Cell wall fraction of Mycobacterium indicus pranii shows potential Th1 adjuvant activity

Very few adjuvants inducing Thl immune response have been developed and are under clinical investigation. Hence, there is the need to find an adjuvant that elicits strong nil immune response which should be safe when injected in the host along with vaccines. Mycobacterium indicus pranii (MIP), a non-pathogenic vaccine candidate, has shown strong immunomodulatory activity in leprosy/tuberculosis/cancer and in genital warts patients where its administration shifted the host immune response towards Thl type. These findings prompted us to study the components of MIP in detail for their Thl inducing property. Since mycobacterial cell wall is very rich in immunostimulatory components and is known to play important role in immune modulation, we investigated the activity of MIP cell wall using Ovalbumin antigen (OVA) as model antigen. 'Whole cell wall' (CW) and 'aqueous soluble cell wall fractions' (ACW) induced significant Thl immune response while 'cell wall skeleton' (CWS) induced strong Th2 type of immune response. Finally, functional activity of fractions having Thl inducing activity was evaluated in mouse model of melanoma. CW demonstrated significant anti-tumor activity similar to whole MIP. Anti-tumor activity of CW could be correlated with enhanced tumor antigen specific Thl immune response observed in tumor draining lymph nodes.