AUTHOR=Verma Shailendra K. , Batra Lalit , Tuteja Urmil 

TITLE=A Recombinant Trivalent Fusion Protein F1–LcrV–HSP70(II) Augments Humoral and Cellular Immune Responses and Imparts Full Protection against Yersinia pestis

JOURNAL=Frontiers in Microbiology

VOLUME=7

YEAR=2016

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2016.01053

DOI=10.3389/fmicb.2016.01053

ISSN=1664-302X

ABSTRACT=<p>Plague is one of the most dangerous infections in humans caused by <italic>Yersinia pestis</italic>, a Gram-negative bacterium. Despite of an overwhelming research success, no ideal vaccine against plague is available yet. It is well established that F1/LcrV based vaccine requires a strong cellular immune response for complete protection against plague. In our earlier study, we demonstrated that HSP70(II) of <italic>Mycobacterium tuberculosis</italic> modulates the humoral and cellular immunity of F1/LcrV vaccine candidates individually as well as in combinations in a mouse model. Here, we made two recombinant constructs <italic>caf1–lcrV</italic> and <italic>caf1–lcrV–hsp70(II)</italic>. The <italic>caf1</italic> and <italic>lcrV</italic> genes of <italic>Y. pestis</italic> and <italic>hsp70</italic> domain II of <italic>M. tuberculosis</italic> were amplified by polymerase chain reaction. Both the recombinant constructs <italic>caf1–lcrV</italic> and <italic>caf1–lcrV–hsp70(II)</italic> were cloned in pET28a vector and expressed in <italic>Escherichia coli.</italic> The recombinant fusion proteins F1–LcrV and F1–LcrV–HSP70(II) were purified using Ni-NTA columns and formulated with alum to evaluate the humoral and cell mediated immune responses in mice. The protective efficacies of F1–LcrV and F1–LcrV–HSP70(II) were determined following challenge of immunized mice with 100 LD<sub>50</sub> of <italic>Y. pestis</italic> through intraperitoneal route. Significant differences were noticed in the titers of IgG and it’s isotypes, i.e., IgG1, IgG2b, and IgG3 in anti- F1–LcrV–HSP70(II) sera in comparison to anti-F1–LcrV sera. Similarly, significant differences were also noticed in the expression levels of IL-2, IFN-γ and TNF-α in splenocytes of F1–LcrV–HSP(II) immunized mice in comparison to F1–LcrV. Both F1–LcrV and F1–LcrV–HSP70(II) provided 100% protection. Our research findings suggest that F1–LcrV fused with HSP70 domain II of <italic>M. tuberculosis</italic> significantly enhanced the humoral and cellular immune responses in mouse model.</p>