Acute human leptospirosis in a Caribbean region of Colombia: From classic to emerging risk factors

BACKGROUND

Leptospirosis is a zoonosis of worldwide incidence, with a broad spectrum of health risk factors.

AIM

The objective was to determine risk factors associated with acute human leptospirosis and to explore predictive variables of risk to human leptospirosis.

METHODS

The study was carried out in the Department of Córdoba, in the north of Colombia. We conducted a longitudinal prospective descriptive study with non-probabilistic sampling, which included 339 patients suspected of leptospirosis. Positive cases were confirmed by MAT and PCR. The determination of social and environmental risk factors was done with a survey on epidemiological and environmental variables to establish an association between cases of leptospirosis and risk factors as well as predictive variables.

RESULTS

We found 19.8% (67/339) cases of acute leptospirosis, and the seroprevalence was 27.1% (92/339). The most frequent serogroups were Sejroe, Australis, Pomona, Batavie, Pyrogenes and Grippotyphosa. We identified the following risk factors: age between 10 and 19 years (OR = 2.571; 95% CI); pig ownership (OR = 2.019; 95% CI); bathing or recreational activities in lake/lagoon (OR = 3.85; 95% CI) and in dams (OR = 3.0; 95% CI); floodings 30 days before the onset of symptoms (OR = 2.019; 95% CI), and a mean temperature of 28°C (p 0.044; 95%CI). As significant predictor variables, we identified age (10-19 years), bathing or recreational activities in the lake/lagoon, and flooding 30 days before symptoms were again evidenced. This region presents classic risk factors (pig ownership) and emerging environmental risk factors (recreational practice or bathing in a lake/lagoon and flooding 30 days before the onset of symptoms), and demographic factors such as young age (10-19 years).

CONCLUSIONS

These factors are also predictors of human cases of acute leptospirosis and provide contextual information on environmental and public health that should be considered for epidemiological surveillance in this endemic area.

Antibiotic Resistance Rates for Helicobacter pylori in Rural Arizona: A Molecular-Based Study

Helicobacter pylori (H. pylori) is a common bacterial infection linked to gastric malignancies. While H. pylori infection and gastric cancer rates are decreasing, antibiotic resistance varies greatly by community. Little is known about resistance rates among rural Indigenous populations in the United States. From 2018 to 2021, 396 endoscopy patients were recruited from a Northern Arizona clinic, where community H. pylori prevalence is near 60%. Gastric biopsy samples positive for H. pylori (n = 67) were sequenced for clarithromycin- and metronidazole-associated mutations, 23S ribosomal RNA (23S), and oxygen-insensitive NADPH nitroreductase (rdxA) regions. Medical record data were extracted for endoscopic findings and prior H. pylori history. Data analysis was restricted to individuals with no history of H. pylori infection. Of 49 individuals, representing 64 samples which amplified in the 23S region, a clarithromycin-associated mutation was present in 38.8%, with T2182C being the most common mutation at 90%. While the prevalence of metronidazole-resistance-associated mutations was higher at 93.9%, the mutations were more variable, with D95N being the most common followed by L62V. No statistically significant sex differences were observed for either antibiotic. Given the risk of treatment failure with antibiotic resistance, there is a need to consider resistance profile during treatment selection. The resistance rates in this population of American Indian patients undergoing endoscopy are similar to other high-risk populations. This is concerning given the high H. pylori prevalence and low rates of resistance testing in clinical settings. The mutations reported are associated with antibiotic resistance, but clinical resistance must be confirmed.

Development and evaluation of a multiplex serodiagnostic bead assay (BurkPx) for accurate melioidosis diagnosis

Burkholderia pseudomallei, the causative agent of melioidosis, is a gram-negative soil bacterium well recognized in Southeast Asia and northern Australia. However, wider and expanding global distribution of B. pseudomallei has been elucidated. Early diagnosis is critical for commencing the specific therapy required to optimize outcome. Serological testing using the indirect hemagglutination (IHA) antibody assay has long been used to augment diagnosis of melioidosis and to monitor progress. However, cross reactivity and prior exposure may complicate the diagnosis of current clinical disease (melioidosis). The goal of our study was to develop and initially evaluate a serology assay (BurkPx) that capitalized upon host response to multiple antigens. Antigens were selected from previous studies for expression/purification and conjugation to microspheres for multiantigen analysis. Selected serum samples from non-melioidosis controls and serial samples from culture-confirmed melioidosis patients were used to characterize the diagnostic power of individual and combined antigens at two times post admission. Multiple variable models were developed to evaluate multivariate antigen reactivity, identify important antigens, and determine sensitivity and specificity for the diagnosis of melioidosis. The final multiplex assay had a diagnostic sensitivity of 90% and specificity of 93%, which was superior to any single antigen in side-by-side comparisons. The sensitivity of the assay started at >85% for the initial serum sample after admission and increased to 94% 21 days later. Weighting antigen contribution to each model indicated that certain antigen contributed to diagnosis more than others, which suggests that the number of antigens in the assay can be decreased. In summation, the BurkPx assay can facilitate the diagnosis of melioidosis and potentially improve on currently available serology assays. Further evaluation is now required in both melioidosis-endemic and non-endemic settings.

NHP BurkPx: A multiplex serodiagnostic bead assay to monitor Burkholderia pseudomallei exposures in non-human primates

BACKGROUND

Melioidosis is a disease caused by the bacterium Burkholderia pseudomallei, infecting humans and non-human primates (NHP) through contaminated soil or water. World-wide there are an estimated 165,000 human melioidosis cases each year, but recordings of NHP cases are sporadic. Clinical detection of melioidosis in humans is primarily by culturing B. pseudomallei, and there are no standardized detection protocols for NHP. NHP are an important animal model for melioidosis research including clinical trials and development of biodefense countermeasures.

METHODOLOGY/PRINCIPLE FINDINGS

We evaluated the diagnostic potential of the multiple antigen serological assay, BurkPx, in NHP using two sera sets: (i) 115 B. pseudomallei-challenged serum samples from 80 NHP collected each week post-exposure (n = 52) and at euthanasia (n = 47), and (ii) 126 B. pseudomallei-naïve/negative serum samples. We observed early IgM antibody responses to carbohydrate antigens followed by IgG antibody recognition to multiple B. pseudomallei protein antigens during the second week of infection. B. pseudomallei negative serum samples had low to intermediate antibody cross reactivity to the antigens in this assay. Infection time was predicted as the determining factor in the variation of antibody responses, with 77.67% of variation explained by the first component of the principal component analysis. A multiple antigen model generated a binary prediction metric ([Formula: see text]), which when applied to all data resulted in 100% specificity and 63.48% sensitivity. Removal of week 1 B. pseudomallei challenged serum samples increased the sensitivity of the model to 95%.

CONCLUSION/SIGNIFICANCE

We employed a previously standardized assay for humans, the BurkPx assay, and assessed its diagnostic potential for detection of B. pseudomallei exposure in NHP. The assay is expected to be useful for surveillance in NHP colonies, in investigations of suspected accidental releases or exposures, and for identifying vaccine correlates of protection.

Highly Multiplexed Serology for Nonhuman Mammals

Emerging infectious diseases represent a serious and ongoing threat to humans. Most emerging viruses are maintained in stable relationships with other species of animals, and their emergence within the human population results from cross-species transmission. Therefore, if we want to be prepared for the next emerging virus, we need to broadly characterize the diversity and ecology of viruses currently infecting other animals (i.e., the animal virosphere). High-throughput metagenomic sequencing has accelerated the pace of virus discovery. However, molecular assays can detect only active infections and only if virus is present within the sampled fluid or tissue at the time of collection. In contrast, serological assays measure long-lived antibody responses to infections, which can be detected within the blood, regardless of the infected tissues. Therefore, serological assays can provide a complementary approach for understanding the circulation of viruses, and while serological assays have historically been limited in scope, recent advancements allow thousands to hundreds of thousands of antigens to be assessed simultaneously using <1 μL of blood (i.e., highly multiplexed serology). The application of highly multiplexed serology for the characterization of the animal virosphere is dependent on the availability of reagents that can be used to capture or label antibodies of interest. Here, we evaluate the utility of commercial immunoglobulin-binding proteins (protein A and protein G) to enable highly multiplexed serology in 25 species of nonhuman mammals, and we describe a competitive fluorescence-linked immunosorbent assay (FLISA) that can be used as an initial screen for choosing the most appropriate capture protein for a given host species. IMPORTANCE Antibodies are generated in response to infections with viruses and other pathogens, and they help protect against future exposures. Mature antibodies are long lived, are highly specific, and can bind to their protein targets with high affinity. Thus, antibodies can also provide information about an individual's history of viral exposures, which has important applications for understanding the epidemiology and etiology of disease. In recent years, there have been large advances in the available methods for broadly characterizing antibody-binding profiles, but thus far, these have been utilized primarily with human samples only. Here, we demonstrate that commercial antibody-binding reagents can facilitate modern antibody assays for a wide variety of mammalian species, and we describe an inexpensive and fast approach for choosing the best reagent for each animal species. By studying antibody-binding profiles in captive and wild animals, we can better understand the distribution and prevalence of viruses that could spill over into humans.

Canine Leptospirosis in a Northwestern Region of Colombia: Serological, Molecular and Epidemiological Factors

Canine leptospirosis is a zoonosis of epidemiological importance. Dogs are recognized as primary reservoirs of Leptospira interrogans serogroup Canicola and a source of infection to the environment through urine. This study aimed to determine the presence of antibodies against Leptospira in canines from 49 municipalities in the Department of Antioquia, Colombia. We performed a cross-sectional study of dogs included in a neutering control program. We collected 1335 sera samples, assayed by a microagglutination test (MAT), and performed PCR detection in 21 urine samples. We also surveyed 903 dog owners. We found a seroreactivity of 11.2% (150/1335) in Antioquia with titers ≥1:50. Municipalities with the highest number of cases were Belmira (46.1%), Turbo (34.5%), and Concepción (31.0%). L. santarosai was identified by phylogenetic analysis in one urine sample from the municipality of Granada. The most important factor associated with a positive result was the lack of vaccination against leptospirosis (PR 3.3, p ≤ 0.014). Environmental factors such as water presence and bare soil around the household were also associated with Leptospira seroreactivity in the Department of Antioquia. We reviewed a national epidemiological surveillance database for human cases in those municipalities. We found a correlation between the high number of cases in canines and humans, especially in the Uraba. Serological and molecular results showed the circulation of Leptospira. Future public health efforts in the municipalities with the highest numbers of seroreactivity should be directed towards vaccination to prevent animal disease and decrease the probability of transmission of Leptospira. Dogs actively participate in the Leptospira cycle in Antioquia and encourage the implementation of vaccination protocols and coverage.

"Nobody Is Talking About It": Diné (Navajo) Communities Speak About Stomach Cancer and Helicobacter pylori Infections

Stomach cancer is the third leading cause of cancer death globally. Helicobacter pylori plays a role in the healthy human gut, but is also associated with multiple chronic diseases, including stomach cancer. Though H. pylori prevalence is declining in parts of the world, it remains high among certain populations. In Arizona, stomach cancer rates are 3-4 times higher among the Navajo Nation population as compared with the non-Hispanic white population. This pilot project assessed adult Diné (Navajo) individuals' understanding and awareness regarding H. pylori infection and stomach cancer. Focus groups were held in three Diné communities. Data were analyzed thematically using a multi-investigator consensus approach. Participants had limited knowledge of H. pylori infection and stomach cancer and perceived local medical providers as also having limited knowledge on these conditions. Participants described poor health care experiences, structural inequalities, and environmental concerns and associated these with H. pylori infection and stomach cancer. This study highlights the need for additional research and education on current knowledge and perceptions of stomach cancer and H. pylori infections in Navajo Nation.

Helicobacter pylori Prevalence and Risk Factors in Three Rural Indigenous Communities of Northern Arizona

Helicobacter pylori (H. pylori) is one of the most common bacterial stomach infections and is implicated in a majority of non-cardia gastric cancer. While gastric cancer has decreased in the United States (US), the incidence in the Navajo Nation is nearly four times higher than surrounding Non-Hispanic White populations. Little is known about H. pylori prevalence in this population or other Indigenous communities in the lower 48 states. In this cross-sectional study, 101 adults representing 73 households from three Navajo Nation chapter communities completed surveys and a urea breath test for active H. pylori. Accounting for intrahousehold correlation, H. pylori prevalence was 56.4% (95% CI, 45.4–66.8) and 72% of households had at least one infected person. The odds of having an active infection in households using unregulated water were 8.85 (95% CI, 1.50–53.38) that of the use of regulated water, and males had 3.26 (95% CI, 1.05–10.07) higher odds than female. The prevalence of H. pylori in Navajo is similar to that seen in Alaska Natives. Further investigation into factors associated with prevention of infection is needed as well as understanding barriers to screening and treatment.

High Diversity of Leptospira Species Infecting Bats Captured in the Urabá Region (Antioquia-Colombia)

Leptospirosis is a globally distributed zoonotic disease caused by pathogenic bacteria of the genus Leptospira. This zoonotic disease affects humans, domestic animals and wild animals. Colombia is considered an endemic country for leptospirosis; Antioquia is the second department in Colombia, with the highest number of reported leptospirosis cases. Currently, many studies report bats as reservoirs of Leptospira spp. but the prevalence in these mammals is unknown. The goal of this study was to better understand the role of bats as reservoir hosts of Leptospira species and to evaluate the genetic diversity of circulating Leptospira species in Antioquia-Colombia. We captured 206 bats in the municipalities of Chigorodó (43 bats), Carepa (43 bats), Apartadó (39 bats), Turbo (40 bats), and Necoclí (41 bats) in the Urabá region (Antioquia-Colombia). Twenty bats tested positive for Leptospira spp. infection (20/206—9.70%) and the species of infected bats were Carollia perspicillata, Dermanura rava, Glossophaga soricina, Molossus molossus, Artibeus planirostris, and Uroderma convexum. These species have different feeding strategies such as frugivorous, insectivores, and nectarivores. The infecting Leptospira species identified were Leptospira borgpetersenii (3/20–15%), Leptospira alexanderi (2/20–10%), Leptospira noguchii (6/20–30%), Leptospira interrogans (3/20–15%), and Leptospira kirschneri (6/20–30%). Our results showed the importance of bats in the epidemiology, ecology, and evolution of Leptospira in this host-pathogen association. This is the first step in deciphering the role played by bats in the epidemiology of human leptospirosis in the endemic region of Urabá (Antioquia-Colombia).

Abstract PO-162: Helicobacter pylori in Native Americans in Northern Arizona

Background. Helicobacter pylori, one of the most common bacterial infections worldwide. Chronic infections are associated with gastritis, peptic ulcer, and gastric cancer. While H. pylori infections and gastric cancer are going down in the US, certain populations continue to experience high H. pylori prevalence of infection and a significant burden from stomach cancer. For example, in Arizona H. pylori prevalence of infection among the Navajo is 60% and gastric cancer is 3-4 times higher that of the white population. Objective: The aim of this work was to survey the presence of virulence factors (cagA and vacA) in H. pylori in the Navajo reservation and their association with gastric disease. Methods: The presence of the virulence genes, cagA and vacA in H. pylori was investigated in gastric biopsies from 97 patients attending the gastroenterology clinic in Winslow, AZ. Biopsies were collected from the antrum and fundus and used for histological examination and for molecular characterization. Molecular characterization was performed by looking at type and number of EPIYA motifs in cagA and presence of different alleles in the signal (s) and medium (m) regions of the vacA gene. Results: The infection rate in the biopsy samples was 22.9%. The cagA gene amplified in 76.9% of the cases and analysis of the 3′ region of cagA showed the predominant presence of the “Western CagA” type with the EPIYA-ABC motif (70.0%) the most prevalent. The vacA allele s1bm1 was the most prevalent (76.9%) followed by s2m2 (11.5%). CagA negative isolates were associated with gastritis or normal findings while EPIYA motifs ABCC were present in severe gastric disease. vacA s2m2 were associated with normal findings. Conclusions: In this population, we have found H. pylori genotypes with predominant cagA Western-type and ABC EPIYA motifs. The vacA s1m1 genotype was the most prevalent and seemed to be associated with gastritis. American Indian/Native American populations are at higher risk for gastric cancer than the general US population. It is important to better establish and quantify genotypes of H. pylori to identify bacterial factors involved in the high prevalence of H. pylori and associated disease among the Navajo population.

Citation Format: Fernando P. Monroy, Heidi E. Brown, Priscilla Sanderson, Gregory Jarrin, Mimi Mbegbu, Shari Kyman, Camenlita Chief, Robin B. Harris. Helicobacter pylori in Native Americans in Northern Arizona [abstract]. In: Proceedings of the AACR Virtual Conference: Thirteenth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2020 Oct 2-4. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(12 Suppl):Abstract nr PO-162.

Domestic canines do not display evidence of gut microbial dysbiosis in the presence of Clostridioides (Clostridium) difficile, despite cellular susceptibility to its toxins

Clostridioides difficile infection (CDI) is an emerging public health threat and C. difficile is the most common cause of antimicrobial-associated diarrhea worldwide and the leading cause of hospital-associated infections in the US, yet the burden of community-acquired infections (CAI) is poorly understood. Characterizing C. difficile isolated from canines is important for understanding the role that canines may play in CAI. In addition, several studies have suggested that canines carry toxigenic C. difficile asymptomatically, which may imply that there are mechanisms responsible for resistance to CDI in canines that could be exploited to help combat human CDI. To assess the virulence potential of canine-derived C. difficile, we tested whether toxins TcdA and TcdB (hereafter toxins) derived from a canine isolate were capable of causing tight junction disruptions to colonic epithelial cells. Additionally, we addressed whether major differences exist between human and canine cells regarding C. difficile pathogenicity by exposing them to identical toxins. We then examined the canine gut microbiome associated with C. difficile carriage using 16S rRNA gene sequencing and searched for deviations from homeostasis as an indicator of CDI. Finally, we queried 16S rRNA gene sequences for bacterial taxa that may be associated with resistance to CDI in canines. Clostridioides difficile isolated from a canine produced toxins that reduced tight junction integrity in both human and canine cells in vitro. However, canine guts were not dysbiotic in the presence of C. difficile. These findings support asymptomatic carriage in canines and, furthermore, suggest that there are features of the gut microbiome and/or a canine-specific immune response that may protect canines against CDI. We identified two biologically relevant bacteria that may aid in CDI resistance in canines: 1) Clostridium hiranonis, which synthesizes secondary bile acids that have been shown to provide resistance to CDI in mice; and 2) Sphingobacterium faecium, which produces sphingophospholipids that may be associated with regulating homeostasis in the canine gut. Our findings suggest that canines may be cryptic reservoirs for C. difficile and, furthermore, that mechanisms of CDI resistance in the canine gut could provide insights into targeted therapeutics for human CDI.

Intracellular Invasion and Killing Assay to Investigate the Effectsof Binge Alcohol Toxicity in Murine Alveolar Macrophages

Alcohol consumption has diverse and well-documented effects on the human immune system and its ability to defend against infective agents. While pulmonary related infections can occur in healthy humans, binge alcohol use is recognized as a major health risk factor (Nelson et al., 1991). Although binge alcohol consumption has been considered as a risk factor for the development of pulmonary infections, no experimental studies have investigated the outcomes of a single binge alcohol exposure during infection. A key assay to assess the effects of a single binge alcohol exposure on the interactions between bacteria and alveolar macrophage is a binge alcohol intracellular invasion and killing assay. MH-S alveolar macrophages (AMs) are exposed to a single binge alcohol dose prior to infection for 3 h. The macrophage monolayer is then infected to allow for engulfment, followed by removal of extracellular bacteria to assess the intracellular killing capacity of infected macrophages over time. We have utilized this assay to demonstrate that low alcohol exposure significantly suppressed the uptake and killing of less virulent Burkholderia thailandensis (B. thailandensis) by AMs. More recently we found that activated AMs with interferon (IFN)-γ incubated in alcohol (0.08%) for 3 h prior to infection showed significantly lower bacterial uptake at 2 and 8 h post infection, which lead to B. thailandensis survival and a ~2.5-fold replication increase compared to controls (Jimenez et al., 2017). These results provide insights into binge alcohol consumption, a culturally prevalent risk factor, as a predisposing factor for pulmonary bacterial infections. This assay can be adapted to other bacterial species and host cell types to assess tissue specific effects of alcohol during infection.

Effects of binge alcohol exposure on Burkholderia thailandensis-alveolar macrophage interaction

Alcohol consumption has diverse and well-documented effects on the human immune system and its ability to defend against infective agents. One example is melioidosis, a disease caused by infection with Burkholderia pseudomallei, which is of public health importance in Southeast Asia and Northern Australia, with an expanding global distribution. While B. pseudomallei infections can occur in healthy humans, binge alcohol use is progressively being recognized as a major risk factor. Although binge alcohol consumption has been considered as a risk factor for the development of melioidosis, no experimental studies have investigated the outcomes of alcohol exposure on Burkholderia spp. infection. Therefore, we proposed the use of non-pathogenic B. thailandensis E264 as a useful BSL-1 model system to study the effects of binge alcohol exposure on bacteria and alveolar macrophage interactions. The MH-S alveolar macrophage (AMs) cell line was used to characterize innate immune responses to infection in vitro. Our results showed that alcohol exposure significantly suppressed the uptake and killing of B. thailandensis by AMs. Alveolar macrophages incubated in alcohol (0.08%) for 3 h prior to infection showed significantly lower bacterial uptake at 2 and 8 h post infection. Activated AMs with IFN-γ and pre and post-incubation in alcohol when exposed to B. thailandensis released lower nitric oxide (NO) concentrations, compared to activated AMs with IFN-γ from non-alcoholic controls. As a result, B. thailandensis survival and replication increased ∼2.5-fold compared to controls. The presence of alcohol (1%) also increased bacterial survival within AMs. Alcohol significantly decreased bacterial motility compared to non-alcoholic controls. Increased biofilm formation was observed at 3 and 6 h when bacteria were pre-incubated in (0.08%) alcohol. These results provide insights into binge alcohol consumption, a culturally prevalent risk factor, as a predisposing factor for melioidosis.

Role of glucocorticoids and Toxoplasma gondii infection on murine intestinal epithelial cells

Glucocorticoids (GCs) are stress hormones secreted in response to perceived psychological and or physiological stress. GCs have been shown to reduce tissue inflammation by down-regulating the production of inflammatory chemokines produced by epithelial cells. The protozoan parasite Toxoplasma gondii is known to increase cytokine, chemokine, and Toll-like receptors (TLRs) expression in parasite infected mouse intestinal epithelial cells (IECs). We sought to analyze the role of an anti-inflammatory protein, glucocorticoid-induced leucine zipper (GILZ) in MODE-K cells during infection with T. gondii. GILZ expression in MODE-K cells was assessed by PCR and immunoblotting after stimulation with GCs (corticosterone, CORT) or T. gondii infection. GILZ mRNA was constitutively expressed in MODE-K cells but not its protein product. While infection and pre-exposure to CORT decreased GILZ isoforms of 28 and 17 kD, the presence of CORT during infection increased levels of 17 kD isoform. Infected cells treated with CORT had decreased expression of chemokines (IP-10/CXCL10, MCP-1/CCL2, MIP-2/CXCL8) while their expression was increased when endogenous GILZ was removed by siRNA treatment. GILZ up-regulation during infection may serve as a mechanism to decrease epithelial cell responses and facilitate parasite replication.

Regulation of chemokine responses in intestinal epithelial cells by stress and Toxoplasma gondii infection

Infection with Toxoplasma gondii induces chemokine up-regulation in several cell types. Here, we investigated the role of stress products (norepinephrine, NE) on chemokine production in mouse intestinal epithelial cells (IECs). Purified IECs were used to determine the expression levels of chemokines by real-time PCR. There was significantly increased expression in CCL2, CCL3, CCL5, CXCL2, CXCL9 and CXCL10 in IECs following peroral infection with T. gondii (INF) on day eight post-infection (PI) compared to infected mice subjected to cold-water stress (INF+CWS). In vitro studies using the MODE-K cell line showed increased chemokine mRNA and protein expression in infected but not in cells exposed to parasite antigen. Down-regulation of chemokine expression was more pronounced when active infection was used in combination with NE. Chemokine receptor expression was increased in IECs isolated from INF and decreased in the INF+CWS group. In MODE-K cells, there was decreased mRNA expression of chemokine receptors when incubated with β-adrenergic antagonists. Neither, adrenergic antagonists blocked the effect of infection on chemokine receptor expression. Cold-water stress was able to decrease expression of chemokines and their receptors in IECs in vivo and in vitro. Cold-water stress-mediated modulation of innate intestinal responses are beneficial in C57BL/6 mice during T. gondii infection.

Regulation of toll-like receptors in intestinal epithelial cells by stress and Toxoplasma gondii infection

Intestinal epithelial cells (IECs) form a barrier between invading microorganisms and the underlying host tissues. IECs express toll-like receptors (TLRs) that recognize specific molecular signatures on microbes, which activate intracellular signalling pathways leading to production of proinflammatory cytokines and chemokines. Stress hormones play an important role in modulation of proinflammatory cytokines and down-regulation of immune responses. Here we demonstrated that expression levels of TLR-2, TLR-4, TLR-9 and TLR-11 were significantly increased in mouse IECs following infection with Toxoplasma gondii on day 8 postinfection. In contrast, expression of TLRs was significantly decreased in infected mice subjected to cold water stress (CWS + INF). Expression of TLR-9 and TLR-11 in the mouse MODE-K cell line was significantly increased after infection. Expression of TLR-9 and TLR-11 in cells exposed to norepinephrine (NE) and parasites was significantly decreased when compared to cells exposed to parasites only. A significant increase was observed in SIGIRR, a negative regulator of TLRs in the CWS + INF group when compared to the INF group. Stress components were able to decrease expression levels of TLRs in IECs, decrease parasite load, and increase expression of a negative regulator thereby ameliorating intestinal inflammatory responses commonly observed during per oral T. gondii infection in C57BL/6 mice.

Antibodies in cold stressed mice recognize a surface protein in Toxoplasma gondii tachyzoites

Physical or psychological stressors are known to have significant consequences for immune function and the outcome of disease in human and animal models. In mice, cold water stress (CWS) has been shown to delay control of acute infection and reactivation of latent infections. Increased levels of parasite-specific IgG and IgM antibodies are observed when CWS is applied in the chronic phase. The present study examined the effects of a physical stressor, CWS, on tachyzoites antigens of Toxoplasma gondii, with particular emphasis on a low molecular weight antigen, 5 kDa, which seems to be recognized by antibodies from mice subjected to CWS in the chronic phase. This antigen is not recognized by antibodies from infected mice not subjected to CWS. Sera obtained from stressed and infected (CWS + INF) mice subjected to CWS during the chronic phase (CWS + INF + CWS) were used to harvest anti-5-kDa antibodies for immunolocalization studies. Tachyzoite lysate preparations were electrophoretically separated and transferred to nitrocellulose membranes. Strips of nitrocellulose containing tachyzoite antigens in the 4-10-kDa range were used to select for anti-5-kDa antibodies. Harvested anti-5-kDa localized this antigen on the surface of tachyzoites. This antigen was not present in bradyzoite preparations. Treatment with phosphatidylinositol-specific phospholipase C showed this antigen was not anchored to the cell membrane through glycosyl-phosphatidylinositol. Strong antibody responses in stressed animals during the chronic phase are associated with parasite reactivation. The 5-kDa antigen constitutes a unique immunogenic component of T. gondii, with significant diagnostic potential for identifying reactivation of latent infections.

Toxoplasma gondii: effect of infection on expression of 14-3-3 proteins in human epithelial cells

14-3-3 Proteins are expressed in most eukaryotes organisms and play varied and crucial roles in a wide range of regulatory processes. In mammalian cells, seven 14-3-3 isoforms have been identified. However, it is not known what effect infection has on 14-3-3 isoform expression. In this study human colonic carcinoma cell lines were infected with Toxoplasma gondii for 24h and expression of 14-3-3 proteins was determined by RT-PCR. HT-29 cells only expressed 3 out of the 7 isoforms while 5 and all 7 isoforms were found in HCT-116 and Caco-2 cells, respectively. Infection had little or no effect in the expression of 14-3-3gamma, epsilon, sigma, and xi; but in HCT-116 cells induced expression of 14-3-3eta and sigma, while 14-3-3beta, eta, and xi were induced in HT-29 cells. If 14-3-3 proteins are involved in cell survival and/or prevention of parasite replication, longer incubation times may be required as no differences in percentage of infection were found among the cell lines at 24h post-infection.

Effects of alpha- and beta-adrenergic agonists on Toxoplasma gondii infection in murine macrophages

We investigated the effects of alpha- and beta-adrenergic receptor agonists on the ability of Toxoplasma gondii to infect and proliferate in cultured murine macrophages. Macrophages pretreated in vitro with varying concentrations of alpha- and beta-adrenergic agonists and incubated with the RH strain of T. gondii did not result in a significant increase in the percentage of infected macrophages compared with negative controls. When parasites were pretreated with L-phenylephrine, an alpha-agonist, and L-isoproterenol, a beta-agonist, before infection, there was no significant change in the percentage of infected macrophages. Clonidine, an alpha2-adrenergic agonist, led to a significant decrease in the number of infected macrophages at all concentrations tested. The effects of clonidine were blocked by yohimbine, a specific alpha2-adrenergic antagonist, but not by phentolamine, an alpha1-adrenergic antagonist. These results suggest that the antiparasitic effects exhibited by clonidine (alpha2-adrenergic agonist) are mediated through an alpha2-adrenoreceptor found on the surface of T. gondii.

Effects of cold stress on spleen cell proliferation and cytokine production during chronic Toxoplasma gondii infection

BACKGROUND

Cell-mediated immunity is critical for controlling infection and preventing reactivation during the chronic phase of Toxoplasma gondii infection. In people suffering from AIDS, T. gondii is one of the major opportunistic infectious agents. Mechanisms regulating rapid development of clinical signs in previously asymptomatic patients remain unclear; however, cofactors such as stress are suspected to play a role in the susceptibility to opportunistic infections.

OBJECTIVE

This study examined the role of cold stress (CS) in splenocyte function during chronic T. gondii infection.

METHODS

Control mice and mice previously infected orally with T. gondii were subjected to CS during the chronic phase (CSchr), i.e. 90 days after infection, and in vitro cell proliferation and cytokine production were measured before (day 0) and 1, 15 and 25 days after CSchr. Splenocyte proliferation and cytokine production were measured after in vitro stimulation with concanavalin A (Con-A), anti-CD3 antibody (A-CD3) and Toxoplasma lysate antigen.

RESULTS

CSchr enhanced splenocyte proliferation in cells stimulated with Con-A and A-CD3, but it suppressed proliferation in cells stimulated with T. gondii antigens. Increased levels of interferon (IFN)-gamma were detected independent of the type of stimulation after CSchr and remained high throughout the experiment. CS had similar results in noninfected animals.

CONCLUSION

Although an overall increase in splenocyte function occurred after nonspecific stimulation, CS suppressed primed spleen cells from responding to T. gondii antigens which could lead to reactivation of latent infection. The increase in IFN-gamma after CSchr could be a result of spleen cells being primed by released parasites by this stressor. IFN-gamma is critical in the control of parasite reactivation.

Toxoplasma gondii: cold stress-induced modulation of antibody responses

Physical or psychological stressors have been shown to have significant consequences in the immune function and the outcome of disease in human and animal models. Recent work has demonstrated that products released during stress, such as glucocorticoids and catecholamines, can profoundly influence the in vitro growth of pathogens by modulating immune responses. The present study examined the effects of a physical stressor (cold stress) on antigens of Toxoplasma gondii that elicits an antibody-mediated immune response during the acute and chronic phases of infection. Sera obtained from different groups of mice subjected to cold stress during the acute and chronic phases of T. gondii infection were used to measure the levels of antibodies and to localize by Western blot the dominant antigens eliciting IgG and IgM antibody responses. Serum antibodies collected from stressed and infected mice recognized antigens different from those recognized by infected mice without stress. During the acute phase, a stronger IgM antibody response against antigens of 30, 42, 54, and 60 kDa was detected in stressed animals at 3 weeks postinfection. In addition, a 5-kDa antigen was specifically detected in mice subjected to stress during the acute and chronic phases of infection. Levels of specific IgG were increased in infected and in infected and stressed animals that underwent stress in the chronic phase. IgM production did not increase following cold stress in the chronic phase. These results suggest that the strong antibody response in stressed animals is associated with longer parasite persistence in circulation. Stress modulated not only the host immune response but also the ability of parasite antigens to elicit specific antibody responses by the host.

Immunomodulatory effects of cold stress on mice infected intraperitoneally with a 50% lethal dose of Toxoplasma gondii

Cofactors such as stress have been suspected to play a role in the susceptibility to opportunistic infections. Toxoplasma gondii is one of the major opportunistic infectious agents in immunocompromised individuals, and infection can be modulated by external factors such as stress.

OBJECTIVE

The purpose of this study was to examine the in vivo and in vitro role of cold stress (CS) in the pathogenesis of T. gondii infection and its impact on regulatory cytokines in this model.

METHODS

Mice subjected to CS and control animals were infected intraperitoneally with an LD(50) of PD2 T. gondii tachyzoites, and the outcome of the infection was determined. In addition, peritoneal macrophages obtained from CS and non-stressed mice were infected in vitro with T. gondii. The number of infected macrophages, the number of intracellular parasites and the production of interferon (IFN)-gamma, interleukin (IL)-12, and tumor necrosis factor (TNF)-alpha were determined.

RESULTS

CS applied before intraperitoneal inoculation increased susceptibility against T. gondii infection. Peritoneal cells from CS mice contained significantly higher numbers of intracellular parasites and infected macrophages compared to those from non-stressed animals. IFN-gamma production was initially high in the CS group but decreased significantly after 36 h. Opposite results were found in the non-stressed group. Macrophages from CS mice persistently produced high levels of TNF-alpha and IL-12 and peaked after 36 h. Levels of these cytokines were lower or absent in the non-stressed group.

CONCLUSION

These results suggest that CS increased the host susceptibility to intraperitoneal T. gondii infection by modulating the function of macrophages and the production of cytokines (IFN-gamma) involved in the early control of infection.

The kidney form of Trypanosoma musculi: A distinct stage in the life cycle?

Trypanosoma musculi is a parasite specific to mice, which resides in the blood and lacks intracellular stages. After immune clearance of the flagellates from the general circulation, mice are resistant to reinfection. Yet, long after parasites are no longer detected in the peripheral blood, they persist in the vasa recta of the kidneys and it has been proposed that this is an immunologically privileged site for T. musculi. This relationship provides a useful model for studies of latent or chronic infections in immune hosts. Here, Fernando Monroy and Donald Dusanic consider the immune responses of mice to T. musculi and compare characteristics of the parasites from the vasa recta (kidney forms, KFs) of mice with latent infections to trypanosomes from the peripheral blood (bloodstream forms, BSFs) of animals during active infections. They consider how KFs evade immune destruction and suggest that these sequestered parasites represent a distinct stage in the life cycle.

Cold stress-induced modulation of inflammatory responses and intracerebral cytokine mRNA expression in acute murine toxoplasmosis

The effects of a physical stressor, cold water stress (CWS), within the central nervous system were investigated in the acute phase of infection with Toxoplasma gondii. Female BALB/c mice were subjected to CWS for 5 min each day for 8 days prior to oral infection with 20 cysts of the low virulent ME 49 strain. Animals were killed at 10-day intervals to detect inflammation, gliosis, and expression of intracerebral cytokine mRNAs. Zones of inflammation were detected by Nissl staining and gliosis by immunoreactivity to glial fibrillary acidic protein. Larger zones of inflammation and reactive astrogliosis were consistently observed in mice subjected to CWS and infected (CWS +INF) compared to control infected (INF) mice. Expression of interleukin (IL)-1beta, IL-2, IL-12, interferon (IFN)-gamma, tumor necrosis factor (TNF)-alpha, and inducible nitric oxide synthase (iNOS) were decreased in CWS+INF mice at 10 days postinoculation (PI), followed by a gradual increase after day 20 PI. This was in contrast to increased expression of these cytokines at 10 days PI in INF mice with a gradual decline thereafter. Inflammation and astrogliosis in CWS+INF mice were associated with an increased expression of IL-1beta, IL-6, IL-12, and TNF-alpha between 20 and 30 days PI. These findings correlated with the continuous gene expression of tachyzoite surface antigen (SAG)-1 mRNA in CWS+INF mice compared to its sharp decline in INF mice after 20 days PI. These results suggest that CWS delays regulation and control of intracerebral Toxoplasma gondii during acute infection in BALB/c mice by decreasing the early expression of IFN-gamma, IL-2, TNF-alpha, iNOS, IL-1beta, and IL-12, while increasing the expression of IL-6, a counterregulatory cytokine.

Cold stress-induced modulation of cell immunity during acute Toxoplasma gondii infection in mice

Infection with Toxoplasma gondii in the acute phase results in nonspecific suppression of immunologic function in mice and humans. The present study examined the effects of a physical stressor, i.e., cold stress (CS), on macrophage function (nitrite production, parasite survival) and splenic blastogenesis in the acute phase of murine T. gondii infection. In our stress paradigm, female BALB/c mice were placed in cold water (1 +/- 0.5 C), 5 min each day for 8 days. Nitrite production and parasite survival were measured in cultured peritoneal macrophages obtained from mice subjected to CS after in vivo activation with interferon-gamma/lipopolysaccharide (CS + ACT), and in vitro infection with T. gondii tachyzoites. Peritoneal macrophages from CS + ACT mice showed decreased nitrite production compared to control but activated cells (ACT). Spleen cell proliferation to in vitro stimulation with the mitogens concanavalin A (Con A) and anti-CD3, and Toxoplasma lysate antigen (TLA) was measured in splenocytes obtained from BALB/c mice during the acute phase of infection with T. gondii. Mice subjected to CS and infection (CS + INF) had maximum splenocyte proliferation on days 8 and 15 followed by a subsequent decline on day 28 postinoculation (PI). In contrast, infected mice not subjected to stress (INF) showed decreased splenocyte proliferation on days 8 and 15 followed by an increase on day 28 PI. The rate of mortality was decreased in the CS + INF compared to the INF group during acute infection. These results suggest that CS may alter the pathogenesis of T. gondii infection by modulating acute-phase responses, provoking a state of transient disequilibrium between the host and parasite.

PCR detection and identification of Leishmania parasites in clinical specimens in Ecuador: a comparison with classical diagnostic methods

A simplified polymerase chain reaction (PCR)-based assay was used for detection and typing of Leishmania parasites in clinical specimens from patients suspected of cutaneous leishmaniasis. Using cultures as the reference standard, our PCR detection method was more sensitive (92%) than classical diagnostic techniques, including microscopy (42% sensitivity), histologic staining (33%), and IgG enzyme-linked immunosorbent (20%). The PCR assay was also 100% specific. Parasites in both lesion biopsies and isolates cultured from lesion aspirates were identified as Leishmania braziliensis by PCR. In this study, we have demonstrated the suitability of simplified PCR assays for the simultaneous diagnosis and typing of parasites causing cutaneous leishmaniasis in a developing country where leishmaniasis is endemic.

Trypanosoma musculi survival in the kidneys of chronically infected mice: kidney form ultrastructure, surface characteristics, and serological interactions

After elimination of Trypanosoma musculi from the general circulation by the immune responses of infected mice, the animals are resistant to reinfection. Yet, parasites survive in the vasa recta of the kidneys for the life of these mice. These kidney forms (KF) actively reproduce in an environment that provides the necessary nutrients and appears to prevent their elimination from these capillaries by the hosts' immune responses. Comparative studies conducted with KF and the bloodstream forms (BSF) indicate that, although both forms appear to be similar morphologically at the ultrastructural level, they differ in their surface reactivities with lectins and tolerance to various pH and solute concentrations. Although antibodies are not detected on the surfaces of KF, urea levels approximating those in the vasa recta dissociate antibody from the surfaces of BSF. The data suggest that parasites found in the vasa recta of these chronically infected mice differ from the BSF and are protected from the humoral and cell-mediated immune responses of the murine hosts by the concentrated solutes present in these capillaries. The KF may be killed by these same immune effector mechanisms upon leaving the capillaries of the kidneys and, therefore, not be found in the general circulation of these chronically infected immune hosts.

Survival of Trypanosoma musculi in the kidneys of chronically infected mice: kidney form reproduction and immunological reactions

Trypanosoma musculi are detected in the blood of the mouse host within 3-5 days after infection. Peak parasitemia is reached within 10 days and parasites persist at a plateau level for 2-3 wk. There are no intracellular stages and the flagellates are eliminated from the peripheral blood within 4 wk. However, trypanosomes persist in the vasa recta of the kidneys and may be present for the life of the host. Infection provides lifelong resistance to reinfection. Kidney forms (KF) of T. musculi were isolated and studied to define their morphology, reproductive activity, and serological reactivity. Dividing epimastigotes and trypomastigote stages were present in kidneys. Multinucleate and rosette forms were common. Measurements of the coefficient of variation of the KF confirmed that the trypanosomes were actively reproducing. Direct immunofluorescence reactions with rabbit antimouse IgG + IgA + IgM detected antibodies on bloodstream forms (BSF) but not on the KF. However, indirect immunofluorescence tests using antisera collected from mice during early and late phases of the infections showed that KF were capable of reacting with antibodies. The reproductive activity displayed by the KF appears to be responsible for the continuous replacement of the trypanosomes that are killed by the immune responses of the resistant mice when they leave the vasa recta. Solute concentrations of the blood within the vasa recta appear to prevent antibodies from complexing with surface antigens of the parasites. These capillaries provide nutrients that allow the trypanosomes to reproduce and persist unaffected by the host immune responses.

The developmental expression of cysteine proteinases in Schistosoma mansoni

In this study several probes were used to identify and characterize cysteine proteinases (CP) from Schistosoma mansoni developmental stages. Proteinase activity was detected in all developmental stages using fluorogenic substrates. Specific activity was 4- to 11-fold higher against CBZ-phe-arg-AFC than against CBZ-arg-arg-AFC. A 32 kDa S. mansoni CP (Sm32) was identified in all stages by the radiolabelled active site CP inhibitor, CBZ-[125I]tyr-ala-CHN2. A second CP, of 31 kDa (Sm31) was only detected in adult worms, primarily female worms and late schistosomula. Monoclonal antibodies for Sm32 and Sm31 reacted with homologous CP only in adult worms and late schistosomula. This study defines the developmental expression of CP activity in S. mansoni.

Biomphalaria glabrata hemolymph lectins: binding to bacteria, mammalian erythrocytes, and to sporocysts and rediae of Echinostoma paraensei

Polyclonal antibodies were raised in rabbits to two groups of diffusely staining M line Biomphalaria glabrata plasma polypeptides, of 150-210 and 70-120 kDa, designated as Group 1 molecules (G1M) and group 2 molecules (G2M), respectively. G1M and G2M are known to increase in abundance and to become more diverse following infection of B. glabrata with the digenetic trematode Echinostoma paraensei. These antibodies were used in conjunction with immunoblotting and slot blotting procedures to document binding of G1M/G2M from plasma of unexposed control snails (C plasma) or plasma from snails with 8-day infections of E. paraensei (I plasma) to various targets. Binding of G1M/G2M to both gram-positive and gram-negative bacteria, human A, B, and O and rabbit erythrocytes, and to sporocysts and rediae of E. paraensei was documented. Immunoblots revealed that erythrocytes are bound by a particular G2M band of 100-120 kDa present in I plasma that is in low concentration or lacking in C plasma. This explains previous results indicating that I plasma agglutinates all 4 erythrocytes examined whereas C plasma agglutinates only rabbit erythrocytes. More G1M/G2M binding to sporocysts occurred if I plasma rather than C plasma was used for incubations. Also, monosaccharide inhibition of G1M/G2M binding to sporocysts was observed in I plasma but not in C plasma. The results indicate that infection with E. paraensei induces production by B. glabrata of unique plasma polypeptides and that molecules present in I plasma can bind to the surfaces of non-self objects including E. paraensei larvae in a lectin-like fashion.

Production of heterogeneous carbohydrate-binding proteins by the host snail Biomphalaria glabrata following exposure to Echinostoma paraensei and Schistosoma mansoni

Hemolymph lectins may play an important role in the internal defense responses of gastropods to parasites. Two groups of known carbohydrate-binding polypeptides, of 150-220 kDa (designated as group 1 molecules, or G1M) and of 75-130 kDa (group 2 molecules, or G2M), were harvested from pooled plasma samples of Biomphalaria glabrata using affinity chromatography and examined using 2-dimensional electrophoresis. Plasma samples were derived from control snails or snails exposed 8 days earlier to the trematodes Echinostoma paraensei or Schistosoma mansoni. Plasma of control and S. mansoni-exposed snails contained little or no G1M, whereas plasma from E. paraensei-infected snails contained G1M covering a broad pI spectrum. G2M resolved as 1-2 isoforms in control plasma and up to 4 relatively faint isoforms in plasma from S. mansoni-exposed snails, and as 5-6 resolvable isoforms in plasma from E. paraensei-infected snails. Plasma from individual snails contained as many as 5 G2M polypeptides following exposure to E. paraensei. Exposure to trematode larvae stimulated production by B. glabrata of increased abundance and diversity of carbohydrate-binding proteins. The 2 trematode species provoked different responses, and 2 B. glabrata strains studied (M line and 13-16-R1 strains) differed from one another in their responses.