Dataset Information

Identification of Cytauxzoon felis antigens via protein microarray and assessment of expression library immunization against cytauxzoonosis.

ABSTRACT:

Background

Cytauxzoonosis is a disease of felids in North America caused by the tick-transmitted apicomplexan parasite Cytauxzoon felis. Cytauxzoonosis is particularly virulent for domestic cats, but no vaccine currently exists. The parasite cannot be cultivated in vitro, presenting a significant limitation for vaccine development.

Methods

Recent sequencing of the C. felis genome has identified over 4300 putative protein-encoding genes. From this pool we constructed a protein microarray containing 673 putative C. felis proteins. This microarray was probed with sera from C. felis-infected and naïve cats to identify differentially reactive antigens which were incorporated into two expression library vaccines, one polyvalent and one monovalent. We assessed the efficacy of these vaccines to prevent of infection and/or disease in a tick-challenge model.

Results

Probing of the protein microarray resulted in identification of 30 differentially reactive C. felis antigens that were incorporated into the two expression library vaccines. However, expression library immunization failed to prevent infection or disease in cats challenged with C. felis.

Conclusions

Protein microarray facilitated high-throughput identification of novel antigens, substantially increasing the pool of characterized C. felis antigens. These antigens should be considered for development of C. felis vaccines, diagnostics, and therapeutics.

SUBMITTER: Schreeg ME

PROVIDER: S-EPMC6310948 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Cytauxzoon felis is a tick-borne hemoprotozoan parasite that causes life-threatening disease in domestic cats in the United States. Currently, the platforms for C. felis research are limited to natural or experimental infection of domestic cats. This study aims to develop an alternative model by infecting Amblyomma americanum ticks with C. felis via direct injection. Amblyomma americanum adults were injected with C. felis-infected feline erythrocytes through two routes: directly into the digestive tract through the anal pore (IA injection), or percutaneously into the tick hemocoel (IH injection). RNAscope® in situ hybridization (ISH) was used to visualize the parasites within the ticks at different time points after injection. Four months after injection, ticks were divided into 3 infestation groups based on injection methods and inoculum type and fed on 3 naïve cats to assess the ticks' ability to transmit C. felis. Prior to the transmission challenge, selected ticks from each infestation group were tested for C. felis RNA via reverse transcription-PCR (RT-PCR). In both IA- and IH-injected ticks, ISH signals were observed in ticks up to 3 weeks after injection. The number of hybridization signals notably decreased over time, and no signals were detected by 4 months after injection. Prior to the transmission challenge, 37-57% of the sampled ticks were positive for C. felis RNA via RT-PCR. While the majority of injected ticks successfully attached and fed to repletion on all 3 cats during the transmission challenge, none of the cats became infected with C. felis. These results suggest that injected C. felis remained alive in ticks but was unable to progress to infective sporozoites after injection. It is unclear why this infection technique had been successful for other closely related tick-borne hemoprotozoa and not for C. felis. This outcome may be associated with uncharacterized differences in the C. felis life cycle, the lack of the feeding or molting in our model or absence of gametocytes in the inoculum. Nonetheless, our study demonstrated the potential of using ticks as an alternative model to study C. felis. Future improvement of a tick model for C. felis should consider other tick species for the injection model or utilize infection methods that more closely emulate the natural infection process.