Antibody that inhibits human immunodeficiency virus reverse transcriptase and association with inability to isolate virus

Vaccination against drug resistance in HIV infection

HIV-1 resistance to currently employed antiretroviral drugs and drug-associated adverse reactions and toxicity point to a need for additional measures to control HIV-1 replication in HIV-infected patients. The immune system of HIV-infected individuals mount an immune response against the regions harboring drug-resistance mutations, sometimes stronger than that against the parental wild-type sequences. A potent cross-reactive immune response against drug-resistant pol proteins can suppress the replication of drug-escaping HIV. This suggests the possibility for a vaccination against existing and anticipated drug-resistant HIV variants. If successful, therapeutic vaccines against drug resistance would ease the therapeutic modalities and limit the spread of drug-resistant HIV. A better understanding of the complex interactions between patterns of drug-resistance mutations, immune responses against these mutations and their antigen presentation by particular human lymphocyte antigen alleles could help to tailor these vaccines after new drugs/new mutations. In this review, we describe the developments in the field of immunization against mutations conferring drug resistance and evaluate their prospects for human vaccination.

Isolation and quantitation of HIV in peripheral blood

Quantitation of replication-competent human immunodeficiency virus (HIV) in peripheral blood of infected individuals is critical for investigations of HIV pathogenesis and therapy. In this unit, the basic protocol determines the HIV titer in seropositive blood by measuring the tissue culture infectious dose (TCID) by an end-point dilution method. A second basic protocol utilizes the PHA-stimulated T cell blasts (activated T cells) in co-culture with PBMC as described in the first basic protocol for the short-term growth of HIV in vitro. An Alternate Protocol describes the accumulative method of determining 50% tissue culture infectious dose (TCID(50)) of HIV using the Reed-Muench equation when multiple replicates of a given sample are employed in the assay. A consequence of HIV infection is the depletion of CD4(+) target cells, evidenced by syncytia formation or single-cell death; two support protocols detail the evaluation of these cytopathic effects.

Eukaryotic expression of enzymatically active human immunodeficiency virus type 1 reverse transcriptase

Reverse transcriptase of human immunodeficiency virus type I is a vitalenzyme in the HIV-1 replication cycle and an attractive target of attempts to arrest a primary viral infection. We designed a vector for eukaryotic expression of the 66 kDa subunit of reverse transcriptase under the control of the immediate early cytomegalovirus promoter. Efficient transient expression of the 66 kDa subunit of reverse transcriptase was achieved in a variety of cells. Immunostaining of the transfected cells revealed the cytoplasmatic localization of reverse transcriptase. Reverse transcriptase activity was detected in all transfected cell lines. Injection of this plasmid encoding the 66 kDa subunit of reverse transcriptase into mice resulted in strong reverse transcriptase-specific immune responses indicating that the 66 kDa subunit of reverse transcriptase is expressed in vivo. Sera from DNA-immunized mice inhibited reverse transcription in vitro.

Neutralizing antibodies against HIV determined by amplification of viral long terminal repeat sequences from cells infected in vitro by nonneutralized virions

Based on the earliest intracellular synthesis of nascent HIV-1 long terminal repeat (LTR) fragments, we have established a heminested polymerase chain reaction (HNPCR) amplification of the 5' LTR sequences (LTR-HNPCR) for molecular assay of virus-neutralizing antibodies (VNAb). We incubated HIV antibodies with virus isolates for an hour, followed by addition of lymphoid cells (H9 or peripheral blood mononuclear cells [PBMC]) and further incubation for an hour. After washing the cells three times for thorough removal of free virions and antibodies, LTR-HNPCR consistently revealed HIV DNA in H9 cells after 15 minutes, in PBMC after 4 hours, and corresponding virion expression after 7 days in culture. Replication-competent HIV detected by LTR-HNPCR following overnight culture of infected PBMC for 16 to 18 hours was comparable with tissue culture infectivity measured by p24 antigen expression at 7 days. After establishing a molecular assay for in vitro HIV neutralization by HIV Ig, a panel of five HIV isolates tested with 6 monoclonal antibodies and HIV Ig revealed that LTR-HNPCR was comparable with other VNAb assays. These preliminary data indicate that the molecular assay for HIV neutralization has a clear-cut end point, is specific, reliable, and more rapid than other VNAb assays. Therefore, it offers potential utility in evaluating immune response to candidate vaccines.

Quantitative measurement of antibody inhibiting reverse transcriptase activity in cats naturally infected with feline immunodeficiency virus

Quantitative measurement of reverse transcriptase-inhibiting (RTI) antibodies in Japanese household cats naturally infected with feline immunodeficiency virus (FIV) was performed by poly A-linked colorimetric reverse transcriptase assay (PAC-RTA). Eight FIV-seropositive plasma samples were diluted twofold from 1:10 to 1:160 and incubated with FIV RT. Fifty percent RTI activity (RTI50) was calculated from a dose response PAC-RTA curve. The plasma of FIV-seropositive cats showed different RTI activities against two Japanese isolates and Petaluma strain. Six of eight plasma samples showed RTI activities against the Japanese isolates (subtype B), but only one showed RTI activity against Petaluma strain (subtype A). It is important to use the appropriate strain as a source of RT for detection of RTI antibody in cats.

Measurement of levels of human immunodeficiency virus type 1 reverse transcriptase (RT) and RT activity-blocking antibody in human serum by a new standardized colorimetric assay

Standardization and calibration of a new colorimetric assay for detection of reverse transcriptase (RT) was carried out for optimal detection of RT activity-blocking antibody (RTb-Ab) in serum. A total of 99 of 100 Swedish and 54 of 54 African human immunodeficiency virus type 1 (HIV-1) antibody-positive individuals had RTb-Ab. The one RTb-Ab-negative HIV-1 serum sample from a Swedish individual was obtained early during seroconversion. Five of 615 HIV-1-negative sera from tumor patients, pregnant women, patients undergoing routine viral diagnostics, and blood donors gave false-positive results. In addition, 3 of 126 HIV-1-negative African serum samples and 2 of 91 serum samples selected because of false reactivity in other commercially available HIV antibody assays were positive for RTb-Ab. RT activity and RTb-Ab were measured in sera from newly HIV-1-infected individuals during seroconversion. Peak RT activity was usually detected between days 8 and 13 after the onset of symptoms of primary infection. In addition, HIV-1 RTb-Ab was detected in the same recently infected individuals in most cases within 1 month and in some cases as early as 10 to 12 days after the onset of symptoms. A cross-reactivity study involving HIV-1 and HIV-2 RTb-Abs and their homologous RT showed HIV-1 RTb-Ab to be highly type specific. None of 10 serum samples from HIV-1-infected individuals showed cross-reacting RTb-Ab toward HIV-2 RT, whereas 4 of 10 serum samples from HIV-2-infected patients showed cross-reactivity toward HIV-1 RT; however, the cross-reactivity toward HIV-1 RT was 3,000 times lower than that toward its homologous RT. Future uses for the assay with reference to the recent World Health Organization proposal for other methods instead of Western blotting (immunoblotting) for confirming HIV-1 infection and for methods for the diagnosis of infection as follow-up in vaccine trials are also discussed.

Human antibodies responsible for binding inhibition and polymerization inhibition of human immunodeficiency virus type 1 reverse transcriptase

Using a solid-phase non-radioisotopic (non-RI) reverse transcriptase (RT) assay, antibodies inhibiting human immunodeficiency virus type 1 (HIV-1) RT activity (RTI antibody) were investigated for their ability to inhibit binding of RT to a template-primer and DNA polymerization. The RTI antibody inhibited the binding of RT to the template-primer (BI antibody), and directly reacted with the RT-template-primer complex and inhibited enzymatic activity (PI antibody). The RTI antibody interfered with formation of the RT-template-primer complex suggesting that it recognized the antigenic site involved in template-primer binding of RT molecules. Since deoxynucleotide triphosphates (dNTPs) blocked inhibition of the RT activity by the PI antibody, the antigenic site recognized by the PI antibody may be closely related to the dNTP binding site. The seropositivities of the BI and PI antibodies were 84.6% and 91.2%, respectively, in HIV-1-infected individuals; healthy individuals, HTLV-I-positive individuals, autoimmune disease patients and leukemia patients were all seronegative. No significant correlation of residual RT activities was observed when BI and PI antibodies were compared (r = 0.688). It is possible that the epitopes recognized by the BI antibody differs from those recognized by the PI antibody. The assays described are able to detect BI and PI antibodies in the sera of HIV-1-infected individuals.

Characteristics and clinical significance of a stabilization assay to detect specific antibodies to reverse transcriptase of human immunodeficiency virus

Antibodies against reverse transcriptase (RT) of human immunodeficiency virus type 1 (HIV-1) have been detected in seropositive subjects by immunoprecipitation, Western immunoblotting, and neutralization assay. Recently, we noticed that the antibodies against RT stabilized RT upon heat inactivation, and we have developed a stabilization assay of RT antibody. Briefly, the RT of HIV-1 is completely inactivated by incubation at 56 degrees C for 20 min, but this inactivation is inhibited in the presence of a specific antibody directed against this molecule. We examined the specificity and clinical significance of this stabilization assay. HIV-1 antibody-positive sera stabilized HIV-1 RT but not HIV-2 RT, whereas half of these sera cross-neutralized HIV-2 RT. Antibody titers against RT determined by the neutralization assay and the stabilization assay were compared with clinical characteristics. Antibodies against HIV-1 RT were much more frequently detected by the stabilization assay than by the neutralization assay. Statistically significant associations were found between stabilizing antibody titer and CD4+ cell number in peripheral blood of patients and also between antibody titer and CD4+/CD8+ ratios. These results indicate that our new stabilization assay to detect specific antibodies against RT of HIV-1 is useful as a clinical marker of infection and progress of the disease.

Differentiation between human immunodeficiency virus type 1 (HIV-1) and HIV-2 isolates by nonradioisotopic reverse transcriptase-typing assay

We tested whether human immunodeficiency virus type 1 (HIV-1) could be differentiated from HIV-2 by a reverse transcriptase (RT)-typing assay that measured the reduction of enzyme activity owing to specific antibody. RT-inhibiting antibody was examined for HIV type specificity by a new nonradioisotopic RT assay. Antibodies from four rabbits immunized with recombinant HIV-1 RT and from 23 HIV-1-seropositive individuals all specifically inhibited the enzyme activities of two HIV-1 strains (LAV-1 and GH-3), three zidovudine-resistant HIV-1 mutants, and a recombinant HIV-1 RT. However, none of these antisera affected the activities of six HIV-2 strains (GH-1, GH-2, GH-4, GH-5, GH-6, LAV-2ROD), Rous-associated virus type 2, and DNA polymerase I from Escherichia coli. In contrast, HIV-2 antibody from a rabbit immunized with disrupted GH-1 virions blocked the enzyme activities of the six HIV-2 strains but not those of the three HIV-1 strains, Rous-associated virus type 2, or DNA polymerase I. These results indicate that the antigenic domains of HIV-1 and HIV-2 RTs recognized by their inhibiting antibodies are distinct from each other and are highly conserved. Clinical HIV isolates from 18 HIV-1-seropositive individuals and 3 HIV-2-seropositive Ghanaian individuals were identified as HIV-1 and HIV-2, respectively, by the nonradioisotopic RT-typing assay.

Mechanism of enzyme inhibition mediated by anti-reverse transcriptase antibodies from HIV type 1-infected individuals

We have examined the mechanisms of reverse transcriptase (RT) inhibition mediated by anti-RT antibodies, isolated by affinity chromatography, from four HIV-1-positive individuals. In kinetics assays, anti-RT immunoglobulin (Ig) obtained from three of the sera mediated a noncompetitive type of inhibition against template primer; two of these three also mediated noncompetitive inhibition with respect to deoxyribonucleoside triphosphate. Such inhibition did not require that the Ig be preincubated with RT prior to the addition of reaction components. In contrast, a more complicated pattern of inhibition was exhibited by anti-RT Ig from the fourth serum. Preincubation of this Ig with enzyme markedly enhanced the inhibition. The results demonstrate that the specificities of RT-inhibiting antibodies vary among HIV-1-infected individuals, but that one prevalent mechanism of inhibition involves interactions with epitopes outside of the enzyme active site.

Two highly antigenic sites in the human immunodeficiency virus type 1 reverse transcriptase

Antibodies to human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT) are found in the serum of the majority of infected individuals, and inhibition of RT polymerase activity by HIV-1-positive sera can be demonstrated in vitro. The binding sites of human antibodies on the protein have not yet been identified. We synthesized overlapping peptides covering the entire RT protein of HIV-1 and used them in an enzyme-linked immunosorbent assay system to map the reactivities of HIV-1 and HIV-2 antibody-positive sera. Two highly antigenic regions were identified by both HIV serotypes. One region was found in the central part of the RT protein (amino acids 261 to 280) and another was found at the carboxy terminus in the RNase H portion of RT (amino acids 517 to 536). Comparison of the serological results with the crystal structure of the RT revealed that the antigenic region in the RNase H portion is located at the surface of the protein. The other antibody-binding site (amino acids 261 to 280) was located in the "thumb" region of the polymerase domain of RT. Polyclonal antibodies to either of the antibody-binding sites do not affect the polymerase activity of the RT protein.

Prognostic value of serum immunoglobulin A antibodies to pol gene products during HIV-1 infection

Serum specimens from 66 HIV-1-infected subjects were tested by ELISA for the presence of IgA antibodies to HIV-1: 44 samples were found positive and 37 were confirmed by immunoblot. In these subjects, the presence of anti-HIV IgA antibodies was studied in relation to the total count of circulating CD4+ lymphocytes and to the level of serum IgA. A significative correlation (P < 0.03) was found between the absence of IgA to the subunit p68 of the reverse transcriptase and a count of CD4+ cell < 400/mm3 or total IgA level over 4.25 g/l. The same pattern was observed for the IgA antibodies to the p52 subunit but the association was just not significant (P < 0.07). No significant decrease was noted for the IgA directed towards the other proteins of HIV-1, especially the products of the gag gene.

High prevalence of serum antibodies to equine infectious anemia virus reverse transcriptase

The immunogenicity of the equine infectious anemia virus (EIAV) reverse transcriptase (RT) was examined by immunoblot assay with recombinant EIAV RT. All of the 19 sera from EIAV-infected horses tested contained antibodies that recognized EIAV RT and directly inhibited the polymerase activity of the enzyme. An examination of sera obtained sequentially from two experimentally infected animals revealed that anti-RT antibodies arise early in infection and increase in level. The appearance of the antibodies correlated with progression toward the asymptomatic period of infection.

A non-radioisotopic reverse transcriptase assay using biotin-11-deoxyuridinetriphosphate on primer-immobilized microtiter plates

We developed a non-radioisotopic (non-RI) reverse transcriptase assay (RTA). The reverse transcriptase (RT) incorporates biotin-11-deoxyuridine-triphosphate (bio-dUTP) using a poly(rA) template hybridized with oligo(dT) primer that is immobilized on the surface of a 96-well microtiter plate. This assay is thus semi-automated by adapting it to an ELISA testing format. The incorporation of bio-dUTP was enhanced by adding cold dTTP to the reaction mixture, optimally in a molar ratio 4:1 (dTTP:bio-dUTP). This non-RI RTA is more sensitive than the conventional RI assay for the detection of purified Rous-associated virus 2 (RAV-2) and of human immunodeficiency virus type 1 (HIV-1) lysate. Because of its simple procedure, higher sensitivity and non-use of RI materials, the assay can be utilized not only for virological studies but also for routine safety screening of biological products for retroviral contamination.

Inhibition of heat inactivation of reverse transcriptase of human immunodeficiency virus type 1 by seropositive sera

The reverse transcriptase (RT) activity of a lysate of human immunodeficiency virus type 1 (HIV) was almost completely inactivated by incubation at 56 degrees C for 20-30 min. The heat-inactivation of RT in the virus lysate or purified RT was partially inhibited in the presence of some human sera or plasma containing antibodies against HIV. The IgG fraction purified from the seropositive sera was responsible for stabilization of RT upon heat inactivation. This is a new assay system for detection of antibodies against RT.

B cell responses to HIV and the development of human monoclonal antibodies

In this review B cell responses in HIV-infected individuals are summarized together with the techniques used to date to produce human monoclonals to HIV and the properties of these antibodies. Profound disturbances in B cell responses are apparent both in vivo and in vitro. While there is evidence in vivo of marked polyclonal B cell activation, primary and secondary antibody responses are impaired. Similarly these cells exhibit spontaneous immunoglobulin secretion upon in vitro culture but do not readily respond to B cell mitogens and recall antigens including HIV. Furthermore, certain of these defects can be reproduced in normal B cells in vitro by incubation with HIV or HIV coded peptides. Individuals infected with HIV develop antibodies to HIV structural proteins (e.g. p17, p24, gp41 and gp120) and regulatory proteins (e.g. vif, nef, RT). Autoantibodies against a number of immunologically important molecules are also frequently observed. The anti-HIV antibodies are predominantly of the IgG1 isotype and exhibit a variety of effects on the virus in vitro. To date, using conventional immortalization strategies, an appreciable number of human monoclonals to HIV have been developed. These have been specific for gp41, gp120 and gag with antibodies of the former specificity predominating. The majority of these antibodies have been of the IgG1 isotype. Only a small number of the antibodies neutralize virus in vitro and most of these react with gp120. The neutralizing antibodies recognize conformational and carbohydrate epitopes or epitopes in amino acid positions 306-322. The predominant epitopes recognized by the anti-gp41 antibodies were in amino acid positions 579-620 and 644-662. A high percentage (congruent to 25%) of these antibodies enhance viral growth in vitro. The problems relating to the production of human monoclonals to HIV are discussed together with strategies that could be used in the future.

HIV-1 reverse transcriptase inhibiting antibody titer in serum: relation to disease progression and to core-antibody levels

A new assay for detecting inhibition of reverse transcriptase activity (the RT-i REA) was developed. This assay was standardized for screening serum samples for reverse transcriptase inhibiting antibodies (RT-iAb). High specificity (100%) and sensitivity (greater than 98%) were achieved with samples from HIV-negative individuals and HIV-infected individuals. The RT-i REA was also used in a study of the titers of RT-iAb in serum samples obtained from 33 HIV-infected homosexual men. The results confirmed the relation between decreasing RT-iAb levels and progression to late stages of the disease. Furthermore, a falling RT-iAb titer was observed in 14 of 15 individuals experiencing periods of severe clinical symptoms attributed to HIV-activity. In 7 of the patients the decline in RT-iAb titer began prior to severe clinical symptoms. The fall in RT-iAb titer also correlated with a reduction in core Ab level. The core Ab level has previously been reported to be a disease progression marker with considerable prognostic value. However, whereas all patients were positive for RT-iAb, 8 of the 33 patients did not have detectable core Ab. The use of RT-iAb titer as a marker of disease progression is discussed.

HIV reverse transcriptase inhibiting antibodies detected by a new technique: relation to p24 and gp41 antibodies, HIV antigenemia and clinical variables

A new assay for HIV reverse transcriptase activity inhibiting antibodies (RTI-ab) was used for the analysis of a large collection of sera sampled before and after confirmation of HIV infection. In this assay HIV-RT was preincubated with diluted serum, after which residual RT activity was determined by a technique using a template coupled to macrobeads and 125I-lodo-deoxyuridine-triphosphate as the tracer-substrate. Of the 936 sera analysed, 818 were found positive for RTI-ab, and 824 were positive in Western blot (Wb). The prevalence of RTI-ab compared to Wb was therefore 99.3%. The corresponding figure for 930 sera analysed for envelope-ab, i.e., gp41-ab, was 823 positive, and of these 930 sera 815 were Wb positive, giving a comparative prevalence of 101%. In contrast, only 678 samples of 993 analyzed for core ab, i.e., p24, were positive, giving a prevalence of 77.0% as 880 of these samples were Wb positive. Thus, RTI-ab was as prevalent as gp41-ab, and although the analyses of RTI-ab amounts in different stages showed decreasing levels in stage IV compared to stages II or III, all of the sera except 1 were found positive in stages III and IV. Further, it was found that both the few RTI-ab negative samples in stage II and the few RTI-ab positive samples among Wb negative sera were sampled in connection with seroconversion. The specificity of the RTI-ab assay was 100% in a test of 200 serum samples from HIV negative blood donors. It was concluded that RTI-ab analyses can be made highly sensitive and specific and useful for studies of HIV infection.

Laboratory diagnosis of HIV infection

Laboratory diagnosis of human immunodeficiency virus (HIV) infection is complicated by absence of data on sensitivity, specificity and predictive value of the various tests as they apply to children. The presence of maternal anti-HIV passively transmitted across the placenta also confounds diagnosis. The authors review currently available data on the detection of HIV, HIV genome, and HIV gene products, as well as the diagnostic value of detecting serologic and cellular responses to HIV in infants and children.

Comparison of different methods for detecting human immune deficiency virus in human immunodeficiency virus-seropositive hemophiliacs

Since the detection of antibodies against the human immune deficiency virus (HIV) does not definitely prove HIV infection in hemophiliacs, virus detection was attempted by virus isolation from the peripheral blood monocytes (PBL), by demonstration of p24 antigen and decline of p24 antibody, and by detection of viral DNA by the polymerase chain reaction (PCR). Virus isolation was optimized by immediate coculture of PBL and by replacement of the reverse transcriptase test by the p24 antigen test, whereas the elimination of CD8+ lymphocytes proved to be unnecessary. Virus detection was dependent on the clinical stage of the illness. Virus isolation in 70 of 211 patients (33%) was more sensitive than detection of p24 antigen or decline of p24 antibody. PCR was performed in 25 patients and indicated infection in all of 15 isolation-positive cases and in 6 of 10 patients from whom virus was not isolated. Changes from negative to positive virus culture and from a weakly fusiogenic to a highly fusiogenic isolate were often accompanied by a progression of the disease. The results suggest that reactivation of HIV occurs when immune deficiency has become manifest. Apparently virus isolation detects only the virus already reactivated in vivo, whereas the PCR may also detect latent virus.

Serum capacity to inhibit reverse transcriptase in vitro distinguishes HIV-1 infection from HIV-2 or SIV infection

The inhibition of HIV-1 and SIV reverse transcriptase by human and rhesus macaque serum positive for HIV-1 or HIV-2/SIV antibodies was studied. The domain to which reverse transcriptase-inhibiting antibodies were elicited appeared to be highly antigenic. A total of 67% (48 of 72) of individuals had HIV-1 reverse transcriptase-inhibiting (RTI) antibodies 1 year after seroconversion for HIV-1, 90% (9 of 10) of HIV-2 antibody positive persons had SIV RTI antibodies, and all four experimentally SIV-infected rhesus macaques developed SIV RTI antibodies. Low cross-reactivity between HIV-1 and HIV-2/SIV RTI antibodies was observed. Of 10 HIV-1 RTI sera, 2 reduced SIV RT activity by more than 50% (mean reduction 85 versus 24%). Only 1 of 9 SIV RTI human sera reduced HIV-1 RT (mean reduction 74 versus 25%). This serum, however, showed a shared reactivity against both HIV-1 and HIV-2. These results indicate that the HIV-1 domain inducing RTI antibodies is antigenically different from the HIV-2/SIV domain.

Cross-sectional study of reverse transcriptase-inhibiting antibody as a marker of acquired immune deficiency syndrome

A cross-sectional study of 128 individuals infected with human immunodeficiency virus type 1 (HIV-1) was conducted to determine the correlation of reverse transcriptase-inhibiting (RTI) antibody to clinical disease. Thirty-two individuals were studied in each of four clinical groups: asymptomatic individuals, those with persistent generalized lymphadenopathy, those with acquired immune deficiency syndrome (AIDS)-related complex, and those with AIDS. Our study showed that 78% of asymptomatic individuals, 53% of those with persistent generalized lymphadenopathy, 50% of those with AIDS-related complex, and only 25% of those with AIDS have RTI antibody. Concurrent measurement of measles antibody level was used as an indicator of the immune status of these individuals. Measles antibody did not decline in persons with clinical disease, but asymptomatic individuals had lower antibody titers, possibly due to hypergammaglobulinemia associated with advanced HIV infection. These results indicate that more HIV-infected asymptomatic individuals than symptomatic individuals have RTI antibody. This suggests either that the RTI antibody level decreases with the progression of disease in HIV infection or that symptomatic individuals do not produce RTI antibody. The presence or absence of RTI antibody can thus be used as a marker of advanced disease.

Expression of human immunodeficiency virus type 1 (HIV-1) gag antigens on the surface of a cell line persistently infected with HIV-1 that highly expresses HIV-1 antigens

MT-4 cells persistently infected with human immunodeficiency virus type 1 (HIV-1) (MT-4/HIV-1) were recently isolated (K. Ikuta, C. Morita, M. Nakai, N. Yamamoto, and S. Kato, Japan. J. Cancer Res. (Gann), 79, 418-423, 1988). Mouse hybridoma cell clones producing monoclonal antibodies (MoAbs) to HIV-1 gag p24 and p18, and pol reverse transcriptase (RT) were isolated by using this MT-4/HIV-1 cell line for the screening of MoAb production by the immunofluorescence (IF) test. By indirect IF tests of acetone-fixed cells with these MoAbs, the IF intensities in MT-4/HIV-1 cells were found to be higher than those in the other HIV-1 infected cells, such as MOLT-4/HIV-1, HL-60/HIV-1, and U937/HIV-1 cells. Cell surface expression of the HIV-1 gag p24 and p18 antigens examined by IF and radioimmune techniques with these MoAbs revealed the p24 and p18 antigens to be expressed strongly on the cell surface of MT-4/HIV-1 cells and faintly on the cell surface of MOLT-4/HIV-1 cells, respectively. However, monoclonal antibody isolated in the present study failed to detect pol RT antigen on the surface of MT-4/HIV-1 cells. These results indicate that the gag p24 and p18 antigens are expressed, at least in part, on the surface of HIV-1-infected cells.

Efficient primary isolation of human immunodeficiency virus

A highly-sensitive and efficient culture technique for human immunodeficiency virus type-1 (HIV-1) is described; HIV-1 was recovered from the lymphocytes of 44 (94%) antibody-seropositive healthy or symptomatic individuals. The reductions in the requirements for both the reagent volume and the number of patients' lymphocytes, together with an increased efficiency, has made this HIV-1 culture system more practical for diagnostic virology laboratories.

Isolation of human immunodeficiency virus from peripheral blood lymphocytes stored in various transport media and frozen at -60 degrees C

The peripheral blood lymphocytes from 48 heparinized blood specimens from human immunodeficiency virus (HIV) antibody-positive individuals were divided into two aliquots. One aliquot was reconstituted in one of the following five media. Medium 1 consisted of tryptose broth with 0.5% gelatin; medium 2 consisted of RPMI 1640 containing 10% fetal bovine serum (FBS); medium 3 consisted of RPMI 1640 containing 20% FBS, Polybrene, interleukin 2, and anti-alpha interferon; medium 4 consisted of medium 2 plus 10% dimethyl sulfoxide (DMSO); and medium 5 consisted of medium 3 plus 10% DMSO. Lymphocytes were stored in these five media at -60 degrees C. The other aliquot of cells was stored at -190 degrees C in RPMI 1640 containing 50% FBS and 10% DMSO. After 1 week, both aliquots were cocultivated with phytohemagglutinin-stimulated uninfected peripheral blood lymphocytes, and presence of HIV was detected by the reverse transcriptase test. Storage in medium 1, 2, or 3 did not result in satisfactory isolation rates, but storage at -60 degrees C in medium 4 or 5 gave equal or better isolation rates than did storage at -190 degrees C. Inactivation of HIV by freezing of the cells without DMSO correlated with high antibody titers to core and polymerase proteins as measured by Western (immuno-) blotting.

Immunoglobulin preparations for HIV-infected patients

Patients with the acquired immunodeficiency syndrome (AIDS) suffer from a deficiency of cellular immunity. However, some HIV-infected children and adults suffer from recurrent upper respiratory tract infections suggestive of a failure to synthesise specific antibodies, despite the hypergammaglobulinaemia that is present. Intravenous immunoglobulin (IV IgG) appears to benefit HIV-infected children with recurrent infections, in doses similar to those used for treating patients with primary hypogammaglobulinaemia. In some HIV-infected adults, IV IgG also appears to reduce bacterial respiratory infections but the treatment schedules remain to be defined. In patients with life-threatening bleeding due to immune thrombocytopenic purpura associated with HIV infection, high dose IV IgG treatment (1-2 g/kg) also increases platelet counts but unlike other therapies for ITP, is not immunosuppressive and has no other serious adverse effects. It is likely that over the next few years, specific anti-HIV preparations will be evaluated. Neutralising antibody has been demonstrated in HIV-infected patients and a specific antibody preparation against HIV might either prevent HIV infection after initial exposure to the virus or slow the progression of HIV-related disease. However, the development of a specific, effective, neutralising anti-HIV immunoglobulin preparation (whether polyclonal or monoclonal) will require information about which HIV antigens elicit protective immunity and the role played by neutralising antibody in HIV-related disease.