Domain II of Mycobacterium tuberculosis (Mtb) heat shock protein 70 (HSP70), spanning amino acid residues 161–370, was covalently linked to a recently described synthetic dengue virus antigen to study the influence of the former on the immunogenicity of the latter. Using an enzyme-linked immunosorbent assay, dengue antigen-specific antibody titers elicited by the fusion protein in Balb/c mice were an order of magnitude higher than those elicited by either the synthetic dengue antigen alone or a physical mixture of the dengue antigen plus Mtb HSP70 domain II protein. Our data demonstrate that (i) Mtb HSP70 domain II is capable of potentiating B-cell response and (ii) it should be covalently linked to the target antigen to do so.