A comparative study between excretory/secretory and autoclaved vaccines against RH strain of Toxoplasma gondii in murine models

Abstract

Toxoplasma gondii is an obligate intracellular protozoan that has a major importance in public health, in addition to veterinary medicine. Therefore, the development of an effective vaccine for controlling toxoplasmosis is an important goal. Excretory/secretory antigens (ESA), were previously identified as potential vaccine candidates, proved to play important roles in the pathogenesis and immune escape of the parasite. In addition, autoclaved Toxoplasma vaccine (ATV) is a special type of killed vaccine, recently characterized. The aim of the present work was, to compare between excretory/secretory and ATV against RH strain of T. gondii in mice based on; parasitological and histopathological levels. Tachyzoites were harvested from peritoneal exudates of infected mice and were used for challenge infection and vaccine preparation. BCG was used as an adjuvant. Mice were allocated equally into five groups; they were vaccinated intradermally over the sternum. The results of this study showed that the survival time after challenge, extended up to 16 days in ESA vaccinated group and up to 15 days in autoclaved Toxoplasma vaccinated group. ESA vaccinated group exhibited a profound decrease in parasite load following parasite challenge with a higher percentage of reduction in parasite count in all examined organs than the autoclaved Toxoplasma vaccinated group. The histopathological picture of the liver in both immunized groups, revealed marked reduction in the pathological changes observed as compared to controls, especially in ESA vaccinated group. It was concluded that vaccination with ESA showed more promising results versus ATV, as demonstrated by the survival rate of vaccinated mice, tachyzoites count and histopathological examination.

Immunization With a Live-Attenuated RH:ΔNPT1 Strain of Toxoplasma gondii Induces Strong Protective Immunity Against Toxoplasmosis in Mice

“…In light of the fact that T. gondii causes serious public health problems and enormous economic losses, safer and more efficient approaches need to be developed to control this ubiquitous pathogen (Dubey, 2010; Zhu et al, 2017). Previous studies have suggested that DNA vaccines, subunit vaccines, inactivated vaccines and secreted antigens could induce a certain level of humoral and cellular responses and prolong the lifespan of vaccinated mice, but none of these vaccines could provide complete protection against further infection (Innes et al, 2011; Ezz Eldin et al, 2015; Yang et al, 2017; Zheng et al, 2017). Although many researchers have performed a tremendous amount of work to pursue effective drugs and better vaccines, a mature product is unlikely to be available in the near future.…”

Remarkable histopathological improvement of experimental toxoplasmosis after receiving spiramycin-chitosan nanoparticles formulation

“…The mice were distributed into seven experimental groups (ten mice per each). T. gondii RH strain infection was induced by intraperitoneal mice injection with 2500 tachyzoites/100 µl saline/ mouse except the healthy controls [Araujo et al1992;Ezz Eldin et al 2015].…”

A Lactate Fermentation Mutant of Toxoplasma Stimulates Protective Immunity Against Acute and Chronic Toxoplasmosis

“…The first generation of vaccines contained killed parasites, or native antigens derived from soluble or secretory proteins of cultured tachyzoites. These vaccines only provided limited protection against further infections ( 15 , 16 ). Then when the recombinant DNA technology became available, a variety of subunit vaccines were tried, mainly using surface or secretory proteins such as SAG1 and MIC2 ( 17 – 20 ).…”