Dextrin Sulphate and Fucoidan are Potent Inhibitors of HIV Infection in vitro

Two sulphated polysaccharides, fucoidan (a derivative of seaweed) and the newly synthesised dextrin sulphate, were tested for their ability to inhibit human immunodeficiency virus (HIV) infection in vitro in comparison to dextran sulphate and azidothymidine. They were found to be potent inhibitors of diverse strains of HIV-1 in a variety of human cell lines and in peripheral blood lymphocytes (PBL) using a range of assays, including cell-free and cell-to-cell spread of infection. The drugs did not adversely affect cell proliferation or protein metabolism of PBL. As dextrin sulphate is less potent than dextran sulphate in prolonging thrombin-induced fibrin clotting time, it merits further development as an antiviral agent.

An improved algorithm for determining HIV type 1 subtypes in a primary laboratory in Uganda

A pilot study was undertaken with the objective of developing a simple, economical, and efficient algorithm through which to subtype HIV-1 in a large epidemiological cohort study in Uganda. A peptide enzyme immunoassay (PEIA) employing both V3 and gp41 regions and a heteroduplex mobility assay (HMA) were evaluated in comparison with DNA sequencing. Of 146 samples selected, 115 (79%) were successfully sequenced. Taking sequence data as the "gold standard," other assays were compared with these data. The HMA correctly identified 95 (83%) of the samples, and only 1 sample was wrongly identified. The V3 PEIA alone and in combination with gp41 peptides correctly identified 76 and 78% of the samples, respectively; however, the number of wrongly identified samples was four times less with the combination compared with V3 peptides alone (4 versus 16%). The sensitivity, specificity, and positive and negative predictive values for serotype A and D samples were greater for the combination than V3 peptides alone. We have described a new algorithm to segregate subtypes A and D. This algorithm uses the two peptide assays followed by HMA and then DNA sequencing for untypable samples, giving an accuracy of 95% at a cost of 37 and 21% for consumables compared with subtyping all the samples by HMA or DNA sequencing, respectively. This proposed approach is suitable for epidemiological studies in Uganda and other regions with a predominance of A and D subtypes.

Characterization of sera from subjects infected with HIV-1 subtypes B and E in Thailand by antibody binding and neutralization

The range and specificity of the humoral immune response to HIV-1 subtypes B and E was investigated in Thai samples. Sera from HIV-1-positive subjects, consisting of subtypes B (n = 24) and E (n = 138), were characterized in relation to the neutralization of primary isolates and T-cell line-adapted (TCLA) strains and binding to monomeric gp120, the CD4/gp120 binding site (BS), and V3 peptides. A subtype-specific pattern of antibody binding was observed with the exception of the CD4/gp 120MN BS. Neutralization of TCLA strains (n = 4) was strongly type-specific (p = .002); however, neutralization of primary isolates (n = 8) was weak and group specific. Thus, the subtype specificity of B and E sera in the neutralization of TCLA strains, but not primary isolates, supports the dominance of the V3 region in TCLA virus neutralization but does not support the distinction of subtypes B and E as discrete neutralization serotypes in Thailand.

Lack of correlation between V3-loop peptide enzyme immunoassay serologic subtyping and genetic sequencing

OBJECTIVE

To compare the performance of V3-loop peptide enzyme immunoassay (PEIA) methodologies from four different laboratories for subtyping HIV-1, and to determine the causes for the lack of correlation between V3-loop PEIA serotyping and subtyping by sequencing.

MATERIALS AND METHODS

Synthetic peptides derived from the amino-acid consensus sequences of the V3-loop of group M strains representing genetic subtypes A-F as well as reference strains were evaluated in PEIA by four different laboratories for their ability to accurately determine the subtype in a panel of 85 sera obtained from persons infected with known HIV-1 subtypes (28 subtype A, 34 subtype B, four subtype C, 10 subtype D, seven subtype F, one each of subtype H and G). Furthermore, the V3 loop of the corresponding virus was compared with the V3 loop of the peptides used in PEIA.

RESULTS

The correlation between HIV-1 subtyping by sequencing and V3-loop PEIA from the different laboratories varied considerably for the different HIV-1 subtypes: subtype A (46-68%), B (38-85%), C (75-100%), D (29-50%), and F (17-57%). A 70% agreement between PEIA and sequencing subtypes was observed for samples with the concordant presence of the same octameric sequences in the V3 loop of the virus and the V3 loop of the peptide used in PEIA; however, only 42% of specimens with different V3-loop octameric viral and peptide sequences yielded concordant results in V3-loop serotyping and genetic subtyping.

CONCLUSION

Our results indicate that V3-loop PEIA methodologies used in different laboratories correlate poorly with genetic subtyping, and that their accuracy to predict HIV-1 subtypes in sera of Belgian individuals infected with different HIV-1 subtypes (A, B, C, D, F, G and H) vary considerably. The poor correlation between serotyping and genetic subtyping was partly due to the simultaneous occurrence of subtype-specific octameric sequences at the tip of the V3 loop of viruses belonging to different genetic subtypes.

A sudden epidemic of HIV type 1 among injecting drug users in the former Soviet Union: identification of subtype A, subtype B, and novel gagA/envB recombinants

The former Soviet Union republics have experienced an explosive human immunodeficiency virus type 1 (HIV-1) epidemic among injecting drug users (IDUs), consisting mainly of subtype A viruses originated from a point source (Bobkov et al.: AIDS Res Hum Retroviruses 1997;13:1195-1201). To determine whether new HIV-1 subtypes have entered the IDU population, 46 samples derived from IDUs in Russia (n = 39) and the Ukraine (n = 7) were genotyped by heteroduplex mobility assay (HMA). It was shown that 83% of IDU HIV-1 strains found in both countries belong to genetic subtype A. However, env subtype B was also found in 17% of cases. The sequence data showed a marked intrasubtype homogeneity of HIV-1 (the average means of interpatient genetic distance were 1.1 and 1.7% [in the gag gene] or 1.8 and 2.3% [in the env gene] for subtype A and subtype B, respectively), confirming the hypothesis of a point source of virus for each subtype variant. Moreover, recombinant gagA/envB variants originating from those two strains were also found in two samples collected in the Kaliningrad region of Russia. In conclusion, our results suggest that two strains of HIV-1 belonging to different genetic subtypes, A and B, as well as gagA/envB recombinants between genomes of these strains, are now circulating simultaneously among IDUs in the former Soviet Union.

Serotyping of HIV type 1 infections: definition, relationship to viral genetic subtypes, and assay evaluation. UNAIDS Network for HIV-1 Isolation and Characterization

V3 serotyping refers to a system based on binding of antibody in patient sera to V3-loop peptides derived from HIV-1 env genetic subtypes. The V3x serotype represents reactivity of serum from an HIV-1-infected patient (regardless of viral genetic subtype), which reacts preferentially to a V3 peptide derived from the X subtype sequence. We have classified HIV-1 serotypes, determined the relationship between the HIV-1 V3 serotypes and viral genetic subtypes in a large study (n = 125), and evaluated the performance of three different V3 peptide-binding assays. Seven HIV-1 V3 serotypes were identified: A, B, B-Br, B-Th, C, D, and E. Serotypes B-Br and B-Th represent sera that react specifically to peptides derived from Brazilian B (B-Br, GWGR) and Thai B (B-Th, GPGQ) strains. The HIV-1 V3 B, C, and E serotypes correlated closely with their viral env genetic subtypes; 19-26 of 32 B sera (59-79%), 3-4 of 4 C sera (75-100%), and 19-22 of 23 E sera (83-96%) were identified as serotypes B, C, and E, respectively. In contrast, two major V3 serotypes were classified in A sera: A (14-18 of 36 [40-50%]) and C (12-19 of 36 [33-54%]). Similarly, two major V3 serotypes were classified in D sera: B (6-10 of 20 [30-50%]) and D (9-12 of 20 [45-60%]). Serotyping of subtype E sera showed the best concordance with genetic subtypes by all assays. Overall, HIV-1 V3 serotyping produced consistent results among three laboratories. However, HIV-1 V3 serotypes do not distinguish all HIV-1 genetic subtypes. The relative biological significance of the V3 serotypes remains to be elucidated.

HIV type 1 V3 serotyping of Tanzanian samples: probable reasons for mismatching with genetic subtyping

HIV-1 V3 serotyping is used to classify immunodeficiency viruses on the basis of antibody binding to V3 peptides derived from env genetic subtypes. Although it shows a reasonable overlap, it has been reported to be distinct from viral genetic subtypes. The aim of this study is to determine the feasibility of HIV-1 serotyping to predict genetic subtypes in an East African setting, where multiple HIV-1 subtypes have coexisted for many years. HIV-1 genetic subtypes of 86 AIDS patients in Mbeya Town, southwest Tanzania, were determined, using env nucleic acid sequencing as the basis for comparison. Those data were compared with V3 serotyping results obtained by four different methodologies. Four HIV-1 genetic subtypes were identified, including A (25, 29%), C (47, 55%), D (13, 15%), and G (1, 1%). The sensitivity and specificity of those serotyping assays varied considerably: sensitivity for genetic subtype A (40-48%), C (52-96%), and D (9-31%); and specificity for genetic subtype A (77-95%), C (46-63%), and D (97-100%). We further tried to identify reasons for the discrepancies between serotyping results and genetic subtypes. By means of logistic regression analysis three amino acid residues within the V3 loop (positions 12, 13, and 19; V, H, and A for serotype A, I, R, and T for serotype C) were found to be most important for antibody binding; a deviation from the subtype-specific amino acids was highly related to mismatched results. In addition, we have shown that phenetic analysis of V3 amino acid sequence data could be used to predict the majority of V3 serotypes (93-94%). Our data demonstrated that for the majority of specimens HIV-1 V3 serotyping results closely match the subtype of the analyzed sample as revealed by the V3 loop amino acid sequence. However, our data demonstrate that HIV-1 serotyping is not sufficiently accurate to predict genetic subtypes in Tanzania, where subtypes A, C, D, and G are circulating. This was due to highly similar amino acid sequences throughout the prevalent genetic subtypes, which caused the inability of HIV-1 V3 serotyping to differentiate subtype A from C as well as D from C. Instead, the serotyping results reflect the frequency distribution of V3 serotypes. To investigate HIV-1 genetic subtypes in population-based studies in this African setting additional or modified algorithms are needed.

Neutralization of primary and T-cell line adapted isolates of human immunodeficiency virus type 1: role of V3-specific antibodies

The role of the third variable domain (V3) of gp120 in the neutralization of primary and T-cell line adapted (TCLA) strains of human immunodeficiency virus type 1 (HIV-1) by serum from HIV-1-infected individuals was investigated. A primary virus isolate, M2424/4, when adapted to H9 cells, was more sensitive to neutralization on MT2 cells than the same stock passaged in PBMC. Neutralization of the PBMC-passaged stock by V3-specific MAbs was abrogated by addition of V3 (MN) peptide. However, exogenous V3 (MN) peptide failed to reduce the neutralization of this isolate on PBMC, or MT2 cells, by high titre anti-HIV-1 polyclonal human sera in contrast to the extensive reduction of neutralization by the same sera on MT2 cells using the prototype MN strain (4- to > or = 24-fold) and the TCLA M2424/H9 isolate (2- to 8-fold). These results indicate that the neutralization of primary virus isolates by serum from HIV-1-infected individuals is not significantly mediated by V3-specific antibodies.

A pilot phase II study of the safety and immunogenicity of HIV p17/p24:VLP (p24-VLP) in asymptomatic HIV seropositive subjects

The aim of this phase II study was to evaluate the safety, immunogenicity and tolerability of the yeast-derived virus-like particle immunogen, Ty.p24.VLP (p24-VLP), in HIV-antibody-positive asymptomatic volunteers. Fifteen informed and consented volunteers, with p24 Antibody titres >1/100, p24 Antigen <20 pg/l, and CD4>350 x 10(9)/l were enrolled. Five were immunized with aluminium hydroxide placebo, five with 25 microg, and five with 100 microg p24-VLP in Alum adjuvant at weeks 0 and 4 by the intramuscular route. Patients were followed for 16 weeks post vaccination and the main outcome assessments were CD4 and CD8 lymphocyte counts, p24 antigen and antibody, Ty antibody and quantitative viral cultures. No serious adverse events were observed in any of the groups. There were increases in CD4 counts in the treated groups but not in the controls, although these changes were not statistically significant. There were no significant intrasubject or intergroup changes in the other parameters, such as p24 antigen and antibody. No pattern of change in plasma viraemia was detected, and most cultures were negative. Therefore we conclude that p24-VLP immunizations of 25 microg and 100 microg are well tolerated, and the CD4 changes are encouraging, but higher doses and larger numbers are required to see if there are significant humoral or cellular responses, and extended phase II studies are now in progress.

An HIV type 1 epidemic among injecting drug users in the former Soviet Union caused by a homogeneous subtype A strain

Epidemiological data have demonstrated rapid growth of HIV-1 infections among injecting drug users (IDUs) in the Ukraine and Russia, during 1996. Here we describe the results of genetic analysis of isolates derived from 12 HIV-1-infected IDUs in different sites of Russia and the Ukraine. The blood samples were taken within a 1- to 2-month period after the first HIV-1-positive test. The results of the heteroduplex mobility assay as well as gag/env phylogenetic analysis reveal that all sequences belong to gag/env genetic subtype A. Moreover, interpatient genetic distances between the nucleotide sequences encompassing the C2-V3, the V4-V5, and p17-encoding regions within this group were low (the average means were 0.9, 1.3, and 0.4%, respectively). These data show a marked homogeneity of HIV-1, probably spreading during primary infection. It is possible that the current epidemic of subtype A HIV-1 among IDUs in the former Soviet Union is caused by a point source exposure.

Genetic heterogeneity of HIV type 1 in Russia: identification of H variants and relationship with epidemiological data

HIV-genetic subtypes were analyzed in 130 subjects from the Russian Federation, by the HMA technique. Six subtypes were identified in heterosexuals, including A, B, C, D, G, and H; however, homosexual men were infected predominantly with the B subtype (33 of 35). The subtype A isolates were found in population of intravenous drug users. HMA successfully identifies 128/130 DNA samples; the phylogenetic analysis of the V1/V5 gp120 encoding region derived from another two samples demonstrated that these isolate belong to subtype H.

No evidence of antibody to human foamy virus in widespread human populations

The first human foamy virus (HFV) to be described was isolated from nasopharyngeal carcinoma tissue from a Kenyan patient. Early seroepidemiology concluded that there was a significant infection rate, particularly among Africans. Awareness of foamy viruses as potential vectors has stimulated interest in the natural seroprevalence of HFV infection. We, therefore, investigated the prevalence of HFV infection in more than 5000 human sera collected from diverse populations. To maximize the chances of including the major antigenic epitopes, recombinant proteins derived from the HFV gag and env genes divided into three (the 5' amino terminal, the 3' carboxy terminal, and an internal overlapping region) were used as antigens in an ELISA. In contrast to most other seroepidemiological investigations of HFV infection, highly reactive sera identified by ELISA were subjected to further analysis by additional serological assays and, where PBMCs were available, PCR. None of the serum samples were confirmed as positive. It is worth noting that with our ELISA, the highest level of serum reactivity to HFV was found in subjects from Pacific islands (17%), and in Central Africa (34% in Malawi), areas previously cited as having a high level of HFV infection. Taken together with sequence analysis endorsing the phylogenetic closeness of HFV to SFV-6/7, these data strongly suggest that HFV is not naturally found in the human population.

Identification of an env G subtype and heterogeneity of HIV-1 strains in the Russian Federation and Belarus

OBJECTIVE

To identify HIV-1 envelope sequence subtypes in infected individuals from the Russian Federation and Belarus.

PATIENTS

A cohort of children infected after exposure to non-sterile needles during the 1988-1989 HIV-1 epidemic in southern Russia (n = 20) and HIV-1-seropositive individuals from Russia (n = 1) and Belarus (n = 7) infected via sexual transmission.

METHODS

DNA samples derived from peripheral blood mononuclear cells were analysed for their HIV-1 genotypes by the heteroduplex mobility assay (HMA). The 1.3 kilobase-pair env gene fragments encoding a portion of gp120 were amplified by nested polymerase chain reaction, cloned and sequenced. The env sequences derived from these patients were aligned and phylogenetic neighbour-joining and maximum parsimony-derived trees generated.

RESULTS

The env sequences derived from eight individuals infected in Russia and Belarus belong to subtype A (one), B (four), C (two), and D (one). Sequences derived from children, infected during parenteral manipulations in southern Russia, and one mother were closely related, but highly divergent, as a group, from all prototypic strains (genetic divergence, 17.2-22.9%). However, they clustered together with env sequences of the V1525 and LBV21-7 isolates from Gabon, recently described to be members of a new HIV-1 env subtype G.

CONCLUSION

Extensive heterogeneity of HIV-1 subtypes was evident in the Russian Federation and Belarus. Our data also support the existence of an HIV-1 env genetic subtype G, and such isolates are now apparently present on both the African and European continents. These variants were identified through V3 peptide enzyme-linked immunosorbent assay screening and subsequent HMA analysis. The combination of these techniques represents a model for screening HIV variants within a large population.

Serotyping HIV type 1 by antibody binding to the V3 loop: relationship to viral genotype. WHO Network for HIV Isolation and Characterization

We have investigated whether peptides representing the HIV-1 principal neutralization domain (V3) can be used as antigens in antibody-binding assays to predict the genotypes of the subjects' virus. Serum samples collected from HIV-1-infected subjects from the four WHO-sponsored vaccine evaluation sites (Uganda, Rwanda, Thailand, and Brazil) were characterized by antibody binding to a panel of synthetic V3 peptides that were derived from the consensus sequences of the V3 region of the HIV-1 subgroups according to the env phylogenetic analysis (A-E). An indirect V3 peptide-binding assay was used for primary screening, and a V3 peptide antigen-limiting ELISA was then used as a secondary assay to discriminate cross-reactivity if the screening assay was equivocal. In general, V3 peptide serology could predict HIV-1 genotypes. In sera for which the genotype of the virus was known, peptide assays could predict the correct genotype in approximately 90% of cases for genotypes A, B, C, and E; Ugandan sera of genotype D were more broadly reactive. There was considerable serological cross-reactivity between some HIV-1 genotypes, in particular between A and C, and, to a lesser extent, B and D subtypes. Owing to polymorphism at the crown of the V3 loop, an additional B peptide (B') was required to type Brazilian B genotype sera. These simple assays may help facilitate the determination and distribution of HIV-1 genotypes circulating in populations.

Molecular epidemiology of HIV-1 in the former Soviet Union: analysis of env V3 sequences and their correlation with epidemiologic data

OBJECTIVE

To investigate the HIV-1 V3 sequence diversity in the former Soviet Union in 30 subjects infected with HIV-1 via different modes of transmission.

PATIENTS

A cohort of children infected after exposure to nonsterile needles during the epidemic in 1988-1989 in southern Russia (Elista, n = 12 and Rostov-on-Don, n = 10), and eight HIV-seropositive subjects from Belarus (Minsk), infected via sexual (n = 7) and parenteral (n = 1) infection.

METHODS

The HIV-1 V3 encoding region was amplified by nested polymerase chain reaction on DNA of primary peripheral blood mononuclear cells collected from the study subjects and then cloned and sequenced.

RESULTS

The alignment of 127 V3 sequences from 22 patients in the cohort group demonstrated common consensus sequences in both the Elista and Rostov samples. The average means of interperson variation were 5.9 and 6.6% in Elista and Rostov subjects, respectively, and comparable to the mean intraperson variation. The average mean interperson variation between nucleotide sequences of HIV patients infected through sexual transmission was considerably higher (14.9%).

CONCLUSION

V3 sequence analysis confirms the epidemiologic data which support the transmission of HIV-1 in children from a single source, and suggests the infection of a mother from her parenterally infected child. Furthermore, the genetic variability of HIV-1 V3 in the noncohort group was particularly divergent indicating the heterogeneity of the virus circulating in the former Soviet Union.

Immunization of human HIV-seronegative volunteers with recombinant p17/p24:Ty virus-like particles elicits HIV-1 p24-specific cellular and humoral immune responses

OBJECTIVE

To evaluate the immune response to HIV-1 p24 generated in vivo by p17/p24:Ty virus-like particles (p17/p24:Ty-VLP) by examining the lymphoproliferative and antibody (Ab) responses to HIV-1 p24, as well as Gag-specific cytotoxic T lymphocytes (CTL), in HIV-seronegative volunteers immunized with hybrid p17/p24:Ty-VLP.

DESIGN AND METHODS

Sixteen HIV-seronegative volunteers were immunized with p17/p24:Ty-VLP at two dose levels (100 or 500 micrograms) and monitored for the following 48 weeks for production of anti-p24 and anti-p17 Ab, in vitro lymphoproliferative responses to HIV-1 p24 and p17, and in vitro CTL responses to HIV-1 Gag.

RESULTS

Twelve out of the 16 volunteers had significant p24-specific proliferative responses, with volunteers on the higher dose schedule exhibiting earlier proliferative responses than those on the lower dose schedule. Proliferative responses in both volunteer groups were similar in overall magnitude but appeared at different times during the immunization schedule. Anti-p24 Ab were detected in six out of the nine individuals in the lower dose group and in five out of the seven in the higher dose group. There was a good correlation between the presence of p24-specific Ab and the detection of lymphoproliferative responses to the p24 protein in peripheral blood mononuclear cells isolated from the same individuals. Anti-p17 Ab were detected in five volunteers. No Gag-specific CTL responses were detected.

CONCLUSION

We conclude that hybrid HIV-1 p17/p24:Ty-VLP are capable of inducing both cellular and humoral immunity to HIV-1 Gag p17 and p24 components and are worthy of further study as a potential HIV immunotherapeutic.

Identification of human immunodeficiency virus type 1 subtypes and their distribution in the Commonwealth of Independent States (Former Soviet Union) by serologic V3 peptide-binding assays and V3 sequence analysis

Serologic V3 loop peptide-binding assays have been used to predict divergent human immunodeficiency virus type 1 (HIV-1) strains from the Commonwealth of Independent States (former Soviet Union) that have been subsequently confirmed by sequencing of the V3 region. Initial screening was done by MN V3 peptide binding; 12 parenterally infected HIV-1-positive subjects from Elista and Rostov (group 1) with low-titer MN binding and 6 heterosexually infected HIV-1-positive adults from Byelorussia (group 2) with high-titer MN binding were selected. A consensus sequence from the Elista and Rostov areas was generated; a corresponding 14-mer peptide was synthesized and used in an indirect ELISA to screen sera from 392 individuals from diverse geographic areas. Reactivity to the consensus peptide was 82% in subjects from the homologous areas and 11%-38% in other areas. Antibody binding to a panel of synthetic V3 peptides may be used to predict the presence of diverse strains of HIV-1 within virally heterogenous populations.

Development of HIV-1 group-specific neutralizing antibodies after seroconversion

OBJECTIVE

To study the induction of group-specific (gs) neutralizing antibodies to HIV-1 after seroconversion.

DESIGN AND METHODS

Serum samples taken sequentially from seven Dutch homosexual men and four British haemophiliacs (anonymous sample, therefore sex not known) before and after seroconversion were tested for neutralizing antibodies effective against five diverse HIV-1 strains. Strains of HIV-1 tested included isolates from the United States, Europe and Africa.

RESULTS

The gs neutralizing antibody response varied between individuals. Only five of the 11 individuals studied produced detectable neutralizing antibodies to laboratory-adapted HIV-1 strains (for example, IIIB) within 32 weeks of seroconversion. Most individuals initially produced antibodies effective against US/European isolates; the response then generally broadened to include the more diverse strains, i.e., African.

CONCLUSIONS

These results suggest that the gs neutralizing target for HIV-1 is poorly immunogenic in vivo and is probably not highly conserved among diverse HIV-1 strains.

Geographic Diversity of Human Immunodeficiency Virus Type 1: Serologic Reactivity to env Epitopes and Relationship to Neutralization

The antibody recognition of the major neutralization epitopes of human immunodeficiency virus type 1 (HIV-1) in 829 HIV-1-seropositive subjects from North America (106), Europe (241), Africa (342), and Asia (100) was investigated. Peptides derived from diverse published V3 loop sequences were used as antigen, and serum reactivity was detected by sensitive ELISAs. Antibody binding to peptides derived from the V3 loop sequence of HIV-1 isolates varies considerably depending on the geographic origin of the antibody and is associated with neutralization titer against homologous isolates. Serotype reactivity to peptides may be a simple and rapid approach to investigation of HIV-1 env diversity worldwide and may assist the choice of immunogen for development of future AIDS vaccines.

Comparative humoral responses to HIV-1 p24gag and gp120env in subjects from East Africa and the UK

We compared 1616 sera from HIV-1-infected subjects and matched HIV-negative local controls in Uganda, Kenya and the UK. Sera were screened for specific antibody to HIV-1 p24 Gag and gp120 Env proteins and for p24 antigenaemia. In contrast to the UK, the majority of African HIV-1-infected subjects maintained detectable anti-p24 antibodies. However, lower reactivity of anti-p24 was observed in African AIDS patients, compared with those with asymptomatic HIV-1 infection. This reduction in anti-p24 reactivity with more advanced clinical stage was less marked in African HIV-1 infection than in the UK. Correspondingly, p24 antigenaemia was more common in patients with AIDS from the UK than in African patients (65 versus 4%). Reductions in anti-gp120 reactivity were observed in African AIDS patients, compared with the asymptomatic group. However, median reactivity of anti-gp120 in UK patients remained unchanged in both asymptomatic and AIDS subjects. The differences in humoral response to p24 and gp120 between Africa and the UK are semi-quantitative rather than qualitative and could be explained by initial higher antibody response to HIV-1 in African subjects.

Relation between humoral responses to HIV gag and env proteins at seroconversion and clinical outcome of HIV infection

OBJECTIVE

To study the contribution of the humoral response to HIV-I at seroconversion to disease outcome after 84 months.

DESIGN

A retrospective longitudinal study.

SETTING

Two haemophilia centres in the United Kingdom.

PATIENTS

88 Haemophiliac patients infected with HIV-I for whom sera were available from before seroconversion and in whom clinical follow up data were available.

RESULTS

Kaplan-Meier survival analysis showed a significant difference between a high titre (greater than 1600) p24 antibody response at seroconversion and prolonged time before the development of HIV related disease (p = 0.0008). In contrast, higher titres of antibody to gp120 at seroconversion (greater than 25,600) correlated with more rapid clinical deterioration (p = 0.025).

CONCLUSIONS

The first humoral response to HIV proteins at seroconversion is associated with clinical outcome; patients with an initial low titre antibody response to the gagp24 protein have a significantly faster rate of progression to CDC stage IV disease. Patients with a high titre p24 antibody response progress to AIDS more slowly, and these data provide an explanation why p24 antigenaemia is not universally detected in patients with AIDS. It is unclear whether the association between a strong initial p24 antibody response and slower progression of HIV disease is causal and if so whether it is due to viral or host factors.

Antibodies to HIV-1 nef(p27): prevalence, significance, and relationship to seroconversion

A sensitive and specific enzyme-linked immunoassay for antibodies to the human immunodeficiency virus type 1 (HIV-1) nef gene product, p27, has been developed using recombinant Escherichia coli-derived protein from the LAV-1-Bru sequence. Of 92 HIV-1 infected hemophiliacs, 72 (78%) produced anti-nef antibodies in this assay; the early appearance of anti-nef prior to full seroconversion was a rare event in this population, occurring in only one subject (approximately 1%). Anti-nef antibodies were not detected in any of 500 sera from 98 repeatedly HIV seronegative subjects who had been exposed to sexually transmitted modes of HIV infection (45 subjects) or through blood products (53 subjects). There was no significant association of titer or anti-nef antibody with protection from disease in HIV infection (p = 0.1). Although the nef protein is relatively immunogenic in natural infection, this study cannot confirm the previously reported high prevalence of anti-nef antibodies prior to seroconversion, nor the finding of anti-nef antibodies in HIV seronegative but exposed subjects.

Antibodies to a putative HIV gp41 immunosuppressive peptide, pHIVIS (583-599), do not correlate significantly with outcome in HIV infection

We have studied the prevalence of antibodies to peptides derived from the transmembrane protein of HIV, gp41. Previous work has suggested that the presence of antibodies to the gp41 peptide known as pHIVIS (env 583-599) is associated with protection from immunosuppression in HIV infection. We studied 171 sequential sera from 55 HIV-1-infected people in various clinical stages of disease. There was no significant association between antibodies to pHIVIS and clinical status in this study. Although pHIVIS has sequence similarity to the putative immunosuppressive region of the C-type oncornaviruses (p15E), antibodies to this peptide do not appear to be associated with protection from immunosuppression in natural HIV infection.

Decline of anti-p24 antibody precedes antigenaemia as correlate of prognosis in HIV-1 infection

A cohort of 84 homosexual men presenting with persistent generalized lymphadenopathy (PGL) was studied between March 1982 and March 1987. A progression rate to AIDS of 5% per year was seen in those who were infected with HIV. Certain clinical features and routine laboratory investigations were significantly associated with an increased risk of disease progression, but had only limited predictive value. Two hundred and fifty-two serial sera from 57 patients were analysed for the p24 antigen (Abbott), the principal core protein of HIV and antibody against p24 by direct enzyme-linked immunosorbent assay (ELISA). Patients who remained well retained a high titre of anti-p24 antibody compared with those who progressed to AIDS-related complex (ARC) or AIDS. HIV antigen was detectable in 40% of AIDS patients 2 years before diagnosis, but antigenaemia was preceded by loss of anti-p24 antibody by up to 18 months and preceded AIDS by up to 40 months. ARC patients tended to be negative when tested for both alpha-p24 antibody and antigen, suggesting a transitional state. Analysis of the humoral response against gag proteins appears to correlate closely with clinical status and may be an earlier and more consistent way of predicting disease progression than p24 antigenaemia, or clinical and routine laboratory investigations.

HTLV-III antibody and T-cell subset ratios in haemophiliacs and their spouses

44% of 63 British patients with either haemophilia A or B were HTLV-III antibody positive (HTLV-VIII+). HTLV-III+ was more frequent in high factor VIII concentrate users and 75% of severely affected haemophilia A patients were HTLV-III+. All eight patients who were exposed to factor IX concentrate were HTLV-III-. 17 haemophilia A patients who received only British made factor VIII concentrate (average 12,000 units/year) were HTLV-III-. Two of 63 patients had evidence of a pre-AIDS type symptom complex and both were HTLV-III+. Information from a cohort of 21 Liverpool haemophiliacs suggests that HTLV-III was first introduced into this country in 1981. OKT4/T8 ratios were abnormal in 52% of 21 patients studied but this finding was not confined to either HTLV-III+ or HTLV-III- individuals. The spouses of 14 HTLV-III+ haemophiliacs were all HTLV-III-.

AIDS and haemophilia: morbidity and morality in a well defined population

One hundred and forty-three multitransfused patients with hereditary haemostatic disorders were examined for evidence of disease related to the acquired immune deficiency syndrome (AIDS). Ninety-nine patients with severe haemophilia A were tested for anti-HTLV-III and 76 were found to be positive. All except one of these seropositive patients had received commercial factor VIII concentrates at some time. Eighteen patients with haemophilia B were tested and all were anti-HTLV-III negative. Three out of 36 sexual partners of patients with haemophilia A positive for anti-HTLV-III were also seropositive. One, who had recently received blood transfusions, had AIDS with Pneumocystis carinii pneumonia. Three patients with severe haemophilia A died from Aids. A further 30 haemophiliacs had AIDS related complex or lymphadenopathy that could be related to HTLV-III infection. There was a significant correlation between lymphadenopathy and anti-HTLV-III seropositivity. No evidence of casual spread of AIDS was found since all 68 health care staff tested were anti-HTLV-III negative, including three surgeons who regularly worked with patients positive for anti-HTLV-III. The resources devoted to counselling and laboratory support in centres treating people at risk and their families need to be urgently reassessed.

Human T-lymphotropic virus type III (HTLV-III) infection in seronegative haemophiliacs after transfusion of factor VIII

Fifteen haemophiliac patients acquired antibodies to human T-lymphotropic virus type III during 1984. One batch of factor VIII concentrate given to all these patients is presumed to be the cause of the seroconversion. A further eighteen patients who received the same batch did not seroconvert and one other patient became seropositive but had not received this batch. Before transfusion of the implicated batch the patients had low T-helper-cell numbers and T-helper/suppressor ratios; neither changed in those who seroconverted. The probability of seroconversion was independently related to the pre-existing low T-helper/suppressor ratio, the number of vials of the implicated batch transfused, and the total annual factor VIII consumption. Ten other patients received a batch of factor IX concentrate from the same donor plasma; none of these patients seroconverted.

Neutralization of human T-lymphotropic virus type III by sera of AIDS and AIDS-risk patients

Human T-lymphotropic virus type III (LAV, HTLV-III) is aetiologically linked to acquired immune deficiency syndrome (AIDS) and persistent general lymphadenopathy (PGL). Specific radioimmunoassays (RIA), enzyme-linked assays, immunofluorescence assays (IFA) and immunoblotting techniques are being used widely to detect serum antibodies to HTLV-III in infected patients and in those at risk of infection. However, these assays do not functionally identify those antibodies that neutralize the infectivity of the virus. We have used three methods of titrating serum neutralizing factors: inhibition of syncytium induction, neutralization of envelope pseudotypes of vesicular stomatitis virus (VSV) and reduction of infectivity of HTLV-III for a cell line permissive to virus replication. We report here that sera from subjects in various disease categories possess only low-level neutralizing activity, even when antibodies to viral membrane antigens are present in high titre. Envelope pseudotypes prepared from four HTLV-III isolates made in three different countries are equally sensitive to neutralization by positive sera, including sera from patients yielding two of the virus isolates.

Rising prevalence of human T-lymphotropic virus type III (HTLV-III) infection in homosexual men in London

The prevalence of antibody to HTLV-III has increased from 3.7% (4/107) amongst unselected British homosexual men attending a London sexually transmitted disease (STD) clinic during one week in March, 1982, to 21% (26/124) in those attending during one week in July, 1984. Seropositive men had a significantly higher prevalence of infection with hepatitis B virus than did seronegative men. 82% (27/33) of the seropositive men in 1984 were symptomless or had only local genito-urinary symptoms referable to the STD for which they were attending. The evidence suggests that HTLV-III was initially an imported but is now an endemic sexually transmitted agent. As of July, 1984, at least 2600 homosexual men in London would probably have been infected.

HTLV-III serology distinguishes atypical and endemic Kaposi's sarcoma in Africa

Serum samples from African patients with Kaposi's sarcoma and acquired-immuno-deficiency-syndrome-related (AIDS-related) disorders and from normal subjects in Uganda and Zambia were tested for antibodies to the human T-lymphotropic retroviruses (HTLV) types I, II, and III. Nearly 90% of patients with AIDS-related disorders or with atypical, aggressive Kaposi's sarcoma were seropositive for HTLV-III in both countries, whereas only 17% of patients with classic endemic Kaposi's sarcoma were seropositive. Among the controls 20% were seropositive for HTLV-III in Uganda but only 2% in Zambia. None of the subjects tested had antibodies to HTLV-I or HTLV-II. These results are further evidence of the emergence of a clinically atypical form of Kaposi's sarcoma in Africans, which resembles that seen in American patients with AIDS, and which is associated with HTLV-III infection. The low frequency of antibodies to HTLV-III in the normal Zambian population together with the first appearance of HTLV-III-associated diseases during the past 2 years suggests that this virus is new to Zambia, although it may have been present in Uganda for longer.

Prevalence of antibody to human T-lymphotropic virus type III in AIDS and AIDS-risk patients in Britain

2000 persons in the UK were examined serologically for antibodies to human T-lymphotropic virus type III (HTLV-III). Sera reacting in a membrane immunofluorescence assay (IFA) to HTLV-III were also positive when tested against cells infected with lymphadenopathy virus (LAV-1), and cross-adsorption tests indicated that these retroviruses are probably identical. A competitive radioimmunoassay (RIA), which was wholly concordant with IFA, was used to screen the sera. 30/31 patients with the acquired immunodeficiency syndrome (AIDS) were seropositive, as were 89% patients with persistent generalised lymphadenopathy (PGL), 17% symptomless homosexual men, 34% haemophiliacs receiving pooled clotting factors, and 1.5% intravenous drug abusers. None of more than 1000 unselected blood donors was seropositive. These data confirm the close association between HTLV-III and AIDS and PGL and show that infection with HTLV-III is also prevalent in the populations in whom these syndromes are most likely to develop. However, it would be unwise to presume that AIDS will necessarily develop in seropositive subjects.

Clinical findings and serological evidence of HTLV-III infection in homosexual contacts of patients with AIDS and persistent generalised lymphadenopathy in London

Between 1980 and 1984 28 homosexual men who had had ano-genital intercourse with patients with either acquired immunodeficiency syndrome (AIDS) or persistent generalised lymphadenopathy (PGL) were followed up. The pattern of the sexual links indicated that within this group there were two clusters, one consisting of 7 men and the other of 13.17 of the 28 contacts became ill with either AIDS or PGL; among those in the clusters, 4 died of AIDS and 11 had PGL, and of the rest 2 had PGL. 16 of the 19 men in the clusters who were tested for HTLV-III antibodies were seropositive, as were 7 of those not in the clusters. 111 men attending a genitourinary medicine clinic who had not had known contact with either AIDS or PGL patients and who were being screened for syphilis served as controls. Of these, 19/86 who were homosexual and 0/25 who were heterosexual were positive for HTLV-III antibodies. None of the 4 who died of AIDS had had contact with each other. The 2 in the first cluster seemed to have been linked by a symptomless HTLV-III-negative man, who was also probably the link between the two clusters, while in the second cluster the chief "carrier" seemed to be a seropositive man in whom PGL developed. These findings are consistent with the hypothesis that HTLV-III is the sexually transmitted causative agent of AIDS and PGL.

Low prevalence in the UK of HTLV-I and HTLV-II infection in subjects with AIDS, with extended lymphadenopathy, and at risk of AIDS

Antibodies reacting selectively with human T-cell leukaemia virus type I (HTLV-I) were detected in approximately 5% patients with extended lymphadenopathy syndrome (ELAS) and in less than 1% of unselected homosexual patients and drug abusers. None of 22 patients with acquired immunodeficiency syndrome (AIDS) had HTLV-I antibodies and neither did 85 haemophiliacs and 940 blood donors. 3 out of 113 drug addicts had high titres of antibodies to human T-cell leukaemia virus type II (HTLV-II). A T-cell line was derived from 1 of the seropositive ELAS patients. This line was found to be infected with, and releasing, HTLV-I. Infection by HTLV-I and HTLV-II retroviruses thus occurs more frequently in ELAS patients and drug addicts than in the UK population as a whole, but the low prevalence of these infections in ELAS and AIDS patients indicates that these two strains of lymphotropic retroviruses have no aetiological role in ELAS and AIDS.