Heat shock proteins enriched-promastigotes of Leishmania major inducing Th2 immune response in BALB/c mice

In silico designing of a novel polyvalent multi-subunit peptide vaccine leveraging cross-immunity against human visceral and cutaneous leishmaniasis: an immunoinformatics-based approach

CONTEXT

Leishmaniasis is a group of vector-borne infectious diseases caused by over 20 pathogenic Leishmania species that are endemic in many tropical and subtropical countries. The emergence of drug-resistant strains, the adverse side effects of anti-Leishmania drugs, and the absence of a preventative vaccination strategy threaten the sensitive population. Recently, many groups of researchers have exploited the field of reverse vaccinology to develop vaccines, focusing chiefly on inducing immunity against either visceral or cutaneous leishmaniasis.

METHODS

This present work involves retrieving twelve experimentally validated leishmanial antigenic protein sequences from the UniProt database, followed by their antigenicity profiling employing ANTIGENpro and Vaxijen 2.0 servers. MHC-binding epitopes for the same were predicted using both NetCTL 1.2 and SYFPEITHI servers, while epitopes for B cell were computed using ABCpred and BepiPred 2.0 servers. The screened epitopes with significantly higher scores were utilized for designing the vaccine construct with appropriate linkers and natural adjuvant. The secondary and tertiary structures of the synthetic peptide were determined by conditional random fields, shallow neural networks, and profile-profile threading alignment with iterative structure assembly simulations, respectively. The 3-D vaccine model was validated through CASP10-tested refinement and the MolProbity web server. Molecular docking and multi-scale normal mode analysis simulation were performed to analyze the best vaccine-TLR complex. Finally, computational immune simulation findings revealed promising cellular and humoral immune responses, suggesting that the engineered chimeric peptide is a potential broad-spectrum vaccine against visceral and cutaneous leishmaniasis.

Comparative analysis of the anticoagulant activities and immunogenicity of HSC70 and HSC70TKD of Haemaphysalis flava

BACKGROUND

Haemaphysalis flava is a hematophagous ectoparasite that acquires the nutrition needed for development and reproduction by sucking blood and digesting the blood meal. During blood-sucking and blood-meal digestion, the prevention of blood coagulation is important for this tick. Previous studies have shown that heat shock cognate 70 (HSC70) protein has certain anticoagulant activities, but its immunogenicity remains unclear. Also, whether the mutation of individual bases of the TKD-like peptide of HSC70 through the overlap extension method can change its anticoagulant activities and immunogenicity remains to be investigated.

METHODS

The gene encoding the HSC70 protein was cloned from a complementary DNA library synthesized from H. flava. The coding gene of the TKD-like peptide of HSC70 was mutated into a TKD peptide coding gene (HSC70^TKD) using the overlap extension method. Escherichia coli prokaryotic expression plasmids were constructed to obtain the recombinant proteins of HSC70 (rHSC70) and HSC70^TKD (rHSC70^TKD). The purified rHSC70 and rHSC70^TKD were evaluated at different concentrations for anticoagulant activities using four in vitro clotting assays. Emulsifying recombinant proteins with complete and incomplete Freund's adjuvants were subcutaneously immunized in Sprague Dawley rats. The serum antibody titers and serum concentrations of interferon-gamma (IFN-γ) and interleukin-4 (IL-4) were detected using an indirect enzyme-linked immunosorbent assay to assess the immunogenicity of rHSC70 and rHSC70^TKD.

RESULTS

The open reading frame of HSC70 was successfully amplified and found to have a length of 1958 bp. The gene encoding the TKD-like peptide of HSC70 was artificially mutated, with the 1373-position adenine (A) of the original sequence mutated into guanine (G), the 1385-position cytosine (C) mutated into G and the 1386-position G mutated into C. rHSC70 and rHSC70^TKD that fused with His-tag were obtained using the expression plasmids pET-28a-HSC70 and pET-28a-HSC70^TKD, respectively. rHSC70 and rHSC70^TKD prolonged the thrombin time (TT) and reduced the fibrinogen (FIB) content in the plasma, but did not affect the prothrombin time (PT) or activated partial thromboplastin time (APTT) when compared to the negative control. Interestingly, the ability of rHSC70^TKD to prolong the TT and reduce the FIB content in the plasma was better than that of rHSC70. The specific antibody titers of both rHSC70 and rHSC70^TKD in rat serum reached 1:124,000 14 days after the third immunization. The serum concentration of IFN-γ in the rHSC70^TKD group was higher than that in the rHSC70 group. The rHSC70 group has the highest serum concentration of IL-4, and the serum concentration of IL-4 in the rHSC70^TKD group was higher than that in the negative group.

CONCLUSIONS

rHSC70 and rHSC70^TKD exhibited anticoagulant activities by prolonging the TT and reducing the FIB content in vitro. rHSC70^TKD had better anticoagulant activities than rHSC70. Both rHSC70 and rHSC70^TKD had good immunogenicity and induced humoral and cellular immunity.

Virulence factor RNA transcript expression in the Leishmania Viannia subgenus: influence of species, isolate source, and Leishmania RNA virus-1

BACKGROUND

Leishmania RNA virus-1 (LRV1) is a double-stranded RNA virus identified in 20-25% of Viannia-species endemic to Latin America, and is believed to accelerate cutaneous to mucosal leishmaniasis over time. Our objective was to quantify known virulence factor (VF) RNA transcript expression according to LRV1 status, causative species, and isolate source.

METHODS

Eight cultured isolates of Leishmania were used, four of which were LRV1-positive (Leishmania Viannia braziliensis [n = 1], L. (V.) guyanensis [n = 1], L. (V.) panamensis [n = 2]), and four were LRV1-negative (L. (V.) panamensis [n = 3], L. (V.) braziliensis [n = 1]). Promastigotes were inoculated into macrophage cultures, and harvested at 24 and 48 h. RNA transcript expression of hsp23, hsp70, hsp90, hsp100, mpi, cpb, and gp63 were quantified by qPCR.

RESULTS

RNA transcript expression of hsp100 (p = 0.012), cpb (p = 0.016), and mpi (p = 0.022) showed significant increases from baseline pure culture expression to 24- and 48-h post-macrophage infection, whereas hsp70 (p = 0.004) was significantly decreased. A trend toward increased transcript expression of hsp100 at baseline in isolates of L. (V.) panamensis was noted. Pooled VF RNA transcript expression by L. (V.) panamensis isolates was lower than that of L. (V.) braziliensis and L. (V.) guyananesis at 24 h (p = 0.03). VF RNA transcript expression did not differ by LRV1 status, or source of cultured isolate at baseline, 24, or 48 h; however, a trend toward increased VF RNA transcript expression of 2.71- and 1.93-fold change of mpi (p = 0.11) and hsp90 (p = 0.11), respectively, in LRV1 negative isolates was noted. Similarly, a trend toward lower levels of overall VF RNA transcript expression in clinical isolates (1.15-fold change) compared to ATCC® strains at 24 h was noted (p = 0.07).

CONCLUSIONS

Our findings suggest that known VF RNA transcript expression may be affected by the process of macrophage infection. We were unable to demonstrate definitively that LRV-1 presence affected VF RNA transcript expression in the species and isolates studied. L. (V.) guyanensis and L. (V.) braziliensis demonstrated higher pooled VF RNA transcript expression than L. (V.) panamensis; however, further analyses of protein expression to corroborate this finding are warranted.