Construction of a Complementary DNA Library of Parelaphostrongylus tenuis and Identification of a Potentially Sero-Diagnostic Recombinant Antigen

Flagella hook protein FlgE is a novel vaccine candidate of Pseudomonas aeruginosa identified by a genomic approach

Infections due to Pseudomonas aeruginosa (PA) are becoming a serious threat to patients in intensive care units. A PA vaccine is a practical and economical solution to solve the problems caused by PA infection successfully. In recent years, several antigen candidates have been tested in animal and human clinical trials, but none of them has been approved to date. An alternative strategy for antigen screening and protective antigens is in urgent demand. In this study, we generated a genome-wide library of PA protein fragments tagged with maltose-binding protein (MBP). Using sera from patients who recovered after PA infection, we identified a novel protective antigen, FlgE, which is the structural component of the flagella hook. Vaccination with recombinant FlgE (reFlgE) induced a Th2-predominant immune response and reduced bacterial load and inflammation in PA-infected mice. Anti-reFlgE antibodies recognized native FlgE on the bacterial membrane in vitro and conferred protection in mice, which may be due to the mediation of opsonophagocytic killing and inhibition of bacterial motility. In addition, the combination of reFlgE with rePcrV_NH, an engineered antigen we reported previously, provided elevated protection against PA infection. Our data demonstrate that FlgE is a promising vaccine candidate for PA and provide a new strategy for the efficient screening of antigens of other pathogens.

Analysis of heavy-chain antibody responses and resistance to Parelaphostrongylus tenuis in experimentally infected alpacas

The parasitic nematode Parelaphostrongylus tenuis is an important cause of neurologic disease of camelids in central and eastern North America. The aim of this study was to determine whether alpacas develop resistance to disease caused by P. tenuis in response to a previous infection or a combination of controlled infection and immunization. Alpacas were immunized with a homogenate of third-stage larvae (L3) and simultaneously implanted subcutaneously with diffusion chambers containing 20 live L3. Sham-treated animals received adjuvant alone and empty chambers. The protocol was not effective in inducing resistance to oral challenge with 10 L3, and disease developed between 60 and 71 days following infection. Immediately following the onset of neurologic disease, affected animals were treated with a regimen of anthelmintic and anti-inflammatory drugs, and all recovered. One year later, a subset of alpacas from this experiment was challenged with 20 L3 and the results showed that prior infection induced resistance to disease. Primary and secondary infections induced production of conventional and heavy-chain IgGs that reacted with soluble antigens in L3 homogenates but did not consistently recognize a recombinant form of a parasite-derived aspartyl protease inhibitor. Thus, the latter antigen may not be a good candidate for serology-based diagnostic tests. Antibody responses to parasite antigens occurred in the absence of overt disease, demonstrating that P. tenuis infection can be subclinical in a host that has been considered to be highly susceptible to disease. The potential for immunoprophylaxis to be effective in preventing disease caused by P. tenuis was supported by evidence of resistance to reinfection.