Evaluation of a temperature-restricted, mucosal tuberculosis vaccine in guinea pigs

Tuberculosis (TB) is currently the leading cause of death in humans by a single infectious agent, Mycobacterium tuberculosis. The Bacillus Calmette-Guérin (BCG) vaccine prevents pulmonary TB with variable efficacy, but can cause life-threatening systemic infection in HIV-infected infants. In this study, TBvac85, a derivative of Mycobacterium shottsii expressing M. tuberculosis Antigen 85B, was examined as a safer alternative to BCG. Intranasal vaccination of guinea pigs with TBvac85, a naturally temperature-restricted species, resulted in serum Ag85B-specific IgG antibodies. Delivery of the vaccine by this route also induced protection equivalent to intradermal BCG based on organ bacterial burdens and lung pathology six weeks after aerosol challenge with M. tuberculosis strain Erdman. These results support the potential of TBvac85 as the basis of an effective TB vaccine. Next-generation derivatives expressing multiple M. tuberculosis immunogens are in development.

Zika virus and Guillain-Barré syndrome in Bangladesh

Objective

Previous studies have associated Guillain–Barré syndrome (GBS) with Zika virus (ZIKV) outbreaks in South America and Oceania. In Asia, ZIKV is known to circulate widely, but the association with Guillain–Barré syndrome is unclear. We investigated whether endemic ZIKV infection is associated with the development of GBS.

Methods

A prospective study was conducted from 2011 to 2015 in Bangladesh. A total of 418 patients and 418 healthy family controls were included in the study. Patients were diagnosed with GBS prior to inclusion according to established criteria. Detailed information on the epidemiology, clinical presentation, electrophysiology, diagnosis, disease severity, and clinical course were obtained during a follow‐up of 1 year using a predefined protocol.

Results

ZIKV‐neutralizing antibodies were detected in our study from 2013 onwards. The prevalence of ZIKV‐neutralizing antibodies was not significantly higher in patients with GBS compared to healthy controls (OR 2.23, P = 0.14, 95% CI 0.77–6.53). Serological evidence for prior ZIKV infection in patients with GBS was associated with more frequent cranial, sensory, and autonomic nerve involvement compared to GBS patients with Campylobacter jejuni, the predominant preceding infection in GBS worldwide. Nerve‐conduction studies revealed that ZIKV antibodies were associated with a demyelinating subtype of GBS, while C. jejuni infections were related to an axonal subtype.

Interpretation

No significant association was found between ZIKV infection and GBS in Bangladesh, but GBS following ZIKV infection was characterized by a distinct clinical and electrophysiological subtype compared to C. jejuni infection. These findings indicate that ZIKV may precede a specific GBS subtype but the risk is low.

Diagnostic Bacteriology: Raman Spectroscopy

Current clinical methodology for identification of bacterial infections relies predominantly on culturing microbes from patient material and performing biochemical tests. This can often be an inefficient and lengthy process, which has a significant detrimental effect upon patient care. Techniques used in other aspects of molecular research have the potential to revolutionize the way in which diagnostic tests are used and delivered in the clinical setting. The need for rapid, accurate, and cost-effective molecular techniques in the diagnostic laboratory is imperative to improving patient care, preventing the spread of drug resistance and decreasing the overall burden associated with nosocomial infections. Raman spectroscopy and surface-enhanced Raman spectroscopy (SERS) are powerful vibrational spectroscopy techniques that are being developed for highly sensitive pathogen identification in complex clinical samples. Raman spectroscopy is a molecular technique that is capable of probing samples noninvasively and nondestructively. It has been used with high specificity to assess tissue and bacterial samples at the molecular level with diverse clinical and diagnostic applications. SERS has recently developed out of the advances in the Raman spectroscopy arena. This technique is designed to amplify Raman scattering and allows for better differentiation of bacterial isolates. Although the current parameters for the use of SERS require a pure culture and are relatively monoparametric, current breakthroughs and testing are pushing the technology to new levels and thus changing the face of modern bacterial diagnostics.

Rv3351c, a Mycobacterium tuberculosis gene that affects bacterial growth and alveolar epithelial cell viability

Despite the interactions known to occur between various lower respiratory tract pathogens and alveolar epithelial cells (AECs), few reports examine factors influencing the interplay between Mycobacterium tuberculosis bacilli and AECs during infection. Importantly, in vitro studies have demonstrated that the M. tuberculosis hbha and esxA gene products HBHA and ESAT6 directly or indirectly influence AEC survival. In this report, we identify Rv3351c as another M. tuberculosis gene that impacts the fate of both the pathogen and AEC host. Intracellular replication of an Rv3351c mutant in the human AEC type II pneumocyte cell line A549 was markedly reduced relative to the complemented mutant and parent strain. Deletion of Rv3351c diminished the release of lactate dehydrogenase and decreased uptake of trypan blue vital stain by host cells infected with M. tuberculosis bacilli, suggesting attenuated cytotoxic effects. Interestingly, an isogenic hbha mutant displayed reductions in AEC killing similar to those observed for the Rv3351c mutant. This opens the possibility that multiple M. tuberculosis gene products interact with AECs. We also observed that Rv3351c aids intracellular replication and survival of M. tuberculosis in macrophages. This places Rv3351c in the same standing as HBHA and ESAT6, which are important factors in AECs and macrophages. Defining the mechanism(s) by which Rv3351c functions to aid pathogen survival within the host may lead to new drug or vaccine targets.

Bioburden Increases Heterotopic Ossification Formation in an Established Rat Model

BACKGROUND

Heterotopic ossification (HO) develops in a majority of combat-related amputations wherein early bacterial colonization has been considered a potential early risk factor. Our group has recently developed a small animal model of trauma-induced HO that incorporates many of the multifaceted injury patterns of combat trauma in the absence of bacterial contamination and subsequent wound colonization.

QUESTIONS/PURPOSES

We sought to determine if (1) the presence of bioburden (Acinetobacter baumannii and methicillin-resistant Staphylococcus aureus [MRSA]) increases the magnitude of ectopic bone formation in traumatized muscle after amputation; and (2) what persistent effects bacterial contamination has on late microbial flora within the amputation site.

METHODS

Using a blast-related HO model, we exposed 48 rats to blast overpressure, femur fracture, crush injury, and subsequent immediate transfemoral amputation through the zone of injury. Control injured rats (n = 8) were inoculated beneath the myodesis with phosphate-buffered saline not containing bacteria (vehicle) and treatment rats were inoculated with 1 × 10(6) colony-forming units of A baumannii (n = 20) or MRSA (n = 20). All animals formed HO. Heterotopic ossification was determined by quantitative volumetric measurements of ectopic bone at 12-weeks postinjury using micro-CT and qualitative histomorphometry for assessment of new bone formation in the residual limb. Bone marrow and muscle tissue biopsies were collected from the residual limb at 12 weeks to quantitatively measure the bioburden load and to qualitatively determine the species-level identification of the bacterial flora.

RESULTS

At 12 weeks, we observed a greater volume of HO in rats infected with MRSA (68.9 ± 8.6 mm(3); 95% confidence interval [CI], 50.52-85.55) when compared with A baumannii (20.9 ± 3.7 mm(3); 95% CI, 13.61-28.14; p < 0.001) or vehicle (16.3 ± 3.2 mm(3); 95% CI, 10.06-22.47; p < 0.001). Soft tissue and marrow from the residual limb of rats inoculated with A baumannii tested negative for A baumannii infection but were positive for other strains of bacteria (1.33 × 10(2) ± 0.89 × 10(2); 95% CI, -0.42 × 10(2)-3.08 × 10(2) and 1.25 × 10(6) ± 0.69 × 10(6); 95% CI, -0.13 × 10(6)-2.60 × 10(6) colony-forming units in bone marrow and muscle tissue, respectively), whereas tissue from MRSA-infected rats contained MRSA only (4.84 × 10(1) ± 3.22 × 10(1); 95% CI, -1.47 × 10(1)-11.1 × 10(1) and 2.80 × 10(7) ± 1.73 × 10(7); 95% CI, -0.60 × 10(7)-6.20 × 10(7) in bone marrow and muscle tissue, respectively).

CONCLUSIONS

Our findings demonstrate that persistent infection with MRSA results in a greater volume of ectopic bone formation, which may be the result of chronic soft tissue inflammation, and that early wound colonization may be a key risk factor.

CLINICAL RELEVANCE

Interventions that mitigate wound contamination and inflammation (such as early débridement, systemic and local antibiotics) may also have a beneficial effect with regard to the mitigation of HO formation and should be evaluated with that potential in mind in future preclinical studies.

HspX vaccination and role in virulence in the guinea pig model of tuberculosis

Mycobacterium tuberculosis (Mtb) currently infects billions of people; many of whom are latently infection and at risk for reactivation. Mycobacterium bovis Bacille Calmette-Guerin (BCG) while approved as a vaccine, is unable to prevent reactivation of latent tuberculosis infection (LTBI). Subunit vaccines boosting BCG or given alone are being tested for efficacy in LTBI models. Alpha-crystallin (Acr, HspX), is a latency associated protein and subunit vaccine candidate. In this report, three HspX formulas (native and two recombinant variants) were used as vaccines in the guinea pig model of tuberculosis; none were protective during challenge with WT Mtb. However, recombinant HspX was protective in animals challenged with a strain of Mtb lacking hspX (X4-19), indicating protection was driven by molecules co-purifying with HspX or an adjuvant effect of recombinant HspX in this system. Mtb X4-19 was significantly less virulent than WT Mtb. Quantitative PCR and whole genome sequencing identified several genes (Rv2030c-Rv2032, Rv1062, Rv1771, Rv1907, and Rv3479) with altered expression that may contribute to loss of virulence. Physiological differences required for the establishment of Mtb infection in different hosts may affect the potential of subunit vaccines to elicit protection, supporting the need for rigorous biochemical and modeling analyses when developing tuberculosis vaccines.