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Identification of an epitope of a recombinant Onchocerca volvulus protein that induces corneal pathology
E Pearlman1, E Diaconu, F E Hazlett
1Department of Medicine, Case Western Reserve University, Cleveland, OH, USA.
Abstract:
Ocular onchocerciasis results from immune recognition of parasite proteins released into the eye by degenerating microfilariae. Previous studies have shown that pathology similar to human ocular onchocerciasis can be induced in sensitized mice by intracorneal injection with Onchocerca volvulus antigens. In the current study, we used this murine model to map the segments of O. volvulus protein disulfide isomerase (OvPDI) associated with the development of corneal pathology. Subclones of OvPDI were constructed encompassing one or more predicted T cell epitopes. Keratitis was induced in BALB/c mice after subcutaneous immunizations with OvPDI, followed by intracorneal challenge of OvPDI constructs. Truncated OvPDI proteins containing amino acids 450-481 of OvPDI were found to induce keratitis, whereas constructs that did not include this region did not induce corneal pathology. Consistent with this observation, two peptides derived from the 450-481 region stimulated T cell proliferation to a greater degree than control carrier protein. DNA sequence analysis of cDNAs encoding OvPDI from blinding and non-blinding strains of O. volvulus indicated no differences in the primary amino acid sequence of the 450-481 domain. Immunization of animals with OvPDI induced antibodies recognizing a 55 kDa host protein, identical to the predicted molecular weight of the mouse PDI homologue. Together, these data implicate specific antigenic epitopes of OvPDI in the development of O. volvulus mediated corneal pathology.
Insights
Immune responses to Onchocerca volvulus protein disulfide isomerase (OvPDI) cause ocular onchocerciasis. Specific OvPDI segments, particularly amino acids 450-481, are critical for inducing experimental keratitis in a mouse model.
Area of Science:
- Immunology
- Parasitology
- Ophthalmology
Background:
- Ocular onchocerciasis is an eye disease caused by immune responses to Onchocerca volvulus parasite proteins.
- A murine model exists where intracorneal injection of O. volvulus antigens can mimic human ocular pathology.
Purpose of the Study:
- To identify specific segments of O. volvulus protein disulfide isomerase (OvPDI) responsible for inducing corneal pathology in a mouse model.
- To investigate the role of T cell epitopes within OvPDI in the development of keratitis.
Main Methods:
- Construction of OvPDI subclones containing predicted T cell epitopes.
- Induction of keratitis in BALB/c mice via immunization with OvPDI and subsequent intracorneal challenge.
- Analysis of T cell proliferation and antibody production in response to OvPDI fragments.
Main Results:
- Truncated OvPDI proteins including amino acids 450-481 induced keratitis, while other regions did not.
- Peptides from the 450-481 region significantly stimulated T cell proliferation.
- No primary amino acid sequence differences in the 450-481 domain were found between blinding and non-blinding O. volvulus strains.
Conclusions:
- Specific antigenic epitopes within the OvPDI 450-481 region are implicated in mediating O. volvulus-induced corneal pathology.
- The findings suggest a targeted approach for understanding and potentially treating ocular onchocerciasis.