The Impact of SIV-Induced Immunodeficiency on Clinical Manifestation, Immune Response, and Viral Dynamics in SARS-CoV-2 Coinfection

Persistent and uncontrolled SARS-CoV-2 replication in immunocompromised individuals has been observed and may be a contributing source of novel viral variants that continue to drive the pandemic. Importantly, the effects of immunodeficiency associated with chronic HIV infection on COVID-19 disease and viral persistence have not been directly addressed in a controlled setting. Here we conducted a pilot study wherein two pigtail macaques (PTM) chronically infected with SIVmac239 were exposed to SARS-CoV-2 and monitored for six weeks for clinical disease, viral replication, and viral evolution, and compared to our previously published cohort of SIV-naïve PTM infected with SARS-CoV-2. At the time of SARS-CoV-2 infection, one PTM had minimal to no detectable CD4+ T cells in gut, blood, or bronchoalveolar lavage (BAL), while the other PTM harbored a small population of CD4+ T cells in all compartments. Clinical signs were not observed in either PTM; however, the more immunocompromised PTM exhibited a progressive increase in pulmonary infiltrating monocytes throughout SARS-CoV-2 infection. Single-cell RNA sequencing (scRNAseq) of the infiltrating monocytes revealed a less activated/inert phenotype. Neither SIV-infected PTM mounted detectable anti-SARS-CoV-2 T cell responses in blood or BAL, nor anti-SARS-CoV-2 neutralizing antibodies. Interestingly, despite the diminished cellular and humoral immune responses, SARS-CoV-2 viral kinetics and evolution were indistinguishable from SIV-naïve PTM in all sampled mucosal sites (nasal, oral, and rectal), with clearance of virus by 3-4 weeks post infection. SIV-induced immunodeficiency significantly impacted immune responses to SARS-CoV-2 but did not alter disease progression, viral kinetics or evolution in the PTM model. SIV-induced immunodeficiency alone may not be sufficient to drive the emergence of novel viral variants.

A combined adjuvant approach primes robust germinal center responses and humoral immunity in non-human primates

Adjuvants and antigen delivery kinetics can profoundly influence B cell responses and should be critically considered in rational vaccine design, particularly for difficult neutralizing antibody targets such as human immunodeficiency virus (HIV). Antigen kinetics can change depending on the delivery method. To promote extended immunogen bioavailability and to present antigen in a multivalent form, native-HIV Env trimers are modified with short phosphoserine peptide linkers that promote tight binding to aluminum hydroxide (pSer:alum). Here we explore the use of a combined adjuvant approach that incorporates pSer:alum-mediated antigen delivery with potent adjuvants (SMNP, 3M-052) in an extensive head-to-head comparison study with conventional alum to assess germinal center (GC) and humoral immune responses. Priming with pSer:alum plus SMNP induces additive effects that enhance the magnitude and persistence of GCs, which correlate with better GC-TFH cell help. Autologous HIV-neutralizing antibody titers are improved in SMNP-immunized animals after two immunizations. Over 9 months after priming immunization of pSer:alum with either SMNP or 3M-052, robust Env-specific bone marrow plasma cells (BM BPC) are observed. Furthermore, pSer-modification of Env trimer reduce targeting towards immunodominant non-neutralizing epitopes. The study shows that a combined adjuvant approach can augment humoral immunity by modulating immunodominance and shows promise for clinical translation.

Enhanced IL-17 Producing and Maintained Cytolytic Effector Functions of Gut Mucosal CD161+CD8+ T Cells in SIV-Infected Rhesus Macaques

Previous studies have indicated that the loss of CD161-expressing CD4+ Th17 cells is linked to the progression of chronic HIV. These cells are significantly depleted in peripheral blood and gut mucosa of HIV-infected individuals, contributing to inflammation and disruption of the gut barrier. However, the impact of HIV infection on CD161-expressing CD8+ T cells remain unclear. Here, we examined the functions of peripheral blood and mucosal CD161+CD8+ T cells in the macaque model of HIV infection. In contrast to the significant loss of CD161+CD4+ T cells, CD161+CD8+ T cell frequencies were maintained in blood and gut during chronic SIV infection. Furthermore, gut CD161+CD8+ T cells displayed greater IL-17 production and maintained Th1-type and cytolytic functions, contrary to impaired IL-17 and granzyme-B production in CD161+CD4+ T cells of SIV-infected macaques. These results suggest that augmented Th17-type effector functions of CD161+CD8+ T cells during SIV infection is a likely mechanism to compensate for the sustained loss of gut mucosal Th17 cells. Targeting the cytokine and cytolytic effector functions of CD161+CD8+ T cells in the preclinical setting of chronic SIV infection with antiretroviral therapy has implications in the restoration of gut barrier disruption in persons with HIV infection.

Long-primed germinal centres with enduring affinity maturation and clonal migration

Germinal centres are the engines of antibody evolution. Here, using human immunodeficiency virus (HIV) Env protein immunogen priming in rhesus monkeys followed by a long period without further immunization, we demonstrate germinal centre B (BGC) cells that last for at least 6 months. A 186-fold increase in BGC cells was present by week 10 compared with conventional immunization. Single-cell transcriptional profiling showed that both light- and dark-zone germinal centre states were sustained. Antibody somatic hypermutation of BGC cells continued to accumulate throughout the 29-week priming period, with evidence of selective pressure. Env-binding BGC cells were still 49-fold above baseline at 29 weeks, which suggests that they could remain active for even longer periods of time. High titres of HIV-neutralizing antibodies were generated after a single booster immunization. Fully glycosylated HIV trimer protein is a complex antigen, posing considerable immunodominance challenges for B cells1,2. Memory B cells generated under these long priming conditions had higher levels of antibody somatic hypermutation, and both memory B cells and antibodies were more likely to recognize non-immunodominant epitopes. Numerous BGC cell lineage phylogenies spanning more than the 6-month germinal centre period were identified, demonstrating continuous germinal centre activity and selection for at least 191 days with no further antigen exposure. A long-prime, slow-delivery (12 days) immunization approach holds promise for difficult vaccine targets and suggests that patience can have great value for tuning of germinal centres to maximize antibody responses.

A cellular trafficking signal in the SIV envelope protein cytoplasmic domain is strongly selected for in pathogenic infection

The HIV/SIV envelope glycoprotein (Env) cytoplasmic domain contains a highly conserved Tyr-based trafficking signal that mediates both clathrin-dependent endocytosis and polarized sorting. Despite extensive analysis, the role of these functions in viral infection and pathogenesis is unclear. An SIV molecular clone (SIVmac239) in which this signal is inactivated by deletion of Gly-720 and Tyr-721 (SIVmac239ΔGY), replicates acutely to high levels in pigtail macaques (PTM) but is rapidly controlled. However, we previously reported that rhesus macaques and PTM can progress to AIDS following SIVmac239ΔGY infection in association with novel amino acid changes in the Env cytoplasmic domain. These included an R722G flanking the ΔGY deletion and a nine nucleotide deletion encoding amino acids 734-736 (ΔQTH) that overlaps the rev and tat open reading frames. We show that molecular clones containing these mutations reconstitute signals for both endocytosis and polarized sorting. In one PTM, a novel genotype was selected that generated a new signal for polarized sorting but not endocytosis. This genotype, together with the ΔGY mutation, was conserved in association with high viral loads for several months when introduced into naïve PTMs. For the first time, our findings reveal strong selection pressure for Env endocytosis and particularly for polarized sorting during pathogenic SIV infection in vivo.

The pigtail macaque (Macaca nemestrina) model of COVID-19 reproduces diverse clinical outcomes and reveals new and complex signatures of disease

The novel coronavirus SARS-CoV-2, the causative agent of COVID-19 disease, has killed over five million people worldwide as of December 2021 with infections rising again due to the emergence of highly transmissible variants. Animal models that faithfully recapitulate human disease are critical for assessing SARS-CoV-2 viral and immune dynamics, for understanding mechanisms of disease, and for testing vaccines and therapeutics. Pigtail macaques (PTM, Macaca nemestrina) demonstrate a rapid and severe disease course when infected with simian immunodeficiency virus (SIV), including the development of severe cardiovascular symptoms that are pertinent to COVID-19 manifestations in humans. We thus proposed this species may likewise exhibit severe COVID-19 disease upon infection with SARS-CoV-2. Here, we extensively studied a cohort of SARS-CoV-2-infected PTM euthanized either 6- or 21-days after respiratory viral challenge. We show that PTM demonstrate largely mild-to-moderate COVID-19 disease. Pulmonary infiltrates were dominated by T cells, including CD4+ T cells that upregulate CD8 and express cytotoxic molecules, as well as virus-targeting T cells that were predominantly CD4+. We also noted increases in inflammatory and coagulation markers in blood, pulmonary pathologic lesions, and the development of neutralizing antibodies. Together, our data demonstrate that SARS-CoV-2 infection of PTM recapitulates important features of COVID-19 and reveals new immune and viral dynamics and thus may serve as a useful animal model for studying pathogenesis and testing vaccines and therapeutics.

Co-immunization of DNA and Protein in the Same Anatomical Sites Induces Superior Protective Immune Responses against SHIV Challenge

We compare immunogenicity and protective efficacy of an HIV vaccine comprised of env and gag DNA and Env (Envelope) proteins by co-administration of the vaccine components in the same muscles or by separate administration of DNA + protein in contralateral sites in female rhesus macaques. The 6-valent vaccine includes gp145 Env DNAs, representing six sequentially isolated Envs from the HIV-infected individual CH505, and matching GLA-SE-adjuvanted gp120 Env proteins. Interestingly, only macaques in the co-administration vaccine group are protected against SHIV CH505 acquisition after repeated low-dose intravaginal challenge and show 67% risk reduction per exposure. Macaques in the co-administration group develop higher Env-specific humoral and cellular immune responses. Non-neutralizing Env antibodies, ADCC, and antibodies binding to FcγRIIIa are associated with decreased transmission risk. These data suggest that simultaneous recognition, processing, and presentation of DNA + Env protein in the same draining lymph nodes play a critical role in the development of protective immunity.

Zika virus infection during pregnancy protects against secondary infection in the absence of CD8+ cells

While T cell immunity is an important component of the immune response to Zika virus (ZIKV) infection generally, the efficacy of these responses during pregnancy remains unknown. Here, we tested the capacity of CD8 lymphocytes to protect from secondary challenge in four macaques, two of which were depleted of CD8⁺ cells prior to rechallenge with a heterologous ZIKV isolate. The initial challenge during pregnancy produced transcriptional signatures suggesting complex patterns of immune modulation as well as neutralizing antibodies that persisted until rechallenge, which all animals efficiently controlled, demonstrating that the primary infection conferred adequate protection. The secondary challenge promoted activation of innate and adaptive immune cells, possibly suggesting a brief period of infection prior to clearance. These data confirm that ZIKV infection during pregnancy induces sufficient immunity to protect from a secondary challenge and suggest that this protection is not dependent on CD8 T cells.

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Zika infection during pregnancy provides protection from secondary infection.

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CD8 T cell responses are not needed for protection from secondary infection.

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Zika infection during pregnancy results in immunomodulatory transcriptional signatures but little IFN response.

Postnatal Zika virus infection of nonhuman primate infants born to mothers infected with homologous Brazilian Zika virus

Recent data in a nonhuman primate model showed that infants postnatally infected with Zika virus (ZIKV) were acutely susceptible to high viremia and neurological damage, suggesting the window of vulnerability extends beyond gestation. In this pilot study, we addressed the susceptibility of two infant rhesus macaques born healthy to dams infected with Zika virus during pregnancy. Passively acquired neutralizing antibody titers dropped below detection limits between 2 and 3 months of age, while binding antibodies remained detectable until viral infection at 5 months. Acute serum viremia was comparatively lower than adults infected with the same Brazilian isolate of ZIKV (n = 11 pregnant females, 4 males, and 4 non-pregnant females). Virus was never detected in cerebrospinal fluid nor in neural tissues at necropsy two weeks after infection. However, viral RNA was detected in lymph nodes, confirming some tissue dissemination. Though protection was not absolute and our study lacks an important comparison with postnatally infected infants born to naïve dams, our data suggest infants born healthy to infected mothers may harbor a modest but important level of protection from postnatally acquired ZIKV for several months after birth, an encouraging result given the potentially severe infection outcomes of this population.

Fetal demise and failed antibody therapy during Zika virus infection of pregnant macaques

Zika virus (ZIKV) infection of pregnant women is associated with pathologic complications of fetal development. Here, we infect pregnant rhesus macaques (Macaca mulatta) with a minimally passaged ZIKV isolate from Rio de Janeiro, where a high rate of fetal development complications was observed. The infection of pregnant macaques with this virus results in maternal viremia, virus crossing into the amniotic fluid (AF), and in utero fetal deaths. We also treated three additional ZIKV-infected pregnant macaques with a cocktail of ZIKV-neutralizing human monoclonal antibodies (nmAbs) at peak viremia. While the nmAbs can be effective in clearing the virus from the maternal sera of treated monkeys, it is not sufficient to clear ZIKV from AF. Our report suggests that ZIKV from Brazil causes fetal demise in non-human primates (NHPs) without additional mutations or confounding co-factors. Treatment with a neutralizing anti-ZIKV nmAb cocktail is insufficient to fully stop vertical transmission.

Zika virus (ZIKV) infection in pregnant women has been associated with fetal developmental defects. Here, the authors show that a Brazilian ZIKV isolate causes fetal demise in non-human primates and that antibody treatment at time of peak viremia is insufficient to clear ZIKV replication from amniotic fluid.

Derivation and Characterization of a CD4-Independent, Non-CD4-Tropic Simian Immunodeficiency Virus

CD4 tropism is conserved among all primate lentiviruses and likely contributes to viral pathogenesis by targeting cells that are critical for adaptive antiviral immune responses. Although CD4-independent variants of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) have been described that can utilize the coreceptor CCR5 or CXCR4 in the absence of CD4, these viruses typically retain their CD4 binding sites and still can interact with CD4. We describe the derivation of a novel CD4-independent variant of pathogenic SIVmac239, termed iMac239, that was used to derive an infectious R5-tropic SIV lacking a CD4 binding site. Of the seven mutations that differentiate iMac239 from wild-type SIVmac239, a single change (D178G) in the V1/V2 region was sufficient to confer CD4 independence in cell-cell fusion assays, although other mutations were required for replication competence. Like other CD4-independent viruses, iMac239 was highly neutralization sensitive, although mutations were identified that could confer CD4-independent infection without increasing its neutralization sensitivity. Strikingly, iMac239 retained the ability to replicate in cell lines and primary cells even when its CD4 binding site had been ablated by deletion of a highly conserved aspartic acid at position 385, which, for HIV-1, plays a critical role in CD4 binding. iMac239, with and without the D385 deletion, exhibited an expanded host range in primary rhesus peripheral blood mononuclear cells that included CCR5(+) CD8(+) T cells. As the first non-CD4-tropic SIV, iMac239-ΔD385 will afford the opportunity to directly assess the in vivo role of CD4 targeting on pathogenesis and host immune responses.

IMPORTANCE

CD4 tropism is an invariant feature of primate lentiviruses and likely plays a key role in pathogenesis by focusing viral infection onto cells that mediate adaptive immune responses and in protecting virions attached to cells from neutralizing antibodies. Although CD4-independent viruses are well described for HIV and SIV, these viruses characteristically retain their CD4 binding site and can engage CD4 if available. We derived a novel CD4-independent, CCR5-tropic variant of the pathogenic molecular clone SIVmac239, termed iMac239. The genetic determinants of iMac239's CD4 independence provide new insights into mechanisms that underlie this phenotype. This virus remained replication competent even after its CD4 binding site had been ablated by mutagenesis. As the first truly non-CD4-tropic SIV, lacking the capacity to interact with CD4, iMac239 will provide the unique opportunity to evaluate SIV pathogenesis and host immune responses in the absence of the immunomodulatory effects of CD4(+) T cell targeting and infection.

Elite Control, Gut CD4 T Cell Sparing, and Enhanced Mucosal T Cell Responses in Macaca nemestrina Infected by a Simian Immunodeficiency Virus Lacking a gp41 Trafficking Motif

Deletion of Gly-720 and Tyr-721 from a highly conserved GYxxØ trafficking signal in the SIVmac239 envelope glycoprotein cytoplasmic domain, producing a virus termed ΔGY, leads to a striking perturbation in pathogenesis in rhesus macaques (Macaca mulatta). Infected macaques develop immune activation and progress to AIDS, but with only limited and transient infection of intestinal CD4(+) T cells and an absence of microbial translocation. Here we evaluated ΔGY in pig-tailed macaques (Macaca nemestrina), a species in which SIVmac239 infection typically leads to increased immune activation and more rapid progression to AIDS than in rhesus macaques. In pig-tailed macaques, ΔGY also replicated acutely to high peak plasma RNA levels identical to those for SIVmac239 and caused only transient infection of CD4(+) T cells in the gut lamina propria and no microbial translocation. However, in marked contrast to rhesus macaques, 19 of 21 pig-tailed macaques controlled ΔGY replication with plasma viral loads of <15 to 50 RNA copies/ml. CD4(+) T cells were preserved in blood and gut for up to 100 weeks with no immune activation or disease progression. Robust antiviral CD4(+) T cell responses were seen, particularly in the gut. Anti-CD8 antibody depletion demonstrated CD8(+) cellular control of viral replication. Two pig-tailed macaques progressed to disease with persisting viremia and possible compensatory mutations in the cytoplasmic tail. These studies demonstrate a marked perturbation in pathogenesis caused by ΔGY's ablation of the GYxxØ trafficking motif and reveal, paradoxically, that viral control is enhanced in a macaque species typically predisposed to more pathogenic manifestations of simian immunodeficiency virus (SIV) infection.

IMPORTANCE

The pathogenesis of human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV) reflects a balance between viral replication, host innate and adaptive antiviral immune responses, and sustained immune activation that in humans and Asian macaques is associated with persistent viremia, immune escape, and AIDS. Among nonhuman primates, pig-tailed macaques following SIV infection are predisposed to more rapid disease progression than are rhesus macaques. Here, we show that disruption of a conserved tyrosine-based cellular trafficking motif in the viral transmembrane envelope glycoprotein cytoplasmic tail leads in pig-tailed macaques to a unique phenotype in which high levels of acute viral replication are followed by elite control, robust cellular responses in mucosal tissues, and no disease. Paradoxically, control of this virus in rhesus macaques is only partial, and progression to AIDS occurs. This novel model should provide a powerful tool to help identify host-specific determinants for viral control with potential relevance for vaccine development.

miR-190b is markedly upregulated in the intestine in response to simian immunodeficiency virus replication and partly regulates myotubularin-related protein-6 expression

HIV replication and the cellular micro-RNA (miRNA) machinery interconnect at several posttranscriptional levels. To understand their regulatory role in the intestine, a major site of HIV/SIV replication, dissemination, and CD4(+) T cell depletion, we profiled miRNA expression in colon following SIV infection (10 acute SIV, 5 uninfected). Nine (four up and five down) miRNAs showed statistically significant differential expression. Most notably, miR-190b expression showed high statistical significance (adjusted p = 0.0032), the greatest fold change, and was markedly elevated in colon and jejunum throughout SIV infection. In addition, miR-190b upregulation was detected before peak viral replication and the nadir of CD4(+) T cell depletion predominantly in lamina propria leukocytes. Interestingly non-SIV-infected macaques with diarrhea and colitis failed to upregulate miR-190b, suggesting that its upregulation was neither inflammation nor immune-activation driven. SIV infection of in vitro-cultured CD4(+) T cells and primary intestinal macrophages conclusively identified miR-190b upregulation to be driven in response to viral replication. Further miR-190b expression levels in colon and jejunum positively correlated with tissue viral loads. In contrast, mRNA expression of myotubularin-related protein 6 (MTMR6), a negative regulator of CD4(+) T cell activation/proliferation, significantly decreased in SIV-infected macrophages. Luciferase reporter assays confirmed MTMR6 as a direct miR-190b target. To our knowledge, this is the first report, which describes dysregulated miRNA expression in the intestine, that identifies a potentially significant role for miR-190b in HIV/SIV pathogenesis. More importantly, miR-190b-mediated MTMR6 downregulation suggests an important mechanism that could keep infected cells in an activated state, thereby promoting viral replication. In the future, the mechanisms driving miR-190b upregulation including other cellular processes it regulates in SIV-infected cells need determination.

Focused examination of the intestinal epithelium reveals transcriptional signatures consistent with disturbances in enterocyte maturation and differentiation during the course of SIV infection

The Gastrointestinal (GI) tract plays a pivotal role in AIDS pathogenesis as it is the primary site for viral transmission, replication and CD4⁺ T cell destruction. Accordingly, GI disease (enteropathy) has become a well-known complication and a driver of AIDS progression. To better understand the molecular mechanisms underlying GI disease we analyzed global gene expression profiles sequentially in the intestinal epithelium of the same animals before SIV infection and at 21 and 90 days post infection (DPI). More importantly we obtained sequential excisional intestinal biopsies and examined distinct mucosal components (epithelium. intraepithelial lymphocytes, lamina propria lymphocytes, fibrovascular stroma) separately. Here we report data pertaining to the epithelium. Overall genes associated with epithelial cell renewal/proliferation/differentiation, permeability and adhesion were significantly down regulated (<1.5–7 fold) at 21 and 90DPI. Genes regulating focal adhesions (n = 6), gap junctions (n = 3), ErbB (n = 3) and Wnt signaling (n = 4) were markedly down at 21DPI and the number of genes in each of these groups that were down regulated doubled between 21 and 90DPI. Notable genes included FAK, ITGA6, PDGF, TGFβ3, Ezrin, FZD6, WNT10A, and TCF7L2. In addition, at 90DPI genes regulating ECM-receptor interactions (laminins and ITGB1), epithelial cell gene expression (PDX1, KLF6), polarity/tight junction formation (PARD3B&6B) and histone demethylase (JMJD3) were also down regulated. In contrast, expression of NOTCH3, notch target genes (HES4, HES7) and EZH2 (histone methyltransferase) were significantly increased at 90DPI. The altered expression of genes linked to Wnt signaling together with decreased expression of PDX1, PARD3B, PARD6B and SDK1 suggests marked perturbations in intestinal epithelial function and homeostasis leading to breakdown of the mucosal barrier. More importantly, the divergent expression patterns of EZH2 and JMJD3 suggests that an epigenetic mechanism involving histone modifications may contribute to the massive decrease in gene expression at 90DPI leading to defects in enterocyte maturation and differentiation.

Gluten-sensitive enteropathy coincides with decreased capability of intestinal T cells to secrete IL-17 and IL-22 in a macaque model for celiac disease

Celiac disease (CD) is an autoimmune disorder caused by intolerance to dietary gluten. The interleukin (IL)-17 and IL-22 function as innate regulators of mucosal integrity. Impaired but not well-understood kinetics of the IL-17/22 secretion was described in celiac patients. Here, the IL-17 and IL-22-producing intestinal cells were studied upon their in vitro stimulation with mitogens in class II major histocompatibility complex-defined, gluten-sensitive rhesus macaques. Pediatric biopsies were collected from distal duodenum during the stages of disease remission and relapse. Regardless of dietary gluten content, IL-17 and IL-22-producing cells consisted of CD4+ and CD8+ T lymphocytes as well as of lineage-negative (Lin-) cells. Upon introduction of dietary gluten, capability of intestinal T cells to secrete IL-17/22 started to decline (p<0.05), which was paralleled with gradual disruption of epithelial integrity. These data indicate that IL-17/22-producing cells play an important role in maintenance of intestinal mucosa in gluten-sensitive primates.

S100β as a novel and accessible indicator for the presence of monocyte-driven encephalitis in AIDS

AIMS

The pathogenesis of human/simian immunodeficiency virus encephalitis (HIVE/SIVE) remains incompletely understood, but is associated with alterations in the blood-brain barrier. At present, it is not possible to easily determine if an individual has HIVE/SIVE before post mortem examination.

METHODS

We have examined serum levels of the astroglial protein S100β in SIV-infected macaques and show that it can be used to determine which animals have SIVE. We also checked for correlations with inflammatory markers such as CCL2/MCP-1, IL-6 and C-reactive protein.

RESULTS

We found that increased S100β protein in serum correlated with decreased expression of the tight junction protein zonula occludens-1 on brain microvessels. Furthermore, the decrease in zonula occludens-1 expression was spatially related to SIVE lesions and perivascular deposition of plasma fibrinogen. There was no correlation between encephalitis and plasma levels of IL-6, MCP-1/CCL2 or C-reactive protein.

CONCLUSIONS

Together, these data indicate that SIVE lesions are associated with vascular leakage that can be determined by S100β protein in the periphery. The ability to simply monitor the presence of SIVE will greatly facilitate studies of the neuropathogenesis of AIDS.

Focused examination of the intestinal lamina propria yields greater molecular insight into mechanisms underlying SIV induced immune dysfunction

Background

The Gastrointestinal (GI) tract is critical to AIDS pathogenesis as it is the primary site for viral transmission and a major site of viral replication and CD4⁺ T cell destruction. Consequently GI disease, a major complication of HIV/SIV infection can facilitate translocation of lumenal bacterial products causing localized/systemic immune activation leading to AIDS progression.

Methodology/Principal Findings

To better understand the molecular mechanisms underlying GI disease we analyzed global gene expression profiles sequentially in the intestine of the same animals prior to and at 21 and 90d post SIV infection (PI). More importantly we maximized information gathering by examining distinct mucosal components (intraepithelial lymphocytes, lamina propria leukocytes [LPL], epithelium and fibrovascular stroma) separately. The use of sequential intestinal resections combined with focused examination of distinct mucosal compartments represents novel approaches not previously attempted. Here we report data pertaining to the LPL. A significant increase (±1.7-fold) in immune defense/inflammation, cell adhesion/migration, cell signaling, transcription and cell division/differentiation genes were observed at 21 and 90d PI. Genes associated with the JAK-STAT pathway (IL21, IL12R, STAT5A, IL10, SOCS1) and T-cell activation (NFATc1, CDK6, Gelsolin, Moesin) were notably upregulated at 21d PI. Markedly downregulated genes at 21d PI included IL17D/IL27 and IL28B/IFNγ3 (anti-HIV/viral), activation induced cytidine deaminase (B-cell function) and approximately 57 genes regulating oxidative phosphorylation, a critical metabolic shift associated with T-cell activation. The 90d transcriptome revealed further augmentation of inflammation (CXCL11, chitinase-1, JNK3), immune activation (CD38, semaphorin7A, CD109), B-cell dysfunction (CD70), intestinal microbial translocation (Lipopolysaccharide binding protein) and mitochondrial antiviral signaling (NLRX1) genes. Reduced expression of CD28, CD4, CD86, CD93, NFATc1 (T-cells), TLR8, IL8, CCL18, DECTIN1 (macrophages), HLA-DOA and GPR183 (B-cells) at 90d PI suggests further deterioration of overall immune function.

Conclusions/Significance

The reported transcriptional signatures provide significant new details on the molecular pathology of HIV/SIV induced GI disease and provide new opportunity for future investigation.

SIV antigen immunization induces transient antigen-specific T cell responses and selectively activates viral replication in draining lymph nodes in retroviral suppressed rhesus macaques

Background

HIV infection causes a qualitative and quantitative loss of CD4⁺ T cell immunity. The institution of anti-retroviral therapy (ART) restores CD4⁺ T cell responses to many pathogens, but HIV-specific responses remain deficient. Similarly, therapeutic immunization with HIV antigens of chronically infected, ART treated subjects results in poor induction of HIV-specific CD4 responses. In this study, we used a macaque model of ART treatment during chronic infection to study the virologic consequences of SIV antigen stimulation in lymph nodes early after immunization. Rhesus CMV (RhCMV) seropositive, Mamu A*01 positive rhesus macaques were chronically infected with SIVmac251 and treated with ART. The immune and viral responses to SIV gag and RhCMV pp65 antigen immunization in draining lymph nodes and peripheral blood were analyzed. Animals were immunized on contralateral sides with SIV gag and RhCMV pp65 encoding plasmids, which allowed lymph nodes draining each antigen to be obtained at the same time from the same animal for direct comparison.

Results

We observed that both SIV and RhCMV immunizations stimulated transient antigen-specific T cell responses in draining lymph nodes. The RhCMV-specific responses were potent and sustained (50 days post-immunization) in the periphery, while the SIV-specific responses were transient and extinguished quickly. The SIV antigen stimulation selectively induced transient SIV replication in draining lymph nodes.

Conclusions

The data are consistent with a model whereby viral replication in response to SIV antigen stimulation limits the generation of SIV antigen-specific responses and suggests a potential mechanism for the early loss and poor HIV-specific CD4⁺ T cell response observed in HIV-infected individuals.

Engineering HIV-resistant human CD4+ T cells with CXCR4-specific zinc-finger nucleases

HIV-1 entry requires the cell surface expression of CD4 and either the CCR5 or CXCR4 coreceptors on host cells. Individuals homozygous for the ccr5Δ32 polymorphism do not express CCR5 and are protected from infection by CCR5-tropic (R5) virus strains. As an approach to inactivating CCR5, we introduced CCR5-specific zinc-finger nucleases into human CD4+ T cells prior to adoptive transfer, but the need to protect cells from virus strains that use CXCR4 (X4) in place of or in addition to CCR5 (R5X4) remains. Here we describe engineering a pair of zinc finger nucleases that, when introduced into human T cells, efficiently disrupt cxcr4 by cleavage and error-prone non-homologous DNA end-joining. The resulting cells proliferated normally and were resistant to infection by X4-tropic HIV-1 strains. CXCR4 could also be inactivated in ccr5Δ32 CD4+ T cells, and we show that such cells were resistant to all strains of HIV-1 tested. Loss of CXCR4 also provided protection from X4 HIV-1 in a humanized mouse model, though this protection was lost over time due to the emergence of R5-tropic viral mutants. These data suggest that CXCR4-specific ZFNs may prove useful in establishing resistance to CXCR4-tropic HIV for autologous transplant in HIV-infected individuals.

Improved xenobiotic metabolism and reduced susceptibility to cancer in gluten-sensitive macaques upon introduction of a gluten-free diet

BACKGROUND

A non-human primate (NHP) model of gluten sensitivity was employed to study the gene perturbations associated with dietary gluten changes in small intestinal tissues from gluten-sensitive rhesus macaques (Macaca mulatta).

METHODOLOGY

Stages of remission and relapse were accomplished in gluten-sensitive animals by administration of gluten-free (GFD) and gluten-containing (GD) diets, as described previously. Pin-head-sized biopsies, obtained non-invasively by pediatric endoscope from duodenum while on GFD or GD, were used for preparation of total RNA and gene profiling, using the commercial Rhesus Macaque Microarray (Agilent Technologies),targeting expression of over 20,000 genes.

PRINCIPAL FINDINGS

When compared with normal healthy control, gluten-sensitive macaques showed differential gene expressions induced by GD. While observed gene perturbations were classified into one of 12 overlapping categories--cancer, metabolism, digestive tract function, immune response, cell growth, signal transduction, autoimmunity, detoxification of xenobiotics, apoptosis, actin-collagen deposition, neuronal and unknown function--this study focused on cancer-related gene networks such as cytochrome P450 family (detoxification function) and actin-collagen-matrix metalloproteinases (MMP) genes.

CONCLUSIONS/SIGNIFICANCE

A loss of detoxification function paralleled with necessity to metabolize carcinogens was revealed in gluten-sensitive animals while on GD. An increase in cancer-promoting factors and a simultaneous decrease in cancer-preventing factors associated with altered expression of actin-collagen-MMP gene network were noted. In addition, gluten-sensitive macaques showed reduced number of differentially expressed genes including the cancer-associated ones upon withdrawal of dietary gluten. Taken together, these findings indicate potentially expanded utility of gluten-sensitive rhesus macaques in cancer research.

Neurokinin-1 receptor (NK1-R) expression in the brains of SIV-infected rhesus macaques: implications for substance P in NK1-R immune cell trafficking into the CNS

Recent studies suggest a link between neuropsychiatric disorders and HIV/SIV infection. Most evidence indicates that monocytes/macrophages are the primary cell type infected within the CNS and that they contribute to CNS inflammation and neurological disease. Substance P (SP), a pleotropic neuropeptide implicated in inflammation, depression, and immune modulation via interaction with its cognate receptor, the neurokinin 1 receptor (NK1-R), is produced by monocyte/macrophages. While the presence of NK1-R on neurons is well known, its role on cells of the immune system such as monocyte/macrophages is just beginning to emerge. Therefore, we have examined the expression of SP and NK1-R and their relationship to SIV/HIV encephalitis (SIVE/HIVE) lesions and SIV-infected cells. These studies demonstrated intense expression of SP and NK1-R in SIVE lesions, with macrophages being the principal cell expressing NK1-R. Interestingly, all of the SIV-infected macrophages expressed NK1-R. Additionally, we examined the functional role of SP as a proinflammatory mediator of monocyte activation and chemotaxis. These studies demonstrated that treatment of monocytes with SP elicited changes in cell-surface expression for CCR5 and NK1-R in a dose-dependent manner. Moreover, pretreatment with SP enhanced both SP- and CCL5-mediated chemotaxis. All of these findings suggest that SP and NK1-R are important in SIV infection of macrophages and the development of SIVE lesions.

Rabies virus-based vaccines elicit neutralizing antibodies, poly-functional CD8+ T cell, and protect rhesus macaques from AIDS-like disease after SIV(mac251) challenge

Highly attenuated rabies virus (RV) vaccine vectors were evaluated for their ability to protect against highly pathogenic SIV(mac251) challenge. Mamu-A*01 negative rhesus macaques were immunized in groups of four with either: RV expressing SIV(mac239)-GagPol, a combination of RV expressing SIV(mac239)-Env and RV expressing SIV(mac239)-GagPol, or with empty RV vectors. Eight weeks later animals received a booster immunization with a heterologous RV expressing the same antigens. At 12 weeks post-boost, all animals were challenged intravenously with 100 TCID(50) of pathogenic SIV(mac251-CX). Immunized macaques in both vaccine groups had 1.3-1.6-log-fold decrease in viral set point compared to control animals. The GagPol/Env immunized animals also had a significantly lower peak viral load. When compared to control animals following challenge, vaccinated macaques had a more rapid induction of SIV(mac251) neutralizing antibodies and of CD8(+) T cell responses to various SIV epitopes. Moreover, vaccinated macaques better maintained peripheral memory CD4(+) T cells and were able to mount a poly-functional CD8(+) T cell response in the mucosa. These findings indicate promise for RV-based vectors and have important implications for the development of an efficacious HIV vaccine.

CCAAT/enhancer binding protein beta is a major mediator of inflammation and viral replication in the gastrointestinal tract of simian immunodeficiency virus-infected rhesus macaques

The gastrointestinal tract (GIT) is a major target of infection with human immunodeficiency virus (HIV) and simian immunodeficiency virus (SIV). Chronic GIT disease and inflammation are common sequelae to HIV/SIV infection. Nonetheless, the molecular mechanisms that cause and maintain GIT dysfunction remain unclear. We investigated the contribution of CCAAT/enhancer-binding protein beta (C/EBPbeta) to GIT disease and viral replication in jejunum and colon collected at necropsy from 12 SIV-infected (group 1), or 10 uninfected macaques with chronic diarrhea (group 2), and 9 uninfected control macaques (group 3). All group 1 and 2 macaques had chronic diarrhea, wasting, and colitis, but group 1 animals had more severe lesions in the jejunum. C/EBPbeta gene expression increased significantly in colon of groups 1 and 2 and in jejunum of only group 1 macaques compared with controls. In group 1 animals, CEBPbeta expression was localized predominantly to macrophages and occasionally lymphocytes. Chromatin immunoprecipitation assays confirmed the binding of C/EBPbeta and p65 to the SIV long terminal repeat region in colonic lamina propria cells, suggesting a mechanistic link between inflammation and activation of viral replication in vivo. This is the first in vivo study describing the transcriptional changes and immunophenotypic localization of C/EBPbeta in the GIT of SIV-infected macaques. More importantly, these data provide a molecular mechanism for persistent inflammation and immune activation leading to increased SIV burden and GIT pathology in SIV-infected macaques and perhaps HIV-infected individuals.

Gastrointestinal disease in simian immunodeficiency virus-infected rhesus macaques is characterized by proinflammatory dysregulation of the interleukin-6-Janus kinase/signal transducer and activator of transcription3 pathway

Gastrointestinal disease and inflammation are common sequelae of human and simian immunodeficiency virus (SIV) infection. Nevertheless, the molecular mechanisms that lead to gastrointestinal dysfunction remain unclear. We investigated regulation of the interleukin (IL)-6-JAK-STAT3 pathway in jejunum and colon, collected at necropsy, from 10 SIV-infected macaques with diarrhea (group 1), 10 non-SIV-infected macaques with diarrhea (group 2), and 7 control uninfected macaques (group 3). All group 1 and 2 macaques had chronic diarrhea, wasting, and colitis, but group 1 animals had more frequent and severe lesions in the jejunum. A significant increase in IL-6 and SOCS-3 gene expression along with constitutive STAT3 activation was observed in the colon of all group 1 and 2 macaques and in the jejunum of only group 1 macaques compared to controls. Further, in colon, histopathology severity scores correlated significantly with IL-6 (groups 1 and 2) and SOCS-3 (group 2) gene expression. In jejunum, a similar correlation was observed only in group 1 animals. Phosphorylated STAT3 (p-STAT3) was localized to lymphocytes (CD3+) and macrophages (CD68+), with fewer CD3+ lymphocytes expressing p-STAT3 in group 1 macaques. Despite high SOCS-3 expression, STAT3 remained constitutively active, providing a possible explanation for persistent intestinal inflammation and immune activation that may favor viral replication and disease pro-gression.

Single epitope mucosal vaccine delivered via immuno-stimulating complexes induces low level of immunity against simian-HIV

The difficulty in developing an effective vaccine to contain the HIV/AIDS epidemic coupled with the fact that primary HIV-1 infection typically occurs via mucosal sites has increased emphasis on vaccine approaches that protect at mucosal surfaces. In this study we employed HIV and simian-HIV (SHIV)-derived T helper (Th) and cytotoxic T lymphocyte (CTL) single epitopes incorporated into immuno-stimulating complexes (ISCOM) as a candidate immunogens. Immunized rhesus macaques (Macaca mulatta) were challenged with CCR5-tropic SHIV(SF162p4). On the day of challenge, low levels of virus-neutralizing antibodies (Ab) and CTLs were detected in ISCOM-immunized macaques. Greater than 10(5) viral RNA copies per ml of plasma in 2/5 immunized and 3/4 control macaques were detected within 3 weeks post-challenge. Depletion of CD4+ T cells from gut-associated lymphoid tissues (GALT) was observed by post-challenge day (PCD) 14 in all macaques regardless immunization. Nonetheless, lower viral loads and relatively better preservation of peripheral CD4+ T cells following the SHIV infection was observed in ISCOM-immunized macaques. We predict that if coadministered with additional epitopes and/or more efficacious mucosal delivery system or route, HIV/SIV-derived peptide vaccines may have potential to elicit heterologous protection.

Visualizing cytokine-secreting cells in situ in the rhesus macaque model of chronic gut inflammation

Cytokine-producing cells in gut-associated lymphoid tissues of rhesus macaques with chronic enterocolitis were studied. The confocal microscopy technique that we developed enables simultaneous in situ visualization of multiple extra- and/or intracellular antigens at a resolution higher than that allowed by light or epifluorescence microscopy. The presence of interleukin-6 (IL-6)-, tumor necrosis factor alpha (TNF-alpha)-, and IL-1-alpha-producing cells was focally intense in the colon lamina propria of the affected animals. The IL-1-alpha-producing cells were T lymphocytes (CD3+), while the TNF-alpha-producing cells were both macrophages (CD68+/HAM56+/LN5+) and T lymphocytes (CD3+). The IL-6-producing cells within the colon consisted of T lymphocytes and macrophages. The amount of IL-6-producing cells seen in macaques with enterocolitis was significantly higher (P<0.001) than that seen in the healthy control animal, while TNF-alpha- and IL-1-alpha-producing cells were seen only in macaques with enterocolitis. Most of the T lymphocytes that produced cytokines were detected in the lamina propria, while the macrophages were most prominent in highly inflamed regions of the lamina propria. Taken together, our findings indicate that there might be immunological similarity between chronic enterocolitis of rhesus macaques and humans, suggesting the potential use of the nonhuman primate model for the validation of novel therapies.

Development of a rotavirus-shedding model in rhesus macaques, using a homologous wild-type rotavirus of a new P genotype

Although there are several reports on rotavirus inoculation of nonhuman primates, no reliable model exists. Therefore, this study was designed to develop a rhesus macaque model for rotavirus studies. The goals were to obtain a wild-type macaque rotavirus and evaluate it as a challenge virus for model studies. Once rotavirus was shown to be endemic within the macaque colony at the Tulane National Primate Research Center, stool specimens were collected from juvenile animals (2.6 to 5.9 months of age) without evidence of previous rotavirus infection and examined for rotavirus antigen. Six of 10 animals shed rotavirus during the 10-week collection period, and the electropherotypes of all isolates were identical to each other but distinct from those of prototype simian rotaviruses. These viruses were characterized as serotype G3 and subgroup 1, properties typical of many animal rotaviruses, including simian strains. Nucleotide sequence analysis of the VP4 gene was performed with a culture-grown isolate from the stool of one animal, designated the TUCH strain. Based on both genotypic and phylogenetic comparisons between TUCH VP4 and cognate proteins of representatives of the reported 22 P genotypes, the TUCH virus belongs to a new genotype, P[23]. A pool of wild-type TUCH was prepared and intragastrically administered to eight cesarean section-derived, specific-pathogen-free macaques 14 to 42 days of age. All animals were kept in a biocontainment level 2 facility. Although no diarrhea was observed and the animals remained clinically normal, all animals shed large quantities of rotavirus antigen in their feces after inoculation, which resolved by the end of the 14-day observation period. Therefore, TUCH infection of macaques provides a useful nonhuman primate model for studies on rotavirus protection.

Defining T-cell-mediated immune responses in rotavirus-infected juvenile rhesus macaques

The appearance of virus-specific CD4(+) and/or CD8(+) T lymphocytes in peripheral blood of captive juvenile rhesus macaques (Macaca mulatta) was observed following rotavirus infection. These cell-mediated immune responses were measured following experimental or natural infection after rotavirus was isolated from stool specimens of asymptomatic animals. The virus isolated was a new strain of simian rotavirus that we named TUCH (for Tulane University and Cincinnati Children's Hospital). Restimulation of peripheral T lymphocytes by inactivated double- or triple-layered TUCH rotavirus particles containing either VP6 or VP4 and VP7 on their respective surfaces resulted in increased quantities of interleukin-6 (IL-6) and IL-12 in cell culture supernatants. Recall responses to rotavirus by CD4(+) and CD8(+) T lymphocytes were associated with accumulation of intracellular IL-6 and gamma interferon. Antigen presentation of TUCH rotavirus to lymphocytes was mediated via differentiated cultures of monocyte-derived dendritic (HLA-DR(+)) cells. This is the first report demonstrating cell-mediated immune responses to rotavirus in nonhuman primates. Further exploration of rhesus macaques in vaccine trials with human rotavirus vaccine candidates is the major objective of future studies.

Infectious agent and immune response characteristics of chronic enterocolitis in captive rhesus macaques

Chronic enterocolitis is the leading cause of morbidity in colonies of captive rhesus macaques (Macaca mulatta). This study's aim was to identify the common enteric pathogens frequently associated with chronic enterocolitis in normal, immunocompetent rhesus monkeys and to elucidate the influence of this clinical syndrome on the host immune system. We analyzed the fecal specimens from 100 rhesus macaques with or without clinical symptoms of chronic diarrhea. Retrospective analysis revealed an increased incidence of Campylobacter spp. (Campylobacter coli and Campylobacter jejuni), Shigella flexneri, Yersinia enterocolitica, adenovirus, and Strongyloides fulleborni in samples collected from animals with chronic diarrhea (P < 0.05). The presence of additional enteric pathogens, such as Escherichia coli, carrying the eaeA intimin or Stx2c Shiga toxin virulence genes, Balantidium coli, Giardia lamblia, Enterocytozoon bieneusi, and Trichuris trichiura was found in all animals regardless of whether diarrhea was present. In addition, the upregulation of interleukin-1 alpha (IL-1 alpha), IL-3, and tumor necrosis factor alpha cytokine genes, accompanied by an increased presence of activated (CD4(+) CD69(+)) T lymphocytes was found in gut-associated lymphoid tissues collected from animals with chronic enterocolitis and diarrhea in comparison with clinically healthy controls (P < 0.05). These data indicate that chronic enterocolitis and diarrhea are associated, in part, with a variety of enteric pathogens and highlight the importance of defining the microbiological status of nonhuman primates used for infectious disease studies. The data also suggest that chronic colitis in rhesus macaques may have potential as a model of inflammatory bowel disease in humans.

Quantitative evaluation of Enterocytozoon bieneusi infection in simian immunodeficiency virus-infected rhesus monkeys

The association of the microsporidia Enterocytozoon bieneusi with chronic diarrhea and wasting in individuals with acquired immunodeficiency syndrome (AIDS) has been demonstrated. The disease caused by E. bieneusi has been linked to decreased levels of circulating CD4+ T lymphocytes. In this study, we investigated the relationship between the extent of excretion of E. bieneusi in feces of simian immunodeficiency virus (SIV)-infected juvenile macaques and the CD4+ T lymphocyte counts in the peripheral blood. Twelve juvenile rhesus monkeys (Macaca mulatta) were intravenously inoculated with the pathogenic molecular clone SIVmac239. Numbers of CD4+ T lymphocytes were assessed by three-color flow cytometry. The presence of E. bieneusi DNA in feces was assessed by nested PCR. In addition, selected samples of feces were examined by competitive quantitative PCR to assess the level of E. bieneusi infection. Low (n = 5) to undetectable (n = 7) quantities of E. bieneusi were present in feces of the twelve animals in prior to inoculation with SIV. After SIV inoculation the number of animals shedding E. bieneusi increased (n = 10) as did the quantity of E. bieneusi shedding in the feces. Of the twelve juvenile animals, five animals died within 8 months post-SIV inoculation with symptoms of AIDS. Four of the five deceased animals showed shedding of E. bieneusi DNA in feces (> or =100 spores/g) for at least three consecutive months. Increased number of E. bieneusi in feces was accompanied by decreased counts of circulating CD4+ T lymphocytes and increased SIV plasma viral load.

Prevalence and characteristics of Pasteurella multocida in commercial turkeys

The oropharyngeal regions of 680 meat turkeys and 55 breeder turkeys from nine outbreak farms, three history-outbreak farms, and 19 nonoutbreak farms in Ohio, Indiana, and Pennsylvania were cultured to determine the prevalence of Pasteurella multocida in turkeys. Pasteurella multocida was recovered from 32 out of 105 turkeys belonging to outbreak farms. Pasteurella multocida was not recovered from either history-outbreak or nonoutbreak farms. Characterization via capsular and somatic serotyping, biotyping, restriction endonuclease analysis, and antimicrobial susceptibility testing was performed on all recovered P. multocida isolates. Pasteurella multocida serotype A:1 and somatic serotype 1 with an un-typable capsular serogroup (UT:1) were the most common serogroups found. All isolates belonged to biotype P. multocida ssp. multocida. EcoRI, HpaII, and HindIII restriction enzyme digestions identified three, five, and five restriction fragment length polymorphism profiles, respectively. A majority of the isolates were susceptible to amikacin, ampicillin, ceftiofur, cephalothin, enrofloxacin, florfenicol, gentamicin, neomycin, novobiocin, oxacillin with 2% NaCl, sarafloxacin, tilmicosin, and trimethoprim with sulphadiazine and resistant to clindamicin, penicillin, tiamulin, and tylosin.

The effect of hypovitaminosis A on the pathogenesis of Pasteurella multocida in turkeys

It has been proposed that Pasteurella multocida can invade the host tissues via the mucous membrane. Vitamin A (VitA) deficiency has been associated with mucous membrane damage, such as squamous metaplasia. The objective of this study was to determine the early stages in the pathogenesis of P. multocida in VitA-deficient turkeys and clinically healthy turkeys. Fifteen-week-old VitA-deficient and clinically healthy turkeys were inoculated with P. multocida P-1059, a virulent strain, and the portal of entry, invasion, and localization of P. multocida were studied by microbial examination of the trachea, liver, and lung and histologic examinations of internal organs. Higher mortality was found in VitA-deficient turkeys. Pasteurella multocida was first reisolated from the trachea, secondarily from the liver and blood, and finally from the lung in both groups. Invasion of P. multocida into tissues occurred between 3 hr and 24 hr postinoculation in both groups. Our findings suggest that altered membrane integrity in VitA-deficient birds did not appear to change the time course of the systemic spread of P. multocida infection in turkeys and that the increased mortality seen in the VitA-deficient turkeys may be associated with immune system impairment.

Induction of vitamin A deficiency in turkeys

The objective of this study was to determine the relationship between the hepatic vitamin A (VitA) level and the pathologic changes in the oropharynx and esophagus of VitA-deficient turkeys. Study turkeys were provided with a diet sufficient (11,000 IU/kg) or deficient (2750 IU/kg) in VitA from 4 to 17 wk of age. Body weight, bacterial culture, and tissues from internal organs were collected at weekly intervals. VitA deficiency causes epithelial tissue damage in poultry. This epithelial damage was seen grossly as white plaques in the oropharynx and esophagus and histologically as squamous metaplasia of mucosal glands and keratinization of epithelium. No significant difference in body weights was seen among the groups. Moreover, no pathogenic bacteria was isolated during sampling periods. Liver VitA levels declined significantly after consumption of low VitA diet for 3 wk and were depleted after 5 wk. Squamous metaplasia due to VitA deficiency developed in the esophagus after 3 wk and in the oropharynx after 4 wk of consuming a VitA-deficient diet.

Survey of pathogens and blood parasites in free-living passerines

To determine the disease prevalence of free-living passerines, 1709 passerines were sampled from 38 different field sites in Ohio. Choanal and cloacal swabs were collected from each bird and cultured for the presence of Pasteurella multocida, Salmonella spp., and Escherichia coli by standard microbiologic techniques. In addition, the serum from each bird was analyzed for the presence of antibodies to Mycoplasma gallisepticum, Mycoplasma synoviae, Newcastle disease virus, and avian influenza virus. A blood smear was also made to examine for the presence of blood parasites. Results indicated that the isolation of E. coli varied with bird species, with the European starling having a higher (21.4%) isolation of E. coli. Salmonella spp. were also isolated from these free-living passerines. Pasteurella multocida was not isolated from any of the sampled passerines. These birds did not have antibodies to M. gallisepticum, M. synoviae, Newcastle disease virus, or avian influenza virus. Blood parasites were not detected in any of the birds sampled.

Virulence of raptor-origin Pasteurella multocida in domestic chickens

Pasteurella multocida belonging to somatic serotype 1 and capsular type A has been known to cause avian cholera in domestic poultry. Pasteurella multocida serotype 1 has also been isolated from raptorial birds. However, the capsular type for these raptorial isolates remains unknown. Moreover, the virulence of these raptorial isolates for domestic poultry has not been determined. The objectives of this study were to determine the capsular type of raptorial P. multocida serotype 1 isolates and to determine if these isolates were virulent for domestic chickens. Study chickens were inoculated with one of three P. multocida isolates. Isolate WESO-1 was obtained from a western screech owl (Otus kennicottii) and isolates RTHA-2 and RTHA-4 were isolated from two red-tailed hawks (Buteo jamaicensis). These isolates were given by either the oral, intravenous, or intraocular route. Control birds were given brain-heart infusion broth. The capsular serotypes of three isolates were also determined. The RTHA-2 and RTHA-4 isolates belonged to P. multocida capsular type A. The WESO-1 isolate belonged to capsular type F. Results also demonstrated that, for the isolates examined, the intraocular route did not cause mortality in chickens. There was mortality in all groups for the intravenous route. However, various mortality patterns were observed when P. multocida was given orally for the three different isolates. The RTHA-4 isolate (serotype 1:A) was the most virulent for domestic chickens. The WESO-1 isolate (serotype 1:F) was the least virulent for chickens among the raptorial isolates examined.

Crop impaction resulting from feather ball formation in caged layers

Abnormal behaviors in commercial poultry, including feather pulling and pica, have been known to occur when birds are exposed to an unfamiliar environment. We report here the development of crop impactions resulting from feather ball formation. Twelve specific-pathogen-free (SPF) chickens were placed in one of three cages housed among a commercial layer flock in three different buildings on a farm site. Three weeks after placement, the birds were removed from the cages and given a physical exam. Chickens were thin, and one bird in each of the three caged groups had a palpable mass at the level of the thoracic inlet. At necropsy, a mass was noted in the crop. Upon further dissection, a wet, foul-smelling mass consisting of feathers and feed debris was recovered. Results from our case indicate that unfamiliar surroundings can cause pica in birds. Hence, avian researchers and veterinarians planning to introduce new birds into a flock, i.e., SPF birds, should consider the birds' previous environmental conditions prior to placement because sudden placement in unfamiliar surroundings can result in pica.

The effect of route of inoculation on the virulence of raptorial Pasteurella multocida isolates in Pekin ducks (Anas platyrhynchos)

The purpose of this study was to determine the virulence of raptorial Pasteurella multocida for ducks and the effect of various routes of inoculation on virulence. Four-week-old Pekin ducks (Anas platyrhynchos) were challenged with one of three raptorial isolates (RTHA-2, RTHA-4, or WESO-1) by one of five inoculation routes (intranasal, intraocular, intravenous, oral, and subcutaneous). Ducks were monitored daily for mortality until 2 wk postchallenge. Results indicated that the intravenous route caused the most mortality for all isolates and that significant variation existed in the virulence among the sources of P. multocida, with WESO-1 causing the least mortality of the isolates tested.

Encephalomalacia associated with vitamin E deficiency in commercially raised emus

Thirteen of 64 emus on a commercial emu farm in Ohio exhibited neurological signs that included backward staggering, incoordination, generalized weakness, and sitting on their hocks with head retracted backward. Eight of the birds showing such signs were found dead. Two of these emus were necropsied, and no significant gross lesions were observed. Major histopathological lesions were found in the cerebellum and included multiple malacic foci in association with neuropil rarefaction and astrogliosis within the white matter of folia. In addition, the hepatic vitamin E level of one emu was determined at the Michigan State University Animal Health Diagnostic Laboratory (MSU-AHDL) to be 14.61 micrograms/g dry weight. This vitamin E level was in the lower percentile (35%) of 30 emu liver samples examined at MSU-AHDL. A diagnosis of vitamin E-associated encephalomalacia was made based on clinical signs, gross and histological lesions, and liver vitamin E levels.

Serologic survey of free-living nestling prairie falcons (Falco mexicanus) for selected pathogens

Serum samples from 34 free-living nestling prairie falcons (Falco mexicanus) in southwestern Idaho were negative for antibodies to avian influenza virus, Newcastle disease virus, and three Aspergillus species. Serum from a single bird had hemagglutinating inhibition activity in response to Mycoplasma synoviae, and another bird's serum had slight activity in response to M. gallisepticum.

Evaluation of an avian-specific probiotic and Salmonella typhimurium-Specific antibodies on the colonization of Salmonella typhimurium in broilers

Salmonella typhimurium colonizes the intestinal tract of poultry and causes food-borne illness in humans. Reduction of S. typhimurium colonization in the intestinal tract of poultry reduces potential carcass contamination during slaughter. The purpose of this study was to determine the effect of an avian-specific probiotic and S. typhimurium-specific antibodies on the colonization of S. typhimurium in broilers and on body weights. Broiler chicks were spray-vaccinated at the hatchery with the commercial product. Avian Pac Plus, which contains Lactobacillus acidophilus, Streptococcus faecium, ad S. typhimurium-specific antibodies. At placement, these chicks were administered Avian Pac plus in the water. Six hours postplacement, chicks were orally challenged with 1.8 x 10 (7) CFU of S. typhimurium. Chicks were administered Avian Pac Plus for two additional days postchallenge. Chicks were evaluated for S. typhimurium colonization and shedding every 3 to 4 days for the first 2 weeks and every 7 days for 6 weeks. The mean cecal and colonic concentration of S. typhimurium from the Avian Pac Plus-treated group was significantly lower at day 31 (P = 0.0001), day 38 (P = 0.0005), and day 43 (P = 0.0001) than the nontreated control group. These results indicated that a combination of Lactobacillus acidophilus, Streptococcus faecium, and S typhimurium-specific antibodies have a beneficial effect in reducing the colonization of S. typhimurium in market-aged broilers.

Evaluation of an avian-specific probiotic to reduce the colonization and shedding of Campylobacter jejuni in broilers

Campylobacter jejuni has often been responsible for human gastroenteritis. Poultry have often been implicated as a source for these human infections. Intestinal colonization of C. jejuni in the chicken plays a role in carcass contamination during slaughter. Thus, reducing C. jejuni colonization in chickens can potentially reduce the incidence of C. jejuni infections in humans. The use of probiotics to competitively exclude the colonization of intestinal pathogens has been proposed for poultry. Hence, the purpose of this study was to evaluate the use of an avian-specific probiotic containing Lactobacillus acidophilus and Streptococcus faecium for reducing the shedding and colonization of C. jejuni in the chicken intestinal tract. Day-old chicks were randomly allocated into either a probiotic-treated group or a control group. The treated group was given probiotic from day 1 to day 3, and the control group was not given any probiotic. Six hours after the first oral administration of probiotics (treatment) or double distilled water (control), these chicks were challenged with C. jejuni. The frequency of the C. jejuni shedding was monitored until market age. Intestinal colonization was determined for the two experimental groups at slaughter. Results indicated that chickens given probiotics from day 1 to day 3 had a 70% reduction in the frequency of C. jejuni shedding in colonized chicks (P = 0.0001) and a 27% reduction in jejunal colonization in colonized chicks (P = 0.0001) at slaughter when compared with the control group. Thus, the use of the avian-specific probiotic containing L. acidophilus and S. faecium can reduce the colonization and frequency of fecal shedding of C. jejuni in market-aged broilers.