Brucella activates the host RIDD pathway to subvert BLOS1-directed immune defense.

The phagocytosis and destruction of pathogens in lysosomes constitute central elements of innate immune defense. Here, we show that Brucella, the causative agent of brucellosis, the most prevalent bacterial zoonosis globally, subverts this immune defense pathway by activating regulated IRE1α-dependent decay (RIDD) of Bloc1s1 mRNA encoding BLOS1, a protein that promotes endosome-lysosome fusion. RIDD-deficient cells and mice harboring a RIDD-incompetent variant of IRE1α were resistant to infection. Inactivation of the Bloc1s1 gene impaired the ability to assemble BLOC-1-related complex (BORC), resulting in differential recruitment of BORC-related lysosome trafficking components, perinuclear trafficking of Brucella-containing vacuoles (BCVs), and enhanced susceptibility to infection. The RIDD-resistant Bloc1s1 variant maintains the integrity of BORC and a higher-level association of BORC-related components that promote centrifugal lysosome trafficking, resulting in enhanced BCV peripheral trafficking and lysosomal destruction, and resistance to infection. These findings demonstrate that host RIDD activity on BLOS1 regulates Brucella intracellular parasitism by disrupting BORC-directed lysosomal trafficking. Notably, coronavirus murine hepatitis virus also subverted the RIDD-BLOS1 axis to promote intracellular replication. Our work establishes BLOS1 as a novel immune defense factor whose activity is hijacked by diverse pathogens.

Interactions between fungal hyaluronic acid and host CD44 promote internalization by recruiting host autophagy proteins to forming phagosomes.

Phagocytosis and autophagy play critical roles in immune defense. The human fungal pathogen Cryptococcus neoformans (Cn) subverts host autophagy-initiation complex (AIC)-related proteins, to promote its phagocytosis and intracellular parasitism of host cells. The mechanisms by which the pathogen engages host AIC-related proteins remain obscure. Here, we show that the recruitment of host AIC proteins to forming phagosomes is dependent upon the activity of CD44, a host cell surface receptor that engages fungal hyaluronic acid (HA). This interaction elevates intracellular Ca2+ concentrations and activates CaMKKß and its downstream target AMPKα, which results in activation of ULK1 and the recruitment of AIC components. Moreover, we demonstrate that HA-coated beads efficiently recruit AIC components to phagosomes and CD44 interacts with AIC components. Taken together, these findings show that fungal HA plays a critical role in directing the internalization and productive intracellular membrane trafficking of a fungal pathogen of global importance.

The candidate vaccine strain Brucella ovis ∆abcBA is protective against Brucella melitensis infection in mice.

Brucellosis is a major zoonotic disease, and Brucella melitensis is the species most often associated with human infection. Vaccination is the most efficient tool for controlling animal brucellosis, with a consequent decrease of incidence of human infections. Commercially available live attenuated vaccines provide some degree of protection, but retain residual pathogenicity to human and animals. In this study, Brucella ovis ∆abcBA (Bo∆abcBA), a live attenuated candidate vaccine strain, was tested in two formulations (encapsulated with alginate and alginate plus vitelline protein B [VpB]) to immunize mice against experimental challenge with B. melitensis strain 16M. One week after infection, livers and spleens of immunized mice had reduced numbers of the challenge strain B. melitensis 16M when compared with those of nonimmunized mice, with a reduction of approximately 1-log10 of B. melitensis 16M count in the spleens from immunized mice. Moreover, splenocytes stimulated with B. melitensis antigens in vitro secreted IFN-γ when mice had been immunized with Bo∆abcBA encapsulated with alginate plus VpB, but not with alginate alone. Body and liver weights were similar among groups, although spleens from mice immunized with Bo∆abcBA encapsulated with alginate were larger than those immunized with Bo∆abcBA encapsulated with alginate plus VpB or nonimmunized mice. This study demonstrated that two vaccine formulations containing Bo∆abcBA protected mice against experimental challenge with B. melitensis.

Genetic characterization of the haemagglutinin gene in canine distemper virus strains from naturally infected dogs in Brazil / Caracterização genética do gene da hemaglutinina em vírus da cinomose canina de cães naturalmente infectados no Brasil

Canine distemper is one of the major infectious diseases in dogs and wild animals, resulting in high morbidity and mortality. The H gene has the greatest genetic variability among the genes encoded by the canine distemper virus (CDV) genome, and it has been used to characterise field samples, allowing the identification of specific lineages. Variation in the H gene can allow the virus to evade recognition by vaccine-induced antibodies, resulting in vaccine failure. The purpose of this study was to characterise H gene in CDV strains from naturally infected dogs in the state of São Paulo. The phylogenetic analysis revealed that Brazilian CDV strains were genetically related to the circulating CDV strains in Uruguay, Argentina, and Europe. We found no evidence of South America 2 and 3 CDV lineages circulating in Brazilian dogs. The degree of genetic divergence between wild Brazilian CDV strains and vaccine strains may suggest the possibility of vaccine failures and consequently the occurrence of canine distemper outbreaks.(AU)

A cinomose canina é uma das principais doenças infecciosas em cães e animais selvagens, resultando em alta morbidade e mortalidade. O gene H tem uma das maiores variabilidades genéticas entre os genes codificados pelo vírus da cinomose canina (CDV), e tem sido utilizado para caracterizar as estirpes de CDV, permitindo a identificação de linhagens específicas. A variação no gene H pode permitir que o vírus evite o reconhecimento por anticorpos induzidos pela vacina, resultando em falha vacinal. O objetivo deste estudo foi caracterizar o gene H em estirpes de CDV de cães infectados naturalmente no estado de São Paulo. A análise filogenética revelou que as estirpes de CDV brasileiras estão geneticamente relacionadas as estirpes circulantes no Uruguai, na Argentina e na Europa. Não foi encontrada nenhuma evidência da circulação no estado de São Paulo das linhagens América do Sul 2 e 3. O grau de divergência genética entre linhagens selvagens de CDV brasileiras e as estirpes vacinais podem sugerir a possibilidade de falhas vacinais e consequentemente a ocorrência de surtos de cinomose canina.(AU)

SYSTEMIC HISTIOCYTIC SARCOMA IN A COMMON HIPPOPOTAMUS (HIPPOPOTAMUS AMPHIBIUS).

A 37-yr-old captive common hippopotamus (Hippopotamus amphibius) developed lethargy and decline in mobility that progressed to death, despite supportive therapy. Histopathologic examination revealed severe, diffuse, intravascular and interstitial infiltration of neoplastic histiocytes in the spleen, liver, lymph nodes, lungs, large intestine, kidneys, and thyroid gland. Neoplastic cells were pleomorphic with marked anisocytosis and anisokaryosis, scattered multinucleated giant cells, numerous bizarre mitotic figures, and marked erythrophagocytosis. Immunohistochemistry demonstrated that neoplastic cells were positive for ionized calcium-binding adapter molecule 1 (a histiocytic marker) and negative for CD3 (a T-cell marker) and myeloperoxidase, confirming the diagnosis of systemic histiocytic sarcoma.

Serologic and molecular evidence of Brucella ovis infection in ovine and caprine flocks in the State of Minas Gerais, Brazil.

BACKGROUND: Brucella ovis infection is one of the leading causes of sub fertility and infertility in ovine, been characterized mainly by epididymitis, orchitis and testicular atrophy in rams. This study aimed to determine the frequency of B. ovis positivity in rams and goats flocks in the State of Minas Gerais, Brazil, by agarose gel immunodiffusion (AGID), ELISA, Rose Bengal, PCR and bacteriological isolation as diagnostic tools. FINDINGS: Serum and urine samples were collected from properties with sheep or goat flocks, or from properties with mixed flock. Out of 50 sheep flocks, 6% (3/50) were seropositive by AGID while 4% (2/50) were positive by urine PCR for B. ovis. Out of five goat farms, 20% (1/5) were seropositive for B. ovis by AGID. Mixed flock farms had 11.1% (2/18) of positivity by AGID. By ELISA, 19.5% (8/41) of sheep properties and 61.1% (11/18) of the properties with mixed flocks were positive for B. ovis. No samples were positive in the test of Rose Bengal, ruling out exposure to smooth LPS Brucella species (particularly Brucella melitensis) and indicating that the positive in the ELISA was associated with Brucella spp. LPS rough (presumably B. ovis). No urine sample from sheep or goat was positive by bacteriological isolation. CONCLUSIONS: Our results demonstrate serologic or molecular evidence of B. ovis infection in several rams and billy goats from meso-regions of the State of Minas Gerais, Brazil. Also, this study report the indirect ELISA as an important tool for the diagnosis of B. ovis infection, as indirect ELISA in this study demonstrated to be the most sensitive diagnostic method adopted.

Transcription of innate immunity genes and cytokine secretion by canine macrophages resistant or susceptible to intracellular survival of Leishmania infantum.

In this study we assessed the basal transcription of genes associated with innate immunity (i.e. Nramp1, NOD1, NOD2, TLR1, TLR2, TLR3, TLR4, TLR5, TLR6, TLR7, and TLR9) in canine monocyte-derived macrophages from Leishmania-free dogs. Additionally, secretion of cytokines (IL-10, IL-12, TNF-α and IFN-γ) and nitric oxide in culture supernatants of macrophages with higher or lower resistance to intracellular survival of Leishmania infantum was also measured. Constitutive transcription of TLR9 and NOD2 were negligible; NOD1, TLR1, and TLR7 had low levels of transcription, whereas Nramp1 and TLR2, 3, 4, 5, and 6 had higher levels of constitutive transcription in canine monocyte-derived macrophages. There were no significant differences in transcription between macrophages with higher or lower resistance to intracellular survival of L. infantum. Secretion of TNF-α was higher in more resistant macrophages (designated as resistant) at 24h after infection when compared to less resistant macrophages (designated as susceptible), as well as the secretion of IFN-γ at 72 h post infection. Secretion of IL-10 was lower in resistant macrophages at 24h after infection. No detectable production of nitric oxide was observed. Interestingly, there was a negative correlation between NOD2 transcript levels and intracellular survival of L. infantum in resistant macrophages. This study demonstrated that decreased intracellular survival of L. infantum in canine macrophages was associated with increased production of TNF-α and IFN-γ and decreased production of IL-10; and that constitutive transcription of Nramp1, TLR and NLR does not interfere in intracellular survival of L. infantum.

First identification of canine distemper virus in hoary fox (Lycalopex vetulus): pathologic aspects and virus phylogeny.

Canine distemper virus (CDV) has been reported in several wild animal species, but there have been no reports of CDV in hoary fox (Lycalopex vetulus). This paper characterizes the first case of natural CDV infection in hoary fox, including the clinical and pathologic aspects of the disease as well as the viral strain phylogeny.