The global outbreak of severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) urgently requires an effective vaccine for prevention. In this study, 66 epitopes containing pentapeptides of SARS‐CoV‐2 spike protein in the IEDB database were compared with the amino acid sequence of SARS‐CoV‐2 spike protein, and 66 potentially immune‐related peptides of SARS‐CoV‐2 spike protein were obtained. Based on the single‐nucleotide polymorphisms analysis of spike protein of 1218 SARS‐CoV‐2 isolates, 52 easily mutated sites were identified and used for vaccine epitope screening. The best vaccine candidate epitopes in the 66 peptides of SARS‐CoV‐2 spike protein were screened out through mutation and immunoinformatics analysis. The best candidate epitopes were connected by different linkers in silico to obtain vaccine candidate sequences. The results showed that 16 epitopes were relatively conservative, immunological, nontoxic, and nonallergenic, could induce the secretion of cytokines, and were more likely to be exposed on the surface of the spike protein. They were both B‐ and T‐cell epitopes, and could recognize a certain number of HLA molecules and had high coverage rates in different populations. Moreover, epitopes 897‐913 were predicted to have possible cross‐immunoprotection for SARS‐CoV and SARS‐CoV‐2. The results of vaccine candidate sequences screening suggested that sequences (without linker, with linker GGGSGGG, EAAAK, GPGPG, and KK, respectively) were the best. The proteins translated by these sequences were relatively stable, with a high antigenic index and good biological activity. Our study provided vaccine candidate epitopes and sequences for the research of the SARS‐CoV‐2 vaccine.

Background: Leishmania species belong to the family Trypanosomatidae and cause leishmaniasis, a geographically widespread disease that infects humans and other vertebrates. This disease remains endemic in China. Due to the large geographic area and complex ecological environment, the taxonomic position and phylogenetic relationship of Chinese Leishmania isolates remain uncertain. A recent internal transcribed spacer 1 and cytochrome oxidase II phylogeny of Chinese Leishmania isolates has challenged some aspects of their traditional taxonomy as well as cladistics hypotheses of their phylogeny. The current study was designed to provide further disease background and sequence analysis. Methods: We systematically analyzed 50 cytochrome b (cyt b) gene sequences of 19 isolates (16 from China, 3 from other countries) sequenced after polymerase chain reaction (PCR) using a special primer for cyt b as well as 31 sequences downloaded from GenBank. After alignment, the data were analyzed using the maximum parsimony, Bayesian and netwok methods. Results: Sequences of six haplotypes representing 10 Chinese isolates formed a monophyletic group and clustered with Leishmania tarentolae. The isolates GS1, GS7, XJ771 of this study from China clustered with other isolates of Leishmania donovani complex. The isolate JS1 was a sister to Leishmania tropica, which represented an L. tropica complex instead of clustering with L. donovani complex or with the other 10 Chinese isolates. The isolates KXG-2 and GS-GER20 formed a monophyletic group with Leishmania turanica from central Asia. In the different phylogenetic trees, all of the Chinese isolates occurred in at least four groups regardless of geographic distribution. Conclusions: The undescribed Leishmania species of China, which are clearly causative agents of canine leishmaniasis and human visceral leishmaniasis and are related to Sauroleishmania, may have evolved from a common ancestral parasite that came from the Americas and may have split off earlier than the other old world Leishmania. Our results also suggest the following: the isolates GS7, GS1 and XJ771 occur as part of the L. donovani complex; the JS1 isolate is L. tropica; and the isolate GS-GER20 identified as Leishmania gerbilli is close to KXG-2 which is L. turanica.

Toxoplasma gondii is one of the most widespread obligatory parasitic protozoa which infect nearly all the warm-blooded animals, leading to toxoplasmosis. Current administration of the therapeutic drugs like the combination of pyrimethamine and sulfadiazine shows high rates of toxic side effects and encounters drug resistance in some cases. Resveratrol is a natural plant extracts with multiple functions, such as anti-bacterial, anti-cancer and anti-parasite activities. In this study, we evaluated the inhibitory effects of resveratrol upon the tachyzoites of Toxoplasma gondii RH strain extracellularly and intracellularly. We demonstrated that resveratrol possessed a direct anti-toxoplasma activity by reducing the population of extracellularly grown tachyzoites, probably through disturbing the redox homeostasis of the parasites. Moreover, resveratrol was also able to release the burden of cellular stress, promote the apoptosis and maintain the autophagic status of macrophages that were turned out to be regulated by intracellular parasites, thereby functioning indirectly in eliminating T. gondii. In conclusion, resveratrol has both direct and indirect anti-toxoplasma effects against the RH tachyzoites and may possess a potential to be further evaluated and employed in toxoplasmosis treatment.

In order to identify immunodominant antigens ofMycobacterium tuberculosisthat may be used in the serodiagnosis of active tuberculosis (TB), we designed anM. tuberculosisfusion protein consisting of CFP-10 (10-kDa culture filtrate protein), ESAT-6 (6-kDa early secreted antigenic target), and the extracellular domain fragment of PPE68 (PPE68′). Then, the coding sequences of the three proteins were inserted into a prokaryotic expression vector, pET-32a(+). To enhance the immunological response, the proteins were linked together. The fusion proteins with a 6×His tag were successfully overexpressed inEscherichia coliBL21 and purified. The purified proteins were applied for detection of the total IgG titer by using an enzyme-linked immunosorbent assay (ELISA) with human sera from well-characterized TB cases and the control cases, and results were compared to those with purified protein derivative tuberculin (PPD). The ELISA results showed that among 140 cases of confirmed active TB and 70 control cases, CFP-10–ESAT-6–PPE68′ had a sensitivity of 73.3% and specificity of 94.3%, compared to a sensitivity of 66.7% and specificity of 74.3% for PPD and a sensitivity of 65% and specificity of 91.4% for CFP-10–ESAT-6. In addition, the fusion protein CFP-10–ESAT-6–PPE68′ stimulated a higher level of antigen-specific gamma interferon (IFN-γ) release for active-TB patients than PPD and CFP-10–ESAT-6. After immunization of C57BL/6 mice, the findings indicated that the total IgG titers and the concentrations of IFN-γ in mice immunized by CFP-10–ESAT-6–PPE68′ were high and induced strong, long-term humoral immunity compared to results with PPD and CFP-10–ESAT-6. Thus, our study indicates that the fusion protein CFP-10–ESAT-6–PPE68′ may be useful as an immunodominant antigen for the serodiagnosis of active TB.