Intravenous immunoglobulin (IVIg). IVIg is a blood product prepared from the serum of more than 1,000 donors that contains a broad range of antibodies.  Some of these antibodies target a patient’s autoantibodies and neutralize them, along with other pro-inflammatory aspects of the immune system.   It contains the antibody IgG.  What is known about IgG is that it helps control the immune system.  AE is caused by overactive or rogue antibodies in your immune system. IVIg is part of the first-line of treatment options for Autoimmune Encephalitis, along with steroids and plasmapheresis that try to control these antibodies from attacking.

Once you receive an IVIG infusion treatment, most physicians believe that it sends a signal to slow down the immune system from making more antibodies.  It may also provide antibodies you are lacking.  It is also thought that it creates a decoy target for the overactive immune system to attack.  Resulting in diverting the normal immune system from the body’s normal organs.  It may also work by binding the abnormal antibody and stimulating its’ removal.  Adding healthy antibodies into your system can also boost your immune system by performing the same function as your body’s native antibodies.

Standard dosage

IVIg is generally given at a dose of 0.4 g/kg daily for 3–5 days followed by 0.4 g/kg every week for 5 weeks,

and then the patient should be re-evaluated for assessment of neurological improvement. Local availability of different IVIg products may vary.

Each dose is usually administered in an infusion center, although some insurance policies will cover home infusions, over 2–4 hours with monitoring for infusion reactions during that time. The patient should be pre-medicated with acetaminophen 650 mg and diphenhydramine 25–50 mg by mouth.

Contraindications

Hypersensitivity to IVIg, including patients with IgA deficiency with anti-IgA antibodies, and history of hypersensitivity.

Main drug interactions

IVIg may diminish the efficacy of live vaccines. Main side-effects Selective IgA deficiency is a relative contraindication to IVIg therapy. Checking total immunoglobulin (Ig) and Ig isotypes to exclude selective IgA deficiency prior to commencing IVIg therapy is generally recommended, though anaphylaxis caused by IgE antibodies to IgA is rare [23]. Patients with B cell deficiencies are most at risk for true anaphylaxis caused by IgE antibodies to IgA. A prior allergic reaction to IVIg products is an absolute contraindication to IVIg therapy. No other specific blood testing is required prior to starting IVIg. However, IVIg should be used with caution in patients with renal impairment or a history of thrombotic events.

Commonly encountered and/or serious side effects include headache, infusion reactions, autoimmune hemolytic anemia, aseptic meningitis, deep venous thromboses, pulmonary emboli, acute tubular necrosis, renal failure and pulmonary edema.

Special Points

After the prescribed course of IVIg has been completed, the patient should be reassessed by a neurologist within 2 weeks to re-evaluate subjective and objective parameters of neurological function, prior to the waning of the immunotherapeutic effects of IVIg (elimination half-life of IVIg is 14–24 days).

If objective evidence of clinical improvement is documented along

with improvement in symptoms, further treatments with IVIg are generally recommended. If the patient remains in remission from the neurological symptoms, the treatments are usually tapered from an infusion every other week to an infusion every third week, followed by monthly treatments, and then discontinuing therapy. This tapering is often done in conjunction with initiation of an oral immunosuppressant, such as azathioprine or mycophenolate mofetil, with the goal of overlapping the IVIg and oral immunosuppressive therapy for 3–6 months, followed by discontinuation of IVIg. Longer-term immunosuppression with oral agents is only undertaken in those patients with clear objective evidence of neurological improvement after a trial of IVIg.

If no objective improvements are noted after the 12-week trial, then IVIg is discontinued at that point.

References

Andrew Mckeon, MD, Current Treatment Options in Neurology, Immunotherapeutics for Autoimmune Encephalopaties

Shin, Y.-W. et al. Treatment strategies for autoimmune encephalitis. Ther. Adv.
Neurol. Disord. 11, 1–19 (2018).