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Convalescent plasma increases HAI antibody titers

Issue: November 2015

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Hyperimmune intravenous immunoglobulin treatment appeared to significantly increase hemagglutination inhibition antibody titer concentrations in patients with influenza, according to recent findings from the INSIGHT FLU005 pilot study.

“Despite widespread access to antivirals such as oseltamivir and to seasonal vaccines, influenza has been associated with an estimated average of 226,000 excess hospitalizations and 34,000 to 49,000 deaths each year in the United States,” researchers wrote in Clinical Infectious Diseases. “There is a need for more effective treatments for severe, hospitalized cases of influenza.”

In the randomized, double blind study, the researchers evaluated 31 adults with laboratory-confirmed seasonal influenza at one of eight U.S. sites during the 2013-2014 influenza season. The patients were randomly assigned to standard of care (SOC) plus a 0.25 g/kg dose of anti-influenza hyperimmune intravenous immunoglobulin (Emergent Biosolutions; hIVIG; n = 16) or placebo.

Intravenous immunoglobulin (IVIG) infusions were administered over at least 2 hours, and blood samples were collected and measured for hemagglutination inhibition (HAI) antibody titers of influenza A(H1N1) and A(H3N2) and influenza B viruses. The measurements were taken before and after infusion on days 1, 3, 7 and 28; laboratory safety tests were conducted before and after infusion on days 3, 7 and 28.

The researchers found that for IVIG recipients, targeted HAI titer levels were achieved in 100% of patients infected with A/California/07/2009 (H1N1)pdm09 virus, 100% of patients infected with A/Texas/50/2012 (H3N2) virus and 93.8% of those infected with B/Massachusetts/02/2012.

A significant difference in HAI antibody titer levels was observed between the IVIG and placebo groups in patients with A(H1N1)pdm09 during the first 3 days of follow-up. The ratio of geometric mean titers for IVIG vs. placebo was highest 1 hour after infusion (3.9; 95% CI, 2.3-6.7), followed by the first (3.1; 95% CI, 1.8-5.4) and third days (2; 95% CI, 1-4).

Three patients experienced grade 4 adverse events, including one patient who had three grade 4 events and died from advanced cancer unrelated to the study. The two other patients each experienced one grade 4 event of unknown etiology.

“This trial is seeking to evaluate the efficacy and safety of anti-influenza hIVIG in patients hospitalized with severe influenza beginning with the 2014-2015 Northern Hemisphere influenza season,” the researchers wrote. “Due to the ongoing threat of antigenic drift, one major challenge of such a trial will be the need to keep the antibody specificity of the manufactured IVIG product contemporaneous with circulating virus subtypes throughout the projected course of the study over two or more influenza seasons.” – by Jen Byrne

• Reference:
• Davey RT Jr, et al. Clin Infect Dis. 2015;doi:10.1093/infdis/jiv453.

Disclosure: Davey reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.