Immunoadjuvant and Humoral Immune Responses of Garlic (Allium sativum L.) Lectins upon Systemic and Mucosal Administration in BALB/c Mice

Dietary food components have the ability to affect immune function; following absorption,
specifically orally ingested dietary food containing lectins can systemically modulate the immune
cells and affect the response to self- and co-administered food antigens. The mannose-binding
lectins from garlic (Allium sativum agglutinins; ASAs) were identified as immunodulatory proteins
in vitro. The objective of the present study was to assess the immunogenicity and adjuvanticity
of garlic agglutinins and to evaluate whether they have adjuvant properties in vivo for a weak
antigen ovalbumin (OVA). Garlic lectins (ASA I and ASA II) were administered by intranasal (50 days
duration) and intradermal (14 days duration) routes, and the anti-lectin and anti-OVA immune
(IgG) responses in the control and test groups of the BALB/c mice were assessed for humoral
immunogenicity. Lectins, co-administered with OVA, were examined for lectin-induced anti-OVA
IgG response to assess their adjuvant properties. The splenic and thymic indices were evaluated as
a measure of immunomodulatory functions. Intradermal administration of ASA I and ASA II had
showed a four-fold and two-fold increase in anti-lectin IgG response, respectively, vs. the control
on day 14. In the intranasal route, the increases were 3-fold and 2.4-fold for ASA I and ASA II,
respectively, on day 50. No decrease in the body weights of animals was noticed; the increases in
the spleen and thymus weights, as well as their indices, were significant in the lectin groups. In
the adjuvanticity study by intranasal administration, ASA I co-administered with ovalbumin (OVA)
induced a remarkable increase in anti-OVA IgG response (~six-fold; p < 0.001) compared to the
control, and ASA II induced a four-fold increase vs. the control on day 50. The results indicated that ASA was a potent immunogen which induced mucosal immunogenicity to the antigens that were
administered intranasally in BALB/c mice. The observations made of the in vivo study indicate that
ASA I has the potential use as an oral and mucosal adjuvant to deliver candidate weak antigens.
Further clinical studies in humans are required to confirm its applicability.