publications and source records attributed to D C Kaslow.

At least 55 records · Page 3Linked to original sources
PubMed1997

Complete protective immunity induced in mice by immunization with the 19-kilodalton carboxyl-terminal fragment of the merozoite surface protein-1 (MSP1[19]) of Plasmodium yoelii expressed in Saccharomyces cerevisiae: correlation of protection with antigen-specific antibody titer, but not with effector CD4+ T cells.

The 19-kDa carboxyl-terminal fragment of the merozoite surface protein-1 (MSP1) is a leading malaria vaccine candidate but is unable to induce immunity in all monkeys or all strains of mice. The mechanism of immunity is unclear, although data show that cell-mediated immunity plays a critical role following immunization with the larger mature MSP1 protein. We optimized a vaccine protocol using the MSP1(19) fragment of Plasmodium yoelii expressed in Saccharomyces cerevisiae, such that following exposure of mice to parasites, they remained undetectable in peripheral blood, whereas control animals all died at very high parasitemia within 10 days. We then depleted the vaccinated mice of >99% of CD4+ T cells by anti-CD4 mAb treatment and could show that infections in most animals remained subpatent following challenge. Furthermore, mice in which the gene for the mu-chain of Ig had been disrupted could not be immunized with MSP1(19). Immunity in normal mice did not depend on the presence of an intact spleen nor production of nitric oxide, persisting unabated when >70% of splenic macrophages were depleted. Thus, while effector CD4+ T cells may contribute to immunity, neither they nor factors associated with a Th1-type cell mediated immune response appeared to play the major role in MSP1(19)-induced protection in normal mice. Furthermore, T cells were not sufficient for immunity in mice lacking B cells. In normal mice, protection correlated with a very high titer of MSP1(19)-specific Abs (>6,400,000), predominantly G1 and G2b, which may function by merozoite neutralization.

Animals↗
PubMed1997

Transmission-blocking vaccines: uses and current status of development.

Malaria continues to cause incomprehensible human suffering throughout most of the tropics and subtropics: in sub-Saharan Africa it is estimated that 2 million children die each year as a direct cause of infection with Plasmodium. Vector control and malaria chemotherapy that were previously effective in controlling and treating malaria are now largely ineffective due to insecticide-resistant mosquitoes and drug-resistant parasites. As alternatives to these mainstays of control, an intensive effort to develop subunit vaccines targeted at various stages of the life has been undertaken. One such vaccine, directed against the sexual and sporogonic stages and referred to as a transmission-blocking vaccine, offers the hope of controlling malaria in geographically isolated areas, preventing re-introduction of the parasite in malaria-free zones, blocking the spread of drug-resistant or vaccine escape mutants, and reducing exposure to "virulent" strains of parasites. A series of potential transmission-blocking vaccine candidates have identified and the genes encoding these surface proteins have now been isolated and sequenced. One such vaccine candidate, Pfs25, is now being tested in human Phase I safety and immunogenicity studies. Here the use and status of transmission-blocking vaccines are reviewed.

Animals↗
PubMed1997

Cloning and cross-species comparison of the thrombospondin-related anonymous protein (TRAP) gene from Plasmodium knowlesi, Plasmodium vivax and Plasmodium gallinaceum.

To examine the structure of the Plasmodium sporozoite micronemal protein, thrombospondin-related anonymous protein (TRAP) we have isolated TRAP genes from three species of Plasmodium: P. gallinaceum (PgTRAP), P. knowlesi (PkTRAP) and P. vivax (PvTRAP). Thus it is now possible to compare the TRAP gene from a total of six species of Plasmodium. The overall structure of TRAP is conserved in all species; specifically, an amino-terminal A-domain similar to magnesium-binding domains of mammalian integrins; a thrombospondin-like sulfatide-binding domain similar to region II in Plasmodium circumsporozoite protein; an acidic asparagine/proline-rich repeat region; a trans-membrane domain and a short acidic cytoplasmic region with a highly conserved carboxy terminus. The overall structure of TRAP from P. gallinaceum and P. falciparum (PfTRAP) is conserved and phylogenetic analysis suggests a monophyletic relationship of avian P. gallinaceum and human P. falciparum. Comparison of the amino acid sequences of the A-domain of PgTRAP and PfTRAP indicates a more rapid divergence of this domain with respect to the rest of the protein in these two species. The structural differences of PgTRAP and PfTRAP may relate to the distinct invasion pathways, macrophage and endothelial cell invasion of P. gallinaceum sporozoites versus hepatocyte invasion of P. falciparum.

Amino Acid Sequence↗
PubMed1997

A novel malaria protein, Pfs28, and Pfs25 are genetically linked and synergistic as falciparum malaria transmission-blocking vaccines.

Antibodies to Pfs28 block Plasmodium falciparum transmission and when combined with antibodies to Pfs25 provide synergy in blocking transmission. Pfs28 and Pfs25 are immunogenic, have limited antigenic diversity, and are structurally similar and genetically linked on chromosome 10. Pfs28 may prove a useful addition to Pfs25 in an effective transmission-blocking vaccine.

Amino Acid Sequence↗
PubMed1997

Expression and serologic activity of a soluble recombinant Plasmodium vivax Duffy binding protein.

Plasmodium vivax Duffy binding protein (DBP) is a conserved functionally important protein. P. vivax DBP is an asexual blood-stage malaria vaccine candidate because adhesion of P. vivax DBP to its erythrocyte receptor is essential for the parasite to continue development in human blood. We developed a soluble recombinant protein of P. vivax DBP (rDBP) and examined serologic activity to it in residents of a region of high endemicity. This soluble rDBP product contained the cysteine-rich ligand domain and most of the contiguous proline-rich hydrophilic region. rDBP was expressed as a glutathione S-transferase (GST) fusion protein and was isolated from GST by thrombin treatment of the purified fusion protein bound on glutathione agarose beads. P. vivax rDBP was immunogenic in rabbits and induced antibodies that reacted with P. vivax and Plasmodium knowlesi merozoites. Human sera from adult residents of a region of Papua New Guinea where malaria is highly endemic or P. vivax-infected North American residents reacted with rDBP in an immunoblot and an enzyme-linked immunosorbent assay. The reactivity to reduced, denatured P. vivax rDBP and the cross-reactivity with P. knowlesi indicated the presence of immunogenic conserved linear B-cell epitopes. A more extensive serologic survey of Papua New Guinea residents showed that antibody response to P. vivax DBP is common and increases with age, suggesting a possible boosting of the antibody response in some by repeated exposure to P. vivax. A positive humoral response to P. vivax DBP correlated with a significantly higher response to P. vivax MSP-1(19). The natural immunogenicity of this DBP should strengthen its usefulness as a vaccine.

Adolescent↗
PubMed1997

Comparison of protection induced by immunization with recombinant proteins from different regions of merozoite surface protein 1 of Plasmodium yoelii.

Vaccination with native full-length merozoite surface protein 1 (MSP1) or with recombinant C-terminal peptides protects mice against lethal challenge with virulent malaria parasites. To determine whether other regions of MSP1 can also induce protection, Plasmodium yoelii MSP1 was divided into four separate regions. Each was expressed in Escherichia coli as a fusion protein with glutathione S-transferase (GST). The N-terminal fragment began after the cleavage site for the signal sequence and ended in the region comparable to the cleavage site for the C terminus of the 82-kDa peptide of Plasmodium falciparum. This expressed protein was 30 kDa smaller than the predicted peptide. One peptide from the middle region was produced, and the C terminus consisted of a 42-kDa fragment corresponding to the analogous peptide of P. falciparum and a 19-kDa fragment that extended 37 amino acids in the amino-terminal direction beyond the probable cleavage site. To test protection of mice against lethal P. yoelii challenge, three mouse strains (CAF1, BALB/c, and A/J) were vaccinated with each of the four recombinant proteins of MSP1. Mice vaccinated with the C-terminal 19-kDa protein were highly protected (described previously), as were those vaccinated with the 42-kDa protein that contained the 19-kDa fragment. The N-terminally expressed fragment of P. yoelii was not full length because of proteolytic cleavage in E. coli. The GST-82-kDa partial fragments induced some immunity, but the surviving mice still had high parasitemias. Vaccination with the peptide from the middle region of MSP1 gave minimal to no protection. Therefore, in addition to the C-terminal 19- and 42-kDa proteins, the only other fragment to give protection was the 82-kDa protein. The protection induced by the truncated 82-kDa protein was minimal compared with that of the C-terminal fragments.

Animals↗
PubMed1996

Sporadic urban leptospirosis.

BACKGROUND: Surprisingly, many inner-city residents have antibodies to Leptospira interrogans. The manner in which these persons acquire this organism in the absence of recognized occupational, recreational, or epidemic risk factors is not known. OBJECTIVE: To study the epidemiology of patients with leptospirosis who acquired L. interrogans in inner-city Baltimore, Maryland. DESIGN: Epidemiologic investigation. SETTING: Inner-city university hospital. PATIENTS: Three inner-city residents who developed leptospirosis. MEASUREMENTS: Trapping rats in alleys where the patients may have acquired L. interrogans; polymerase chain reaction (PCR) analysis of patients serum and cerebrospinal fluid specimens and rat tissues to determine the presence of leptospiral DNA; and serologic testing of serum from patients and rats by microagglutination assay to confirm L. interrogans infection. RESULTS: Three patients developed leptospirosis after probable percutaneous exposure to rat (Rattus norvegicus) urine in Baltimore alleys. A PCR assay detected L. interrogans DNA in samples of body fluid obtained from the first two patients at presentation (one in cerebrospinal fluid, the other in serum). Results of PCR done on serum drawn from the third patient after antibiotic therapy began were negative. A microagglutination test showed that all patients had high levels of antibodies to the L. interrogans serogroup icterohaemorrhagiae. In 19 of 21 rats that were trapped in the alleys where the patients had sustained lacerations before illness developed, kidney or brain tissues were positive by PCR for the presence of L. interrogans. CONCLUSIONS: A population was discovered to be at risk for acquiring L. interrogans: urban residents who are sporadically exposed to rat urine in the inner city. Inner-city rats often carry L. interrogans. Polymerase chain reaction can quickly establish the diagnosis of leptospirosis and is useful for epidemiologic study. An endemic substrate for the transmission of the organism is present in inner-city Baltimore. Leptospirosis may become increasingly recognized in deteriorating inner cities in which rat populations are expanding.

Adult↗
PubMed1996

Genetic regulation of protective immune response in congenic strains of mice vaccinated with a subunit malaria vaccine.

The C-terminal 19-kDa, epidermal growth factor-like region of the merozoite surface protein 1 (MSP1) has been used as a vaccine to induce protective immunity to Plasmodium yoelii in mice and to Plasmodium falciparum in monkeys. To analyze the mechanisms and genetic regulation of this MSP1 vaccine-induced protection, we studied the immunologic correlates of protection in H-2 recombinant and congenic mouse strains on the B10 background. Multiple H-2-linked loci were found to contribute, each with a different mechanism. One locus mapped to the I-A region based on the strong protection in C57BL/10 mice compared with intermediate protection in B10.A(4R) mice and the lack of a difference between B10.AKM and B10.MBR mice. Differences in efficacy of passively transferred antisera from vaccinated C57BL/10 vs B10.A(4R) mice indicated that the protection regulated by the I-A locus was at least in part Ab dependent. Two loci mapped to the right of I-A (FE, H-2S, or H-2D) based on a correlation with the number of H-2k loci to the right of I-A in mice that were I-Ak. One effect was Ab independent and may correspond to a possible negative effect of the I-Ek locus. T cells from protected and nonprotected strains differed in their production of IFN-gamma and TNF-alpha following immunization with MSP1(19), but it was unclear how the differential patterns of cytokine expression related to the level of protection. Thus, MSP1(19) vaccine-induced protection is regulated by H-2-linked loci corresponding to two different immune mechanisms. These findings may indicate the need for more than one Ag in a vaccine to protect an HLA-diverse population.

Animals↗
PubMed1996

Expression and immunogenicity of the C-terminus of a major blood-stage surface protein of Plasmodium vivax, Pv200(19), secreted from Saccharomyces cerevisiae.

The carboxy-terminus of the major merozoite surface protein of Plasmodium has been shown to be the target of protective immunity in a number of non-vivax malaria parasite species. In an effort to develop a protective vaccine for Plasmodium vivax, the most prevalent form of human malaria, we expressed in Saccharomyces cerevisiae the 19-kDa a carboxy-terminus of Pv200 as a His6-tagged, secreted polypeptide. Five of seven H-2 congenic mouse strains elicited antibodies that recognized yeast produced PV200(19) by ELISA. The vaccine appears to be immunogenic and widely recognized, and to contain one or more helper T cell epitopes that may allow boosting with subsequent natural infections.

Amino Acid Sequence↗
PubMed1996

Identification and cloning of a locus of serine repeat antigen (sera)-related genes from Plasmodium vivax.

Polymerase chain reaction (PCR) primers based on the cysteine proteinase-like active site regions of the Plasmodium falciparum serine repeat antigen (SERA) were used to identify related sequences within the genome of P. vivax. Molecular cloning and sequence analysis of approximately 25 kb of P. vivax genomic DNA revealed a cluster of five repeated SERA-like genes (V-SERA-1-5), each encoding a cysteine proteinase-related protein. In addition to DNA sequence homology, significant similarities in deduced intron/exon organizations were also observed. The characteristic polyserine sequence found in SERA was not present in any of the deduced V-SERA sequences. Instead, in this region of the five genes, considerable sequence differences were found, suggesting the potential for antigenic variation in the V-SERA molecules. In common with SERA, however, the codon at the position corresponding to the active site cysteine residue of active mammalian and plant cysteinyl proteinases was found to be that of a serine residue in each of the V-SERA genes. Furthermore, in four of the five genes, including the expressed V-SERA-5 gene, the codon for the active site histidine residue was changed to that of a leucine residue. These critical differences reinforce the concept that a biological activity other than proteolysis is likely to be the primary function of the proteins encoded by this family of genes.

Amino Acid Sequence↗
PubMed1996

Stage-specific processing of Pfs230, a Plasmodium falciparum transmission-blocking vaccine candidate.

During Plasmodium falciparum gametocytogenesis, Pfs230, a malaria transmission-blocking vaccine candidate, is expressed as a 360 kDa protein localized to the parasitophorous vacuole/parasite plasma membrane. When gametocytes emerge from red blood cells, as they do when taken up in a blood meal by a mosquito, Pfs230 is processed from a 360 kDa form to a 310 kDa form the latter of which is exposed on the exterior surface of gametes. The 50 kDa portion of Pfs230, removed from the amino-terminus of the 360 kDa form, contains 25 contiguous glutamates and an EEVG16 repeat. Analogous to other P. falciparum proteins, the repeat region appears to be immunodominant. As the gamete emerges from the red blood cell and is exposed to the antibodies in the blood meal, cleavage of the immunodominant region of Pfs230 may contribute to an immune evasion strategy by the parasite.

Amino Acid Sequence↗
PubMed1996

Influence of adjuvants on murine immune responses against the C-terminal 19 kDa fragment of Plasmodium vivax merozoite surface protein-1 (MSP-1).

The immunogenicity of a yeast-expressed 19 kDa fragment of P vivax MSP-1 in the presence of different adjuvant formulations was evaluated. ICR mice were immunized with the 19 kDa antigen, using Freund's, alum, and block copolymer P1005 in water-in-oil (W/O) or oil-in-water (O/W) emulsions with or without detoxified lipopolysaccharide (RaLPS) as adjuvants. Five weeks following immunization with the antigen, mice were boosted with asexual blood-stage antigens. Three weeks after the last immunization with the 19 kDa antigen, mice from the Freund's group and most groups that received P1005 as adjuvant had higher total IgG titres than those that received alum as adjuvant or antigen alone. Antibody responses after the antigen immunization were predominantly of the IgG1 isotype, but mice in the Freund's and P1005 (W/O or O/W emulsion with or without RaLPS) groups also had high titres of IgG2a and IgG2b. Antibody titres against merozoites increased in all groups after the parasite antigen boost. IgG2a levels in the group that received antigen in P1005 plus RaLPS in the W/O emulsion were higher than those receiving Freund's, alum or the other copolymer adjuvants. The high IgG2a titres in this group were associated with reduced IL-10 production.

Adjuvants, Immunologic↗