Phase I/II trial of HIV-1 hyperimmune globulin for the prevention of HIV-1 vertical transmission in Uganda

Complement-Opsonized HIV Modulates Pathways Involved in Infection of Cervical Mucosal Tissues: A Transcriptomic and Proteomic Study

Genital mucosal transmission is the most common route of HIV spread. The initial responses triggered at the site of viral entry are reportedly affected by host factors, especially complement components present at the site, and this will have profound consequences on the outcome and pathogenesis of HIV infection. We studied the initial events associated with host-pathogen interactions by exposing cervical biopsies to free or complement-opsonized HIV. Opsonization resulted in higher rates of HIV acquisition/infection in mucosal tissues and emigrating dendritic cells. Transcriptomic and proteomic data showed a significantly more pathways and higher expression of genes and proteins associated with viral replication and pathways involved in different aspects of viral infection including interferon signaling, cytokine profile and dendritic cell maturation for the opsonized HIV. Moreover, the proteomics data indicate a general suppression by the HIV exposure. This clearly suggests that HIV opsonization alters the initial signaling pathways in the cervical mucosa in a manner that promotes viral establishment and infection. Our findings provide a foundation for further studies of the role these early HIV induced events play in HIV pathogenesis.

Antibody-dependent cellular cytotoxicity in HIV infection

: Interactions between the Fc segment of IgG and its receptors (FcγRs) found on cells such as natural killer cells, monocytes, macrophages and neutrophils can potentially mediate antiviral effects in the setting of HIV and related infections. We review the potential role of FcγR interactions in HIV, SIV and SHIV infections, with an emphasis on antibody-dependent cellular cytotoxicity (ADCC). Notably, these viruses employ various strategies, including CD4 down-regulation and BST-2/tetherin antagonism to limit the effect of ADCC. Although correlative data suggest that ADCC participates in both protection and control of established infection, there is little direct evidence in support of either role. Direct evidence does, however, implicate an FcγR-dependent function in augmenting the beneficial in vivo activity of neutralizing antibodies.

Use of broadly neutralizing antibodies for HIV-1 prevention

Antibodies have a long history in antiviral therapy, but until recently, they have not been actively pursued for HIV-1 due to modest potency and breadth of early human monoclonal antibodies (MAbs) and perceived insurmountable technical, financial, and logistical hurdles. Recent advances in the identification and characterization of MAbs with the ability to potently neutralize diverse HIV-1 isolates have reinvigorated discussion and testing of these products in humans, since new broadly neutralizing MAbs (bnMAbs) are more likely to be effective against worldwide strains of HIV-1. In animal models, there is abundant evidence that bnMAbs can block infection in a dose-dependent manner, and the more potent bnMAbs will allow clinical testing at infusion doses that are practically achievable. Moreover, recent advances in antibody engineering are providing further improvements in MAb potency, breadth, and half-life. This review summarizes the current state of the field of bnMAb protection in animal models as well as a review of variables that are critical for antiviral activity. Several bnMAbs are currently in clinical testing, and we offer perspectives on their use as pre-exposure prophylaxis (PrEP), potential benefits beyond sterilizing immunity, and a discussion of future approaches to engineer novel molecules.

Early weaning of HIV-exposed uninfected infants and risk of serious gastroenteritis: Findings from two perinatal HIV prevention trials in Kampala, Uganda

Objective: To assess serious gastroenteritis risk and mortality associated with early cessation of breastfeeding in infants enrolled in 2 prevention of maternal-to-child HIV-transmission trials in Uganda.Methods: We used hazard rates to evaluate serious gastroenteritis events by month of age and mortality among HIV-exposed uninfected infants enrolled in the HIV Network for Prevention Trials (HIVNET 012) (1997–2001) and HIV hyperimmune globulin (HIVIGLOB)/nevirapine (NVP) (2004–2007) trials. HIV-infected mothers were counseled using local infant feeding guidelines current at the time.Results: Breastfeeding cessation occurred earlier in HIVIGLOB/NVP compared with HIVNET 012 (median 4.0 versus 9.3 months,P,0.001). Rates of serious gastroenteritis were higher in HIVIGLOB/NVP (8.0/1000 child-months) than in HIVNET 012 (3.1/1000 child-months; P , 0.001). Serious gastroenteritis events also peaked earlier at 3–4 and 7–8 months (16.2/1000 and 15.0/1000 child-months,respectively) compared with HIVNET 012 at 9–10 months (20.8/1000 child-months). All cause infant mortality did not statistically differ between the HIVIGLOB/NVP and the HIVNET 012 trials [3.2/1000 versus 2.0/1000 child-months, respectively (P = 0.10)].Conclusions: Early breastfeeding cessation seen in the HIVIGLOB/NVP trial was associated with increased risk of serious gastroenteritis among HIV-exposed uninfected infants when compared with later breastfeeding cessation in the HIVNET 012 trial.Testing interventions, which could decrease HIV transmission through breastfeeding and allow safe

Development of human monoclonal antibodies against diseases caused by emerging and biodefense-related viruses

Polyclonal antibodies have a century-old history of being effective against some viruses; recently, monoclonal antibodies (mAbs) have also shown success. The humanized mAb Synagis (palivizumab), which is still the only mAb against a viral disease approved by the US FDA, has been widely used as a prophylactic measure against respiratory syncytial virus infections in neonates and immunocompromised individuals. The first fully human mAbs against two other paramyxoviruses, Hendra and Nipah virus, which can cause high (up to 75%) mortality, were recently developed; one of them, m101, showed exceptional potency against infectious virus. In an amazing pace of research, several potent human mAbs targeting the severe acute respiratory syndrome coronavirus S glycoprotein that can affect infections in animal models have been developed months after the virus was identified in 2003. A potent humanized mAb with therapeutic potential was recently developed against the West Nile virus. The progress in developing neutralizing human mAbs against Ebola, Crimean-Congo hemorrhagic fever, vaccinia and other emerging and biodefense-related viruses is slow. A major problem in the development of effective therapeutic agents against viruses, including therapeutic antibodies, is the viruses' heterogeneity and mutability. A related problem is the low binding affinity of crossreactive antibodies able to neutralize a variety of primary isolates. Combinations of mAbs or mAbs with other drugs, and/or the identification of potent new mAbs and their derivatives that target highly conserved viral structures, which are critical for virus entry into cells, are some of the possible solutions to these problems, and will continue to be a major focus of antiviral research.

HIV-1 autologous antibody neutralization associates with mother to child transmission

The HIV-1 characteristics associated with mother to child transmission (MTCT) are still poorly understood and if known would indicate where intervention strategies should be targeted. In contrast to horizontally infected individuals, exposed infants possess inherited antibodies (Abs) from their mother with the potential to protect against infection. We investigated the HIV-1 gp160 envelope proteins from seven transmitting mothers (TM) whose children were infected either during gestation or soon after delivery and from four non-transmitting mothers (NTM) with similar viral loads and CD4 counts. Using pseudo-typed viruses we tested gp160 envelope glycoproteins for TZM-bl infectivity, CD4 and CCR5 interactions, DC-SIGN capture and transfer and neutralization with an array of common neutralizing Abs (NAbs) (2F5, 2G12, 4E10 and b12) as well as mother and infant plasma. We found no viral correlates associated with HIV-1 MTCT nor did we find differences in neutralization with the panel of NAbs. We did, however, find that TM possessed significantly higher plasma neutralization capacities than NTM (P = 0.002). Furthermore, we found that in utero (IU) TM had a higher neutralization capacity than mothers transmitting either peri-partum (PP) or via breastfeeding (BF) (P = 0.002). Plasma from children infected IU neutralized viruses carrying autologous gp160 viral envelopes as well as those from their corresponding mothers whilst plasma from children infected PP and/or BF demonstrated poor neutralizing capacity. Our results demonstrate heightened autologous NAb responses against gp120/gp41 can associate with a greater risk of HIV-1 MTCT and more specifically in those infants infected IU. Although the number of HIV-1 transmitting pairs is low our results indicate that autologous NAb responses in mothers and infants do not protect against MTCT and may in fact be detrimental when considering IU HIV-1 transmissions.

Immunology of infants through adolescents: responses to emulate for HIV vaccines

PURPOSE OF REVIEW

The major target groups for an HIV vaccine include breastfeeding infants and adolescents. Differential immune maturity in these age groups may significantly impact vaccine efficacy, and should be taken into account when developing vaccines. Here we review these differences, with an emphasis on the immune response to vaccines for HIV and other pathogens. Recommendations for potential adaptation of current HIV vaccines are also made.

RECENT FINDINGS

An effective neonatal vaccine needs to be immunogenic in the presence of maternal antibody, and must induce cytotoxic T-lymphocyte responses, neutralizing antibody responses, both systemic and mucosal. There is renewed hope in the possibility of stimulating neutralizing antibodies with HIV vaccination. DNA vaccines are promising for neonates, but will need appropriate boosting. Certain adjuvants and vector delivery systems are more suitable for neonates. Adolescents may have stronger immune responses to HIV vaccines than adults, and will also require induction of mucosal neutralizing humoral and cellular immunity.

SUMMARY

Some current HIV vaccine strategies may need adaptation for neonates and suitable product development should be accelerated. Vaccines could induce better responses in adolescents and therefore should not be discarded prematurely. Development of vaccines that have potential for these age groups is an urgent global priority.

Safety and efficacy of HIV hyperimmune globulin for prevention of mother-to-child HIV transmission in HIV-1-infected pregnant women and their infants in Kampala, Uganda (HIVIGLOB/NVP STUDY)

BACKGROUND

This phase III, randomized, clinical trial compared single-dose nevirapine (sdNVP) plus HIV hyperimmune globulin (HIVIGLOB) with sdNVP alone for preventing maternal-to-child transmission of HIV. Primary objectives were to determine rates of HIV infection among infants and to assess the safety of HIVIGLOB in combination with sdNVP in HIV-infected Ugandan pregnant women and their infants.

METHODS

Mother-infant pairs were randomized to receive 200 mg of nevirapine to women in labor and 2 mg/kg NVP to newborns within 72 hours after birth (sdNVP arm) or to receive sdNVP plus a single intravenous 240-mL dose of HIVIGLOB given to women at 36- to 38-week gestation and a single intravenous 24-mL dose to newborns within 18 hours of birth (HIVIGLOB/sdNVP arm). Risk of HIV infection was determined using Kaplan-Meier and risk ratio estimates at birth, 2, 6, 14 weeks, 6, and 12 months of age.

RESULTS

Intent-to-treat analysis included 198 HIVIGLOB/sdNVP and 294 sdNVP mother-infant pairs. At 6 months of age, the primary endpoint, there was no statistically significant difference in HIV transmission in the HIVIGLOB/sdNVP arm vs. the sdNVP arm [18.7% vs. 15.0%; risk ratio = 1.240 (95% confidence interval: 0.833 to 1.846); P = 0.290]. Similarly, the proportion of serious adverse events in the HIVIGLOB/sdNVP and sdNVP arms, respectively, for mothers (18.9% vs. 19.3%; P = 0.91) and infants (62.6% vs. 59.5%; P = 0.51) was not significantly different.

CONCLUSIONS

Giving mother-infant pairs an infusion of peripartum HIV hyperimmune globulin in addition to sdNVP for preventing maternal-to-child transmission was as safe as sdNVP alone but was no more effective than sdNVP alone in preventing HIV transmission.

NK cell function and antibodies mediating ADCC in HIV-1-infected viremic and controller patients

Natural killer (NK) cells have been suggested to play a protective role in HIV disease progression. One potent effector mechanism of NK cells is antibody-dependent cellular cytotoxicity (ADCC) mediated by antiviral antibodies binding to the FcγRIIIa receptor (CD16) on NK cells. We investigated NK cell-mediated ADCC function and the presence of ADCC antibodies in plasma from 20 HIV-1-infected patients and 10 healthy donors. The HIV-positive patients were divided into two groups: six who controlled viremia for at least 8 y without treatment (controllers), and 14 who were persistently viremic and not currently on treatment. Plasma from both patient groups induced NK cell IFN-γ expression and degranulation in response to HIV-1 envelope (Env) gp140-protein-coated cells. Patient antibodies mediating ADCC were largely directed towards the Env V3 loop, as identified by a gp140 protein lacking the V3 loop. Interestingly, in two controllers ADCC-mediating antibodies were more broadly directed to other parts of Env. A high viral load in patients correlated with decreased ADCC-mediated cytolysis of gp140-protein-coated target cells. NK cells from both infected patients and healthy donors degranulated efficiently in the presence of antibody-coated HIV-1-infected Jurkat cells. In conclusion, the character of ADCC-mediating antibodies differed in some controllers compared to viremic patients. NK cell ADCC activity is not compromised in HIV-infected patients.

Complement opsonization of HIV-1 enhances the uptake by dendritic cells and involves the endocytic lectin and integrin receptor families

Interaction with the complement system is an underappreciated aspect of HIV-1 infection; even in primary infection, complement fragments are found on virions with potential to affect the interplay between the virus and dendritic cells (DC). Since opsonization may affect the efficiency of uptake and the type of receptors utilized, we compared the interactions of DC with free HIV-1 (F-HIV) and complement opsonized HIV-1 (C-HIV). We demonstrate that C-HIV significantly enhanced the uptake by immature DC (IDC) and mature DC (MDC) and that the internalization rate was dependent on both opsonization of the virus and DC maturation state. Increased DC uptake of C-HIV was not due to opsonization related increased binding of virus to the surface of DC but rather increased internalization of C-HIV despite utilizing a similar repertoire of receptors as F-HIV. Both F-HIV and C-HIV interacted with C-type lectins, integrins, and CD4 and blocking these receptor families prevented HIV-1 from binding to DC at 4°C. Blocking integrins significantly reduced the binding and uptake of F-HIV and C-HIV implicating the involvement of several integrins such as β1-integrin, CR3, LFA-1, and α4β7. Distinctive for C-HIV was usage of β1-integrin and for F-HIV, usage of β7-integrin, whereas both F-HIV and C-HIV utilized both integrin chains of CR3. We have in this study identified the receptor types used by both F-HIV and C-HIV to bind to DC. Noteworthy, C-HIV was internalized more efficiently by DC than F-HIV, probably via receptor mediated endocytosis, which may entail different intracellular processing of the virus leading to both elevated infection and altered activation of HIV specific immune responses.

HIV-1 and breastfeeding: biology of transmission and advances in prevention

Breastfeeding accounts for about 40% of mother-to-child transmission of HIV-1 worldwide and carries an estimated risk of transmission of 0.9% per month after the first month of breastfeeding. It is recommended that HIV-1-infected women completely avoid breastfeeding in settings where safe feeding alternatives exist. However, as replacement feeding is not safely available in many parts of the world, and because breastfeeding provides optimal nutrition and protection against other infant infections, there is intense ongoing research to make breastfeeding safe for HIV-1-infected mothers in resource-limited settings. More research is needed to determine the optimal duration of breastfeeding, optimal weaning practices, and which individual antiretroviral prophylactic regimen is best for HIV-1-infected mothers and their infants in a particular setting.

Modeling vertical transmission of HIV: imperfect vaccines can be of benefit

Reducing mother to child transmission (MTCT) of HIV in resource poor countries continues to be a major challenge. Here, we construct a hazard model to assess the effectiveness of combinations of HIV vaccine, Nevirapine (NVP), and HIV-specific monoclonal antibody (HIVAB) in reducing MTCT of HIV during the intrapartum and breastfeeding periods. The model shows that an intervention that uses three doses of vaccine with 30% initial immunity and 30% boost effect with subsequent doses (giving rise to maximum immunity approximately 66% with 3 doses) could reduce MTCT to 7.7% when used with NVP and to 5.9% when used with NVP and HIVAB. Using a vaccine with 50% initial immunity and 50% boost can reduce the rate to 4.3%. These results indicate that even an imperfect vaccine, when used in combination with other therapies, can be of considerable benefit in preventing MTCT in resource poor countries.

Potent human monoclonal antibodies against SARS CoV, Nipah and Hendra viruses

BACKGROUND

Recently, several potently neutralizing fully human monoclonal antibodies (hmAbs) targeting the severe acute respiratory syndrome-associated coronavirus (SARS CoV) S glycoprotein, and the G glycoprotein of the paramyxoviruses Hendra virus (HeV) and Nipah virus (NiV) have been discovered [corrected].

OBJECTIVE

To examine, compare and contrast the functional characteristics of hmAbs with the potential for prophylaxis and treatment of diseases caused by SARS CoV, HeV and NiV.

METHODS

A review of relevant literature.

RESULTS/CONCLUSIONS

Structural, functional and biochemical analyses [corrected] have provided insights into the molecular mechanisms of receptor recognition and antibody neutralization, and suggested that these antibodies alone or in combination could fight the viruses' heterogeneity and mutability, which is a major problem in the development of effective therapeutic agents against viruses, including therapeutic antibodies.

Therapeutic antibodies: current state and future trends--is a paradigm change coming soon?

Antibody-based therapeutics currently enjoy unprecedented success, growth in research and revenues, and recognition of their potential. It appears that the promise of the "magic bullet" has largely been realized. There are currently 22 monoclonal antibodies (mAbs) approved by the United States Food and Drug Administration (FDA) for clinical use and hundreds are in clinical trials for treatment of various diseases including cancers, immune disorders, and infections. The revenues from the top five therapeutic antibodies (Rituxan, Remicade, Herceptin, Humira, and Avastin) nearly doubled from $6.4 billion in 2004 to $11.7 billion in 2006. During the last several years major pharmaceutical companies raced to acquire antibody companies, with a recent example of MedImmune being purchased for $15.6 billion by AstraZeneca. These therapeutic and business successes reflect the major advances in antibody engineering which have resulted in the generation of safe, specific, high-affinity, and non-immunogenic antibodies during the last three decades. Currently, second and third generations of antibodies are under development, mostly to improve already existing antibody specificities. However, although the refinement of already known methodologies is certainly of great importance for potential clinical use, there are no conceptually new developments in the last decade comparable, for example, to the development of antibody libraries, phage display, domain antibodies (dAbs), and antibody humanization to name a few. A fundamental question is then whether there will be another change in the paradigm of research as happened 1-2 decades ago or the current trend of gradual improvement of already developed methodologies and therapeutic antibodies will continue. Although any prediction could prove incorrect, it appears that conceptually new methodologies are needed to overcome the fundamental problems of drug (antibody) resistance due to genetic or/and epigenetic alterations in cancer and chronic infections, as well as problems related to access to targets and complexity of biological systems. If new methodologies are not developed, it is likely that gradual saturation will occur in the pipeline of conceptually new antibody therapeutics. In this scenario we will witness an increase in combination of targets and antibodies, and further attempts to personalize targeted treatments by using appropriate biomarkers as well as to develop novel scaffolds with properties that are superior to those of the antibodies now in clinical use.

The growth and potential of human antiviral monoclonal antibody therapeutics

Monoclonal antibodies (mAbs) have long provided powerful research tools for virologists to understand the mechanisms of virus entry into host cells and of antiviral immunity. Even so, commercial development of human (or humanized) mAbs for the prophylaxis, preemptive and acute treatment of viral infections has been slow. This is surprising, as new antibody discovery tools have increased the speed and precision with which potent neutralizing human antiviral mAbs can be identified. As longstanding barriers to antiviral mAb development, such as antigenic variability of circulating viral strains and the ability of viruses to undergo neutralization escape, are being overcome, deeper insight into the mechanisms of mAb action and engineering of effector functions are also improving the efficacy of antiviral mAbs. These successes, in both industrial and academic laboratories, coupled with ongoing changes in the biomedical and regulatory environments, herald an era when the commercial development of human antiviral mAb therapies will likely surge.

Toward elimination of perinatal human immunodeficiency virus transmission in the United States: effectiveness of funded prevention programs, 1999-2001

The objective of the study was to assess the effectiveness of federal funds in preventing perinatal human immunodeficiency virus (HIV) transmission in the United States. We used surveillance data from 1999 and 2001 in 6 funded areas to estimate the proportion of HIV-infected women prescribed perinatal prophylaxis and whose infants were HIV infected. We compared outcomes with 5 unfunded areas in which surveillance data were available. The proportion of funded-area women prescribed prophylaxis increased from 80.1% to 85.9% (P < .01), compared with a decline in unfunded areas from 95.1% to 86.7% (P < .01); the difference in trends between groups was P < .01. The perinatal HIV transmission rate for funded areas declined from 6.5% (105 cases) in 1999 to 3.4% (46 cases) in 2001 (P < .01), compared with a decline in unfunded areas from 4.3% (19 cases) to 3.4% (13 cases) (P = .59); the difference in trends between groups was P = .24). The number of perinatal HIV infections in the funded areas decreased by 56%, achieving the Centers for Disease Control and Prevention's goal of a 50% reduction in incidence by 2005.

Elimination of HIV-1 infection by treatment with a doxorubicin-conjugated anti-envelope antibody

OBJECTIVE

To test the efficacy of an immunoconjugate against HIV-1.

DESIGN

: A murine monoclonal antibody against the envelope antigen of HIV (P4/D10) was conjugated with the conventional anticancer drug, doxorubicin, and tested against infectious virus and infected cells, both in vitro and in vivo.

METHODS

P4/D10 antibody was incubated with free virus (neutralization) or HIV-infected cells (inhibition) and the resulting infection was measured by a p24 capture enzyme-linked immunosorbent assay. In an HIV-1/MuLV murine challenge model, the ability of the conjugate to inhibit infection in vivo was measured.

RESULTS

Doxorubicin-conjugated P4/D10 neutralized HIV-1IIIB and eliminated intercellular spread and HIV replication in infected Jurkat cells in vitro. The conjugate also protected mice from challenge with HIV-1IIIB/MuLV at an eightfold lower concentration than needed for free antibody, whereas no effects were observed for comparable doses of free drug or irrelevant conjugate controls.

CONCLUSION

This indicates that doxorubicin is concentrated to HIV-infected cells by the P4/D10 antibody, significantly (P = 0.0001) contributing to HIV elimination. This concept could also be adapted to eradicate remaining antigen-expressing T cells in patients treated with antiretroviral therapy.

Efficient expression of recombinant human monoclonal antibodies in Drosophila S2 cells

We have explored the Drosophila S2 cell line for expression of Ig molecules isolated as Fab or scFv cDNA from phage-displayed libraries. We present a series of vectors for inducible expression and secretion of human Ig heavy (HC) and light chains (LC), both on separate plasmids and in combination constructs. Both HC (tested as human gamma(1)) and LC (human kappa) could be expressed separately and were secreted into the medium, confirming previous reports. When the combination vector carrying both the HC and LC cDNA, as well as when the HC and LC vectors were co-transfected, complete IgG1 was found in the medium. Transient transfection resulted in production levels of 0.5-1 mg/l. Stable cell lines could be established within 2-3 weeks. After 10-12 days of expression from such cell lines, Ig molecules accumulated and the medium contained typically 5-35 mg/l of IgG1. The IgG in these preparations was purified to more than 90% purity on protein G columns. Binding characteristics for IgG of the same clone expressed in S2 cells or mammalian cells were indistinguishable. The main advantages with this system compared to mammalian expression were its robustness and the much faster establishment of stable, high level producing cell lines.

Amniotic fluid has higher relative levels of lentivirus-specific antibodies than plasma and can contain neutralizing antibodies

BACKGROUND

The in utero transmission rate of HIV-1 is estimated to be 10-15% in the absence of interventions and breastfeeding. Natural protective mechanisms involving lentivirus-specific antibodies may therefore exist to limit in utero transmission of lentiviruses.

OBJECTIVES

HIV-1- and SIV-specific immunoglobulin G (IgG) levels in amniotic fluid samples from humans and rhesus macaques were assessed.

STUDY DESIGN

HIV-1- and SIV-specific immunoglobulin G levels, relative to total IgG concentrations in amniotic fluid samples from humans and rhesus macaques, were determined using a quantitative Western blotting procedure. Amniotic fluid from rhesus macaques was tested for the ability to neutralize SIV infection of CEMX174 cells.

RESULTS

The levels of HIV-1- and SIV-specific immunoglobulin G, relative to total IgG concentrations in amniotic fluid samples from humans and rhesus macaques, were approximately 3-10-fold higher than in plasma. The ability of antibodies in human amniotic fluid samples to neutralize viral infectivity could not be assessed, because zidovidine was present in the samples. Most amniotic fluid samples from rhesus macques not treated with antiretrovirals were able to neutralize SIV infectivity, except for a sample from a SIV positive rhesus whose infant was infected in utero.

CONCLUSIONS

Active immunity to HIV-1 resulting in virus-specific antibodies in amniotic fluid exists, and may be a natural barrier to in utero infection. This may provide hope for stimulating neutralizing antibody via vaccine design.

Multi-subtype gp160 DNA immunization induces broadly neutralizing anti-HIV antibodies

A highly desirable feature for an human immunodeficiency virus type 1 (HIV-1) vaccine is the ability to induce broadly reactive anti-envelope antibodies that can neutralize primary HIV-1 isolates. Two immunizations with an HIV-1 envelope-encoding plasmid together with recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) resulted in high antibody titers in mice. The antibody induction was further enhanced after immunization with genes encoding HIV-1 envelopes originating from subtypes A, B and C. The sera from these animals were able to neutralize A, B and C viral isolates, whereas the sera from animals immunized solely with subtype B DNA neutralized only subtype B virus. The combined DNA vaccine gave serum antibodies with broad recognition of HIV-1 envelope epitopes as determined by peptide mapping. Cell-mediated immunity was not compromised by the increased humoral immunity. This demonstrates the ability of multiple envelope genes to induce the desired antibody response against several subtypes. Moreover, it documents the ability of rGM-CSF to enhance the potency of such a vaccine when given simultaneously. The strategy may be useful for making an HIV vaccine more potent and broadly effective against strains of different clades.

Immunoprophylaxis to Prevent Mother-to-Child Transmission of HIV-1

Antiretroviral therapy can profoundly reduce the risk of mother-to-child transmission (MTCT) of HIV, but the drugs have a relatively short half-life and should thus be administered throughout breast-feeding to optimally prevent postnatal infection of the infant. The potential toxicities and the development of resistance may limit the long-term efficacy of antiretroviral prophylaxis, and a safe and effective active/passive immunoprophylaxis regimen, begun at birth, and potentially overlapping with interpartum or neonatal chemoprophylaxis, would pose an attractive alternative. This review draws on data presented at the Ghent Workshop on prevention of breast milk transmission and on selected issues from a workshop specifically relating to immunoprophylaxis held in Seattle in October 2002. This purpose of this review is to address the scientific rationale for the development of passive (antibody) and active (vaccine) immunization strategies for prevention of MTCT. Data regarding currently or imminently available passive and active immunoprophylaxis products are reviewed for their potential use in neonatal trials within the coming 1-2 years.

Prevention of perinatal HIV transmission: a review of novel strategies

Significant progress has been made in preventing transmission of HIV-1 from mother to infant. With combination antiretroviral therapies, transmission rates lower than 2% have been achieved in clinical studies. Abbreviated regimens covering labour and the first few days of neonatal life have shown considerable promise in the developing world. Several questions and challenges remain, however. These include choice of the optimal antiretroviral agent(s) and duration of the regimens, availability of antiretroviral agents in developing countries, long-term safety of antiretrovirals during pregnancy and early neonatal life and the problem of breastfeeding transmission in countries where alternatives to breastfeeding are not available. A wider array of strategies for prevention of mother-to-child transmission of HIV-1 during breastfeeding, including passive and active immunisation, may offer much needed answers to the problem of continued HIV transmission from mother to infant.