# Absence of Anti-Babesia microti antibody in commercial intravenous immunoglobulin (IVIG)

## TL;DR

Commercial IVIG does not contain antibodies against Babesia microti, suggesting it may not help treat babesiosis.

## Contribution

This study is the first to test commercial IVIG for anti-Babesia microti antibodies and finds them absent.

## Key findings

- No commercial IVIG samples tested positive for anti-Babesia microti antibodies using IFA or ELISA.
- Commercial IVIG may not provide therapeutic benefit for babesiosis patients.
- Patients with impaired antibody production may not benefit from IVIG as an adjunct therapy.

## Abstract

Babesiosis is a worldwide emerging protozoan infection that is associated with a spectrum of disease severity from asymptomatic infection to severe organ damage and death. While effective treatment strategies are available, some immunocompromised patients experience severe acute and prolonged/relapsing illness due in part to an impaired host antibody response. Intravenous immunoglobulin (IVIG) has been used as an adjunctive therapy in some immunocompromised babesiosis patients, but its therapeutic effect is uncertain. We evaluated the presence of Babesia microti antibodies in commercial samples of IVIG.

The presence of B. microti antibodies in commercial samples of IVIG were tested using an immunofluorescence assay. A subset of samples was then tested for B. microti antibodies using an enzyme linked immunosorbent assay.

Out of 57 commercial IVIG samples tested using IFA, and 52 samples tested using ELISA, none were positive for B. microti antibodies.

Commercially available IVIG may not be of therapeutic benefit for babesiosis patients. Additional sampling of IVIG for B. microti antibody and a clinical trial of babesiosis patients given IVIG compared with controls would provide further insight into the use of IVIG for the treatment of babesiosis.

Human babesiosis is usually a mild to moderate illness that clears with a standard course of atovaquone and azithromycin. The disease is often severe in immunocompromised patients, including those over 50 years of age, those with asplenia, malignancy, HIV/AIDS, or on immunosuppressive therapy. Patients with multiple immunosuppressive conditions that usually result in low or absent antibody production may experience severe acute disease followed by persistent relapsing disease that can last for months or even years. Intravenous immunoglobulin (IVIG) has been used as adjunct therapy in patients with severe babesiosis, although controlled therapeutic trials have not been carried out. This prompted us to evaluate Babesia microti antibody concentrations in IVIG samples from different commercial sources. We tested commercially available IVIG for antibodies against B. microti using IFA and ELISA assays. None of the IVIG samples contained detectable antibody against B. microti. Our results suggest that commercially available IVIG may be of limited therapeutic benefit for babesiosis patients.