Immunogens in Balamuthia mandrillaris: a proteomic exploration

Balamuthia mandrillaris is the causative agent of granulomatous amoebic encephalitis, a rare and often fatal infection affecting the central nervous system. The amoeba is isolated from diverse environmental sources and can cause severe infections in both immunocompromised and immunocompetent individuals. Given the limited understanding of B. mandrillaris, our research aimed to explore its protein profile, identifying potential immunogens crucial for early granulomatous amoebic encephalitis diagnosis. Cultures of B. mandrillaris and other amoebas were grown under axenic conditions, and total amoebic extracts were obtained. Proteomic analyses, including two-dimensional electrophoresis and mass spectrometry, were performed. A 50-kDa band showed a robust recognition of antibodies from immunized BALB/c mice; peptides contained in this band were matched with elongation factor-1 alpha, which emerged as a putative key immunogen. Besides, lectin blotting revealed the presence of glycoproteins in B. mandrillaris, and confocal microscopy demonstrated the focal distribution of the 50-kDa band throughout trophozoites. Cumulatively, these observations suggest the participation of the 50-kDa band in adhesion and recognition mechanisms. Thus, these collective findings demonstrate some protein characteristics of B. mandrillaris, opening avenues for understanding its pathogenicity and developing diagnostic and therapeutic strategies.

Identification of differential protein recognition pattern between Naegleria fowleri and Naegleria lovaniensis

Many pathogenicity factors are involved in the development of primary amoebic meningoencephalitis (PAM) caused by N fowleri. However, most of them are not exclusive for N fowleri and they have not even been described in other nonpathogenic Naegleria species. Therefore, the objective of this work was to identify differential proteins and protein pattern recognition between Naegleria fowleri and Naegleria lovaniensis using antibodies anti-N fowleri as strategy to find vaccine candidates against meningoencephalitis. Electrophoresis and Western blots conventional and 2-DE were performed for the identification of antigenic proteins, and these were analysed by the mass spectrometry technique. The results obtained in 2-DE gels and Western blot showed very notable differences in spot intensity between these two species, specifically those with relative molecular weight of 100, 75, 50 and 19 kDa. Some spots corresponding to these molecular weights were identified as actin fragment, myosin II, heat shock protein, membrane protein Mp2CL5 among others, with differences in theoretical post-translational modifications. In this work, we found differences in antigenic proteins between both species, proteins that could be used for a further development of vaccines against N fowleri infection.

Neutrophils extracellular traps damage Naegleria fowleri trophozoites opsonized with human IgG

Naegleria fowleri infects humans through the nasal mucosa causing a disease in the central nervous system known as primary amoebic meningoencephalitis (PAM). Polymorphonuclear cells (PMNs) play a critical role in the early phase of N. fowleri infection. Recently, a new biological defence mechanism called neutrophil extracellular traps (NETs) has been attracting attention. NETs are composed of nuclear DNA combined with histones and antibacterial proteins, and these structures are released from the cell to direct its antimicrobial attack. In this work, we evaluate the capacity of N. fowleri to induce the liberation of NETs by human PMN cells. Neutrophils were cocultured with unopsonized or IgG-opsonized N. fowleri trophozoites. DNA, histone, myeloperoxidase (MPO) and neutrophil elastase (NE) were stained, and the formation of NETs was evaluated by confocal microscopy and by quantifying the levels of extracellular DNA. Our results showed N. fowleri induce the liberation of NETs including release of MPO and NE by human PMN cells as exposure interaction time is increased, but N. fowleri trophozoites evaded killing. However, when trophozoites were opsonized, they were susceptible to the neutrophils activity. Therefore, our study suggests that antibody-mediated PMNs activation through NET formation may be crucial for antimicrobial responses against N. fowleri.

Molecular modeling studies demonstrate key mutations that could affect the ligand recognition by influenza AH1N1 neuraminidase

The goal of this study was to identify neuraminidase (NA) residue mutants from human influenza AH1N1 using sequences from 1918 to 2012. Multiple alignment studies of complete NA sequences (5732) were performed. Subsequently, the crystallographic structure of the 1918 influenza (PDB ID: 3BEQ-A) was used as a wild-type structure and three-dimensional (3-D) template for homology modeling of the mutated selected NA sequences. The 3-D mutated NAs were refined using molecular dynamics (MD) simulations (50 ns). The refined 3-D models were used to perform docking studies using oseltamivir. Multiple sequence alignment studies showed seven representative mutations (A232V, K262R, V263I, T264V, S367L, S369N, and S369K). MD simulations applied to 3-D NAs showed that each NA had different active-site shapes according to structural surface visualization and docking results. Moreover, Cartesian principal component analyses (cPCA) show structural differences among these NA structures caused by mutations. These theoretical results suggest that the selected mutations that are located outside of the active site of NA could affect oseltamivir recognition and could be associated with resistance to oseltamivir.

Prevalence of bovine subclinical mastitis, its etiology and diagnosis of antibiotic resistance of dairy farms in four municipalities of a tropical region of Mexico

A region-wide survey was conducted in the tropical area of Tierra Caliente, State of Guerrero, Mexico to estimate the prevalence of subclinical bovine mastitis (SCM), distribution of mastitis pathogens, and in vitro antimicrobial susceptibility of different mastitis pathogens in dairy farms. In total, 1036 quarter milk samples were obtained from 259 cows at 87 different dairy farms. Collected quarter milk samples were submitted for California Mastitis Test (CMT), bacteriological examination, and testing for antimicrobial susceptibility. Overall prevalence of SCM in the studied area was 20.5 %. Prevalence in the different regions was as follows: 28 % in Arcelia municipality, 21 % in Tlalchapa municipality, 19.4 % in Pungarabato municipality, and 14.3 % in Finch Cutzamala municipality. Of all positive isolates, 97.5 % were Gram-negative bacteria. Moreover, of all positive isolates, 37.5 % were Proteus vulgaris, 25 % Salmonella spp., 12.5 % Enterobacter aerogenes, and 10 % Escherichia coli. Klebsiella pneumonia and E. coli were sensitive for netilmicin antimicrobial. However, E. coli was sensitive for pefloxacin and gentamicin with a sensitivity for pefloxacin for E. aerogenes, while Staphylococci were sensitive for gentamicin and dicloxacillin. It could be concluded that practices such as the implementation of mastitis control programs, improved milking hygiene together with an intramammary treatment with netilmicin, pefloxacin, and gentamicin antimicrobials should be considered for mastitis prevention in the study area of Tierra Caliente, in the tropical area of Guerrero, Mexico.

Purification and cellular localization of the Entamoeba histolytica transcarboxylase

Genome analysis of Entamoeba histolytica predicts the presence of acetyl-CoA carboxylase. Using Western blot, histochemistry, and confocal microscopy, we demonstrated the presence of a biotin-containing protein in the cytoplasm of E. histolytica, with a molecular weight of 136 kDa and biotin-carboxylase activity. This protein probably corresponds to a transcarboxylase that catalyzes the rate-limiting reaction leading to fatty acid elongation.

Intranasal immunization with Naegleria fowleri lysates and Cry1Ac induces metaplasia in the olfactory epithelium and increases IgA secretion

According to previous reports, intranasal administration of the Cry1Ac protein alone or with amoebic lysates increases protection against Naegleria fowleri meningoencephalitis in mice, apparently by eliciting IgA responses in the nasal mucosa. In the current study, we performed an immunohistochemical analysis of IgA in the nasal mucosa of mice immunized intranasally with Cry1Ac, and amoebic lysates or a combination of both. The animals were sacrificed 24 h after the last immunization or after an intranasal lethal challenge with N. fowleri. Our results indicate that all of the intranasal immunizations provoked an increase in areas with metaplasia in the olfactory epithelium, allowing for secretion of IgA. As a result, IgA antibodies were found interacting with trophozoites in the nasal lumen, and there was a marked increase of IgA in the metaplasic epithelium. On the other hand in nonimmunized mice trophozoites were observed invading the nasal mucosa, which was not the case for immunized mice. Our results suggest that intranasal immunization provokes cellular changes in the olfactory epithelium, leading to greater protection against N. fowleri that is probably caused by an increased secretion of IgA. The increased IgA response induced in the nasal mucosa by immunization probably impedes both amoebic adhesion and subsequent invasion of the parasite to the nasal epithelium.

Phenotypic and functional differences between lymphocytes from NALT and nasal passages of mice

Nasal-associated lymphoid tissue (NALT) and nasal passages (NP) are considered as inductive and effector sites, respectively. The differences among lymphocyte populations of these nasal compartments have not been clearly established. The aim of this work was to contribute to the characterization of NALT and NP lymphocytes in mice. We isolated lymphocytes from both compartments, determined the frequencies of B220(+) cells as well as CD8(+), CD4(+) T cells; and analysed the expression of CD69 and CD25. Besides we analysed the proportion of T cells producing IL-2, IL-4, IL-5, IL-10, IFN-gamma and TNF-alpha. We found differences between NALT and NP. Two populations of B cells, B220+(hi) and B220+(low) were clearly distinguished only in NP, but not in NALT. Both (hi) and (low) B220(+) cells expressed CD19, but only a fraction of the B220+(low) population, expressed the plasma cell marker CD138(+). More B than T lymphocytes, as well as higher frequencies of CD4(+) than CD8(+) T cells were found in both compartments. A small fraction of NK cells (CD3(-)DX5(+)) along with a significant proportion of double negative CD4(-)CD8(-)CD3(+)DX5(-) T cells was detected in both nasal tissues. Furthermore, as expected for a mucosal effector site, NP contained major proportions of B220(+), T CD4(+) and T CD8(+) cells expressing CD25 and CD69 in comparison to NALT. Likewise, the proportion of T cells spontaneously producing IL-2, IFN-gamma, and IL-4, was higher in NP than in NALT. These data provide further evidence indicating that distinctive phenotypic and functional features exist in the lymphocyte populations residing at NALT and NP.

Immunohistochemical characterization of the initial stages of Naegleria fowleri meningoencephalitis in mice

The initial stages of Naegleria fowleri meningoencephalitis in mice were immunohistochemically characterized following the first 8 h post-intranasal inoculation. The events found after 8 h were: (1) amebas in contact with the mucous layer of the olfactory epithelium, (2) numerous parasites eliminated by extensive shedding of the mucous layer, and (3) many organisms reaching the nasal epithelium. In contrast to other works, we observed that after 24 h, amebas invaded the epithelium, without evidence of the disruption of the nasal mucosa. In addition some trophozoites invading through the respiratory epithelium were observed, suggesting an additional invasion route. The inflammatory response detected was scarce until 30 h post-inoculation. After 96 h, the inflammatory response was severe in the olfactory bulb and brain, and the tissue damage great. Consequently, an inflammatory reaction may enhance tissue damage but apparently does not destroy amebas which seem to proliferate in the olfactory bulb.

Immunoblot analysis of IgA antibodies to Naegleria fowleri in human saliva and serum

The objective of this study was to evaluate the secretory IgA (SIgA) antibody response to Naegleria fowleri (Nf) in individuals living in a parasite endemic area. Saliva and serum samples were obtained from both healthy subjects and patients suffering from a respiratory illness (chronic bronchitis or rhinitis) and were analyzed by immunoblot assay. SIgA from the patients' samples recognized more intensely a greater number of Nf proteins than did SIgA from the healthy control group. The proteins more frequently recognized were those with a molecular weight of 171, 107, 102, 62, 50, 46, and 10 kDa. Some IgA antibodies recognized proteins from Nf and Entamoeba histolytica (Eh) of similar molecular weight. These results suggest that some of those antibodies could have been elicited by a previous intestinal infection with Eh. Through the common mucosal immune system the IgA B-cells activated by Eh antigens can be disseminated to all the mucosae, including the nasal mucosa. SIgA antibodies recognizing Nf proteins, induced either by specific immunization or by cross-reaction, could participate in the resistance to the infection, probably by inhibiting the adherence of Nf trophozoites to the nasal mucosa.