72:
Correlation Of B Cell Number With Typhi Vi IgG Antibodies In Primary Immunodeficient Patients
Saturday, March 3, 2018
South Hall A2 (Convention Center)
Antony R. Parker, Suranjith L. Seneviratne, MB BS MD MRCP, N. Rajiva De Silva, Jeevani Kumarage, Vijitha Senatane, Amitha Fernando, Kirthi Gunasekara, Bandu Gunasena, Nishantha Padmalal Gurugama, Sudath Peiris
RATIONALE:

The response to the polysaccharide vaccine Typhim Vi® is an essential aid to investigate adaptive immune system disorders. Antigenic stimulation of B-cells and B-cell expansion is responsible for the production of antibodies. We sought to understand the correlation between the total B-cell count and antibody production in response to Typhim Vi® in an immunocompromised population.

METHODS:

Samples from primary immunodeficiency patients (PID, n=15) and the control population (n=32) who received Typhim Vi ®, were obtained from the Medical Research Institute, Colombo, Sri Lanka. B-cell numbers were measured by flow cytometry and Typhi Vi IgG using the VaccZyme Salmonella Typhi Vi IgG ELISA (The Binding Site Group, Birmingham, UK). Lower limits of normal reference for B cells was 133 cells /mL and for Typhim Vi ® post vaccination 60 U/mL and fold increase 4.8.

RESULTS:

The B-cell count was lower in individuals with PID (median 305 cells/mL, range 90-1127 vs median 429 cells/mL, range 144-2061; p=0.04), however in ~60% of patients the B-cell count and production of Typhim Vi ® antibodies were above the normal cut offs. In the remaining PID population, the B-cell response was measureable but they did not produce an immune response to Typhim Vi ®. The B-cell numbers were slightly different between responders and non-responders but did not achieve significance.

CONCLUSIONS:

Total number of B-cells cannot adequately describe PID patients. Likewise not all PID patients mount a response to Typhim Vi ® and therefore measurement of many parameters is required to investigate these complex disorders.