Cell-free HIV-1 Research Articles

Proteasome-independent degradation of HIV-1 in naturally non-permissive human placental trophoblast cells

BackgroundThe human placenta-derived cell line BeWo has been demonstrated to be restrictive to cell-free HIV-1 infection. BeWo cells are however permissive to infection by VSV-G pseudotyped HIV-1, which enters cells by a receptor-independent mechanism, and to infection by HIV-1 via a cell-to-cell route.ResultsHere we analysed viral entry in wild type BeWo (CCR5+, CXCR4+) and BeWo-CD4+ (CD4+, CCR5+, CXCR4+) cells. We report that HIV-1 internalisation is not restricted in either cell line. Levels of internalised p24 antigen between VSV-G HIV-1 pseudotypes and R5 or X4 virions were comparable. We next analysed the fate of internalised virions; X4 and R5 HIV-1 virions were less stable over time in BeWo cells than VSV-G HIV-1 pseudotypes. We then investigated the role of the proteasome in restricting cell-free HIV-1 infection in BeWo cells using proteasome inhibitors. We observed an increase in the levels of VSV-G pseudotyped HIV-1 infection in proteasome-inhibitor treated cells, but the infection by R5-Env or X4-Env pseudotyped virions remains restricted.ConclusionCollectively these results suggest that cell-free HIV-1 infection encounters a surface block leading to a non-productive entry route, which either actively targets incoming virions for non-proteasomal degradation, and impedes their release into the cytoplasm, or causes the inactivation of mechanisms essential for viral replication.

Understanding Basic Mechanisms and Optimizing Assays to Evaluate the Efficacy of Vaginal Microbicides

The ideal microbicide or microbicide combination must have activity against cell-free and cell-associated primary HIV isolates representing multiple clades, must inhibit transmission to relevant cell types within the mucosa, and must retain activity in the presence of cervicovaginal fluid and when virus is introduced in semen or seminal plasma. This summary briefly reviews some of the basic concepts underlying the optimization of assays to evaluate the efficacy of candidate microbicides against HIV/STI. The review is based on the presentations of Drs. Stuart Turville (Population Council), Dan Barouch (Harvard University), Scott McCoombe (Northwestern University), Betsy Herold (Albert Einstein College of Medicine), Sam Niedbala (Lehigh University), and the subsequent discussion led by Drs. Robin Shattock (St. George's Hospital Medical School) and Jim Turpin (National Institutes of Health) during a session entitled "Biomarkers of HIV/STI" held at the conference entitled "Biomarkers for evaluation of vaginal microbicides and contraceptives: discovery and early validation," organized by CONRAD and the Alliance for Microbicide Development in November of 2006 as well as more recent published findings.

DC contact with HIV‐1‐infected cells leads to high levels of Env‐mediated virion endocytosis coupled with enhanced HIV‐1 Ag presentation

In HIV-infected patients, DC are likely to interact with both cell-free HIV and HIV-infected cells. We were interested in investigating the mechanism of virus transmission occurring upon contact between HIV-1-infected cells and DC, as well as the consequences for HIV-1 Ag-presenting activity. By comparing mixed co-cultures with trans-well cultures, we observed that cell-to-cell contact strongly increased HIV-1 Env-mediated virion endocytosis in target DC. This endocytosis was independent of HIV-1 tropism, de novo infection, HIV-1 Env-CD4-dependent fusion, and immature DC activation/maturation. We also found that augmentation of HIV-1 endocytosis was closely correlated with strong, Env-dependent HIV-1 Ag presentation by DC. Our results provide a better understanding of the mechanisms underlying the induction of the anti-HIV adaptive immune response.

Trichomonas Vaginalis Treatment Reduces Vaginal HIV-1 Shedding

Vaginal HIV-1 shedding has been associated with Trichomonas vaginalis (TV) infection and could play a role in HIV transmission. The purpose of the study was to examine if effective TV treatment reduces the presence of vaginal HIV-1 RNA. TV+ women attending an HIV outpatient clinic in New Orleans, LA, who resolved infection (n = 58) and TV-negative controls (n = 92), matched on antiretroviral therapy (ART) were examined and interviewed at baseline, 1, and 3 months. TV status was tested by culture and the amount of cell free HIV-1 RNA in the vaginal fluids was determined by the Amplicor HIV-1 Monitor ultrasensitive assay. : Most women (81.3%) were black and the mean age was 37.5 (SD 8.7). At baseline, 46.0% had plasma HIV-1 RNA >/=10,000 copies/mL, 26.4% had CD4<200 cells/muL, 54.7% were taking ART, and only 26.0% had detectable HIV-1 RNA in their vaginal fluids. TV-positive women who were effectively treated for TV were less likely to shed HIV vaginally at 3-months post-treatment compared to baseline (R.R. 0.34, 95% CI: 0.12-0.92, P = 0.03), whereas there was no change for TV-negative women. This study provides additional support that reducing TV infection among HIV-positive women may have an impact on the prevention of HIV transmission. Reasons for the delayed treatment effect and the effect on cervical shedding need further investigation.

RAG2 −/− γ c −/− Mice Transplanted with CD34 + Cells from Human Cord Blood Show Low Levels of Intestinal Engraftment and Are Resistant to Rectal Transmission of Human Immunodeficiency Virus

Rectal transmission is one of the main routes of infection by human immunodeficiency virus type 1 (HIV-1). To efficiently study transmission mechanisms and prevention strategies, a small animal model permissive for rectal transmission of HIV is mandatory. We tested the susceptibility of RAG2(-/-)gamma(c)(-/-) mice transplanted with human cord blood hematopoietic stem cells to rectal infection with HIV. We rectally exposed these humanized mice to cell-free and cell-associated HIV. All mice remained HIV negative as assessed by plasma viral load. The same mice infected intraperitoneally showed high levels of HIV replication. In the gut-associated lymphatic tissue, we found disproportionately smaller numbers of human cells than in other lymphoid organs. This finding may explain the observed resistance to rectal transmission of HIV. To increase the numbers of local HIV target cells and the likelihood of HIV transmission, we treated mice with different proinflammatory stimuli: local application of interleukin-1beta, addition of seminal plasma to the inoculum, or induction of colitis with dextran sodium sulfate. These procedures attracted some human leukocytes, but the transmission rate was still very low. The humanized mice showed low levels of human engraftment in the intestinal tract and seem to be resistant to rectal transmission of HIV, and thus they are an unsuitable model for this application.

Accumulation of activated CD4+ lymphocytes in the lung of individuals infected with HIV accompanied by increased virus production in patients with secondary infections.

The lung is continuously exposed to infectious and non-infectious agents causing cell activation. Activated cells in the lung such as antigen-presenting cells which harbour HIV may favour this organ as a site for virus production. To test this hypothesis, cells from blood and bronchoalveolar lavage (BAL) of HIV-infected patients and healthy controls were obtained and the activation of the cells were analysed by measuring the expression of IL-2 receptor, HLA-DR and VLA-1. The HIV-infected individuals were subdivided into 'lung symptomatic' or 'lung asymptomatic' patients, depending on the presence or absence of secondary lung diseases besides HIV. All HIV-infected individuals demonstrated a decreased number of CD4+ lymphocytes in blood; however, normal numbers of these cells were found in BAL. The activation state of CD4+ and CD8+ T lymphocytes in blood and BAL was higher in lymphocytes from HIV-infected patients compared with controls. The activation state was highest in the lung symptomatic group. Lung symptomatic patients and lung asymptomatic patients with extrapulmonary infections had increased levels of free virus in plasma. Four out of four individuals without or with only low amounts of cell-free HIV in plasma belonged to the symptom-free subgroup. These results suggest that microorganisms other than HIV may promote viral replication via antigen-driven accumulation and activation of CD4+ cells in the lung or other organs, and thus may be responsible for the loss of helper T cells and the progression of the disease.

Increased Levels of HIV-1-Infected Cells in Endocervical Secretions After the Luteinizing Hormone Surge

Levels of HIV-1 RNA in endocervical specimens fluctuate with the menstrual cycle, suggesting that cell-free HIV-1 levels may vary during the cycle, which could influence infectivity. Here, we examined daily changes in endocervical HIV-1-infected cells during 1 cycle. There were significant positive associations between the number of days from the luteinizing hormone surge and the number of HIV-1 DNA copies/swab (P = 0.001) and the number of total cells/swab (P < 0.001) in endocervical specimens. These data suggest that sampling of cell-associated endocervical HIV-1 increases after the periovulatory period, which could result in increased exposure to HIV-1-infected cells during sexual contact.

Development of a Comprehensive Human Immunodeficiency Virus Type 1 Screening Algorithm for Discovery and Preclinical Testing of Topical Microbicides

Topical microbicides are self-administered, prophylactic products for protection against sexually transmitted pathogens. A large number of compounds with known anti-human immunodeficiency virus type 1 (HIV-1) inhibitory activity have been proposed as candidate topical microbicides. To identify potential leads, an in vitro screening algorithm was developed to evaluate candidate microbicides in assays that assess inhibition of cell-associated and cell-free HIV-1 transmission, entry, and fusion. The algorithm advances compounds by evaluation in a series of defined assays that generate measurements of relative antiviral potency to determine advancement or failure. Initial testing consists of a dual determination of inhibitory activity in the CD4-dependent CCR5-tropic cell-associated transmission inhibition assay and in the CD4/CCR5-mediated HIV-1 entry assay. The activity is confirmed by repeat testing, and identified actives are advanced to secondary screens to determine their effect on transmission of CXCR4-tropic viruses in the presence or absence of CD4 and their ability to inhibit CXCR4- and CCR5-tropic envelope-mediated cell-to-cell fusion. In addition, confirmed active compounds are also evaluated in the presence of human seminal plasma, in assays incorporating a pH 4 to 7 transition, and for growth inhibition of relevant strains of lactobacilli. Leads may then be advanced for specialized testing, including determinations in human cervical explants and in peripheral blood mononuclear cells against primary HIV subtypes, combination testing with other inhibitors, and additional cytotoxicity assays. PRO 2000 and SPL7013 (the active component of VivaGel), two microbicide products currently being evaluated in human clinical trials, were tested in this in vitro algorithm and were shown to be highly active against CCR5- and CXCR4-tropic HIV-1 infection.

Photopheresis in HIV-1 Infected Patients Utilizing Benzoporphyrin Derivative (BPD) Verteporfin and Light

An ex vivo trial utilizing photopheresis with Benzoporphyrin Derivative as the photoactive compound, identified the minimum energy levels of light and concentrations of BPD that eradicated both cell-free and cell-associated HIV-1 infectivity without destroying the virus particles or infected leukocytes. Leukocytes remained viable with altered chemokine/cytokine expression. Apoptosis was induced in a minority of CD4 but not CD8 positive cells with a statistically significant increase in cytolytic T-cell activity. In the 24 week clinical trial in 7 HIV-1 infected patients, three who had rapidly rising viral loads prior to initiating therapy stabilized. Two had a sustained greater than 0.5 log decrement and 5 had stable plasma viral loads (less than a 0.5 log increment or decrement) with varied effects on absolute CD4 and CD8 positive lymphocytes counts. One achieved a greater than 1 log decrement in HIV-1 plasma viral load and undetectable in vivo cell-free and cell-associated HIV-1 infectivity with an increased in vitro lymphocyte mitogen stimulation index. Under amended protocol, 5 additional 12 month courses were administered to three additional patients and two of the previous enrollees. Area under the curve for viral load showed a significant decrease from pre- to post-therapy (p 0.007). No associated toxicities were observed.

Upregulation of HTLV‐1 and HTLV‐2 expression by HIV‐1 in vitro

Co-infections with HIV-1 and the human T leukemia virus types 1 and 2 (HTLV-1, HTLV-2) occur frequently, particularly in large metropolitan areas where injection drug use is a shared mode of transmission. Recent evidence suggests that HIV-HTLV co-infections are associated with upregulated HTLV-1/2 virus expression and disease. An in vitro model of HIV-1 and HTLV-1/2 co-infection was utilized to determine if cell free HIV-1 virions or recombinant HIV-1 Tat protein (200-1,000 ng/ml) upregulated HTLV-1/2 expression and infectivity. Exposure to HIV-1 increased the number of HTLV-1 antigen expressing cells, from 6% at baseline to 12% at 24 hr, and 20% at 120 hr (P < 0.05) post-exposure. A similar, although less robust response was observed in HTLV-2 infected cells. HIV-1 co-localized almost exclusively with HTLV-1/2 positive cells. Exposure to HIV-1 Tat protein (1,000 ng/ml) increased HTLV-1 p19 expression almost twofold by 48 hr, and cells co-stimulated with 10 nM phorbol myristate acetate (PMA) showed almost a fourfold increase over baseline. It is concluded that HIV-1 augments HTLV-1/2 infectivity in vitro. The findings also suggest a role for the HIV-1 Tat protein and PMA-inducible cellular factors, in HIV-1 induced HTLV-1/2 antigen expression.

Mucosal transmission of R5 and X4 tropic HIV-1 via vaginal and rectal routes in humanized Rag2 −/−γc −/− (RAG-hu) mice

Studies on HIV-1 mucosal transmission to evaluate early events in pathogenesis and the development of effective preventive/prophylactic methods have thus far been hampered by the lack of a suitable animal model susceptible to HIV-1 infection by either vaginal and/or rectal routes. In this regard, while primate-SIV/SHIV and cat-FIV models provided useful surrogate platforms to derive comparative data, these viruses are distinct and different from that of HIV-1. Therefore an optimal model that permits direct study of HIV-1 transmission via mucosal routes is highly desirable. The new generation of humanized NOD/SCID BLT, NOD/SCIDγc −/−, and Rag2 −/−γc −/− mouse models show great promise to achieve this goal. Here, we show that humanized Rag2 −/−γc −/− mice (RAG-hu) engrafted with CD34 hematopoietic progenitor cells harbor HIV-1-susceptible human cells in the rectal and vaginal mucosa and are susceptible to HIV-1 infection when exposed to cell-free HIV-1 either via vagina or rectum. Infection could be established without any prior hormonal conditioning or mucosal abrasion. Both R5 and X4 tropic viruses were capable of mucosal infection resulting in viremia and associated helper T cell depletion. There was systemic spread of the virus with infected cells detected in different organs including the intestinal mucosa. R5 virus was highly efficient in mucosal transmission by both routes whereas X4 virus was relatively less efficient in causing infection. HIV-1 infection of RAG-hu mice by vaginal and rectal routes as shown here represents the first in vivo model of HIV-1 transmission across intact mucosal barriers and as such may prove very useful for studying early events in HIV-1 pathogenesis in vivo, as well as the testing of microbicides, anti-HIV vaccines/therapeutics, and other novel strategies to prevent HIV-1 transmission.

Distinct efficacy of HIV-1 entry inhibitors to prevent cell-to-cell transfer of R5 and X4 viruses across a human placental trophoblast barrier in a reconstitution model in vitro

Background and methodsHIV-1 cell-to-cell transmission is more efficient than infection of permissive cells with cell-free particles. The potency of HIV-1 entry inhibitors to inhibit such transmission is not well known. Herein, we evaluated the efficacy of this new class of antiretrovirals to block cell-to-cell transmission of HIV-1 in a model of reconstitution of the human placental trophoblast barrier in vitro.ResultsOur data show that CCR5 antagonists and T20 inhibit the passage of the virus across the BeWo cell monolayer in contact with PBMCs infected with an R5 (Ba-L) and a dualtropic (A204) HIV-1 with IC50s in the range of 100 – 5,000 nM for TAK779; 90 to 15,000 nM for SCH-350581 and 3,000 to 20,000 nM for T20. The CXCR4 antagonist AMD3100 is also effective against X4 HIV-1 infected PBMCs in our model with IC50 comprised between 4 nM and 640 nM. HIV-1 entry inhibitors are less efficient to block cell-to-cell virus transmission than cell-free HIV-1 infection of PBMCs and CCR5 antagonists do not prevent PBMC infection by dual tropic HIV-1 in contrast to cell-to-cell infection in our model.Surprisingly, T20 (and C34) do not block cell-to-cell transmission of X4 HIV-1 but, rather, increase 80 to 140 fold, compared to control without drug, the passage of the virus across the trophoblast barrier. Additional experiments suggest that the effect of T20 on BeWo/PBMC-X4 HIV-1 is due to an increase of effector-target cells fusion.ConclusionOur results support further evaluation of HIV-1 coreceptor antagonists, alone or combined to other antiretrovirals, in a perspective of prevention but warn on the use of T20 in patients bearing X4 HIV-1 at risk of transmission.

Deactivation of Human Immunodeficiency Virus Type 1 in Medium by Copper Oxide-Containing Filters

Human immunodeficiency virus type 1 (HIV-1) can be transmitted through breast-feeding and through contaminated blood donations. Copper has potent biocidal properties and has been found to inactivate HIV-1 infectivity. The objective of this study was to determine the capacity of copper-based filters to inactivate HIV-1 in culture media. Medium spiked with high titers of HIV-1 was exposed to copper oxide powder or copper oxide-impregnated fibers or passed through copper-based filters, and the infectious viral titers before and after treatment were determined. Cell-free and cell-associated HIV-1 infectivity was inhibited when exposed to copper oxide in a dose-dependent manner, without cytotoxicity at the active antiviral copper concentrations. Similar dose-dependent inhibition occurred when HIV-1 was exposed to copper-impregnated fibers. Filtration of HIV-1 through filters containing the copper powder or copper-impregnated fibers resulted in viral deactivation of all 12 wild-type or drug-resistant laboratory or clinical, macrophage-tropic and T-cell-tropic, clade A, B, or C, HIV-1 isolates tested. Viral inactivation was not strain specific. Thus, a novel means to inactivate HIV-1 in medium has been developed. This inexpensive methodology may significantly reduce HIV-1 transmission from "mother to child" and/or through blood donations if proven to be effective in breast milk or plasma and safe for use. The successful application of this technology may impact HIV-1 transmission, especially in developing countries where HIV-1 is rampant.

Photopheresis in HIV-1 Infected Patients Utilizing (Benzoporphyrin Derivative Verteporfin/BPD-MA) and Light.

An ex vivo trial utilizing photopheresis with Benzoporphyrin Derivative as the photoactive compound, identified the minimum energy levels of light and concentrations of BPD that eradicated both cell-free and cell-associated HIV-1 infectivity without destroying the virus particles or infected leukocytes. Leukocytes remained viable with altered chemokine/cytokine expression. Apoptosis was induced in a minority of CD4 but not CD8 positive cells with a statistically significant increase in cytolytic T-cell activity. In the 24 week clinical trial in seven HIV-1 infected patients. Three who had rapidly rising viral loads prior to initiating therapy stabilized. Two had a (sustained) greater than .5 log decrement and 5 had stable plasma viral loads (less than a .5 log increment or decrement) with varied effects on absolute CD4 and CD8 positive lymphocytes counts. One achieved a greater than 1 log decrement in HIV-1 plasma viral load and undetectable in vivo cell-free and cell-associated HIV-1 infectivity with an increased in vitro lymphocyte mitogen stimulation index. Under amended protocol 5 additional 12 month courses were administered to three additional patients and two of the previous enrollees. Area under the curve for viral load showed a significant decrease from pre to post therapy (p 0.007). No associated toxicities observed.

Inhibition of HIV-1 infectivity and epithelial cell transfer by human monoclonal IgG and IgA antibodies carrying the b12 V region.

Both IgG and secretory IgA Abs in mucosal secretions have been implicated in blocking the earliest events in HIV-1 transit across epithelial barriers, although the mechanisms by which this occurs remain largely unknown. In this study, we report the production and characterization of a human rIgA(2) mAb that carries the V regions of IgG1 b12, a potent and broadly neutralizing anti-gp120 Ab which has been shown to protect macaques against vaginal simian/HIV challenge. Monomeric, dimeric, polymeric, and secretory IgA(2) derivatives of b12 reacted with gp120 and neutralized CCR5- and CXCR4-tropic strains of HIV-1 in vitro. With respect to the protective effects of these Abs at mucosal surfaces, we demonstrated that IgG1 b12 and IgA(2) b12 inhibited the transfer of cell-free HIV-1 from ME-180 cells, a human cervical epithelial cell line, as well as Caco-2 cells, a human colonic epithelial cell line, to human PBMCs. Inhibition of viral transfer was due to the ability of b12 to block both viral attachment to and uptake by epithelial cells. These data demonstrate that IgG and IgA MAbs directed against a highly conserved epitope on gp120 can interfere with the earliest steps in HIV-1 transmission across mucosal surfaces, and reveal a possible mechanism by which b12 protects the vaginal mucosal against viral challenge in vivo.

Proliferative activation up‐regulates expression of CD4 and HIV‐1 co‐receptors on NK cells and induces their infection with HIV‐1

NK cells play important roles in immune surveillance against malignancy and virus-infected cells. NK cell functions are affected in patients infected with HIV-1; however, whether there is direct interaction between NK cells and HIV-1 remains controversial. In this study the expression of CD4, an important receptor for HIV-1, was up-regulated on NK cells co-cultured with an NK cell-selective stimulating cell line, HFWT, and rIL-2. Although the level of CD4 was lower on NK cells than on CD4+ T cells, expression of the HIV-1 co-receptor CCR5 was clearly up-regulated on CD4+ NK cells. CD4+ NK cells expressed higher levels of HLA-DR and CD25 than CD4- NK cells, suggesting that they were highly activated. Cell-free HIV-1 could not infect the NK cells, but NK cells were infected when co-cultured with HIV-1-infected T cells. Using this co-culture system, we can better understand how HIV-1 infects NK cells and how NK cell functions are affected in AIDS.

Flash-Heat Inactivation of HIV-1 in Human Milk

Up to 40% of all mother-to-child transmission of HIV occurs by means of breast-feeding; yet, in developing countries, infant formula may not be a safe option. The World Health Organization recommends heat-treated breast milk as an infant-feeding alternative. We investigated the ability of a simple method, flash-heat, to inactivate HIV in breast milk from HIV-positive mothers. Ninety-eight breast milk samples, collected from 84 HIV-positive mothers in a periurban settlement in South Africa, were aliquoted to unheated control and flash-heating. Reverse transcriptase (RT) assays (lower detection limit of 400 HIV copies/mL) were performed to differentiate active versus inactivated cell-free HIV in unheated and flash-heated samples. We found detectable HIV in breast milk samples from 31% (26 of 84) of mothers. After adjusting for covariates, multivariate logistic regression showed a statistically significant negative association between detectable virus in breast milk and maternal CD4+ T-lymphocyte count (P=0.045) and volume of breast milk expressed (P=0.01) and a positive association with use of multivitamins (P=0.03). All flash-heated samples showed undetectable levels of cell-free HIV-1 as detected by the RT assay (P<0.00001). Flash-heat can inactivate HIV in naturally infected breast milk from HIV-positive women. Field studies are urgently needed to determine the feasibility of in-home flash-heating breast milk to improve infant health while reducing postnatal transmission of HIV in developing countries.

In VitroPre- and Post-Exposure Prophylaxis Using HIV Inhibitors as Microbicides Against Cell-Free or Cell-Associated HIV-1 Infection

Several classes of microbicides are being evaluated for the prevention of sexual HIV transmission. In vivo, the infectious dose and viral source involved in transmission remain uncertain and it is likely that women will use microbicides both before and after high-risk HIV exposure. Therefore, we evaluated HIV entry inhibitors (EIs) and reverse transcriptase inhibitors (RTIs) for their ability to block cell-free and cell-associated HIV-1 infection in co-cultures of monocyte-derived dendritic cells (MO-DC) and CD4+ T-cells using settings of pre- and post-exposure prophylaxis. In the pre-exposure assay, where compound was present before, during and 24 h after infection, all tested EIs (BMS806, TAK779 and T20) and RTIs (PMPA, TMC120 and UC781) blocked infection with 10(-4) multiplicity of infection (MOI) of cell-free virus at a dose between 100 and 10,000 nM, dependent on the compound used. At 10(-3) MOI, however, only T20 and the RTIs completely blocked infection. Furthermore, in experiments with cell-associated virus, EIs were ineffective, whereas RTIs actively blocked infection with similar potency as in the experiments with cell-free virus. In the post-exposure assay, where compound was added 2 h after infection and remained present for 24 h, EIs were inactive whereas RTIs blocked cell-free and cell-associated viral infections equally efficiently. Moreover, post-exposure prophylaxis initiated 24 h after infection with cell-free or cell-associated HIV-1 was still effective with 1,000 nM of TMC120. Both EIs and RTIs were non-cytotoxic at any tested concentration for MO-DC and CD4+ T-cells in co-culture. Our study shows that RTIs are potent inhibitors of cell-free and cell-associated virus used either in pre- or post-exposure settings. It highlights that parameters such as viral input, viral source, the time of compound addition and the target cells should be considered in microbicides evaluation.

RNase H-mediated retrovirus destruction in vivo triggered by oligodeoxynucleotides

The HIV-1 RNase H can be prematurely activated by oligodeoxynucleotides targeting the highly conserved polypurine tract required for second strand DNA synthesis. This inhibits retroviral replication in cell-free HIV particles and newly infected cells. Here we extend these studies to an in vivo model of retroviral replication. Mice that are chronically infected with the spleen focus-forming virus and treated with oligodeoxynucleotides that target the polypurine tract, exhibit either transient or long-term reductions in plasma virus titer, depending on the therapeutic regimen. Treatment prior to, during or shortly after infection can delay disease progression, increase survival rates and prevent viral infection. This strategy destroys viral RNA template in virus particles in serum as well as early retroviral replication intermediates in infected cells. As it targets events common to the replication cycle of all retroviruses, this approach may be broadly applicable to retroviruses of medical and agricultural importance.

Antiretroviral Therapy Among HIV-Infected Breastfeeding Mothers: A Promising Strategy to Prevent HIV Postnatal Transmission in Africa

Evaluation of: Giuliano M, Guidotti G, Andreotti M et al.: Triple antiretroviral prophylaxis administered during pregnancy and after delivery significantly reduces breast milk viral load: a study within the Drug Resource Enhancement Against AIDS and Malnutrition Program. J. Acquir. Immune Defic. Syndr. 44(3), 286–291 (2007). Maternal highly active antiretroviral therapy (HAART) starting during the late prenatal period and prolonged during lactation is a potentially interesting strategy to prevent mother-to-child transmission of HIV through breastfeeding in Africa. In this report, Giuliano and colleagues demonstrated that HIV-infected women treated with HAART from before delivery had lower cell-free HIV RNA load in breast milk and were less likely to have a detectable viral load in this compartment 1 week after delivery, when compared with untreated women. Antiretroviral therapy among HIV-infected breastfeeding mothers could thus be a promising strategy to prevent HIV transmission through breast milk in Africa if further larger studies confirm its safety. This strategy could also provide a link between prevention and care, since maternal HAART provided in pregnancy and during the breastfeeding period can be thereafter continued among women who meet the criteria for their own health.