Bioinformatics-based prediction and screening of immunogenic epitopes of Toxoplasma gondii rhoptry proteins 7, 21 and 22 as candidate vaccine target

Introduction

Toxoplasmosis is a well-known zoonotic disease caused by Toxoplasma gondii. The main causes of the disease range from eating undercooked or contaminated meat and shellfish to cleaning litter trays into which cats that excreted toxoplasma via faeces. This pathogen can live for a very long time, possibly a lifetime, within the bodies of humans and other animals.

Aims and objectives

This study aimed to predict and analyse candidate immunogenic epitopes for vaccine development by evaluating the physio-chemical properties, multiple sequence alignment, secondary and tertiary structures, phosphorylation sites, transmembrane domains, and signal peptides, of T. gondii rhoptry proteins ROP7, ROP21, and ROP22 using bioinformatics tools.

Methods

To find immunogenic epitopes of rhoptry proteins, numerous bioinformatics web servers were used containing multiple sequence alignment, physiochemical properties, antigenicity and allergenicity, post-translational modification sites (PTMs), signal peptides, transmembrane domains, secondary and tertiary structures, and screening of predicted epitopes. We evaluated immunogenic linear B-cell epitopes as candidate proteins for vaccine development.

Results

Nine epitopes were identified for each protein, and analysis of immunogenicity, revealed three candidate epitopes for ROP7, one for ROP21, and four for ROP22. Among all candidate epitopes, ROP22 contained the most immunogenic epitopes with immunogenicity score of 0.50575.

Conclusion

We acquired detailed information on predicted immunogenic epitopes using in-silico methods. The results provide a foundation for further experimental analysis of toxoplasmosis, and potential vaccine development.

118 A retrospective analysis of follicular dynamics, LH, estradiol-17β, and progesterone in prostaglandin F2α-induced estrus of Beetal goats

The objective of the study was to reveal the factors associated with variable interval to ovulation following a single dose of prostaglandin F2α (PGF2) in Beetal goats. In experiment 1, the extent of ovulation time was demonstrated after synchronizing Beetal goats (n=38) by using a single injection of PGF2 based on corpus luteum detection by B-mode transrectal ultrasonography. Ovulations were detected every 6h from PGF2 until ovulation. To explore the changes in follicular dynamics, endocrine profiles and behavioural events due to the variation in the interval to ovulation, another set of goats (n=13; experiment 2) were synchronized by a single dose of PGF2 given at random days of the luteal phase. Follicular dynamics were monitored every 12h from PGF2 until ovulation and oestrus was detected by apronized bucks every 6h from PGF2 treatment. Blood sampling (3mL) for oestradiol-17β and progesterone was done every 12h from PGF2 until ovulation and every 2h for LH assay by radioimmunoassay. Data were analysed by Student’s t-test, general linear models, and Pearson coefficient correlation (SPSS, version 20.0, SPSS Inc., Chicago, IL, USA). Results revealed that ovulation time varied from 60 to 96h after PGF2, and 57% of ovulations occurred by 72h after PGF2 (experiment 1). Based on this observation, goats (n=13) in second experiment were retrospectively divided into early and late ovulators (i.e. 72 and 84h following PGF2, respectively). Onset of oestrus, peak oestradiol-17β concentration, and LH surge after PGF2 were first observed in early than late ovulators (P<0.05). The goats having greater follicle diameter and smaller corpus luteum diameter at the time of PGF2 ovulated earlier than late ovulators (5.4±0.2v. 4.3±0.2mm and 10±0.6v. 11.8±0.3mm, respectively; P<0.05). Likewise, plasma progesterone concentration tended to be lower (P=0.087) in early than late ovulators. However, interval from onset of oestrus to peak LH and ovulation, duration of standing oestrus, interval from LH peak to ovulation, diameter and growth rate of preovulatory follicles, and number of ovulations were similar (P>0.05) between early and late ovulators. In conclusion, the size of dominant follicle and corpus luteum at the time of PGF2 determines the interval to ovulation following a single dose of PGF2 during the luteal phase.