Joint effects of HIV-1 RNA levels and CD4 lymphocyte cells on the risk of specific opportunistic infections

Pneumocystis jirovecii pneumonia in people living with HIV: a review

Pneumocystis jirovecii is a ubiquitous opportunistic fungus that can cause life-threatening pneumonia. People with HIV (PWH) who have low CD4 counts are one of the populations at the greatest risk of Pneumocystis jirovecii pneumonia (PCP). While guidelines have approached the diagnosis, prophylaxis, and management of PCP, the numerous studies of PCP in PWH are dominated by the 1980s and 1990s. As such, most studies have included younger male populations, despite PCP affecting both sexes and a broad age range. Many studies have been small and observational in nature, with an overall lack of randomized controlled trials. In many jurisdictions, and especially in low- and middle-income countries, the diagnosis can be challenging due to lack of access to advanced and/or invasive diagnostics. Worldwide, most patients will be treated with 21 days of high-dose trimethoprim sulfamethoxazole, although both the dose and the duration are primarily based on historical practice. Whether treatment with a lower dose is as effective and less toxic is gaining interest based on observational studies. Similarly, a 21-day tapering regimen of prednisone is used for patients with more severe disease, yet other doses, other steroids, or shorter durations of treatment with corticosteroids have not been evaluated. Now with the widespread availability of antiretroviral therapy, improved and less invasive PCP diagnostic techniques, and interest in novel treatment strategies, this review consolidates the scientific body of literature on the diagnosis and management of PCP in PWH, as well as identifies areas in need of more study and thoughtfully designed clinical trials.

Discontinuing Pneumocystis jirovecii Pneumonia Prophylaxis in HIV-Infected Patients With a CD4 Cell Count <200 cells/mm3

OBJECTIVE

To review the evidence for discontinuing primary and secondary Pneumocystis jirovecii pneumonia (PJP) prophylaxis in HIV-infected patients with a CD4 count <200 cells/mm(3).

DATA SOURCES

We conducted a literature search in MEDLINE, EMBASE, Cochrane Library, Google Scholar, and the International Aids Society Library (up to August 2015) using the following key search terms: Pneumocystis jirovecii, pneumonia, human immunodeficiency virus, primary prophylaxis, secondary prophylaxis, and discontinuation.

STUDY SELECTION AND DATA EXTRACTION

All English-language studies that evaluated discontinuation of primary and/or secondary PJP prophylaxis in HIV-infected patients with CD4 count <200 cells/mm(3) were included.

DATA SYNTHESIS

Five studies were identified, which varied in design, sample size, outcomes, and duration of follow-up. Three studies examined discontinuation of primary and secondary PJP prophylaxis; 1 study evaluated discontinuing primary PJP prophylaxis; and 1 study evaluated stopping secondary PJP prophylaxis. Two out of the 5 studies pooled data for all opportunistic infections. Overall, there was a low incidence of PJP among HIV-infected patients who discontinued primary PJP prophylaxis and were well controlled on antiretroviral therapy (ART).

CONCLUSIONS

Discontinuation of primary PJP prophylaxis appears to be safe in patients on combination ART with a suppressed HIV viral load and a CD4 count >100 cells/mm(3). Additional data are needed to support the safety of discontinuing secondary PJP prophylaxis. Decisions to discontinue PJP prophylaxis in patients with a CD4 count <200 cells/mm(3) should be done on an individual patient basis, taking into consideration clinical factors, including ongoing adherence to ART.

Discontinuation of primary and secondary prophylaxis for opportunistic infections in HIV-infected patients who had CD4+ cell count <200 cells/mm(3) but undetectable plasma HIV-1 RNA: an open-label randomized controlled trial

Abstract The CDC recommends discontinuing opportunistic infections (OIs) prophylaxis in HIV-infected patients who have CD4+ cell count >200 cells/mm(3) after receiving combination antiretroviral therapy (cART). A prospective randomized controlled trial was conducted at Chiang Mai University Hospital from June 1, 2009 to January 31, 2012 in 74 adult HIV-infected patients who had received cART and had CD4+ cell count <200 cells/mm(3) but plasma HIV-1 RNA<50 copies/ml. Forty-three patients (58.1%) were male and the mean age was 41.8±8.1 years; 68 (91.9%) and 59 (79.7%) patients were receiving co-trimoxazole and antifungal prophylaxis, respectively. The median CD4+ cell counts at enrollment were 142 (IQR 108, 161) and 158 (IQR 141, 176) cells/mm(3) among patients who discontinued and continued OIs prophylaxis, respectively (p value=0.041). One of 37 patients (2.7%) in the discontinuation group developed Pneumocystis jiroveci pneumonia, giving the incidence rate of 1.57/1000 person-months. None of the 37 patients in the continuation group developed OIs. The difference in the prevention rates of OIs between groups was -2.7% (95% CI -7.9, 2.5). In conclusion, in the setting where plasma HIV-RNA measurement is available, e.g., Asia-Pacific region, discontinuation of prophylaxis is considerably safe in HIV-infected patients receiving cART with undetectable plasma HIV-RNA but incomplete immune recovery.

Discontinuation of Pneumocystis jirovecii pneumonia prophylaxis with CD4 count <200 cells/µL and virologic suppression: a systematic review

BACKGROUND

HIV viral load (VL) is currently not part of the criteria for Pneumocystis jirovecii pneumonia (PCP) prophylaxis discontinuation, but suppression of plasma viremia with antiretroviral therapy may allow for discontinuation of PCP prophylaxis even with CD4 count <200 cells/µL.

METHODS

A systematic review was performed to determine the incidence of PCP in HIV-infected individuals with CD4 count <200 cells/µL and fully suppressed VL on antiretroviral therapy but not receiving PCP prophylaxis.

RESULTS

Four articles examined individuals who discontinued PCP prophylaxis with CD4 count <200 cells/µL in the context of fully suppressed VL on antiretroviral therapy. The overall incidence of PCP was 0.48 cases per 100 person-years (PY) (95% confidence interval (CI) (0.06-0.89). This was lower than the incidence of PCP in untreated HIV infection (5.30 cases/100 PY, 95% CI 4.1-6.8) and lower than the incidence in persons with CD4 count <200 cells/µL, before the availability of highly active antiretroviral therapy (HAART), who continued prophylaxis (4.85/100 PY, 95% CI 0.92-8.78). In one study in which individuals were stratified according to CD4 count <200 cells/µL, there was a greater risk of PCP with CD4 count ≤100 cells/µL compared to 101-200 cells/µL.

CONCLUSION

Primary PCP prophylaxis may be safely discontinued in HIV-infected individuals with CD4 count between 101-200 cells/µL provided the VL is fully suppressed on antiretroviral therapy. However, there are inadequate data available to make this recommendation when the CD4 count is ≤100 cells/µL. A revision of guidelines on primary PCP prophylaxis to include consideration of the VL is merited.

Decline of CD4⁺ T-cell count before start of therapy and immunological response to treatment in antiretroviral-naive individuals

OBJECTIVE

Treatment guidelines recommend initiation of therapy for individuals experiencing rapid CD4 cell decline. It is not known, however, whether the rate of CD4 cell decline before combination antiretroviral therapy (cART) is related to immunological response following cART.

METHODS

We estimated precART and postcART CD4 cell slopes by mixed models and categorized patients into two groups according to whether estimated precART slopes were above or below the 75th percentile. We compared immunological responses of the two groups through both mixed models and survival techniques. Models were stratified by CD4 cell at baseline, adjusted for HIV RNA, age, sex, HIV transmission group, year of seroconversion, initiation during primary infection, hepatitis C virus and hepatitis B virus serostatus, and cART class.

RESULTS

Of 2038 eligible patients, 1531 and 507 experienced median (interquartile range) precART CD4 cell slope of −105 (−471 to −61) and −42 (−62 to −80) cells/μl, respectively, over 2 years. After adjusting for potential confounders, individuals with shallower decline experienced a slower rate of CD4 cell recovery following cART initiation of +9.5 [95% confidence interval (CI) +6.6 to +12.2] compared to +13.9 (+13.0 to +14.8) cells/μl per month among those with steeper precART decline (P < 0.001). After stratifying by the baseline CD4 cell count, the adjusted relative hazard of an increase from baseline of more than 50 cells/μl was 0.70 (95% CI 0.62−0.79) for those with a shallower vs. steeper precART decline.

CONCLUSION

Findings highlight the existence of a subgroup of individuals with shallower precART CD4 cell decline who experience poorer CD4 cell increases after cART; new studies in this group may provide information to optimize responses to therapy.

Epidemiology of Opportunistic Infections and Its Correlation With CD4 T-Lymphocyte Counts and Plasma Viral Load Among HIV-Positive Patients at a Tertiary Care Hospital in India

The study was conducted to find the correlation of CD4 counts and plasma viral load (PVL) with opportunistic infections (OIs) in HIV-positive patients. A total of 43 drug-naive patients enrolled in the study. Absolute CD4 counts and PVL were measured. On the basis of symptoms, sputum, stool, and blood samples were obtained for laboratory tests. Oral swabs were obtained from all the patients. Pneumocystis jiroveci pneumonia was found in 45.2% patients (odds ratio [OR] = 12.8 for CD4 counts ≤100 cells/ mm3 and 8.5 for PVL >4.0 log10 copies/mL). Pulmonary tuberculosis (TB; OR = 8.0 for PVL >4.0 log10 copies/mL) and streptococcal pneumonia (detected only with CD4 counts <50 cells/mm 3 and PVL >4.0 log10 copies/mL) were seen in 41.9% and 12.9% patients, respectively. Among patients with diarrhea, Giardia lamblia was detected in 31% patients (OR = 3.0 for CD4 counts ≤100 cells/mm3 and 4.0 for PVL >4.0 log10 copies/mL) and Cryptosporidium in 17.2% patients (OR = 1.8 for CD4 counts ≤100 cells/mm3 and found only with PVL >4.0 log10 copies/mL). Shigellosis and Clostridium difficile toxin was present in 13.6% patients and 6.8% patients, respectively.

Comparative radiological features of disseminated disease due to Mycobacterium tuberculosis vs non-tuberculosis mycobacteria among AIDS patients in Brazil

Background

Disseminated mycobacterial disease is an important cause of morbidity and mortality in patients with HIV-infection. Nonspecific clinical presentation makes the diagnosis difficult and sometimes neglected.

Methods

We conducted a retrospective cohort study to compare the presentation of disseminated Mycobacterial tuberculosis (MTB) and non-tuberculous Mycobacterial (NTM) disease in HIV-positive patients from 1996 to 2006 in Brazil.

Results

Tuberculosis (TB) was diagnosed in 65 patients (67.7%) and NTM in 31 (32.3%) patients. Patients with NTM had lower CD4 T cells counts (median 13.0 cells/mm³ versus 42.0 cells/mm³, P = 0.002). Patients with tuberculosis had significantly more positive acid-fast smears (48.0% vs 13.6%, P = 0.01). On chest X-ray, miliary infiltrate was only seen in patients with MTB (28.1% vs. 0.0%, P = 0.01). Pleural effusion was more common in patients with MTB (45.6% vs. 13.0%, P = 0.01). Abdominal adenopathy (73.1% vs. 33.3%, P = 0.003) and splenic hypoechoic nodules (38.5% vs. 0.0%, P = 0.002) were more common in patients with TB.

Conclusion

Miliary pulmonary pattern on X-ray, pleural effusion, abdominal adenopathy, and splenic hypoechoic nodules were imaging findings associated with the diagnosis of tuberculosis in HIV-infected patients. Recognition of these imaging features will help to distinguish TB from NTM in AIDS patients with fever of unknown origin due to disseminated mycobacterial disease.

Pneumocystis jiroveci pneumonia prophylaxis is not required with a CD4+ T-cell count < 200 cells/microl when viral replication is suppressed

OBJECTIVE

To determine the safety of discontinuing Pneumocystis jiroveci pneumonia (PCP) prophylaxis, in patients on effective antiretroviral therapy with CD4+ T-cell counts that have plateaued at < 200 cells/microl.

METHODS

We prospectively evaluated a cohort of HIV infected patients at a multidisciplinary HIV clinic with sustained HIV RNA levels < 50 copies/ml and CD4+ T-cell counts that have plateaued at < 200 cells/microl and who have discontinued PCP prophylaxis.

RESULTS

Nineteen patients fulfilled the above criteria. Eleven had been taking daily trimethoprim-sulfamethoxazole, seven were receiving monthly aerosolized pentamidine, and one patient never received any prophylaxis. The median CD4+ T-cell count at the time of discontinuation and at the most recent determination were 120 (range, 34-184) and 138 (range, 6-201) cells/microl, respectively. To date, patients have been off PCP prophylaxis for a mean of 13.7 +/- 10.6 months and a median of 9.0 (range 3-39) months for a total of 261 patient-months. To date, no patient has developed PCP. This is significantly different from the risk of developing PCP with a CD4+ T-cell count of < 200 cells/microl in untreated HIV infection (rate difference 9.2%; 95% confidence interval, 5.7 to 12.8%; P < 0.05).

CONCLUSION

With sustained suppression of viral replication, PCP prophylaxis may not be necessary, regardless of CD4+ T-cell count. This illustrates a degree of immune recovery that occurs with virologic suppression that is not reflected in absolute CD4+ T-cell count or percentage and suggests that guidelines for P. jiroveci pneumonia prophylaxis may need to be re-evaluated.

Trends in opportunistic infections in the pre- and post-highly active antiretroviral therapy eras among HIV-infected children in the Perinatal AIDS Collaborative Transmission Study, 1986-2004

OBJECTIVE

We sought to determine the impact of highly active antiretroviral therapy on the incidence and prevalence of opportunistic infections in HIV-infected children.

METHODS

Children born from 1986 to 1998 were monitored until 2004 in the Perinatal AIDS Collaborative Transmission Study, sponsored by the Centers for Disease Control and Prevention. We determined the pre-highly active antiretroviral therapy and post-highly active antiretroviral therapy (before and after January 1, 1997, respectively) incidence rates of opportunistic infections among HIV-infected children and characterized the temporal decreases in percentages of CD4+ cells and the mortality rates among patients with and those without incident opportunistic infections.

RESULTS

The overall opportunistic infection incidence declined from 14.4 to 1.1 cases per 100 patient-years; statistically significant reductions were seen in the incidence of the most common opportunistic infections, including Pneumocystis jiroveci pneumonia (5.8 vs 0.3 cases per 100 patient-years), recurrent bacterial infections (4.7 vs 0.2 cases per 100 patient-years), extraocular cytomegalovirus infection (1.4 vs 0.1 cases per 100 patient-years), and disseminated nontuberculous mycobacterial infection (1.3 vs 0.2 cases per 100 patient-years). Kaplan-Meier analysis of time from birth to the first opportunistic infection illustrated more-rapid acquisition of opportunistic infections by HIV-infected children born in the pre-highly active antiretroviral therapy era than by those born later. In the first 3 years of life, there was a faster decline in the percentage of CD4+ cells among children with opportunistic infections. The mortality rate was significantly higher among children with opportunistic infections.

CONCLUSIONS

Reduction in the incidence of opportunistic infections and prolongation of the time to the first opportunistic infection were noted during the post-highly active antiretroviral therapy era. Children who experienced opportunistic infections had higher mortality rates than did those who did not. Younger children (<3 years) who experienced opportunistic infections had faster declines in percentages of CD4+ T cells.

Response to highly active antiretroviral therapy at 6 months and long-term disease progression in HIV-1 infection

OBJECTIVE

To compare the long-term prognostic significance of different definitions of immunologic and virologic responses to highly active antiretroviral therapy (HAART) at 6 months.

METHODS

This was a prospective study conducted in 68 French hospitals. HAART was initiated in 2236 protease inhibitor-naive patients included in the French Hospital Database on HIV. Multivariate Cox proportional hazard models measuring time from 6 months after starting HAART were used to compare the strength of the association between different definitions of immunologic and virologic responses at 6 months and subsequent progression to AIDS or death. The Akaike's Information Criteria were used to identify the most appropriate model.

RESULTS

During a median follow-up of 58 months, 325 patients experienced an AIDS-defining event or died. The model that fitted best was the model in which the CD4 cell count and plasma HIV-1 RNA values attained at 6 months were considered. The risk of clinical progression at 5 years ranged from 7% (95% confidence interval [CI]: 4-10) in patients whose CD4 cell count at 6 months was >or=350 cells/microL and whose HIV-1 RNA concentration was <3 log10 copies/mL to 63% (95% CI: 52-75) in patients whose CD4 cell count at 6 months was <100 cells/microL and whose HIV-1 RNA concentration was >or=5 log10.

CONCLUSIONS

Plasma HIV-1 RNA concentration and CD4 cell count should be taken into account independently when evaluating early response to treatment. The persistent impact of early response on clinical progression at 5 years emphasizes the major importance of the success of first-line HAART.

Natural History and Possible Reactivation of Human Papillomavirus in Human Immunodeficiency Virus–Positive Women

BACKGROUND

Little is known in human immunodeficiency virus (HIV)-positive women about how the combination of plasma HIV RNA level and CD4+ T-cell count is associated with the natural history of human papillomavirus (HPV) infection or about HPV reactivation--whether it occurs and with what frequency in HIV-positive women.

METHODS

HIV-positive (n = 1848) and -negative (n = 514) women were assessed at semiannual visits (total person-years = 5661) for cervicovaginal HPV with polymerase chain reaction assays and for squamous intraepithelial lesions (SILs) by Pap smear. We studied the prevalent detection of HPV and SILs with generalized estimating equations and the incident detection and persistence of HPV and SILs with multivariable Cox models. All statistical tests were two-sided.

RESULTS

We observed a strong interaction between the associations of CD4+ and plasma HIV RNA strata with both prevalent (P(interaction) = .002) and incident (P(interaction) = .001) detection of HPV. Indeed, the hazard ratio for incident HPV detection peaked between 4.0 and 5.0, with either a CD4+ count of less than 200 cells per mm3 or an HIV RNA level of more than 100,000 copies per mL. Although incident HPV detection in all women was associated with the number of recent sex partners (P(trend)<.001), 22% of sexually inactive HIV-positive women with a CD4+ count of less than 200 cells/mm3 also had at least one incidentally detected HPV type. The association between CD4+/HIV RNA strata and HPV persistence was statistically significantly smaller (P<.001) than for incident HPV detection. SIL prevalence, incident detection, and persistence had similar associations with CD4+/HIV RNA strata as HPV (above).

CONCLUSION

In HIV-positive women, plasma HIV RNA level and CD4+ count in combination appear to have a strong and statistically interactive association with incident detection of HPV, some of which may reflect HPV reactivation (e.g., in sexually inactive women). The more moderate association between HIV coinfection and HPV persistence could partly explain why cervical cancer rates have not reached more epidemic proportions in HIV-positive women.

Mycobacterium avium complex in patients with HIV infection in the era of highly active antiretroviral therapy

Disseminated Mycobacterium avium complex (MAC) infection is a common complication of late-stage HIV-1 infection. Since the advent of highly active antiretroviral therapy (HAART), the rate of MAC infection has declined substantially, but patients with low CD4 cell counts remain at risk. Among patients in the Johns Hopkins cohort with advanced HIV disease, the proportion developing MAC has fallen from 16% before 1996 to 4% after 1996, with a current rate of less than 1% per year. Factors associated with developing MAC include younger age, no use of HAART, and enrollment before 1996. Prophylaxis with azithromycin or clarithromycin is recommended for all patients with CD4 counts less than 50 cells/mL. Optimum treatment for disseminated MAC includes clarithromycin and ethambutol, and another investigation suggests that the addition of rifabutin might reduce mortality. Both prophylaxis and treatment of disseminated MAC can be discontinued in patients who have responded to HAART, and specific guidelines for withdrawing treatment have been published. Although HAART has altered the frequency and outcome of MAC infection, it remains an important complication of AIDS.

Cytomegalovirus (CMV) and human immunodeficiency virus (HIV) burden, CMV end-organ disease, and survival in subjects with advanced HIV infection (AIDS Clinical Trials Group Protocol 360)

We undertook a prospective study to analyze cytomegalovirus (CMV) end-organ disease (EOD) in subjects with advanced human immunodeficiency virus (HIV) infection. Of 403 individuals without prior CMV EOD who were followed up for a median of 151 weeks, 56 died and 21 developed CMV EOD. Twenty of the subjects with CMV EOD had CD4 cell counts of < or =50 cells/mm3 and HIV RNA level of >10,000 copies/mL of plasma at baseline; in these 20 subjects, an increase of CMV DNA level to greater than the quantification limits was associated with CMV EOD. A CD4 cell count of < or =100 cells/mm3 and an HIV RNA level of >10,000 copies/mL of plasma at baseline, a CMV DNA level of >200 copies/mL of blood during follow-up, or development of CMV EOD were all associated with decreased survival. HIV-infected subjects with CD4 cell counts of < or =50 cells/mm3 and HIV RNA levels of >10,000 copies/mL of plasma should have blood fractions screened for CMV DNA; if CMV DNA is detected, CMV prophylaxis might be considered.

Lopinavir/ritonavir: a review of its use in the management of HIV infection

Lopinavir is a novel protease inhibitor (PI) developed from ritonavir. Coadministration with low-dose ritonavir significantly improves the pharmacokinetic properties and hence the activity of lopinavir against HIV-1 protease. Coformulated lopinavir/ritonavir was developed for ease of administration and to ensure both drugs are taken together, as part of combination therapy with other antiretroviral agents. Coformulated lopinavir/ritonavir-based regimens provide adequate and durable suppression of viral load and sustained improvements in CD4+ cell counts, as demonstrated in randomised trials in antiretroviral therapy-naive and -experienced adults and children. To date, development of primary resistance to lopinavir/ritonavir has not been observed in 470 antiretroviral therapy-naive patients treated for >48 weeks. The lopinavir/ritonavir-based regimen was more effective than nelfinavir in antiretroviral therapy-naive HIV-1-infected patients in a phase III trial. The coformulation is also effective as 'salvage' therapy, as shown by low cross-resistance rates in patients who failed to respond to treatment with other PIs in phase II trials. Coformulated lopinavir/ritonavir was well tolerated in both antiretroviral therapy-naive and -experienced HIV-1-infected adults and children with low rates of study drug-related treatment discontinuations. The most common adverse event in adults associated with lopinavir/ritonavir was diarrhoea, followed by other gastrointestinal disturbances, asthenia, headache and skin rash. The incidence of moderate-to-severe adverse events in children was low, skin rash being the most common. Changes in body fat composition occurred with equal frequency in lopinavir/ritonavir- and nelfinavir-treated naive patients, through week 60 in a phase III study. Although laboratory abnormalities occurred with similar frequency in both treatment groups, triglycerides grade 3/4 elevations were significantly more frequent with lopinavir/ritonavir. Total cholesterol and triglycerides grade 3/4 elevations appear to occur more frequently in PI-experienced than in PI-naive lopinavir/ritonavir-treated patients. A number of clinically important drug interactions have been reported with lopinavir/ritonavir necessitating dosage adjustments of lopinavir/ritonavir and/or the interacting drugs, and several other drugs are contraindicated in patients receiving the coformulation.

CONCLUSION

Coformulated lopinavir/ritonavir is a novel PI that, in combination with other antiretroviral agents, suppresses plasma viral load and enhances immunological status in therapy-naive and -experienced patients with HIV-1 infection. Lopinavir/ritonavir appears more effective than nelfinavir in 'naive' patients and is also suitable for 'salvage' therapy, because of its high barrier to development of resistance. Given its clinical efficacy, a tolerability profile in keeping with this class of drugs, favourable resistance profile and easy-to-adhere-to administration regimen, coformulated lopinavir/ritonavir should be regarded as a first-line option when including a PI in the management of HIV-1 infection.

OVERVIEW OF PHARMACODYNAMIC PROPERTIES

Lopinavir/ritonavir is a coformulation of two structurally related protease inhibitor (PI) antiretroviral agents. Lopinavir is a highly potent and selective inhibitor of the HIV type 1 (HIV-1) protease, an essential enzyme for production of mature, infective virus. It acts by arresting maturation of HIV-1 thereby blocking its infectivity. Thus, the main antiviral action of lopinavir is to prevent subsequent infections of susceptible cells; it has no effect on cells with already integrated viral DNA. Lopinavir has an approximate, equals 10-fold higher in vitro activity against both wild-type and mutant HIV-1 proteases than ritonavir; however, its in vivo activity is greatly attenuated by a high first-pass hepatic metabolism. The low-dose ritonavir coadministered with lopinavir inhibits metabolic inactivation of lopinavir and acts only as its pharmacokinetic enhancer. Therefore, the antiretroviral activity of roviral activity of coformulated lopinavir/ritonavir 400/100mg twice daily is derived solely from lopinavir plasma concentrations. Combining lopinavir with low-dose ritonavir produces lopinavir concentrations far exceeding those needed to suppress 50% of in vitro and in vivo viral replication in CD4+ cells and monocyte/macrophages (main human reservoirs of HIV-1 infection). Thus far, no resistance to lopinavir has been detected in clinical trials in antiretroviral therapy-naive patients treated for up to 204 weeks and only 12% of HIV-1 strains from patients in whom prior treatment with multiple PIs have failed, have been observed to develop resistance to coformulated lopinavir/ritonavir. A strong negative correlation was found between the number of PI mutations at baseline and the viral response rates achieved with lopinavir/ritonavir-based regimens in PI-experienced patients, indicating that resistance to lopinavir increases with increasing number of PI mutations and that five PI mutations represent the clinically relevant genotypic breakpoint for lopinavir.

OVERVIEW OF PHARMACOKINETIC PROPERTIES

The absolute bioavailability of lopinavir coformulated with ritonavir in humans has not yet been established. Multiple-dosage absorption pharmacokinetics of lopinavir/ritonavir 400/100mg twice daily (the mean peak [C(max)] and trough [C(trough)] plasma concentrations at steady-state and the 12-hour area under the plasma concentration-time curve [AUC(12)] of either drug) were stable in antiretroviral therapy-naive and single PI-experienced adult patients receiving therapy over a 24-week evaluation period. The C(trough) values of lopinavir, achieved with lopinavir/ritonavir 400/100mg twice daily, were median 84-fold higher than the protein binding-adjusted 50% effective concentration (EC(50)) of lopinavir against wild-type HIV-1 in antiretroviral therapy-naive HIV-1-infected patients in a phase II study. Bioavailability of lopinavir administered in either the capsule or the liquid lopinavir/ritonavir formulation can be increased substantially with concurrent ingestion of food with moderate-to-high fat content. At steady state, lopinavir is approximately 98-99% plasma protein bound and the percentage of its unbound (i.e. pharmacologically active) fraction is dependent on total drug plasma concentration. Both lopinavir and ritonavir penetrate poorly into the human genital tracts and the cerebrospinal fluid. Both agents undergo extensive and rapid first-pass metabolism by hepatic cytochrome P450 (CYP) 3A4 isoenzyme. However, ritonavir also potently inhibits this enzyme and acts as a pharmacokinetic enhancer of lopinavir. The elimination half-life and apparent oral clearance of lopinavir average approximately 4-6 hours and approximately 6-7 L/h, respectively, with lopinavir/ritonavir 400/100mg twice daily administration. Less than 3% and 20% of the lopinavir dose is excreted unchanged in the urine and faeces, respectively. Limited data show similar pharmacokinetics of lopinavir in children as in adults.

DRUG INTERACTIONS

Coformulated lopinavir/ritonavir has the potential to interact with wide variety of drugs via several mechanisms, mostly involving the CYP enzymes. Coadministration of lopinavir/ritonavir is contraindicated with certain drugs (i.e. flecainide, propafenone, astemizole, terfenadine, ergot derivatives, cisapride, pimozide, midazolam and triazolam) that are highly dependent on CYP3A or CYP2D6 for clearance and for which elevated plasma concentrations are associated with serious and/or life-threatening events. Coadministration with lopinavir/ritonavir is also not recommended for drugs or herbal products (i.e. rifampicin [rifampin] and St. John's wort [Hypericum perforatum]) that may substantially reduce lopinavir plasma concentrations, or drugs whose plasma concentrations elevated by the coformulation may lead to serious adverse reactions (i.e. simvastatin and lovastatin). However, a recent study in healthy volunteers suggests that adequate lopinavir concentrations may be achieved during rifampicin coadministration by increasing the twice-daily dosage of lopinavir/ritonavir in conjunction with therapeutic drug monitoring. The liquid (but not the capsule) formulation of lopinavir/ritonavir contains 42.4% ethanol (v/v) and should not be coadministered with drugs capable of producing disulfiram-like reactions (e.g. disulfiram, metronidazole). Coadministration with saquinavir or indinavir requires no dosage adjustment, whereas coadministration with amprenavir, nevirapine or efavirenz requires a dosage increase of the coformulation typically by 33%. As the oral bioavailability of both didanosine and lopinavir/ritonavir is significantly affected by concurrent food ingestion, didanosine should be administered 1 hour before or 2 hours after lopinavir/ritonavir has been taken with food. Interactions between lopinavir/ritonavir and other nucleoside reverse transcriptase inhibitors (NRTIs) are not expected. The coformulation is also likely to increase plasma concentrations of non-antiretroviral drugs metabolised through the CYP3A pathway. To reduce the risk of their toxicity when coadministered with lopinavir/ritonavir, the recommended actions include: (i) monitoring of the drug plasma concentration (antiarrhythmics and immunosuppressants) or the international normalised ratio (warfarin); (ii) the use of alternative treatment (atorvastatin) or birth control methods (ethinylestradiol); and (iii) dosage adjustment (clarithromycin [only in patients with renal failure], rifabutin, dihydropyridine calcium-channel blockers, atorvastatin, ketoconazole and itraconazole). (ABSTRACT TRUNCATED)

Time-updated CD4+ T lymphocyte count and HIV RNA as major markers of disease progression in naive HIV-1-infected patients treated with a highly active antiretroviral therapy: the Aquitaine cohort, 1996-2001

In naive HIV-1 infected patients who start a highly active antiretroviral therapy (HAART), the relationship between time-updated CD4+ cell count, HIV RNA, and clinical progression (new AIDS-defining event or death) is incompletely understood. A 2-step statistical approach was adopted: first, modeling the evolution of the 2 markers taking into account left-censoring of HIV RNA and, second, studying their respective effect on clinical progression. The study sample consisted in 551 previously untreated patients of the Aquitaine Cohort who started their first HAART regimen between 1996 and 2000. During a median follow-up of 33 months, 46 patients experienced a new AIDS-defining diagnosis and 23 died. In multivariate survival analysis, time-updated CD4+ cell count (hazard ratio [HR] = 1.92 for 100 cells/mm3 lower, P < 10(-4) and HIV RNA (HR = 1.30 for 1 log(10) copies/mL higher, P = 0.04) on continuous scale were associated with clinical progression. When analyzing the effect of updated biomarkers using usual thresholds, the association with clinical progression was weaker for CD4+ but still significant (P = 0.007) whereas it remained only significant for updated HIV RNA above 4 log(10) copies/mL (P = 0.01). The prognostic information of updated HIV RNA adjusted on updated CD4+ is significant but depends on how the markers are taken into account. Clinical decisions and interpretation of clinical trial results must weigh the signification of each of these 2 biomarkers.

Short-term CD4 cell response after highly active antiretroviral therapy initiated at different times from seroconversion in 1,500 seroconverters

The effect of HIV infection duration and CD4 cell count on short-term CD4 response was evaluated in treatment-naive seroconverters using logistic regression adjusted for CD4 count before highly active antiretroviral therapy (HAART) as well as for exposure category, age, sex, acute infection, and cohort. This association was also investigated in pretreated seroconverters, further adjusting for prior therapy. CD4 response (increase of >100 cells/microL at 6 months) was more likely if HAART was initiated in the first year following seroconversion (OR = 1.50 [95% CI: 1.07-2.10] compared with 2-5 years). There was no improvement in response from initiating HAART with CD4 count >350 cells/microL compared with 201 to 350 cells/microL. Below 200 cells/microL, however, the chance of a CD4 response appeared to be reduced (OR = 0.72 [95% CI: 0.40-1.28] for 0-200 cells/microL compared with 201-350 cells/microL, P = 0.26). Results were similar for pretreated individuals. Further, in pretreated individuals, a CD4 response was less likely if the CD4 nadir was lower than the pre-HAART CD4 count (OR = 0.18 [95% CI: 0.10-0.36] for >150 cells/microL difference between nadir and pre-HAART CD4 count vs. no difference, P < 0.001). Given the limitations of observational studies, particularly the inability to control for unmeasured confounders, these findings suggest that the initiation of HAART within the first year following seroconversion appears to improve short-term immunologic response. After that time, there is little to be gained in terms of short-term response from initiating HAART before reaching a CD4 count of 200 cells/microL.

CD4(+) T cell levels are decreased during active CMV infection in kidney transplant recipients

The numbers of T lymphocytes and T cell subsets (CD2(+), CD3(+), CD4(+), CD8(+)), activated T cells (CD26(+)), B cells (CD19(+)), granulocytes (CD15(+)) and natural killer cells (CD16/56) were monitored by flow cytometry in 79 kidney transplant recipients, 35 of whom had cytomegalovirus infection. The percentages of these cells were correlated with viral load, as determined by cytomegalovirus antigenemia. Development of cytomegaloviral infection coincided with a significant reduction in the percentages of CD4(+) (P < 0.005) and CD3(+) (P < 0.05) cells. Monitoring of lymphocyte subsets may provide useful information on immunological events during cytomegaloviral infection.

Nontuberculous mycobacteria in the HIV infected patient

The reduction in disseminated NTM infections caused by HAART is one of the success stories in the history of HIV in the developed world. Despite this success, these diseases still occur and may have atypical presentations in patients receiving HAART. Clinicians treating HIV-infected patients must remain familiar with the diagnosis and treatment of these diseases and implement prevention strategies when indicated.

Predictive value of HIV-1 viral load on risk for opportunistic infection

OBJECTIVE

The relationship between HIV-1 viral load and the risk for opportunistic infection (OI) was examined in Adult AIDS Clinical Trial Group (AACTG) 722, a virology substudy of AACTG 323: a phase 4 randomized study designed to examine the use of chronic suppressive versus episodic fluconazole therapy.

METHODS

The primary analysis used a case-control sampling scheme with two controls per "case" (subjects that developed an OI) matched by gender, age, and time on study. Forty-five cases and matched controls were identified and used in the analysis.

RESULTS

Study 722 accrued 518 subjects between 5/97 and 11/99. Forty-five subjects developed serious OIs or refractory candidiasis. Median baseline CD4 count was 24 cell/mm3 for cases and 46 for controls (p =.003). Median viral load (VL) was 5.02 log10 copies/mL for cases and 4.08 for controls (p =.002). Multivariate analysis found four independent variables associated with time to OI: baseline VL and CD4 (RR = 2.2 per log increment and 6.0 per 50-cell increment, respectively), a one log increase in VL at any time (RR = 15), and history of an OI (RR = 5.2).

CONCLUSIONS

VL and changes in VL were independently associated with risk of development of OIs in a prospective study and should be considered by clinicians when assessing patients for risk of OI.

Association of adherence to Mycobacterium avium complex prophylaxis and antiretroviral therapy with clinical outcomes in Acquired Immunodeficiency Syndrome

High-level adherence to regimens of combination antiretroviral therapy and prophylactic medications for opportunistic infections (OIs) is crucial to their success. However, little is known about the association between adherence to these life-sustaining therapies and such clinical outcomes as progression of acquired immune deficiency syndrome (AIDS) or development of OIs. We assessed adherence to regimens of antiretroviral and Mycobacterium avium complex (MAC) prophylactic medications in 643 patients enrolled in a trial of MAC prophylaxis. By week 56 of the study follow-up, 42% of the patients reported nonadherence to MAC prophylaxis, whereas one-quarter of the patients reported nonadherence to potent antiretroviral regimens. Nonadherence to both MAC prophylaxis and antiretroviral therapy was associated with higher human immunodeficiency virus (HIV) type 1 RNA levels and a significant increase in the risk of developing an AIDS-defining complication or death. Predictors of nonadherence are presented. These results underscore the clinical significance of adherence to HIV therapy and may be helpful in designing interventions to optimize the management of HIV by improving adherence.

Highly active antiretroviral therapy-associated regression of cytomegalovirus retinitis: long-Term results in a small case series

PURPOSE

To report the stability of acquired immunodeficiency syndrome (AIDS)-associated cytomegalovirus (CMV) retinitis lesions that have undergone regression in the absence of specific anti-CMV medications owing to highly active antiretroviral therapy (HAART)-generated immune recovery.

METHODS

The initial examination revealed HAART-associated regression of CMV retinitis lesions in eight subjects at two institutions. Patients were monitored for recurrences of CMV activity. CD4+ T-lymphocyte counts and human immunodeficiency virus (HIV) loads were measured.

RESULTS

All patients had positive initial responses to HAART with an average HIV load decrease of 2.26 log units (range 0.3-5.57). Mean CD4+ T-lymphocyte count at baseline was 45.6 (range 4-107) and increased by an average of 132.5 (range 7-266) within the first 2 to 4 months of HAART. Patients were observed for an average of 15.5 months (range 11-20 months). Six subjects had a vigorous and sustained response to therapy, achieving an average HIV load of 9,400 copies/mL (3.32 log10 decrease) and CD4+ T-lymphocyte count of 158.2 cells/microL. These patients had no CMV retinitis progression. By contrast, two others who attained an average log10 decrease of only 0.48 had modest and short-lived increases in the CD4+ T-lymphocyte count. These patients experienced reactivation of CMV retinitis after 5 and 7 months, respectively.

CONCLUSIONS

Regressed CMV retinitis may remain healed for long periods. However, failure of HAART to induce substantial decreases in HIV load may predict poor or unsustainable rises in the CD4+ T-lymphocyte count and presage recurrence of CMV retinitis. Vigilance in ophthalmic examinations is especially mandatory in these subjects.

Efficacy of macrolides used in combination with ethambutol, with or without other drugs, against Mycobacterium avium within human macrophages

The activities of clarithromycin or roxithromicin used in combination with other antimicrobial drugs were tested in human macrophages experimentally infected with 23 strains of Mycobacterium avium. Overall, clarithromycin-ethambutol-rifampicin was the most active combination tested. The reduction in intracellular viable bacilli was found to be more than 1 log(10) for 95% and more than 2 logs(10) for 65% of the strains. The second most active combination was roxithromycin-ethambutol-rifampicin, which was found to be bactericidal for about 80% and highly bactericidal for 20% of the strains. Others combinations were only bacteriostatic or weakly bactericidal for many of the strains. The addition of a third drug did not necessarily promote enhanced bacterial killing inside the macrophage.

Viral load as an independent risk factor for opportunistic infections in HIV-infected adults and adolescents

OBJECTIVE

We investigated whether HIV plasma RNA (viral load; VL) predicts risk for opportunistic infections (OI) in HIV-infected persons, independent of CD4 lymphocyte count and other factors that might affect disease outcome.

METHODS

Among persons who had initiated antiretroviral therapy (ART), we studied the risk for OI following a VL measurement in the Centers for Disease Control and Prevention Adult and Adolescent Spectrum of HIV Disease (ASD) Project, a medical record review study of HIV-infected persons in 11 US cities. Analysis was limited to persons who had initiated ART and who had VL data, primarily from the period 1996-1999. Persons were considered at risk for OI for 1 to 6 months after a given VL; risk for OI was assessed using a Poisson multiple regression model controlling for CD4 lymphocyte count, ART, and other variables potentially associated with development of OI: history of AIDS OI, age, sex, race, HIV risk category, OI prophylaxis, and calendar year.

RESULTS

Although decreasing CD4 count was the strongest predictor of risk for OI [relative risk (RR), 13.3 for persons with CD4 lymphocyte count < 50 x 10(6)/l compared with persons with CD4 lymphocyte count > or = 500 x 10(6)/l], increasing VL was independently associated with increased risk [RR, 1.6, 1.9, 2.7, and 3.5 for VL of 7000-19 999, 20 000-54 999, 55 000-149 999, and > or = 150 000 copies/ml (by reverse transcription-PCR), respectively, compared with VL < 400]. Similar results were obtained when the risk period was reduced to 5, 4, 3, and 2 months after VL measurement.

CONCLUSIONS

VL is an independent risk factor for OI and should be considered in special situations, such as in decisions to discontinue primary or secondary OI prophylaxis after CD4 lymphocyte counts have increased in response to ART.

A prospective study of discontinuing primary and secondary Pneumocystis carinii pneumonia prophylaxis after CD4 cell count increase to > 200 x 106 /l

OBJECTIVE

To assess the incidence of Pneumocystis carinii pneumonia (PCP) after discontinuation of either primary or secondary prophylaxis.

DESIGN

This was a prospective, non-randomized, non-blinded study.

SETTING

Twenty-five University-based AIDS Clinical Trials Group units.

PARTICIPANTS

Participants either had a CD4 cell count < or = 100 x 106/l at any time in the past and no history of confirmed PCP (group I; n = 144), or had a confirmed episode of PCP > or = 6 months prior to study entry (group II; n = 129). All subjects had sustained CD4 cell counts > 200 x 106/l in response to antiretroviral therapy.

INTERVENTIONS

Subjects discontinued PCP prophylaxis within 3 months or at the time of study entry. Evaluations for symptoms of PCP and CD4 cell counts were performed every 8 weeks. Prophylaxis was resumed if two consecutive CD4 cell counts were < 200 x 106/l.

MAIN OUTCOME MEASURE(S)

The main outcome was development of PCP.

RESULTS

No cases of PCP occurred in 144 subjects (median follow-up, 82 weeks) in group I or in the 129 subjects (median follow-up, 63 weeks) in group II (95% upper confidence limits on the rates of 1.3 per 100 person-years and 1.96 per 100 person-years for groups I and II, respectively). Eight subjects (five in group I and three in group II) resumed PCP prophylaxis after two consecutive CD4 cell counts < 200 x 106/l.

CONCLUSIONS

The risk of developing initial or recurrent PCP after discontinuing prophylaxis is low in HIV-infected individuals who have sustained CD4 cell count increases in response to antiretroviral therapy. Neither lifelong primary nor secondary PCP prophylaxis is necessary.

Overview of the effectiveness of triple combination therapy in antiretroviral-naive HIV-1 infected adults

AIM

To estimate the effectiveness of triple combination therapy in antiretroviral-naive adults.

METHODS

A systematic overview of results from clinical trials involving triple combination therapy with dual nucleoside reverse transcriptase inhibitors (NRTI) and: a protease inhibitor (PI triple); a non-nucleoside reverse transcriptase inhibitor (NNRTI triple); or a third NRTI (triple NUC). Data from 23 clinical trials involving 31 independent treatment groups, 19 unique antiretroviral regimens, and 3257 enrolled patients were included in this study.

RESULTS

Median log(10) baseline plasma HIV RNA and CD4 cell count over all trials averaged 4.69 (49,329 copies/ml) and 375 x 10(6) cells/l, respectively. The overall estimated percentage of patients with plasma HIV RNA < or = 400 copies/ml at 24 weeks was 64% [95% confidence interval (CI), 60 to 67%]. The percentages of patients with plasma HIV RNA < or = 50 copies/ml at 48 weeks by drug class were: PI triple, 46% (95% CI, 41 to 52%); NNRTI triple, 51% (95% CI, 43 to 59%); triple NUC, 45% (95% CI, 36 to 54%). The CD4 cell count increase over all trials at 24 and 48 weeks averaged +123 x 10(6) cells/l (95% CI, 111 x 10(6) to 135 x 10(6) cells/l) and +160 x 10(6) cells/l (95% CI, 146 x 10(6) to 175 x 10(6) cells/l), respectively and did not differ between drug classes. In multivariable regression analysis, neither baseline plasma HIV RNA level and CD4 cell count nor treatment regimen predicted plasma HIV RNA < or = 50 copies/ml at week 48. However, pill count was significantly negatively associated with plasma HIV RNA < or = 50 copies/ml at week 48 (P = 0.0085).

CONCLUSIONS

The results suggest that three drug regimens containing two NRTI with a PI, a NNRTI, or a third NRTI may provide comparable activity, and practical issues such as daily pill burden should be considered when choosing a treatment regimen.

Relation between CD4 cell counts and HIV RNA levels at onset of opportunistic infections

OBJECTIVE

To evaluate the relation between CD4 and HIV RNA levels at the onset of specific opportunistic infections (OIs) in HIV-infected patients.

DESIGN AND METHODS

The OIs occurring between June 1996 and December 1998 were retrospectively reviewed, considering only the episodes of major and minor OIs in patients with simultaneously available CD4 and plasma HIV RNA determinations before clinical onset who had been untreated or on stable antiretroviral therapy (ART) for at least 2 months.

RESULTS

Two hundred seventy-four episodes of different OIs were considered in 216 patients; the median CD4 count was 35 cells/mm3 (range: 0-1154 cells/mm(3)), and the median HIV RNA count was 5.1 log cp/mL (range: < 1.9-6.7 log copies/ml). The different HIV RNA levels were significantly associated with different OIs regardless of CD4 and ART (p < .0001), even when only those occurring in patients with a CD4 count of < or = 50 cells/mm(3) were considered (p = .0049). Kaposi sarcoma, esophageal candidiasis, oropharyngeal candidiasis, and Mycobacterium avium complex disease were associated with significantly above-average median HIV RNA levels, and varicella-zoster virus infection was associated with below-average levels.

CONCLUSIONS

Different OIs are associated at their onset with significantly different HIV RNA levels, regardless of CD4 cell counts and ART.

Qualitative and quantitative PCR measures of cytomegalovirus in patients with advanced HIV infection who require transfusions

The Viral Activation Transfusion Study (VATS) was a randomized trial that compared leukocyte-reduced transfusions with unfiltered red blood cell transfusions in HIV and cytomegalovirus (CMV) antibody-positive patients with anemia who were undergoing their first blood transfusion. The relations of the baseline qualitative and quantitative polymerase chain reaction (PCR) measures of plasma CMV viremia, HIV RNA, CD4(+) cell counts, and quality of life in these study subjects were examined. The 511 study subjects had a median CD4(+) cell count equal to 15 cells/mm3, and 110 (21.5%) had CMV viremia by qualitative assay. In multivariate models, frequency of positive qualitative CMV increased with decreasing CD4(+) cell counts (p =.04 trend), higher HIV RNA (p <.001), and a history of CMV disease (p <.001). Quantitative CMV PCR were performed on the 110 qualitative assay-positive study subjects. Median CMV viral load was 1780 copies/ml. In multivariate regression models, lower CD4(+) cell count (p =.03), and a history of CMV disease (p <.001) correlated with the level of CMV load. HIV RNA load and CMV load were not correlated. A lower Karnofsky score was associated with both the presence and quantity of CMV DNA.

Discontinuation of primary prophylaxis in HIV-infected patients at high risk of Pneumocystis carinii pneumonia: prospective multicentre study

OBJECTIVES

To assess the safety of discontinuation of primary prophylaxis in HIV-infected patients on antiretroviral combination therapy at high risk of developing Pneumocystis carinii pneumonia.

DESIGN

Prospective multicentre study.

PATIENTS AND METHODS

The incidence of P. carinii pneumonia after discontinuation of primary prophylaxis was studied in 396 HIV-infected patients on antiretroviral combination therapy who experienced an increase in their CD4 cell count to at least 200 x 10(6)/l and 14% of total lymphocytes; the study population included 191 patients with a history of CD4 cell counts below 100 x 10(6)/l (245 person-years) and 144 patients with plasma HIV RNA above 200 copies/ml (215 person-years).

RESULTS

There was one case of Pneumocystis pneumonia, an incidence of 0.18 per 100 person-years [95% confidence interval (CI), 0.005--1.0 per 100 person-years]. No case was diagnosed in groups with low nadir CD4 cell counts (95% CI, 0--1.2 per 100 person-years) or detectable plasma HIV RNA (95% CI, 0--1.4 per 100 person-years).

CONCLUSIONS

Discontinuation of primary prophylaxis against Pneumocystis pneumonia is safe in patients who have responded with a sustained increase in their CD4 cell count to antiretroviral combination therapy, irrespective of the CD4 cell count nadir and the viral load at the time of stopping prophylaxis.

Predictive role of the three-month CD4 cell count in the long-term clinical outcome of the first HAART regimen

The aim was to evaluate whether the three-month CD4 cell counts are a reliable predictor of the long-term clinical outcome of HAART-treated patients, by an observational study of 585 patients initiating HAART in a clinical setting. Clinical failure was defined as the occurrence of new or recurrent AIDS-defining events or death, and was analysed by means of intention-to-treat, univariate and multivariate analyses. An adjusted Cox regression model was used to evaluate the effect of three-month CD4+ counts on clinical outcome. Clinical failure occurred in 65 patients (11.1%) during a median follow-up of 31 months (1-65) as a result of new AIDS-defining events (ADEs) in 48 patients, ADE recurrence in six, and death in 11. The mean (median; range) CD4+ counts were 156/microL (155; 4--529) in patients with and 362/microL (326; 18--1162) in patients without clinical failure (P < .0001). Moreover, the proportion of patients with mean CD4+ counts < 200 microL was higher in those experiencing subsequent clinical failure (chi2: 41.11; P< .00001). Multivariate analysis showed that baseline CD4+ counts < 50 microL, HIV-RNA > 100,000 copies/mL and AIDS at baseline predicted failure; after adjusting for three-month CD4+ counts, this marker was the only one independently associated with clinical failure (HR 2.93; 95% Cl: 1.16--7.38). The three-month immunologic response is a reliable predictor of long-term clinical outcome.

Prophylaxis of opportunistic infections

Potent antiretroviral therapy has improved the outcome of HIV-associated OIs, which have declined dramatically. The clinical manifestations of some OIs (e.g., CMV retinitis, MAC infection, and TB) have changed. These effects likely are related to the immune reconstitution observed with the suppression of HIV replication. These changes have affected approaches to the prophylaxis of OIs. Withdrawal of some prophylaxis in patients who show evidence of immune reconstitution is possible, although clinical studies are needed to address further specific questions about the timing of withdrawal. The best way to prevent OIs is to give effective antiretroviral therapy--the future epidemiology of OIs is linked inextricably with the effectiveness of future antiretroviral treatments.

The dominant source of CD4+ and CD8+ T-cell activation in HIV infection is antigenic stimulation

To distinguish between antigenic stimulation and CD4+ T-cell homeostasis as the cause of T-cell hyperactivation in HIV infection, we studied T-cell activation in 47 patients before and during highly active antiretroviral therapy (HAART). We show that expression of human leukocyte antigen (HLA)-DR, CD38, and Ki67 on T cells decreased during HAART but remained elevated over normal values until week 48 of therapy. We confirm previous reports that T-cell activation correlates positively with plasma HIV RNA levels (suggesting antigenic stimulation), and negatively with CD4 count (suggesting CD4+ T-cell homeostasis). However, these correlations may be spurious, because misleading, due to the well-established negative correlation between CD4 count and plasma HIV RNA levels. To resolve this conflict, we computed partial correlation coefficients. Correcting for CD4 counts, we show that plasma HIV RNA levels contributed to T-cell hyperactivation. Correcting for plasma HIV RNA levels, we show that CD4+ T-cell depletion contributed to T-cell activation. Correcting for both, activation of CD4+ and CD8+ T cells remained positively correlated. Because this suggests that CD4+ and CD8+ T-cell activation is caused by a common additional factor, we conclude that antigenic stimulation by HIV or other (opportunistic) infections is the most parsimonious explanation for T-cell activation in HIV infection. Persistence of HIV antigens may explain why T-cell activation fails to revert to levels found in healthy individuals after 48 weeks of therapy.

Discontinuing prophylaxis for opportunistic infection: guiding principles

Several large observational studies have documented the reduced risk of opportunistic infections among recipients of potent combination antiretroviral therapy. These data raise the question of whether subjects who respond to antiretroviral therapy need to continue prophylaxis for opportunistic infection. Factors to consider when deciding whether it is safe to discontinue prophylaxis include the following: (1) the risk of developing the specific opportunistic infection; (2) the consequences of the infection (morbidity and availability of effective therapy); (3) both the short-term and long-term toxicity of the agent used for prophylaxis; (4) the potential for drug interactions between the agent used for prophylaxis and other therapies for human immunodeficiency virus infection; (5) the psychological benefit of discontinuing a treatment during the course of a chronic disease; (6) the risk of development of drug resistance during prophylaxis; and (7) costs. This article reviews current data on predicting risk of opportunistic infection, the most critical of these factors.

Discontinuation of secondary prophylaxis for opportunistic infections in HIV-infected patients receiving highly active antiretroviral therapy

BACKGROUND

Immune reconstitution following the introduction of highly active antiretroviral therapies (HAART) has lead to a remarkable reduction in the incidence of opportunistic infections (OI) in subjects with advanced HIV disease. Moreover, discontinuation of primary prophylaxis for some OI can be attempted without risk in patients experiencing a favourable response to treatment. However, data on the feasibility of discontinuing secondary prophylaxis are much more scarce, and restricted mainly to the withdrawal of maintenance treatment for cytomegalovirus (CMV) retinitis.

PATIENTS AND METHODS

Retrospective review of the clinical outcome at 18 months in HIV-infected patients in whom discontinuation of secondary prophylaxis, for different OI, was recommended 3 months after the introduction of HAART, if both CD4 counts > 100 x 10(6) CD4 lymphocytes/l and plasma HIV-RNA < 500 copies/ml had been achieved.

RESULTS

Fifty-three subjects were analysed. Secondary chemoprophylaxis was discontinued for the following OI: Pneumocystis carinii pneumonia (PCP) (n = 29), cerebral toxoplasmosis (n = 9), disseminated Mycobacterium avium complex infection (n = 7), CMV retinitis (n = 5), recurrent oroesophageal candidiasis (n = 5), Visceral leishmaniasis (n = 2), recurrent herpes zoster (n = 2), and chronic mucocutaneous herpes simplex infection (n = 1). In six individuals, OI prophylaxis was discontinued for two or more entities. Only two episodes of OI were recorded in these individuals during 18 months of follow-up. One developed tuberculous lymphadenitis despite having a good response to treatment, and another suffered a new episode of PCP after voluntary treatment interruption for 6 weeks.

CONCLUSION

Secondary prophylaxis for OI can be attempted without major risk in HIV-infected patients experiencing a favourable response to HAART. The benefit of this intervention should reduce costs, drug side-effects and pharmacologic interactions, and indirectly will improve patient's quality of life and adherence to antiretroviral treatment.