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Background: COVID-19 is a worldwide pandemic that stroke almost all countries of the world causing thousands of deaths and disabilities and burdened the economy of countries. One of the main criteria of the immune response against COVID-19 is the “immune exhaustion”, due to increased expression of T cell suppressor molecules e.g. programmed death-1 (PD-1), that leads to flaring of viral multiplication and disastrous clinical outcomes. This immune exhaustion is not restricted to COVID-19 but is also a common complication of chronic infections with the widely spreading protozoan, Toxoplasma (T.) gondii. Thus, theoretically, the toxoplasmosis-associated immune exhaustion can worsen that of COVID-19 and consequently increases its severity. However, the studies on this theory are still insufficient. Objective: this work was designed to answer two questions. Does T. gondii co-infection affect the severity of COVID-19 manifestations? Is this action related to T. gondii-induced PD-1 changes? Methodology: Covid-19+ patients with moderate and severe conditions were screened for T. gondii IgG and compared to healthy controls. Serum levels of IL-1β, IL-6, TNFα, IFNγ, IL-1α cytokines were assessed to evaluate COVID-19 severity and prognosis. Lymphocytic expression of PD-1 was assessed by flowcytometry. Results: We recorded a higher incidence of toxoplasmosis among COVID-19 patients especially patients with severe/critical manifestations. T. gondii positive cases exhibited a statistically significant increase in lymphocytic expression of PD-1 that correlated positively with the proinflammatory and bad prognosis cytokines. With fixation of other risk factors for severity, toxoplasmosis still scored a significant value. Conclusion: toxoplasmosis increased the severity of COVID-19. These effects can be related to the Toxoplasmaassociated increased lymphocytic PD-1 expression. So, toxoplasmosis can be considered as an unrecognized independent risk factor for COVID-19 severity.

Schistosomiasis is the second commonest parasitic disease worldwide. It is responsible for thousandsof deaths per year in addition to the associating serious morbidities that burden both individuals andcommunities. To date, the main preventive measure of infection is mass treatment with praziquantel. itcarries the risk of reinfection and rising resistance which makes the discovery of an effective vaccinean urgent necessity. The present study evaluated E. camaldulensis killed cercariae immunogen (KCI)as a candidate vaccine for experimental schistosomiasis mansoni and to detect the possible immunologicalmechanisms of action of this immunogen. The KCI caused a significant reduction of bothschistosomula and adult worm counts with subsequent ova count reduction. Hepatic granulomas werereduced in number or size. Also, levels of IgG, IgG1 & IgG2a as well as INF-γ & IL-10 fluctuatedlarger than in natural infection.

Schistosomiasis is the second most common parasitic infection all over the world. It is responsible for thousands of deaths per year. Control of this infection depends mainly on praziquantel which unfortunately has many defects e.g. occurrence of reinfection and risk of resistance. So, a suitable vaccine is an urgent need. The vaccination that elicits a combined Th1 and Th2 is considered a proper vaccine candidate. Trehalose Dimycolate (TDM) is an immunogen that proved potent activation of Th1 lymphocytes. Effects of its combination with the Th2 stimulant, soluble egg antigen (SEA) in protection against Schistosoma mansoni infection in experimental animals were studied. Combined SAE+TDM achieved statistically significant protection against infection causing reduction of the worm load and ova count. A large percentage of the laid ova were even immature. Combined immunization was associated with reduced hepatic granuloma number, diameter and hepatic fibrosis percentage. Moreover, SEA+TDM increased stimulation of M2 type macrophages that limited the spread of hepatic fibrosis. It was concluded that SEA+TDM achieved the best protection from infection and the resulting pathology.This can be regarded to increased activation of humoral and cellular wings of immunity and activations of both anti-S. mansoni and tissue protecting macrophages and cytokines.

Schistosomiasis is the second most common human parasitic disease worldwide. It is responsible for 300000 deaths per year. Liver fibrosis is the main pathology of schistosomiasis and its complications are the major cause of death in infected cases. Unfortunately, the therapeutic dose of praziquantel (PZQ) – the main drug treatment – doesn't markedly affect fibrosis. In the present study, antiparasitic and hepatoprotective properties of artichoke leaf extract (ALE) were tested on mice experimentally infected with Schistosoma mansoni (S. mansoni) and were compared to PZQ. Four mice groups were infected with S. mansoni. The first three groups received ALE, ALE + PZQ and PZQ respectively. The 4th was the positive control and the 5th was the negative control group. Worm load, egg count, granuloma numbers and diameters were measured to assess ALE anti-schistoaomal properties. Masson's trichrome staining of fibrosis, immune staining of hepatic stellate cells (HSCs) and estimation of liver enzymes were done to assess its hepato-protective action. Although it had no significant effects on worm or tissue egg load and granuloma number, ALE caused significant reduction of granuloma diameter, improvement of liver functions and liver fibrosis. ALE caused statistically significant changes in HSCs distribution. It reduced granuloma size by increasing HSCs recruitment inside granuloma and limited liver fibrosis by their inhibition in the peri- and inter-granuloma liver tissue. It was concluded that despite failure of ALE to treat S. mansoni infection, it can limit liver damage caused by this parasite by modulating HSCs recruitment.