Serological monitoring of a Toxoplasma infection after hematopoietic stem cell transplantation

Monitoramento sorológico de uma infecção toxoplásmica após transplante de células progenitoras hematopoiéticas

CASE REPORT

Serological monitoring of a Toxoplasma infection after hematopoietic stem cell transplantation

Monitoramento sorológico de uma infecção toxoplásmica após transplante de células progenitoras hematopoiéticas

Cláudio L. Rossi^I; Fernanda S. Nascimento^I; Sílvia de Barros-Mazon^I; Daniela F. Dias^II; Antonio C. Vigorito^II; Cármino A. de Souza^II

^IDepartment of Clinical Pathology, Faculty of Medical Sciences, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil

^IIBone Marrow Transplantation Unit, Hematology and Hemotherapy Center, State University of Campinas (UNICAMP), Campinas, São Paulo, Brazil

^{Correspondence to}

SUMMARY

We report a primary response to Toxoplasma gondii following a hematopoietic stem cell transplantation in a patient with multiple myeloma. The primary response to T. gondii was supported by IgM, IgG and IgA seroconversion. The patient was promptly treated and there were no complications related to toxoplasmosis in the subsequent months.

Keywords: Hematopoietic stem cell transplantation; Toxoplasmosis; Serological diagnosis.

RESUMO

Esse relato de caso descreve uma resposta primária ao Toxoplasma gondii após transplante de células progenitoras hematopoiéticas em paciente com mieloma múltiplo. A resposta primária para o T. gondii foi evidenciada pela soroconversão observada na resposta de anticorpos IgM, IgG e IgA. O paciente foi prontamente tratado e complicações relacionadas à toxoplasmose não foram observadas nos meses subseqüentes.

INTRODUCTION

Toxoplasmosis, a worldwide infection caused by the intracellular parasite Toxoplasma gondii, is generally asymptomatic or is associated with mild, non-specific clinical manifestations in immunocompetent subjects. The parasite can, however, cause serious illness in congenitally infected infants² and in immunocompromised patients^1,4. We report a primary response to T. gondii following a non-myeloablative allogeneic hematopoietic stem cell transplantation in a patient with multiple myeloma.

CASE REPORT

A 53-year-old Brazilian man was diagnosed in December 1998 as having multiple myeloma (stage IIIA according to Durie and Salmon's classification). The patient achieved partial remission after VAD chemotherapy. In April 2000, he underwent an autologous hematopoietic stem cell transplantation (HSCT) (8.94 x 10⁶/kg CD34+ mononuclear cells) under a conditioning regimen of high-dose melphalan (200 mg/m²). There were no important complications in the post-transplantation period and no transfusion was necessary. Neutrophil recovery was observed on day +10. However, because of disease progression, thalidomide (200‑400 mg/day) was started in June 2003. In June 2004, the patient underwent a non-myeloablative allogeneic stem cell transplantation (NST) from an HLA-identical sibling donor and mismatched ABO group (patient O+ and donor B+). Pretransplant serology for toxoplasmosis and cytomegalovirus (CMV) was IgM-negative and IgG-positive. The conditioning regimen included total body irradiation (200 cGy) and fludarabine (90 mg/m²). Graft-versus-host disease (GVHD) prophylaxis with cyclosporine-A and a short course of mycophenolate were initiated. The patient received 8.32 × 10⁸ mononuclear cells/kg and 3.29 × 10⁶ CD34+ cells/kg. Neutrophil recovery was observed on day +5. Complete chimerism was documented by VNTR on days +28, +56, +122, +211 and +909 after NST. The immunosupressor therapy was continued until day +56, when the GVHD prophylaxis was tapered off.

In July 2005 (390 days post-NST), the patient presented fever, myalgia and headache. Serology for syphilis, hepatitis A, B and C and HIV was negative. The serology for CMV was IgM-negative and IgG‑positive, whereas the serology for toxoplasmosis was positive for IgM, IgG and IgA antibodies. The donor's serology for toxoplasmosis was negative for IgM and IgG antibodies. The patient was promptly treated with pyrimethamine, sulfadiazine, and folinic acid, and no complications related to toxoplasmosis have been observed up to now.

The antibody concentrations for several infectious agents, including T. gondii, were measured in recipient serum samples at periodic intervals during follow-up (Table 1). Toxoplasma-specific IgM and IgG antibodies were determined by indirect immunofluorescence (IIF) and enzyme-linked fluorescent assay (ELFA), using the VIDAS^® system (BioMérieux, France). Toxoplasma-specific IgG avidity was also determined by ELFA using the VIDAS system. Anti-T. gondii IgA was measured by enzyme-linked immunosorbent assay (ELISA) using Platelia^TM Toxo IgA kits (Bio-Rad, France). IIF was done as previously described⁹, and titers > 32 were considered positive. ELFA and ELISA were performed according to the manufacturers' instructions. For the VIDAS system, IgM indices > 0.65 and antitoxoplasma IgG titers > 8 international units per milliliter (IU/mL) were considered positive. The IgG avidity test allows specimens to be classified as low (index < 0.2), borderline (0.2 < index < 0.3) or high (> 0.3) avidity. An avidity index > 0.3 is a strong indication of a primary infection dating back more than four months. An index < 0.3 does not allow a recent infection to be differentiated from an old infection. In the ELISA for IgA, serum samples with a sample ratio (sample optical density/optical density for cut-off control serum) > 1 were considered positive.

DISCUSSION

Toxoplasmosis is a rare but serious complication in allogeneic HSCT recipients^3,5,7,8,10. Most cases of Toxoplasma infections occur in seropositive HSCT recipients, suggesting that toxoplasmosis usually results from the reactivation of latent tissue parasites^5,8. In the present case, the seropositive recipient received hematopoietic stem cells from a seronegative donor. The primary response to T. gondii was supported by IgM and IgG seroconversion as shown by IIF, and IgA seroconversion as shown by ELISA. The IgG avidity test also detected low-avidity antibodies in the patient after infection with T. gondii; the low-avidity indices persisted for more than 14 months after the primary infection.

Most cases of toxoplasmosis after HSCT are only diagnosed at autopsy because histological evidence of organ involvement is rarely obtained before death⁶. The early detection of T. gondii DNA in body fluids by PCR methods has been considered an important tool for monitoring Toxoplasma infection following HSCT^5,6. A recent study has shown the importance of monitoring toxoplasmosis after HSCT with biological tests that combine PCR and serological techniques³. This case stresses the importance of detecting anti-T. gondii antibodies in donors and recipients before transplantation, and of serologically monitoring the recipient during long-term follow-up.

Received: 6 May 2010

Accepted: 24 June 2010

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Publication Dates

• Publication in this collection
  25 Aug 2010
• Date of issue
  Aug 2010

History

• Accepted
  24 June 2010
• Received
  06 May 2010