Potential biomarkers associated with discrimination between latent and active pulmonary tuberculosis

SETTING

A third of the world's population has latent tuberculous infection (LTBI). Current TB diagnostics used in developing countries are ineffective and are unable to distinguish LTBI from active TB. Identifying biomarkers that could aid in the early detection of TB and in distinguishing TB states could be a major breakthrough in global TB control.

OBJECTIVE

To identify potential immune biomarkers to distinguish active TB from LTBI.

DESIGN

A cross-sectional study was conducted among 19 active TB patients, 8 TB-negative individuals (controls) and 16 LTBI non-human immunodeficiency virus infected individuals in Nairobi, Kenya. Excess supernatants from the QuantiFERON®-TB Gold In-Tube test were used to measure immune analytes using a Th17-focused Milliplex® assay.

RESULTS

Overall antigen-specific responses were higher in the LTBI group than in active TB patients and controls. Interleukin (IL) 17F, macrophage inflammatory protein 3 alpha (MIP-3α), IL-13, IL-17A, IL-5, interferon-gamma (IFN-γ), IL-9, IL-1β and IL-2 were significantly differentially produced by individuals with LTBI and active TB patients. Receiver operator curve analysis revealed good discriminative abilities of these analytes. Co-expression analysis highlighted uniquely co-expressed cytokine pairs between TB groups.

CONCLUSION

These findings suggest that IL-17F, MIP-3α, IL-13, IL-17A, IL-5, IL-9, IL-1β and IL-2, in addition to IFN-γ, could identify and uniquely discriminate between TB states.

Latent tuberculosis infection: An overview

Latent tuberculosis infection (LTBI) is defined as a state of persistent immune response to stimulation by Mycobacterium tuberculosis antigens without evidence of clinically manifested active tuberculosis (TB) disease. Individuals with LTBI represent a reservoir for active TB cases. The detection and management of LTBI is now a key component of the World Health Organization's End TB Strategy and the Government of Canada's federal framework for action on TB prevention and control. This is because people with LTBI can progress to active TB or undergo reactivation, a risk that is greatly increased in those with immunocompromising conditions. This overview provides a summary of LTBI and reactivation risk, as well as the recent advances in the diagnosis and treatment of LTBI.

Automation for clinical CD4 T-cell enumeration, a desirable tool in the hands of skilled operators

BACKGROUND

Automation in HIV clinical flow cytometry when appropriately applied brings considerable standardisation benefits. The Canadian Immunology Quality Assessment Program (CIQAP) detected situations where operators did not manually override automated software in the event of improper output on the Epics XL and FC500 CD4 immunophenotyping platforms. The automated gating algorithm identifies lymphocytes using a double gate strategy based on CD45 × side scatter (SS) gating and a light scatter FS × SS gate known to fail with sub optimal specimens.

METHOD

To generate correct interpretation and results CIQAP introduced a simple protocol modification, bypassing the light scatter gate to include all cells characterized by the CD45 gate. Seventeen problem cases were reanalysed for both absolute and relative T-cell subsets accuracy and compared to the CIQAP group mean values. Results were found to be associated with the percentage of lymphocytes excluded by the automated light scatter gate.

RESULTS

The modified manual protocol resolved poor performance in 14 instances out of 17 problem cases. It was found to improve accuracy when the light scatter gate excluded greater than 5% of the cells. The remaining three cases had a lymphocyte recovery of greater than 94.6% in the original automated analysis.

CONCLUSION

There is a risk in relying solely on automated gating procedures when using the Epics XL and FC500 CD4 immunophenotyping platforms. Laboratory managers have the responsibility to intervene when required. EQA providers are equally responsible to alert the clinical laboratories of the need to update operator training to deal with stressed specimens. © 2016 International Clinical Cytometry Society.

Comprehensive proteomic study identifies serpin and cystatin antiproteases as novel correlates of HIV-1 resistance in the cervicovaginal mucosa of female sex workers

Not all individuals exposed to HIV-1 become infected, and evidence from HIV-1 highly exposed seronegative women (HIV-1-resistant) suggests that mucosal factors in the female genital tract, the first site of contact for the virus, are playing a role. To better understand factors mediating protection from HIV-1, we performed a large clinical study using the tools of systems biology to fully characterize the cervicovaginal mucosa proteome in HIV-1-resistant women. Cervicovaginal lavage fluid was collected from 293 HIV-1-resistant, uninfected, and infected sex workers and analyzed by 2D-LC LTQ-FT-MS. Of the more than 360 unique proteins identified, 41 were differentially abundant (>3-fold cutoff) in HIV-1-resistant women. The majority of over-abundant proteins were antiproteases (>40%), some with described anti-inflammatory and anti-HIV-1 activity. Quantification of specific anti-HIV-1 antiproteases Serpin A1, Serpin A3, and Cystatin B and an epithelial antiprotease A2ML1 found them to be significantly over-abundant in HIV-1-resistant women (p = 0.004; p = 0.046; p = 0.0003; and p = 0.04, respectively). Expression levels were not correlated to sexual practices or other epidemiological factors. Mucosal antiprotease levels correlated with pro-inflammatory cytokine concentration (p = <0.0001), but independently of pro-inflammatory cytokine levels in HIV-1-resistant women including TNF-alpha, IL-1 alpha, IL-1 beta, IL-6, and IL-8. This comprehensive systems biology approach identifies mucosal serpins and cystatins as novel correlates of HIV-1-resistance. This represents the first study characterizing these factors in the female genital tract.

Defining the genital immune correlates of protection against HIV acquisition: co-infections and other potential confounders

The sexual transmission of HIV is very inefficient, presumably because mucosal immune defences prevent infection after most exposures. Since numerous genital immune factors have antiviral effects in vitro, their elucidation might greatly inform the microbicide and HIV prevention fields, particularly in the context of HIV-exposed but persistently seronegative (ESN) individuals. However, several important confounders must be considered in such research. First, sound epidemiological criteria are needed to define individuals as ESN. Then, since high-risk sexual activity is commonly one of these criteria, its potential impact on genital immunology must be carefully considered, both the direct effects of sex and the secondary immune effects of genital co-infections. This means that it may be very difficult to determine whether differences in genital immunology between ESN and control groups are responsible for HIV protection, or are a consequence of high-risk sexual activity. To overcome this confounding, the demographics and epidemiology of ESN cohorts must be described very carefully, thorough co-infection diagnostics must be performed and, if possible, prospective studies with an endpoint of HIV acquisition should be performed to define the direction of causality.

Improved mRNA quantitation in LightCycler RT-PCR

BACKGROUND

Real-time polymerase chain reaction (PCR) utilizing the LightCycler and similar systems is an increasingly used technique for quantitative reverse transcription (RT)-PCR of mRNA levels from genes of immunologic interest. A commonly encountered limitation with these systems is that the fluorescence induced by SYBR Green (a fluorophore that binds double-stranded DNA) can result from primer dimers (PDs) as well as the PCR product of interest, thus interfering with the ability to reproducibly quantitate mRNA levels.

METHODS

We use a modification of the LightCycler PCR strategy to overcome this problem by altering the PCR strategy to take advantage of the LightCycler's ability to measure fluorescence at a temperature greater than the melting point of PDs. The resulting measurements determine fluorescence of only the desired PCR product.

RESULTS

We demonstrate that by using this modified PCR strategy, one can eliminate the fluorescence induced by PDs and obtain accurate product quantitation.

CONCLUSIONS

This simple modification allows more precise quantitation of sample mRNA levels by eliminating the contaminating fluorescence induced by the formation of PCR PDs. This modification obviates the need to redesign PCR primers in RT-PCR experiments where this is impractical or impossible.

HIV-1-specific cellular immune responses among HIV-1-resistant sex workers

The goal of the present study was to determine whether there were HIV-1 specific cellular immune responses among a subgroup of women within a cohort of Nairobi prostitutes (n = 1800) who, despite their intense sexual exposure to HIV-1, are epidemiologically resistant to HIV-1 infection. Of the 80 women defined to be resistant, 24 were recruited for immunological evaluation. The HIV-1-specific T-helper responses were determined by IL-2 production following stimulation with HIV-1 envelope peptides and soluble gp120. Cytotoxic T lymphocyte responses were determined by lysis of autologous EBV-transformed B cell lines infected with control vaccinia virus or recombinant vaccinia viruses containing the HIV-1 structural genes env, gag and pol. Resistant women had significantly increased HIV-1 specific T-helper responses, as determined by in vitro IL-2 production to HIV-1 envelope peptides and soluble glycoprotein 120, compared with low-risk seronegative and HIV-1-infected controls (P < or = 0.01, Student's t-test). Seven of the 17 (41%) resistant women showed IL-2 stimulation indices > or = 2.0. HIV-1-specific CTL responses were detected among 15/22 (68.2%) resistant women compared with 0/12 low-risk controls (Chi-squared test, P < 0.001). In the two resistant individuals tested, the CTL activity was mediated by CD8+ effectors. Many HIV-1-resistant women show evidence of HIV-1-specific T-helper and cytotoxic responses. These data support the suggestion that HIV-1-specific T-cell responses contribute to protection against HIV-1 infection.

Acute sexually transmitted infections increase human immunodeficiency virus type 1 plasma viremia, increase plasma type 2 cytokines, and decrease CD4 cell counts

In Kenya, the median incubation time to AIDS in seroconverting sex workers is 4 years; this incubation time is specific to female sex workers. We studied the influence of acute sexually transmitted infections (STIs) on several immunologic parameters in 32 human immunodeficiency virus type 1 (HIV-1)-positive and 10 HIV-1-negative women sex workers who were followed for 1-5 months. Plasma cytokines, soluble cytokine receptors, CD4 and CD8 T cell counts, and HIV-1 plasma viremia were quantitated before, during, and after episodes of STI. Increases in interleukin (IL)-4, IL-6, IL-10, soluble tumor necrosis factor (TNF)-alpha, and viremia and a decline in CD4(+) T cell counts occurred during gonococcal cervicitis and returned to baseline after treatment. Increases in viremia correlated with increased IL-4 and decreased IL-6 concentrations. Similar changes were seen among women with acute pelvic inflammatory disease. Acute bacterial STI resulted in increased HIV-1 viremia. This may be mediated through increased inflammatory cytokines or through modulation of immune responses that control HIV-1 viremia.

Influence of HLA supertypes on susceptibility and resistance to human immunodeficiency virus type 1 infection

Certain human leukocyte antigens, by presenting conserved immunogenic epitopes for T cell recognition, may, in part, account for the observed differences in human immunodeficiency virus type 1 (HIV-1) susceptibility. To determine whether HLA polymorphism influences HIV-1 susceptibility, a longitudinal cohort of highly HIV-1-exposed female sex workers based in Nairobi, Kenya, was prospectively analyzed. Decreased HIV-1 infection risk was strongly associated with possession of a cluster of closely related HLA alleles (A2/6802 supertype; incidence rate ratio [IRR], 0.45; 95% confidence interval [CI], 0.27-0.72; P=.0003). The alleles in this supertype are known in some cases to present the same peptide epitopes for T cell recognition. In addition, resistance to HIV-1 infection was independently associated with HLA DRB1*01 (IRR, 0.22; 95% CI, 0.06-0.60; P=.0003), which suggests that anti-HIV-1 class II restricted CD4 effector mechanisms may play an important role in protecting against viral challenge. These data provide further evidence that resistance to HIV-1 infection in this cohort of sex workers is immunologically mediated.

Identifying inflorescence phytoliths from selected species of wheat (Triticum monococcum, T. dicoccon, T. dicoccoides, and T. aestivum) and barley (Hordeum vulgare and H. spontaneum) (Gramineae)

Analysis of microfossil silica phytoliths is becoming an increasingly important research tool for taxonomists, archaeobotanists, and paleoecologists. Expanded use of phytolith analysis by researchers is dependent upon development of phytolith systematics. In this study phytoliths produced by the inflorescence bracts from four species of wheat, Triticum monoccocum, T. dicoccon, T. dicoccoides, and T. aestivum, and two species of barley, Hordeum vulgare, and H. spontaneum, were analyzed using computer-assisted image and statistical analysis with the intent to develop taxonomic tools to distinguish among the taxa. A classification key based on significant differences among the mean morphometries of the inflorescence phytoliths produced by each species was created and tested. Discriminant analysis of the morphometries of several morphotypes of phytoliths was also conducted to determine whether this computer-assisted statistical procedure could be used as another method to classify the taxa and to determine which morphotypes have measurements that can best be used in discriminant functions. Test results indicated that, at the genus level, both the classification key and discriminant analysis of certain morphotypes of phytoliths were relatively reliable tools for distinguishing among phytoliths produced in the inflorescence bracts of the taxa considered. For distinguishing among the taxa at the species level, the classification key was most reliable. Of the discriminant analyses tested, that based on all the phytolith morphotypes combined was more reliable than those based on only one morphotype.

Resistance to HIV-1 infection among highly exposed sex workers in Nairobi: what mediates protection and why does it develop?

Variability in susceptibility to infection and disease caused by infectious agents is a characteristic of all populations. Among susceptible individuals exposed to an infection, not all become infected and among infected individuals, not all develop disease. It seems logical that variability in susceptibility to infection and disease would apply to infection and disease with human immunodeficiency viruses. However, until recently, it has been generally held that there is no natural immunity to HIV-1 and that once infected, all individuals would ultimately succumb to AIDS.

HIV-1-specific mucosal IgA in a cohort of HIV-1-resistant Kenyan sex workers

OBJECTIVES

Most HIV-1 transmission is sexual; therefore, immune responses in the genital mucosa may be important in mediating protection against HIV infection. This study examined HIV-1-specific mucosal IgA in a cohort of HIV-1-resistant Kenyan female sex workers.

METHODS

HIV-1-specific immune responses were compared in HIV-1-resistant and HIV-1-infected sex workers, and in lower risk uninfected women. Cervical and vaginal samples from each group were tested for HIV-1-specific IgA and IgG by enzyme immunoassay. Systemic T-helper lymphocyte cell responses to HIV-1 envelope peptide epitopes were assayed using an interleukin 2 bioassay. HIV-1 risk-taking behaviours were assessed using standardized questionnaires.

RESULTS

HIV-1-specific IgA was present in the genital tract of 16 out of 21 (76%) HIV-1-resistant sex workers, five out of 19 (26%) infected women, and three out of 28 (11%) lower risk women (P < 0.0001). Among lower risk women, the presence of HIV-1-specific IgA was associated with HIV-1 risk-taking behaviour. Systemic T-helper lymphocyte responses to HIV-1 envelope peptides were present in 11 out of 20 (55%) HIV-1-resistant women, four out of 18 (22%) infected women, and one out of 25 (4%) lower risk women (P < 0.001). T-helper lymphocyte responses did not correlate with the presence or titre of virus-specific mucosal IgA in any study group.

CONCLUSIONS

HIV-1-specific IgA is present in the genital tract of most HIV-1-resistant Kenyan sex workers, and of a minority of lower risk uninfected women, where it is associated with risk-taking behaviour. These data suggest a role for mucosal HIV-1-specific IgA responses in HIV-1 resistance, independent of host cellular responses.

Naturally occurring IgG anti-HLA alloantibody does not correlate with HIV type 1 resistance in Nairobi prostitutes

In an effort to identify an immunological basis for natural resistance to HIV-1 infection, we have examined serum antibody responses to HLA class I antigens in female prostitutes of the Nairobi Sex Workers Study. Anti-HLA antibodies are known to block HIV infectivity in vitro and can be protective against SIV challenge in macaques immunized with purified class I HLA. Thus, it was postulated that broadly cross-reactive alloantibodies recognizing common HLA alleles in the client population might contribute to the prevention of heterosexual transmission of HIV. In fact, 12% of the women were found to have serum IgG antibodies against class I alloantigens. However, this alloantibody did not correlate with the HIV status of the women and was found in a similar proportion of HIV-positive and HIV-resistant women. The observed levels of alloantibody did not increase with HIV infection in susceptible individuals, suggesting that potential antigenic mimicry between HIV and host HLA class I antigens does not significantly increase levels of anti-class I antibodies. The lack of correlation between serum anti-allo-class I HLA antibodies and the risk of sexual transmission indicates that this humoral immune response is unlikely to be the natural mechanism behind the HIV-resistance phenotype of persistently HIV-seronegative women. This result, however, does not preclude the further investigation of alloimmunization as an artificial HIV immunization strategy.