Understanding causes of hospitalization and access to care among newly diagnosed HIV patients in Houston, TX

More than a quarter of patients with HIV in the United States are diagnosed in hospital settings most often with advanced HIV related conditions.(1) There has been little research done on the causes of hospitalization when the patients are first diagnosed with HIV. The aim of this study was to determine if the patients are hospitalized due to an HIV related cause or due to some other co-morbidity. Reduced access to care could be one possible reason why patients are diagnosed late in the course of the disease. This study compared the access to care of patients diagnosed with HIV in hospital and outpatient setting. The data used for the study was a part of the ongoing study “Attitudes and Beliefs and Steps of HIV Care”. The participants in the study were newly diagnosed with HIV and recruited from both inpatient and outpatient settings. The primary and the secondary diagnoses from hospital discharge reports were extracted and a primary reason for hospitalization was ascertained. These were classified as HIV-related, other infectious causes, non–infectious causes, other systemic causes, and miscellaneous causes. Access to care was determined by a score based on responses to a set of questions derived from the HIV Cost and Services Utilization Study (HCSUS) on a 6 point scale. The mean score of the hospitalized patients and mean score of the patients diagnosed in an outpatient setting was compared. We used multiple linear regressions to compare mean differences in the two groups after adjusting for age, sex, race, household income educational level and health insurance at the time of diagnosis. There were 185 participants in the study, including 78 who were diagnosed in hospital settings and 107 who were diagnosed in outpatient settings. We found that HIV-related conditions were the leading cause of hospitalization, accounting for 60% of admissions, followed by non-infectious causes (20%) and then other infectious causes (17%). The inpatient diagnosed group did not have greater perceived access-to-care as compared to the outpatient group. Regression analysis demonstrated a statistically significant improvement in access-to-care with advancing education level (p=0.04) and with better health insurance (p=0.004). HIV-related causes account for many hospitalizations when patients are first diagnosed with HIV. Many of these HIV-related hospitalizations could have been prevented if patients were diagnosed early and linked to medical care. Programs to increase HIV awareness need to be an integral part of activities aimed at control of spread of HIV in the community. Routine testing for HIV infection to promote early HIV diagnosis can prevent significant morbidity and mortality.^

Influence of trust on HIV diagnosis and care practices

Many factors have been studied as potential correlates in delayed HIV diagnosis and delayed linkage to HIV healthcare. Few studies have analyzed the association of trust as a correlate in HIV diagnosis and HIV medical treatment delays. This study sought to assess the effect of patient trust in physicians and trust in the healthcare system, and whether diminished levels of trust affect delays in HIV diagnosis and/or linking to HIV healthcare, among a cohort of newly diagnosed HIV-infected persons, in Harris County, Texas.^ This study is a secondary data analysis from the Attitude and Beliefs and the Steps of HIV Care Study, also known as the Steps Study, a prospective observational cohort study. From January 2006 to October 2007 patients newly diagnosed with HIV infection and not yet in HIV primary care were recruited from publically funded HIV testing sites in Houston, Texas.^ Two outcomes were assessed in this study. The first outcome sought to determine the influence of trust and whether decreased levels of trust predicted delays in HIV diagnosis. Trust in physicians and trust in the healthcare system were measured via 2 validated trust scales. Trust scores of those with late diagnosis (CD4 counts <200 cells/mm3) were compared statistically with those with early diagnosis (CD4 counts ≥ 200 cells/mm3) in a cross sectional study design. Trust was not found to be predictive of delays in HIV diagnosis. ^ The second outcome utilized the same trust scales and a prospective cohort study design to assess whether there were differences in trust scores between those who successfully linked to HIV healthcare, compared to those who failed to link to HIV healthcare, within 6 months of diagnosis. Patients with higher trust in physicians and trust in the healthcare system were significantly more likely to be linked to HIV healthcare than those with lower trust.^ Overall, this study showed that among low-income persons with undiagnosed HIV infection, low trust is not a barrier to timely diagnosis of HIV infection. Trust may be a factor in promoting a prompt linkage to HIV healthcare among those who are newly diagnosed.^

Psychosocial predictors of HIV testing behaviors among high risk heterosexuals

Though a lot of progress has been made in the treatment, prevention, and in increasing the knowledge and awareness of HIV/AIDS, the CDC reports that over 21% of the people infected with HIV are unaware of their HIV serostatus. Thirty-one percent of people infected with HIV are diagnosed late in the disease progression, often too late to prevent the transmission or the progression of HIV to AIDS. CDC has set a goal to increase by the year 2010, the number of people aware of the HIV serostatus by 5%. ^ This study examined the association between decision-making and risk-taking (assessed using the decision-making confidence and risk-taking scales of the Texas Christian University Self Rating Form) and HIV testing behaviors within a population of heterosexuals at risk for HIV infections living in Harris County, Texas (N=923). Data used in the study was obtained during the first cycle of the National HIV Behavioral Surveillance among heterosexuals at risk for HIV infection (NHBS-HET1), conducted from October, 2006 to June, 2007. Eighty percent of the study population reported testing for HIV at some point in their lives. The results showed that individuals who scored high (>3.3) on the decision-making confidence scale of the TCU/SRF were more likely to be tested for HIV when compared to those who scored low on the scale (OR= 2.02, 95% CI= 1.44–2.84), and that individuals who score low on the risk-taking scale of the TCU/SRF were more likely to have been tested for HIV when compared to those who scored high on the scale (OR= 1.65, 95% CI= 1.2–2.31). Several demographic factors were also assessed for their association with HIV testing behaviors. Only sex was found to be associated with HIV testing. ^ The findings suggest that risk-taking and decision-making are predictors of HIV testing behaviors such as prior HIV testing within heterosexuals living in high-risk areas of Houston, Texas, and that intervention designed to improve the risk-taking and decision-making attributes of this population might improve HIV testing within this population.^

A systematic review of literature to compare the fertility desires among HIV positive women and cancer survivors

Background. Decision-making on reproductive issues is influenced by an interplay of individual, familial, medical, religious and socio-cultural factors. Women with chronic medical illnesses such an HIV infection and cancers are often fraught with decisional conflicts about child-bearing. With increase in the incidence of these illnesses as well as improvement in survival rates, there is a need to pay due attention to the issue of reproductive decision-making. Examining the prevalence and determinants of fertility desires in the two groups in a comparative manner would help bring to light perception of the medical community and the society in general on the two illnesses and the issue of motherhood. ^ Methods. Systematic literature search was undertaken using databases such as MEDLINE (PubMED), MEDLINE (Ovid), PsycInfo and Web of Science. Articles published in English and English language abstracts for foreign articles were included. Studies that explore ‘fertility desires’ as the outcome variable were included. Quantitative studies which have assessed the prevalence of fertility desires as well as qualitative studies which have provided a descriptive understanding of factors governing reproductive desires were included in the review. ^ Results. A total of 34 articles (29 studies examining HIV and 5 studies examining cancer in relation to fertility desires). Variables such as age, stage of illness, support of spouse and family, perception of the medical community and one’s own view of motherhood were key determinants among both groups. ^ Conclusion. There is a need for uniform, systematic research in this field. It is important that health care workers acknowledge these decisional conflicts, include them as part of the medical care of these patients and provide guidance with the right balance of information, practicality and compassion.^

Concomitant Mycobacterium tuberculosis infection and type 2 diabetes: A descriptive model with global health implications

The type 2 diabetes (diabetes) pandemic is recognized as a threat to tuberculosis (TB) control worldwide. This secondary data analysis project estimated the contribution of diabetes to TB in a binational community on the Texas-Mexico border where both diseases occur. Newly-diagnosed TB patients > 20 years of age were prospectively enrolled at Texas-Mexico border clinics between January 2006 and November 2008. Upon enrollment, information regarding social, demographic, and medical risks for TB was collected at interview, including self-reported diabetes. In addition, self-reported diabetes was supported by blood-confirmation according to guidelines published by the American Diabetes Association (ADA). For this project, data was compared to existing statistics for TB incidence and diabetes prevalence from the corresponding general populations of each study site to estimate the relative and attributable risks of diabetes to TB. In concordance with historical sociodemographic data provided for TB patients with self-reported diabetes, our TB patients with diabetes also lacked the risk factors traditionally associated with TB (alcohol abuse, drug abuse, history of incarceration, and HIV infection); instead, the majority of our TB patients with diabetes were characterized by overweight/obesity, chronic hyperglycemia, and older median age. In addition, diabetes prevalence among our TB patients was significantly higher than in the corresponding general populations. Findings of this study will help accurately characterize TB patients with diabetes, thus aiding in the timely recognition and diagnosis of TB in a population not traditionally viewed as at-risk. We provide epidemiological and biological evidence that diabetes continues to be an increasingly important risk factor for TB.^

Cross-culture perspectives on fear of HIV disease and AIDS in health care workers

Health care workers have been known to carry into the workplace a variety of judgmental and negative attitudes towards their patients. In no other area of patient care has this issue been more pronounced as in the management of patients with AIDS. Health care workers have refused to treat or manage patients with AIDS and have often treated them more harshly than identically described leukemia patients. Some health care institutions have simply refused to admit patients with AIDS and even recent applicants to medical colleges and schools of nursing have indicated a preference for schools in areas with low prevalence of HIV disease. Since the attitudes of health care workers do have significant consequences on patient management, this study was carried out to determine the differences in clinical practice in Nigeria and the United States of America as it relates to knowledge of a patient's HIV status, determine HIV prevalence and culture in each of the study sites and how they impact on infection control practices, determine the relationship between infection control practices and fear of AIDS, and also determine the predictors of safe infection control practices in each of the study sites.^ The study utilized the 38-item fear of AIDS scale and the measure of infection control questionnaire for its data. Questionnaires were administered to health care workers at the university teaching hospital sites of Houston, Texas and Calabar in Nigeria. Data was analyzed using a chi-square test, and where appropriate, a student t-tests to establish the demographic variables for each country. Factor analysis was done using principal components analysis followed by varimax rotation to simple structure. The subscale scores for each study site were compared using t-tests (separate variance estimates) and utilizing Bonferroni adjustments for number of tests. Finally, correlations were carried out between infection control procedures and fear of AIDS in each study site using Pearson-product moment correlation coefficients.^ The study revealed that there were five dimensions of the fear of AIDS in health care workers, namely fear of loss of control, fear of sex, fear of HIV infection through blood and illness, fear of death and medical interventions and fear of contact with out-groups. Fear of loss of control was the primary area of concern in the Nigerian health care workers whereas fear of HIV infection through blood and illness was the most important area of AIDS related feats in United States health care workers. The study also revealed that infection control precautions and practices in Nigeria were based more on normative and social pressures whereas it was based on knowledge of disease transmission, supervision and employee discipline in the United States, and thus stresses the need for focused educational programs in health care settings that emphasize universal precautions at all times and that are sensitive to the cultural nuances of that particular environment. ^

The association between CD4+ lymphocyte count and measures of body composition in HIV-infected men

Purpose. This project was designed to describe the association between wasting and CD4 cell counts in HIV-infected men in order to better understand the role of wasting in progression of HIV infection.^ Methods. Baseline and prevalence data were collected from a cross-sectional survey of 278 HIV-infected men seen at the Houston Veterans Affairs Medical Center Special Medicine Clinic, from June 1, 1991 to January 1, 1994. A follow-up study was conducted among those at risk, to investigate the incidence of wasting and the association between wasting and low CD4 cell counts. Wasting was described by four methods. Z-scores for age-, sex-, and height-adjusted weight; sex-, and age-adjusted mid-arm muscle circumference (MAMC); and fat-free mass; and the ratio of extra-cellular mass (ECM) to body-cell mass (BCM) $>$ 1.20. FFM, ECM, and BCM were estimated from bioelectrical impedance analysis. MAMC was calculated from triceps skinfold and mid-arm circumference. The relationship between wasting and covariates was examined with logistic regression in the cross-sectional study, and with Poisson regression in the follow-up study. The association between death and wasting was examined with Cox's regression.^ Results. The prevalence of wasting ranged from 5% (weight and ECM:BCM) to almost 14% (MAMC and FFM) among the 278 men examined. The odds of wasting, associated with baseline CD4 cell count $<$200, was significant for each method but weight, and ranged from 4.6 to 12.7. Use of antiviral therapy was significantly protective of MAMC, FFM and ECM:BCM (OR $\approx$ 0.2), whereas the need for antibacterial therapy was a risk (OR 3.1, 95% CI 1.1-8.7). The average incidence of wasting ranged from 4 to 16 per 100 person-years among the approximately 145 men followed for 160 person-years. Low CD4 cell count seemed to increase the risk of wasting, but statistical significance was not reached. The effect of the small sample size on the power to detect a significant association should be considered. Wasting, by MAMC and FFM, was significantly associated with death, after adjusting for baseline serum albumin concentration and CD4 cell count.^ Conclusions. Wasting by MAMC and FFM were strongly associated with baseline CD4 cell counts in both the prevalence and incidence study and strong predictors of death. Of the two methods, MAMC is convenient, has available reference population data, may be the most appropriate for assessing the nutritional status of HIV-infected men. ^

A descriptive study of syphilis infection in Houston, Texas, 1999--2008

The rate of syphilis nationally has been on the rise since 2001. Syphilis, if left untreated can facilitate the transmission of HIV infection. An epidemiologic study describing the trends of syphilis is important to the public health community to lay the foundation for the development and implementation of programs to prevent and eliminate syphilis in the United States. ^ The objective of this study was to describe the trends of syphilis among the population in Houston/Harris County, Texas. ^ We reviewed surveillance data that included 11,605 unique cases from the Houston Department of Human and Health Service from 1999 through 2008. The rates were calculated per 100,000 population. ^ We show the prevalence of syphilis at testing (excluding congenital) increased 40% in Houston/Harris County, Texas from 2001 through 2008, and the ratio of syphilis comparing men to women was 2:1. The 18–29 years age group had the highest percentage of cases of syphilis among all age groups in Houston/Harris County. Primary and Secondary (P&S) syphilis, the most infectious stage, had an 85% increase in rate among males from 1999 through 2008. ^ Between 1999 and 2000, 71% of cases were identified through public facilities compared to private facilities. However, after 2001 rates shifted over more to the private facilities. By 2008, private facilities identified 54.7% of cases, compared to 45.3% identified through public facilities. This may be due to an increase among individuals who have a higher socio-economic status with access to health care insurance. ^ In conclusion, syphilis rates from 1999 through 2008 increased among all race ethnicities, age groups, and genders in Houston/Harris County. Blacks still are disproportionally affected by syphilis infections, and for the first time, White males displayed a significant increase in cases among males. It is vital to Houston public health professionals to have improved surveillance techniques to track syphilis trends and engage high risk groups to better understand their risks in hope of treating and preventing syphilis.^

HIV prevalence and contextual risk-factors among injection drug users in Harris County, Texas

Injection drug use is the third most frequent risk factor for new HIV infections in the United States. A dual mode of exposure: unsafe drug using practices and risky sexual behaviors underlies injection drug users' (IDUs) risk for HIV infection. This research study aims to characterize patterns of drug use and sexual behaviors and to examine the social contexts associated with risk behaviors among a sample of injection drug users. ^ This cross-sectional study includes 523 eligible injection drug users from Houston, Texas, recruited into the 2009 National HIV Behavioral Surveillance project. Three separate set of analyses were carried out. First, using latent class analysis (LCA) and maximum likelihood we identified classes of behavior describing levels of HIV risk, from nine drug and sexual behaviors. Second, eight separate multivariable regression models were built to examine the odds of reporting a given risk behavior. We constructed the most parsimonious multivariable model using a manual backward stepwise process. Third, we examined whether HIV serostatus knowledge (self-reported positive, negative, or unknown serostatus) is associated with drug use and sexual HIV risk behaviors. ^ Participants were mostly male, older, and non-Hispanic Black. Forty-two percent of our sample had behaviors putting them at high risk, 25% at moderate risk, and 33% at low risk for HIV infection. Individuals in the High-risk group had the highest probability of risky behaviors, categorized as almost always sharing needles (0.93), seldom using condoms (0.10), reporting recent exchange sex partners (0.90), and practicing anal sex (0.34). We observed that unsafe injecting practices were associated with high risk sexual behaviors. IDUs who shared needles had higher odds of having anal sex (OR=2.89, 95%CI: 1.69-4.92) and unprotected sex (OR=2.66, 95%CI: 1.38-5.10) at last sex. Additionally, homelessness was associated with needle sharing (OR=2.24, 95% CI: 1.34-3.76) and cocaine use was associated with multiple sex partners (OR=1.82, 95% CI: 1.07-3.11). Furthermore, twenty-one percent of the sample was unaware of their HIV serostatus. The three groups were not different from each other in terms of drug-use behaviors: always using a new sterile needle, or in sharing needles or drug preparation equipment. However, IDUs unaware of their HIV serostatus were 33% more likely to report having more than three sexual partners in the past 12 months; 45% more likely to report to have unprotected sex and 85% more likely to use drug and or alcohol during or before at last sex compared to HIV-positive IDUs. ^ This analysis underscores the merit of LCA approach to empirically categorize injection drug users into distinct classes and identify their risk pattern using multiple indicators and our results show considerable overlap of high risk sexual and drug use behaviors among the high-risk class members. The observed clustering pattern of drug and sexual risk behavior among this population confirms that injection drug users do not represent a homogeneous population in terms of HIV risk. These findings will help develop tailored prevention programs.^

Evaluation of memory B cells among perinatally HIV infected children from Houston Texas

Background: HIV associated B cell exhaustion is a notable characteristic of HIV viremic adults. However, it is not known if such alterations are present in perinatal HIV infected children, whose viral dynamics differs from those seen in adults. In the present study we perform an analysis of B cells subsets and measure antigen-specific memory B cells (MBC) in a pediatric HIV infected cohort. ^ Methods: Peripheral mononuclear cells (PBMC) of perinatal HIV infected individuals are characterized into naïve (CD21hi/CD27−), classic (CD27+), tissue like (CD21lo/CD27 −) and activated MBC (CD27+CD21− ) by FACS. A memory ELISPOT assay is used to detect antibody secreting cells. We measure total IgG and antibodies specific for influenza, HBV, mumps, measles, rubella and VZV. Memory was expressed as spot forming cells (SPC) /million of PBMC. Wilcoxon rank-sum was used to compare unpaired groups and linear regression analysis was used to determine predictors of B cell dysfunction ^ Results: 41 HIV perinatal infected children are included (51.2% females and 65.9% Black). Age at study is median (range) 8.78 years (4.39-11.57). At the time of testing they have a CD4% of 30.9 (23.2-39.4), a viral load (VL) of 1.95 log10 copies/ml (1.68-3.29) and a cumulative VL of 3.4 log10 copy × days (2.7-4.0). Ninety two percent of the children are on cARV for > 6 months. Overall, HIV+ children compared with controls have a significant lower number of IgG and antigen specific SFC. In addition, they have a lower proportion of classical MBC 12.9 (8.09-19.85) vs 29.4 (18.7-39.05); 0.01, but a significant higher proportion of tissue like memory MBC 6.01 (2.79-12.7) vs 0.99 (0.87-1.38); 0.003, compared with controls. Patients are parsed on VL (<400 and ≥ 400 copies/ml) with the objective to evaluate the effect of VL on B cell status. Patients with a VL ≥ 400 copies/ml have a significantly lower IgG, HBV, measles, rubella and VZV SPC compared with those with a VL < 400 copies/ml. There are no significant differences in B cell subpopulations between the groups. A moderate negative correlation was observed between the time of cARV initiation and the frequency of IgG memory B cells, suggesting that early initiation of cARV appears to lead to a better functionality of the IgG memory B cells (P=0.05). A statistically significant positive correlation was observed between the total number of IgG memory cells and the number of antigen-specific memory B cells/SPCs. Suggesting that the progressive recovery of the IgG memory B cell pull goes along with a progressive increase in the number of antigen-specific SPCs. ^ Conclusion: A pediatric cohort in overall good status with respect to HIV infection and on ART has defects in B cell function and numbers (reduced total and antigen specific MBC and increased tissue like and reduced classical MBC).^

Planning, implementation, and evaluation of an HIV -screening program for pregnant women

The purpose of this study was to evaluate the effectiveness of an HIV-screening program at a private health-care institution where the providers were trained to counsel pregnant women about the HIV-antibody test according to the latest recommendations made by the U.S. Public Health Service (PHS) and the Texas legislature. A before-and-after study design was selected for the study. The participants were OB/GYN nurses who attended an educational program and the patients they counseled about the HIV test. Training improved the nurses' overall knowledge about the content of the program and nurses were more likely to offer the HIV test to all pregnant women regardless of their risk of infection. Still, contrary to what was predicted, the nurses did not give more information to increase the knowledge pregnant women had about HIV infection, transmission, and available treatments. Consequently, many women were not given the chance to correctly assess their risk during the counseling session and there was no evidence that knowledge would reduce the propensity of many women to deny being at risk for HIV. On the other hand, pregnant women who received prenatal care after the implementation of the HIV-screening program were more likely to be tested than women who received prenatal care before its implementation (96% vs. 48%); in turn, the likelihood that more high-risk women would be tested for HIV also increased (94% vs. 60%). There was no evidence that mandatory testing with right of refusal would deter women from being tested for HIV. When the moment comes for a woman to make her decision, other concerns are more important to her than whether the option to be tested is mandatory or not. The majority of pregnant women indicated that their main reasons for being tested were: (a) the recommendation of their health-care provider; and (b) concern about the risks to their babies. Recommending that all pregnant women be tested regardless of their risk of infection, together with making the HIV test readily available to all women, are probably the two best ways of increasing the patients' participation in an HIV-screening program for pregnant women. ^

Attitudes of health-care workers toward pregnant, HIV -positive women

The management of HIV infection with antiretroviral drugs has succeeded in increasing survival rates, but the subject of pregnancy in HIV-positive women continues to garner debate. Discrimination and stigma have been identified as barriers to health care, suggesting that women with HIV may be disinclined to seek prenatal care if health-care workers exhibit negative attitudes toward the women's pregnancies. To optimize prenatal and medical care for women with HIV infection, it is important to understand the general social conditions and cultural context in which these women have children. Goffman's treatise on stigma, Foucault's discussion of the knowledge/power matrix, and Bandura's Social Cognitive Theory offer theoretical perspectives by which we can evaluate the gender, race, and class issues that are inherent in pregnancy decision-making for women with HIV infection. It is also necessary to evaluate prevailing attitudes on childbearing toward HIV-positive women and to review the historical background of prejudice in which HIV-positive women make decisions regarding childbearing. ^ This qualitative study used a survey instrument and one-on-one interviews with HIV-infected women to elicit their perceptions of how they were treated by care providers when they became pregnant. It also included interviews with health-care workers to determine what their feelings are about pregnancy within the context of HIV infection. Results of the ethnographic inquiry reveal that most of the women had negative experiences at some point during a pregnancy, but that the situation improved when they sought care from a provider who was familiar with HIV infection. The health-care providers interviewed were firm in their belief that HIV-positive women deserved optimal care and treated the women with respect, but these are individuals who are also experts in providing care to HIV-positive patients. The question remains as to what kind of care HIV-positive women are receiving generally and what types of attitudes they are being subjected to if they see less experienced providers. Further research is also needed to determine whether HIV-positive women from a broader ethnic representation and higher socioeconomic status experience similar negative attitudes. ^

Interferon β transduction of peripheral blood lymphocytes from HIV-infected donors increases Th1-type cytokine production and improves the proliferative response to recall antigens

We are developing a gene therapy method of HIV infection based on the constitutive low production of interferon (IFN) β. Peripheral blood lymphocytes (PBL) from HIV-infected patients at different clinical stages of infection were efficiently transduced with the HMB-HbHuIFNβ retroviral vector. The constitutive low production of IFN-β in cultured PBL from HIV-infected patients resulted in a decreased viral production and an enhanced survival of CD4+ cells, and this protective effect was observed only in the PBL derived from donors having a CD4+ cell count above 200 per mm3. In IFN-β-transduced PBL from healthy and from HIV-infected donors, the production of the Th1-type cytokines IFN-γ and interleukin (IL)-12 was enhanced. In IFN-β-transduced PBL from HIV-infected donors, the production of IL-4, IL-6, IL-10, and tumor necrosis factor α was maintained at normal levels, contrary to the increased levels produced by the untransduced PBL. The proliferative response to recall antigens was partially restored in IFN-β-transduced PBL from donors with an impaired antigen response. Thus, in addition to inhibiting HIV replication, IFN-β transduction of PBL from HIV-infected donors improves several parameters of immune function.

Detection of HIV-1 RNA by nucleic acid sequence-based amplification combined with fluorescence correlation spectroscopy

Nucleic acid sequence-based amplification (NASBA) has proved to be an ultrasensitive method for HIV-1 diagnosis in plasma even in the primary HIV infection stage. This technique was combined with fluorescence correlation spectroscopy (FCS) which enables online detection of the HIV-1 RNA molecules amplified by NASBA. A fluorescently labeled DNA probe at nanomolar concentration was introduced into the NASBA reaction mixture and hybridizing to a distinct sequence of the amplified RNA molecule. The specific hybridization and extension of this probe during amplification reaction, resulting in an increase of its diffusion time, was monitored online by FCS. As a consequence, after having reached a critical concentration of 0.1–1 nM (threshold for unaided FCS detection), the number of amplified RNA molecules in the further course of reaction could be determined. Evaluation of the hybridization/extension kinetics allowed an estimation of the initial HIV-1 RNA concentration that was present at the beginning of amplification. The value of initial HIV-1 RNA number enables discrimination between positive and false-positive samples (caused for instance by carryover contamination)—this possibility of discrimination is an essential necessity for all diagnostic methods using amplification systems (PCR as well as NASBA). Quantitation of HIV-1 RNA in plasma by combination of NASBA with FCS may also be useful in assessing the efficacy of anti-HIV agents, especially in the early infection stage when standard ELISA antibody tests often display negative results.

Nerve growth factor is an autocrine factor essential for the survival of macrophages infected with HIV

Nerve growth factor (NGF) is a neurotrophin with the ability to exert specific effects on cells of the immune system. Human monocytes/macrophages (M/M) infected in vitro with HIV type 1 (HIV-1) are able to produce substantial levels of NGF that are associated with enhanced expression of the high-affinity NGF receptor (p140 trkA) on the M/M surface. Treatment of HIV-infected human M/M with anti-NGF Ab blocking the biological activity of NGF leads to a marked decrease of the expression of p140 trkA high-affinity receptor, a concomitant increased expression of p75NTR low-affinity receptor for NGF, and the occurrence of apoptotic death of M/M. Taken together, these findings suggest a role for NGF as an autocrine survival factor that rescues human M/M from the cytopathic effect caused by HIV infection.