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A series of glycoconjugates with defined connectivity were synthesized to investigate the impact of coupling Salmonella typhimurium O-antigen to different amino acids of CRM197 protein carrier. In particular, two novel methods for site-selective glycan conjugation were developed to obtain conjugates with single attachment site on the protein, based on chemical modification of a disulfide bond and pH-controlled transglutaminase-catalyzed modification of lysine, respectively. Importantly, conjugation at the C186-201 bond resulted in significantly higher anti O-antigen bactericidal antibody titers than coupling to K37/39, and in comparable titers to conjugates bearing a larger number of saccharides. This study demonstrates that the conjugation site plays a role in determining the immunogenicity in mice and one single attachment point may be sufficient to induce high levels of bactericidal antibodies. [ABSTRACT FROM AUTHOR]

Summary The chromosome ends of human malaria parasites harbour many genes encoding proteins that are exported to the surface of infected red cells, often being involved in host–parasite interactions and immune evasion. Unlike other murine malaria parasites Plasmodium chabaudi undergoes antigenic variation during passage in the laboratory mouse and hence is a model suitable for investigation of switching mechanisms. However, little is known about the subtelomeric regions of P. chabaudi chromosomes and its variable antigens. Here we report 80 kb of sequence from an end of one P. chabaudi chromosome. Hybridization of probes spanning this region to two dimensional pulsed field gels of the genome revealed 10 multicopy gene families located exclusively in subtelomeric regions of multiple P. chabaudi chromosomes, interspersed amongst multicopy intergenic regions. Hence all chromosomes share a common subtelomeric structure, presumably playing a similar role in spatial positioning as the P. falciparum Rep20 sequence. Expression in blood stages, domains characteristic of surface antigens and copy numbers between four and several hundred per genome, indicate a functional role in antigenic variation for some of these families. We identify members of the cir family, as well as novel genes, that although clearly homologous to cir have large low complexity regions in the predicted extracellular domains. Although all families have homologues in other rodent Plasmodium species, four were previously not known to be subtelomeric. Six have homologues in human and simian malarias. [ABSTRACT FROM AUTHOR]

The merozoite surface protein 2 of P. falciparum is highly polymorphic in nature, but has regions of almost complete conservation at its N- and C-termini. We produced a chimeric recombinant protein comprising these regions only (hereafter termed NC). Mice immunized with the NC antigen produce antibodies at levels comparable to those immunized with 1624, a full-length recombinant protein representing MSP2 from P. falciparum. Antisera raised against NC recognized P. falciparum schizonts by IFA and a P. falciparum protein of Mr 45 kDa by Western blot. However, antibody specificities were observed to differ between anti-NC and anti-1624 sera, and this resulted in differences in parasite recognition, despite similar levels of antibodies having been produced. The response to the NC antigen was also shown to be restricted in some mice (H2-d), but this was overcome by including appropriate T-cell help, which was accomplished by creating recombinant protein chimeras that contained NC and T-helper epitopes from Tetanus toxoid, or MSP119 from P. berghei. [ABSTRACT FROM AUTHOR]

The effect of intra-erythrocytic development of the Plasmodium falciparum parasite on local deformability of human erythrocyte membranes was studied by aspiration of cells into 0.56 µm diameter pores in polycarhonate filters and examination, after fixing, with a scanning electron microscope. As the aspiration pressure increased, the erythrocyte membrane was extruded into the filter pores. The pressure dependence of the protrusion length and the minimum pressure required to produce any deformation provided measures of the membrane shear and the bending moduli, respectively. At the trophozoite and, to a greater extent, schizont stage of development, host cell membrane deformability was significantly decreased. There was no appreciable difference between uninfected and ring-infected erythrocytes. [ABSTRACT FROM AUTHOR]

An investigation of antigens accessible to lactoperoxidase-catalysed cell surface iodination on intact Plasmodium falciparum-infected red blood cells (RBC) has identified a 1251-labelled antigen with an apparent size of about 155 kD. This labelled protein was specifically immunoprecipitated by the following antibodies: a rabbit antiserum and a mouse monoclonal antibody raised against a synthetic peptide comprising the 3',8-mer repeat EENVEHDA of the Pf155/RESA protein; a rabbit antiserum raised against a synthetic octapeptide comprising two copies of the 3',4-mer repeat EENV of the Pf155/RESA protein; and rabbit antisera against another synthetic peptide C(MYSNNNVED)2. The last antibody shows a strong reaction in asexual blood stage parasites with the Pf155/RESA antigen. While this antigen has been described previously as a submembrane component of the outer membrane of infected RBC. this report shows that at least part of it is accessible to the surface of both ring and late trophozoite-infected erythrocytes. [ABSTRACT FROM AUTHOR]

Analyzes the specificity of T cells induced following immunization with recombinant forms of the 19kDa carboxylterminal fragment of Plasmodium yoelii merozoite surface protein 1 (MSP1[sub 19]). Absence of evidence that effector T cells can protect mice against malaria; Presence of multiple T cell epitopes in MSP1[sub 19]; Indication that such epitopes are targets of helper T cells.

Keywords: COVID-19; Epidemics; Prevention and control EN COVID-19 Epidemics Prevention and control 494 494 1 12/15/20 20201201 NES 201201 Stage 3 lockdown measures in Victoria reduced COVID-19 transmission, but more was required to control the epidemic Australia, like many other countries, had an initial rise in coronavirus disease 2019 (COVID-19) cases in March and April 2020; however, this was followed by a relatively sharp decline in May 2020 after federal and state governments introduced strict community controls. The ongoing high number of daily cases in Victoria led to concern in the community and the media about whether the Stage 3 measures before the mandatory use of mask had prevented COVID-19 transmission. Victoria faced a huge challenge to reduce transmissions to the level needed to get the COVID-19 epidemic under control. [Extracted from the article]

The Plasmodium vivax sexual stage 25 kDa protein Pvs25 is expressed on the surface of the ookinete form of the parasite. Monoclonal antibodies directed against Pvs25 block the development of P. vivax oocysts in the mosquito host. Thus, Pvs25 is a potential vaccine candidate for eliciting transmission-blocking immunity in individuals living in malaria-epidemic regions. Pvs25 which was expressed and purified for clinical trials was crystallized using polyethylene glycol as the precipitating agent and diffracts X-rays to 2.3 Å. The orthorhombic Pvs25 crystal form belongs to space group P212121, with unit-cell parameters a - 42.6, b - 59.8, c - 66.8 Å and one molecule in the asymmetric unit. Reductively methylated Pvs25 crystallized in two forms: an orthorhombic P212121 form with unit-cell parameters a - 43.4, b - 62.9, c - 66.9 Å and one molecule in the asymmetric unit and a monoclinic P21 from with unit-cell parameters a = 53.5, b - 43.3, c = 65.3 Å, β - 104.0 which was predicted to have one or two molecules in the asymmetric unit. Several native and heavy atom data sets have been collected from Pvs25 and methylated Pvs25 crystals for use in MAD or MIR techniques. [ABSTRACT FROM AUTHOR]

Investigates the cloning and characterization of a repetitive sequence of Plasmodium falciparum, REP51. Southem blot digests of Plasmodium falciparum genomic DNA; Characterization of an array of 450 containing inserts by examination of the Sau3AI digestion profiles of the plasmid DNA of 250 of the clones and by hybridization of the inserts from selected clones to the whole array.

Studies the conservation of repeating structures in the PfEMP2/MESA antigenic protein of Plasmodium falciparum. Genomic DNA of Plasmodium falciparum; Use of recombinant proteins to purify antibodies from the Aotus antisera.

Glycoproteins In their Communication on page 13198 ff., Q.‐Y. Hu, F. Micoli et al. present two methods for the preparation of glycoconjugate vaccines with one single sugar chain linked to one or two positions of a carrier protein. [ABSTRACT FROM AUTHOR]