Lower numbers of natural killer T cells in HIV-1 and Mycobacterium leprae co-infected patients

Natural killer T (NKT) cells are a heterogeneous population of lymphocytes that recognize antigens presented by CD1d and have attracted attention because of their potential role linking innate and adaptive immune responses. Peripheral NKT cells display a memory-activated phenotype and can rapidly secrete large amounts of pro-inflammatory cytokines upon antigenic activation. In this study, we evaluated NKT cells in the context of patients co-infected with HIV-1 and Mycobacterium leprae. The volunteers were enrolled into four groups: 22 healthy controls, 23 HIV-1-infected patients, 20 patients with leprosy and 17 patients with leprosy and HIV-1-infection. Flow cytometry and ELISPOT assays were performed on peripheral blood mononuclear cells. We demonstrated that patients co-infected with HIV-1 and M.leprae have significantly lower NKT cell frequencies [median 0.022%, interquartile range (IQR): 0.0070.051] in the peripheral blood when compared with healthy subjects (median 0.077%, IQR: 0.0320.405, P < 0.01) or HIV-1 mono-infected patients (median 0.072%, IQR: 0.0300.160, P < 0.05). Also, more NKT cells from co-infected patients secreted interferon-? after stimulation with DimerX, when compared with leprosy mono-infected patients (P = 0.05). These results suggest that NKT cells are decreased in frequency in HIV-1 and M.leprae co-infected patients compared with HIV-1 mono-infected patients alone, but are at a more activated state. Innate immunity in human subjects is strongly influenced by their spectrum of chronic infections, and in HIV-1-infected subjects, a concurrent mycobacterial infection probably hyper-activates and lowers circulating NKT cell numbers.

A SURVEY OF NEOSPORA CANINUM AND TOXOPLASMA GONDII INFECTION IN URBAN RODENTS FROM BRAZIL

Toxoplasma gondii is a protozoan parasite that infects humans and other warm-blooded animals; it uses feral and domestic cats as the definitive hosts. Neospora caninum is a protozoan parasite of animals whose life cycle is very similar to T. gondii but uses canids as definitive hosts. Small rodents play an important role in the life cycle of T. gondii, and a few findings indicated that they may be natural intermediate hosts for N. caninum. The present study was aimed at identifying infections by T. gondii and N. caninum in urban rodents. Infections by T. gondii were quantified using isolation of the parasite by bioassay in mice; molecular methods were also used for both parasites. Overall, 217 rodents were captured. Brain and heart tissues of all rodents were bioassayed in mice for the detection of T. gondii infection. Brain and heart tissues of 121 rodents had the DNA extracted for molecular analysis. Toxoplasma gondii was isolated by bioassay from a single rodent. From the 121 rodents tested for the presence of T. gondii DNA, 2 animals were positive. In contrast, DNA of N. caninum was not detected in any of the samples. In conclusion, the surveys of N. caninum and T. gondii infection in Rattus rattus, Rattus norvegicus, and Mus musculus captured in urban areas of Sao Paulo reveal a striking low frequency of occurrence of these infections.

Paracoccidioides brasiliensis infection in dogs from Western Brazilian Amazon

The objective of the study was to evaluate Paracoccidioides brasiliensis infection in urban dogs from the municipality of Monte Negro, Rondonia, Western Brazilian Amazon. The serum samples (n=126) were analyzed by indirect ELISA and the immunodiffusion test using P. brasiliensis gp43 and exoantigen as antigens, respectively. A positivity of 54.8% was observed only in the ELISA test and no statistical difference was observed in the seroprevalence in relation to age or sex. This is the first paracoccidioidomycosis survey carried out with dogs from the Western Brazilian Amazon. The higher positivity rates of P. brasiliensis infection observed in this study suggest that veterinarians must be alert to detect new cases of natural disease in dogs living in paracoccidioidomycosis endemic areas.

Natural antibody response to Plasmodium falciparum merozoite antigens MSP5, MSP9 and EBA175 is associated to clinical protection in the Brazilian Amazon

BACKGROUND: Antibodies have an essential role in the acquired immune response against blood stage P. falciparum infection. Although several antigens have been identified as important antibody targets, it is still elusive which antigens have to be recognized for clinical protection. Herein, we analyzed antibodies from plasmas from symptomatic or asymptomatic individuals living in the same geographic area in the Western Amazon, measuring their recognition of multiple merozoite antigens. METHODS: Specific fragments of genes encoding merozoite proteins AMA1 and members of MSP and EBL families from circulating P. falciparum field isolates present in asymptomatic and symptomatic patients were amplified by PCR. After cloning and expression of different versions of the antigens as recombinant GST-fusion peptides, we tested the reactivity of patients' plasmas by ELISA and the presence of IgG subclasses in the most reactive plasmas. RESULTS: 11 out of 24 recombinant antigens were recognized by plasmas from either symptomatic or asymptomatic infections. Antibodies to MSP9 (X2(DF=1) = 9.26/p = 0.0047) and MSP5 (X2(DF=1) = 8.29/p = 0.0069) were more prevalent in asymptomatic individuals whereas the opposite was observed for MSP1 block 2-MAD20 (X2(DF=1) = 6.41/p = 0.0206, Fisher's exact test). Plasmas from asymptomatic individuals reacted more intensely against MSP4 (U = 210.5, p < 0.03), MSP5 (U = 212, p < 0.004), MSP9 (U = 189.5, p < 0.002) and EBA175 (U = 197, p < 0.014, Mann-Whitney's U test). IgG1 and IgG3 were predominant for all antigens, but some patients also presented with IgG2 and IgG4. The recognition of MSP5 (OR = 0.112, IC95% = 0.021-0.585) and MSP9 (OR = 0.125, IC95% = 0.030-0.529, cross tab analysis) predicted 8.9 and 8 times less chances, respectively, to present symptoms. Higher antibody levels against MSP5 and EBA175 were associated by odds ratios of 9.4 (IC95% = 1.29-69.25) and 5.7 (IC95% = 1.12-29.62, logistic regression), respectively, with an asymptomatic status. CONCLUSIONS: Merozoite antigens were targets of cytophilic antibodies and antibodies against MSP5, MSP9 and EBA175 were independently associated with decreased symptoms.

The role of the NadR regulator during infection and its implication for the coverage of a new Meningococcus B vaccine

Background: Neisseria meningitides represents a major cause of meningitis and sepsis. The meningococcal regulator NadR was previously shown to repress the expression of the Neisserial Adhesin A (NadA) and play a major role in its phase-variation. NadA is a surface exposed protein involved in epithelial cell adhesion and colonization and a major component of 4CMenB, a novel vaccine to prevent meningococcus serogroup B infection. The NadR mediated repression of NadA is attenuated by 4-HPA, a natural molecule released in human saliva. Results: In this thesis we investigated the global role of NadR during meningogoccal infection, identifying through microarray analysis the NadR regulon. Two distinct types of NadR targets were identified, differing in their promoter architectures and 4HPA responsive activities: type I are induced, while type II are co-repressed in response to the same 4HPA signal. We then investigate the mechanism of regulation of NadR by 4-HPA, generating NadR mutants and identifying classes or residues involved in either NadR DNA binding or 4HPA responsive activities. Finally, we studied the impact of NadR mediated repression of NadA on the vaccine coverage of 4CMenB. A selected MenB strains is not killed by sera from immunized infants when the strain is grown in vitro, however, in an in vivo passive protection model, the same sera protected infant rats from bacteremia. Finally, using bioluminescent reporters, nadA expression in the infant rat model was induced in vivo at 3 h post-infection. Conclusions: Our results suggest that NadR coordinates a broad transcriptional response to signals present in the human host, enabling the meningococcus to adapt to the relevant host niche. During infectious disease the effect of the same signal on NadR changes between different targets. In particular NadA expression is induced in vivo, leading to efficient killing of meningococcus by anti-NadA antibodies elicited by the 4CMenB vaccine.

Screening and treatment to prevent sequelae in women with Chlamydia trachomatis genital infection: how much do we know?

Background. An important question for chlamydia control programs is the extent to which finding and treating prevalent, asymptomatic Chlamydia trachomatis genital infection reduces reproductive sequelae in infected women. Methods. We reviewed the literature to critically evaluate evidence on the effect of chlamydia screening on development of sequelae in infected women. Results. Two randomized controlled trials of 1-time screening for chlamydial infection—in a Seattle-area health maintenance organization and a Danish school district—revealed that screening was associated with an ∼50% reduction in the incidence of pelvic inflammatory disease over the following year. However, both of these trials had methodological issues that may have affected the magnitude of observed screening benefits and might limit generalizability to other populations. A large, nonrandomized cohort of chlamydia screening among US Army recruits, although limited by lack of outpatient data, did not find a benefit of similar magnitude to the randomized trials. Methodological limitations restrict valid conclusions about individual benefits of screening using data from historical cohorts and ecological studies. We identified no trials directly evaluating the effect of chlamydia screening on subclinical tubal inflammation or damage, ectopic pregnancy, or tubal factor infertility and no studies addressing the effects of >1 round of screening, the optimal frequency of screening, or the benefits of screening for repeat infections. Conclusions. Additional studies of the effectiveness of chlamydia screening would be valuable; feasible study designs may depend on the degree to which screening programs are already established. In addition, better natural history data on the timing of tubal inflammation and damage after C. trachomatis infection and development of more accurate, noninvasive tools to assess chlamydial sequelae are essential to informing chlamydia control efforts.

Risk of sequelae after Chlamydia trachomatis genital infection in women

Chlamydia trachomatis infection, the most common reportable disease in the United States, can lead to pelvic inflammatory disease (PID), infertility, ectopic pregnancy, and chronic pelvic pain. Although C. trachomatis is identified among many women who receive a diagnosis of PID, the incidence and timing of PID and long-term sequelae from an untreated chlamydial infection have not been fully determined. This article examines evidence reviewed as part of the Centers for Disease Control and Prevention Chlamydia Immunology and Control Expert Advisory Meeting; 24 reports were included. We found no prospective studies directly assessing risk of long-term reproductive sequelae, such as infertility, after untreated C. trachomatis infection. Several studies assessed PID diagnosis after untreated chlamydial infection, but rates varied widely, making it difficult to determine an overall estimate. In high-risk settings, 2%-5% of untreated women developed PID within the approximately 2-week period between testing positive for C. trachomatis and returning for treatment. However, the rate of PID progression in the general, asymptomatic population followed up for longer periods appeared to be low. According to the largest studies, after symptomatic PID of any cause has occurred, up to 18% of women may develop infertility. In several studies, repeated chlamydial infection was associated with PID and other reproductive sequelae, although it was difficult to determine whether the risk per infection increased with each recurrent episode. The present review critically evaluates this body of literature and suggests future research directions. Specifically, prospective studies assessing rates of symptomatic PID, subclinical tubal damage, and long-term reproductive sequelae after C. trachomatis infection; better tools to measure PID and tubal damage; and studies on the natural history of repeated chlamydial infections are needed.

Comparative transcriptomics of extreme phenotypes of human HIV-1 infection and SIV infection in sooty mangabey and rhesus macaque

High levels of HIV-1 replication during the chronic phase of infection usually correlate with rapid progression to severe immunodeficiency. However, a minority of highly viremic individuals remains asymptomatic and maintains high CD4⁺ T cell counts. This tolerant profile is poorly understood and reminiscent of the widely studied nonprogressive disease model of SIV infection in natural hosts. Here, we identify transcriptome differences between rapid progressors (RPs) and viremic nonprogressors (VNPs) and highlight several genes relevant for the understanding of HIV-1-induced immunosuppression. RPs were characterized by a specific transcriptome profile of CD4⁺ and CD8⁺ T cells similar to that observed in pathogenic SIV-infected rhesus macaques. In contrast, VNPs exhibited lower expression of interferon-stimulated genes and shared a common gene regulation profile with nonpathogenic SIV-infected sooty mangabeys. A short list of genes associated with VNP, including CASP1, CD38, LAG3, TNFSF13B, SOCS1, and EEF1D, showed significant correlation with time to disease progression when evaluated in an independent set of CD4⁺ T cell expression data. This work characterizes 2 minimally studied clinical patterns of progression to AIDS, whose analysis may inform our understanding of HIV pathogenesis.

A natural freshwater origin for two chlamydial species, Candidatus Piscichlamydia salmonis and Candidatus Clavochlamydia salmonicola, causing mixed infections in wild brown trout (Salmo trutta)

Gill disease in salmonids is characterized by a multifactorial aetiology. Epitheliocystis of the gill lamellae caused by obligate intracellular bacteria of the order Chlamydiales is one known factor; however, their diversity has greatly complicated analyses to establish a causal relationship. In addition, tracing infections to a potential environmental source is currently impossible. In this study, we address these questions by investigating a wild brown trout (Salmo trutta) population from seven different sites within a Swiss river system. One age class of fish was followed over 18 months. Epitheliocystis occurred in a site-specific pattern, associated with peak water temperatures during summer months. No evidence of a persistent infection was found within the brown trout population, implying an as yet unknown environmental source. For the first time, we detected 'Candidatus Piscichlamydia salmonis' and 'Candidatus Clavochlamydia salmonicola' infections in the same salmonid population, including dual infections within the same fish. These organisms are strongly implicated in gill disease of caged Atlantic salmon in Norway and Ireland. The absence of aquaculture production within this river system and the distance from the sea, suggests a freshwater origin for both these bacteria and offers new possibilities to explore their ecology free from aquaculture influences.

Incidence of severe reproductive tract complications associated with diagnosed genital chlamydial infection: the Uppsala Women's Cohort Study

OBJECTIVE: To estimate the cumulative incidence of severe complications associated with genital chlamydia infection in the general female population. METHODS: The Uppsala Women's Cohort Study was a retrospective population based cohort study in Sweden, linking laboratory, hospital, and population registers. We estimated the cumulative incidence of hospital diagnosed pelvic inflammatory disease, ectopic pregnancy, and infertility, and used multivariable regression models to estimate hazard ratios according to screening status. RESULTS: We analysed complete data from 43 715 women in Uppsala aged 15-24 years between January 1985 and December 1989. Follow up until the end of 1999 included 709 000 woman years and 3025 events. The cumulative incidence of pelvic inflammatory disease by age 35 years was 3.9% (95% CI 3.7% to 4.0%) overall: 5.6% (4.7% to 6.7%) in women who ever tested positive for chlamydia, 4.0% (3.7% to 4.4%) in those with negative tests, and 2.9% (2.7% to 3.2%) in those who were never screened. The corresponding figures were: for ectopic pregnancy, 2.3% (2.2% to 2.5%) overall, 2.7% (2.1% to 3.5%), 2.0% (1.8% to 2.3%), and 1.9% (1.7% to 2.1%); and for infertility, 4.1% (3.9% to 4.3%) overall, 6.7% (5.7% to 7.9%), 4.7% (4.4% to 5.1%), and 3.1% (2.8% to 3.3%). Low educational attainment was strongly associated with the development of all outcomes. CONCLUSIONS: The incidence of severe chlamydia associated complications estimated from ours, and other population based studies, was lower than expected. Studies that incorporate data about pelvic inflammatory disease diagnosed in primary care and behavioural risk factors would further improve our understanding of the natural history of chlamydia. Our results provide reassurance for patients, but mean that the benefits of chlamydia screening programmes might have been overestimated.

Influence of inhibitory killer immunoglobulin-like receptors and their HLA-C ligands on resolving hepatitis C virus infection

An estimated 2%-3% of the world's population is chronically infected with hepatitis C virus (HCV) and this is a major cause of liver disease worldwide. Following acute infection, outcome is variable with acute HCV successfully resolved in some individuals (20%-30%), but in the majority of cases the virus is able to persist. Co-infection with human immunodeficiency virus has been associated with a negative impact on the course of HCV infection. The host's immune response is an important correlate of HCV infection outcome and disease progression. Natural killer (NK) cells provide a major component of the antiviral immune response by recognising and killing virally infected cells. NK cells modulate their activity through a combination of inhibitory and activatory receptors such as the killer immunoglobulin-like receptors (KIRs) that bind to human leukocyte antigen (HLA) Class I molecules. In this workshop component, we addressed the influence of KIR genotypes and their HLA ligands on resolving HCV infection and we discuss the implications of the results of the study of Lopez-Vazquez et al. on KIR and HCV disease progression.

Natural antibodies target virus-antibody complexes to organized lymphoid tissue

Natural antibodies (NA) specific for infectious pathogens are found at low titer (usually <1:40) in the serum of healthy, non-immunized, individuals. Therefore, NA are part of the first line of defence against blood borne microorganisms. They directly neutralize viral infections or lyse pathogens by activating the complement cascade. In addition, recent studies highlighted their role in the pooling of infectious pathogens and other antigens to the spleen. This prevents infection of vital target organs and enhances the induction of adaptive immune responses. Specific T and B-cell responses are exclusively induced in highly organized secondary lymphoid organs including lymph nodes and the spleen. As a consequence, mice with disrupted microorganisation of lymphoid organs have defective adaptive immunity. In addition, some pathogens including lymphocytic choriomeningitis virus (LCMV), Leishmania and HIV developed strategies to destroy the splenic architecture in order to induce an acquired immunosuppression and to establish persistent infection. NA antibodies enhance early neutralizing antibodies in the absence of T help mainly by targeting antigen to the splenic marginal zone. In addition, by activating the complement cascade, NA enhance T cell and T-cell dependent B-cell responses. Therefore, natural antibodies are an important link between innate and adaptive immunity.

Polyclonal and specific antibodies mediate protective immunity against enteric helminth infection

Anti-helminth immunity involves CD4+ T cells, yet the precise effector mechanisms responsible for parasite killing or expulsion remain elusive. We now report an essential role for antibodies in mediating immunity against the enteric helminth Heligmosomoides polygyrus (Hp), a natural murine parasite that establishes chronic infection. Polyclonal IgG antibodies, present in naive mice and produced following Hp infection, functioned to limit egg production by adult parasites. Comparatively, affinity-matured parasite-specific IgG and IgA antibodies that developed only after multiple infections were required to prevent adult worm development. These data reveal complementary roles for polyclonal and affinity-matured parasite-specific antibodies in preventing enteric helminth infection by limiting parasite fecundity and providing immune protection against reinfection, respectively. We propose that parasite-induced polyclonal antibodies play a dual role, whereby the parasite is allowed to establish chronicity, while parasite load and spread are limited, likely reflecting the long coevolution of helminth parasites with their hosts.

Subcutaneous infection model facilitates treatment assessment of secondary Alveolar echinococcosis in mice.

Alveolar echinococcosis (AE) in humans is a parasitic disease characterized by severe damage to the liver and occasionally other organs. AE is caused by infection with the metacestode (larval) stage of the fox tapeworm Echinococcus multilocularis, usually infecting small rodents as natural intermediate hosts. Conventionally, human AE is chemotherapeutically treated with mebendazole or albendazole. There is, however still the need for improved chemotherapeutical options. Primary in vivo studies on drugs of interest are commonly performed in small laboratory animals such as mice and Mongolian jirds, and in most cases, a secondary infection model is used, whereby E. multilocularis metacestodes are directly injected into the peritoneal cavity or into the liver. Disadvantages of this methodological approach include risk of injury to organs during the inoculation and, most notably, a limitation in the macroscopic (visible) assessment of treatment efficacy. Thus, in order to monitor the efficacy of chemotherapeutical treatment, animals have to be euthanized and the parasite tissue dissected. In the present study, mice were infected with E. multilocularis metacestodes through the subcutaneous route and were then subjected to chemotherapy employing albendazole. Serological responses to infection were comparatively assessed in mice infected by the conventional intraperitoneal route. We demonstrate that the subcutaneous infection model for secondary AE facilitates the assessment of the progress of infection and drug treatment in the live animal.

Persistent infections after natural transmission of bovine viral diarrhoea virus from cattle to goats and among goats

Bovine viral diarrhoea virus (BVDV) is an economically important pathogen of cattle worldwide. Infection of a pregnant animal may lead to persistent infection of the foetus and birth of a persistently infected (PI) calf that sheds the virus throughout its life. However, BVD viruses are not strictly species specific. BVDV has been isolated from many domesticated and wild ruminants. This is of practical importance as virus reservoirs in non-bovine hosts may hamper BVDV control in cattle. A goat given as a social companion to a BVDV PI calf gave birth to a PI goat kid. In order to test if goat to goat infections were possible, seronegative pregnant goats were exposed to the PI goat. In parallel, seronegative pregnant goats were kept together with the PI calf. Only the goat to goat transmission resulted in the birth of a next generation of BVDV PI kids whereas all goats kept together with the PI calf aborted. To our knowledge, this is the first report which shows that a PI goat cannot only transmit BVD virus to other goats but that such transmission may indeed lead to the birth of a second generation of PI goats. Genetic analyses indicated that establishment in the new host species may be associated with step-wise adaptations in the viral genome. Thus, goats have the potential to be a reservoir for BVDV. However, the PI goats showed growth retardation and anaemia and their survival under natural conditions remains questionable.