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BackgroundGender reassignment surgery is a procedure some transgender women (TW) undergo for gender-affirming purposes. This often includes the construction of a neovagina using existing penile and scrotal tissue and/or a sigmoid colon graft. There are limited data regarding the composition and function of the neovaginal microbiome representing a major gap in knowledge in neovaginal health.ResultsMetaproteomics was performed on secretions collected from the neovaginas (n = 5) and rectums (n = 7) of TW surgically reassigned via penile inversion/scrotal graft with (n = 1) or without (n = 4) a sigmoid colon graft extension and compared with secretions from cis vaginas (n = 32). We identified 541 unique bacterial proteins from 38 taxa. The most abundant taxa in the neovaginas were Porphyromonas (30.2%), Peptostreptococcus (9.2%), Prevotella (9.0%), Mobiluncus (8.0%), and Jonquetella (7.2%), while cis vaginas were primarily Lactobacillus and Gardnerella. Rectal samples were mainly composed of Prevotella and Roseburia. Neovaginas (median Shannon's H index = 1.33) had higher alpha diversity compared to cis vaginas (Shannon's H = 0.35) (p = 7.2E-3, Mann-Whitney U test) and were more similar to the non-Lactobacillus dominant/polymicrobial cis vaginas based on beta diversity (perMANOVA, p = 0.001, r2 = 0.342). In comparison to cis vaginas, toll-like receptor response, amino acid, and short-chain fatty acid metabolic pathways were increased (p < 0.01), while keratinization and cornification proteins were decreased (p < 0.001) in the neovaginal proteome.ConclusionsPenile skin-lined neovaginas have diverse, polymicrobial communities that show similarities in composition to uncircumcised penises and host responses to cis vaginas with bacterial vaginosis (BV) including increased immune activation pathways and decreased epithelial barrier function. Developing a better understanding of microbiome-associated inflammation in the neovaginal environment will be important for improving our knowledge of neovaginal health. Video Abstract.

Although nonhuman primate studies have shown that simian immunodeficiency virus/simian-human immunodeficiency virus (SIV/SHIV) exposure during preexposure prophylaxis (PrEP) with oral tenofovir can induce SIV immunity without productive infection, this has not been documented in humans. We evaluated cervicovaginal IgA in Partners PrEP Study participants using a subtype C primary isolate and found that women on PrEP had IgA with higher average human immunodeficiency virus type 1 (HIV-1)-neutralizing magnitude than women on placebo (33% versus 7%; P = 0.008). Using a cutoff of ≥90% HIV-1 neutralization, 19% of women on-PrEP had HIV-1-neutralizing IgA compared to 0% of women on placebo (P = 0.09). We also estimated HIV-1 exposure and found that the proportion of women with HIV-1-neutralizing IgA was associated with the level of HIV-1 exposure (P = 0.04). Taken together, our data suggest that PrEP and high levels of exposure to HIV may each enhance mucosal HIV-1-specific humoral immune responses in sexually exposed but HIV-1-uninfected individuals.ImportanceAlthough there is not yet an effective HIV-1 vaccine, PrEP for at-risk HIV-1-uninfected individuals is a highly efficacious intervention to prevent HIV-1 acquisition and is currently being recommended by the CDC and WHO for all individuals at high risk of HIV-1 acquisition. We previously demonstrated that PrEP use does not enhance peripheral blood HIV-1-specific T-cell responses in HIV-exposed individuals. Here, we evaluate for cervicovaginal HIV-neutralizing IgA responses in genital mucosal secretions of HIV-exposed women, which is likely a more relevant site than peripheral blood for observation of potentially protective immune events occurring in response to sexual HIV-1 exposure for various periods. Furthermore, we assess for host response in the context of longitudinal quantification of HIV-1 exposure. We report that HIV-neutralizing IgA is significantly correlated with higher HIV-1 exposure and, furthermore, that there are more women with HIV-1-neutralizing IgA in the on-PrEP group than in the placebo group.

ObjectiveThe effects of sex hormones on the immune defenses of the female genital mucosa and its susceptibility to infections are poorly understood. The injectable hormonal contraceptive depot medroxyprogesterone acetate (DMPA) may increase the risk for HIV-1 acquisition. We assessed the local concentration in the female genital mucosa of cationic polypeptides with reported antiviral activity in relation to DMPA use.MethodsHIV-1-uninfected women were recruited from among couples testing for HIV in Nairobi, Kenya. Cervicovaginal secretion samples were collected, and the concentrations of HNP1-3, LL-37, lactoferrin, HBD-2, and SLPI were measured by enzyme-linked immunosorbent assays. Levels of cationic polypeptides in cervicovaginal secretions were compared between women who were not using hormonal contraception and those using DMPA, oral, or implantable contraception.ResultsAmong 228 women, 165 (72%) reported not using hormonal contraception at enrollment, 41 (18%) used DMPA, 16 (7%) used an oral contraceptive, and 6 (3%) used a contraceptive implant. Compared with nonusers of hormonal contraception, DMPA users had significantly higher mean levels of HNP1-3 (2.38 vs. 2.04 log₁₀ ng/mL; P = 0.024), LL-37 (0.81 vs. 0.40 log10 ng/mL; P = 0.027), and lactoferrin (3.03 vs. 2.60 log₁₀ ng/mL; P = 0.002), whereas SLPI and HBD-2 were similar.ConclusionsAlthough all analyzed cationic polypeptides have intrinsic antiviral capacity, their interaction and cumulative effect on female genital mucosa susceptibility to infections in vivo has yet to be unraveled. This study suggests a potential mechanism underlying the effect of DMPA on the innate immune defenses, providing a rationale to investigate its effect on HIV-1 acquisition risk.

There is an association between the clinical stage of HIV-1 infection and the presence of antibodies against viral gag proteins (p17 and p24). The IgG subclass (G1 and G3) pattern against these antigens was analysed in stable patients and HIV patients progressing to AIDS. Antibodies were analysed with whole viral or peptide ELISA (using sequentially overlapping peptides) and Western Blots. IgG1 was found to be the dominant anti-HIV-1 IgG subclass and IgG1 antibodies declined in progressing patients against all HIV antigens evaluated in Western blot, including p17, p24, p31, gp41, p64, gp120 and gp160. In contrast IgG antibodies, which were found to be predominantly directed against gag proteins, and which could be detected in almost all patients, remained in the circulation during disease progression. By peptide assays distinct immunogenic regions were found in p17 in contrast to more events distributed epitopes in p24. A decreased divergence of antibody reactivity to both p17 and p24 peptides in the group of patients who developed AIDS was seen. No reaction to any single gag epitope related to disease progression. The difference between IgG1 and IgG3 anti-gag antibodies in relation lo clearance during disease progression may depend on different properties of immune complexes formed by these two IgG subclasses. [ABSTRACT FROM AUTHOR]

The anti-HIV IgG subclass response was analysed in sera from different clinical stages and related to virus specific antibody-dependent cellular cytotoxicity (ADCC). IgG1 was found to be the dominant subclass, present in all sera and with similar mean titres at different stages. The number of anti-HIV IgG3 positive sera, measured on whole viral lysate antigen plates, decreased during disease progression from 38% in symptom-free to 7% in AIDS patients. IgG2 and IgG4 subclasses were less prevalent although a slight increase of IgG4 frequency was found in AIDS patients. High IgGl titres correlated with a positive ADCC reaction but there was no correlation between anti-HIV IgG1 and ADCC titres. Some sera which contained HIV IgG1 as the only subclass were able to mediate an ADCC reaction. In addition, when anti-HIV IgG3 was isolated, by protein A chromatography, no ADCC killing was induced by these antibodies. It is concluded that IgG1 is the major ADCC-active IgG subclass in HIV infected individuals. The lack of correlation between IgG1 and ADCC titres may be explained by a relatively small fraction of IgG1 antibodies mediating ADCC. [ABSTRACT FROM AUTHOR]

Peripheral blood lymphocytes from healthy, HIV sero-negative blood donors have been in vitro immunized using penv9, a recombinant fragment of the envelope of HIV-1. This primary in vitro immunization followed by Epstein-Barr virus (EBV) transformation and somatic cell fusion subsequently gave rise to several specific anti-penv9 monoclonal antibodies (MO28, MO30 and MO43) of μ isotype. The hybridomas have been kept in culture for over 6 months and the antibody productivity for MO30 was measured to 18 μg × (24 hr × 106 cells)-1. The fine specificity of the antibodies was mapped by a peptide inhibition enzyme immunoassay, using overlapping synthetic pentadeca peptides covering the whole penv9. These human monoclonal antibodies exhibited a similar epitope specificity directed against a non-sequential determinant, including the amino acids 632–646, 677–681 and 687–691. This specificity is very rarely found in immune sera from sero-positive patients and presently not reported in human monoclonal antibodies derived from in vivo immunized individuals, indicating that different antibody specificities can be obtained by the in vitro immunization technology. These human monoclonal antibodies did not neutralize HIV. The results presented here demonstrate the feasability of generating human monoclonal antibodies against HIV by primary in vitro immunizations, thereby avoiding the use of lymphocytes derived from infected patients when human monoclonal antibodies for therapeutic purposes are to be produced. [ABSTRACT FROM AUTHOR]

Fifteen amino acid peptides, sequentially overlapping by 10 amino acids, were synthesized on the basis of the HTLV-III sequences of the gag and env proteins. They were used as antigens in IgG subclass ELISAs and T-cell stimulation assays. Sera and cells were obtained from 30 asymptomatic, HIV-infected homosexuals. in all subclasses reactivity was found to parts of the gag protein, while IgG I dominated anti-env peptide responses. It was possible to delineate peptides showing restricted IgG subclass responses that were dominated by either IgG 1, 2, 3 or 4. A negative correlation was generally observed between B-cell and T-cell reactivity, but a T-cell and B-cell co-operation was suggested by the response to two IgG1-restricted peptides. The IgG3-dominated epitopes were present in peptides previously known to be amphipathic and capable of T-cell stimulation. The analysis of subclass-restricted responses on the peptide level will assist the understanding of the subclass expression in vivo, since the peptide mapping approximates the delineation of a subclass- restricted response at the level of single epitopes. [ABSTRACT FROM AUTHOR]

Human MoAbs of IgM class were developed against three regions of the HIV-1 envelope. Uninfected donor lymphocytes were immunized in vitro with recombinant protein pB1. Four out of five antibodies were directed to different parts of the V3 region, which contains a major neutralizing site. Two out of these antibodies were directed to more than one amino acid sequence, indicating reactivity to discontinuous sites. Two of the human MoAbs inhibited viral spread between cells in tissue culture, interpreted as reactivities to conserved amino acid sequences exposed during viral maturation. No MoAb neutralized virus, which may be explained by the relatively low avidity of the antibodies. One MoAb was directed to a region containing amino acids participating in CD4 binding. This technique appears to allow formation of antibodies with fine specificities other than those obtained in infected hosts. [ABSTRACT FROM AUTHOR]

The article summarizes the work from many laboratories in the identification of antigenic regions from HIV, a variety of methods of identification and interpretation of results means that not all groups agree on the importance of certain epitopes. However, consensus agreement on many regions exist where independent laboratories have confirmed results from others. The knowledge of these regions can be applied in several ways to improve understanding of the natural immune response to HIV, to contemplate manipulation of immune responses in infected individuals, either stimulation as active immunotherapy or suppression of deleterious responses, and in the design of a subunit prophylactic vaccine.

To define the amino acids involved in IgG subclass reactivity to two overlapping HIV-1 gp41 (E34/32; amino acid positions 582-613) peptides, sera from 18 HIV-infected individuals were studied. Peptides mimicking E34 but with single amino acid deletions or glycine substitutions were used to define the amino add residues necessary for antibody binding. Two dominating immunogenic epitopes, containing highly hydrophilic amino acids, were found on the original peptide. Further analysis was undertaken with two corresponding omission sets of dodecapeptides representing halves of the complete E34 plus a terminal cystein peptide. The subclass reactivities usually differed between the patients with regard to the epitopes with which the different IgG subclasses reacted and also to the importance of different amino acids in antibody binding. The 600 glycine and the 601 lysine were involved in the binding of all IgG1,2 and 4 and most IgG3. The development of E34/32-reactive IgM and IgG subclasses showed different patterns in four patients with primary HIV infections, contradicting the existence of a general pattern for the development of IgG subclasses to this peptide. The findings suggest that different progenitor clones are selected for synthesis of the different subclasses. [ABSTRACT FROM AUTHOR]

Phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, suppresses natural, lectin and antibody-dependent killing by normal human lymphocytes in short-term radioisotope release assays. Fifty percent inhibition of killing of lymphoid target cells was seen at approximately 5 ng/ml TPA and inhibition was further potentiated by the presence of monocytic cells. In contrast, TPA increased killing of K-562 erythroleukaemic cells by non-adherent NK cells with optimal activity around I ng/ml. Two anti-estrogenic drugs, tamoxifen and clomiphene, known to inhibit protein kinase C, gave near to complete inhibition of NK killing at concentrations 12 and 30 μM, respectively. Retinal, another protein kinase C inhibitor, inhibited both antibody- dependent killing and lectin-dependent killing. An influx of 45Ca2+ into the effector population was found during effector-target cell conjugation and this flux was suppressed at TPA concentrations similar to those that suppressed killing. The results suggest that killing depends on a co-ordinated activation of protein kinase C together with a channel-dependent calcium influx. TPA may suppress killing by a negative feedback effect of protein kinase C on the hydrolysis of inositol phospholipids, as demonstrated in many other systems, or through the down-regulation of cell surface receptors required for triggering of lysis. [ABSTRACT FROM AUTHOR]

A potential component that may be useful for passive immunotherapy for HIV-1 is human monoclonal antibodies (HumAbs) possessing potent anti-HIV-1 activity that is directed against conserved regions of the envelope glycoprotein. Such antibodies would, in principle, have the ability to neutralize diverse isolates of HIV-1. To develop such reagents, hybridomas were derived by initial Epstein Barr virus transformation of peripheral blood mononuclear cells (PBMCs) from an asymptomatic HIV-1 seropositive donor followed by fusion with heteromyelomas, and secreted anti-HIV-1 antibodies were further characterized. The specificity of one HumAb, designated as clone 3, was determined by enzyme-linked immunosorbent assay (ELISA) and Western blotting analyses that indicated reactivity to the transmembrane envelope glyco-protein gp41. Synthetic pentadecapeptides overlapping by 10 amino acids were utilized for epitope mapping of clone 3; a decapeptide GCSGKLICTT in the transmembrane gp41 was identified as the epitope. Clone 3 bound to SupT1 cells infected with HTLV-IIIB in fluorescent activated cell sorting analysis. In addition, in vitro biological assays demonstrated that clone 3 possessed neutralization reactivity against diverse laboratory isolates as well as an AZT-resistant isolate. Therefore, clone 3 reactivity defines a conserved neutralizable site on the HIV-1 transmembrane glycoprotein. Clone 3 and the conserved immunogenic epitope on gp41 could be useful in passive and active immunotherapy for the acquired immunodeficiency syndrome (AIDS).

Mouse monoclonal antibodies with high human immunodeficiency virus type 1 (HIV-1) neutralizing titers were used for passive immunotherapy of eleven late-state HIV-infected patients. In five patients the serum level of the core protein p24 decreased, while in five cases it remained unchanged. The level of viral RNA in plasma as measured by quantitative polymerase chain reaction (PCR) decreased in four cases, was stable in another four, and increased in three cases. An anti-mouse (HAMA) response developed in eight patients and anti-idiotypic antibodies appeared in six. Immune complexes that formed in patient sera during the treatment were shown to contain mostly envelope glycoprotein gp120 which decreased in nine of the eleven treated patients toward the end of treatment. Antibodies inhibiting gp120 binding to CD4 became detectable or increased in six patients during immunotherapy. Serology of the HIV-1 V3 region was studied for both the HIV-1 IIIB and MN strains with no or very small changes in titer or avidity after treatment. No change in neutralizing titers to strain HTLVIIIB was observed in serum samples collected before and after treatment was terminated. In nine of the eleven patients stimulation of the T lymphocytes to proliferate in vitro when activated by phytohemagglutinin (PHA) was shown to be increased compared to before treatment. Increased T-cell proliferation was also noted with several antigens such as HIV-1 recombinant antigens, cytomegalovirus (CMV), tetanus toxoid (TT), and purified protein derivate of mycobacterium tuberculosis (PPD). These findings indicate a decreased total gp120 content in serum, permitting better T-cell activation.

Strong specific T-cell responses to human immunodeficiency virus type 1 (HIV-1) gp160 were induced by immunization with recombinant gp160 (rgp160). It was given as postinfection vaccination to 40 asymptomatic HIV-1 seropositive patients. The participants received 6 doses of 160 micrograms rgp160 administered intramuscularly at 0, 1, 4, 8, 17, and 26 weeks and were monitored for 1 year. Lymphocyte proliferation was performed by cultivating lymphoid cells in vitro with specific antigens and mitogens. After immunization with gp160, specific T-cell proliferative responses were induced in all 40 patients. One week after the sixth immunization at day 180, a substantially increased response was detected in 98% of the patients, with a mean stimulation index value of 195. Furthermore, proliferative responses were also identified, after immunization, against native gp120 and against a peptide representing the V3 region of gp120. In addition to the HIV-specific T-cell responses, increased reactivity to several other non-HIV antigens, including tetanus toxoid, influenza, measles, and cytomegalovirus, were seen after gp160 vaccination. The responses to CMV and measles were interpreted to represent an improved recall antigen response. Such recall antigen responses were few in matched HIV-infected controls immunized with influenza virus only. All patients initially and repeatedly showed a normal capacity of total T-cell activation, evaluated by the mitogen phytohemagglutinin (PHA). The trend in CD4 counts improved in 30 of 40 patients during the year of follow-up. The frequency of increases of proliferative responses to antigens was associated with a better CD4 trend. Addition of zidovudine for 2 weeks after each immunization had no beneficial effects nor did it prevent induction of immune responses. All patients tolerated the immunizations well, and no systemic adverse effects were noted. This is a phase I trial, and no definitive conclusions regarding clinical efficacy can be reached.

Synthetic peptides were used to identify continuous antigenic sites on the external envelope glycoprotein gp125 of human immunodeficiency virus (HIV)-2. Initially, seven HIV-2-positive human serum samples were screened with 172 sequential nonapeptides containing a six-amino-acid overlap. This represents the entire gp125 molecule of HIV-2ISY. The antibody reactivity was found to be mainly restricted to 14 regions within gp125. Following these results, 33 longer peptides, 15-24 amino acids in length, were synthesized and tested against a larger number of samples. Eleven antigenic regions were thus identified. Two of these were detected within a region corresponding to the C1 region and four others within a region corresponding to the C2 region of HIV-1. The highest frequency of reactivity (90%) of 31 HIV-2 seropositive human serum samples was elicited by three peptides from a region corresponding to the V3 region of HIV-1. The C-terminal portion of this region was recognized by almost 80% of the samples. Reactive regions corresponding to the V4, V5, and N-terminal portion of V4 were also identified. A mouse monoclonal antibody reacting with gp125 was mapped to the N-terminal region of the molecule and was found to react with the sequence DVWNLFETS. The peptides were used to evaluate the antibody response of monkeys immunized with whole killed HIV-2 or simian immunodeficiency virus (SIV). The monkeys showed a pattern of reactivity similar to HIV-2-infected human serum samples. Postinfection samples from monkeys inoculated with HIV-2 or SIV reacted mainly to peptides from the V3 region. Two peptides were used to detect the seroconversion of two SIV-infected monkeys. Thus, we have demonstrated that human seroreactivity to HIV-2 gp125 occurs at a few distinct linear antigenic sites distributed at similar positions on the molecule as those in HIV-1 gp120.

The importance of the dependence on single amino acids in the V3 region of HIV-1 gp120 was evaluated for virus neutralization and antibody-dependent cellular cytotoxicity (ADCC). Synthetic overlapping 15-mer peptides and a set of omission peptides covering amino acids 301-317 were used. Sera from 29 HIV-1-infected individuals at different stages of disease were tested for neutralization, ADCC and specific IgG reactivity. Six HIV-1 neutralizing monoclonal antibodies (mAb) acted as controls. All mAb reacted with a region (amino acids 304-318) of gp120, previously shown to induce neutralizing antibodies. The amino acids essential for reactivity were identified to be within the sequence GPGR (amino acids 312-315). The importance of this region for occurrence of neutralizing antibodies in infected humans was investigated using the same set of peptides. Out of 29 individuals, 21 were found to have neutralizing antibodies in titres between 100 and 1000. Among the neutralization-positive sera, 17/21 (81%) reacted with amino acids 304-318, compared with only one of eight sera (13%) negative in neutralization. When any of the four amino acids G, P, G or R were deleted, the seroreactivity decreased considerably. The conserved sequence GPGR was therefore considered to be the most important for neutralization in this region in human sera as well. Thus, the conserved sequence GPGR in the V3 region of gp120 is critical for virus neutralization by human HIV-1-specific antibodies.

A panel of highly purified synthetic oligopeptides representing defined parts of the gag and env proteins of HIV-1 and HIV-2 were used as antigens in ELISA for serodiagnosis of HIV-1 and HIV-2 infection. The analysis included sera from 321 HIV-infected patients and 201 healthy controls from the Ivory Coast, where the prevalence is high for both HIV-1 and HIV-2, and sera from European HIV-1-infected individuals. All sera from HIV-1-infected individuals reacted with a 20 amino acid (a.a.) peptide JB-4c (a.a. 594-613) derived from a highly immunogenic conserved region of the external part of gp41. An equally good response was seen in the HIV-2-infected individuals to a 20 a.a. peptide, JB-16c, from the corresponding part of HIV-2 gp36. Both HIV-1- and HIV-2-seropositive individuals responded well to a peptide, JB-8pc (a.a. 427-448), representing the C-terminal end of the putative CD4-binding site of gp120 of HIV-1. The frequency of reactivity to three selected HIV-1 gag peptides derived from p17 and p15 was 60-70% in both HIV-1 and HIV-2-positive sera. To distinguish between HIV-1 and HIV-2 infection, the sera were titrated against the peptides. Although there was a high degree of cross-reactivity at lower serum dilutions, it was possible to discriminate the infections at higher dilutions to the HIV-1 and HIV-2 gp41/gp36 peptides JB-4c and JB-16c. Analysis of serum reactivity to several selected peptides thus allowed the identification of HIV infection, and the discrimination between HIV-1 and HIV-2.(ABSTRACT TRUNCATED AT 250 WORDS)

Phorbol ester 12-O-tetradecanoylphorbol-13-acetate (TPA), an activator of protein kinase C, suppresses natural, lectin and antibody-dependent killing by normal human lymphocytes in short-term radioisotope release assays. Fifty percent inhibition of killing of lymphoid target cells was seen at approximately 5 ng/ml TPA and inhibition was further potentiated by the presence of monocytic cells. In contrast, TPA increased killing of K-562 erythroleukaemic cells by non-adherent NK cells with optimal activity around 1 ng/ml. Two anti-estrogenic drugs, tamoxifen and clomiphene, known to inhibit protein kinase C, gave near to complete inhibition of NK killing at concentrations 12 microM and 30 microM, respectively. Retinal, another protein kinase C inhibitor, inhibited both antibody-dependent killing and lectin-dependent killing. An influx of 45Ca2+ into the effector population was found during effector-target cell conjugation and this flux was suppressed at TPA concentrations similar to those that suppressed killing. The results suggest that killing depends on a co-ordinated activation of protein kinase C together with a channel-dependent calcium influx. TPA may suppress killing by a negative feedback effect of protein kinase C on the hydrolysis of inositol phospholipids, as demonstrated in many other systems, or through the down-regulation of cell surface receptors required for triggering of lysis.

Peripheral blood lymphocytes from healthy, HIV sero-negative blood donors have been in vitro immunized using penv9, a recombinant fragment of the envelope of HIV-1. This primary in vitro immunization followed by Epstein-Barr virus (EBV) transformation and somatic cell fusion subsequently gave rise to several specific anti-penv9 monoclonal antibodies (MO28, MO30 and MO43) of mu isotype. The hybridomas have been kept in culture for over 6 months and the antibody productivity for MO30 was measured to 18 micrograms x (24 hr x 10(6) cells)-1. The fine specificity of the antibodies was mapped by a peptide inhibition enzyme immunoassay, using overlapping synthetic pentadeca peptides covering the whole penv9. These human monoclonal antibodies exhibited a similar epitope specificity directed against a non-sequential determinant, including the amino acids 632-646, 677-681 and 687-691. This specificity is very rarely found in immune sera from seropositive patients and presently not reported in human monoclonal antibodies derived from in vivo immunized individuals, indicating that different antibody specificities can be obtained by the in vitro immunization technology. These human monoclonal antibodies did not neutralize HIV. The results presented here demonstrate the feasability of generating human monoclonal antibodies against HIV by primary in vitro immunizations, thereby avoiding the use of lymphocytes derived from infected patients when human monoclonal antibodies for therapeutic purposes are to be produced.