LcrV Plague Vaccine with Altered Immunomodulatory Properties

Abstract

Yersinia pestis, the causative agent of plague, secretes LcrV (low-calcium-response V or V antigen) during infection. LcrV triggers the release of interleukin 10 (IL-10) by host immune cells and suppresses proinflammatory cytokines such as tumor necrosis factor alpha and gamma interferon as well as innate defense mechanisms required to combat the pathogenesis of plague. Although immunization of animals with LcrV elicits protective immunity, the associated suppression of host defense mechanisms may preclude the use of LcrV as a human vaccine. Here we show that short deletions within LcrV can reduce its immune modulatory properties. An LcrV variant lacking amino acid residues 271 to 300 (rV10) elicited immune responses that protected mice against a lethal challenge with Y. pestis. Compared to full-length LcrV, rV10 displayed a reduced ability to release IL-10 from mouse and human macrophages. Furthermore, the lipopolysaccharide-stimulated release of proinflammatory cytokines by human or mouse macrophages was inhibited by full-length LcrV but not by the rV10 variant. Thus, it appears that LcrV variants with reduced immune modulatory properties could be used as a human vaccine to generate protective immunity against plague.Plague epidemics have likely killed more people worldwide than any other infectious disease (36,54). Mammals, in particular rats, prairie dogs, and gerbils, are the primary reservoir of Yersinia pestis, and human disease transmission occurs by flea bites, aerosol, or contact (15, 17). Flea bite-transmitted Y. pestis infection leads to bubonic plague, with characteristic lymph node swellings and disease symptoms that progress frequently to systemic infection and pneumonia (7,14). Aerosol transmission of virulent Y. pestis, whether during plague epidemics or deliberate dissemination, precipitates pneumonic plague, a rapidly fatal disease with few characteristic symptoms (28). Considering the ubiquitous zoonotic nature of the disease and the possible illegitimate use of Y. pestis as a weapon, there is an urgent need for vaccine development to protect humans against bubonic and pneumonic plague (36).Some, but not all, bubonic plague victims survive the disease, even without therapy, and appear to develop immunity (12,48). Burrows discovered Y. pestis LcrV as a protective antigen which stimulates humoral immune responses in experimental animals that afford protection against plague infection (10, 11). Based on these observations, several laboratories developed recombinant LcrV subunit vaccines, either alone or in combination with other Y. pestis proteins, and demonstrated that a humoral immune response to LcrV confers plague protection in experimental animals (2,21,25,31,32,47). Brubaker and colleagues first showed that LcrV injection of animals stimulates the release of interleukin 10 (IL-10), a cytokine that suppresses innate immune functions (8, 34). LcrV injection also prevents the release of proinflammatory cytokines, such as gamma interferon (IFN-␥) or tumor necrosis factor alpha (TNF-␣), during ...

Role of immune response in Yersinia pestis infection

“…Other mechanisms used by Y. pestis can also disturb the host immune responses; for example, it has been shown that the effectors YopP/YopJ of T3SS can be injected into endothelial cells and reduce the expression of adhesion molecules (ICAM-1 and E-selectin) on endothelial and bronchial epithelial cells, inhibiting the recruitment of PMNs to the infection site [47,48]. In addition to YopP, LcrV also inhibits neutrophil chemotaxis in vivo and in vitro [49].…”

ppGpp Conjures Bacterial Virulence

“…Therefore, SpoT is sufficient to elicit a posttranscriptional mechanism that induces the expression of Y. pestis virulence factors directly or indirectly. Specifically, ppGpp induces the expression of three T3SS effectors: YopE and YopH, effectors that disrupt the host cell cytoskeleton and facilitate the resistance of phagocytosis (157,183,190), and LcrV, a factor that triggers interleukin-10 (IL-10) release and suppresses the proinflammatory cytokines tumor necrosis factor alpha (TNF-␣) and gamma interferon (IFN-␥) (142,150). As predicted, IL-10 levels in sera of mice inoculated with relA spoT mutants were diminished compared to those in the sera of mice inoculated with the WT.…”

Plant-Derived Recombinant Fl, V, and F1-V Fusion Antigens ofYersinia PestisActivate Human Cells of the Innate and Adaptive Immune System

“…Evidence of the interaction of V antigen with human TLR2 has been provided (34)(35). Overheim et al (35) showed that LcrV derived from Y. pestis and purified fromE. coli induced IL-I 0 from murine macrophages and human monocytes.…”

“…Such effects would depend on TLR2 stimulation (33). Evidence of the interaction of V antigen with human TLR2 has been provided (34)(35). Overheim et al (35) showed that LcrV derived from Y. pestis and purified fromE.…”