Use of interactive messaging to reduce pre-diagnosis loss to follow-up for TB care

OBJECTIVE: To investigate the uptake and usage of a WhatsApp-based interactive communication strategy to avert pre-diagnosis loss to follow-up (LTFU) from TB care in a high-incidence setting.METHODS: We enrolled adults (≥18 years) who underwent routine sputum TB testing in two primary healthcare clinics in Khayelitsha, Cape Town, South Africa. The intervention consisted of structured WhatsApp-based reminders (prompts) sent prior to a routine clinic appointment scheduled 2-3 days after the diagnostic visit. Pre-diagnosis LTFU was defined as failure to return for the scheduled appointment and within 10 days.RESULTS: We approached 332 adults with presumptive TB, of whom 103 (31%) were successfully enrolled; 213 (64%) did not own a WhatsApp-compatible phone. Of 103 participants, 74 (72%) actively responded to WhatsApp prompts; 69 (67%) opted to include a close contact in group communication to co-receive reminders. Pre-diagnosis LTFU was low overall (n = 7, 6.8%) and was not associated with failure to respond to WhatsApp prompts.CONCLUSION: In this high-incidence setting, enrolment in a WhatsApp-based communication intervention among adults with presumptive TB was low, mainly due to low availability of WhatsApp-compatible phones. Among participants, we observed high message response rates and low LTFU, suggesting potential for interactive messaging services to support pre-diagnosis TB care.

Closing the reporting gap for childhood tuberculosis in South Africa: improving hospital referrals and linkages

Setting

A referral hospital in Cape Town, Western Cape Province, Republic of South Africa.

Objective

To measure the impact of a hospital-based referral service (intervention) to reduce initial loss to follow-up among children with tuberculosis (TB) and ensure the completeness of routine TB surveillance data.

Design

A dedicated TB referral service was established in the paediatric wards at Tygerberg Hospital, Cape Town, in 2012. Allocated personnel provided TB education and counselling, TB referral support and weekly telephonic follow-up after hospital discharge. All children identified with TB were matched to electronic TB treatment registers (ETR.Net/EDRWeb). Multivariable logistic regression was used to compare reporting of culture-confirmed and drug-susceptible TB cases before (2007-2009) and during (2012) the intervention.

Results

Successful referral with linkage to care was confirmed in 267/272 (98%) and successful reporting in 227/272 (84%) children. Children with drug-susceptible, culture-confirmed TB were significantly more likely to be reported during the intervention period than in the pre-intervention period (OR 2.52, 95%CI 1.33-4.77). The intervention effect remained consistent in multivariable analysis (adjusted OR 2.62; 95%CI 1.31-5.25) after adjusting for age, sex, human immunodeficiency virus status and the presence of TB meningitis.

Conclusions

A simple hospital-based TB referral service can reduce initial loss to follow-up and improve recording and reporting of childhood TB in settings with decentralised TB services.

Improving rifampicin-resistant tuberculosis diagnosis using Xpert® MTB/RIF: modelling interventions and costs

SETTING

Cape Town, South Africa.

OBJECTIVE

To model the diagnosis of rifampicin-resistant tuberculosis (RR-TB) and laboratory costs of smear/culture and Xpert-based algorithms and the effect of varying adherence and human immunodeficiency virus (HIV) testing in the Xpert-based algorithm.

METHODS

We used a validated operational model (100 000 population) and published laboratory cost data. We estimated the number and cost of RR-TB cases identified using the smear/culture- and Xpert-based algorithms. We modelled varying adherence and different levels of known HIV status against the Xpert-based algorithm.

RESULTS

The number of RR-TB cases identified increased from 603 with smear/culture to 1178 with the Xpert-based algorithm (100% adherence; 60% knew their HIV status). The overall laboratory cost increased from US$1 073 858 to US$2 430 050 and the cost per RR-TB case identified increased from US$1781 to US$2063 in the respective algorithms. When adherence to the Xpert-based algorithm was increased from 50% to 100% (60% knew their HIV status), the number of RR-TB cases identified increased from 721 to 1178.

CONCLUSION

The Xpert-based algorithm is efficient in identifying RR-TB, as the increase in costs is offset by the increase in the number of cases identified. Adherence to the Xpert-based algorithm is important to ensure that all presumptive TB cases receive the benefit of simultaneous TB and RR-TB testing.

High laboratory cost predicted per tuberculosis case diagnosed with increased case finding without a triage strategy

SETTING

Cape Town, South Africa.

OBJECTIVE

To model the effects of increased case finding and triage strategies on laboratory costs per tuberculosis (TB) case diagnosed.

METHODS

We used a validated operational model and published laboratory cost data. We modelled the effect of varying the proportion with TB among presumptive cases and Xpert cartridge price reductions on cost per TB case and per additional TB case diagnosed in the Xpert-based vs. smear/culture-based algorithms.

RESULTS

In our current scenario (18.3% with TB among presumptive cases), the proportion of cases diagnosed increased by 8.7% (16.7% vs. 15.0%), and the cost per case diagnosed increased by 142% (US$121 vs. US$50). The cost per additional case diagnosed was US$986. This would increase to US$1619 if the proportion with TB among presumptive cases was 10.6%. At 25.9-30.8% of TB prevalence among presumptive cases and a 50% reduction in Xpert cartridge price, the cost per TB case diagnosed would range from US$50 to US$59 (comparable to the US$48.77 found in routine practice with smear/culture).

CONCLUSION

The operational model illustrates the effect of increased case finding on laboratory costs per TB case diagnosed. Unless triage strategies are identified, the approach will not be sustainable, even if Xpert cartridge prices are reduced.

Operational modelling: the mechanisms influencing TB diagnostic yield in an Xpert® MTB/RIF-based algorithm

SETTING

Cape Town, South Africa.

OBJECTIVE

To compare the diagnostic yield for smear/culture and Xpert® MTB/RIF algorithms and to investigate the mechanisms influencing tuberculosis (TB) yield.

METHOD

We developed and validated an operational model of the TB diagnostic process, first with the smear/culture algorithm and then with the Xpert algorithm. We modelled scenarios by varying TB prevalence, adherence to diagnostic algorithms and human immunodeficiency virus (HIV) status. This enabled direct comparisons of diagnostic yield in the two algorithms to be made.

RESULTS

Routine data showed that diagnostic yield had decreased over the period of the Xpert algorithm roll-out compared to the yield when the smear/culture algorithm was in place. However, modelling yield under identical conditions indicated a 13.3% increase in diagnostic yield from the Xpert algorithm compared to smear/culture. The model demonstrated that the extensive use of culture in the smear/culture algorithm and the decline in TB prevalence are the main factors contributing to not finding an increase in diagnostic yield in the routine data.

CONCLUSION

We demonstrate the benefits of an operational model to determine the effect of scale-up of a new diagnostic algorithm, and recommend that policy makers use operational modelling to make appropriate decisions before new diagnostic algorithms are scaled up.

Scanty smears associated with initial loss to follow-up in South African tuberculosis patients

BACKGROUND

Smear-positive patients should be started on anti-tuberculosis treatment promptly. However, studies show that up to 38% of diagnosed patients are initial loss to follow-up (LTFU), meaning they do not start treatment after diagnosis. We investigated determinants of initial LTFU at primary health care facilities.

DESIGN

In a facility-matched case-control study, health care facilities were visited from October 2010 to September 2012. After identification from registers, patients were traced and invited to complete a questionnaire.

RESULTS

Of 973 participants, 233 (24%) were cases and 740 (74%) controls. Initial LTFU was associated with smear grade (pooled adjusted odds ratio [aOR] 0.73, 95% confidence interval [CI] 0.64-0.90, scanty at baseline) for participants identified at facilities, but not with age (overall P = 0.80) or sex (aOR 0.83, 95%CI 0.58-1.20). Of the 233 cases, 197 (85%) were traced in the community, of whom 58 (29%) were found. Among the group found, initial LTFU was associated with age (aOR 3.38, 95%CI 1.15-9.95) and smear grade (aOR 0.08, 95%CI 0.02-0.34, scanty at baseline).

CONCLUSION

Scanty smear positivity was associated with initial LTFU. Tuberculosis programmes should start scanty smear-positive patients on treatment early and develop alternative community tracing strategies. Health care worker training could address the first aspect, and the use of technology to improve treatment initiation, such as mobile phone applications, the second.

Comparing laboratory costs of smear/culture and Xpert® MTB/RIF-based tuberculosis diagnostic algorithms

SETTING

Cape Town, South Africa, where Xpert^® MTB/RIF was introduced as a screening test for all presumptive tuberculosis (TB) cases.

OBJECTIVE

To compare laboratory costs of smear/culture- and Xpert-based tuberculosis (TB) diagnostic algorithms in routine operational conditions.

METHODS

Economic costing was undertaken from a laboratory perspective, using an ingredients-based costing approach. Cost allocation was based on reviews of standard operating procedures and laboratory records, timing of test procedures, measurement of laboratory areas and manager interviews. We analysed laboratory test data to assess overall costs and cost per pulmonary TB and multidrug-resistant TB (MDR-TB) case diagnosed. Costs were expressed as 2013 Consumer Price Index-adjusted values.

RESULTS

Total TB diagnostic costs increased by 43%, from US$440 967 in the smear/culture-based algorithm (April-June 2011) to US$632 262 in the Xpert-based algorithm (April-June 2013). The cost per TB case diagnosed increased by 157%, from US$48.77 (n = 1601) to US$125.32 (n = 1281). The total cost per MDR-TB case diagnosed was similar, at US$190.14 and US$183.86, with 95 and 107 cases diagnosed in the respective algorithms.

CONCLUSION

The introduction of the Xpert-based algorithm resulted in substantial cost increases. This was not matched by the expected increase in TB diagnostic efficacy, calling into question the sustainability of this expensive new technology.

Comparing multidrug-resistant tuberculosis patient costs under molecular diagnostic algorithms in South Africa

SETTING

Ten primary health care facilities in Cape Town, South Africa, 2010-2013.

OBJECTIVE

A comparison of costs incurred by patients in GenoType MDRTBplus line-probe assay (LPA) and Xpert MTB/RIF-based diagnostic algorithms from symptom onset until treatment initiation for multidrug-resistant tuberculosis (MDR-TB).

METHODS

Eligible patients identified from laboratory and facility records were interviewed 3-6 months after treatment initiation and a cost questionnaire completed. Direct and indirect costs, individual and household income, loss of individual income and change in household income were recorded in local currency, adjusted to 2013 costs and converted to $US.

RESULTS

Median number of visits to initiation of MDR-TB treatment was reduced from 20 to 7 (P < 0.001) and median costs fell from US$68.1 to US$38.3 (P = 0.004) in the Xpert group. From symptom onset to being interviewed, the proportion of unemployed increased from 39% to 73% in the LPA group (P < 0.001) and from 53% to 89% in the Xpert group (P < 0.001). Median household income decreased by 16% in the LPA group and by 13% in the Xpert group.

CONCLUSION

The introduction of an Xpert-based algorithm brought relief by reducing the costs incurred by patients, but loss of employment and income persist. Patients require support to mitigate this impact.

Completeness and accuracy of electronic recording of paediatric drug-resistant tuberculosis in Cape Town, South Africa

SETTING

Cape Town, South Africa.

OBJECTIVE

To assess the completeness and accuracy of electronic recording of drug-resistant tuberculosis (DR-TB) in children.

DESIGN

Retrospective cohort study. All children aged <15 years treated for DR-TB during 2012 were included, with clinical data collected from routine health services. Matching was performed between clinical data and an extracted data set from an electronic register for DR-TB (EDR.web), and data sources were compared.

RESULTS

Seventy-seven children were identified clinically, of whom only 49 (64%) were found in EDR.web. Most data in EDR.web were complete and accurate, but there were some internal inconsistencies for confirmed TB. Only 4.4% of all EDR.web entries were children.

CONCLUSION

Only two thirds of children clinically treated for DR-TB were recorded in the electronic reporting system, suggesting under-reporting. We also found a lower than expected prevalence of childhood DR-TB, probably suggesting both under-diagnosis and under-recording of DR-TB in children. Clinicians at facility level should be able to access the electronic reporting system, and data transfer between clinical paper-based and electronic sources should be simplified. Cross-linking between electronic registers for drug-susceptible and DR-TB or consolidation of registers could improve the accuracy of recording. Improved recording and reporting of DR-TB in children is needed.

Decentralised care for the management of child contacts of multidrug-resistant tuberculosis

SETTING

Cape Town, South Africa.

OBJECTIVE

To determine the number of multidrug-resistant tuberculosis (MDR-TB) child contacts routinely identified by health services, and whether a model of decentralised care improves access.

METHODS

All MDR-TB source cases registered in Cape Town from April 2010 to March 2011 were included. All child contacts assessed at hospital and outreach clinics were recorded from May 2010 to June 2011. Electronic probabilistic matching was used to match source cases with potential child contacts; the number of children accessing decentralised (Khayelitsha) and hospital-based care was compared.

RESULTS

Of 1221 MDR-TB source cases identified, 189 (15.5%) were registered in Khayelitsha; 31 (16.4%) had at least one child contact assessed. In contrast, 95 (9.2%) of the 1032 source cases diagnosed in the other Cape Town subdistricts (hospital-based care) had at least one child contact assessed (P = 0.003). Children in Khayelitsha were seen at a median of 71 days (interquartile range [IQR] 37-121 days) after source case diagnosis compared to 90 days (IQR 56-132 days) in other subdistricts (P = 0.15).

CONCLUSION

Although decentralised care led to an increased number of child contacts being evaluated, both models led to the assessment of a small number of potential child MDR-TB contacts, with considerable delay in assessment.

Reasons for the low bacteriological coverage of tuberculosis reported in Mpumalanga Province, South Africa

SETTING

Public sector hospitals and primary health clinics in the Mpumalanga Province of South Africa.

OBJECTIVE

To determine whether failure to adhere to tuberculosis (TB) diagnostic guidelines (i.e., submit sputum for smear microscopy) contributed to the low bacteriological coverage reported for TB in 2008 in Mpumalanga Province.

METHODS

We reviewed clinical records for new pulmonary TB cases at 30 of 118 randomly selected facilities that met the bacteriological coverage target of 80% and 30/87 facilities that did not. Data for hospital and clinic cases were abstracted into case report forms, captured electronically and compared with data from the electronic TB register (ETR). We assessed age, sex, human immunodeficiency virus (HIV) infection and facility type as potential confounders for recording of smear microscopy results.

RESULTS

Age, sex and HIV infection did not influence recording of results. In hospitals, 61.8% of pulmonary TB cases had sputum smear results in their clinical records compared to 93.6% at clinics (P < 0.001). Of the 711 cases (30.3%) that did not have smear results in the ETR, 342 (48.1%) did have smear results in their clinical records.

CONCLUSION

Both poor clinical practice (especially in hospitals) and poor record keeping have contributed to the low bacteriological coverage reported. These shortcomings need to be addressed to improve patient care and programme management.

Symptom reporting among prevalent tuberculosis cases who smoke, are HIV-positive or have hyperglycaemia

Data from a tuberculosis (TB) prevalence survey conducted in 24 communities in Zambia and the Western Cape, South Africa, January-December 2010, were analysed to determine the influence of smoking, hyperglycaemia and human immunodeficiency virus (HIV) infection on TB symptom reporting in culture-confirmed TB cases. Of 123 790 adults eligible for enrolment, 90 601 (73%) consented and 64 463 had evaluable sputum samples. ORs and 95%CIs were calculated using a robust standard errors logistic regression model adjusting for clustering at community level. HIV-positive TB cases were more likely to report cough, weight loss, night sweats and chest pain than non-HIV-positive TB cases. TB cases who smoked or had hyperglycaemia did not report symptoms differently from cases without these comorbidities.

Tuberculosis patients in primary care do not start treatment. What role do health system delays play?

SETTING

Primary health care facilities in five provinces of South Africa.

OBJECTIVE

To investigate the association between the proportion of sputum results with a prolonged smear turnaround time and the proportion of smear-positive tuberculosis (TB) cases initially lost to follow-up.

DESIGN

The unit of investigation was a primary health care facility and the outcome was the initial loss to follow-up rate per facility, which was calculated by comparing the sputum register with the TB treatment register. A prolonged turnaround time was defined as more than 48 h from when the sputum sample was documented in the sputum register to receipt of the result at the facility.

RESULTS

The mean initial loss to follow-up rate was 25% (95%CI 22-28). Smear turnaround time overall was inversely associated with initial loss to follow-up (P = 0.008), when comparing Category 2 (33-66% turnaround time within 48 h) with Category 1 (0-32%) (OR 0.73, 95%CI 0.48-1.13, P = 0.163) and when comparing Category 3 (67-100%) with Category 1 (OR 0.62, 95%CI 0.39-0.99, P = 0.045). The population preventable fraction of initial loss to follow-up (when turnaround time was <48 h in ≥67% of smear results) was 21%.

CONCLUSION

Initial loss to follow-up should be reported as part of the TB programme to ensure that patients are initiated on treatment to prevent transmission within communities.

Capture-recapture to estimate completeness of tuberculosis surveillance in two communities in South Africa

BACKGROUND

Reliable surveillance is essential for any tuberculosis (TB) control programme; however, under-registration of TB cases due to under-notification of patients on treatment or failure to initiate treatment has been well-documented internationally.

OBJECTIVE

To determine the contribution of capture-recapture methods in estimating the completeness of bacteriologically confirmed pulmonary TB registration in two high-incident communities in South Africa.

METHODS

Record linkage between the TB treatment register and two laboratory sputum TB result registers and three-source log-linear capture-recapture analysis.

RESULTS

The number of bacteriologically confirmed pulmonary TB cases in the TB treatment register was 243, with an additional 63 cases identified in the two laboratory databases, resulting in 306 TB cases. The observed completeness of the TB treatment register was 79%. The log-linear model estimated 326 (95%CI 314-355) TB cases, resulting in an estimated completeness of registration of 75% (95%CI 68-77).

CONCLUSION

Capture-recapture can be useful in evaluating the completeness of TB control surveillance and registration, including in resource-limited settings; however, methodology and results should be carefully assessed. Interventions are needed to increase the completeness of registration and to reduce the number of initial defaulters.

Incomplete registration and reporting of culture-confirmed childhood tuberculosis diagnosed in hospital

SETTING

The South African National Tuberculosis Programme (NTP) recommends the registration of tuberculosis (TB) patients at community clinics. TB in children is often diagnosed at referral hospitals, and there are concerns as to whether these children are accurately reflected in routine NTP reporting.

OBJECTIVE

To assess the completeness of registration of children with culture-confirmed TB diagnosed in a referral hospital, in the routine provincial electronic TB register (ETR.Net), and to describe TB treatment outcomes.

DESIGN

A retrospective cohort study including children aged <13 years diagnosed with culture-confirmed TB at Tygerberg Children's Hospital from July 2007 to June 2009. Data on demographic, clinical and referral factors were collated from hospital data sources. Electronic matching was used to identify children in the provincial ETR.Net.

RESULTS

Only 166 of 267 (62%) children were registered in ETR.Net. Children with TB meningitis and death prior to referral were significantly less likely to be registered. Treatment outcome data were available for only 70% of children; favourable outcomes were reported in 56%.

CONCLUSIONS

A large proportion of children diagnosed with confirmed TB at a referral hospital were not registered, resulting in underreporting of the burden and severity of childhood TB. Routine surveillance of childhood TB should include linkage of hospital data.

Accuracy and completeness of recording of confirmed tuberculosis in two South African communities

BACKGROUND

Although tuberculosis (TB) treatment registers and laboratory records are essential tools for recording and reporting in TB control programmes, the accuracy and completeness of routinely collected data are seldom monitored.

OBJECTIVE

To assess the accuracy and completeness of TB treatment register data in two South African urban communities using record linkage.

METHODS

All cases of bacteriologically confirmed TB, defined as two smear-positive results and/or at least one culture-positive result, were included. Record linkage was performed between three data sources: 1) TB treatment registers, 2) the nearest central laboratory, and 3) the referral hospital laboratory.

RESULTS

The TB treatment registers had 435 TB cases recorded, of which 204 (47%) were bacteriologically confirmed. An additional 39 cases recorded as non-bacteriological cases in the TB treatment registers were reclassified as bacteriologically confirmed, and 63 bacteriologically confirmed cases were identified from the laboratory databases that were not recorded in the TB treatment registers. The final number of bacteriologically confirmed TB cases was 306, giving an increase of 50%.

CONCLUSIONS

The accuracy and completeness of the TB treatment register and central laboratory data were inadequate. A high percentage of bacteriologically confirmed cases from both laboratories were not recorded in the TB treatment registers. We are developing an electronic result management system to improve the management of laboratory results.

Changing Mycobacterium tuberculosis population highlights clade-specific pathogenic characteristics

Mycobacterium tuberculosis strains can be classified into a number of major clades according to defined evolutionary markers. It is hypothesised that strains comprising these clades have evolved different properties which may influence a local strain population structure. To investigate this, we analysed the incidence of tuberculosis caused by the predominant clades (Beijing, Haarlem, LAM, Quebec and the Low-Copy Clade) found in a community within the Cape Town metropole in South Africa over a 12-year period. We found that while the incidence of cases infected with strains of the Haarlem, LAM, Quebec and the Low-Copy Clades remained relatively stable, that of cases of the Beijing clade increased exponentially over time, with a doubling time of 4.86 years (P=0.018). This growth was exclusively attributable to drug-susceptible strains. Although drug-resistant Beijing cases remained constant in number, non-Beijing drug-resistant cases declined over time (P=0.007). Drug-susceptible Beijing-infected cases had a greater proportion of smear-positive sputa than their non-Beijing counterparts (P=0.013) and were less likely to be successfully treated (retreatment cases) (P=0.026). Recent evidence suggests that these differences likely reflect enhanced pathogenicity rather than transmissibility. The rapid emergence of Beijing strains demonstrates adaptation to conditions within the study community and poses a grave challenge to future TB control.

Initial default from tuberculosis treatment: how often does it happen and what are the reasons?

A study in 11 primary health care facilities in and around Cape Town determined the proportion of bacteriologically confirmed tuberculosis (TB) cases who did not start treatment (initial default) and identified reasons for it. Databases from centralised laboratories were compared with electronic TB treatment registers. Fourteen per cent (373/2758) of TB suspects were TB cases. Of the 58 (16%) initial defaulters, 14 (24%) died, while 26 (45%) could not be interviewed for address-related reasons. The 18 subjects who were interviewed indicated reasons for initial default that were (56%) or were not (44%) directly linked to services. High initial default rates require improvement in the quality of health services.

Infection control practices in public dental care services: findings from one South African Province

Infection control practices which increase the risk of blood-borne virus transmission with associated dental practice in one South African province were studied. All 24 state dental clinics were observed for adequate provision to carry out good infection prevention and control (IPC) practice, 75 staff including dentists, nurses and dental assistants were interviewed to assess IPC knowledge and 23 dental procedures were observed. Significant findings were the difference between knowledge and practice, despite adequate provisions for safe infection control practice. The lack of protective eye wear during a dental procedure, not washing hands between patients, not disassembling an item prior to disinfection or sterilization, and not using a sterile drill for each patient were identified. A rapid method for detection of occult blood was used as a marker for inadequate IPC practice. Contaminated dental items of equipment just prior to patient use in 25% of equipment tested and 37% of surfaces and surrounding areas in the dental clinics and units were recorded. This study concludes that, despite provision for safe dental practice available in state dental clinics, there was a lack of knowledge application in clinical practice. The risk of blood-borne virus transmission in a population with high human immunodeficiency virus (HIV) prevalence cannot be ignored.

Apoptotic cells overexpress vinculin and induce vinculin-specific cytotoxic T-cell cross-priming

Here we show that apoptotic cells overexpress vinculin and are ingested by dendritic cells, which subsequently cross-prime vinculin-specific cytotoxic T lymphocytes (CTLs). Successful cross-priming requires that the apoptotic cells provide maturation signals to dendritic cells through CD40-CD40 ligand (CD40L) interactions. If apoptotic cells are CD40L-, the help of a third T cell is needed for priming, indicating a regulatory role for apoptotic cells in determining priming or tolerance. Vinculin-specific CTL priming is also related to apoptosis in vivo, given that in HIV-seropositive individuals, the frequency of specific CTLs depends on the proportion of peripheral CD40L+ apoptotic cells.

Mage-3 and influenza-matrix peptide-specific cytotoxic T cells are inducible in terminal stage HLA-A2.1+ melanoma patients by mature monocyte-derived dendritic cells

Dendritic cell (DC) vaccination, albeit still in an early stage, is a promising strategy to induce immunity to cancer. We explored whether DC can expand Ag-specific CD8+ T cells even in far-advanced stage IV melanoma patients. We found that three to five biweekly vaccinations of mature, monocyte-derived DC (three vaccinations of 6 x 106 s.c. followed by two i.v. ones of 6 and 12 x 106, respectively) pulsed with Mage-3A2.1 tumor and influenza matrix A2. 1-positive control peptides as well as the recall Ag tetanus toxoid (in three of eight patients) generated in all eight patients Ag-specific effector CD8+ T cells that were detectable in blood directly ex vivo. This is the first time that active, melanoma peptide-specific, IFN-gamma-producing, effector CD8+ T cells have been reliably observed in patients vaccinated with melanoma Ags. Therefore, our DC vaccination strategy performs an adjuvant role and encourages further optimization of this new immunization approach.

Optimal activation of tumor-reactive T cells by selected antigenic peptide analogues

Many mechanisms have been proposed to explain why immune responses against human tumor antigens are generally ineffective. For example, tumor cells have been shown to develop active immune evasion mechanisms. Another possibility is that tumor antigens are unable to optimally stimulate tumor-specific T cells. In this study we have used HLA-A2/Melan-A peptide tetramers to directly isolate antigen-specific CD8(+) T cells from tumor-infiltrated lymph nodes. This allowed us to quantify the activation requirements of a representative polyclonal yet monospecific tumor-reactive T cell population. The results obtained from quantitative assays of intracellular Ca(2+) mobilization, TCR down-regulation, cytokine production and induction of effector cell differentiation indicate that the naturally produced Melan-A peptides are weak agonists and are clearly suboptimal for T cell activation. In contrast, optimal T cell activation was obtained by stimulation with recently defined peptide analogues. These findings provide a molecular basis for the low immunogenicity of tumor cells and suggest that patient immunization with full agonist peptide analogues may be essential for stimulation and maintenance of anti-tumor T cell responses in vivo.

In vivo expression of natural killer cell inhibitory receptors by human melanoma-specific cytolytic T lymphocytes

Natural killer (NK) receptor signaling can lead to reduced cytotoxicity by NK cells and cytolytic T lymphocytes (CTLs) in vitro. Whether T cells are inhibited in vivo remains unknown, since peptide antigen-specific CD8(+) T cells have so far not been found to express NK receptors in vivo. Here we demonstrate that melanoma patients may bear tumor-specific CTLs expressing NK receptors. The lysis of melanoma cells by patient-derived CTLs was inhibited by the NK receptor CD94/NKG2A. Thus, tumor-specific CTL activity may be decreased through NK receptor triggering in vivo.

An expanded peripheral T cell population to a cytotoxic T lymphocyte (CTL)-defined, melanocyte-specific antigen in metastatic melanoma patients impacts on generation of peptide-specific CTLs but does not overcome tumor escape from immune surveillance in metastatic lesions

It is not known if immune response to T cell-defined human histocompatibility leukocyte antigen (HLA) class I-restricted melanoma antigens leads to an expanded peripheral pool of T cells in all patients, affects cytotoxic T lymphocyte (CTL) generation, and correlates with anti-tumor response in metastatic lesions. To this end, a limiting dilution analysis technique was developed that allowed us to evaluate the same frequency of peptide-specific T cells as by staining T cells with HLA-peptide tetrameric complexes. In four out of nine patients, Melan-A/Mart-1(27-35)-specific CTL precursors (CTLp) were >/=1/2,000 peripheral blood lymphocytes and found mostly or only in the CD45RO(+) memory T cell subset. In the remaining five patients, a low (<1/40,000) peptide-specific CTLp frequency was measured, and the precursors were only in the CD45RA(+) naive T cell subset. Evaluation of CTL effector frequency after bulk culture indicated that peptide-specific CTLs could be activated in all patients by using professional antigen-presenting cells as dendritic cells, but CTLp frequency determined the kinetics of generation of specificity and the final number of effectors as evaluated by both limiting dilution analysis and staining with HLA-A*0201-Melan-A/Mart-1 tetrameric complexes. Immunohistochemical analysis of 26 neoplastic lesions from the nine patients indicated absence of tumor regression in most instances, even in patients with an expanded peripheral T cell pool to Melan-A/Mart-1 and whose neoplastic lesions contained a high frequency of tetramer-positive Melan-A/Mart-1-specific T cells. Furthermore, frequent lack of a "brisk" or "nonbrisk" CD3(+)CD8(+) T cell infiltrate or reduced/absent Melan-A/Mart-1 expression in several lesions and lack of HLA class I antigens were found in some instances. Thus, expansion of peripheral immune repertoire to Melan-A/Mart-1 takes place in some metastatic patients and leads to enhanced CTL induction after antigen-presenting cell-mediated selection, but, in most metastatic lesions, it does not overcome tumor escape from immune surveillance.

Analysis of the cytolytic T lymphocyte response of melanoma patients to the naturally HLA-A*0201-associated tyrosinase peptide 368-376

The human tyrosinase gene codes for two distinct antigens that are recognized by HLA-A*0201-restricted CTLs. For one of them, tyrosinase peptide 368-376, the sequence identified by mass spectrometry in melanoma cell eluates differs from the gene-encoded sequence as a result of posttranslational modification of amino acid residue 370 (asparagine to aspartic acid). Here, we used fluorescent tetrameric complexes ("tetramers") of HLA-A*0201 and tyrosinase peptide 368-376 (YMDGTMSQV) to characterize the CD8+ T-cell response to this antigen in lymphoid cell populations from HLA-A2 melanoma patients. Taking advantage of the presence of significant numbers of tetramer-positive CD8+ T cells in tumor-infiltrated lymph node cells from a melanoma patient, we derived polyclonal and monoclonal tyrosinase peptide 368-376-specific CTLs by tetramer-guided flow cytometric sorting. These CTLs efficiently and specifically lysed HLA-A*0201- and tyrosinase-positive melanoma cells. As assessed with tyrosinase peptide variants, the fine antigen specificity of the CTLs was quite diverse at the clonal level. Flow cytometric analysis of PBMCs stained with tetramers showed that tyrosinase peptide 368-376-specific CD8+ T cells were hardly detectable in peripheral blood of melanoma patients. However, significant numbers of such cells were detected after short-term stimulation of CD8+ lymphocytes with tyrosinase peptide 368-376 in 6 of 10 HLA-A2 melanoma patients. Taken together, these findings emphasize the significant contribution of the natural tyrosinase peptide 368-376 to the antigenic specificities recognized by the tumor-reactive CTLs that may develop in HLA-A2 melanoma patients.

An antigen-targeted approach to adoptive transfer therapy of cancer

Previous attempts to treat human malignancies by adoptive transfer of tumor-specific CTLs have been limited by the difficulty of isolating T cells of defined antigen specificity. The recent development of MHC class I/antigenic peptide tetrameric complexes that allow direct identification of antigen-specific T cells has opened new possibilities for the isolation and in vitro expansion of tumor-specific T cells. In the present study, we have derived polyclonal monospecific cell lines from circulating Melan-A-specific CTL precursors of HLA-A*0201+ melanoma patients by combining stimulation with recently identified peptide analogues of the immunodominant epitope from the melanoma-associated antigen Melan-A with staining with fluorescent HLA-A*0201/Melan-A peptide tetramers. In vitro expansion of antigen-specific CD8+ T cells was monitored by flow cytometry with the fluorescent tetramers and anti-CD8 monoclonal antibody. This analysis revealed that Melan-A 26-35 peptide analogues were much more efficient than the parental peptides in stimulating a rapid in vitro expansion of antigen-specific CD8+ T cells. These cells were then isolated by tetramer-guided cell sorting and subsequently expanded in vitro by mitogen stimulation. The resulting polyclonal but monospecific CTLs fully cross-recognized the parental peptides and were able to efficiently lyse Melan-A-expressing tumor cells. Altogether, these results pave the way to a molecularly defined approach to antigen-specific adoptive transfer therapy of cancer.

Human myelomonocytic cells express an inhibitory receptor for classical and nonclassical MHC class I molecules

Leukocyte activation can be negatively regulated by inhibitory receptors specific for MHC class I molecules. While one inhibitory receptor, Ig-like transcript 2 (ILT2), is expressed by all lymphoid and myelomonocytic cell types, other receptors display a more selective tissue distribution. Here we characterize an inhibitory receptor, termed ILT4, which is selectively expressed in monocytes, macrophages, and dendritic cells (DCs), binds classical class I molecules and the nonclassical class I molecules HLA-G, and transduces negative signals that can inhibit early signaling events triggered by stimulatory receptors. ILT4 may control inflammatory responses and cytotoxicity mediated by myelomonocytic cells and may modulate their Ag-presenting functions, focusing immune responses to microbial challenges and avoiding autoreactivity.

A case of primary immunodeficiency due to a defect of the major histocompatibility gene complex class I processing and presentation pathway

INTRODUCTION

We report a case of primary immunodeficiency due to a defect of the TAP transporter, an heterodimeric complex which controls the expression of HLA class I molecule by delivering peptides from the cytosol into the lumen of the endoplasmic reticulum. Since childhood, the 36 year old female suffered from recurrent sinusitis/bronchitis. She later developed bronchiectasis and destructive nasal epitheloid granulomata in conjunction with a generalized vasculitic syndrome that did not improve upon immunosuppression and antibiotics.

METHODS

The class I monomorphic W6/32 was used for cell surface staining and immunoprecipitation of MHC class I molecules. Peptide transport assay was carried out in semi-permeabilized cells with iodinated peptides. Antigen presentation experiments were performed using chromium 51 labelled patient B cell line and EBV specific CTL. TAP1 and TAP2 specific antibodies were used for Western blotting and immunoprecipitation of the TAP complex.

RESULTS AND CONCLUSIONS

A severe reduction of MHC class I molecules at the cell surface of the B-cell lines was observed, whereas MHC class II expression was not altered. Isoelectric focusing of metabolically labelled MHC class I molecules revealed that class I heavy chains remain unsialylated, consistent with a block of TAP dependent peptide translocation. These conclusions were confirmed by further experiments showing that peptide translocation was completely abolished. We also demonstrated that presentation of viral antigens through endogenous class I molecules was severely impaired. Immunoprecipitation and Western blotting of TAP1/2 complex showed that TAP2 was not detectable. Further, experiments are in progress to identify the site of the mutation.

Phthalocyanine photodynamic therapy: disparate effects of pharmacologic inhibitors on cutaneous photosensitivity and on tumor regression

The phthalocyanines are promising second-generation photosensitizers that are being evaluated for the photodynamic therapy (PDT) of malignant tumors. In vivo studies with the silicon phthalocyanine Pc 4 have shown that it is highly effective at causing regression of RIF-1 tumors in C3H/HeN mice in PDT protocols. Because cutaneous photosensitivity is the major complication of photosensitizers used for PDT, experiments were performed to evaluate the effect of inhibitors of the inflammatory response (cyproheptadine, dexamethasone, pentoxifylline, and tumor necrosis factor alpha [TNF-alpha] antibodies) on Pc 4-induced cutaneous photosensitivity and tumor regression. The C3H/HeN mice were injected with either Pc 4 or Photofrin and were exposed to 86 J/cm2 of filtered radiation emitted from a solar simulator. Animals were irradiated at 1, 3, 7, 10, 14 and 28 days postinjection. Cutaneous photosensitivity was assessed using the murine ear-swelling response. Cyproheptadine, dexamethasone, pentoxifylline and TNF-alpha antibodies were administered prior to illumination to assess their ability to block Pc 4-induced cutaneous photosensitivity and to evaluate whether such treatment adversely influenced Pc 4 PDT-induced tumor regression. Compared to Photofrin, Pc 4 produced cutaneous photosensitivity that was transient, resolving within 24 h, and that could be elicited for only 10 days after administration. In contrast, Photofrin caused photosensitivity that required 4 days to resolve and could be elicited for at least 1 month after it was administered. The Pc 4-induced cutaneous photosensitivity could be blocked by corticosteroids and an inhibitor of vasoactive amines (cyproheptadine). The TNF-alpha gene transcription was found to increase in keratinocytes following treatment with Pc 4 and light. The anti-TNF-alpha antibodies and pentoxifylline, an inhibitor of cytokine transcription, also prevented cutaneous photosensitivity, implicating TNF-alpha in the pathogenesis of Pc 4-induced cutaneous photosensitivity. None of these agents had any effect on Pc 4 PDT-induced tumor regression. Cyproheptadine, dexamethasone, pentoxifylline and TNF-alpha antibodies may be valuable pharmacologic agents in the management of cutaneous photosensitivity associated with PDT without altering the efficacy of this new therapeutic modality. The findings suggest that it should be possible to devise PDT protocols that block cutaneous photosensitivity without impairing the anti-tumor response to the agents.