Serological response in patients with chronic asymptomatic human immunodeficiency virus infection

Immune response to HIV p24 core protein during the early phases of human immunodeficiency virus infection

The immune response to the p24 core antigen of human immunodeficiency virus type 1 (HIV-1) was studied in serial samples collected prospectively from 52 homosexual males in two separate cohorts from Amsterdam and San Francisco. p24 antibody levels were quantified with an antigen sandwich immunoassay using p24 recombinant antigen as capture and probe. Titers and slopes of dilution curves reflecting antibody affinity were analyzed. Only 45 of 52 men developed a measurable primary immune response to p24. In 17 (33%) patients there was a low response with maximum antibody titer below 66, shallow (low affinity) dilution curve, and 10 of the 17 became HIV antigen positive over a 2 year period. In 24 (46%) of the 52 patients titers ranged from 100-4000, steeper dilution curves were noted, and none became HIV antigen positive. Four (8%) men developed a strong immune response with high titers (greater than 12,000) and high affinity type dilution curve. Over time, after the peak immune response, antibody titer declined in some individuals related in part to the formation of immune complexes between HIV-1 p24 antigen and antibody which were dissociable. In vitro, the addition of increasing amounts of purified p24 antigen corresponded to decreasing antibody titer and a shallower dilution curve suggesting a preferential consumption of high affinity antibodies for complex formation. The magnitude of immune response to HIV-1 p24 antigen varies widely in infected homosexual men. Both the intrinsic ability to mount an immune response and immune complex formation contribute to the measurable antibody level.

Competition ELISA using a human monoclonal antibody for detection of antibodies against human immunodeficiency virus type 1

A novel competition ELISA for detection of antibodies against HIV-1 was developed. The assay is based on competition at the single epitope level and utilises a human monoclonal antibody and an E. coli-produced fragment of the transmembrane glycoprotein gp41. The sensitivity of the assay was 100% in tests on 247 serum samples obtained from 219 individuals previously shown to be HIV-1 antibody positive by both conventional indirect ELISA and the immunoblotting test. The patients represented various clinical and immunological stages of HIV-1 infection. Likewise, the specificity of the assay was 100% in tests on 105 serum samples from normal individuals previously tested negative by indirect ELISA. Further, among 105 serum samples selected due to consistent false positive reactions in the indirect ELISA only 2 samples (1.9%) demonstrated false positive reactions in the competition ELISA, i.e. 98.1% specificity. Finally, only 2 of 57 (3.5%) serum samples from HIV-2 infected individuals showed positive reactions in the assay, while 54 (94.7%) had absorbance values similar to the negative controls. These results demonstrate that human monoclonal antibodies may form the basis for highly sensitive and specific assays for detection of antibodies to HIV-1.

Clinical signs and laboratory markers in predicting progression to AIDS in HIV-1 infected patients

In a prospective longitudinal study 89 men with HIV-1 infection were observed for a mean time of 51 months with regard to clinical signs and laboratory findings predictive of progression to AIDS/opportunistic infection (OI). In a bivariate regression analysis the clinical signs showing a significant relation to AIDS development were: dermatitis of the face, yellow toe nail changes, hairly leukoplakia and oral candidiasis. The laboratory findings significantly associated with progression to AIDS were: decrease of the relative and absolute number of CD4 lymphocytes, decrease of the CD4/CD8 ratio, HIV p24 antigenaemia, lack of anti-HIV p24, elevated erythrocyte sedimentation rate, anaemia and elevated serum-beta-2-microglobulin. The relative number (%) of CD4 cells was found superior to the absolute number and the CD4/CD8 ratio. In a multivariate regression analysis decrease of CD4 lymphocytes and lack of anti-HIV p24 were independently associated with subsequent AIDS/OI development.

Analysis of a highly immunodominant epitope in the human immunodeficiency virus type 1 transmembrane glycoprotein, gp41, defined by a human monoclonal antibody

A human monoclonal antibody, 41-7 [immunoglobulin G1(kappa)], directed against the transmembrane glycoprotein gp41 of the human immunodeficiency virus type 1 (HIV-1) has been produced by direct fusion of lymph node cells from an HIV-1-infected individual with a human B-lymphoblastoid cell line. The minimal essential epitope for 41-7 was mapped to a conserved seven-amino acid sequence, N-CSGKLIC-C, located within the N-terminal part of gp41. Antibodies blocking the binding of 41-7 could be detected in the serum of all HIV-1-infected individuals tested, irrespective of the stage of the infection. The epitope is located externally to the plasma membrane, and it is accessible to antibody in the native conformation of the glycoprotein. Despite this, no neutralizing activity of 41-7 could be demonstrated in vitro. These data indicate, directly and indirectly, that this immunodominant epitope on gp41, although exposed on the viral surface, elicits antibodies lacking antiviral activity and, hence, should be avoided in future vaccine candidates.

Antibodies against the major core protein p24 of human immunodeficiency virus: relation to immunological, clinical and prognostic findings

In 79 homosexual men positive for antibody to human immunodeficiency virus (HIV), the titer and avidity of p24 antibody was determined by an indirect ELISA and the serum tested for the presence of HIV antigen. Results were examined for a possible correlation with clinical, immunological and prognostic findings. High titers and low avidity of p24 antibodies correlated significantly with a normal pokeweed mitogen response, early lymph node changes, and an asymptomatic and stable clinical condition. In HIV antigen negative patients, low titers and high avidity of p24 antibodies correlated significantly with a progressive clinical condition. The finding of primarily high avidity antibodies against p24 antigen in patients with more advanced immunodeficiency indicates that a decline of p24 antibodies during the clinical course of HIV infection may not be explained exclusively by an increased production of viral proteins.