T lymphocytes among HIV-infected and -uninfected infants: CD4/CD8 ratio as a potential tool in diagnosis of infection in infants under the age of 2 years

Correlation of High Interleukin 17A and Interleukin 6 Levels with High Virus Load Among Subtype C HIV-infected, Antiretroviral Therapy-naive Zimbabwean Patients: A Cross-sectional Study

Introduction:

In response to the human immunodeficiency virus (HIV) infection, activated immune cells produce several cytokines that alter the immune response and HIV disease progression. We quantified Th1/Th2/Th17 cytokines in an antiretroviral therapy naïve (ART) cohort to investigate their correlation with traditional markers of HIV disease progression; CD4+ T-lymphocytes and virus load (VL).

Methods:

We enrolled 247 HIV-infected ART-naïve participants into the study. CD4+ T- and CD8+ T-lymphocytes were enumerated using flow cytometry. VL was quantified using the Cavidi ExaVirTM Load assay. IL-2, IL-4, IL-6, IL-10, IL-17A, TNF-α, and IFN-γ levels were quantified using the BD Cytometric Bead Array Human Th1/Th2/Th17 cytokine assay. The Kendall’s rank correlation coefficient was used to determine the correlation between log10 transformed data for cytokine levels and CD4+ T- and CD8+ T-lymphocytes, CD4/CD8 ratio, and VL.

Results:

The median CD4+ T- and CD8+ T-lymphocyte counts were 458 cells/µL (IQR:405-556) and 776 cells/µL (IQR:581-1064), respectively. The median CD4/CD8 ratio was 0.6 (IQR: 0.45-0.86). The median VL was log103.3.copies/mL (IQR:2.74-3.93). Low CD4+ T-lymphocyte counts (p=0.010) and CD4/CD8 ratio (p=0.044) were significantly correlated with high VL. There was no significant correlation of cytokine levels with CD4+ T-, CD8+ T-lymphocyte counts and CD4/CD8 ratio. However, high levels of IL-17A (p=0.012) and IL-6 (p=0.034) were significantly correlated with high VL.

Conclusion:

Our study contributes to the little knowledge available on the role of cytokine profiles in the immune response to subtype C HIV infection.

Influence of comorbidities on CD4+/CD8+ proportion in HIV-positive patients in Blumenau, State of Santa Catarina: a retrospective study

INTRODUCTION

The objective was to identify comorbidities related to HIV-positive patients in Blumenau, State of Santa Catarina.

METHODS

A retrospective, descriptive observational design study which analyzed data from 424 patients assisted by the sexually transmitted disease/acquired immunodeficiency syndrome (STD/AIDS) Specialized Care Service (SCS).

RESULTS

Of 424 medical records analyzed, 388 patients presented CD4+/CD8+ ratios lower than 1. The most prevalent comorbidities were smoking, depression, alcoholism, and herpes zoster infection, in males and females.

CONCLUSIONS

The most relevant comorbidity in both genders was herpes zoster, an important marker of immunity in patients. The lowest mean was observed among patients with neurotoxoplasmosis.

Lymphocyte Perturbations in Malawian Children with Severe and Uncomplicated Malaria

Lymphocytes are implicated in immunity and pathogenesis of severe malaria. Since lymphocyte subsets vary with age, assessment of their contribution to different etiologies can be difficult. We immunophenotyped peripheral blood from Malawian children presenting with cerebral malaria, severe malarial anemia, and uncomplicated malaria (n = 113) and healthy aparasitemic children (n = 42) in Blantyre, Malawi, and investigated lymphocyte subset counts, activation, and memory status. Children with cerebral malaria were older than those with severe malarial anemia. We found panlymphopenia in children presenting with cerebral malaria (median lymphocyte count, 2,100/μl) and uncomplicated malaria (3,700/μl), which was corrected in convalescence and was absent in severe malarial anemia (5,950/μl). Median percentages of activated CD69⁺ NK (73%) and γδ T (60%) cells were higher in cerebral malaria than in other malaria types. Median ratios of memory to naive CD4⁺ lymphocytes were higher in cerebral malaria than in uncomplicated malaria and low in severe malarial anemia. The polarized lymphocyte subset profiles of different forms of severe malaria are independent of age. In conclusion, among Malawian children cerebral malaria is characterized by lymphocyte activation and increased memory cells, consistent with immune priming. In contrast, there are reduced memory cells and less activation in severe malaria anemia. Further studies are required to understand whether these immunological profiles indicate predisposition of some children to one or another form of severe malaria.

T-lymphocyte populations following a period of high volume training in female soccer players

PURPOSE

To investigate the T-lymphocyte response to a period of increased training volume in trained females compared to habitual activity in female controls.

METHODS

Thirteen trained female (19.8 ± 1.9 yrs) soccer players were monitored during a two-week long high volume training period (increased by 39%) and thirteen female untrained (20.5 ± 2.2 yrs) controls were monitored during two-weeks of habitual activity. Blood lymphocytes, collected at rest, were isolated before and after the two-week period. Isolated lymphocytes were assessed for the cell surface expression of the co-receptor CD28, a marker of T-lymphocyte naivety, and CD57 a marker used to identify highly-differentiated T-lymphocytes. Co-expression of these markers was identified on helper CD4(+) and cytotoxic CD8(+) T-lymphocytes. In addition a further population of γδ(+) T-lymphocytes were identified. Plasma was used to determine Cytomegalovirus (CMV) serostatus.

RESULTS

No difference was observed in the T-lymphocyte populations following the two-week period of increased volume training. At baseline the number of total CD3(+), cytotoxic CD8(+), naïve (CD8(+) CD28(+) CD57(-)), intermediate (CD8(+) CD28(+) CD57(+)) T-lymphocytes and the number and proportion of γδ(+) T-lymphocytes were greater in the trained compared to the untrained females (p<0.05). The proportion of CD4(+)T-lymphocytes was greater in the untrained compared to the trained (p<0.05), in turn the CD4(+):CD8(+) ratio was also greater in the untrained females (p<0.05). Inclusion of percentage body fat as a covariate removed the main effect of training status in all T-lymphocyte sub-populations, with the exception of the γδ(+) T-lymphocyte population. 8% of the untrained group was defined as positive for CMV whereas 23% of the trained group was positive for CMV. However, CMV was not a significant covariate in the analysis of T-lymphocyte proportions.

CONCLUSION

The period of high volume training had no effect on T-lymphocyte populations in trained females. However, baseline training status differences were evident between groups. This indicates that long-term exercise training, as opposed to short-term changes in exercise volume, appears to elicit discernible changes in the composition of the blood T-lymphocyte pool.

Control lymphocyte subsets: can one country's values serve for another's?

Lymphocyte subsets can be affected by host and environmental factors, yet direct comparisons of their patterns across continents are lacking. This work compares proportions and counts of lymphocyte subsets between healthy children from Thailand, Malawi and the USA. We analyzed subsets of 1,399 healthy children aged between 0 and 15 years: 281 Thai, 397 Malawian and 721American children. Existing data for five subsets were available for all three cohorts (Total T, CD4+ T, CD8+ T, natural killer (NK) and B cells), with data for another six subsets from the Thai and American cohorts (naïve, memory and activated CD4+ and CD8+ T cells). Cellular patterns between cohorts differed mainly in children under two years. Compared to American children, Thai children had higher median numbers of total T cells, CD8+ T cells and NK cells while Malawian children under 18 months, on average, had more CD8+ T cells and B cells. Both Thai and Malawian children had lower median CD4+ T cell percentages and CD4/CD8 ratios than American children. Thai children had more memory and activated CD8+ T cells than American children. Approximately one-fifth of Thai and Malawian HIV-uninfected healthy children aged 0-3 years met WHO-defined CD4+ count criteria for immune-deficiency in HIV-infected children. Healthy children from Thailand, Malawi and the USA have differences in lymphocyte subsets that are likely to be due to differences in ethnicity, exposure to infectious diseases and environmental factors. These results indicate the need for country-specific reference ranges for diagnosis and management of immunologic disorders.

HIV infection and microbial diversity in saliva

Limited information is available about the effects of HIV and subsequent antiretroviral treatment on host-microbe interactions. This study aimed to determine the salivary microbial composition for 10 HIV-seropositive subjects, before and 6 months after highly active antiretroviral therapy (HAART), compared with that for 10 HIV-seronegative subjects. A conventional culture and two culture-independent analyses were used and consistently demonstrated differences in microbial composition among the three sets of samples. HIV-positive subjects had higher levels of total cultivable microbes, including oral streptococci, lactobacilli, Streptococcus mutans, and Candida, in saliva than did HIV-negative subjects. The total cultivable microbial levels were significantly correlated with CD4+ T cell counts. Denaturing gradient gel electrophoresis (DGGE), which compared the overall microbial profiles, showed distinct fingerprinting profiles for each group. The human oral microbe identification microarray (HOMIM) assay, which compared the 16S rRNA genes, showed clear separation among the three sample groups. Veillonella, Synergistetes, and Streptococcus were present in all 30 saliva samples. Only minor changes or no changes in the prevalence of Neisseria, Haemophilus, Gemella, Leptotrichia, Solobacterium, Parvimonas, and Rothia were observed. Seven genera, Capnocytophaga, Slackia, Porphyromonas, Kingella, Peptostreptococcaceae, Lactobacillus, and Atopobium, were detected only in HIV-negative samples. The prevalences of Fusobacterium, Campylobacter, Prevotella, Capnocytophaga, Selenomonas, Actinomyces, Granulicatella, and Atopobium were increased after HAART. In contrast, the prevalence of Aggregatibacter was significantly decreased after HAART. The findings of this study suggest that HIV infection and HAART can have significant effects on salivary microbial colonization and composition.

Presumptive diagnosis of severe HIV infection to determine the need for antiretroviral therapy in children less than 18 months of age

OBJECTIVE

To develop a new algorithm for the presumptive diagnosis of severe disease associated with human immunodeficiency virus (HIV) infection in children less than 18 months of age for the purpose of identifying children who require antiretroviral therapy (ART).

METHODS

A conditional probability model was constructed and non-virologic parameters in various combinations were tested in a hypothetical cohort of 1000 children aged 6 weeks, 6 months and 12 months to assess the sensitivity, specificity, and positive and negative predictive values of these algorithms for identifying children in need of ART. The modelled parameters consisted of clinical criteria, rapid HIV antibody testing and CD4+ T-lymphocyte (CD4) count.

FINDINGS

In children younger than 18 months, the best-performing screening algorithm, consisting of clinical symptoms plus antibody testing plus CD4 count, showed a sensitivity ranging from 71% to 80% and a specificity ranging from 92% to 99%. Positive and negative predictive values were between 61% and 97% and between 95% and 96%, respectively. In the absence of virologic tests, this alternate algorithm for the presumptive diagnosis of severe HIV disease makes it possible to correctly initiate ART in 91% to 98% of HIV-positive children who are at highest risk of dying.

CONCLUSION

The algorithms presented in this paper have better sensitivity and specificity than clinical parameters, with or without rapid HIV testing, for the presumptive diagnosis of severe disease in HIV-positive children less than 18 months of age. If implemented, they can increase the number of HIV-positive children successfully initiated on ART.

Reference values of lymphocyte subsets in healthy, HIV-negative children in Cameroon

Lymphocyte subset reference values used to monitor infectious diseases, including HIV/AIDS, tuberculosis, malaria, or other immunological disorders in healthy children in Cameroon, are lacking. Values for Caucasian cohorts are already being utilized for clinical decisions but could be inappropriate for African populations. We report here the immunological profile for children aged from birth through 6 years in Cameroon and also compare our values to data from other African and Caucasian populations. In a cohort of 352 healthy children, aged 0 to 6 years, the relative and absolute numbers of T-cell subsets, B cells, and NK lymphocytes were determined from peripheral blood collected in EDTA tubes. Samples were stained with BD Multitest reagents in Trucount tubes and analyzed by using CellQuest-Pro and FlowJo software. We evaluated about 23 different lymphocyte subsets in which the absolute number and percentage values differed significantly (P < 0.05) with age and peaked between 6 and 12 months. B-cell values were higher compared to reported values from developed countries. Differences in activated and differentiated T cells were observed in subjects between 1 and 6 years of age. The absolute CD8(+) T-cell count and the CD4(+)/CD8(+) ratio seem to depend on gender. Normal lymphocyte subsets values among children from Cameroon differ from reported values in Caucasian and some African populations. The differences observed could be due to genetic and environmental factors coupled with the methodology used. These values could be used as initial national reference guidelines as more data are assembled.

Detection limits of intraoperative near infrared imaging for tumor resection

BACKGROUND AND OBJECTIVES

The application of fluorescent molecular imaging to surgical oncology is a developing field with the potential to reduce morbidity and mortality. However, the detection thresholds and other requirements for successful intervention remain poorly understood. Here we modeled and experimentally validated depth and size of detection of tumor deposits, trade-offs in coverage and resolution of areas of interest, and required pharmacokinetics of probes based on differing levels of tumor target presentation.

METHODS

Three orthotopic tumor models were imaged by widefield epifluorescence and confocal microscopes, and the experimental results were compared with pharmacokinetic models and light scattering simulations to determine detection thresholds.

RESULTS

Widefield epifluorescence imaging can provide sufficient contrast to visualize tumor margins and detect tumor deposits 3-5  mm deep based on labeled monoclonal antibodies at low objective magnification. At higher magnification, surface tumor deposits at cellular resolution are detectable at TBR ratios achieved with highly expressed antigens.

CONCLUSIONS

A widefield illumination system with the capability for macroscopic surveying and microscopic imaging provides the greatest utility for varying surgical goals. These results have implications for system and agent designs, which ultimately should aid complete resection in most surgical beds and provide real-time feedback to obtain clean margins.

T-lymphocyte subsets in apparently healthy nigerian children

Population studies showed that there are differences in T-lymphocytes subpopulation of normal children in different regions, and reference values in an area might be different from another. This study compared the values in our population with CDC and WHO reference values. Blood samples from 279 healthy, HIV-negative children <12 years of age were analysed for complete blood count, CD3+, CD4+, CD8+ counts and percentages. Except for CD8%, mean values for all parameters measured significantly decreased with age. CD4+ counts were higher in females than males, P < .05. Using the WHO criteria, 15.9% of subjects had low total lymphocyte count and 20.6% had low CD4 count. Children <3 years had median CD4% lower than WHO normal values. Our median CD4+ counts correlated with CDC values. Values used by WHO in infants are higher than ours. We suggest that our children be assessed using CDC reference values which correlate with ours.

Performance of modified WHO presumptive criteria for diagnosis of HIV infection in children <18 months admitted to University Teaching Hospital in Lusaka

BACKGROUND: Making a diagnosis of HIV infection in children aged less than 18 months remains a challenge in low resource settings like Zambia due to the limited availability of gold standard testing with HIV DNA PCR. Clinicians in rural areas have to depend on clinical diagnosis to start HAART as they wait for the dry blood spot (DBS) for DNA PCR results sent from the urban centers. METHODS: This descriptive cross-sectional study was performed at the University Teaching Hospital, Lusaka, Zambia. 299 HIV-exposed children aged less than 18 months were enrolled following a consent procedure. Patients were evaluated for HIV infection based on the World Health Organization's presumptive diagnostic criteria (WHO-PDC), integrated management of childhood illnesses (IMCI) criteria, select physical exam abnormalities, and CD4% and findings were compared with HIV-DNA PCR results. RESULTS: Of the 299 exposed patients analyzed, 111(37%) were found to be HIV-positive by DNA PCR. The median CD4% in the infected children was 18%. WHO-PDC used on its own had 23% sensitivity (95% CI 17-32%) and 93% specificity (88-96%), respectively, whereas IMCI criterion had 10% sensitivity (6-17%) and 97% specificity (94-99%), respectively. Multivariate analysis was used to identify the most sensitive predictors when combined with the WHO-PDC and IMCI criterion. WHO-PDC with CD4% improved the sensitivity to 77% (68-83%) with a specificity of 83% (77-88%), positive predictive value (PPV) of 73% (64-80%) and negative predictive value (NPV) of 86% (80-90%). IMCI with CD4% improved sensitivity to 80% (71-87%) with a specificity of 88% (82-92%), PPV 78% (69-85%) and NPV 89% (84-93%). The addition of individual physical exam findings without CD4% improved the sensitivity of WHO-PDC only modestly. When the WHO-PDC, weight<3(rd) percentile, hepatomegaly, splenomegaly, lymphadenopathy and CD4% were combined, the sensitivity improved to 85% (77-90%), specificity 63% (56-70%), PPV 58% (50-65%) and NPV of 88% (81-92%). CONCLUSION: The WHO-PDC clinical algorithm can be improved when combined with a CD4% <25% in children less than 12 months of age and CD4% <20% in those between 12 and 18 months.

Research needs and challenges in the development of HIV diagnostic and treatment monitoring tests for use in resource-limited settings

PURPOSE OF REVIEW

The aim of this article is to review research priorities for current and new technologies to diagnose HIV and to monitor treatment response, including technologies to enumerate CD4 cell counts and quantify plasma viral load, in resource-limited settings.

RECENT FINDINGS

Numerous challenges remain before HIV diagnostic and treatment monitoring technologies can be broadly implemented, especially in rural areas. New technologies that are less costly and complex to use are in development and may be better suited than current technologies for use in resource-limited settings. Investment into research activities is needed for development, evaluation and validation of new technologies. The lack of clarity in the process for evaluation and validation for these technologies affects country and program-level decisions on the appropriateness of technologies for individual settings. Implementation research is needed to assess how best to use CD4 and viral load to guide initiation and management of antiretroviral treatment, as well as how best to scale up diagnosis of HIV serostatus in infants. Studies also need to be conducted to determine if the same CD4 cutoffs can be used in resource-limited settings for initiating antiretroviral therapy and prophylaxis against opportunistic infections due to potential regional differences and the impact of other common co-morbidities on CD4 cell counts.

SUMMARY

Increased availability of antiretroviral therapy in resource-limited settings increases the need for reliable, less costly and simpler to use HIV diagnostic and treatment monitoring technologies. Global leadership is needed to coordinate the research and development necessary to ensure that HIV diagnostic and treatment monitoring technologies are properly evaluated in the setting where they will be used.

Lymphocyte subsets in healthy Malawians: implications for immunologic assessment of HIV infection in Africa

Background

CD4⁺T lymphocyte measurements are the most important indicator of mortality in HIV-infected individuals in resource-limited settings. There is currently a lack of comprehensive immunophenotyping data from African populations to guide the immunologic assessment of HIV infection.

Objective

To quantify variation in absolute and relative lymphocyte subsets with age in healthy Malawians.

Methods

Lymphocyte subsets in peripheral blood of 539 healthy HIV-uninfected Malawians stratified by age were enumerated by flow cytometry.

Results

B and T–lymphocyte and T-lymphocyte subset absolute concentrations peaked in early childhood then decreased to adult levels, whereas lymphocyte subset proportions demonstrated much less variation with age. Adult lymphocyte subsets were similar to those in developed countries. In contrast, high B-lymphocyte and CD8⁺T-lymphocyte levels among children under 2 years, relative to those in developed countries, resulted in low CD4⁺T-lymphocyte percentages that varied little between 0 and 5 years (35% to 39%). The CD4⁺T-lymphocyte percentages in 35% of healthy children under 1 year and 18% of children age 1 to 3 years were below the World Health Organization threshold defining immunodeficiency in HIV-infected children in resource-limited settings. Thirteen percent of healthy children under 18 months old had a CD4:CD8T-lymphocyte ratio <1.0, which is commonly associated with HIV infection. All immunologic parameters except absolute natural killer lymphocyte concentration varied significantly with age, and percentage and overall absolute CD4⁺T-lymphocyte counts were higher in females than males.

Conclusion

Although lymphocyte subsets in Malawian adults are similar to those from developed countries, CD4⁺T-lymphocyte percentages in young children are comparatively low. These findings need to be considered when assessing the severity of HIV-related immunodeficiency in African children under 3 years.

Performance of clinical algorithms for HIV-1 diagnosis and antiretroviral initiation among HIV-1-exposed children aged less than 18 months in Kenya

BACKGROUND

Ninety percent of HIV-1-infected children live in sub-Saharan Africa. In the absence of diagnosis and antiretroviral therapy, approximately 50% die before 2 years.

METHODS

We evaluated sensitivity and specificity of clinical algorithms for diagnosis of HIV-1 infection and antiretroviral therapy initiation among HIV-1-exposed children aged less than 18 months. Children were identified with routine HIV-1 testing and assessed using 3 sets of criteria: (1) Integrated Management of Childhood Illnesses (IMCI), (2) World Health Organization Presumptive Diagnosis (WHO-PD) for HIV-1 infection, and (3) CD4 T-lymphocyte cell subsets. HIV-1 infection status was determined using DNA polymerase chain reaction testing.

FINDINGS

A total of 1418 children (median age 5.4 months) were screened for HIV-1 antibodies, of whom 144 (10.2%) were seropositive. Of these, 134 (93%) underwent HIV-1 DNA testing and 80 (60%) were found to be HIV-1 infected. Compared with HIV-1 DNA testing, sensitivity and specificity of the IMCI criteria were 19% and 96% and for WHO-PD criteria 43% and 88%, respectively. Inclusion of severe immune deficiency determined by CD4% improved sensitivity of IMCI and WHO-PD criteria to 74% and 84%, respectively; however, specificity declined to 43% and 41%, respectively.

INTERPRETATION

Diagnosis of HIV-1 infection among exposed children less than 18 months in a high-prevalence resource-limited setting remains a challenge, and current recommended algorithms have low sensitivity. This underscores the need for rapid scale-up of viral assays for early infant diagnosis.

Making a working clinical diagnosis of HIV infection in infants in Zimbabwe

OBJECTIVES

Clinical algorithms can be helpful in decisions about treatment and feeding options in infancy, but have had limited exposure to real data. This analysis uses data from a large clinical trial to test such algorithms, and thereby develop a successor which performs usefully in poor countries with high HIV-prevalence.

METHODS

The ZVITAMBO trial followed 14 110 mother-baby pairs through infancy. 32% of mothers were HIV-positive. Infants were HIV tested regularly using DNA PCR. Clinical signs were evaluated in terms of identifying HIV-infection at 6 weeks, 6 and 12 months, using Zimbabwean, South African, and WHO generic adaptations of the WHO integrated management of childhood illness HIV algorithm. A modification, in which HIV-exposed infants are first divided into being at least or less than median weight-for-age, was derived and evaluated.

RESULTS

At 6 weeks 65% of all infected babies are less than median weight-for-age. Adding at least two clinical signs reduces sensitivity to 20% but those identified are 1.5 (95% CI 1.1-2.1) times more likely to die by 6 months than other infected infants. At 6 months, 86% of uninfected babies of HIV-infected mothers can be identified by selecting those whose weight is greater than median or, if less than median, who exhibit <2 clinical signs.

CONCLUSIONS

In poor settings a simple clinical algorithm can identify children with probable HIV infection, especially those at risk of early death, who can then be referred for further testing and care, including highly active antiretroviral therapy. Most infants who are HIV-uninfected can be identified at 6 months and provided with support to maintain infection-free survival, including focussed infant-feeding counselling.

CD4+/CD8+ T cell ratio for diagnosis of HIV-1 infection in infants: Women and Infants Transmission Study

OBJECTIVE

In this study, we tested the hypothesis that the CD4(+)/CD8(+) T cell ratio could predict HIV infection status in HIV-exposed infants.

METHODS

CD4(+)/CD8(+) T cell ratios were determined from data for live-born singleton infants who had been prospectively enrolled in the Women and Infants Transmission Study. Data for 2208 infants with known HIV infection status (179 HIV-infected and 2029 uninfected infants) were analyzed.

RESULTS

Receiver operating characteristic curves indicated that the CD4(+)/CD8(+) T cell ratio performed better than the proportion of CD4(+) T cells for diagnosis of HIV infection as early as 2 months of age, and this relationship was unaffected by adjustment for maternal race/ethnicity, infant birth weight, gestational age, and gender. At 4 months of age, 90% specificity for HIV diagnosis was associated with 60% sensitivity. For ease of use, graphical estimates based on cubic splines for the time-dependent parameters in a Box-Cox transformation (L), the median (M), and the coefficient of variation (S) were used to create LMS centile curves to show the sensitivity and specificity of CD4(+)/CD8(+) T cell ratios in HIV-infected and uninfected infants until 12 months of age. At 6 months of age, a simplified equation that incorporated sequential CD4(+)/CD8(+) T cell ratios and hematocrit values resulted in improved receiver operating characteristic curves, with 94% positive predictive value and 98% negative predictive value. The positive and negative predictive values remained above 90% in simulated infant populations over a wide range of HIV infection prevalence values.

CONCLUSIONS

In the absence of virological diagnosis, a presumptive diagnosis of HIV infection status can be made on the basis of CD4(+)/CD8(+) T cell ratios in HIV-1-exposed infants after 2 months of age; sensitivity and specificity can be improved at 6 months by using a discriminant analysis equation.

CD4+ T lymphocytes enumeration by an easy-to-use single platform image cytometer for HIV monitoring in resource-constrained settings

BACKGROUND

HIV monitoring in resource-constrained settings demands affordable and reliable CD4(+) T lymphocytes enumeration methods. We developed a simple single platform image cytometer (SP ICM), which is a dedicated volumetric CD4(+) T lymphocytes enumeration system that uses immunomagnetic and immunofluorescent technologies. The instrument was designed to be a low-cost, yet reliable and robust one. In this article we test the instrument and the immunochemical procedures used on blood from HIV negative and HIV positive patients.

METHODS

After CD4 immunomagnetic labeling in whole blood, CD4(+) T lymphocytes, CD4(+dim) monocytes and some nonspecifically labeled cells are magnetically attracted to an analysis surface. Combining with CD3-Phycoerythrin (PE) labeling, only CD3(+)CD4(+) T lymphocytes are fluorescently labeled and visible in a fluorescent image of the analysis surface. The number of CD4(+) T lymphocytes is obtained by image analysis. Alternatively, CD3 immunomagnetic selection in combination with CD4 immunofluorescent labeling can also be applied for CD4(+) T lymphocytes enumeration.

RESULTS

The SP ICM system was compared with two single platform flow cytometer (SP FCM) methods: tetraCXP and TruCount methods. The SP ICM system has excellent precision, accuracy and linearity for CD4(+) T lymphocytes enumeration. Good correlations were obtained between the SP ICM and the SP FCM methods for blood specimens of 44 HIV(-) patients, and of 63 HIV(+) patients. Bland-Altman plots showed interchangeability between the SP ICM and the SP FCM methods.

CONCLUSIONS

The immunolabeling methods and the instrumentation are simple and easy-to-handle for less-trained operators. The SP ICM system is a good candidate for CD4(+) T lymphocytes enumeration in point-of-care settings of resource-constrained countries.

CD4/CD8 T-cell ratio predicts HIV infection in infants: the National Heart, Lung, and Blood Institute P2C2 Study

BACKGROUND

In resource-poor regions of the world, HIV virologic testing is not available.

OBJECTIVE

We sought to evaluate the diagnostic usefulness of the CD4/CD8 T-cell ratio in predicting HIV infection in infants.

METHODS

Data from the 3- and 9-month visits for non-breast-fed infants born to HIV-infected mothers enrolled (1990-1994) in the Pediatric Pulmonary and Cardiac Complications of Vertically Transmitted HIV Infection Study (mother-to-child transmission of HIV, 17%) were analyzed. Data from the 3-month visit for infants enrolled (1985-1996) in the Perinatal AIDS Collaborative Transmission Study (mother-to-child transmission of HIV, 18%) were used for validation.

RESULTS

At 3 months of age, data were available on 79 HIV-infected and 409 uninfected non-breast-fed infants in the Pediatric Pulmonary and Cardiac Complications of Vertically Transmitted HIV Infection Study. The area under the curve (AUC) of the receiver operating characteristic curve at 3 months was higher for the CD4/CD8 ratio compared with the CD4(+) T-cell count (AUC, 0.83 and 0.75; P = .03). The mean CD4/CD8 ratio at the 3-month visit was 1.7 for HIV-infected infants and 3.0 for uninfected infants. A CD4/CD8 ratio of 2.4 at 3 months of age was almost 2.5 times more likely to occur in an HIV-infected infant compared with an uninfected infant (test sensitivity, 81%; posttest probability of HIV, 33%). Model performance in the Centers for Disease Control and Prevention Perinatal AIDS Collaborative Transmission Study validation test (224 HIV-infected and 1015 uninfected 3-month-old infants) was equally good (AUC, 0.78 for CD4/CD8 ratio).

CONCLUSION

The CD4/CD8 T-cell ratio is a more sensitive predictor of HIV infection in infants than the CD4(+) T-cell count.

CLINICAL IMPLICATIONS

The CD4/CD8 T-cell ratio can be used with caution to predict HIV infection in children.

A single platform image cytometer for resource-poor settings to monitor disease progression in HIV infection

BACKGROUND

For resource-poor countries, affordable methods are required for enumeration of CD4(+) T lymphocytes of HIV-positive patients. For infants, additional determination of CD4/CD8 ratio is needed.

METHODS

We determine the CD4(+) and CD8(+) T lymphocytes as the CD3(+)CD4(+) and CD3(+)CD8(+) population of blood cells. Target cells are CD3-immunomagnetically separated from the whole blood, and CD4-Phycoerythrin and CD8-PerCP immunofluorescently labeled. A point-of-care single platform image cytometer was developed to enumerate the target CD3(+)CD4(+) and CD3(+)CD8(+) populations. It has light-emitting diodes illumination, is fully computer-controlled, operates from a 12 V battery, and was designed to be cheap and easy-to-handle. Target cells are imaged on a CCD camera and enumerated by an image analysis algorithm. The cytometer outputs the absolute number of CD4(+) and CD8(+) T lymphocytes/microl and CD4/CD8 ratio.

RESULTS

The quality of the cell images obtained with the cytometer is sufficient for a reliable enumeration of target cells. The image cytometer achieves an accuracy of better than 10% in the range of 50-1700 cells/microl. Analysis of blood samples from HIV patients yields a good agreement with the TruCount method for CD4 and CD8 count and CD4/CD8 ratio.

CONCLUSIONS

The image cytometer is affordable (component costs $3,000), compact (25 x 25 x 20 cm(3)), and uses disposable test materials, making it a good candidate to monitor progression of immunodeficiency disease in resource-poor settings.

Diagnosis of pediatric human immunodeficiency virus infection in resource-constrained settings

The majority of children infected with human immunodeficiency virus live in resource-constrained settings and die without an established diagnosis. Definitive laboratory diagnosis in children younger than 12-18 months requires virologic testing; however, antibody testing is often the only option available. Antibody testing provides a definitive diagnosis in older children but is frequently not used. Children meeting clinical criteria should be treated regardless of availability of laboratory diagnoses.