Adjuvant treatment increases the resistance to Mycobacterium avium infection of mycobacteria-susceptible BALB/c mice

In vivo immunogenicity of Tax(11-19) epitope in HLA-A2/DTR transgenic mice: implication for dendritic cell-based anti-HTLV-1 vaccine

Viral oncoprotein Tax plays key roles in transformation of human T-cell leukemia virus (HTLV-1)-infected T cells leading to adult T-cell leukemia (ATL), and is the key antigen recognized during HTLV-associated myelopathy (HAM). In HLA-A2+ asymptomatic carriers as well as ATL and HAM patients, Tax(11-19) epitope exhibits immunodominance. Here, we evaluate CD8 T-cell immune response against this epitope in the presence and absence of dendritic cells (DCs) given the recent encouraging observations made with Phase 1 DC-based vaccine trial for ATL. To facilitate these studies, we first generated an HLA-A2/DTR hybrid mouse strain carrying the HLA-A2.1 and CD11c-DTR genes. We then studied CD8 T-cell immune response against Tax(11-19) epitope delivered in the absence or presence of Freund's adjuvant and/or DCs. Overall results demonstrate that naturally presented Tax epitope could initiate an antigen-specific CD8T cell response in vivo but failed to do so upon DC depletion. Presence of adjuvant potentiated Tax(11-19)-specific response. Elevated serum IL-6 levels coincided with depletion of DCs whereas decreased TGF-β was associated with adjuvant use. Thus, Tax(11-19) epitope is a potential candidate for the DC-based anti-HTLV-1 vaccine and the newly hybrid mouse strain could be used for investigating DC involvement in human class-I-restricted immune responses.

Cell recruitment and cytokines in skin mice sensitized with the vaccine adjuvants: saponin, incomplete Freund's adjuvant, and monophosphoryl lipid A

Vaccine adjuvants are substances associated with antigens that are fundamental to the formation of an intense, durable, and fast immune response. In this context, the use of vaccine adjuvants to generate an effective cellular immune response is crucial for the design and development of vaccines against visceral leishmaniasis. The objective of this study was to evaluate innate inflammatory response induced by the vaccine adjuvants saponin (SAP), incomplete Freund’s adjuvant (IFA), and monophosphoryl lipid A (MPL). After a single dose of adjuvant was injected into the skin of mice, we analyzed inflammatory reaction, selective cell migration, and cytokine production at the injection site, and inflammatory cell influx in the peripheral blood. We found that all vaccine adjuvants were able to promote cell recruitment to the site without tissue damage. In addition, they induced selective migration of neutrophils, macrophages, and lymphocytes. The influx of neutrophils was notable at 12 h in all groups, but at other time points it was most evident after inoculation with SAP. With regard to cytokines, the SAP led to production of interleukin (IL)-2, IL-6, and IL-4. IFA promoted production of tumor necrosis factor (TNF)-α, interferon (IFN)-γ, IL-6, IL-17, IL-4, and IL-10. We also observed that MPL induced high production of IL-2, TNF-α, and IFN-γ, in addition to IL-6, IL-17, and IL-10. In peripheral blood, values of certain cell populations in the local response changed after stimulation. Our data demonstrate that the three vaccine adjuvants stimulate the early events of innate immune response at the injection site, suggesting their ability to increase the immunogenicity of co-administered antigens. Moreover, this work provides relevant information about elements of innate and acquired immune response induced by vaccine adjuvants administered alone.

Mycobacterial infections: are the observed enigmas and paradoxes explained by immunosuppression and immunodeficiency?

The enigmas and paradoxes observed in tuberculous patients, in Bacille Calmette-Guérin-vaccinated people and in Bacille Calmette-Guérin-treated cancer patients have been examined, in an attempt to explain them through the mechanisms of immunodeficiency and immunosuppression. A dual effect is postulated: an immunosuppression induced by the infecting mycobacteria that adds to a pre-existing or emerging state of immunodeficiency of the infected individual. The immunological cellular and humoral anergies observed at the beginning of a tuberculous therapy are usually lifted after the first two weeks of treatment. This restoration of immune responsiveness may be attributed to the destruction or to the growth inhibition of immunosuppressive mycobacteria. The observation that drugs cytocidal in vitro do not always sterilize the patients under treatment whereas bacteriostatic drugs do, may find an explanation in the dual immunosuppression induced by cytocidal drugs and mycobacteria. The fact that Bacille Calmette-Guérin applied as an immunotherapy to residual cancer has either a favorable or an unfavorable action may be due to the immunosuppressive activity attached to some Bacille Calmette-Guérin strains and to some cancers. The variable protective activity of Bacille Calmette-Guérin vaccines may be due to the immunological status of the vaccinated people and the compositional differences between strains. The protective activity of subunit vaccines in experimental models can be attributed to the elimination of immunosuppressive factors present in whole killed mycobacteria.

Stress modulates acute inflammation triggered by mycobacteria in autoimmunity-prone and normal mice

We have investigated the effect of a single stress treatment of mice on the early cellular response (granulocyte influx) of acute inflammation that was produced by intraperitoneal inoculation of the animals with mycobacteria (10(6) bacilli of M. avium). Autoimmunity-prone (NZB/W) and normal (BALB/c, MRL, NZW) mice were submitted to the same stress (20 min of swimming) this given either before or simultaneously with the induction of the intraperitoneal mycobacteria-induced inflammation. Local inflammation was evaluated by the quantification of leukocytes harvested from the peritoneal cavity of the mice; this was done 30 and 60 minutes after the end of the stress treatment. We found that the stressor alone was able to increase the number of cells that were harvested from the peritoneal cavity; this may be due to stress-induced detachment of resident macrophages from the peritoneal walls. The autoimmunity-prone mice (NZB/W) showed a marked decrease in the number of inflammatory cells (mostly of granulocytes) when stress treatment was performed immediately before the triggering of inflammation; these stress-induced alterations were attenuated in normal mice (BALB/c and MRL strains), as well as in the non-autoimmune parent strain (NSW) of NZB/W mice. Modulation of the acute inflammatory response by stress was smaller if the stress was induced concomitantly with the triggering of inflammation; here, NZB/W were again the mice most affected by stress. Our data indicate that [1] stress is able to modify the acute inflammatory response of mice; [2] autoimmunity-prone mice are more sensitive to stress-induced modulation of inflammation than normal animals; and [3] the timing of stress (with regard to the initiation of inflammatory phenomena) is an important factor in the intensity of changes produced by stress in the early cellular response of acute inflammation.

Effect of mycobacterial infection in the lupus-prone MRL/lpr mice: enhancement of life span of autoimmune mice, amelioration of kidney disease and transient decrease in host resistance

We have used the MRL/lpr murine model of spontaneous lupus to investigate three questions in infection immunity: (1) does mycobacterial infection have any effect on the mortality of the autoimmunity-prone lpr mice?; (2) does the infection modify the progression of kidney disease of lpr lupus?; and (3) does the lpr gene change the resistance of mice to mycobacteria? Experimental infections were induced by intraperitoneal inoculation of 10(7) viable bacilli of Mycobacterium avium in 3 months old MRL/lpr mice and also in congeneic MRL/+ mice (lacking the lpr gene). MRL mice were sacrificed 1, 2.5 and 4 months after the M. avium injection. We found that infection caused lowering of urine protein concentration in lpr mice as compared with age-matched lpr controls. Mycobacteriosis also induced a marked decrease in the mortality of lpr animals, e.g. 85% of infected lpr mice reached the age of 7 months whereas only 10% of control lpr mice reached the same age. MRL/lpr mice showed, after 1 and 2.5 months of infection, higher mycobacterial loads than the congeneic non-lpr MRL mice; after 4 months of infection, however, differences in M. avium loads between the two groups of MRL mice became not statistically significant. We conclude that: (1) mycobacterial infection increases the life span of lpr mice; (2) the infection slows down the progression of kidney disease in the lupus-prone lpr animals; (3) the autoimmunity gene lpr is associated with a transient decrease in host resistance to mycobacteria.