Avoidance of Toxoplasma gondii transmission from a recently infected donor to the recipient of hematopoietic stem cell transplantation

Guidelines for the management of Toxoplasma gondii infection and disease in patients with haematological malignancies and after haematopoietic stem-cell transplantation: guidelines from the 9th European Conference on Infections in Leukaemia, 2022

Patients with haematological malignancies might develop life-threatening toxoplasmosis, especially after allogeneic haematopoietic stem-cell transplantation (HSCT). Reactivation of latent cysts is the primary mechanism of toxoplasmosis following HSCT; hence, patients at high risk are those who were seropositive before transplantation. The lack of trimethoprim-sulfamethoxazole prophylaxis and various immune status parameters of the patient are other associated risk factors. The mortality of toxoplasma disease-eg, with organ involvement-can be particularly high in this setting. We have developed guidelines for managing toxoplasmosis in haematology patients, through a literature review and consultation with experts. In allogeneic HSCT recipients seropositive for Toxoplasma gondii before transplant, because T gondii infection mostly precedes toxoplasma disease, we propose weekly blood screening by use of quantitative PCR (qPCR) to identify infection early as a pre-emptive strategy. As trimethoprim-sulfamethoxazole prophylaxis might fail, prophylaxis and qPCR screening should be combined. However, PCR in blood can be negative even in toxoplasma disease. The duration of prophylaxis should be a least 6 months and extended during treatment-induced immunosuppression or severe CD4 lymphopenia. If a positive qPCR test occurs, treatment with trimethoprim-sulfamethoxazole, pyrimethamine-sulfadiazine, or pyrimethamine-clindamycin should be started, and a new sample taken. If the second qPCR test is negative, clinical judgement is recommended to either continue or stop therapy and restart prophylaxis. Therapy must be continued until a minimum of two negative PCRs for infection, or for at least 6 weeks for disease. The pre-emptive approach is not indicated in seronegative HSCT recipients, after autologous transplantation, or in non-transplant haematology patients, but PCR should be performed with a high level of clinical suspicion.

Parasitic infections in hematopoietic stem cell transplant recipients

INTRODUCTION

Hematopoietic stem cell transplantation (HSCT) is a vital treatment for various hematological disorders. However, HSCT recipients face increased risks of infectious complications due to immunosuppression. Parasitic infections are a significant concern in this vulnerable population and can lead to substantial morbidity and mortality. This review examines parasitic infections in HSCT recipients, focusing on major infections affecting different organ systems, including intestinal parasites (Giardia spp., Entamoeba histolytica, and Cryptosporidium spp.), hematologic parasites (Plasmodium spp. and Babesia spp.), and tissue/visceral parasites (Toxoplasma gondii, Leishmania spp., and Trypanosoma cruzi).

METHODS

A systematic search of relevant literature was conducted and included studies up to August 2023. Databases included PubMed, Google Scholar, were queried using specific keywords related to parasitic infections in HSCT patients. The epidemiology, risk factors, clinical presentation, diagnostic methods, and treatment approaches for each infection were evaluated.

RESULTS AND CONCLUSION

Knowing the epidemiology, risk factors, and clinical presentations are crucial for timely intervention and successful management. By emphasizing early detection, effective therapies, and the unique challenges posed by each of these infections, this review highlights the importance of tailored strategies for HSCT recipients. Future research can further refine management protocols to enhance care and outcomes for these patients.

Toxoplasmosis in Pediatric Hematopoietic Stem Cell Transplantation Patients

Infection due to the protozoa Toxoplasma gondii can be life-threatening in hematopoietic stem cell transplantation (HSCT) recipients. Most cases of toxoplasmosis in HSCT recipients result from reactivation of latent infection in individuals who were Toxoplasma-seropositive before transplantation and did not receive appropriate prophylaxis. Pretransplantation screening with Toxoplasma IgG and IgM antibodies is suggested for all allogeneic HSCT recipients and their donors and all autologous HSCT recipients. Prevention of toxoplasmosis in T. gondii-seropositive HSCT recipients requires primary prophylaxis, preemptive screening, or both. Trimethoprim-sulfamethoxazole (TMP-SMX) is the preferred agent for Toxoplasma prophylaxis and should be continued for 6 months or until the patient is no longer receiving immunosuppression, whichever is longer, assuming that immune reconstitution has occurred. Preemptive weekly screening with whole blood Toxoplasma PCR should be considered for seropositive HSCT recipients if prophylaxis cannot be given or if prophylaxis other than TMP-SMX is used. The signs, symptoms, and radiographic findings of toxoplasmosis in HSCT recipients can be nonspecific, and the diagnosis requires a high degree of suspicion. Common presentations include fever, encephalopathy with mental status changes or seizures, and pneumonia. A Toxoplasma PCR analysis from whole blood (and other body fluids/tissues according to clinical symptoms) should be obtained in patients in whom there is a concern for toxoplasmosis. Treatment with oral pyrimethamine, sulfadiazine, and leucovorin for at least 6 weeks is the first-line therapy and should be followed by secondary prophylaxis. In this article, we review the published literature regarding the epidemiology, clinical presentation, treatment, and prevention of toxoplasmosis in HSCT recipients.

Allogeneic hematopoietic stem cell transplant recipients and parasitic diseases: A review of the literature of clinical cases and perspectives to screen and follow-up active and latent chronic infections

BACKGROUND

Allogeneic hematopoietic stem cell transplant (HSCT) recipients are at substantial risk for a variety of infections depending upon numerous factors, such as degree of immunosuppression, host factors, and period after transplantation. Bacterial, fungal, viral, as well as parasitic infections can occur with high morbidity and mortality.

OBJECTIVES

The aim of this study was to evaluate the magnitude of the occurrence of parasitic infections in allogeneic HSCT recipients. Modalities of transmission, methods of diagnosis, treatment, donor and recipient pre-transplant screening and prevention measures of the most serious parasitic infections have also been discussed.

MATERIALS AND METHODS

We systematically reviewed literature records on post-transplant (allogeneic HSCT) parasitic infections, identified through PubMed database searching, using no language or time restrictions. Search was concluded on December 31, 2015. In the present review, we only discussed post-transplant parasitic infections in allogeneic HSCT. Only exclusion criteria were absence of sufficient information on the transmission of parasitic infection to the recipient. Autologous HSCT recipients have not been included because of the absence of a proper allogeneic transplantation even in presence of blood or blood product transfusions. The methods and findings of the present review have been reported based on the preferred reporting items for systematic reviews and meta-analysis checklist (PRISMA).

RESULTS

Regarding allogeneic HSCT recipients, from data published in the literature the real burden of parasitic infections cannot be really estimated. Nevertheless, a positive trend on publication number exists, probably because of more than one reason: (i) the increasing number of patients transplanted and then treated with immunosuppressive agents, (ii) the "population shift" resulting from immigration and travels to endemic areas, and (iii) the increasing of attention for diagnosis/notification/publication of cases.

CONCLUSIONS

Considering parasitic infections as emerging and potentially serious in their evolution, additional strategies for the prevention, careful screening and follow-up, with a high level of suspicion, identification, and preemptive therapy are necessary in transplant recipients.

PERSPECTIVES

The Authors' viewpoint in the perspective to screen and follow-up active and latent chronic parasitosis in stem cells donors and recipients: a proposal for a flow chart.

Toxoplasma prophylaxis in haematopoietic cell transplant recipients: a review of the literature and recommendations

PURPOSE OF REVIEW

Toxoplasmosis in haematopoietic cell transplant (HCT) recipients is associated with high morbidity and mortality rates. Prophylaxis following HCT is recommended for high-risk pre-HCT toxoplasma-seropositive (pre-HCTSP) recipients. However, there is no agreement or consistency among programmes on whether to adopt prophylaxis or not, or if used, on the chosen antitoxoplasma prophylactic regimen. This review discusses the role of prophylaxis, and preemptive treatment, for toxoplasmosis in the setting of HCT.

RECENT FINDINGS

Approximately two-thirds of toxoplasmosis cases following HCT are reported in allogeneic pre-HCTSP (allo pre-HCTSP) patients. This finding confirms a major role of reactivation of latent infection in the pathogenesis of toxoplasmosis in this patient population. Toxoplasma disease-related mortality in allo pre-HCTSP patients was reported at 62%, but it can be significantly decreased with early detection and treatment of toxoplasma infection. There are no randomized trials comparing the efficacy of different prophylactic agents to prevent toxoplasmosis after HCT. Several observational studies have demonstrated the efficacy of trimethoprim-sulfamethoxazole (TMP/SMX) in decreasing the incidence of toxoplasmosis following HCT. There is limited information regarding efficacy of other prophylactic agents. Preemptive treatment using routine blood PCR monitoring seems to be beneficial in detecting infection early and preventing disease in several observational studies and has been adopted for allo pre-HCTSP HCT patients when universal prophylaxis is not possible.

SUMMARY

Universal prophylaxis with TMP/SMX in allo pre-HCTSP patients should be implemented by all transplant programmes. Preemptive treatment with routine blood PCR monitoring is an option if prophylaxis cannot be used.

Determining Toxoplasma high-risk autologous and allogeneic hematopoietic stem cell transplantation patients by systematic pre-transplant PCR screening of stem cell originated buffy coat

The diagnosis of Toxoplasma infection or disease in hematopoietic stem cell transplantation (HSCT) patients is achieved mainly by PCR screening; however screening did not find wide field of use in practice due to costly expenditures of PCR. This study aimed to determine patients at high risk of Toxoplasma infection or disease before transplantation by stem cell originated buffy coat PCR and subsequently to screen them. Buffy coats collected from 12 autologous and 18 allogeneic HSCT patients' donors were investigated by PCR before transplantation. After transplantation, blood and sera collected at fixed time intervals were screened by two PCR methods and serological assays. Screening results first time assessed a toxoplasmosis incidence level as 25% in autologous HSCT patients and increased incidence level in allogeneic HSCT patients to 22%. Importantly, buffy coat PCR was first time performed before transplantation, to determine the risk of toxoplasmosis. Buffy coat PCR results showed that four patients were at high risk of toxoplasmosis before transplantation. After transplantation, these patients experienced toxoplasmosis. In conclusion, for the determination of patients at risk of toxoplasmosis, clinicians should consider buffy coat PCR in combination with serology before transplantation. After transplantation, PCR screening can be initiated in high risk patients upon clinical suspicion.

Prevention of toxoplasmosis in transplant patients

Toxoplasmosis is a life-threatening opportunistic infection that affects haematopoietic stem cell transplant (HSCT) and solid organ transplant (SOT) recipients. Its incidence in these patients is closely related to the prevalence of toxoplasmosis in the general population, which is high in Europe. In SOT recipients, toxoplasmosis results mainly from transmission of the parasite with the transplanted organ from a Toxoplasma-seropositive donor to a Toxoplasma-seronegative recipient. This risk is high in cases of transplantation of organs that are recognized sites of encystation of the parasite, e.g. the heart, and is markedly lower in other SOT recipients. Clinical symptoms usually occur within the first 3 months after transplantation, sometimes as early as 2 weeks post transplant, and involve febrile myocarditis, encephalitis or pneumonitis. In HSCT recipients, the major risk of toxoplasmosis results from the reactivation of a pre-transplant latent infection in seropositive recipients. The median point of disease onset is estimated at 2 months post transplant, with <10% of cases occurring before 30 days and 15-20% later than day 100. Toxoplasmosis usually manifests as encephalitis or pneumonitis, and frequently disseminates with multiple organ involvement. Diagnosis of toxoplasmosis is based on the demonstration of parasites or parasitic DNA in blood, bone marrow, cerebrospinal fluid, bronchoalveolar lavage fluid or biopsy specimens, and serological tests do not often contribute to the diagnosis. For prevention of toxoplasmosis, serological screening of donors and recipients before transplantation allows the identification of patients at higher risk of toxoplasmosis, i.e. seropositive HSCT recipients and mismatched (seropositive donor/seronegative recipients) SOT recipients. Preventing toxoplasmosis disease in those patients presently relies on prophylaxis via prescription of co-trimoxazole.