Immunosuppression with cyclophosphamide favors reinfection with recombinant Toxoplasma gondii strains

Can Lacticaseibacillus rhamnosus CRL1505 postbiotic improve emergency myelopoiesis in immunocompromised mice?

We evaluated whether viable and non-viable Lacticaseibacillus rhamnosus CRL1505 (Lr05V or Lr05NV, respectively) was able to improve emergency myelopoiesis induced by Streptococcus pneumoniae (Sp) infection. Adult Swiss-mice were orally treated with Lr05V or Lr05NV during five consecutive days. The Lr05V and Lr05NV groups and untreated control group received an intraperitoneal dose of cyclophosphamide (Cy-150 mg/kg). Then, the mice were nasally challenged with Sp (107 UFC/mice) on day 3 post-Cy injection. After the pneumococcal challenge, the innate and myelopoietic responses were evaluated. The control group showed a high susceptibility to pneumococcal infection, an impaired innate immune response and a decrease of hematopoietic stem cells (HSCs: Lin-Sca-1+c-Kit+), and myeloid multipotent precursors (MMPs: Gr-1+Ly6G+Ly6C-) in bone marrow (BM). However, lactobacilli treatments were able to significantly increase blood neutrophils and peroxidase-positive cells, while improving cytokine production and phagocytic activity of alveolar macrophages. This, in turn, led to an early Sp lung clearance compared to the control group. Furthermore, Lr05V was more effective than Lr05NV to increase growth factors in BM, which allowed an early HSCs and MMPs recovery with respect to the control group. Both Lr05V and Lr05NV were able to improve BM emergency myelopiesis and protection against respiratory pathogens in mice undergoing chemotherapy.

Modifiable contributing factors to COVID-19: A comprehensive review

The devastating complications of coronavirus disease 2019 (COVID-19) result from an individual's dysfunctional immune response following the initial severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. Multiple toxic stressors and behaviors contribute to underlying immune system dysfunction. SARS-CoV-2 exploits the dysfunctional immune system to trigger a chain of events ultimately leading to COVID-19. The current study identifies eighty immune system dysfunction-enabling toxic stressors and behaviors (hereafter called modifiable contributing factors (CFs)) that also link directly to COVID-19. Each CF is assigned to one of the five categories in the CF taxonomy shown in Section 3.3.: Lifestyle (e.g., diet, substance abuse); Iatrogenic (e.g., drugs, surgery); Biotoxins (e.g., micro-organisms, mycotoxins); Occupational/Environmental (e.g., heavy metals, pesticides); Psychosocial/Socioeconomic (e.g., chronic stress, lower education). The current study shows how each modifiable factor contributes to decreased immune system capability, increased inflammation and coagulation, and increased neural damage and neurodegeneration. It is unclear how real progress can be made in combatting COVID-19 and other similar diseases caused by viral variants without addressing and eliminating these modifiable CFs.

Immunological, histopathological, and ultrastructural evidence of steroid-induced reactivation of chronic murine toxoplasmosis

We developed a model of steroid-induced reactivation of chronic murine toxoplasmosis to mirror similar effects of steroids or other immunosuppressants in infected humans. Immunological, histopathological, and ultrastructural parameters were reported. Prior to steroid administration, mice were infected with 10 cysts of the Me49 strain of Toxoplasma gondii. Mice were treated with dexamethasone (DXM, 2.5 mg/kg/day in drinking water), alone or combined with Solu-Cortef (SOLU, 50 mg/kg by subcutaneous injection 3 times a week) for 7 weeks or left untreated as control. Histopathological changes and ultrastructural effects of steroids on the course of chronic toxoplasmosis were recorded. By electron microscopy, the brains of infected combined treated mice showed an increase in number of tachyzoites and bradyzoites, degeneration, and necrosis of neural cells and hydropic degeneration besides the observed rupture of toxoplasma cysts releasing free tachyzoites in brain tissue. DXM+SOLU-combined treatment also significantly increased mortality, mean brain cyst count as compared to infected untreated mice (P = .01 and). Moreover, 3/12 (25%) treated animals developed clinical signs of toxoplasmic encephalitis. This simple model of drug-induced reactivation of chronic toxoplasmosis permits investigation of host-parasite interaction and may be used for the evaluation of chemotherapeutics in immunocompromised infected patients.

Tissue dissemination and humoral response after experimental reinfection with atypical Toxoplasma gondii strains obtained from congenital human toxoplasmosis in Brazil

The paradigm that Toxoplasma gondii infection generates sterilizing protective immunity was broken by case studies in which reinfections were observed in immunocompetent pregnant women in the chronic phase of toxoplasmosis. Since then, several murine models have suggested that immunoprotection against a previous T. gondii infection may be violated after reinfection with strains of different genotypes. This study aimed to evaluate the dissemination of the parasite after reinfection with the virulent TgCTBr9 and EGS strains in BALB/c mice chronically infected with the avirulent TgCTBr5 strain. Three mice were euthanized at 2, 4, 8, 12, 24 and 48 h post challenge (p.c.) and at 7, 14 and 30 days p.c. Intestines, mesenteric lymph nodes, lungs and brains were collected for PCR-RFLP. Blood samples were collected to measure total IgG, IgG1 and IgG2a by ELISA. The reinfected animals survived and presented reduced morbidity after challenge with the virulent strains. Mice challenged with the TgCTBr9 strain showed a slight increase in anti-T. gondii IgG1. The spread of the TgCTBr5 strain was observed to occur earlier than the dissemination of the virulent TgCTBr9 or EGS strains. The TgCTBr9 strain was observed in the mesenteric lymph node at 7 days post challenge (d.p.c.); in the intestine and lungs at 14 d.p.c.; and in the brain at 30 d.p.c. EGS strain was demonstrated in the mesenteric lymph node and lung at 7 d.p.c and in the intestine and brain at a later time point. The immune response promoted by the primary infection with the avirulent strain (TgCTBr5) protected the animals from death after challenge with the virulent strains (TgCTBr9 or EGS).

A case of pulmonary toxoplasmosis resembling multiple lung metastases of nasal lymphoma in a cat receiving chemotherapy

An 11-year-old cat presented with nasal discharge and lacrimation and was diagnosed with nasal lymphoma. Although the cat showed favorable progression after undergoing chemotherapy, CT imaging demonstrated enlarged pulmonary nodules caused by Toxoplasma gondii. Following the cessation of chemotherapy, the cat was prescribed clindamycin hydrochloride for toxoplasmosis treatment; however, the cat developed kidney lymphoma and died. No T. gondii organisms were observed in the whole body necropsy specimens. It is known that immunocompromised human patients, including those who undergo chemotherapy, are considered at risk for toxoplasmosis. However, the risk of developing toxoplasmosis in cats undergoing chemotherapy is currently unknown. Findings from this case report suggest that cats with chemotherapy-resistant pulmonary masses might have a T. gondii infection rather than metastatic disease.

Kinetics of parasite distribution after reinfection with genetically distinct strains of Toxoplasma gondii

Recent data shows that prior infection by Toxoplasma gondii does not protect the host from subsequent reinfection even after the development of immunological memory. Although animal models for T. gondii reinfection were proposed after cases of natural human reinfection were described, little is known about the events that occur immediately after challenge. To further understand these events, BALB/c mice were chronically infected with D8 non-virulent strain (genotype ToxoDB#8 BrIII) and challenged with two different virulent strains: EGS (genotype ToxoDB #229) or CH3 strain (genotype ToxoDB #19). Primary infection protected animals from lethal challenge and morbidity was reduced. Reinfection was confirmed by PCR-RFLP, showing differences in the way the parasites spread in challenged animals. Parasites reached the lungs during early infection and a parasitism delay in the intestine was observed in D8+CH3 group. Parasites from challenge strains were not detected in the brain of D8+CH3 and in the intestine and brain of D8+EGS group. Previous infection with D8 strain of T. gondii protected against lethal challenges, but it did not prevent parasite spread to some organs.

Calomys callosus chronically infected by Toxoplasma gondii clonal type II strain and reinfected by Brazilian strains is not able to prevent vertical transmission

Considering that Toxoplasma gondii has shown high genetic diversity in Brazil, the aim of this study was to determine whether Calomys callosus chronically infected by the ME-49 strain might be susceptible to reinfection by these Brazilian strains, including vertical transmission of the parasite. Survival curves were analyzed in non-pregnant females chronically infected with ME-49 and reinfected with the TgChBrUD1 or TgChBrUD2 strain, and vertical transmission was analyzed after reinfection of pregnant females with these same strains. On the 19th day of pregnancy (dop), placentas, uteri, fetuses, liver, spleen, and lung were processed for detection of the parasite. Blood samples were collected for humoral and cellular immune response analyses. All non-pregnant females survived after reinfection and no changes were observed in body weight and morbidity scores. In pregnant females, parasites were detected in the placentas of ME-49 chronically infected females and reinfected females, but were only detected in the fetuses of reinfected females. TgChBrUD2 reinfected females showed more impaired pregnancy outcomes, presenting higher numbers of animals with fetal loss and a higher resorption rate, in parallel with higher levels of pro-inflammatory cytokines and IgG2a subclass antibodies. Vertical transmission resulting from chronic infection of immunocompetent C. callosus is considered a rare event, being attributed instead to either reactivation or reinfection. That is, the pregnancy may be responsible for reactivation of the latent infection or the reinfection may promote T. gondii vertical transmission. Our results clearly demonstrate that, during pregnancy, protection against T. gondii can be breached after reinfection with parasites belonging to different genotypes, particularly when non-clonal strains are involved in this process and in this case the reinfection promoted vertical transmission of both type II and Brazilian T. gondii strains.