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We report photometric and spectroscopic observations of the eclipsing SU UMa-type dwarf nova ASASSN-18aan. We observed the 2018 superoutburst with 2.3 mag brightening and found the orbital period ($P_{\rm orb}$) to be 0.149454(3) d, or 3.59 hr. This is longward of the period gap, establishing ASASSN-18aan as one of a small number of long-$P_{\rm orb}$ SU UMa-type dwarf novae. The estimated mass ratio, ($q=M_2/M_1 = 0.278(1)$), is almost identical to the upper limit of tidal instability by the 3:1 resonance. From eclipses, we found that the accretion disk at the onset of the superoutburst may reach the 3:1 resonance radius, suggesting that the superoutburst of ASASSN-18aan results from the tidal instability. Considering the case of long-$P_{\rm orb}$ WZ Sge-type dwarf novae, we suggest that the tidal dissipation at the tidal truncation radius is enough to induce SU UMa-like behavior in relatively high-$q$ systems such as SU UMa-type dwarf novae, but that this is no longer effective in low-$q$ systems such as WZ Sge-type dwarf novae. The unusual nature of the system extends to the secondary star, for which we find a spectral type of G9, much earlier than typical for the orbital period, and a secondary mass $M_2$ of around 0.18 M$_{\odot}$, smaller than expected for the orbital period and the secondary's spectral type. We also see indications of enhanced sodium abundance in the secondary's spectrum. Anomalously hot secondaries are seen in a modest number of other CVs and related objects. These systems evidently underwent significant nuclear evolution before the onset of mass transfer. In the case of ASASSN-18aan, this apparently resulted in a mass ratio lower than typically found at the system's $P_{\rm orb}$, which may account for the occurrence of a superoutburst at this relatively long period., Comment: 17 pages, 14 figures, accepted for publication in PASJ

arXiv:2104.04948v1, et al., We present spectroscopic and photometric observations of 17 dwarf-nova superoutbursts obtained by KOOLS-IFU mounted on the 3.8 m telescope Seimei at the Okayama Observatory of Kyoto University and through the Variable Star Network collaboration (VSNET). Our spectroscopic observations for six outbursts were performed within 1 d of their optical peak. 11 objects (TCP J00590972+3438357, ASASSN-19ado, TCP J06073081−0101501, ZTF20aavnpug, ASASSN-19ady, MASTER OT J061642.05+435617.9, TCP J20034647+1335125, ASASSN-20kv, ASASSN-20kw, MASTER OT J213908.79+161240.2, and ASASSN-20mf) were previously unknown systems, and our observations enabled quick classification of their transient type. These results illustrate that the Seimei telescope has the capability to conduct quick follow-up observations of unknown transients. Our photometric observations yielded that 11 of the objects are WZ Sge-type dwarf novae and their candidates, and the other six are SU UMa-type dwarf novae and their candidates. The He ii 4686 Å emission line was clearly detected among ASASSN-19ado, TCP J06073081−0101501 and MASTER OT J213908.79+161240.2, the association of which with a spiral arm structure in an accretion disk has been suggested in previous studies. Our result suggests that a higher-inclination system shows a stronger emission line of He ii 4686 Å, as well as larger-amplitude early superhumps., Maeda acknowledges support from the Japan Society for the Promotion of Science (JSPS) KAKENHI grant JP18H05223, JP20H00174, and JP20H04737. U. Burgaz acknowledges the support provided by the Turkish Scientific and Technical Research Council (TÜBITAK2211C and 2214A). This work was supported by the project APVV-15-0458 “Interacting binaries - Key for the Understanding of the Universe”. This work was supported by the Slovak Research and Development Agency under the contract No. APVV15-0458 and by the Slovak Academy of Sciences grant VEGA No. 2/0030/21. The authors from Sternberg institute thank the Program of Development of Lomonosov MSU ‘Leading Scientific Schools’. A.A.B, N.P.I. and M.A.B. (SAI MSU) are supported by the Interdisciplinary Scientific and Educational School of Moscow University ’Fundamental and Applied Space Research’. This research was partly supported by the Slovak Academy of Sciences grant VEGA No. 2/0030/21.

arXiv:2004.10508v1, et al., We report on photometric and spectroscopic observations and analysis of the 2019 superoutburst of TCP J21040470+4631129. This object showed a 9 mag superoutburst with early superhumps and ordinary superhumps, which are the features of WZ Sge-type dwarf novae. Five rebrightenings were observed after the main superoutburst. The spectra during the post-superoutburst stage showed Balmer, He I, and possible sodium doublet features. The mass ratio is derived as 0.0880(9) from the period of the superhump. During the third and fifth rebrightenings, growing superhumps and superoutbursts were observed, which have never been detected during a rebrightening phase among WZ Sge-type dwarf novae with multiple rebrightenings. To induce a superoutburst during the brightening phase, the accretion disk needs to have expanded beyond the 3 : 1 resonance radius of the system again after the main superoutburst. These peculiar phenomena can be explained by the enhanced viscosity and large radius of the accretion disk suggested by the higher luminosity and the presence of late-stage superhumps during the post-superoutburst stage, plus by more mass supply from the cool mass reservoir and/or from the secondary because of the enhanced mass transfer than those of other WZ Sge-type dwarf novae., N. Narita is supported by JSPS KAKENHI Grant Numbers JP18H01265 and JP18H05439, and JST PRESTO Grant Number JPMJPR1775. M. Tamura is supported by MEXT/JSPS KAKENHI Grant Nos. 18H05442, 15H02063, and 22000005. P. A. Dubovsky, T. Medulka, and I. Kudzej acknowledge support by NSF AST-1751874 and the Cottrell scholarship from the Research Corporation for Science Advancement and by the Slovak Research and Development Agency under the contract No. APVV-15-0458. A. Zubareva, A. Belinski, A. Dodin, M. Burlak, N. Ikonnikova, E. Mishin, and S. Potanin acknowledge the support from the Program of development of M.V. Lomonosov Moscow State University (Leading Scientific School “Physics of stars, relativistic objects and galaxies”). E. P. Pavlenko, O. I. Antonyuk, and Ju. V. Bbabina acknowledge support by the RSF grant 19-72-10063.

Background Previous studies have shown that the baculovirus-vectored vaccine based on the “baculovirus dual expression system (BDES)” is an effective vaccine delivery platform for malaria. However, a point of weakness remaining for use of this vaccine platform in vivo concerns viral inactivation by serum complement. In an effort to achieve complement resistance, the gene encoding the human decay-accelerating factor (hDAF) was incorporated into the BDES malaria vaccine expressing the Plasmodium falciparum circumsporozoite protein (PfCSP). Results The newly-developed BDES vaccine, designated BDES-sPfCSP2-Spider, effectively displayed hDAF and PfCSP on the surface of the viral envelope, resulting in complement resistance both in vitro and in vivo. Importantly, upon intramuscular inoculation into mice, the BDES-sPfCSP2-Spider vaccine had a higher protective efficacy (60%) than that of the control vaccine BDES-sPfCSP2-Spier (30%) against challenge with transgenic Plasmodium berghei sporozoites expressing PfCSP. Conclusion DAF-shielded BDES-vaccines offer great potential for development as a new malaria vaccine platform against the sporozoite challenge. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-2039-x) contains supplementary material, which is available to authorized users.

A multistage malaria vaccine targeting the pre-erythrocytic and sexual stages of Plasmodium could effectively protect individuals against infection from mosquito bites and provide transmission-blocking (TB) activity against the sexual stages of the parasite, respectively. This strategy could help prevent malaria infections in individuals and, on a larger scale, prevent malaria transmission in communities of endemicity. Here, we describe the development of a multistage Plasmodium vivax vaccine which simultaneously expresses P. vivax circumsporozoite protein (PvCSP) and P25 (Pvs25) protein of this species as a fusion protein, thereby acting as a pre-erythrocytic vaccine and a TB vaccine, respectively. A new-concept vaccine platform based on the baculovirus dual-expression system (BDES) was evaluated. The BDES-Pvs25-PvCSP vaccine displayed correct folding of the Pvs25-PvCSP fusion protein on the viral envelope and was highly expressed upon transduction of mammalian cells in vitro . This vaccine induced high levels of antibodies to Pvs25 and PvCSP and elicited protective (43%) and TB (82%) efficacies against transgenic P. berghei parasites expressing the corresponding P. vivax antigens in mice. Our data indicate that our BDES, which functions as both a subunit and DNA vaccine, can offer a promising multistage vaccine capable of delivering a potent antimalarial pre-erythrocytic and TB response via a single immunization regimen.

During rice (Oryza sativa L.) seed development, the primary endosperm nucleus undergoes a series of divisions without cytokinesis, producing a multinucleate cell, known as a syncytium. After several rounds of rapid nuclear proliferation, the syncytium ceases to undergo mitosis; thereafter, the syncytium is partitioned into individual cells by a specific type of cytokinesis called cellularization. The transition between syncytium and cellularization is important in determining the final seed size and is a model for studying the cell cycle and cytokinesis. The involvement of cyclin-dependent kinase (CDK) inhibitors (CKIs) in cell cycle control was investigated here during the transition between syncytium and cellularization. It was found that one of the rice CKIs, Orysa;KRP3, is strongly expressed in the caryopsis at 2 d after flowering (DAF), and its expression is significantly reduced at 3 DAF. The other CKI transcripts did not show such a shift at 2 DAF. In situ hybridization analysis revealed that Orysa;KRP3 is expressed in multinucleate syncytial endosperm at 2 DAF, but not in cellularized endosperm at 3 DAF. Two-hybrid assays showed that Orysa;KRP3 binds Orysa;CDKA;1, Orysa;CDKA;2, Orysa;CycA1;1, and Orysa;CycD2;2. By contrast, Orysa;CDKB2;1 and Orysa;CycB2;2 do not show binding to Orysa;KRP3. Orysa;KRP3 was able to rescue yeast premature cell division due to the dominant positive expression of mutant rice CDKA;1 indicating that Orysa;KRP3 inhibited rice CDK. These data suggest that Orysa;KRP3 is involved in cell cycle control of syncytial endosperm.

The glycosidic fraction from the dried roots of Panax notoginseng (Burk.) F.H.Chen exhibited an inhibitory effect on zoospore motility of Aphanomyces cochlioides . Further study on this fraction afforded fourteen dammarane-type saponins. Their structures were determined on the basis of spectroscopic and chemical methods. Eleven were known compounds, and the three new ones were 3- O -[β- d -glucopyranosyl (1→6)-β- d -glucopyranosyl]-20- O -β- d -glucopyranosyl 3β, 12β, 20 ( S )-trihydroxydammar-24-ene, 3- O -β- d -glucopyranosyl 20- O -[α- l -arabinopyranosyl (1→2)-β- d -glucopyranosyl] 3β, 12β, 20 ( S )-trihydroxydammar-24-ene and 6- O -β- d -glucopyranosyl 20- O -β- d -glucopyranosyl 3β, 6α, 12β, 20 ( S ), 25-pentahydroxydammar-23-ene, respectively. Each saponin displayed good inhibitory effects on zoospore motility.

A photo-sensitive amino acid analogue was introduced into an outer membrane lipoprotein, Pal, and then subjected to photo-crosslinking with the lipoprotein-specific ABC transporter LolCDE. Pal crosslinked to LolE but not LolC in vivo despite that both are structurally similar membrane subunits. LolCDE liganded with Pal containing the photo-sensitive amino acid analogue was isolated and subjected to in vitro photo-crosslinking. LolE was found to be the binding site for Pal. ATP binding to LolD decreased the LolE–Pal crosslinking by decreasing their hydrophobic interaction. ATP hydrolysis in the presence of LolA completely abolished the LolE–Pal crosslinking and, concomitantly, generated a new LolA–Pal crosslinked product. Structured summary of protein interactions LolE and Pal physically interact by cross-linking study ( View interaction ) LolE and Pal bind by cross-linking study ( View interaction ) Pal and Pal bind by cross-linking study ( View interaction ) Pal and LolA physically interact by competition binding ( View interaction )

In a survey of plant secondary metabolites regulating the behaviour of Aphanomyces cochlioides zoospores, we found that root extracts of Portulaca oleracea inhibited zoospore motility. Bioassay-directed fractionation of Portulaca constituents revealed that the inhibitory activity was dependent on the interaction of two chemically different factors. These were identified as a phenolic compound, N-trans-feruloyltyramine, which by itself was active as a zoospore stimulant, and an acidic compound, 1-linoleoyl-2-lysophosphatidic acid monomethyl ester, which had zoospore-repellent activity. When Chromosorb W AW particles coated with a mixture of these pure compounds were bioassayed in Petri dishes, the inhibitory effect on zoospore motility was identical with that caused by root tip or root extracts of P. oleracea. Inhibited zoospores rapidly settled to the bottom of the Petri dishes where they initially encysted, and then germinated within 1–2 h. This is the first report of factors which inhibit zoospore motility without killing or bursting the zoospores.

Anti-malarial transmission-blocking vaccines (TBVs) aim to inhibit the transmission of Plasmodium from humans to mosquitoes by targeting the sexual/ookinete stages of the parasite. Successful use of such interventions will subsequently result in reduced cases of malarial infection within a human population, leading to local elimination. There are currently only five lead TBV candidates under examination. There is a consequent need to identify novel antigens to allow the formulation of new potent TBVs. Here we describe the design and evaluation of a potential TBV (BDES-PbPSOP12) targeting Plasmodium berghei PSOP12 based on the baculovirus dual expression system (BDES), enabling expression of antigens on the surface of viral particles and within infected mammalian cells. In silico studies have previously suggested that PSOP12 (Putative Secreted Ookinete Protein 12) is expressed within the sexual stages of the parasite (gametocytes, gametes and ookinetes), and is a member of the previously characterized 6-Cys family of plasmodial proteins. We demonstrate that PSOP12 is expressed within the sexual/ookinete forms of the parasite, and that sera obtained from mice immunized with BDES-PbPSOP12 can recognize the surface of the male and female gametes, and the ookinete stages of the parasite. Immunization of mice with BDES-PbPSOP12 confers modest but significant transmission-blocking activity in vivo by active immunization (53.1% reduction in oocyst intensity, 10.9% reduction in oocyst prevalence). Further assessment of transmission-blocking potency ex vivo shows a dose-dependent response, with up to a 76.4% reduction in intensity and a 47.2% reduction in prevalence observed. Our data indicates that PSOP12 in Plasmodium spp. could be a potential new TBV target candidate, and that further experimentation to examine the protein within human malaria parasites would be logical.

Background The approach of using transgenic rodent malaria parasites to assess the immune system’s response to antigenic targets from a human malaria parasite has been shown to be useful for preclinical evaluation of new vaccine formulations. The transgenic Plasmodium berghei parasite line [PvCSP(VK210)/Pb] generated previously expresses the full-length circumsporozoite protein (CSP) VK210 from Plasmodium vivax. The transgenic parasite expresses one of the two most common alleles of CSP, defined by nine amino acids at the central repeat region of this protein. In the present study, a transgenic P. berghei parasite line [PvCSP(VK247)/Pb] expressing the full-length PvCSP(VK247), which is the alternative common allele, was generated and characterized. Methods The P. berghei expressing full-length PvCSP(VK247) was generated and examined its applicability to CSP-based vaccine research by examining its biological characteristics in mosquitoes and mice. Results Similar to PvCSP(VK210)/Pb, PvCSP(VK247)/Pb developed normally in mosquitoes and produced infectious sporozoites equipped to generate patent infections in mice. Invasion of HepG2 cells by PvCSP(VK247)/Pb sporozoites was inhibited by an anti-PvCSP(VK247) repeat monoclonal antibody (mAb), but not by an anti-PvCSP(VK210) repeat mAb. Conclusions These two transgenic parasites thus far can be used to evaluate the potential efficacy of PvCSP-based vaccine candidates encompassing the two major genetic variants in preclinical trials.