The immunopathogenesis of human immunodeficiency virus infection

Human CD4 restores normal T cell development and function in mice deficient in murine CD4

The ability of a human coreceptor to function in mice was investigated by generating human CD4 (hCD4)-expressing transgenic mice on a mouse CD4-deficient (mCD4-/-) background. From developing thymocyte to matured T lymphocyte functions, hCD4 was shown to be physiologically active. By examining the expansion and deletion of specific V beta T cell families in mutated mice with and without hCD4, it was found that hCD4 can participate in positive and negative selection. Mature hCD4 single positive cells also were found in the periphery and they were shown to restore MHC class II-restricted alloreactive and antigen-specific T cell responses that were deficient in the mCD4 (-/-) mice. In addition, these hCD4 reconstituted mice can generate a secondary immunoglobulin G humoral response matching that of mCD4 wild-type mice. The fact that human CD4 is functional in mice and can be studied in the absence of murine CD4 should facilitate studies of human CD4 activity in general and human immunodeficiency virus 1 gp120-mediated pathogenesis in acquired immune deficiency syndrome specifically.

Longitudinal analysis of T cell receptor (TCR) gene usage by human immunodeficiency virus 1 envelope-specific cytotoxic T lymphocyte clones reveals a limited TCR repertoire

Human immunodeficiency virus 1 (HIV-1) infection is associated with a vigorous cellular immune response that allows detection of cytotoxic T lymphocyte (CTL) activity using freshly isolated peripheral blood mononuclear cells (PBMC). Although restricting class I antigens and epitopes recognized by HIV-1-specific CTL have been defined, the effector cells mediating this vigorous response have been characterized less well. Specifically, no studies have addressed the breadth and duration of response to a defined epitope. In the present study, a longitudinal analysis of T cell receptor (TCR) gene usage by CTL clones was performed in a seropositive person using TCR gene sequences as a means of tracking responses to a well-defined epitope in the glycoprotein 41 transmembrane protein. 10 CTL clones specific for this human histocompatibility leukocyte antigen-B14-restricted epitope were isolated at multiple time points over a 31-mo period. All clones were derived from a single asymptomatic HIV-1-infected individual with a vigorous response to this epitope that was detectable using unstimulated PBMC. Polymerase chain reaction amplification using V alpha and V beta family-specific primers was performed on each clone, followed by DNA sequencing of the V-D-J regions. All 10 clones utilized V alpha 14 and V beta 4 genes. Sequence analysis of the TCR revealed the first nine clones isolated to also be identical at the nucleotide level. The TCR-alpha junctional region sequence of the tenth clone was identical to the junctional region sequences of the other nine, but this clone utilized distinct D beta and J beta gene segments. This study provides evidence that the observed high degree of HIV-1-specific CTL activity may be due to monoclonal or oligoclonal expansion of specific effector cells, and that progeny of a particular CTL clone may persist for prolonged periods in vivo in the presence of a chronic productive viral infection. The observed limited TCR diversity against an immunodominant epitope may limit recognition of virus variants with mutations in regions interacting with the TCR, thereby facilitating immune escape.

HIV-mediated defects in immune regulation

The Division of AIDS (DAIDS), National Institute of Allergy and Infectious Diseases (NIAID), sponsored a Workshop on HIV-Mediated Defects in Immune Regulation on September 29-30, 1993. Workshop participants included investigators in basic research of immune regulation, animal models of HIV disease, HIV epidemiology, and HIV clinical research and treatment. The purpose of the workshop was to describe and evaluate biological mechanisms of HIV-mediated immune deficiency other than direct killing of infected CD4+ cells. The workshop focused on HIV-mediated dysfunction in signal transduction and in T cell development and maturation. Mechanisms by which HIV has been proposed to influence signal transduction include gp120 ligation to CD4, HIV superantigen(s), and HIV-mediated perturbations in signal pathway components (e.g., receptors, kinases, phosphatases, cytokines, and cyclins). As a result of signal dysfunction, cells may fail to respond to foreign antigens (anergy) or become predisposed to enter suicide pathways, otherwise known as programmed cell death or apoptosis. Programmed cell death is a normal immune regulatory mechanism that is activated to prevent anti-self responses and also to delete expanded but no longer needed cell populations. In the immune system, new cells are constantly produced from stem cells to replace those that die from age, pathological response, or programmed cell death. Dysfunction in these new cells may occur if HIV causes changes in the structural environment of the thymus and lymph nodes, or in cytokine signals.

Apoptosis: programmed cell death in health and disease

Apoptosis is a normal physiological cell death process of eliminating unwanted cells from living organisms during embryonic and adult development. Apoptotic cells are characterised by fragmentation of nuclear DNA and formation of apoptotic bodies. Genetic analysis revealed the involvement of many death and survival genes in apoptosis which are regulated by extracellular factors. There are multiple inducers and inhibitors of apoptosis which interact with target cell specific surface receptors and transduce the signal by second messengers to programme cell death. The regulation of apoptosis is elusive, but defective regulation leads to aetiology of various ailments. Understanding the molecular mechanism of apoptosis including death genes, death signals, surface receptors and signal pathways will provide new insights in developing strategies to regulate the cell survival/death. The current knowledge on the molecular events of apoptotic cell death and their significance in health and disease is reviewed.

Murine retrovirus-induced depletion of T cells is mediated through activation-induced death by apoptosis

ts1, a mutant of Moloney murine leukemia virus, causes neurologic disorders and acute immunodeficiency associated with the destruction of thymocytes and helper T cells. In this study, we examined whether apoptosis was involved in ts1-induced killings of T cells. Neonatal mice were inoculated with ts1, and 20 to 23 days postinoculation, when cytopathic effects on T cells normally appear, thymocytes and splenic lymphocytes were isolated and examined. Our results showed that several features of apoptosis were present in ts1-infected thymocytes and splenic lymphocytes. Apoptotic fragmented DNA, condensation of the chromatin, and enhanced cell death after stimulation with mitogens which was preventable with protein synthesis inhibitors, all of which are common features of apoptotic cell death, were observed in ts1-infected cells. Several other viruses, including human immunodeficiency virus, have been shown to cause apoptotic death of T cells. Here we show for the first time that a murine retrovirus which also induces immunodeficiency can cause apoptotic T-cell death. Future studies with this murine retrovirus may provide important results to help us better understand the mechanisms of retrovirus-induced apoptosis of T cells.

Human immunodeficiency virus type 1 RNA expression by four chronically infected cell lines indicates multiple mechanisms of latency

Recent information has suggested that posttranscriptional mechanisms, whereby human immunodeficiency virus type 1 (HIV-1) RNA exists as multiply spliced transcripts without promoting an accumulation of the larger messages, are responsible for maintaining a stable state of nonproductive viral expression or viral latency. To test the universality of these observations, we compared the patterns of viral RNA splicing and the frequencies of cells actually harboring HIV-1 RNA in four chronically HIV-1-infected cell lines (U1 [promonocytic], ACH-2 [T lymphocytic], OM-10.1 [promyelocytic], and J1.1 [T lymphocytic]). In uninduced U1 and ACH-2 cultures, a high frequency of cells (approximately one in six) contained HIV-1 RNA but mainly as multiply spliced transcripts, again supporting a posttranscriptional mechanism maintaining viral latency. In sharp contrast, only 1 in 50 cells in uninduced OM-10.1 and J1.1 cultures contained HIV-1 RNA, indicating a primary transcriptional mechanism controlling viral expression in these cells. Furthermore, those OM-10.1 and J1.1 cells that did contain viral RNA were in a state of productive HIV-1 expression marked by the presence of both spliced and unspliced transcripts. Even though the total absence of viral RNA in the majority of OM-10.1 and J1.1 cells indicated a state of absolute latency, treatment with tumor necrosis factor alpha induced transcription of HIV-1 RNA in nearly 100% of the cells in all four of the chronically infected cultures. Tumor necrosis factor alpha induction of U1, ACH-2, and OM-10.1 cultures resulted in an initial accumulation of multiply spliced HIV-1 RNA followed by a transition to the larger unspliced viral RNA transcripts. This RNA splice transition was less apparent in the J1.1 cell line. These results demonstrate that host cell-specific transcriptional and posttranscriptional mechanisms are important factors in the control of HIV-1 latency.

Viral multiplicity of attachment and its implications for human immunodeficiency virus therapies

The multiplicity of attachment (MOA) of a virion in any particular time interval is the average number of cellular attachment opportunities that must be blocked to keep the virion in suspension. MOA is usually proportional to incubation time and cell concentration. Low MOA (like low multiplicity of infection) is required for reproducible assay of adsorptive blockers, and high MOA by itself can produce spurious synergies between adsorptive blockers, e.g., soluble CD4 (sCD4) and some antibodies. Poliovirus and human immunodeficiency virus (HIV) data show that viral neutralization conforms quantitatively to MOA and kinetic theory over large ranges of incubation times and target cell concentrations. Extrapolating sCD4 data beyond conditions achievable in vitro to those in vivo predicts that sCD4 concentrations above the strain-specific sCD4-gp120 dissociation constant are required to block lymphoid HIV significantly, in at least semiquantitative agreement with clinical results. The extrapolation is applicable to humoral neutralization data as well. MOA analysis also indicates that although completely stopping the attachment of individual virions to cells may still be an effective therapeutic strategy against established HIV infection, merely retarding attachment probably is not. The concept of MOA holds great promise for improving the therapeutic relevance of in vitro data and can be applied to any infectious agent, to many processes that impair or enhance infection steps, and to many assay end points, not just infection.

Immunology and exercise. Physiology, pathophysiology, and implications for HIV infection

This article covers the latest information on the immunologic changes of exercise as well as the effects of regular exercise on persons infected with HIV and the exercise recommendations for HIV-infected athletes. Included are discussions about psychoneuroimmunology and exercise-associated changes in immunity.

Genetic analysis of HIV-1 during rapid progression to AIDS in an apparently healthy man

We encountered a case of HIV-1 infection in a previously healthy man, which was characterized by rapid progression to AIDS and death within 7 months in association with high levels of antigenemia throughout the clinical course and no humoral immune response for at least 6 months. Genetic changes of the third variable domain (V3) of the envelope gene of HIV-1 in serum samples were analyzed at four time points during his rapid clinical course. The nucleotide changes were confined to a maximum of three substitutions among 105 nucleotides of the V3 region. A major population of the viral clones in this patient showed one amino acid substitution from aspartic acid (a negatively charged amino acid) to lysine (a positively charged amino acid) at position 30 from the first cysteine of the V3 loop. This substitution was thought to be associated with phenotypic changes, and viruses with this sequence in the V3 region had a strong syncytium-inducing ability in MT-4 cells. It appears that the lack of a humoral immune response accelerated disease progression in our patient and a genetic change that appeared to produce a phenotypic change occurred at an early stage of the disease.

Systemic lymphadenopathic histology in human immunodeficiency virus-1-seropositive drug addicts without apparent acquired immunodeficiency syndrome

We examined lymph nodes from multiple sites in 50 individuals infected with human immunodeficiency virus (HIV-1) who died accidentally of drug overdoses and in whom there was no evidence of opportunistic infection. The size, histologic pattern, presence of Warthin-Finkeldey-type giant cells, and estimation of CD4 cell count of these lymph nodes were compared with those of 13 seronegative drug addicts (controls). Lymph nodes from seropositive individuals were slightly but significantly larger than those of controls. Lymph nodes from seropositive cases were much more likely to contain secondary follicles (90%) than were those from controls (20%). Unlike follicles in control nodes, most secondary follicles in the seropositive cases were in various stages of fragmentation and involution. As follicular changes progressed, there was a decrease in CD4 cells and an increase in intrafollicular and paracortical plasma cells. Plasmacytosis was much more prevalent in lymph nodes from seropositive individuals than in controls. Warthin-Finkeldey-type giant cells were present in at least one node in 29 of 50 seropositive cases, were most numerous in those showing follicular hyperplasia with fragmentation (45% of cases), and were especially numerous in Peyer's patches (61% of cases). There was generally good concordance of HIV-1-associated follicular morphology among diverse lymph node groups. There is prolonged generalized, mild hyperplastic lymphadenopathy with frequent syncytial cells in intravenous drug addicts with asymptomatic HIV-1 infection.

Human immunodeficiency virus type 1 (HIV-1) and human hematopoietic progenitor cells

Besides a progressive depletion of CD4+ T-lymphocytes, other peripheral blood cytopenias, (granulocytopenia, anemia and thrombocytopenia) are frequently observed in HIV-1 seropositive individuals, especially in patients with overt AIDS. Various experimental evidences suggest that HIV-1 could play a direct role in the pathogenesis of HIV-1 related peripheral blood cytopenias, affecting the survival/proliferation capacity of hematopoietic progenitors. CD34+ human hematopoietic progenitors, however, are substantially not susceptible to HIV-1 infection either in vitro and in vivo and their defects seem rather related to an alteration of bone marrow and peripheral blood microenvironments due to the presence of soluble HIV-1 specific products.

CD8+ cytolytic T lymphocytes become infected in vitro in the process of killing HIV-1-infected target cells

In the present study the requirements for in vitro infection of antigen-specific CD8+ cytotoxic T lymphocytes (CTL) with human immunodeficiency virus -1(HIV-1) were investigated. CD3+CD8+CD4- HIV-1 nef-specific CTL become infected with HIV-1 after short-term co-culture with HLA-matched HIV-1-infected CD20+ B lymphoblastoid cells (B-LCL) which are specifically killed. Similar results were observed with an allospecific CD8+ CTL population. In addition, co-culture experiments showed that once infected with HIV-1, these CD8+ CTL could spread the infection further to uninfected CD4+ lymphocytes. In contrast, CD8+ CTL did not become infected with HIV-1 when co-cultured with HLA-mismatched HIV-1-infected B-LCL which are not killed. These observations in vitro could have relevance in peripheral lymphoid organs contributing to the progressive decrease of HIV-specific CD8+ CTL activity that is associated with the progression to AIDS.

Cross-reactivity between autoimmune anti-U1 snRNP antibodies and neutralizing epitopes of HIV-1 gp120/41

We report extensive amino acid sequence homology between HIV-1 gp120/41, and > 33% of a U1 RNA-associated splicing protein, 70K. The latter is a target of autoimmune anti-RNP antibodies in mixed connective tissue disease (MCTD). The homologies, involving dominant epitopes of 70K and neutralizing epitopes of gp120/41, are the basis for mutual antibody cross-reactivity. A key finding is that the epitope GRAFVTIG in the V3 loop of gp120 (strain IIIB) is homologous to the functionally essential U1 RNA-binding site of 70K. ELISA data reveal a mean reactivity of anti-RNP antibodies to V3 IIIB that is as high as that of HIV sera. V3 MN, containing the framework sequence G-AF-T, also cross-reacts with anti-RNP antibodies, as do hydrophilic epitopes in gp41 homologous to the COOH end of 70K. Further, there is strong cross-reactivity between HIV sera and 70K in Western blots. In contrast, antibodies from a related autoimmune disorder, Sjögren's syndrome (SS), are neither V3 nor gp41 selective. We conclude that the substantial cross-reactivities reported here are due to conserved, antigenically dominant B cell epitopes having homologous counterparts in 70K and gp120/41. Because antibody production in both MCTD and HIV-1 infection is T cell dependent, the results imply that common T cell clones are also activated in these two disease paradigms. Further exploration of the mechanisms that activate these clones, and that control their divergent fates in MCTD and AIDS, may provide new insights into immune dysregulation in HIV infection.(ABSTRACT TRUNCATED AT 250 WORDS)

T cell functions are impaired by inhaled isobutyl nitrite through a T-independent mechanism

Isobutyl nitrite is representative of a group of inhalants abused by male homosexuals and adolescents. Inhalation exposure of mice to isobutyl nitrite at 900 ppm for 45 min per day for 14 days caused serious deficits in T cell-mediated immune responses. Cytotoxic T lymphocyte (CTL) activity was reduced by 36% following the exposure. T cell proliferative responses to mitogenic and allogeneic stimulation were reduced by 37% and 51%, respectively. The exposure did not directly alter the ability of cells to synthesize or respond to IL-2. Accessory cell function in facilitating T cell activation was inhibited by about 50% following exposure to the inhalant.

Analysis of the T-cell receptor beta-chain variable-region (V beta) repertoire in monozygotic twins discordant for human immunodeficiency virus: evidence for perturbations of specific V beta segments in CD4+ T cells of the virus-positive twins

We analyzed the T-cell receptor (TCR) V beta repertoire in human immunodeficiency virus type 1 (HIV-1)-infected individuals at different stages of disease. To circumvent the effect of HLA and other loci on the expressed TCR repertoire, we compared the TCR repertoire in nine pairs of monozygotic twins who were discordant for HIV infection. A semiquantitative polymerase chain reaction (PCR) assay and flow cytometry enabled us to show distinct differences in the V beta repertoire in the HIV-positive twin compared with the HIV-negative twin. By combining PCR and cytofluorometry, these differences were restricted to a specific set of TCR V beta segments, with members of the V beta 13 family perturbed in six out of seven cases and those of the V beta 21 family perturbed in four out of seven cases studied. Most of the other V beta families remained unchanged. Our results provide direct evidence for a skewed TCR repertoire in HIV infection.

Disseminated human immunodeficiency virus 1 (HIV-1) infection in SCID-hu mice after peripheral inoculation with HIV-1

A small animal model that could be infected with human immunodeficiency virus 1 (HIV-1) after peripheral inoculation would greatly facilitate the study of the pathophysiology of acute HIV-1 infection. The utility of SCID mice implanted with human fetal thymus and liver (SCID-hu mice) for studying peripheral HIV-1 infection in vivo has been hampered by the requirement for direct intraimplant injection of HIV-1 and the continued restriction of the resultant HIV-1 infection to the human thymus and liver (hu-thy/liv) implant. This may have been due to the very low numbers of human T cells present in the SCID-hu mouse peripheral lymphoid compartment. Since the degree of the peripheral reconstitution of SCID-hu mice with human T cells may be a function of the hu-thy/liv implant size, we increased the quantity of hu-thy/liv tissue implanted under the renal capsule and implanted hu-thy/liv tissue under the capsules of both kidneys. This resulted in SCID-hu mice in which significant numbers of human T cells were detected in the peripheral blood, spleens, and lymph nodes. After intraimplant injection of HIV-1 into these modified SCID-hu mice, significant HIV-1 infection was detected by quantitative coculture not only in the hu-thy/liv implant, but also in the spleen and peripheral blood. This indicated that HIV-1 infection can spread from the thymus to the peripheral lymphoid compartment. More importantly, a similar degree of infection of the hu-thy/liv implant and peripheral lymphoid compartment occurred after peripheral intraperitoneal inoculation with HIV-1. Active viral replication was indicated by the detection of HIV-1 gag DNA, HIV-1 gag RNA, and spliced tat/rev RNA in the hu-thy/liv implants, peripheral blood mononuclear cells (PBMC), spleens, and lymph nodes of these HIV-1-infected SCID-hu mice. As a first step in using our modified SCID-hu mouse model to investigate the pathophysiological consequences of HIV-1 infection, the effect of HIV-1 infection on the expression of human cytokines shown to enhance HIV-1 replication was examined. Significantly more of the HIV-1-infected SCID-hu mice expressed mRNA for human tumor necrosis factors alpha and beta, and interleukin 2 in their spleens, lymph nodes, and PBMC than did uninfected SCID-hu mice. This suggested that HIV-1 infection in vivo can stimulate the expression of cytokine mRNA by human T cells.(ABSTRACT TRUNCATED AT 400 WORDS)

Human immunodeficiency virus type 1 mRNA expression in peripheral blood cells predicts disease progression independently of the numbers of CD4+ lymphocytes

To address the significance of human immunodeficiency virus (HIV) replication in peripheral blood mononuclear cells (PBMCs), we have used reverse transcriptase-initiated PCR to measure HIV-1 mRNA expression in PBMC specimens collected from a cohort of HIV-infected individuals during a long-term prospective study. We found dramatic differences in HIV mRNA expression among individuals with very similar clinical and laboratory indices, and this variation strongly correlated with the future course of the disease. No evidence of viral replication was detected in PBMCs from asymptomatic individuals who, thereafter, had normal levels of CD4+ cells for at least 5 years. Irrespective of whether the CD4+ cell numbers were normal at the time of sampling, abundant expression of HIV-1 mRNA in PBMCs predicted accelerated disease progression within the next 2 years. Thus, independently of what may be the rate of HIV replication in other viral reservoirs, such as lymphatic tissue, the amount of HIV mRNA in PBMCs appears to reflect the subsequent development of HIV disease. We have also used the reverse transcriptase-initiated PCR assay to demonstrate a transient response to 3'-azido-3'-deoxythymidine treatment. Determination of HIV-1 mRNA expression in the PBMCs of infected individuals could, therefore, have significant clinical utility as a prognostic indicator and as a means to guiding and monitoring antiviral therapies.

Rapid and simple PCR assay for quantitation of human immunodeficiency virus type 1 RNA in plasma: application to acute retroviral infection

A method for quantitating human immunodeficiency virus type 1 plasma viremia may be useful in monitoring disease progression and the responsiveness of patients to a therapeutic regimen or vaccine. A quantitative assay for viral RNA in plasma or sera that differs in several aspects from those reported previously was developed. First, whereas conventional reverse transcriptase-PCR assays involve a two-step process and use two enzymes, the method described uses a single enzyme, rTth DNA polymerase, for both reverse transcription and PCR. The reactions are carried out in a single tube and with a single buffer solution with uninterrupted thermal cycling. Second, uracil-N-glycosylase and dUTP are incorporated into the reaction mixtures to ensure that any carryover of DNA from previous amplifications will not compromise quantitation. Third, a quantitation standard is incorporated into each reaction mixture so that differences in amplification efficiency caused by sample interferents, variability in reaction conditions, or thermal cycling can be normalized. To ensure comparable amplification efficiency, the quantitation standard has the same primer-binding regions as the human immunodeficiency virus type 1 target and generates an amplified product of the same size and base composition. The probe-binding region was replaced with a sequence that can be detected separately. Fourth, a colorimetric detection format was modified to provide at least a four-log-unit dynamic range. The quantitative assay requires only a single amplification of the sample and can be completed in less than 8 h. The procedure was used on archival samples to demonstrate the viremic spike in acute infection and the suppressed levels of circulating virus following seroconversion.

Genomic and replicative hepatitis C virus RNA sequences and histologic activity in chronic hepatitis C

Hepatitis C virus (HCV) frequently leads to chronic hepatitis, cirrhosis, and hepatocellular carcinoma, but the mechanism of liver injury is unknown. To determine whether replication of HCV is related to liver damage, we studied 17 liver biopsy specimens (six anti-HCV-positive chronic persistent hepatitis specimens, seven anti-HCV-positive chronic active hepatitis specimens, and four anti-HCV-negative controls) by reverse transcription followed by double polymerase chain reaction for the 5' nontranslated regions of the genomic and replicative strands of HCV. The histologic activity index as well as lymphoid aggregates in portal tracts, bile duct damage, and fatty change were assessed semiquantitatively. There was a statistically significant correlation between the presence of HCV RNA sequences in liver tissue and anti-HCV antibody in serum (P < .005). No correlation was detected between the histologic activity index or any individual histologic parameters and the presence of genomic or replicative strands of HCV. These findings suggest that a direct viropathic effect is less important than other mechanisms, such as the host immune response, in the pathogenesis of hepatocyte and bile duct injury in chronic hepatitis.

Lack of correlation between phenotype activation markers of CD8 lymphocytes and cytotoxic T lymphocyte (CTL) function in HIV-1 infection: evidence for rescue with rIL-2

CTL activity against HIV-1 antigens expressed on HLA-A-matched EBV-transformed B target cells was detected in 33% (6/18) of freshly isolated PBMC (FPBMC) from patients in the early stages of HIV-1 infection (CDCII). No CTL activity was detected in FPMBC in patients with AIDS (CDCIV). However, the presence of CTL activity did not correlate with the expression of CTL activation markers. A dual-color flow cytometric examination revealed that the CD8+ lymphocytes bearing the memory (CD29) and activation (S6F1) surface molecules increased in number as the HIV-1 infection progressed. This functional and phenotypic discrepancy in memory CD8+ lymphocytes suggests that the memory CD8+ lymphocytes have lost cytotoxic function and become "paralyzed" as the HIV disease progresses. Incubation of PBMC of HIV(+) patients with rIL-2 reactivated predominantly HIV-specific CTL. However, rIL-2 stimulation also activated a "polyclonal or polyreactive" cytotoxic function. The reactivation of CTL function is rIL-2 dosage dependent and the amount of rIL-2 required for reactivation is associated with the severity of the disease. HIV antigen specific CTL in HIV(+) patients can be selectively expanded by HIV antigen stimulation in the presence of rIL-2. These results suggest that the in vivo IL-2 deficiency occurring in HIV-1 infection may be responsible in part for the "paralysis" of HIV specific CTL activity. Such activity can be rescued nonspecifically by exogenous rIL-2 stimulation and expanded specifically by HIV-1 antigen stimulation.

Vaccinology, immunology, and comparative pathogenesis of measles in the quest for a preventative against AIDS

Current approaches to the prevention and control of AIDS by vaccines and by chemotherapy have failed to provide satisfactory solutions to this important medical problem and have failed, in addition, to provide definitive guidelines for future research endeavor. Vaccine research must and will continue but it is possible that a safe and effective vaccine may never be developed and it may be timely to explore, in addition, alternative means for immunological intervention in AIDS. Both immunoprophylactic and immunotherapeutic efforts might be assisted by manipulating the T helper 1 (Th1) and T helper 2 (Th2) subsets of CD4+ T helper cells, which is therefore worthy of exploration. Selective control of immune response by the two T helper subsets is by release of different cytokines that promote either cellular or humoral immunity, the latter of which may be associated with inappropriate immune responses and with immune dysfunction. Discovery of the Th1 and Th2 subsets and definition of the cytokines they release provide a new avenue toward possible development of a safe and effective vaccine and an approach, in addition, to correction of immune dysfunction by selective cytokine administration or by cytokine ablation by antagonists or antibodies. AIDS pathogenesis and immune dysfunction are complex and understanding them may be overwhelmed by an excess of possibilities. Simplification of the endeavor might benefit from comparative studies of the pathogenesis of measles, in which there also is immune deficiency but usually with spontaneous viral clearance, reversal of immune dysfunction, and total recovery. In addition, measles presents as a single disease and is caused by antigenically stable virus. Identification of the process whereby measles immunodeficiency is spontaneously reversed might be of importance in attempting to devise means for similar reversal in AIDS.

[CD8 hyperlymphocytosis syndrome and human immunodeficiency virus infection: 5 cases]

A retrospective study on 202 consecutive patients with HIV infection was reviewed. A particular syndrome with blood CD8 lymphocytosis > 1 500/mm3, associated with a diffuse lymphocytic infiltrate histologically proved in the tissue of different organs was present in five patients. Clinical findings were variable, depending on the location of visceral infiltrate by activated, polyclonal lymphocytes of CD8 phenotype: interstitial pneumonia (n = 3), parotid gland enlargement with sicca syndrome (n = 2), pseudo-tumoral splenomegaly (n = 1), peripheral neuropathy (n = 1), superficial generalized lymphadenopathy (n = 5). This syndrome occurred early during HIV infection. All patients had a blood CD4 lymphocyte count > 200/mm3. This disorder is a host immune response, sometimes associated with the presence of some HLA antigens: HLA-DR5 or HLA A1 B8 DR3. Whether this immune response is specific or not, whether outcome of HIV infection depends on hyper CD8 lymphocytosis remains to be proved.

Lymphoma complicating immunodeficiency disorders

BACKGROUND

An increased incidence of lymphoma is seen in various types of immune deficiency or dysregulation, including congenital immune deficiency diseases, organ transplantation with iatrogenic immunosuppression, autoimmune disorders, endemic Burkitt's lymphoma, and AIDS-associated lymphoma.

RESULTS

The lymphomas seen in various immunodeficiency disorders share certain features. Thus, all consist of high-grade, B-cell tumors, with predilection for extranodal involvement, and short survival. However, certain biologic and clinical differences are also apparent. Thus, while the transplantation-associated lymphomas are uniformly associated with the Epstein-Barr Virus (EBV), this association is not seen in all systemic AIDS-related lymphomas, nor in all congenital immune deficiency disorders. Likewise, while c-myc activation has been described in certain types of HIV-related lymphomas, c-myc dysregulation has not been reported in association with organ transplantation.

CONCLUSIONS

The study of lymphomatous disease in various states of immune dysregulation may allow an understanding of the diverse pathogenic mechanisms operative in the development of malignant lymphoma in man.

Detection of HIV-1 DNA in leukocytes using a commercially available assay

Recently, an assay for detection of proviral HIV-1 DNA in leukocytes became commercially available. This assay (Amplicor HIV-1 test, Roche Diagnostic Systems) multiplies HIV-1DNA up to a detectable level, using the polymerase chain reaction. We studied performance of this assay on 74 samples from HIV-1-infected patients and on 41 samples from healthy blood donors. Twice a negative control sample appeared to be erroneously reactive. However, sensitivity and specificity on the patient and donor samples both were 100%. To avoid false-positive results, we advise to repeat initially reactive samples if no other data confirm HIV-infection.

Mechanisms of autoimmunity and AIDS: prospects for therapeutic intervention

The network theory of autoimmunity is presented with recent experimental data relevant to the understanding of the pathogenesis of AIDS. Schematically, effector T cells specific for self-antigens exist normally, but their activity is modulated and prevented by networks of regulatory T cells. As a result of mimicry between molecular components of microorganisms and self-antigens, autoimmune disease can be triggered by specific foreign pathogens which alter the state of activity of the network from suppression to activation. Conversely, by a procedure known as T-cell vaccination, autologous effector T cells re-injected after in vitro stimulation and attenuation may alter the state of the network from an activation to a suppression. Numerous observations are reviewed that support the concept of autoimmune activity in the destruction of non-infected T4 cells. Such activity is presumed to be triggered by an antigen of viral origin, the most likely, but not the only one, being the envelope protein gp 120. Based on this hypothesis, a T-cell vaccination procedure against effector T cells responsible for autoimmunopathic activity in HIV-seropositive patients is proposed, similar to the one known from experimental study of autoimmunity and presently being tested in human autoimmune diseases. Its purpose would be to prevent T-cell loss and the onset of immunodeficiency disease in HIV-seropositive patients. Apart from its potential therapeutic value, this procedure will have use as a therapeutic test from which insight will be gained about the immunopathogenesis of AIDS.

Beta-endorphin content in HIV-infected HuT78 cell line and in peripheral lymphocytes from HIV-positive subjects

We investigated beta-endorphin (BE) content in an HIV-infected cell line and in peripheral blood mononuclear cells (PBM) from HIV-positive subjects. HIV infection increased BE content in HuT78 cell line compared to uninfected cells. Accordingly, BE content was greater in HIV-positive subjects than in healthy controls, both in fresh PBM and in mitogen-stimulated or unstimulated cultured cells. Further, in PHA-stimulated cultures, BE increase was correlated with disease progression. Opioids are known to decrease immune responsiveness in vivo, and it may be that the increased BE concentrations contribute to HIV-associated immune deficiency. In HIV-positive subjects, but not in healthy controls, intracellular BE concentration was positively correlated with PHA-induced PBM proliferation. The latter data suggest an alternative explanation: that the increased BE content represents a paradoxical response of the host in an attempt to balance virus-induced immunodepression. Thus, BE may be important in fine-tuning of the immune response with its up- and downregulation dependent upon differences in immune status.

Non-Hodgkin's lymphoma in four children infected with the human immunodeficiency virus. Association with Epstein-Barr Virus and treatment

BACKGROUND

Reports on lymphoid malignancy and its treatment in children infected with human immunodeficiency virus (HIV) are limited.

METHODS

Antibodies to Epstein-Barr virus (EBV) were detected by indirect immunofluorescence. DNA was extracted from peripheral blood lymphocytes or biopsy specimens. Polymerase chain reaction was run using primers for EBV. Reaction products underwent Southern blot analysis to confirm EBV specificity. Tumor clonality was assessed by immunohistochemistry and by Southern blot analysis of immunoglobulin heavy-chain and T-cell receptor beta-gene rearrangement.

RESULTS

Within 1 year, non-Hodgkin's lymphoma (NHL) was diagnosed in four children infected with HIV. All four were EBV-seropositive and had detectable EBV DNA in peripheral blood lymphocytes. The EBV-linked disorders lymphoid interstitial pneumonia and recurrent parotid enlargement preceded NHL in three and two of the children, respectively. In all four patients, NHL involved at one time the central nervous system (CNS). All three tested NHL tissues were positive for EBV DNA: A 12-week course of chemotherapy given to two children resulted in rapid tumor regression. One of these children experienced meningeal relapse and died 16 months after diagnosis. The other child, who in addition received local irradiation of the affected eye and who underwent surgical removal of the involved ovaries, has been in continuous remission for 20 months.

CONCLUSIONS

EBV-associated NHL may be seen more frequently in pediatric patients with HIV. Treatment protocols taking into account NHL propensity for the CNS in this age group need to be developed.

Transmission from one child to another of human immunodeficiency virus type 1 with a zidovudine-resistance mutation

BACKGROUND AND METHODS. We describe a child who apparently acquired human immunodeficiency virus type 1 (HIV-1) infection in the home setting. The suspected source of infection was a child with the acquired immunodeficiency syndrome who had received zidovudine and whose virus contained a mutation associated with in vitro zidovudine resistance. The children were born to different HIV-1-infected mothers, but they lived in the same home between the ages of two and five years. Child 1 was infected perinatally; Child 2 was not and was repeatedly found to be seronegative. Child 2 was examined because of acute lymphadenopathy and had seroconverted to HIV-1 positivity. HIV-1 proviral DNA was amplified from peripheral-blood mononuclear cells and subjected to sequence analysis. Sequences from Child 2 were compared with those from Child 2's mother, Child 1, and local HIV-1-infected control children.

Improbability of harmful autoimmune responses resulting from immunization with HIV-1 envelope glycoproteins

Autoimmunity mediated by cross-reactive antibodies, elicited by HIV-1 envelope glycoproteins gp120/gp160, has been postulated to contribute to the pathogenesis of AIDS. Partial amino acid sequence homology between gp120/gp160 and several human host proteins, including MHC antigens and immunoglobulins, has been perceived as the basis for immunological cross-reactivity. Binding of antibodies from sera of HIV-1-infected individuals to selected host proteins and/or to synthetic peptides derived from them and the inhibitory activity of such sera in assays measuring the functional activity of T cells provided apparent support for the autoimmunity hypothesis, which is also relevant to the issue of safety of anti-HIV-1 vaccines. Considering the possibility that the detected autoantibodies may arise for reasons other than antibody responses to gp120/gp160, the immunological cross-reactivity between gp120/gp160 and the relevant host proteins was investigated using hyperimmune rabbit anti-gp120/gp160 and monoclonal antibodies. As determined from dilution end-point comparisons for polyclonal anti-gp120, the cross-reactivity of anti-gp120 with CD4 was undetectable (< 10(-5)%). The cross-reactivity of anti-gp120/gp160 with HLA-I and HLA-II antigens was also undetectable (< 4 x 10(-4)%) and that with other human proteins reported to have partial sequence homology with gp120/gp41 was < or = 0.013%. Anti-gp120/gp160 did not have detectable inhibitory effects in functional assays measuring proliferative T cell responses. Therefore, immunization with gp120/gp160 is unlikely to elicit harmful autoimmune responses.

High viral load in lymph nodes and latent human immunodeficiency virus (HIV) in peripheral blood cells of HIV-1-infected chimpanzees

We have examined human immunodeficiency virus type 1 (HIV-1) infection in chimpanzees by analyzing HIV-1 DNA and RNA in lymph nodes and peripheral mononuclear cells (PBMCs). Like certain asymptomatic HIV-infected persons, these chimpanzees had no detectable viral replication in their PBMCs. However, viral replication and a high viral load were observed in the lymphatic tissue. Despite the absence of viral replication in PBMCs, 1/1,000 to 1/10,000 of the PBMCs contained HIV-1 proviral DNA, and HIV transcription could be rapidly induced in these cells in vitro. These results provide direct evidence of cellular latency of HIV in vivo and suggest that HIV infection in chimpanzees may be a useful model for clinical latency of HIV infection in humans.

HIV-associated immune-mediated renal disease

Although focal glomerulosclerosis is the most common renal disease, other proliferative glomerulonephritides are encountered in HIV-infected patients. We studied four HIV-infected patients with renal insufficiency, proteinuria, and proliferative glomerulonephritis, consistent with immune-mediated disease, to investigate the role of the virus and immune complexes in the pathogenesis of the nephropathy. Circulating immune complexes (CICs) and HIV-reactive antibodies were measured and characterized in each patient. Renal biopsy tissue was acid eluted, and the eluate analyzed. DNA extracted from biopsies was subjected to the polymerase chain reaction (PCR) to detect HIV genome. CICs were detected in each patient: an IgA-p24 HIV antigen complex and an IgG antibody-gp 120 HIV antigen complex in two patients; two patients had an IgG-p24 HIV antigen complex. Identical complexes were eluted from renal tissue in the first three patients; p24 HIV antigen, and complement from the fourth. The eluted antibodies reacted with the HIV antigens from the isolated CICs. Direct immunofluorescence for viral antigen in the eluted glomerular tissue revealed HIV antigens; PCR confirmed the presence of gag genome in all four biopsies. We conclude both circulating and in-situ HIV antigen-specific immune complexes may be associated with glomerulonephritis in HIV infected patients. Viral incorporation into renal tissue may be important in the pathogenesis of HIV-associated renal disease.

Cytokine involvement in viral permissiveness and the progression of HIV disease

Many viruses have evolved novel means of exploiting host defense mechanisms for their own survival. This exploitation may be best exemplified by the interrelationships between certain viruses and the host cytokine networks. Many viruses, including the human immunodeficiency virus type-1 (HIV-1), rely on the liberation and cellular action of host immune cytokines to expand their host cell range, to regulate their cellular expression, and to maintain their dormant state until the proper extracellular conditions arise. As again exemplified by HIV-1, viruses may also take an active role regulating cytokine expression and cell surface cytokine receptors. Because the viral life cycle, and in particular the HIV-1 life cycle, is so intertwined with cytokine regulatory networks, these networks represent potential points for therapeutic intervention. As our understanding of cellular cytokine pathways involved in viral infection and replication continues to expand, so too will our ability to design rational anti-viral therapies to alter multiple steps along the viral life cycle.

Multifactorial nature of human immunodeficiency virus disease: implications for therapy

The immunopathogenic mechanisms underlying human immunodeficiency virus (HIV) disease are extremely complex; the disease process is multifactorial with multiple overlapping phases. Viral burden is substantial and viral replication occurs throughout the entire course of HIV infection. Inappropriate immune activation and elevated secretion of certain cytokines compound the pathogenic process. Profound immunosuppression ultimately occurs together with a disruption of the microenvironment of the immune system, which is probably unable to regenerate spontaneously. Thus, therapeutic strategies in HIV disease must not be unidimensional, but rather must be linked to the complex pathogenic components of the disease and must address where feasible each of the recognized pathogenic processes for the possibility of therapeutic intervention.

1992 AAD Award for Excellence in Education: The Integrated Basic and Clinical Science Conference Series at the University of Texas Southwestern Medical Center

This article was written to share information concerning the establishment and implementation of a successful, integrated basic and clinical science conference series for resident trainees in dermatology. We discuss the underlying philosophy and describe the concepts employed in, and the dynamics that have resulted from, this educational experiment. Finally, we include the schedule and references for the 1993-1994 academic year.

CD8+ T lymphocyte-mediated inhibition of HIV-1 long terminal repeat transcription: a novel antiviral mechanism

HIV-1 infection evokes a vigorous antiviral response that may participate in resolving the initial peak of plasma viremia and maintenance of the asymptomatic state. CD8+ T lymphocytes of HIV-1-infected individuals play a critical role in the cellular anti-HIV response. In agreement with previous reports, we observed a potent suppressive effect on HIV-1 production from autologous CD4+ T lymphocytes by CD8+ T lymphocytes from asymptomatic HIV-1-infected individuals. To elucidate the mechanism(s) of the nonlytic suppressive antiviral activity, we examined the effect of CD8+ T lymphocytes on the transcriptional activity of the HIV-1 promoter (HIV-LTR). CD8+ lymphocytes from HIV-1-infected asymptomatic individuals suppressed tat-mediated HIV-LTR transcription in CD4+ lymphocytes. HIV-LTR transcriptional activity was suppressed by CD8 lymphocytes to an extent similar to tat-mediated transcription whereas CMV immediate early gene promoter activity was not affected. In contrast to the suppressive effect seen with CD8+ lymphocytes from HIV-1-infected individuals, CD8+ lymphocytes from uninfected individuals did not significantly inhibit tat-mediated or HIV-LTR transcription. The transcriptional inhibitory activity was not MHC class I restricted and could be mediated by a soluble factor(s). Supernatants from some CD8+ T lymphocyte cultures from HIV-1+ individuals exerted an inhibitory effect on tat-mediated HIV-LTR transcription comparable to that seen with CD8+ cells. In conclusion, CD8+ lymphocytes from asymptomatic HIV-1+ individuals could suppress virus production by inhibiting HIV-1 gene expression.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunologic targets of HIV infection: T cells. NICHD IVIG Clinical Trial Group, and the NHLBI P2C2 Pediatric Pulmonary and Cardiac Complications of HIV Infection Study Group

One of the principal targets of HIV infection is the human peripheral blood CD4+ T cell, resulting in progressive CD4+ lymphocyte loss. Hypothesized mechanisms for this loss include apoptosis, cytolytic reactions, V-beta gene deletion of the T-cell receptor (TCR) by superantigens, CD4+ lymphocyte syncytium formation, and autoimmune reactions. In adults with HIV infection, the critical decline in CD4+ lymphocyte number that heralds the onset of AIDS-defining conditions is well characterized, whereas in infants and children the critical level of CD4+ cells predisposing to the development of AIDS-defining conditions or mortality is not fully characterized, due to an incomplete knowledge of CD4+ lymphocyte number and changes with age in normal and HIV-infected children. In a prospective study of 317 infants born to HIV-infected women, early results show that the monthly change in absolute CD4+ lymphocyte number over a 3- to 9-month period in HIV-infected infants was -109 cells/mm3 per month, at least double the rate of decline measured in HIV-noninfected infants in the study or that calculated from normal infants' values reported in the literature. In other clinical studies in HIV-infected infants and children, it was possible to study the effect of low CD4+ cell counts on clinical status and mortality. In HIV-infected pediatric patients younger than 1 year, it was possible to correlate low CD4+ cell number with advanced disease status (CDC pediatric class P-2). It was also possible to correlate extremely low CD4+ cell counts (< 200 cells/mm3) in HIV-infected children with a significant risk of mortality within the next 3 months of life. Sequential CD4+ cell analysis of HIV-high-risk infants will delineate the rate of HIV-related decline in CD4+ cells, thus facilitating the diagnosis of HIV infection and aiding in identification of HIV-infected children at high risk of disease progression or death.

Zidovudine. An update of its pharmacodynamic and pharmacokinetic properties, and therapeutic efficacy

Zidovudine remains the mainstay in the treatment of patients infected with human immunodeficiency virus (HIV). The drug delays disease progression to acquired immunodeficiency syndrome (AIDS) and to AIDS-related complex (ARC), reduces opportunistic infections, and increases survival in patients with advanced HIV infection. There is evidence to suggest that zidovudine also delays disease progression in patients with mild symptomatic disease. Although one study has shown zidovudine to have no significant beneficial effects on survival or disease progression in patients with asymptomatic HIV infection, several other studies have shown zidovudine to delay disease progression in this patient group. Results from related ongoing studies are awaited with interest. Zidovudine reduces the incidence of AIDS dementia complex (ADC) and appears to prolong survival in these patients, and improves other neurological complications of HIV infection. The drug also appears to enhance the efficacy of interferon-alpha in patients with Kaposi's sarcoma. Although zidovudine is widely used as postexposure prophylaxis following accidental exposure to HIV, its efficacy in preventing seroconversion is unclear. Whether zidovudine prevents vertical transmission also remains to be determined. The overall efficacy of zidovudine in the treatment of children with HIV infection appears similar to that in adults despite more rapid disease progression in younger patients. Zidovudine-resistant isolates can emerge as early as after 2 months' therapy, and primary infection with zidovudine-resistant strains has been documented. Both zidovudine resistance and the syncytium-inducing HIV phenotype appear to be associated with poor clinical outcome. However, zidovudine resistance may revert on drug withdrawal or switching to an alternative therapy. Zidovudine-associated haematotoxicity may be dose-limiting. Nonhaematological adverse events associated with zidovudine therapy are generally mild and usually resolve spontaneously. Dosages of approximately 500 to 600 mg/day appear to be at least as effective as dosages of 1200 to 1500 mg/day and are better tolerated in patients with less advanced disease. However, optimal dosage are unclear. Despite beneficial effects, zidovudine monotherapy is not curative. There is evidence to suggest that the concomitant administration of zidovudine with didanosine or zalcitabine is effective in patients with HIV disease progression despite receiving zidovudine monotherapy, and there is some evidence that concomitant zidovudine plus didanosine therapy is more effective than alternating monotherapy. However, results from studies of combination therapy in asymptomatic patients, and from comparative combination therapy studies are awaited. Cotherapy with agents that augment haematopoiesis allows the continuation of therapeutic zidovudine dosages.(ABSTRACT TRUNCATED AT 400 WORDS)

Lack of selective V beta deletion in peripheral CD4+ T cells of human immunodeficiency virus-infected infants

To investigate the possibility of super-antigen-mediated deletions of T cells expressing particular T cell receptor V beta (TcR V beta) gene segments during human immunodeficiency virus (HIV) infection, TcR V beta usage in CD4+ and CD8+ subsets was analyzed in a cohort of infants maternally infected by HIV and in a group of healthy neonates. We used a semi-quantitative anchored polymerase chain reaction technique together with cytofluorographic analysis with anti-V beta monoclonal antibodies. The representation of the 24 V beta families in CD4+ and CD8+ T cells from normal neonates was very similar to that in adults. Preferential expression of V beta 2 in the CD4+ subset was observed in both the neonates and in healthy adults. The representation of the 24 V beta families in peripheral CD4+ T cells from the HIV-infected infants showed no selective V beta deletion, even when the CD4+ subset was globally depleted. Moreover, the main characteristics of the control group (predominance of certain V beta families and V beta 2 skewing towards the CD4+ subset) were also present in all the HIV-infected infants.

CD8+ cytotoxic T cell therapy of cytomegalovirus and HIV infection

The development of CD8+ cytotoxic T cell responses to viral pathogens is crucial for the prompt resolution of acute infections and for the control of viruses which persist in the host. Thus, cytomegalovirus often causes life threatening disease in immunosuppressed humans who fail to develop or maintain CD8+ cytotoxic T cells. Similarly, the loss of CD8+ cytotoxic T cell responses to HIV correlates with the development of AIDS. Recent investigations in the immunobiology of cytomegalovirus and HIV have resulted in the application of immunotherapeutic strategies designed to reconstitute or augment deficient CD8+ cytotoxic T cell responses to these human pathogens.

Immunodeficiency-inducing retroviruses

The plethora of disease syndromes (dystrophy of various organ systems, malignancies and opportunistic infections) caused by HIV are all potentiated by the profound virus-induced immunosuppression that accompanies this infection. The mechanism of this severe immunosuppression is poorly understood and the subject is currently being pursued in studies of HIV-infected patients and in animals infected with other immunodeficiency-inducing retroviruses.

Kinetics of human immunodeficiency virus type 1 (HIV-1) DNA and RNA synthesis during primary HIV-1 infection

HIV-1 replication and viral burden in peripheral blood mononuclear cells (PBMC) have been reported to be high in primary infection but generally very low during the prolonged period of clinical latency. It is uncertain precisely when this transition occurs during the HIV-1 infection and what the relationship is between the changes in HIV-1 replication versus the clearance of infected cells in the overall control of viral replication. In the present study, the kinetics of viral burden (i.e., frequency of HIV-1-infected cells) and replication during primary and early-chronic infection were analyzed in PBMC of four acutely infected individuals. High frequencies of HIV-1-infected cells and high levels of virus replication were observed in PBMC after primary HIV-1 infection. Down-regulation of virus replication in PBMC was observed in all four patients coincident with the emergence of HIV-1-specific immune responses. Other parameters of virus replication, such as circulating plasma p24 antigen and plasma viremia showed similar kinetics. In contrast, a significant decline in viral burden in PBMC was observed in only one of four patients. These results indicate that the down-regulation in the levels of virus replication associated with the clinical transition from acute to chronic infection does not necessarily reflect a reduction in viral burden, thus suggesting the involvement of additional factors. Identification of these factors will be important in elucidating the host mechanisms involved in the early control of HIV-1 infection and disease.

Human immunodeficiency virus type 1 Gag protein binds to cyclophilins A and B

Retroviral Gag protein is capable of directing the assembly of virion particles independent of other retroviral elements and plays an important role early in the infection of a cell. Using the GAL4 two hybrid system, we screened a cDNA expression library and identified two host proteins, cyclophillins (CyPs) A and B, which interact specifically with the human immunodeficiency virus type 1 (HIV-1) Gag polyprotein Pr55gag. Glutathione S-transferase-CyP fusion proteins bind tightly to Pr55gag in vitro, as well as to the HIV-1 capsid protein p24. Cyclosporin A efficiently disrupts the Gag-CyPA interaction and less efficiently disrupts the Gag-CyPB interaction. The Gag-CyP interaction may be important for the HIV-1 life cycle and may be relevant to the pathology caused by this immunosuppressive virus.