A novel candidate vaccine for cytauxzoonosis inferred from comparative apicomplexan genomics.

Cytauxzoonosis is an emerging infectious disease of domestic cats (Felis catus) caused by the apicomplexan protozoan parasite Cytauxzoon felis. The growing epidemic, with its high morbidity and mortality points to the need for a protective vaccine against cytauxzoonosis. Unfortunately, the causative agent has yet to be cultured continuously in vitro, rendering traditional vaccine development approaches beyond reach. Here we report the use of comparative genomics to computationally and experimentally interpret the C. felis genome to identify a novel candidate vaccine antigen for cytauxzoonosis. As a starting point we sequenced, assembled, and annotated the C. felis genome and the proteins it encodes. Whole genome alignment revealed considerable conserved synteny with other apicomplexans. In particular, alignments with the bovine parasite Theileria parva revealed that a C. felis gene, cf76, is syntenic to p67 (the leading vaccine candidate for bovine theileriosis), despite a lack of significant sequence similarity. Recombinant subdomains of cf76 were challenged with survivor-cat antiserum and found to be highly seroreactive. Comparison of eleven geographically diverse samples from the south-central and southeastern USA demonstrated 91-100% amino acid sequence identity across cf76, including a high level of conservation in an immunogenic 226 amino acid (24 kDa) carboxyl terminal domain. Using in situ hybridization, transcription of cf76 was documented in the schizogenous stage of parasite replication, the life stage that is believed to be the most important for development of a protective immune response. Collectively, these data point to identification of the first potential vaccine candidate antigen for cytauxzoonosis. Further, our bioinformatic approach emphasizes the use of comparative genomics as an accelerated path to developing vaccines against experimentally intractable pathogens.

Increased cytokine and nitric oxide levels in serum of dogs experimentally infected with Rangelia vitalii.

This study aimed to measure the levels of interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), interleukin 1 (IL-1), interleukin 6 (IL-6), and nitrite/nitrate (NO x ) in serum of dogs experimentally infected with Rangelia vitalii. Twelve female mongrel dogs were divided into 2 groups; group A (uninfected controls) composed by healthy dogs (n=5) and group B consisting of dogs inoculated with R. vitalii (n=7). Animals were monitored by blood smear examinations, which showed intraerythrocytic forms of the parasite on day 5 post-infection (PI). Blood samples were collected through the jugular vein on days 0, 10, and 20 PI to determine the serum levels of IFN-γ, TNF-α, IL-1, IL-6, and NO x . Cytokines were assessed by ELISA quantitative sandwich technique, and NO x was measured by the modified Griess method. Cytokine levels (IFN-γ, TNF-α, IL-1, and IL-6) were increased (P<0.01) in serum of infected animals. Serum levels of NO x were also increased on days 10 PI (P<0.01) and 20 PI (P<0.05) in infected animals. Therefore, the infection with R. vitalii causes an increase in proinflammatory cytokines and nitric oxide content. These alterations may be associated with host immune protection against the parasite.

Increased Cytokine and Nitric Oxide Levels in Serum of Dogs Experimentally Infected with Rangelia vitalii

This study aimed to measure the levels of interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha), interleukin 1 (IL-1), interleukin 6 (IL-6), and nitrite/nitrate (NOx) in serum of dogs experimentally infected with Rangelia vitalii. Twelve female mongrel dogs were divided into 2 groups; group A (uninfected controls) composed by healthy dogs (n=5) and group B consisting of dogs inoculated with R. vitalii (n=7). Animals were monitored by blood smear examinations, which showed intraerythrocytic forms of the parasite on day 5 post-infection (PI). Blood samples were collected through the jugular vein on days 0, 10, and 20 PI to determine the serum levels of IFN-gamma, TNF-alpha, IL-1, IL-6, and NOx. Cytokines were assessed by ELISA quantitative sandwich technique, and NOx was measured by the modified Griess method. Cytokine levels (IFN-gamma, TNF-alpha, IL-1, and IL-6) were increased (P<0.01) in serum of infected animals. Serum levels of NOx were also increased on days 10 PI (P<0.01) and 20 PI (P<0.05) in infected animals. Therefore, the infection with R. vitalii causes an increase in proinflammatory cytokines and nitric oxide content. These alterations may be associated with host immune protection against the parasite.