Hans Gaines

Rapid development of isolate-specific neutralizing antibodies after primary HIV-1 infection and consequent emergence of virus variants which resist neutralization by autologous sera.

The kinetics of appearance and specificity of HIV-1 neutralizing antibodies was studied in four individuals. HIV-1 was isolated during symptomatic primary HIV-1 infection and repeatedly thereafter, and tested against autologous sera collected in parallel. Our patients developed isolate-specific low-titer neutralizing antibodies within 2-4 weeks, and the titers to the first isolates increased with time. We documented the emergence of virus variants with reduced sensitivity to neutralization by autologous, but not heterologous, sera in three patients. These virus variants were not, however, resistant to neutralization per se, since they were readily neutralized by the positive control serum. Our patients did not develop antibodies capable of neutralizing the new virus variants during the observation period. This suggests either a failure of the immune system to respond to the new virus variants or a mechanism by which the virus evades detection by the immune system. The emergence of neutralization-resistant virus variants was not directly correlated with disease progression since two patients have remained asymptomatic after the emergence of such virus variants. It is, however, likely that the emergence of virus variants which the patient fails to neutralize in the long run contributes to disease progression.

ANTIBODY RESPONSE IN PRIMARY HUMAN IMMUNODEFICIENCY VIRUS INFECTION

The antibody response in 20 homosexual men with symptomatic primary HIV infection was studied with ten different antibody assays (enzyme-linked immunosorbent assays, indirect immunofluorescence assays, radioimmunoprecipitation [RIPA], and western blot). HIV antibodies were detectable by all the assays within 2 months after onset of illness. RIPA and western blot were more sensitive than the other assays--all serum samples obtained at 2 weeks and after were reactive. In all cases, the first serum sample reactive by RIPA precipitated gp160 whereas, by western blot, antibodies to p24 were first recognised. This study shows the necessity of including gp160 and p24 in any assay to detect early antibody response in primary HIV infection. 5 patients were studied by virus isolation. During the 2 first weeks after onset of symptoms, HIV was demonstrated in cell-free plasma in all cases and, in 4 cases, also in peripheral blood mononuclear cells. Samples obtained later contained demonstrable infectious virus in only 1 of 4 cases. Thus a phase of viraemia precedes the antibody response in symptomatic primary HIV infection.

Majority of CD4+ T cells from peripheral blood of HIV-1–infected individuals contain only one HIV DNA molecule

Neither the number of HIV-1 proviruses within individual infected cells in HIV-1–infected patients nor their genetic relatedness within individual infected cells and between cells and plasma virus are well defined. To address these issues we developed a technique to quantify and genetically characterize HIV-1 DNA from single infected cells in vivo. Analysis of peripheral blood CD4+ T cells from nine patients revealed that the majority of infected cells contain only one copy of HIV-1 DNA, implying a limited potential for recombination in virus produced by these cells. The genetic similarity between HIV populations in CD4+ T cells and plasma implies ongoing exchange between these compartments both early and late after infection.

Viral dynamics in primary HIV-1 infection.

ObjectivesTo study the natural course of viremia during primary HIV infection (PHI). MethodEight patients were followed from a median of 5 days from the onset of PHI illness. Plasma HIV-1 RNA levels were measured frequently and the results were fitted to mathematical models. HIV-1 RNA levels were also monitored in nine patients given two reverse transcriptase inhibitors and a protease inhibitor after a median of 7 days from the onset of PHI illness. ResultsHIV-1 RNA appeared in the blood during the week preceding onset of PHI illness and increased rapidly during the first viremic phase, reaching a peak at a mean of 7 days after onset of illness. This was followed by a phase of rapidly decreasing levels of HIV-1 RNA to an average of 21 days after onset. Viral density continued to decline thereafter but at a 5- to 50-fold lower rate; a steady-state level was reached at a median of 2 months after onset of PHI. Peak viral density levels correlated significantly with levels measured between days 50 and 600. Initiation of antiretroviral treatment during PHI resulted in rapidly declining levels to below 50 copies/ml. ConclusionsThis study demonstrates the kinetic phases of viremia during PHI and indicates two new contributions to the natural history of HIV-1 infection: PHI peak levels correlate with steady-state levels and HIV-1 RNA declines biphasically; an initial rapid decay is usually followed by a slow decay, which is similar to the initial changes seen with antiviral treatment.

Diagnosis of primary HIV-1 infection and duration of follow-up after HIV exposure

ObjectiveTo determine the sensitivity of 33 currently available and seven earlier tests for the detection of HIV or HIV antibody in primary HIV-1 infection, to estimate the duration of the ‘window period’ and the influence of early initiated antiretroviral treatment (ART). DesignA prospective cohort study of 38 patients with primary HIV-1 infection. ART was initiated at a median time of 13 (range 0–23) days after the onset of symptoms in 10 patients. Main outcome measuresThe time from infection to onset of symptoms and from onset of symptoms to the appearance of HIV antibody as measured by 36 different tests, and the start and duration of viraemia, as detected by four different tests. ResultsThe illness appeared 13–15 days after infection in 12 of 15 determinable cases, and seroconversion was detected within 1–2 weeks after the onset of illness by 27 of 30 currently available tests for HIV antibody, in contrast to the 2–7 weeks or more needed by the old tests. HIV RNA appeared during the week preceding the onset of illness and was detected in all subsequent samples, except when ART had been initiated, which also induced a delay of the antibody response. ConclusionMany tests for HIV or HIV antibody can now be employed for an early confirmation of primary HIV infection (PHI). Currently available screening tests proved much more sensitive than older tests, and seroconversion was usually detected within one month after infection. Consequently, in Sweden we now recommend only 3 months of follow-up after most cases of HIV exposure.

Antigen detection in primary HIV infection.

Serial blood samples were obtained from 21 homosexuals who had developed symptomatic primary infection with human immunodeficiency virus (HIV) after a median incubation time of 14 days. During the first two weeks after the onset of illness HIV antigen (p24) was detected in the blood by enzyme linked immunosorbent assay (ELISA). During the second and third weeks after the onset of illness p24 antibody was detected by Western blot assay and antigen concentrations rapidly decreased to undetectable values. Dissociation of antigen-antibody complexes showed complexed antigen during the phase of declining concentrations of free antigen. Neither free nor complexed antigen was detected in any serum samples for several months thereafter, which suggested that failure to detect HIV antigen reflected low or absent synthesis of viral protein rather than masking of antigen by antibodies. Reappearance of HIV antigen with a fall in p24 antibody concentration was observed in a few patients six months or more after the onset of disease. The combined use of antigen and antibody assays made it possible to obtain evidence of infection with HIV in all of the 95 serum samples tested, illustrating the usefulness of these assays for diagnosing infection with HIV in its early stages.

Clinical picture of primary HIV infection presenting as a glandular-fever-like illness.

The clinical symptoms and signs were assessed in 20 consecutive patients developing infection with the human immunodeficiency virus (HIV). All were male homosexuals and all presented with a glandular-fever-like illness. Changes in laboratory values were compared with findings in 40 HIV negative male homosexual controls. In the 10 patients for whom date of exposure to the virus could be established the incubation period was 11-28 days (median 14). One or two days after the sudden onset of fever patients developed sore throat, lymphadenopathy, rash, lethargy, coated tongue, tonsillar hypertrophy, dry cough, headache, myalgia, conjunctivitis, vomiting, night sweats, nausea, diarrhoea, and palatal enanthema. Twelve patients had painful, shallow ulcers in the mouth or on the genitals or anus or as manifested by oesophageal symptoms; these ulcers may have been the site of entry of the virus. During the first week after the onset of symptoms mild leucopenia, thrombocytopenia, and increased numbers of banded neutrophils were detected (p less than 0.0005). The mean duration of acute illness was 12.7 days (range 5-44). All patients remained healthy during a mean follow up period of 2.5 years. Heightened awareness of the typical clinical picture in patients developing primary HIV infection will alert the physician at an early stage and so aid prompt diagnosis and help contain the epidemic spread of AIDS.

Immunological changes in primary HIV-1 infection

Homosexual men with symptomatic primary HIV-1 infection displayed a pronounced lymphopaenia with significantly depressed numbers of CD3+, CD4+ and CD8+ cells and B cells during the first week of illness. Subsequently, the CD8+ cell counts rose in parallel with numbers of CD3+ cells, atypical lymphocytes and activated (CD38+ and HLA-Dr+) cells to attain maximal levels about a month following onset of illness. In contrast CD4+ and B cell numbers remained low for an extended period of time. Early signs of a host response included a transient appearance of interferon-alpha in the blood and raised levels of neopterin and beta 2-microglobulin (beta 2-M). Neither CD4+/CD8+ cell ratio nor beta 2-M resumed completely normal values during a follow-up period of 2 years. These findings shed some light on pathogenetic events during early HIV-1 infection and suggest that the infection, following the acute symptomatic stage, usually enters a stage of chronic active rather than latent infection.

rBCG Induces Strong Antigen-Specific T Cell Responses in Rhesus Macaques in a Prime-Boost Setting with an Adenovirus 35 Tuberculosis Vaccine Vector

Background BCG vaccination, combined with adenoviral-delivered boosts, represents a reasonable strategy to augment, broaden and prolong immune protection against tuberculosis (TB). We tested BCG (SSI1331) (in 6 animals, delivered intradermally) and a recombinant (rBCG) AFRO-1 expressing perfringolysin (in 6 animals) followed by two boosts (delivered intramuscullary) with non-replicating adenovirus 35 (rAd35) expressing a fusion protein composed of Ag85A, Ag85B and TB10.4, for the capacity to induce antigen-specific cellular immune responses in rhesus macaques (Macaca mulatta). Control animals received diluent (3 animals). Methods and Findings Cellular immune responses were analyzed longitudinally (12 blood draws for each animal) using intracellular cytokine staining (TNF-alpha, IL-2 and IFN-gamma), T cell proliferation was measured in CD4+, CD8alpha/beta+, and CD8alpha/alpha+ T cell subsets and IFN-gamma production was tested in 7 day PBMC cultures (whole blood cell assay, WBA) using Ag85A, Ag85B, TB10.4 recombinant proteins, PPD or BCG as stimuli. Animals primed with AFRO-1 showed i) increased Ag85B-specific IFN-gamma production in the WBA assay (median >400 pg/ml for 6 animals) one week after the first boost with adenoviral-delivered TB-antigens as compared to animals primed with BCG (<200 pg/ml), ii) stronger T cell proliferation in the CD8alpha/alpha+ T cell subset (proliferative index 17%) as compared to BCG-primed animals (proliferative index 5% in CD8alpha/alpha+ T cells). Polyfunctional T cells, defined by IFN-gamma, TNF-alpha and IL-2 production were detected in 2/6 animals primed with AFRO-1 directed against Ag85A/b and TB10.4; 4/6 animals primed with BCG showed a Ag85A/b responses, yet only a single animal exhibited Ag85A/b and TB10.4 reactivity. Conclusion AFRO-1 induces qualitatively and quantitatively different cellular immune responses as compared with BCG in rhesus macaques. Increased IFN-gamma-responses and antigen-specific T cell proliferation in the CD8alpha/alpha+ T cell subset represents a valuable marker for vaccine-take in BCG-based TB vaccine trials

A multicentre evaluation of the accuracy and performance of IP-10 for the diagnosis of infection with M. tuberculosis

IP-10 has potential as a diagnostic marker for infection with Mycobacterium tuberculosis, with comparable accuracy to QuantiFERON-TB Gold In-Tube test (QFT-IT). The aims were to assess the sensitivity and specificity of IP-10, and to evaluate the impact of co-morbidity on IP-10 and QFT-IT. 168 cases with active TB, 101 healthy controls and 175 non-TB patients were included. IP-10 and IFN-γ were measured in plasma of QFT-IT stimulated whole blood and analyzed using previously determined algorithms. A subgroup of 48 patients and 70 healthy controls was tested in parallel with T-SPOT.TB IP-10 and QFT-IT had comparable accuracy. Sensitivity was 81% and 84% with a specificity of 97% and 100%, respectively. Combining IP-10 and QFT-IT improved sensitivity to 87% (p < 0.0005), with a specificity of 97%. T-SPOT.TB was more sensitive than QFT-IT, but not IP-10. Among non-TB patients IP-10 had a higher rate of positive responders (35% vs 27%, p < 0.02) and for both tests a positive response was associated with relevant risk factors. IFN-γ but not IP-10 responses to mitogen stimulation were reduced in patients with TB and non-TB infection. This study confirms and validates previous findings and adds substance to IP-10 as a novel diagnostic marker for infection with M. tuberculosis. IP-10 appeared less influenced by infections other than TB; further studies are needed to test the clinical impact of these findings.