Ether lipid vesicle-based antigens impart protection against experimental listeriosis
Authors: Ejaj Ahmad
Mohammad Owais
Swaleha Zubair
Zainuddin Quadri
Mairaj Ahmed Ansari
Mohsin Raza Khan
Saba Tufail
Journal: International Journal of Nanomedicine (2012)
Discipline: PHARMACOLOGY & TOXICOLOGY
Keywords: Th1 cytokines; antigen-presenting cells; archaeosome; co- stimulatory markers; culture supernatant
Affiliations: Interdisciplinary Biotechnology Unit, Aligarh Muslim University, Aligarh, UP, India.

Abstract:  Background: Incidence of food-borne infections from Listeria monocytogenes, a parasite that has adapted intracellular residence to avoid antibody onslaught, has increased dramatically in the past few years. The apparent lack of an effective vaccine that is capable of evoking the desired cytotoxic T cell response to obliterate this intracellular pathogen has encouraged the investigation of alternate prophylactic strategies. It should also be noted that Archaebacteria (Archae) lipid-based adjuvants enhance the efficacy of subunit vaccines. In the present study, the adjuvant properties of archaeosomes (liposomes prepared from total polar lipids of archaebacteria, Halobacterium salinarum) combined with immunogenic culture supernatant antigens of L. monocytogenes have been exploited in designing a vaccine candidate against experimental listeriosis in murine model. Methods: Archaeosome-entrapped secretory protein antigens (SAgs) of L. monocytogenes were evaluated for their immunological responses and tendency to deplete bacterial burden in BALB/c mice challenged with sublethal listerial infection. Various immunological studies involving cytokine profiling, lymphocyte proliferation assay, detection of various surface markers (by flowcytometric analysis), and antibody isotypes (by enzyme-linked immunosorbent assay) were used for establishing the vaccine potential of archaeosome-entrapped secretory proteins. Results: Immunization schedule involving archaeosome-encapsulated SAgs resulted in upregulation of Th1 cytokine production along with boosted memory in BALB/c mice. It also showed protective effect by reducing listerial burden in various vital organs (liver and spleen) of the infected mice. However, the soluble form of the antigens (SAgs) and their physical mixture with sham (empty) archaeosomes, besides showing feeble Th1 response, were unable to protect the animals against virulent listerial infection. Conclusion: On the basis of the evidence provided by the current data, it is inferred that archaeosome-entrapped SAgs formulation not only enhances cytotoxic T cell response but also helps in the clearance of pathogens and thereby increases the survival of the immunized animals. 

Retracted: No

PubPeer comments:
 Figure 7A. * Red boxes: the lower quadrants of panels i (Sham archaeosomes as control) and iv (archaeosome-entrapped culture supernatant SAgs) appear to look very similar, while the upper quadrants are very different. Could the authors provide an explanation for what happened here?  , 
 The number of dots in quadrants are quite different, the plots look similar but they are not identicle. , 
 #2 Surprisingly many points in both panels represent cells with identical properties, so they cancel out when superimposed. Perhaps they are not identical, but  good enough for government work .  , 
 #2 Dr. Qatari: Sir, thank you for your reply. It would be hoped that the authors will be able to respond to the original query: u201cCould the authors provide an explanation for what happened here?u201d Readers can see for themselves the overlap, which Hoya nicely demonstrated in #2. The question remains open: is there a scientific explanation that will reassure readers? , 
 As one can see Hoya also infers that two concerned quadrants are too similar, however, not identical. The publication was made way back. However, all we have to say that the percentage of the cell population in four different quadrants is different in the two sets. Each of the quadrants specifies a specific surface phenotype. The software says that the actual value is 69.78 and 53.4% respectively in the two groups. ,