In silico designing of novel epitope-based peptide vaccines against HIV-1

The HIV-1 virus has been regarded as a catastrophe for human well-being. The global incidence of HIV-1-infected individuals is increasing. Hence, development of effective immunostimulatory molecules has recently attracted an increasing attention in the field of vaccine design against HIV-1 infection. In this study, we explored the impacts of CD40L and IFN-γ as immunostimulatory adjuvants for our candidate HIV-1 Nef vaccine in human and mouse using immunoinformatics analyses. Overall, 18 IFN-γ-based vaccine constructs (9 constructs in human and 9 constructs in mouse), and 18 CD40L-based vaccine constructs (9 constructs in human and 9 constructs in mouse) were designed. To find immunogenic epitopes, important characteristics of each component (e.g., MHC-I and MHC-II binding, and peptide-MHC-I/MHC-II molecular docking) were determined. Then, the selected epitopes were applied to create multiepitope constructs. Finally, the physicochemical properties, linear and discontinuous B cell epitopes, and molecular interaction between the 3D structure of each construct and CD40, IFN-γ receptor or toll-like receptors (TLRs) were predicted. Our data showed that the full-length CD40L and IFN-γ linked to the N-terminal region of Nef were capable of inducing more effective immune response than multiepitope vaccine constructs. Moreover, molecular docking of the non-allergenic full-length- and epitope-based CD40L and IFN-γ constructs to their cognate receptors, CD40 and IFN-γ receptors, and TLRs 4 and 5 in mouse were more potent than in human. Generally, these findings suggest that the full forms of these adjuvants could be more efficient for improvement of HIV-1 Nef vaccine candidate compared to the designed multiepitope-based constructs.

Immunoinformatics Approach to Design a Chimeric CD70-Peptide Vaccine against Renal Cell Carcinoma

Renal cell carcinoma (RCC) accounts for the majority of cancer-related deaths worldwide. Overexpression of CD70 has been linked to advanced stages of RCC. Therefore, this study aims to develop a multiepitope vaccine targeting the overexpressed CD70 using immunoinformatics techniques. In this investigation, in silico multiepitope vaccines were constructed by linking specific CD70 protein epitopes for helper T lymphocytes and CD8+ T lymphocytes. To enhance immunogenicity, sequences of cell-penetrating peptide (CPP), penetratin (pAntp), along with the entire sequence of tumor necrosis factor-α (TNF-α), were attached to the N-terminal and C-terminal of the CD70 epitopes. Computational assessments were performed on these chimeric vaccines for antigenicity, allergenicity, peptide toxicity, population coverage, and physicochemical properties. Furthermore, refined 3D constructs were subjected to a range of analyses, encompassing structural B-cell epitope prediction and molecular docking. The chosen vaccine construct underwent diverse assessments such as molecular dynamics simulation, immune response simulation, and in silico cloning. All vaccines comprised antigenic, nontoxic, and nonallergenic epitopes, ensuring extensive global population coverage. The vaccine constructs demonstrated favorable physicochemical characteristics. The binding affinity of chimeric vaccines to the TNF receptor remained relatively stable, influenced by the alignment of vaccine components. Molecular docking and dynamics analyses predicted stable interactions between CD70-CPP-TNF and the TNF receptor, indicating potential efficacy. In silico codon optimization and cloning of the vaccine nucleic acid sequence were accomplished using the pET28a plasmid. Furthermore, this vaccine displayed the capacity to modulate humoral and cellular immune responses. Overall, the results suggest therapeutic potential for the chimeric CD70-CPP-TNF vaccine against RCC. However, validation through in vitro and in vivo experiments is necessary. This trial is registered with NCT04696731 and NCT04046445.

Immunopathogenesis of viral infections in neurological autoimmune disease

Autoimmune diseases develop due to self-tolerance failure in recognizing self and non-self-antigens. Several factors play a role in inducing autoimmunity, including genetic and environmental elements. Several studies demonstrated the causative role of viruses; however, some studies showed the preventive effect of viruses in the development of autoimmunity. Neurological autoimmune diseases are classified based on the targets of autoantibodies, which target intracellular or extracellular antigens rather than neurons. Several theories have been hypothesized to explain the role of viruses in the pathogenesis of neuroinflammation and autoimmune diseases. This study reviewed the current data on the immunopathogenesis of viruses in autoimmunity of the nervous system.

Frequency evaluation and molecular characterization of HHV-6 and HHV-7 among children under five years with fever and skin rash

Skin rash is one of the most common complications during childhood. Viral agents play an essential role in the development of such symptoms. Present study aims to determine the prevalence and genetic variability of HHV-6 & HHV-7 infections and their subtypes in children under five years of age with skin rash and negative for rubella and measles. We used serum and throat swap samples from 196 children with skin rash and fever. ELISA and IFA tests were performed to detect antibodies against HHV6/7. Sequencing was performed using Sanger sequencing, and BioEdit and MEGA10 software were used for sequence analysis. According to the results, 66% and 40% of cases were positive for HHV-6 IgM and HHV-7 IgM, respectively. According to the molecular analysis, HHV-6 Nested-PCR was positive in 18% of cases, however, HHV-7 Nested-PCR was positive in 7.7% of cases. On the other hand, HHV-6 IgG and HHV-7 IgG were positive in 91% and 55% of study cases, respectively. For HHV-6, we found some genetic variabilities resulting in antigenic changes compared to reference strains. HHV-7 isolates showed no genetic differentiation and had a stable gene sequence. Based on the results, the detection of some cases of HHV6/7 primary infection and the presence of specific symptoms of roseola in the study population needs continuous evaluation of HHV6/7 frequency and distribution, also genetic variabilities of HHV6. This can pave the way for investigating HHV6 immune evasion and vaccine research and studying the relationship between viral genetic variations and other factors like disease severity. Furthermore, it is necessary to determine the relation between HHV6 genetic changes and latent infection to be considered in possible future vaccines and antiviral drug development. This article is protected by copyright. All rights reserved.

Challenges in osteoarthritis treatment

Osteoarthritis (OA) is the most common form of arthritis and a degenerative joint cartilage disease that is the most common cause of disability in the world among the elderly. It leads to social, psychological, and economic costs with financial consequences. The principles of OA treatment are to reduce pain and stiffness as well as maintain function. In recent years, due to a better understanding of the underlying pathophysiology of OA, a number of potential therapeutic advances have been made, which include tissue engineering, immune system manipulation, surgical technique, pharmacological, and non-pharmacological treatments. Despite this, there is still no certain cure for OA, and different OA treatments are usually considered in relation to the stage of the disease. The purpose of the present review is to summarize and discuss the latest results of new treatments for OA and potential targets for future research.

Controversial role of γδ T cells in pancreatic cancer

γδ T cells are rare lymphocytes with cogent impact on immune responses. These cells are one of the earliest cells to be recruited in the sites of infection or tumors and play a critical role in coordinating innate and adaptive immune responses. The anti-tumor activity of γδ T cells have been numerously reported; nonetheless, there is controversy among published studies regarding their anti-tumor vs pro-tumor effect- especially in pancreatic cancer. A myriad of studies has confirmed that activated γδ T cells can potently lyse a broad variety of solid tumors and leukemia/lymphoma cells and produce an array of cytokines; however, early γδ T cell-based clinical trials did not lead to optimal efficacy, despite acceptable safety. Depending on the local micromilieu, γδ T cells can differentiate into tumor promoting or suppressing cells such as Th1-, Th2-, or Th17-like cells and produce prototypical cytokines such as interferon-γ (IFNγ) and interleukin (IL)-4/-10, IL-9, or IL-17. In an abstruse tumor such as pancreatic cancer- also known as immunologically cold tumor- γδ T cells are more likely to switch to their immunosuppressive phenotype. In this review we will adduce the accumulated knowledge on these two controversial aspects of γδ T cells in cancers- with a focus on solid tumors and pancreatic cancer. In addition, we propose strategies for enhancing the anti-tumor function of γδ T cells in cancers and discuss the potential future directions.

Protective and pathological roles of regulatory immune cells in human cytomegalovirus infection following hematopoietic stem cell transplantation

Human cytomegalovirus (HCMV) is ubiquitously prevalent. Immune system in healthy individuals is capable of controlling HCMV infection; however, HCMV can be life-threatening for immunocompromised individuals, such as transplant recipients. Both innate and adaptive immune systems are critically involved in the HCMV infection. Recent studies have indicated that regulatory immune cells which play essential roles in maintaining a healthy immune environment are closely related to immune response in HCMV infection. However, the exact role of regulatory immune cells in immune regulation and homoeostasis during the battle between HCMV and host still requires further research. In this review, we highlight the protective and pathological roles of regulatory immune cells in HCMV infection following hematopoietic stem cell transplantation (HSCT).

Induction of Systemic Lupus Erythematosus-like Syndrome in BALB/c Mice Leads to Disturbance in Splenic T Cell Subpopulations

Mechanisms underlying the systemic lupus erythematosus (SLE) have not yet been elucidated. In this study, we evaluated the balance of T cell subsets in BALB/c mice model of SLE induced; using Con A and polyamines as DNA immunogenicity modifiers. BALB/c mice were immunized subcutaneously with 50 µg extracted DNA from cells cultured in different conditions: splenocytes+ polyamines (group P), splenocytes+ Con A (group A), splenocytes+ polyamines+ Con A (group PA) and splenocytes only (control). Anti-double-stranded DNA -(ds-DNA) antibodies, proteinuria, and antinuclear autoantibodies were assessed by enzyme-linked immunosorbent assay, Bradford method, and immunofluorescence respectively. Transcription factors of different T helper subsets were examined by real-time polymerase chain reaction. The serum level of the anti-dsDNA antibody in group PA was higher than that in the other groups (p>0.05). Antinuclear antibody (ANA) titer increased in groups A and PA. Proteinuria level in group PA was significantly higher than that in the control group (p<0.001). Expression of Foxp3 was decreased in group A (p=0.001). Additionally, the ratios of T-bet/GATA3 and T-bet/Foxp3 were also increased in group A. (p>0.05). Our results revealed an increased ratio of Th1 to Th2 and decreased expression of Foxp3 in group A, but group PA manifested more obvious signs of the disease. These results suggest that other mechanisms rather than disturbance in T cells' balance may involve the development of disease symptoms.

Overview and Recent Advances of Regulatory T cell Therapy in Solid Organ Transplantation

Solid organ transplant recipients are in high demand for developed immune-modulating agents to control allo-immune responses following transplantation. The immunosuppressive agents offer the recipients improved short-term graft survival; nonetheless, this benefit is tempered by unavoidable long-term adverse events of these medications. Active control of allo-response using therapeutic cell transfer has gained much attraction during the last few years. It is widely established that regulatory T cells (Tregs) control immune responsiveness to allo-antigens and contribute to the induction of tolerance. Here, it is aimed to review recent results regarding Tregs and chimeric antigen receptor (CAR) Tregs therapy in solid organ transplantation and discuss strategies to overcome technical challenges of developing successful Tregs/CAR Tregs therapy.

Frequent detection of enterovirus D68 and rhinovirus type C in children with acute respiratory infections

This study aimed to evaluate the prevalence of human rhinoviruses (HRVs) and the emergence of enterovirus D68 (EV-D68) in children. A total of 322 nasopharyngeal swab samples were provided from children with an initial diagnosis of upper and lower respiratory tract infections. A total of 34 and 70 cases were positive for EV-D68 and HRV, respectively. The phylogenetic analysis revealed that the clades A and B are the prevalent genotypes for EV-D68 and the HRV-positive samples belong to three types including HRV-A, HRV-B, and HRV-C. The results showed that EV-D68 and HRV-C are circulating in Iran especially in the winter.

CAR T cells: Living HIV drugs

Human immunodeficiency virus type 1 (HIV-1), the virus that causes AIDS (acquired immunodeficiency syndrome), is a major global public health issue. Although the advent of combined antiretroviral therapy (ART) has made significant progress in inhibiting HIV replication in patients, HIV-infected cells remain the principal cellular reservoir of HIV, this allows HIV to rebound immediately upon stopping ART, which is considered the major obstacle to curing HIV infection. Chimeric antigen receptor (CAR) cell therapy has provided new opportunities for HIV treatment. Engineering T cells or hematopoietic stem cells (HSCs) to generate CAR T cells is a rapidly growing approach to develop an efficient immune cell to fight HIV. Herein, we review preclinical and clinical data available for the development of CAR T cells. Further, the advantages and disadvantages of clinical application of anti-HIV CAR T cells will be discussed.

Metabolic host response and therapeutic approaches to influenza infection

Based on available metabolomic studies, influenza infection affects a variety of cellular metabolic pathways to ensure an optimal environment for its replication and production of viral particles. Following infection, glucose uptake and aerobic glycolysis increase in infected cells continually, which results in higher glucose consumption. The pentose phosphate shunt, as another glucose-consuming pathway, is enhanced by influenza infection to help produce more nucleotides, especially ATP. Regarding lipid species, following infection, levels of triglycerides, phospholipids, and several lipid derivatives undergo perturbations, some of which are associated with inflammatory responses. Also, mitochondrial fatty acid β-oxidation decreases significantly simultaneously with an increase in biosynthesis of fatty acids and membrane lipids. Moreover, essential amino acids are demonstrated to decline in infected tissues due to the production of large amounts of viral and cellular proteins. Immune responses against influenza infection, on the other hand, could significantly affect metabolic pathways. Mainly, interferon (IFN) production following viral infection affects cell function via alteration in amino acid synthesis, membrane composition, and lipid metabolism. Understanding metabolic alterations required for influenza virus replication has revealed novel therapeutic methods based on targeted inhibition of these cellular metabolic pathways.

Histone deacetylases in virus-associated cancers

Oncogenic viruses are one of the most important causes of cancer worldwide. The pathogens contribute to the establishment of human malignancies by affecting various cellular events. Epigenetic mechanisms, such as histone modification methylation/demethylation, are one of the most critical events manipulated by oncogenic viruses to drive tumorigenesis. Histone modifications are mediated by histone acetylation and deacetylation, regulated by histone acetyltransferases (HATs) and histone deacetylases (HDACs), respectively. Dysregulation of HDACs activity affects viral tumorigenesis in several ways, such as manipulating tumor suppressor and viral gene expression. The present review aims to describe the vital interactions between both cancer-caused/associated viruses and the HDAC machinery, particularly by focusing on those viruses involved in gastrointestinal tumors, as some of the most common viral-mediated cancers.

Induction of protective immune response to intranasal administration of influenza virus-like particles in a mouse model

Human influenza A viruses (IAVs) cause global pandemics and epidemics, which remains a nonignorable serious concern for public health worldwide. To combat the surge of viral outbreaks, new treatments are urgently needed. Here, we design a new vaccine based on virus-like particles (VLPs) and show how intranasal administration of this vaccine triggers protective immunity, which can be exploited for the development of new therapies. H1N1 VLPs were produced in baculovirus vectors and were injected into BALB/c mice by the intramuscular (IM) or intranasal (IN) route. We found that there were significantly higher inflammatory cell and lymphocyte concentrations in bronchoalveolar lavage samples and the lungs of IN immunized mice; however, the IM group had little signs of inflammatory responses. On the basis of our results, immunization with H1N1 influenza VLP elicited a strong T cell immunity in BALB/c mice. Despite T cell immunity amplification after both IN and IM vaccination methods in mice, IN-induced T cell responses were significantly more intense than IM-induced responses, and this was likely related to an increased number of both CD11b^high and CD103⁺ dendritic cells in mice lungs after IN administration of VLP. Furthermore, evaluation of interleukin-4 and interferon gamma cytokines along with several chemokine receptors showed that VLP vaccination via IN and IM routes leads to a greater CD4⁺ Th1 and Th2 response, respectively. Our findings indicated that VLPs represent a potential strategy for the development of an effective influenza vaccine; however, employing relevant routes for vaccination can be another important part of the universal influenza vaccine puzzle.

Thymol as a reciprocal regulator of T cell differentiation: Promotion of regulatory T cells and suppression of Th1/Th17 cells

Regulatory T cells (Tregs) are critical for maintaining immune response and enhancing their differentiation has therapeutic implications for autoimmune diseases. In this study, we investigated the effects of thymol a well-known monoterpene from Thyme on differentiation and function of Tregs. In vitro generation of Tregs from purified naïve CD4⁺CD25^- T cells in the presence of thymol was carried out. Suppressor activity of generated Tregs was examined by changes in the proliferation of CFSE-labeled conventional T cells. Thymol promotes differentiation of naïve CD4⁺CD25^- T cells to CD4⁺CD25⁺Foxp3⁺ Tregs [66.9-71.8% vs. control (47%)] and increased intensity of Foxp3 expression on Tregs (p < 0.01). In functional assay, an increased immune suppression by thymol-induced Tregs (≈2.5 times of untreated Tregs) was detected. For in vivo study, thymol was intraperitoneally administered to ovalbumin (Ova)-immunized mice. Flow cytometry assessment of spleens from thymol-treated Ova-immunized mice showed increased number of CD4⁺ Foxp3⁺ Tregs (>8%, p < 0.01(and decreased levels of CD4⁺T-bet⁺ Th1 and CD4⁺RORγt⁺ Th17 cells resulted in significant decreased Th1/Treg and Th17/Treg ratios. In ex vivo Ova challenge of splenocytes from thymol-treated Ova-immunized mice, similarly higher levels of CD4⁺ Foxp3⁺ Tregs, and also elevated TGF-β expression in CD4⁺Foxp3⁺ population (48.1% vs. 18.9% in untreated Ova-immunized group) and reduced IFN-γ-producing CD4⁺T-bet⁺ T cells and IL-17-producing CD4⁺RORγt⁺ T cells were detected. This led to marked decreased ratios of IFNγ/TGF-β and IL-17/TGF-β expressions. In conclusion, this study revealed thymol as a compound with enhancing effects on Treg differentiation and function, which may have potential benefits in treatment of immune-mediated diseases with Th1/Th17 over-activation.

Differential regulation of CD4+ T cell subsets by Silymarin in vitro and in ovalbumin immunized mice

CD4+ T cell subsets including regulatory T cells (Tregs), Th1 and Th17 are critical for control and development of inflammation and autoimmunity. We investigated the in vitro and in vivo effects of silymarin, a well-known herbal medicine on differentiation and function of Tregs and Th1 and Th17 responses. For in vitro study, mice splenocytes treated with 20-30 μg/ml silymarin were evaluated for gene expressions of specific transcription factors and cytokines of CD4+ T cell subsets using real-time PCR. Induction of Treg cell development in the presence of silymarin was performed on isolated naïve CD4+ T cells. Effect of silymarin-induced Tregs on T cell suppression was determined by CFSE labeling method. Results of this part showed that silymarin significantly decreased IFNγ, RORγt and IL-17 gene expressions and upregulated Foxp3, TGF-β and IL-10 mRNA. More silymarin-enhanced naïve CD4+ T cells differentiated to Tregs (67%) than the control (47%). Silymarin-induced Tregs reduced proliferation of naïve activated T cells (<50%). For in vivo study, mice were immunized with ovalbumin (Ova) on days 1 and 14. Silymarin (100 mg/Kg) was intraperitoneally administered two days before the first Ova challenge followed by on every day for two weeks. Splenocytes were then isolated for assessment of CD4+ T cell subsets and ex vivo analysis using flow cytometry. Treatment of Ova-immunized mice with silymarin increased Tregs (11.24 ± 1.2%, p < 0.01(but decreased Th1 (1.72 ± 0.4%, p < 0.001) and Th17 (1.07 ± 0.04%, p < 0.001) cells. Ex vivo Ova challenge of splenocytes from Ova-immunized mice treated with silymarin decreased proliferation of splenocytes, IFNγ (2.76% of control) and IL-17 (<8%) along with increased TGF-β (59.7%) expressions in CD4+T-bet+, CD4+RORγt+ and CD4+Foxp3+ T cells, respectively. In conclusion, silymarin promoted Treg differentiation and function and decreased Th1 and Th17 cells. Silymarin may differentially regulate CD4+ T cell responses which can provide potential benefits for its use as treatment of immune-related diseases. Graphical abstract ᅟ.

Influenza vaccine: Where are we and where do we go?

The alarming rise of morbidity and mortality caused by influenza pandemics and epidemics has drawn attention worldwide since the last few decades. This life-threatening problem necessitates the development of a safe and effective vaccine to protect against incoming pandemics. The currently available flu vaccines rely on inactivated viral particles, M2e-based vaccine, live attenuated influenza vaccine (LAIV) and virus like particle (VLP). While inactivated vaccines can only induce systemic humoral responses, LAIV and VLP vaccines stimulate both humoral and cellular immune responses. Yet, these vaccines have limited protection against newly emerging viral strains. These strains, however, can be targeted by universal vaccines consisting of conserved viral proteins such as M2e and capable of inducing cross-reactive immune response. The lack of viral genome in VLP and M2e-based vaccines addresses safety concern associated with existing attenuated vaccines. With the emergence of new recombinant viral strains each year, additional effort towards developing improved universal vaccine is warranted. Besides various types of vaccines, microRNA and exosome-based vaccines have been emerged as new types of influenza vaccines which are associated with new and effective properties. Hence, development of a new generation of vaccines could contribute to better treatment of influenza.

Effect of MicroRNA-21 Transfection on In-vitro Differentiation of Human Naive CD4+ T Cells to Regulatory T Cells

Regulatory T cells (Tregs) are important components of the immune system that modulate responses of other cells. These cells are involved in peripheral tolerance mechanisms, so defect in development and function of these cells can result in autoimmune disease. Increasing evidence supports the role of microRNAs-21 (miR-21) in the regulation of forkhead box P3 (Foxp3) expression in Tregs. We aimed to determine whether miR-21 transfection to naive CD4+ T cells can be useful in generation of iTregs in-vitro. We investigated in-vitro differentiation of miR-21-transfected naive CD4+ T cells to iTregs and compared these iTregs to cytokine-differentiated iTregs and control group. We showed that expression of Foxp3, transforming growth factor beta (TGF-β), and interleukin-10 (IL-10) are increased in iTregs generated after miR-21 transfection in comparison with cytokine-differentiated iTregs and control group. Our findings demonstrate that miR-21 has positive role in in-vitro generation of induced regulatory T-cells (iTregs).

Evaluation of TLR9 expression on PBMCs and CpG ODN-TLR9 ligation on IFN-α production in SLE patients

CONTEXT

Systemic lupus erythematosus (SLE) is a systemic autoimmune disease characterized by autoreactive antibodies. Recent findings revealed the importance of innate immune responses, especially Toll-like receptors (TLRs) in the pathogenesis of SLE.

OBJECTIVE

In this study, the level of TLR9 expression on peripheral blood mononuclear cells (PBMCs) was analyzed. The levels of produced IFN-α were also measured in supernatant of PBMCs from SLE patients and healthy controls after stimulation with CpG ODN2216 which is a plasmocytoid dendritic cell (pDC)-specific TLR9 ligand.

MATERIALS AND METHODS

TLR9 expression was analyzed by real-time polymerase chain reaction (PCR) and flow cytometry in 35 SLE patients and 38 healthy controls and IFN-α concentration was measured in supernatants using enzyme-linked immunosorbent assay (ELISA).

RESULTS

The results showed that the TLR9 expression in the mRNA and the protein level was significantly higher in PBMCs from SLE patients. However, IFN-α concentration in patients and controls significantly increased in response to CpG stimulation but this increase was significantly higher in healthy controls compared with SLE patients. Our results do not show any association between taking hydroxychloroquine and reduction in IFN-α production in SLE patients.

DISCUSSION AND CONCLUSIONS

Regarding the findings of the study, there is the possibility that TLR9 has played a role in SLE pathogenesis, and consequently it implies that TLRs can be considered to be the therapeutic targets for systemic autoimmunity. We may conclude that PBMCs in patients are functionally impaired in response to TLR ligation via innate response stimulating pathogen-associated molecular patterns (PAMPs).

A cytotoxin-producing strain of Vibrio cholerae non-O1, non-O139 as a cause of cholera and bacteremia after consumption of raw clams

We report a case of a cholera-like gastroenteritis subsequent with bacteremia in a healthy man following consumption of raw clams. Although we failed to recover the organism from the patient's stool culture, his blood culture was positive for a non-cholera toxin-producing yet cytotoxin-producing non-O1 and non-O139 Vibrio cholerae.

Abiotrophia species as a cause of endophthalmitis following cataract extraction

Microorganisms of the genus Abiotrophia, members of the oral flora, are known as important causes of bacterial endocarditis. In this study, we report two individual cases of acute vitreous infection caused by Abiotrophia adiacens and Abiotrophia defectiva approximately a week after cataract extraction. Abiotrophia isolates were recovered by cultivation of vitreous humor on chocolate agar and identified via conventional and API 20 Strep identification systems. An 83-year-old male patient (A) and an 80-year-old female patient (B) demonstrated almost identical symptoms of infectious endophthalmitis manifested as hypopyon and opaque media. The vision of both patients was reduced to detection of hand motion in the left and the right eyes, respectively. An emergency pars plana core vitrectomy was performed, and intraocular antibiotics were administered to each patient, who presented 8 months apart in two different institutions. Patients A and B were treated with an intravitreal injection of vancomycin-amikacin and vancomycin-ceftazidime, respectively, which resulted in complete recovery.

Comparison of culture and acid-fast bacilli stain to PCR for detection of Mycobacterium tuberculosis in clinical samples

The major drawback in effective use of polymerase chain reaction (PCR) for detecting Mycobacterium tuberculosis (MTB) in clinical samples is the presence of PCR inhibitors and unique cell components of the organism that complicate DNA extraction and subsequent PCR amplification. A PCR assay with a unique multistep DNA extraction method that minimizes these problems was compared in a prospective study to acid-fast bacilli stain (AFBS) and culture for detecting MTB in clinical samples. A total of 254 clinical specimens in two separate studies were processed for MTB by these techniques. While PCR and culture were 100% sensitive and specific, culture required up to 8 weeks of incubation and additional time to perform biochemical testing to identify the isolated micro-organism. Acid-fast bacilli stain had a specificity of about 87% and did not differentiate among Mycobacterial species. In contrast, the results from PCR were available within 48 h and did not require additional testing to attain a final result. Polymerase chain reaction was highly reliable for detection and confirmation and interpretation of positive AFBS results. The assay was easy to perform with a turn around time of about 2 days.

A PCR assay for identification of Enterococcus faecium

Enterococcus faecium has recently emerged as a serious nosocomial pathogen. The prevalence and severity of enterococcal infections, the mortality rate from such infections, and the antibiotic resistance of enterococci are often species dependent. Since conventional biochemical methods fail to differentiate E. faecium from certain newly described enterococcal species, a PCR-based assay was developed for the rapid identification of E. faecium.

Listeria monocytogenes infections: laboratory investigation of an unexpected increase in incidence

Listeria monocytogenes is a facultative intracellular pathogen causing mainly meningitis and septicemia in immunocompromised hosts. From July 1988 through December 1989, 16 patients at The Mount Sinai Hospital were diagnosed as having listeriosis shortly after admission, 14 within a one-year period (July 1988-July 1989). Because this incidence was almost double the incidence in previous years (< 8 annually), an epidemiologic and microbiologic investigation was undertaken to determine a potential route of acquisition of L. monocytogenes. On the basis of plasmid profile, bacteriocin (enterocin) susceptibility pattern, and serotype, no single epidemic strain could be identified. Although direct evidence was lacking, we concluded that our patients may have acquired L. monocytogenes through transient contamination of food.

Aeromonas caviae: ecologic adaptation in the intestinal tract of infants coupled to adherence and enterotoxin production as factors in enteropathogenicity

Aeromonas caviae isolated from stools of diarrheic formula-fed infants and environmental sources produce acetic acid when grown in glucose broth, which is bactericidal (suicide phenomenon). A. caviae grows anaerobically in a minimal medium or under permissive conditions such as the intestinal tract of formula-fed infants. These isolates adhered to HEp-2 cells and produced a cytotoxic and a cytotonic enterotoxin which underscore their enteropathogenicity.

Glucose-mediated catabolite repression of the tricarboxylic acid cycle as an explanation for increased acetic acid production in suicidal Aeromonas strains

Growth in the presence of glucose, even under highly aerobic conditions, significantly reduced the activities of three tricarboxylic acid cycle enzymes, citrate synthetase, alpha-ketoglutarate dehydrogenase, and malate dehydrogenase, in suicidal but not nonsuicidal Aeromonas strains. Pyruvate dehydrogenase activity, however, was significantly increased. The activities of all of the enzymes, as well as the glucose-mediated increase in acetic acid production, were shown to be regulated by catabolite repression. The regulator protein is the same one which regulates the utilization of several sugars.

Microbiologic and clinical evidence supporting the role of Aeromonas caviae as a pediatric enteric pathogen

Aeromonas caviae was recovered as the sole potential enteric pathogen from the stools of 14 of 17 symptomatic children (10 younger than 1 year of age) while Aeromonas hydrophila, Aeromonas sobria, and Plesiomonas shigelloides were isolated once each. The infants from whom A. caviae was isolated all presented with a watery diarrhea lasting 1 to 3 weeks. None of these infants was breast-fed, and all had a stool pH of greater than 7.5. All of the A. caviae isolates, including a reference strain (ATCC 15468), adhered to HEp-2 cells, and preliminary data showed that they produced a cytotoxin as well. Because A. caviae can survive at an elevated pH, as found in the gastrointestinal tract of formula-fed infants, and because of the adherence and cytotoxin production capabilities of the species, it should be regarded as an enteric pathogen in pediatric patients and most probably among adults as well.

Suicide phenomenon in mesophilic aeromonads as a basis for species identification

The acetic acid-mediated suicide phenomenon in mesophilic aeromonads in conjunction with tests for aerogenicity and esculin hydrolysis served as the basis for species identification. Of 210 Aeromonas isolates tested at 30 degrees C, 88 were identified as Aeromonas hydrophila (nonsuicidal, aerogenic, esculin positive), 52 were identified as A. sobria (suicide variable, aerogenic, esculin negative), and 70 were identified as A. caviae (suicidal, anaerogenic, esculin positive). These identifications paralleled those achieved by biochemical criteria.

The suicide phenomenon in motile aeromonads

Certain strains of motile Aeromonas species, including all those of Aeromonas caviae examined, were shown to be suicidal. When they were grown in the presence of glucose at both 30 and 37 degrees C, there was rapid die-off of the organisms after 12 h of incubation, and viable cells generally could not be recovered after 24 h. It was shown that this phenomenon was due to the production of relatively high levels of acetic acid by these strains, even during growth under highly aerobic conditions, and to the greater susceptibility of these strains to acetic acid-mediated death. Suicide did not occur when the pH was maintained above 6.5 or in the presence of high concentration of Pi. These observations were consistent with our inability to isolate suicidal Aeromonas spp. from acidic lakes in New England and with their recovery from alkaline waters in Israel and from sewage. Suicidal aeromonads appear to be better adapted than the nonsuicidal biotypes to anaerobic growth in low-nutrient environments.

Correlation of the suicide phenomenon in Aeromonas species with virulence and enteropathogenicity

Certain strains of mesophilic aeromonads (Aeromonas hydrophila, A. sorbria, and A. caviae), when grown in broth containing 0.5% glucose, undergo growth inhibition concomitant with acetate accumulation. Because these strains are nonviable after 24 h, this phenomenon is termed suicide. We investigated suicidal strains of Aeromonas species as a means of understanding animal virulence and enteropathogenicity. To assess virulence, batches of five white mice were inoculated intraperitoneally with 10(7) cells (washed) of suicidal and nonsuicidal strains of A. hydrophila and A. sobria and suicidal strains of A. caviae. The three nonsuicidal strains of A. sobria tested showed lethality as early as 12 h and were uniformly fatal within 36 h postinoculation. After 36 h, the three suicidal strains killed only 1 of 15 mice inoculated. Four A. hydrophila strains tested which showed the suicide phenomenon at 37 degrees C were variably lethal (40 to 100%). None of three suicidal strains of A. caviae were lethal. Enteropathogenicity was studied by orally inoculating three white mice each with the same Aeromonas strains (10(8) cells, in skim milk) and assessing diarrhea and intestinal fluid accumulation. Diarrhea and fluid accumulation were present in all mice inoculated with two nonsuicidal strains of A. sobria and in 4 of 12 mice given four suicidal strains of A. hydrophila. Two suicidal strains each of A. sorbria and A. caviae failed to elicit any gastrointestinal disturbances. These data suggest that the suicide phenomenon may explain strain-specific (A. sobria and A. hydrophila) and species-specific (A. caviae) virulence and enteropathogenicity.