In silico analyses and design of chimeric proteins containing epitopes of Bartonella henselae antigens for the control of cat scratch disease

Abstract

Bartonella henselae is a Gram-negative bacterium that causes cat scratch disease (CSD), as well as bacteremia, endocarditis, and other clinical presentations. CSD remains one of the most common infections caused by bacteria in the genus Bartonella, and it is transmitted to humans through a scratch or cat bite. Vaccination and more efficient diagnostic methods would represent a promising and sustainable alternative measure for CSD control in humans and animals. Here, we described the in silico analyses and design of three recombinant chimeric proteins (rC1, rC2, and rC3), for use in the control of CSD. The chimeras were constructed with epitopes identified from the sequences of the GroEL, 17 kDa, P26, BadA, Pap31, OMP 89, and OMP 43, previously described as the most important B. henselae antigens. The rC1, rC2, and rC3 were expressed and purified using a heterologous system based on Escherichia coli and reacted with antibodies present in the sera of humans naturally infected. The chimeric proteins were used to immunize mice using Freund adjuvant, and the humoral immune response was evaluated. Animals immunized with rC1 and rC3 showed a significant IgG antibodies response from the 28th day (P < 0.05), and the animals immunized with the rC2 from the 35th day (P < 0.05) remained until the 56th day of experimentation, with a titer of 1:3200 (P < 0.05), 1:1600 (P < 0.05) and 1:1600 (P < 0.05) from rC1, rC2, and rC3, respectively. Significant production of IgA and IgG1 isotype was detected in animals immunized with rC1 and rC2 proteins. Additionally, analysis using 13 serum samples from naturally infected patients showed that the proteins are recognized by antibodies present in sera, reinforcing the possibility of using these chimeras for CSD control. KEY POINTS: • The recombinant chimeras were expressed in Escherichia coli with 37 kDa (rC1), 35 kDa (rC2), and 38 kDa (rC3). • Animals immunized with rC1, rC2, and rC3 showed significant antibody response. • The chimeras were recognized by the sera of naturally infected patients.

Keywords: Diagnosis; In silico analysis; Recombinant protein; Vaccine.