Asymptomatic Cerebrospinal Fluid HIV-1 Viral Blips and Viral Escape During Antiretroviral Therapy: A Longitudinal Study.

We examined longitudinal cerebrospinal fluid (CSF) samples (median, 5 samples/patients; interquartile range [IQR], 3-8 samples/patient) in 75 neurologically asymptomatic human immunodeficiency virus (HIV)-infected patients receiving antiretroviral therapy. Twenty-seven patients (36%) had ≥1 CSF HIV RNA load of >20 copies/mL (23% had ≥1 load of >50 copies/mL), with a median HIV RNA load of 50 copies/mL (IQR, 32-77 copies/mL). In plasma, 42 subjects (52%) and 22 subjects (29%) had an HIV RNA load of >20 and >50 copies/mL, respectively. Two subjects had an increasing virus load in consecutive CSF samples, representing possible CSF escape. Of 418 samples, 9% had a CSF HIV RNA load of >20 copies/mL (5% had a load of >50 copies/mL) and 19% had a plasma HIV RNA load of >20 copies/mL (8% had a load of >50 copies/mL). A CSF-associated virus load of >20 copies/mL was associated with higher CSF level of neopterin. In conclusion, CSF escape was rare, and increased CSF HIV RNA loads usually represented CSF virus load blips.

HIV-1 low copy viral sequencing-A prototype assay.

In HIV-1 patients with low viral burden, sequencing is often problematic, yet important. This study presents a sensitive, sub-type independent system for sequencing of low level viremia. Sequencing data from 32 HIV-1 infected patients with low level viremia were collected longitudinally. A combination of ViroSeq® HIV-1 Genotyping System and an in-house nesting protocol was used. Eight sub-types were represented. The success-rate of amplification of both PR and RT in the same sample was 100% in samples with viral loads above 100 copies/ml. Below 100 copies/ml, this study managed to amplify both regions in 7/13 (54%) samples. The assays were able to amplify either PR or RT in all sub-types included but one sub-type A specimen. In conclusion, this study presents a promising, simple assay to increase the ability to perform HIV-1 resistance testing at low level viremia. This is a prototype assay and the method needs further testing to evaluate clinical performance.

Risk of HIV transmission from patients on antiretroviral therapy: a position statement from the Public Health Agency of Sweden and the Swedish Reference Group for Antiviral Therapy.

The modern medical treatment of HIV with antiretroviral therapy (ART) has drastically reduced the morbidity and mortality in patients infected with this virus. ART has also been shown to reduce the transmission risk from individual patients as well as the spread of the infection at the population level. This position statement from the Public Health Agency of Sweden and the Swedish Reference Group for Antiviral Therapy is based on a workshop organized in the fall of 2012. It summarizes the latest research and knowledge on the risk of HIV transmission from patients on ART, with a focus on the risk of sexual transmission. The risk of transmission via shared injection equipment among intravenous drug users is also examined, as is the risk of mother-to-child transmission. Based on current knowledge, the risk of transmission through vaginal or anal intercourse involving the use of a condom has been judged to be minimal, provided that the person infected with HIV fulfils the criteria for effective ART. This probably also applies to unprotected intercourse, provided that no other sexually transmitted infections are present, although it is not currently possible to fully support this conclusion with direct scientific evidence. ART is judged to markedly reduce the risk of blood-borne transmission between people who share injection equipment. Finally, the risk of transmission from mother to child is very low, provided that ART is started well in advance of delivery.

Prophylaxis and treatment of HIV-1 infection in pregnancy: Swedish recommendations 2013.

Prophylaxis and treatment with antiretroviral drugs and elective caesarean section delivery have resulted in very low mother-to-child transmission of HIV during recent years. Updated general treatment guidelines and increasing knowledge about mother-to-child transmission have necessitated regular revisions of the recommendations for the prophylaxis and treatment of HIV-1 infection in pregnancy. The Swedish Reference Group for Antiviral Therapy (RAV) updated the recommendations from 2010 at an expert meeting on 11 September 2013. The most important revisions are the following: (1) ongoing efficient treatment at confirmed pregnancy may, with a few exceptions, be continued; (2) if treatment is initiated during pregnancy, the recommended first-line therapy is essentially the same as for non-pregnant women; (3) raltegravir may be added to achieve rapid reduction in HIV RNA; (4) vaginal delivery is recommended if at > 34 gestational weeks and HIV RNA is < 50 copies/ml and no obstetric contraindications exist; (5) if HIV RNA is < 50 copies/ml and delivery is at > 34 gestational weeks, intravenous zidovudine is not recommended regardless of the delivery mode; (6) if HIV RNA is > 50 copies/ml close to delivery, it is recommended that the mother should undergo a planned caesarean section, intravenous zidovudine, and oral nevirapine, and the infant should receive single-dose nevirapine at 48-72 h of age and post-exposure prophylaxis with 2 drugs; (7) if delivery is preterm at < 34 gestational weeks, a caesarean section delivery should if possible be performed, with intravenous zidovudine and oral nevirapine given to the mother, and single-dose nevirapine given to the infant at 48-72 h of age, as well as post-exposure prophylaxis with 2 additional drugs.

Antibody persistence 1 year after pandemic H1N1 2009 influenza vaccination and immunogenicity of subsequent seasonal influenza vaccine among adult organ transplant patients.

We investigated the antibody persistence in solid organ transplant (SOT) recipients 1 year after immunization with two doses of monovalent AS03-adjuvanted influenza A(H1N1)pdm09 vaccine. We also assessed the boosting effect of the seasonal trivalent inactivated vaccine 2010 (TIV/10) that contained the influenza A(H1N1)pdm09 strain. A total of 49 SOT recipients and 11 healthy controls were included. After a blood sample was obtained to assess the persistent immunity, one dose of TIV/10 was administered and another blood sample was collected 1 month after vaccination. A(H1N1)pdm09 antibodies were measured using a haemagglutination inhibition assay. The percentage of SOT recipients with protective titres decreased between 1 month and 10-14 months after the monovalent influenza A(H1N1)pdm09 vaccination, from 79% (n = 38) to 47% (n = 23) (P = 0.02). The corresponding numbers for the control group were 100% and 63%, respectively (P = 0.008). After the TIV/10 boosting dose, the number of SOT recipients with protective titres increased from 47% (n = 23) to 71% (n = 35) (P = 0.2). All the controls reached a protective titre level. The median titre rise was significantly higher among controls when compared to SOT recipients (P = 0.0036). No rejection or adverse events were seen. The results show an obvious need for vaccine boosting doses in the SOT patients.

Cerebrospinal fluid viral breakthrough in two HIV-infected subjects on darunavir/ritonavir monotherapy.

Darunavir/ritonavir monotherapy maintains HIV suppression in most patients who have achieved an undetectable viral load on combination antiretroviral treatment, and is increasingly used in the clinic. However, concerns have been raised about the effectiveness of ritonavir-boosted protease inhibitor (PI/r) monotherapy in the prevention of HIV replication in the central nervous system (CNS). Here we report the cases of 2 patients on darunavir/r maintenance monotherapy with cerebrospinal fluid viral breakthrough together with increased immunoactivation and biomarker signs of neuronal injury. These 2 cases raise concerns about the effectiveness of darunavir/ritonavir monotherapy in HIV CNS infection. Thus, we recommend caution with protease inhibitor monotherapy until CNS results have been obtained from clinical studies.

The antibody response to pandemic H1N1 2009 influenza vaccine in adult organ transplant patients.

Limited data are available regarding antibody response and the safety of the monovalent influenza A H1N1/09 vaccine for immunocompromised patients. In this study, the humoral response to this vaccine in solid organ transplant (SOT) recipients and healthy individuals was evaluated. Eighty-two SOT recipients and 28 healthy individuals received two doses of the influenza A H1N1/09 AS03 adjuvanted vaccine containing 3.75 mg of haemagglutinin at a 3- to 4-week interval. Serum samples were drawn at baseline and 3-4 weeks after the first and second vaccine doses. Seroprotective titres were measured with a haemagglutination inhibition. After the first dose seroprotective titres were observed in 69% of the SOT patients and in 96% of the healthy controls (P = 0.006), and increased after the second dose to 80% and 100%, respectively (P = 0.003). All controls and 77% of the SOT recipients achieved a ≥4-fold titre rise after the first immunisation (P = 0.005). The vaccine was well tolerated and no acute rejection was observed. Influenza A H1N1/09 vaccine elicited a protective antibody response in the majority of SOT recipients, but the response was lower when compared with controls. A second dose significantly improved vaccine immunogenicity in SOT recipients. (ClinicalTrials.gov number: NCT01254955).

Rebound of residual plasma viremia after initial decrease following addition of intravenous immunoglobulin to effective antiretroviral treatment of HIV.

BACKGROUND: High dosage of intravenous immunoglobulin (IVIG) has been observed as a possible activator of HIV gene expression in latently infected resting CD4+ T-cells, leading to a substantial decrease in both the reservoir and the residual plasma viremia when added to effective ART. IVIG treatment has also been reported to expand T regulatory cells (Tregs). The aim of this study was to evaluate possible long-term effect of IVIG treatment on residual viremia and T-lymphocyte activation. METHODS: Nine HIV-infected subjects on effective ART included in a previously reported study on IVIG treatment were evaluated 48-104 weeks after therapy. In addition, 14 HIV-infected controls on suppressive ART were included. HIV-1 RNA was analyzed in cell-free plasma by using an ultrasensitive PCR-method with a detection limit of 2 copies/mL. T-lymphocyte activation markers and serum interleukins were measured. RESULTS: Plasma residual viremia rebounded to pre-treatment levels, 48-104 weeks after the initial decrease that was observed following treatment with high-dosage IVIG. No long-term effect was observed regarding T-lymphocyte activation markers, T-regulatory cells or serum interleukins. In a post-hoc analysis, a correlation between plasma HIV-1-RNA and CD4+ T-cell count was found in both IVIG-treated patients and controls. CONCLUSIONS: These results indicate that the decrease in the latent HIV-1 pool observed during IVIG treatment is transient. Although not our primary objective, we found a correlation between HIV-1 RNA and CD4+ T-cell count suggesting the possibility that patients with a higher CD4+ T-cell count might harbor a larger residual pool of latently infected CD4+ T-cells.

HIV-1 viral escape in cerebrospinal fluid of subjects on suppressive antiretroviral treatment.

BACKGROUND: Occasional cases of viral escape in cerebrospinal fluid (CSF) despite suppression of plasma human immunodeficiency virus type 1 (HIV-1) RNA have been reported. We investigated CSF viral escape in subjects treated with commonly used antiretroviral therapy regimens in relation to intrathecal immune activation and central nervous system penetration effectiveness (CPE) rank. METHODS: Sixty-nine neurologically asymptomatic subjects treated with antiretroviral therapy >6 months and plasma HIV-1 RNA <50 copies/mL were cross-sectionally included in the analysis. Antiretroviral therapy regimens included efavirenz, lopinavir/ritonavir or atazanavir/ritonavir combined with tenofovir, abacavir, or zidovudine and emtricitabine or lamivudine. HIV-1 RNA was analyzed with real-time polymerase chain reaction assays. Neopterin was analyzed by enzyme-linked immunosorbent assay. RESULTS: Seven (10%) of the 69 subjects had detectable CSF HIV-1 RNA, in median 121 copies/mL (interquartile range, 54-213 copies/mL). Subjects with detectable CSF virus had significantly higher CSF neopterin and longer duration of treatment. Previous treatment interruptions were more common in subjects with CSF escape. Central nervous system penetration effectiveness rank was not a significant predictor of detectable CSF virus or CSF neopterin levels. CONCLUSIONS: Viral escape in CSF is more common than previously reported, suggesting that low-grade central nervous system infection may continue in treated patients. Although these findings need extension in longitudinal studies, they suggest the utility of monitoring CSF responses, as new treatment combinations and strategies modify clinical practice.

Treatment intensification has no effect on the HIV-1 central nervous system infection in patients on suppressive antiretroviral therapy.

BACKGROUND: Antiretroviral treatment (ART) significantly reduces cerebrospinal fluid (CSF) HIV-1 RNA levels and residual viremia is less frequently found in CSF than in blood. However, persistent intrathecal immunoactivation is common, even after several years of ART. To investigate whether low-level CSF viremia and residual immunoactivation within the central nervous system (CNS) derive from ongoing local viral replication, we conducted a study of treatment intensification in patients on effective ART. METHODS: Ten patients on ART with plasma HIV RNA <50 copies per milliliter for >18 months were included. Intensification was given for in total 8 weeks: 4 weeks with maraviroc or lopinavir/ritonavir (good CNS penetration), and 4 weeks with enfuvirtide (poor CNS penetration). Lumbar punctures were performed 4 weeks before, at intensification commencement, at switchover after 4 weeks, at the conclusion of, and 4 weeks after the intensification period. RESULTS: No significant changes in HIV RNA, neopterin, ß2-microglobulin, immunoglobulin G index, albumin ratio, and CD4(+) T-cell count were observed, either in CSF or blood, neither before, during, nor after the intensification periods. CONCLUSIONS: ART intensification did not reduce residual CSF HIV RNA levels or intrathecal immunoactivation in patients on ART. These findings do not support an ongoing viral replication in CNS.

Mode of coreceptor use by R5 HIV type 1 correlates with disease stage: a study of paired plasma and cerebrospinal fluid isolates.

Through the use of chimeric CXCR4/CCR5 receptors we have previously shown that CCR5-tropic (R5) HIV-1 isolates acquire a more flexible receptor use over time, and that this links to a reduced viral susceptibility to inhibition by the CCR5 ligand RANTES. These findings may have relevance with regards to the efficacy of antiretroviral compounds that target CCR5/virus interactions. Compartmentalized discrepancies in coreceptor use may occur, which could also affect the efficacy of these compounds at specific anatomical sites, such as within the CNS. In this cross-sectional study we have used wild-type CCR5 and CXCR4 as well as chimeric CXCR4/CCR5 receptors to characterize coreceptor use by paired plasma and cerebrospinal fluid (CSF) isolates from 28 HIV-1-infected individuals. Furthermore, selected R5 isolates, with varying chimeric receptor use, were tested for sensitivity to inhibition by the CCR5 antagonist TAK-779. Discordant CSF/plasma virus coreceptor use was found in 10/28 patients. Low CD4+ T cell counts correlated strongly with a more flexible mode of R5 virus CCR5 usage, as disclosed by an increased ability to utilize chimeric CXCR4/CCR5 receptors, specifically receptor FC-2. Importantly, an elevated ability to utilize chimeric receptors correlated with a reduced susceptibility to inhibition by TAK-779. Our findings show that a discordant CSF and plasma virus coreceptor use is not uncommon. Furthermore, we provide support for an emerging paradigm, where the acquisition of a more flexible mode of CCR5 usage is a key event in R5 virus pathogenesis. This may, in turn, negatively impact the efficacy of CCR5 antagonist treatment in late stage HIV-1 disease.

Treatment of HIV infection: Swedish recommendations 2009.

On 4 previous occasions, in 2002, 2003, 2005 and 2007, the Swedish Medical Products Agency (Läkemedelsverket) and the Swedish Reference Group for Antiviral Therapy (RAV) have jointly published recommendations for the treatment of HIV infection. In November 2008, an expert group under the guidance of RAV once more revised the guidelines, of which this is a translation into English. The most important updates in the present guidelines include the following: (a) treatment initiation is now recommended at a CD4 cell count of approximately 350/microl; (b) new recommendations for first-line therapy: abacavir/lamivudine or tenofovir/emtricitabine in combination with efavirenz or a boosted protease inhibitor (PI/r); (c) an increased focus on reducing the use of antiretroviral drugs that may cause lipoatrophy; (d) an emphasis on quality assurance of HIV care through the use of InfCare HIV; (e) considerably altered recommendations for the initiation of antiretroviral therapy in children. All infants (<1 y) should start antiretroviral therapy, regardless of immune status. Also, absolute CD4+ cell counts, rather than percentage, may be used to guide treatment initiation in children above the age of 5 y.

Reduction of the HIV-1 reservoir in resting CD4+ T-lymphocytes by high dosage intravenous immunoglobulin treatment: a proof-of-concept study.

BACKGROUND: The latency of HIV-1 in resting CD4+ T-lymphocytes constitutes a major obstacle for the eradication of virus in patients on antiretroviral therapy (ART). As yet, no approach to reduce this viral reservoir has proven effective. METHODS: Nine subjects on effective ART were included in the study and treated with high dosage intravenous immunoglobulin (IVIG) for five consecutive days. Seven of those had detectable levels of replication-competent virus in the latent reservoir and were thus possible to evaluate. Highly purified resting memory CD4+ T-cells were activated and cells containing replication-competent HIV-1 were quantified. HIV-1 from plasma and activated memory CD4+ T-cells were compared with single genome sequencing (SGS) of the gag region. T-lymphocyte activation markers and serum interleukins were measured. RESULTS: The latent HIV-1 pool decreased with in median 68% after IVIG was added to effective ART. The reservoir decreased in five, whereas no decrease was found in two subjects with detectable virus. Plasma HIV-1 RNA >or= 2 copies/mL was detected in five of seven subjects at baseline, but in only one at follow-up after 8-12 weeks. The decrease of the latent HIV-1 pool and the residual plasma viremia was preceded by a transitory low-level increase in plasma HIV-1 RNA and serum interleukin 7 (IL-7) levels, and followed by an expansion of T regulatory cells. The magnitude of the viral increase in plasma correlated to the size of the latent HIV-1 pool and SGS of the gag region showed that viral clones from plasma clustered together with virus from activated memory T-cells, pointing to the latent reservoir as the source of HIV-1 RNA in plasma. CONCLUSION: The findings from this uncontrolled proof-of-concept study suggest that the reservoir became accessible by IVIG treatment through activation of HIV-1 gene expression in latently-infected resting CD4+ T-cells. We propose that IVIG should be further evaluated as an adjuvant to effective ART.

Activity of the small modified amino acid alpha-hydroxy glycineamide on in vitro and in vivo human immunodeficiency virus type 1 capsid assembly and infectivity.

Upon maturation of the human immunodeficiency virus type 1 (HIV-1) virion, proteolytic cleavage of the Gag precursor protein by the viral protease is followed by morphological changes of the capsid protein p24, which will ultimately transform the virus core from an immature spherical to a mature conical structure. Virion infectivity is critically dependent on the optimal semistability of the capsid cone structure. We have reported earlier that glycineamide (G-NH(2)), when added to the culture medium of infected cells, inhibits HIV-1 replication and that HIV-1 particles with aberrant core structures were formed. Here we show that it is not G-NH(2) itself but a metabolite thereof, alpha-hydroxy-glycineamide (alpha-HGA), that is responsible for the antiviral activity. We show that alpha-HGA inhibits the replication of clinical HIV-1 isolates with acquired resistance to reverse transcriptase and protease inhibitors but has no effect on the replication of any of 10 different RNA and DNA viruses. alpha-HGA affected the ability of the HIV-1 capsid protein to assemble into tubular or core structures in vitro and in vivo, probably by binding to the hinge region between the N- and C-terminal domains of the HIV-1 capsid protein as indicated by matrix-assisted laser desorption ionization-mass spectrometry results. As an antiviral compound, alpha-HGA has an unusually simple structure, a pronounced antiviral specificity, and a novel mechanism of antiviral action. As such, it might prove to be a lead compound for a new class of anti-HIV substances.

Cerebrospinal fluid viral load and intrathecal immune activation in individuals infected with different HIV-1 genetic subtypes.

BACKGROUND: HIV-1 exhibits a high degree of genetic diversity and is presently divided into 3 distinct HIV-1 genetic groups designated major (M), non-M/non-O (N) and outlier (O). Group M, which currently comprises 9 subtypes (A-D, F-H, J and K), at least 34 circulating recombinant forms (CRFs) and several unique recombinant forms (URFs) is responsible for most of the HIV-1 epidemic. Most of the current knowledge of HIV-1 central nervous system (CNS) infection is based on subtype B. However, subtypes other than subtype B account for the majority of global HIV-1 infections. Therefore, we investigated whether subtypes have any influence on cerebrospinal fluid (CSF) markers of HIV-1 CNS infection. METHODOLOGY/PRINCIPAL FINDINGS: CSF HIV-1 RNA, CSF neopterin and CSF white blood cell (WBC) count were measured in patients infected with different HIV-1 subtypes. Using multivariate regression analysis, no differences in the CSF WBC count, neopterin and viral load were found between various HIV-1 subtypes. CONCLUSIONS: We did not find any subtype-dependent differences in the markers evaluated in this study.

Antiretroviral treatment of HIV infection: Swedish recommendations 2007.

On 3 previous occasions, in 2002, 2003 and 2005, the Swedish Medical Products Agency (Läkemedelsverket) and the Swedish Reference Group for Antiviral Therapy (RAV) have jointly published recommendations for the treatment of HIV infection. An expert group, under the guidance of RAV, has now revised the text again. Since the publication of the previous treatment recommendations, 1 new drug for the treatment of HIV has been approved - the protease inhibitor (PI) darunavir (Prezista). Furthermore, 3 new drugs have become available: the integrase inhibitor raltegravir (MK-0518), the CCR5-inhibitor maraviroc (Celsentri), both of which have novel mechanisms of action, and the non-nucleoside reverse transcriptase inhibitor (NNRTI) etravirine (TMC-125). The new guidelines differ from the previous ones in several respects. The most important of these are that abacavir is now preferred to tenofovir and zidovudine, as a first line drug in treatment-naïve patients, and that initiation of antiretroviral treatment is now recommended before the CD4 cell count falls below 250/microl, rather than 200/microl. Furthermore, recommendations on the treatment of HIV infection in children have been added to the document. As in the case of the previous publication, recommendations are evidence-graded in accordance with the Oxford Centre for Evidence Based Medicine, 2001 (see http://www.cebm.net/levels_of_evidence.asp#levels).

Cerebrospinal fluid viral loads reach less than 2 copies/ml in HIV-1-infected patients with effective antiretroviral therapy.

BACKGROUND: A low-grade persisting viraemia despite long-term treatment with highly active antiretroviral therapy (HAART) has previously been demonstrated in HIV-1-infected patients. Whether ongoing viral replication also could be detected in cerebrospinal fluid (CSF) in those circumstances has not been studied before. METHODS: Paired CSF and blood samples from 13 neurologically asymptomatic HIV-1-infected patients on stable HAART were analysed regarding HIV-1 RNA, by using a PCR assay with a detection limit of 2 copies/ml. RESULTS: All 13 patients had HIV-1 RNA < 2 copies/ml in CSF, compared with 8/13 in plasma. CONCLUSION: We could not demonstrate any persistent viral replication in the CSF of neurologically asymptomatic HIV-1-infected patients on effective HAART, rendering it unlikely that CSF acts as a viral reservoir in this category of patients.

Glycine-amide is an active metabolite of the antiretroviral tripeptide glycyl-prolyl-glycine-amide.

The chemically modified tripeptide glycyl-prolyl-glycine-amide (GPG-NH(2)) inhibits replication of human immunodeficiency virus (HIV) type 1 (HIV-1) in vitro, probably by interfering with capsid formation. The aim of the present study was to determine whether the metabolites glycyl-proline (GP-OH), glycine (G-OH), prolyl-glycine-amide (PG-NH(2)), proline (P-OH), and glycine-amide (G-NH(2)) from proteolytic cleavage may inhibit the replication of HIV-1 in vitro. PG-NH(2) has previously been shown to have a modest effect on HIV-1 replication. In the present study we show that G-NH(2) exhibits a pronounced inhibitory effect on HIV-1. This effect was not due to a decrease in cell proliferation or viability and could not be shown for herpes simplex virus type 1. The G-NH(2) concentration that inhibited virus replication by 50% (IC(50)) was equimolar to that of GPG-NH(2) and ranged from 3 to 41 microM. Transmission electron microscopy revealed that the effect of G-NH(2) on HIV-1 morphology was equivalent to that of GPG-NH(2) and showed disarranged capsid structures, indicating interference with capsid formation. Serial passage of HIV-infected cells with G-NH(2) for more than 20 subcultivations did not decrease the susceptibility to the compound. The results from this study suggest that GPG-NH(2) might act as a prodrug and that G-NH(2) is an active antiretroviral metabolite.

Cerebrospinal fluid viral load, virus isolation, and intrathecal immunoactivation in HIV type 2 infection.

Four patients with HIV-2 infection were followed longitudinally with cerebrospinal fluid (CSF) analyses. Two patients had positive CSF HIV-2 isolations. These two patients had CD4 cell count below 200 x 10(6)/liter and maximum CSF HIV-2 RNA viral loads above 4000 copies/ml. Intrathecal immune activation was demonstrated by elevated CSF neopterin concentrations (14-18 nmol/liter). No opportunistic infections were diagnosed. After antiretroviral treatment CSF viral counts decreased to below 125 copies/ml and CSF neopterin concentrations decreased. In two other patients who had CD4 counts within the normal range CSF virus isolations were repeatedly negative and viral CSF loads were below 125 copies/ml. However, a slightly elevated CSF neopterin concentration in one sample and pleocytosis in another might also be caused by HIV-2 in these patients. Before antiretroviral treatment HIV-2 isolations from blood were positive in all four patients. Maximum HIV-2 RNA viral loads were higher in blood than in CSF. Treatment failure in one patient with increasing viral loads in blood did not result in viral rebound in CSF.

Obligatory involvement of CD26/dipeptidyl peptidase IV in the activation of the antiretroviral tripeptide glycylprolylglycinamide (GPG-NH(2)).

GPG-NH2 and G-NH2 are highly selective antiretroviral agents in cell culture, and both compounds inhibit HIV replication in CEM cell cultures to an equal extent (50% effective concentration: approximately 30 microM). The lymphocyte surface glycoprotein marker CD26, which is identical to dipeptidyl peptidase IV, efficiently converted GPG-NH2 to G-NH2 releasing the dipeptide GP-OH. The closely related QPG-NH2 derivative was also inhibitory to HIV, presumably by the dipeptidyl peptidase IV (DPP IV)-catalyzed release of G-NH2. In contrast, the cyclic pQPG-NH2 derivative in which the glutamine at the amino terminal position of QPG-NH2 was replaced by pyroglutamine and which is resistant to cleavage by purified CD26, was devoid of antiviral activity. CD26 is abundantly expressed on a variety of HIV target cells and is also present in serum of bovine, murine and human origin. The CD26/DPP IV enzymatic activity in serum and in cell suspensions could be efficiently inhibited by the CD26/DPP IV inhibitor L-isoleucinepyrrolidine (IlePyr) with 50% inhibitory concentrations ranging between 20 and 100 microM. When combined in HIV-1-infected cell cultures, IlePyr and Diprotin A (DP-A), another CD26/DPP IV inhibitor, abrogated the antiviral activity of GPG-NH2 but not of G-NH2. Therefore, it was concluded that the anti-HIV drug GPG-NH2 is not active as such, but rather behaves as a prodrug that must be obligatorily cleaved by CD26/DPP IV to G-NH2 to exert its antiretroviral activity. This is the first demonstration of a lymphocyte activation/differentiation marker (i.e. CD26) that plays a direct regulatory and indispensable role in the eventual antiretroviral activity of small synthetic molecules such as the antiretroviral (pro)drug GPG-NH2.