The Ag85B protein of the BCG vaccine facilitates macrophage uptake but is dispensable for protection against aerosol Mycobacterium tuberculosis infection

Defining the function and protective capacity of mycobacterial antigens is crucial for progression of tuberculosis (TB) vaccine candidates to clinical trials. The Ag85B protein is expressed by all pathogenic mycobacteria and is a component of multiple TB vaccines under evaluation in humans. In this report we examined the role of the BCG Ag85B protein in host cell interaction and vaccine-induced protection against virulent Mycobacterium tuberculosis infection. Ag85B was required for macrophage infection in vitro, as BCG deficient in Ag85B expression (BCG:(Δ85B)) was less able to infect RAW 264.7 macrophages compared to parental BCG, while an Ag85B-overexpressing BCG strain (BCG:(oex85B)) demonstrated improved uptake. A similar pattern was observed in vivo after intradermal delivery to mice, with significantly less BCG:(Δ85B) present in CD64(hi)CD11b(hi) macrophages compared to BCG or BCG:(oex85B). After vaccination of mice with BCG:(Δ85B) or parental BCG and subsequent aerosol M. tuberculosis challenge, similar numbers of activated CD4(+) and CD8(+) T cells were detected in the lungs of infected mice for both groups, suggesting the reduced macrophage uptake observed by BCG:(Δ85B) did not alter host immunity. Further, vaccination with both BCG:(Δ85B) and parental BCG resulted in a comparable reduction in pulmonary M. tuberculosis load. These data reveal an unappreciated role for Ag85B in the interaction of mycobacteria with host cells and indicates that single protective antigens are dispensable for protective immunity induced by BCG.

Influence of phthiocerol dimycocerosate on CD4(+) T cell priming and persistence during Mycobacterium tuberculosis infection

The characterisation of mycobacterial factors that influence or modulate the host immune response may aid the development of more efficacious TB vaccines. We have previously reported that Mycobacterium tuberculosis deficient in export of Phthiocerol Dimycocerosates (DIM) (MT103(ΔdrrC)) is more attenuated than wild type M. tuberculosis and provides sustained protective immunity compared to the existing BCG vaccine. Here we sought to define the correlates of immunity associated with DIM deficiency by assessing the impact of MT103(ΔdrrC) delivery on antigen presenting cell (APC) function and the generation of CD4(+) T cell antigen-specific immunity. MT103(ΔdrrC) was a potent activator of bone marrow derived dendritic cells, inducing significantly greater expression of CD86 and IL-12p40 compared to BCG or the MT103 parental strain. This translated to an increased ability to initiate early in vivo priming of antigen-specific CD4(+) T cells compared to BCG with enhanced release of IFN-γ and TNF upon antigen-restimulation. The heightened immunity induced by MT103(ΔdrrC) correlated with greater persistence within the spleen compared to BCG, however both MT103(ΔdrrC) and BCG were undetectable in the lung at 70 days post-vaccination. In immunodeficient RAG (-/-) mice, MT103(ΔdrrC) was less virulent than the parental MT103 strain, yet MT103(ΔdrrC) infected mice succumbed more rapidly compared to BCG-infected animals. These results suggest that DIM translocation plays a role in APC stimulation and CD4(+) T cell activation during M. tuberculosis infection and highlights the potential of DIM-deficient strains as novel TB vaccine candidates.

Potent antimycobacterial activity of the pyridoxal isonicotinoyl hydrazone analog 2-pyridylcarboxaldehyde isonicotinoyl hydrazone: a lipophilic transport vehicle for isonicotinic acid hydrazide

The rise in drug-resistant strains of Mycobacterium tuberculosis is a major threat to human health and highlights the need for new therapeutic strategies. In this study, we have assessed whether high-affinity iron chelators of the pyridoxal isonicotinoyl hydrazone (PIH) class can restrict the growth of clinically significant mycobacteria. Screening a library of PIH derivatives revealed that one compound, namely, 2-pyridylcarboxaldehyde isonicotinoyl hydrazone (PCIH), exhibited nanomolar in vitro activity against Mycobacterium bovis bacille Calmette-Guérin and virulent M. tuberculosis. Interestingly, PCIH is derived from the condensation of 2-pyridylcarboxaldehyde with the first-line antituberculosis drug isoniazid [i.e., isonicotinic acid hydrazide (INH)]. PCIH displayed minimal host cell toxicity and was effective at inhibiting growth of M. tuberculosis within cultured macrophages and also in vivo in mice. Further, PCIH restricted mycobacterial growth at high bacterial loads in culture, a property not observed with INH, which shares the isonicotinoyl hydrazide moiety with PCIH. When tested against Mycobacterium avium, PCIH was more effective than INH at inhibiting bacterial growth in broth culture and in macrophages, and also reduced bacterial loads in vivo. Complexation of PCIH with iron decreased its effectiveness, suggesting that iron chelation may play some role in its antimycobacterial efficacy. However, this could not totally account for its potent efficacy, and structure-activity relationship studies suggest that PCIH acts as a lipophilic vehicle for the transport of its intact INH moiety into the mammalian cell and the mycobacterium. These results demonstrate that iron-chelating agents such as PCIH may be of benefit in the treatment and control of mycobacterial infection.

Host cell-induced components of the sulfate assimilation pathway are major protective antigens of Mycobacterium tuberculosis

New therapies to control tuberculosis are urgently required because of the inability of the only available vaccine, BCG, to adequately protect against tuberculosis. Here we demonstrate that proteins of the Mycobacterium tuberculosis sulfate-assimilation pathway (SAP) represent major immunogenic targets of the bacillus, as defined by strong T-cell recognition by both mice and humans infected with M. tuberculosis. SAP proteins displayed increased expression when M. tuberculosis was resident within host cells, which may account in part for their ability to stimulate anti-M. tuberculosis host immunity. Vaccination with the first enzyme in this pathway, adenosine-5'-triphosphate sulfurylase, conferred significant protection against murine tuberculosis and boosted BCG-induced protective immunity in the lung. Therefore, we have identified SAP components as a new family of M. tuberculosis antigens, and we have demonstrated that these components are promising candidate for inclusion in new vaccines to control tuberculosis in humans.

Personal experience of the treatment of ruptured aortic aneurysms. The prognostic evaluation of some parameters

BACKGROUND

The rupture of an aortic aneurysm is the most frequent and most severe complication, with an incidence of approximately 20-40/100,000 persons each year. The aim of this study was to identify the preoperative, intraoperative and postoperative factors that may influence the mortality rate.

METHODS

Between January 1996 and December 1999 145 patients underwent emergency abdominal aortic repair surgery. One hundred and twenty-three patients represented a ruptured AAA and 22 a fissured aneurysm. One hundred and thirty-one patients were males and 14 were females; their mean age was 75+/-5.06 years. We selected a number of parameters after a review of the international literature and these were analysed in the two classes of survivors. No statistical analyses were performed on fissured aneurysms owing to the scant number of cases examined.

RESULTS

Mortality was 41.4% (44.7% in ruptured aneurysms alone). The following were negative preoperative prognostic factors: old age, hypertension, ASA V, intraoperative anuria and platelet count <100,000. Intraoperative factors included: hypotension, cardiac arrest, onset of anuria, aortic clamping in more than one site, duration of surgery, quantity of RBC and plasma transfused. The main postoperative variables correlated to mortality were: hypotension, hypothermia, onset of anuria, need for further transfusions, high creatinine levels.

CONCLUSIONS

Rapid intervention can minimise mortality in structures with expert teams of surgeons and anesthetists experienced in treating this type of pathology.

Mid-term results of endovascular repair for abdominal aortic aneurysm, with loco-regional anesthesia, in high-risk patients

BACKGROUND

Aim of this study was to evaluate the results of endovascular repair of abdominal aortic aneurysm (AAA) in patients considered not suitable for traditional open surgical repair because of the high anesthesiological risk.

METHODS

We have retrospectively evaluated the result of the endovascular treatment of 11 patients with AAA of more than 6 cm diameter and high surgical risk due to cardiac hypokinesia and/or respiratory insufficiency. Patients were selected by a team composed of vascular surgeons and vascular radiologists who decided to implant the graft according to anatomical features of the AAA and of the iliac arteries. The treatment was performed in loco-regional anesthesia. The main end-points were: implantation success, mortality, morbidity, the absence of endoleak during the follow up that lasted two years.

RESULTS

All the grafts were successfully implanted. There were no complications caused by anesthesiological manouvres. We had a minor intra-operative vascular complication and we performed three adjunctive endovascular procedures. A patient died of acute myocardial infarction, in the post operative period. Mean stay was six days. Pre-discharge scan showed 3 endoleaks (type I), two of these healed spontaneously and one sealed by percutaneous endovascular treatment. During follow-up (3-24 months) no patient died. One endoleak (type II) still persists. CONCLUSIONS The use of loco-regional anaesthesia allows us to treat high risk patients. Following strictly the criteria of patient selection, the surgical high risk seems not to influence significantly the mid term results that are almost equal to the ones obtained in low-risk patients.

Carotid endoarterectomy in the presence of contralateral carotid occlusion

BACKGROUND

The purpose of this study was to define a correct anesthesiological and surgical approach in patient who present a significant carotid stenosis with contralateral carotid occlusion.

METHODS

Between 1996 and 1998 in our Department of Vascular Surgery of the Hospital S. Giovanni Battista has been executed 337 Carotid Endoarterectomies (CEA). Of these, 44 patient (13%) had a contralateral internal carotid occlusion. Forty was male (91%), and 4 female (9%). Echo Doppler, angiography, angioTC or angio-RMN and TCD were performed in all patients. In all cases was executed a traditional CEA.

RESULTS

Because of the presence of a large ischaemic cerebral lesion or clamping intolerance 12 operation were performed under general anesthesia (27%). Shunt was used in 15 patients (34%) and patch was used in 10 cases (23%). In 2 cases (4.5%) there was be a thrombosis of the operated internal carotid artery and one patient died (2.3%).

CONCLUSIONS

The presence of contralateral internal carotid occlusion with carotid stenosis > 70% increase the risk of peroperative stroke because of the difficulty of collateral cerebral blood flow. The execution of echo Doppler, angiography, angioTC or angioRM and TCD and their evaluation permit to choice the best anesthesiological and surgical treatment. The utilization of narcosis with thiopental protection and shunting reducing the rate of perioperative stroke, but the local anesthesia allows the best monitoring of intraoperative cerebral function. This behaviour was correctly when in patient with contralateral internal carotid occlusion there is an insufficient intracranic vascularization or an extensive ischaemic lesion or clamping intolerance.