HIV-1 and the Mycobacterium tuberculosis granuloma: A systematic review and meta-analysis

Infection with HIV-1 greatly increases the risk of active tuberculosis (TB). Although hypotheses suggest HIV-1 disrupts Mycobacterium tuberculosis (Mtb) granuloma function, few studies have examined this directly. The objective of this study was to determine what evidence exists about the effect HIV-1 co-infection has upon Mtb granulomas. A systematic search of PubMed, Web of Science, and Medline up to 20 March 2015 was conducted, to identify studies comparing Mtb-infected tissue from HIV-1 infected and uninfected persons, or HIV-1 infected persons with stratified peripheral CD4 T cell (pCD4) counts. We summarized findings that focused on how HIV-1 changes granuloma formation, bacterial presence, cellular composition, and cytokine production. Nineteen studies with a combined sample size of 899 persons were included. Although studies frequently were limited by variable or inadequately described definitions of outcomes and analytical methods, HIV-1 was found to be associated with increased bacillary load within Mtb-infected tissue. Reductions in pCD4 counts within co-infected persons associated with both poorer granuloma formation and higher bacterial load. The high degree of heterogeneity among studies combined with experimental limitations made it difficult to conclusively support previously published and prevalent hypotheses about HIV-1/Mtb co-infection granulomas. To elucidate the validity of these hypotheses we have described areas that can be improved in future studies in order to clarify the influence HIV-1 co-infection has upon the Mtb granuloma.

The cytopathology of mycobacterial infection

Mycobacterial infection, tuberculosis (TB) in particular, remains one of the world's deadliest communicable diseases in adults and particularly in children, in low and middle income countries. The combination of human immunodeficiency virus (HIV) and TB is often lethal with TB accounting for 25% of deaths in the HIV population. One of the cornerstones for reducing the TB epidemic is early case detection using high quality diagnostic techniques. Cytology, especially fine needle aspiration biopsy (FNAB) is able to diagnose mycobacterial infection in a rapid and cost-effective manner without requiring surgery, thus allowing appropriate management to be quickly instituted. Confirmatory ancillary tests can effectively be performed on cytologic material. In this review, the pertinent cytomorphology of mycobacterial infection in various exfoliative and FNAB specimens is presented, in both immunocompetent and immunosuppressed patients. In the immunosuppressed, the typical cytomorphology of caseating granulomatous inflammation may not be seen but suppurative necrotic inflammation, mycobacterial spindle pseudotumour or a specimen comprised entirely of necrosis may be seen instead. This review includes discussion of currently available ancillary tests that can be performed on cytologic specimens.

Frequencies of lymphoid T-follicular helper cells obtained longitudinally by lymph node fine-needle aspiration correlate significantly with viral load in SIV-infected rhesus monkeys

BACKGROUND

T-follicular helper (T(FH)) cells are an important population in lymph nodes (LNs) contributing to the generation of highly specific B cells. For SIV studies in rhesus macaques (RM), analysis of LN is necessary, but restricted due to invasive sampling. We applied the minimally invasive LN fine-needle aspiration (LN-FNA) and examined dynamics of T(FH) cells during SIV infection.

MATERIALS AND METHODS

LN-FNA and LN resection were carried out on uninfected RM. Lymphocytes were analyzed by flow cytometry. Additionally, cells obtained by LN-FNA over time from SIV-infected RM were analyzed.

RESULTS

Percentages of lymphocyte subsets were similar in LN aspirates and whole LNs. Analysis of LN aspirates from SIV-infected RM demonstrated a decrease of CD4(+) T cells, while T(FH) cell frequencies increased over time and correlated significantly with plasma viral load.

CONCLUSIONS

By applying LN-FNA, we showed that T(FH) cell expansion in chronic SIV infection is associated with viral load.

Clinico-pathological features of tuberculosis due to Mycobacterium tuberculosis Uganda genotype in patients with tuberculous lymphadenitis: a cross sectional study

Background

Tuberculous lymphadenitis is next to pulmonary tuberculosis as the most common cause of tuberculosis. Uganda genotype, one of the sub-lineages of Mycobacterium tuberculosis, is the most prevalent cause of pulmonary tuberculosis in Uganda. We here investigate the clinicopathological characteristics of patients with tuberculous lymphadenitis infected with M. tuberculosis Uganda genotype compared with those infected with M. tuberculosis non-Uganda genotype strains.

Methods

Between 2010 and 2012, we enrolled 121 patients (mean age 28.5 yrs, male 48%; female 52%) with tuberculous lymphadenitis, and categorized them by their M. tuberculosis genotypes. The clinical features and lymph node cytopathological parameters were compared between patients in the Uganda and non-Uganda categories using a crude and multivariable logistic regression model with adjustment for confounding factors.

Results

Of the 121participants, 56 (46%) were infected with strains of Uganda genotype. Patients infected with this genotype had significantly lower frequency of abdominal lymphadenopathy (odds ratio 0.4, p = 0.046) after adjusting for sex, age and HIV. Abdominal lymphadenopathy was also significantly associated with abnormal chest X-ray (p = 0.027).

Conclusion

Tuberculous lymphadenitis patients infected with M. tuberculosis Uganda genotype were significantly less prone to have abdominal lymphadenopathy indicating potential reduced ability to disseminate and supporting the concept that differences in M. tuberculosis genotype may have clinical implications.

Serial study of lymph node cell subsets using fine needle aspiration in pigtail macaques

Lymphoid tissues are of intense interest for studies of the pathogenesis of human immunodeficiency virus (HIV) in humans and simian immunodeficiency virus (SIV) in macaques but are relatively difficult to sample non-invasively. Fine needle aspiration (FNA) cytology, conventionally a diagnostic procedure for lymphadenopathy, can be used for longitudinal study of tissue cell subsets during HIV/SIV infection. In this study, we serially sampled lymph node (LN) FNA from pigtail macaques and studied cell subsets in the aspect of absolute count, frequency, and functionality by flow cytometry. The median recovered lymphocyte count from FNA samples was 2.01×10(5) (3.0×10(3) to 2.25×10(6), n=38) and median CD4+ T cell subset recovered was 5.94×10(4) (277 to 6.17×10(5), n=38). Although we observed a relatively large variation in the frequencies of cell subsets of FNA samples taken from different time points, the cell subset composition of FNA samples, in particular T cell and CD4+ T cell frequencies, was broadly comparable to whole excised LNs (n=6) and distinct from peripheral blood. A subset of CD4+ T cells that is located almost exclusively in secondary lymphoid tissues, T follicular helper (TFH) cells, was readily identifiable in LN FNAs and the TFH cell frequencies were strongly correlated with B cell frequencies. In vitro functionality of FNA lymphocytes was demonstrated using polyclonal SEB stimulation, resulting in a median 6% of responding CD4+ T cells, comparable to circulating CD4+ T lymphocytes. We conclude that serial sampling of macaque LNs using FNA is a potentially useful method to study the immunopathogenesis of SIV infection and may be extended to HIV infection.