Sequence homology and morphologic similarity of HTLV-III and visna virus, a pathogenic lentivirus

Corneal Regeneration Using Gene Therapy Approaches

One of the most remarkable advancements in medical treatments of corneal diseases in recent decades has been corneal transplantation. However, corneal transplants, including lamellar strategies, have their own set of challenges, such as graft rejection, delayed graft failure, shortage of donor corneas, repeated treatments, and post-surgical complications. Corneal defects and diseases are one of the leading causes of blindness globally; therefore, there is a need for gene-based interventions that may mitigate some of these challenges and help reduce the burden of blindness. Corneas being immune-advantaged, uniquely avascular, and transparent is ideal for gene therapy approaches. Well-established corneal surgical techniques as well as their ease of accessibility for examination and manipulation makes corneas suitable for in vivo and ex vivo gene therapy. In this review, we focus on the most recent advances in the area of corneal regeneration using gene therapy and on the strategies involved in the development of such therapies. We also discuss the challenges and potential of gene therapy for the treatment of corneal diseases. Additionally, we discuss the translational aspects of gene therapy, including different types of vectors, particularly focusing on recombinant AAV that may help advance targeted therapeutics for corneal defects and diseases.

The Role of Animal Research in Pandemic Responses

The significant advances made by the global scientific community during the COVID-19 pandemic, exemplified by the development of multiple SARS-CoV-2 vaccines in less than 1 y, were made possible in part because of animal research. Historically, animals have been used to study the characterization, treatment, and prevention of most of the major infectious disease outbreaks that humans have faced. From the advent of modern 'germ theory' prior to the 1918 Spanish Flu pandemic through the more recent Ebola and Zika virus outbreaks, research that uses animals has revealed or supported key discoveries in disease pathogenesis and therapy development, helping to save lives during crises. Here we summarize the role of animal research in past pandemic and epidemic response efforts, as well as current and future considerations for animal research in the context of infectious disease research.

The contribution of bovines to human health against viral infections

In the last 40 years, novel viruses have evolved at a much faster pace than other pathogens. Viral diseases pose a significant threat to public health around the world. Bovines have a longstanding history of significant contributions to human nutrition, agricultural, industrial purposes, medical research, drug and vaccine development, and livelihood. The life cycle, genomic structures, viral proteins, and pathophysiology of bovine viruses studied in vitro paved the way for understanding the human counterparts. Calf model has been used for testing vaccines against RSV, papillomavirus vaccines and anti-HCV agents were principally developed after using the BPV and BVDV model, respectively. Some bovine viruses-based vaccines (BPIV-3 and bovine rotaviruses) were successfully developed, clinically tried, and commercially produced. Cows, immunized with HIV envelope glycoprotein, produced effective broadly neutralizing antibodies in their serum and colostrum against HIV. Here, we have summarized a few examples of human viral infections for which the use of bovines has contributed to the acquisition of new knowledge to improve human health against viral infections covering the convergence between some human and bovine viruses and using bovines as disease models. Additionally, the production of vaccines and drugs, bovine-based products were covered, and the precautions in dealing with bovines and bovine-based materials.

HIV replication and latency in monocytes and macrophages

The relevance of monocyte and macrophage reservoirs in virally suppressed people with HIV (vsPWH) has previously been debatable. Macrophages were assumed to have a moderate life span and lack self-renewing potential. However, recent studies have challenged this dogma and now suggest an important role of these cell as long-lived HIV reservoirs. Lentiviruses have a long-documented association with macrophages and abundant evidence exists that macrophages are important target cells for HIV in vivo. A critical understanding of HIV infection, replication, and latency in macrophages is needed in order to determine the appropriate method of measuring and eliminating this cellular reservoir. This review provides a brief discussion of the biology and acute and chronic infection of monocytes and macrophages, with a more substantial focus on replication, latency and measurement of the reservoir in cells of myeloid origin.

Brain macrophages harbor latent, infectious simian immunodeficiency virus

: The current review examines the role of brain macrophages, that is perivascular macrophages and microglia, as a potential viral reservoir in antiretroviral therapy (ART) treated, simian immunodeficiency virus (SIV)-infected macaques. The role, if any, of latent viral reservoirs of HIV and SIV in the central nervous system during ART suppression is an unresolved issue. HIV and SIV infect both CD4 lymphocytes and myeloid cells in blood and tissues during acute and chronic infection. HIV spread to the brain occurs during acute infection by the infiltration of activated CD4 lymphocytes and monocytes from blood and is established in both embryonically derived resident microglia and monocyte-derived perivascular macrophages. ART controls viral replication in peripheral blood and cerebrospinal fluid in HIV-infected individuals but does not directly eliminate infected cells in blood, tissues or brain. Latently infected resting CD4 lymphocytes in blood and lymphoid tissues are a well recognized viral reservoir that can rebound once ART is withdrawn. In contrast, central nervous system resident microglia and perivascular macrophages in brain have not been examined as potential reservoirs for HIV during suppressive ART. Macrophages in tissues are long-lived cells that are HIV and SIV infected in tissues such as gut, lung, spleen, lymph node and brain and contribute to ongoing inflammation in tissues. However, their potential role in viral persistence and latency or their potential to rebound in the absence ART has not been examined. It has been shown that measurement of HIV latency by HIV DNA PCR in CD4 lymphocytes overestimates the size of the latent reservoirs of HIV that contribute to rebound that is cells containing the genomes of replicative viruses. Thus, the quantitative viral outgrowth assay has been used as a reliable measure of the number of latent cells that harbor infectious viral DNA and, may constitute a functional latent reservoir. Using quantitative viral outgrowth assays specifically designed to quantitate latently infected CD4 lymphocytes and myeloid cells in an SIV macaque model, we demonstrated that macrophages in brain harbor SIV genomes that reactivate and produce infectious virus in this assay, demonstrating that these cells have the potential to be a reservoir.

A Quantitative Approach to SIV Functional Latency in Brain Macrophages

Lentiviruses are retroviruses that primarily infect myeloid cells, leading to acute inflammatory infections in many tissues particularly, lung, joints and the central nervous system (CNS). Acute infection by lentiviruses is followed by persistent/latent infections that are not cleared by the host immune system. HIV and SIV are lentiviruses that also infect CD4+ lymphocytes as well as myeloid cells in blood and multiple tissues. HIV infection of myeloid cells in brain, lung and heart cause tissue specific diseases as well as infect cells in gut, lymph nodes and spleen. AIDS dementia and other tissue specific disease are observed when infected individuals are immunosuppressed and the number of circulating CD4+ T cells declines to low levels. Antiretroviral therapy (ART) controls viral spread and dramatically changes the course of immunodeficiency and AIDS dementia. However, ART does not eliminate virus-infected cells. Brain macrophages contain HIV DNA and may represent a latent reservoir that persists. HIV latency in CD4+ lymphocytes is the main focus of current research and concern in efforts to eradicate HIV. However, a number of studies have demonstrated that myeloid cells in blood and tissues of ART suppressed individuals harbor HIV DNA. The resident macrophages in tissues such as brain (microglia), spleen (red pulp macrophages) and alveolar macrophages in lung are derived from the yolk sac and can self renew. The question of the latent myeloid reservoir in HIV has not been rigorously examined and its potential as a barrier to eradication been considered. Using a well characterized SIV ART suppressed, non-human primate (NHP) model, our laboratory developed the first quantitative viral outgrowth assay (QVOA) designed to evaluate latently infected CD4+ lymphocytes and more recently developed a similar protocol for the assessment of latently infected myeloid cells in blood and brain. Using an SIV ART model, it was demonstrated that myeloid cells in blood and brain harbor latent SIV that can be reactivated and produce infectious virus in vitro. These studies demonstrate for the first time that myeloid cells have the potential to be a latent reservoir of HIV that produces infectious virus that can be reactivated in the absence of ART and during HIV eradication strategies. Graphical Abstract.

SIV Latency in Macrophages in the CNS

Lentiviruses infect myeloid cells, leading to acute infection followed by persistent/latent infections not cleared by the host immune system. HIV and SIV are lentiviruses that infect CD4+ lymphocytes in addition to myeloid cells in blood and tissues. HIV infection of myeloid cells in brain, lung, and heart causes tissue-specific diseases that are mostly observed during severe immunosuppression, when the number of circulating CD4+ T cells declines to exceeding low levels. Antiretroviral therapy (ART) controls viral replication but does not successfully eliminate latent virus, which leads to viral rebound once ART is interrupted. HIV latency in CD4+ lymphocytes is the main focus of research and concern when HIV eradication efforts are considered. However, myeloid cells in tissues are long-lived and have not been routinely examined as a potential reservoir. Based on a quantitative viral outgrowth assay (QVOA) designed to evaluate latently infected CD4+ lymphocytes, a similar protocol was developed for the assessment of latently infected myeloid cells in blood and tissues. Using an SIV ART model, it was demonstrated that myeloid cells in blood and brain harbor latent SIV that can be reactivated and produce infectious virus in vitro, demonstrating that myeloid cells have the potential to be an additional latent reservoir of HIV that should be considered during HIV eradication strategies.

Can HIV-infected patients undergo cochlear implantation?

OBJECTIVE

HIV-infected patients have an increased risk of developing sensorineural hearing loss. Cochlear implantation can be a mean of rehabilitating such patients.

METHODS

A 36-year-old HIV-infected male with bilateral profound sensorineural hearing loss underwent cochlear implantation after exclusion of medical and radiological contraindications. The patient was followed up for 2 years to assess the audiological outcome.

RESULTS

After a follow up of 2 years, the patient has attained good functional results not experienced any complications. Conculsion: Cochlear implantation can restore hearing to HIV-infected patients with profound hearing loss due to cochlear impairment. This helps in both social and vocational rehabilitation and can improve the quality of life of such patients.

Infectious Entry Pathway Mediated by the Human Endogenous Retrovirus K Envelope Protein

Endogenous retroviruses (ERVs), the majority of which exist as degraded remnants of ancient viruses, comprise approximately 8% of the human genome. The youngest human ERVs (HERVs) belong to the HERV-K(HML-2) subgroup and were endogenized within the past 1 million years. The viral envelope protein (ENV) facilitates the earliest events of endogenization (cellular attachment and entry), and here, we characterize the requirements for HERV-K ENV to mediate infectious cell entry. Cell-cell fusion assays indicate that a minimum of two events are required for fusion, proteolytic processing by furin-like proteases and exposure to acidic pH. We generated an infectious autonomously replicating recombinant vesicular stomatitis virus (VSV) in which the glycoprotein was replaced by HERV-K ENV. HERV-K ENV imparts an endocytic entry pathway that requires dynamin-mediated membrane scission and endosomal acidification but is distinct from clathrin-dependent or macropinocytic uptake pathways. The lack of impediments to the replication of the VSV core in eukaryotic cells allowed us to broadly survey the HERV-K ENV-dictated tropism. Unlike extant betaretroviral envelopes, which impart a narrow species tropism, we found that HERV-K ENV mediates broad tropism encompassing cells from multiple mammalian and nonmammalian species. We conclude that HERV-K ENV dictates an evolutionarily conserved entry pathway and that the restriction of HERV-K to primate genomes reflects downstream stages of the viral replication cycle.

IMPORTANCE

Approximately 8% of the human genome is of retroviral origin. While many of those viral genomes have become inactivated, some copies of the most recently endogenized human retrovirus, HERV-K, can encode individual functional proteins. Here, we characterize the envelope protein (ENV) of the virus to define how it mediates infection of cells. We demonstrate that HERV-K ENV undergoes a proteolytic processing step and triggers membrane fusion in response to acidic pH--a strategy common to many viral fusogens. Our data suggest that the infectious entry pathway mediated by this ENV requires endosomal acidification and the GTPase dynamin but does not require clathrin-dependent uptake. In marked contrast to other betaretroviruses, HERV-K ENV imparts broad species tropism in cultured cells. This work provides new insights into the entry pathway of an extinct human virus and provides a powerful tool to further probe the endocytic route by which HERV-K infects cells.

HIV-1-based lentiviral vectors

Numerous viral vectors have been developed for the delivery of transgenes to specific target cells. For persistent transgene expression, vectors based on retroviruses are attractive delivery vehicles because of their ability to stably integrate their DNA into the host cell genome. Initially, vectors based on simple retroviruses were the vector of choice for such applications. However, these vectors can only transduce actively dividing cells. Therefore, much interest has turned to retroviral vectors based on the lentivirus genus because of their ability to transduce both dividing and non-dividing cells. The best characterized lentiviral vectors are derived from the human immunodeficiency virus type 1 (HIV-1). This chapter describes the basic features of the HIV-1 replication cycle and the many improvements reported for the lentiviral vector systems to increase the safety and efficiency. We also provide practical information on the production of HIV-1 derived lentiviral vectors, the cell transduction protocol and a method to determine the transduction titers of a lentiviral vector.

Bovine immunodeficiency virus: a lentiviral infection

The bovine immunodeficiency virus (BIV) is a lentivirus which is known to infect cattle worldwide. Though serological and genomic evidence of BIV in cattle has been found throughout the world, isolation of the virus has been reported only from few places. Very little is known about its impact on animal health status, pathogenesis and mode of transmission. BIV is considered generally non-pathogenic and is not known to cause any serious disease in cattle. BIV is genetically and antigenically related to Jembrana disease virus (JDV), the cause of an acute disease in Bali cattle (Bos javanicus) and human immunodeficiency virus, the cause of acquired immunodeficiency syndrome in human. Therefore, it is important to monitor the presence of BIV in cattle to keep vigil over its possible evolution in its natural host to emerge as pathogenic lentivirus like JDV. Differentiation of BIV infection in cattle from the acutely pathogenic JDV is important for diagnosis of the latter. Currently, BIV is considered as a safe model for understanding the complex genome of lentiviruses. Further research on BIV is indeed needed to elucidate its possible role in animal health as well as for insight into the molecular mechanisms adopted by related lentiviruses.

Disinformation squared: was the HIV-from-Fort-Detrick myth a Stasi success?

BACKGROUND

When in May 1983 the acquired immunodeficiency syndrome (AIDS) was first securely attributed to a virus, eventually called the human immunodeficiency virus (HIV), many controversies arose. Among these was one centering on HIV's origin. A startling hypothesis, called here the "HIV-from-Fort-Detrick myth," asserted that HIV had been a product, accidental or intentional, of bioweaponry research. While its earliest identifiable contributors were in the West, this myth's most dynamic propagators were in the East. The Soviet security service, the KGB, took "active measures" to create and disseminate AIDS disinformation beginning no later than July 1983 and ending no earlier than October 1987. The East German security service, a complex bureaucracy popularly known as "the Stasi," was involved, too, but how early, how deeply, how uniformly, how ably, and how successfully has not been clear. Following German reunification, claims arose attributing to the Stasi the masterful execution of ingenious elements in a disinformation campaign they helped shape and soon came to dominate. We have tested these claims.

QUESTION

Was the HIV-from-Fort-Detrick myth a Stasi success?

METHODS

Primary sources were documents and photographs assembled by the Ministry of State Security (MfS) of the German Democratic Republic (GDR or East Germany), the Ministry of Interior of the People's Republic of Bulgaria, and the United States Department of State; the estate of myth principals Jakob and Lilli Segal; the "AIDS box" in the estate of East German literary figure Stefan Heym; participant-observer recollections, interviews, and correspondence; and expert interviews. We examined secondary sources in light of primary sources.

FINDINGS

The HIV-from-Fort-Detrick myth had debuted in print in India in 1983 and had been described in publications worldwide prior to 1986, the earliest year for which we found any Stasi document mentioning the myth in any context. Many of the myth's exponents were seemingly independent conspiracy theorists. Its single most creative exponent was Jakob Segal, an idiosyncratic Soviet biologist long resident in, and long retired in, the GDR. Segal applied to the myth a thin but tenacious layer of plausibility. We could not exclude a direct KGB influence on him but found no evidence demonstrating it. The Stasi did not direct his efforts and had difficulty tracking his activities. The Stasi were prone to interpretive error and self-aggrandizement. They credited themselves with successes they did not achieve, and, in one instance, failed to appreciate that a major presumptive success had actually been a fiasco. Senior Stasi officers came to see the myth's propagation as an embarrassment threatening broader interests, especially the GDR's interest in being accepted as a scientifically sophisticated state. In 1986, 1988, and 1989, officers of HV A/X, the Stasi's disinformation and "active measures" department, discussed the myth in meetings with the Bulgarian secret service. In the last of these meetings, HV A/X officers tried to interest their Bulgarian counterparts in taking up, or taking over, the myth's propagation. Further efforts, if any, were obscured by collapse of the East German and Bulgarian governments.

CONCLUSION

No, the HIV-from-Fort-Detrick myth was not a Stasi success. Impressions to the contrary can be attributed to reliance on presumptions, boasts, and inventions. Presumptions conceding to the Stasi an extraordinary operational efficiency and an irresistible competence - qualities we could not confirm in this case - made the boasts and inventions more convincing than their evidentiary basis, had it been known, would have allowed. The result was disinformation about disinformation, a product we call "disinformation squared."

Somatic Populations of PGT135-137 HIV-1-Neutralizing Antibodies Identified by 454 Pyrosequencing and Bioinformatics

Select HIV-1-infected individuals develop sera capable of neutralizing diverse viral strains. The molecular basis of this neutralization is currently being deciphered by the isolation of HIV-1-neutralizing antibodies. In one infected donor, three neutralizing antibodies, PGT135–137, were identified by assessment of neutralization from individually sorted B cells and found to recognize an epitope containing an N-linked glycan at residue 332 on HIV-1 gp120. Here we use next-generation sequencing and bioinformatics methods to interrogate the B cell record of this donor to gain a more complete understanding of the humoral immune response. PGT135–137-gene family specific primers were used to amplify heavy-chain and light-chain variable-domain sequences. Pyrosequencing produced 141,298 heavy-chain sequences of IGHV4-39 origin and 87,229 light-chain sequences of IGKV3-15 origin. A number of heavy and light-chain sequences of ∼90% identity to PGT137, several to PGT136, and none of high identity to PGT135 were identified. After expansion of these sequences to include close phylogenetic relatives, a total of 202 heavy-chain sequences and 72 light-chain sequences were identified. These sequences were clustered into populations of 95% identity comprising 15 for heavy chain and 10 for light chain, and a select sequence from each population was synthesized and reconstituted with a PGT137-partner chain. Reconstituted antibodies showed varied neutralization phenotypes for HIV-1 clade A and D isolates. Sequence diversity of the antibody population represented by these tested sequences was notably higher than observed with a 454 pyrosequencing-control analysis on 10 antibodies of defined sequence, suggesting that this diversity results primarily from somatic maturation. Our results thus provide an example of how pathogens like HIV-1 are opposed by a varied humoral immune response, derived from intrinsic mechanisms of antibody development, and embodied by somatic populations of diverse antibodies.

Retroviral coinfections: HIV and HTLV: taking stock of more than a quarter century of research

Retroviral coinfections with HIV-1 and HTLV-1 or with HIV-1 and HTLV-2 occur with variable frequencies throughout the world with the highest prevalence in large metropolitan areas in the Americas, Europe, and Africa. The recognition that retroviral coinfections exist dates back to the discovery of HIV-1 over 25 years ago. Despite the large body of published information regarding the biological and clinical significance of retroviral coinfections, controversy throughout several decades of research was fueled by several flawed epidemiologic studies and anecdotal reports that were not always supported with ample statistical and scientific evidence. However, the growing consensus obtained from recent systematic and well-devised research provides support for at least three conclusions: (1) HIV-1 and HTLV-1 coinfections are often seen in the context of patients with high CD4(+) T cell counts presenting with lymphoma or neurological complications; (2) HIV-1 and HTLV-2 coinfections have been linked in some cases to a "long term nonprogressor" phenotype; and (3) differential function and/or overexpression of the HTLV-1 and HTLV-2 Tax proteins likely play a pivotal role in the clinical and immunologic manifestations of HIV/HTLV-1 and -2 coinfections. This review will recount the chronology of work regarding retroviral coinfections from 1983 through the present.

Non-polymeric nano-carriers in HIV/AIDS drug delivery and targeting

Development of an effective drug delivery approach for the treatment of HIV/AIDS is a global challenge. The conventional drug delivery approaches including Highly Active Anti Retroviral Therapy (HAART) have increased the life span of the HIV/AIDS patient. However, the eradication of HIV is still not possible with these approaches due to some limitations. Emergence of polymeric and non-polymeric nanotechnological approaches can be opportunistic in this direction. Polymeric carriers like, dendrimers and nanoparticles have been reported for the targeting of anti HIV drugs. The synthetic pathways as well polymeric framework create some hurdles in their successful formulation development as well as in the possible drug delivery approaches. In the present article, we have discussed the general physiological aspects of the infection along with the relevance of non-polymeric nanocarriers like liposomes, solid lipid nanoparticles (SLN), ethosomes, etc. in the treatment of this disastrous disease.

Correlation between SIV Tat evolution and AIDS progression in cerebrospinal fluid of morphine-dependent and control macaques infected with SIV and SHIV

Morphine abuse has been associated with higher virus replication and accelerated disease progression in a non-human primate model of AIDS. In our previous report, we have shown that 50% of morphine-addicted macaques progress rapidly and that 2/3 of the rapid progressors exhibit severe neuropathogenesis. In this report, we examined the sequence evolution of the SIV Tat protein, known to participate in AIDS neuropathology, in the cerebrospinal fluid (CSF) of morphine-dependent and control macaques over the first 20 weeks of infection. The CSF SIV Tat evolution was found to be inversely related with disease progression, and the highly neuropathogenic inoculum clone sequence was the prevalent CSF form in rapid progressors. Divergence from the inoculum clone was significantly greater in both morphine-dependent normal progressors and control macaques than in the morphine-dependent rapid progressors. Furthermore, we also found evidence of a trend that morphine alters the type of mutation, resulting in an enhanced ratio of transitions to transversions (Ts:Tv). Rapid disease exacerbates this trend and appears to influence the distribution of nonsynonymous changes in the first exon of SIV tat, with a clear majority of mutations occurring in the C-terminal half of the protein where the known functionally important domains reside. Thus, morphine abuse may change the nature and extent of mutations that drive viral evolution.

HIV pathogenesis: knowledge gained after two decades of research

Great progress has been made in our understanding of HIV since its initial discovery about 20 years ago. The ability of HIV to infect CD4+ lymphocytes and a wide variety of other cells in the body is appreciated, as is its role in immunologic, gastrointestinal, and brain disorders. HIV enters cells via the CD4 molecule, chemokine co-receptors (CXCR4, CCR5), and other cell-surface proteins. Several accessory virus-associated genes (e.g., Rev, Tat, Nef) have uncovered unique pathways that can also be observed in normal cells. Recently, the discovery of natural cellular resistant factors (APOBEC3G and TRIM5a) has provided avenues for novel antiviral therapies. Studies of long-term survivors have given insight into immune responses that control HIV and can prevent infection. Neutralizing antibodies and CD8+ cell cytotoxic responses, as well as plasmacytoid dendritic cells and CD8+ cell non-cytotoxic antiviral responses, are adaptive and innate immune activities mediating this anti-HIV effect. HIV vaccine studies have indicated that conventional approaches do not work against this integrated intracellular parasite. While much has been learned about HIV, more details are needed about its infection cycle and its pathologic effects in the body. The past 20 years have yielded important information on HIV/AIDS that should lead to effective anti-HIV therapies and a vaccine.

The human T-cell leukemia virus type 1 (HTLV-1): New insights into the clinical aspects and molecular pathogenesis of adult t-cell leukemia/lymphoma (ATLL) and tropical spastic paraparesis/HTLV-associated myelopathy (TSP/HAM)

Human T-cell leukemia virus type 1 (HTLV-1) was the first human retrovirus to be identified in the early 1980s. The isolation and identification of a related virus, HTLV-2, and the distantly related human immunodeficiency virus (HIV) immediately followed. Of the three retroviruses, two are associated definitively with specific diseases, HIV, with acquired immune deficiency syndrome (AIDS) and HTLV-1, with adult T-cell leukemia/lymphoma (ATLL) and tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). While an estimated 10-20 million people worldwide are infected with HTLV-I, infection is endemic in the Caribbean, parts of Africa, southwestern Japan, and Italy. Approximately 4% of HTLV-I infected individuals develop ATLL, a disease with a poor prognosis. The clinical manifestations of infection and the current biology of HTLV viruses with emphasis on HTLV-1 are discussed in detail. The implications for improvements in diagnosis, treatment, intervention, and vaccination are included, as well as a discussion of the emergence of HTLV-1 and -2 as copathogens among HIV-1-infected individuals.

Gene therapy in the cornea

Technological advances in the field of gene therapy has prompted more than three hundred phase I and phase II gene-based clinical trials for the treatment of cancer, AIDS, macular degeneration, cardiovascular, and other monogenic diseases. Besides treating diseases, gene transfer technology has been utilized for the development of preventive and therapeutic vaccines for malaria, tuberculosis, hepatitis A, B and C viruses, AIDS, and influenza. The potential therapeutic applications of gene transfer technology are enormous. The cornea is an excellent candidate for gene therapy because of its accessibility and immune-privileged nature. In the last two decades, various viral vectors, such as adeno, adeno-associated, retro, lenti, and herpes simplex, as well as non-viral methods, were examined for introducing DNA into corneal cells in vitro, in vivo and ex vivo. Most of these studies used fluorescent or non-fluorescent marker genes to track the level and duration of transgene expression in corneal cells. However, limited studies were directed to evaluate prospects of gene-based interventions for corneal diseases or disorders such as allograft rejection, laser-induced post-operative haze, herpes simplex keratitis, and wound healing in animal models. We will review the successes and obstacles impeding gene therapy approaches used for delivering genes into the cornea.

Intrapatient alterations in the human immunodeficiency virus type 1 gp120 V1V2 and V3 regions differentially modulate coreceptor usage, virus inhibition by CC/CXC chemokines, soluble CD4, and the b12 and 2G12 monoclonal antibodies

We studied human immunodeficiency virus type 1 (HIV-1) chimeric viruses altering in their gp120 V1V2 and V3 envelope regions to better map which genetic alterations are associated with specific virus phenotypes associated with HIV-1 disease progression. The V1V2 and V3 regions studied were based on viruses isolated from an individual with progressing HIV-1 disease. Higher V3 charges were linked with CXCR4 usage, but only when considered within a specific V1V2 and V3 N-linked glycosylation context. When the virus gained R5X4 dual tropism, irrespective of its V3 charge, it became highly resistant to inhibition by RANTES and highly sensitive to inhibition by SDF-1alpha. R5 viruses with higher positive V3 charges were more sensitive to inhibition by RANTES, while R5X4 dualtropic viruses with higher positive V3 charges were more resistant to inhibition by SDF-1alpha. Loss of the V3 N-linked glycosylation event rendered the virus more resistant to inhibition by SDF-1alpha. The same alterations in the V1V2 and V3 regions influenced the extent to which the viruses were neutralized with soluble CD4, as well as monoclonal antibodies b12 and 2G12, but not monoclonal antibody 2F5. These results further identify a complex set of alterations within the V1V2 and V3 regions of HIV-1 that can be selected in the host via alterations of coreceptor usage, CC/CXC chemokine inhibition, CD4 binding, and antibody neutralization.

Cochlear Implantation in Human Immunodeficiency Virus–Infected Patients

OBJECTIVE

To evaluate the efficacy of cochlear implants in human immunodeficiency virus-infected individuals and correlate these results with a proposed pathophysiological mechanism of human immunodeficiency virus-associated hearing loss.

STUDY DESIGN

Retrospective case series and temporal bone analysis of deceased human immunodeficiency virus-positive patients.

SETTING

Tertiary care hospital.

PATIENTS

Seven human immunodeficiency virus-positive individuals with profound sensorineural hearing loss.

INTERVENTION

Cochlear implantation at New York University Medical Center.

METHODS

The surgical outcomes and complications were analyzed. Additionally, electron microscopic and immunohistochemical findings of cadaver temporal bone specimens of other known human immunodeficiency virus-positive individuals were reviewed. The performance results of the human immunodeficiency virus-positive cochlear implant patients were then correlated with the previously hypothesized pathophysiological mechanism of human immunodeficiency virus-associated hearing loss.

RESULTS

The patients had a varied performance with cochlear implantation, and as a group performance was good. There were no surgical complications or postoperative complications. The good performance of these patients supports the hypothesis that the mechanism of human immunodeficiency virus-associated deafness involves infiltration, malfunction, and premature degeneration of the hair cells and supportive cells of the cochlea.

CONCLUSIONS

Human immunodeficiency virus-positive individuals benefit from cochlear implantation without increased surgical risk.

Natural bovine lentiviral type 1 infection in Holstein dairy cattle. I. Clinical, serological, and pathological observations

Clinical, serological, and pathological abnormalities observed in Holstein cows naturally infected with bovine lentivirus 1 bovine immunodeficiency virus (BIV) and other infections were progressive and most commonly associated with weight loss, lymphoid system deficiency, and behavioral changes. Clinical evidence of meningoencephalitis was dullness, stupor, and occasional head or nose pressing postures. The polymerase chain reactions associated the BIV provirus with the lesions in the central nervous system and lymphoid tissues. Multiple concurrent infections developed in retrovirally infected cows undergoing normal stresses associated with parturition and lactation. A major functional correlate of the lymphoreticular alterations was the development of multiple secondary infections which failed to resolve after appropriate antibacterial therapy. The chronic disease syndrome in dairy cows associated with BIV may be useful as a model system for investigation of the pathogenesis of the nervous system lesions and lymphoid organ changes that occur in humans with lentiviral infection.

Rev response elements (RRE) in lentiviruses: an RNAMotif algorithm-based strategy for RRE prediction

Lentiviruses (a sub-family of the retroviridae family) include primate and non-primate viruses associated with chronic diseases of the immune system and the central nervous system. All lentiviruses encode a regulatory protein Rev that is essential for post-transcriptional transport of the unspliced and incompletely spliced viral mRNAs from nuclei to cytoplasm. The Rev protein acts via binding to an RNA structural element known as the Rev responsive element (RRE). The RRE location and structure and the mechanism of the Rev-RRE interaction in primate and non-primate lentiviruses have been analyzed and compared. Based on structural data available for RRE of HIV-1, a two step computational strategy for prediction of putative RRE regions in lentivirus genomes has been developed. First, the RNAMotif algorithm was used to search genomic sequence for highly structured regions (HSR). Then the program RNAstructure, version 3.6 was used to calculate the structure and thermodynamic stability of the region of approximately 350 nucleotides encompassing the HSR. Our strategy correctly predicted the locations of all previously reported lentivirus RREs. We were able also to predict the locations and structures of potential RREs in four additional lentiviruses.

HIV-1 infection and AIDS

Since the initial descriptions of AIDS in the late 1970s, much has been learned about the biology of HIV-1 and the cells it infects. Much has also been learned about mother-to-infant viral transmission and the natural history of HIV-1 infection. Key studies led to strategies for interrupting mother-to-infant transmission, resulting in a significant decline in neonatal HIV-1 infection. More proficient diagnostic techniques made early diagnosis of HIV-1-infected neonates and infants possible during asymptomatic or mildly symptomatic disease stages. Major advances in treatment led to the control of viral replication and thereby altered the course of disease progression. HIV-1/AIDS-associated neurologic disorders declined in parallel. In countries where these therapies are readily available, a dramatic decline in the number of infants born HIV-1 infected has been realized as has a markedly improved survival rate of those infected. Many questions remain, however. The long-term effects of prenatal exposure to antiretroviral agents are not yet known and continue to be studied. Just exactly how HAART therapy may affect early signs of pediatric HIV-1/AIDS-associated CNS disease, should they develop, is unclear. As new anti-retroviral agents are developed and new combination drug regimens are instituted, the potential for neurologic complications, toxicities, and adverse drug interactions (e.g., with antiepileptic drugs (AEDS)) exists and needs to be identified and monitored.

Human retroviruses after 20 years: a perspective from the past and prospects for their future control

Among viruses the human retroviruses may be of special interest to immunologists, because they target cells of the immune system, particularly mature CD4+ T cells, impair their function and cause them to grow abnormally (human T-cell leukemia virus, HTLV) or to die (human immunodeficiency virus, HIV). Human retroviruses cause disease ranging from neurological disorders and leukemias (HTLV-1) to AIDS (acquired immunodeficiency virus) (HIV) and promote development of several types of malignancies (HIV). They share many common features, but their contrasts are greater, especially the far greater replication and variation of HIV associated with its greater genomic complexity. Both have evolved striking redundancy for mechanisms which promote their survival. Thus, HTLV has redundant mechanisms for promoting growth of provirus containing T cells needed for virus continuity, because it is chiefly through its cellular DNA provirus that HTLV replicates and not through production of virions. Conversely, HIV has redundancy in its mechanisms for promoting virion replication and escape from the host immune system. It is via these redundant mechanisms that they produce disease: leukemias from mechanisms promoting T-cell proliferation (HTLV-1) and AIDS from mechanisms promoting virus replication and T-cell death (HIV). The practical challenges for the future are clear. For HTLV-1, education and control of breastfeeding. For HIV, the formidable tasks now ahead in part demand new kinds of talent, talents that will foster greater insights into the development of therapy for the developing countries, new forms of less toxic therapies for all infected persons, a continued and expanded commitment to education, and a persistent 'never say die' commitment to the development of a truly preventive vaccine with all the scientific and nonscientific challenges that these objectives face.

Identification of a key target sequence to block human immunodeficiency virus type 1 replication within the gag-pol transframe domain

Although the full sequence of the human immunodeficiency virus type 1 (HIV-1) genome has been known for more than a decade, effective genetic antivirals have yet to be developed. Here we show that, of 22 regions examined, one highly conserved sequence (ACTCTTTGGCAACGA) near the 3' end of the HIV-1 gag-pol transframe region, encoding viral protease residues 4 to 8 and a C-terminal Vpr-binding motif of p6(Gag) protein in two different reading frames, can be successfully targeted by an antisense peptide nucleic acid oligomer named PNA(PR2). A disrupted translation of gag-pol mRNA induced at the PNA(PR2)-annealing site resulted in a decreased synthesis of Pr160(Gag-Pol) polyprotein, hence the viral protease, a predominant expression of Pr55(Gag) devoid of a fully functional p6(Gag) protein, and the excessive intracellular cleavage of Gag precursor proteins, hindering the processes of virion assembly. Treatment with PNA(PR2) abolished virion production by up to 99% in chronically HIV-1-infected H9 cells and in peripheral blood mononuclear cells infected with clinical HIV-1 isolates with the multidrug-resistant phenotype. This particular segment of the gag-pol transframe gene appears to offer a distinctive advantage over other regions in invading viral structural genes and restraining HIV-1 replication in infected cells and may potentially be exploited as a novel antiviral genetic target.

Viral impermeability of hypoallergenic, low protein, guayule latex films

Guayule latex proteins do not cross-react with antibodies raised against latex proteins in commercially available products manufactured from Hevea brasiliensis latex. Thus guayule latex is a promising raw material for the manufacture of hypoallergenic latex products, safe for use by people suffering from IgE-mediated Type I "latex allergy." Also, guayule latex is a low protein material and therefore unlikely to cause widespread sensitization. Latex products commonly are used as essential barriers against the transmission of disease, and so guayule hypoallergenic latex medical products would be a viable alternative only if they possess effective viral barrier properties. To address this question, fingers of prototype hand-dipped guayule latex examination gloves were tested for their permeability to a surrogate challenge virus, varphiX174. This virus has a diameter of 27 nm and is similar in size to the smallest human pathogenic viruses. Prototype guayule latex condom films were tested using synthetic blood over a range of pressures and, after 4 years of storage, with synthetic blood and with the varphiX174 virus. We concluded that guayule latex films taken from prototype hand-dipped gloves and condoms provide effective barriers to virus transmission and that they remain effective (at least in condoms) after long-term storage.

Marked inhibitory activity of masked aryloxy aminoacyl phosphoramidate derivatives of dideoxynucleoside analogues against visna virus infection

Lipophilic masked aryloxyaminoacylphosphoramidate derivatives of 2',3'-dideoxynucleoside (ddN) analogues with potent anti-HIV activity (i.e., stavudine [d4T], azidothymidine [AZT], dideoxycytidine [ddC], 3'thio-2',3'-dideoxy cytidine [3TC], dideoxyadenosine [ddA], and 2',3'-didehydro-2',3'-dideoxyadenosine [d4A]) activity were evaluated for their activity against visna virus (VV) in sheep choroid plexus (SCP) cells. The activity of several prodrug derivatives against VV proved markedly superior to that of the corresponding free ddN analogues. In particular, the d4A and ddA prodrug derivatives were exquisitely inhibitory in this model system (50% effective concentration [EC50], < or = 0.003 microM), and their anti-VV potency exceeded by at least 200-fold the antiviral potency of the corresponding free nucleosides. Marked differences were noted in the anti-VV potencies of several of the test compounds depending on the nature of the amino acid linked to the 5'-phosphate moiety, the nature of the nucleoside, or both. In view of the stability of the prodrugs in lamb serum, the VV infection model in lambs may be considered highly useful for investigating the in vivo antiretroviral efficacy of these type of drugs, particularly the d4T, ddA, and d4A prodrug derivatives.

The life-cycle of human immunodeficiency virus type 1

The life-cycle of human immunodeficiency virus type 1 (HIV-1) has been studied using several techniques including immunoelectron microscopy and cryomicroscopy. The HIV-1 particle consists of an envelope, a core and the region between the core and the envelope (matrix). Virus particles in the extracellular space are observed as having various profiles: a central or an eccentric round electron-dense core, a bar-shaped electron-dense core, and immature doughnut-shaped particle. HIV-1 particles in the hydrated state were observed by high-resolution electron cryomicroscopy to be spherical and the lipid membrane was clearly resolved as a bilayer. Projections around the circumference were seen to be knob-like. The shapes and sizes of the projections, especially the head parts, were found to vary with each projection. HIV-1 cores were isolated with a mixture of Nonidet P40 and glutaraldehyde, and were confirmed to consist of HIV-1 Gag p24 protein by immunogold labelling. On infection, the HIV-1 virus was found to enter the cell in two ways: membrane fusion and endocytosis. After viral entry, no structures resembling virus particles could be seen in the cytoplasm. In the infected cells, positive reactions by immunolabelling suggest that HIV-1 Gag is produced in membrane-bound structures and transported to the cell surface by the cytoskeletons. A crescent electron-dense layer is then formed underneath the cell membrane. Finally, the virus particle is released from the cell surface and found extracellularly to be a complete virus particle with an electron-dense core. However, several cell clones producing defective mature, doughnut-shaped (immature) or teardrop-shaped particles were found to be produced in the extracellular space. In the doughnut-shaped particles, Gag p17 and p24 proteins exist facing each other against an inner electron-dense ring, suggesting that the inner ring consists of a precursor Gag protein showing a defect at the viral proteinase.

Neurologic manifestations of HIV infection. Using imaging studies and antiviral therapy effectively

Patients with HIV infection are at risk for neurologic complications that can arise through various means. Nervous system disorders sometimes occur as a direct consequence of the HIV infection itself. Or, as immunodeficiency progresses, patients can become susceptible to numerous opportunistic infections and other conditions that have neurologic involvement. Even the antiviral drugs used to treat HIV infection can induce neurologic manifestations. Dr Rachlis discusses several of these manifestations and their management.

Immune response to recombinant visna virus Gag and Env precursor proteins synthesized in insect cells

Two different recombinant visna virus (VV) gag-baculoviruses were constructed for the expression of precursor VV Gag in insect cells. Both recombinant Gag viruses expressed proteins migrating on SDS PAGE at the predicted rate for VV Gag precursor, Pr50gag. However, differences were seen in the morphology of the virus-like particles produced. Monoclonal antibody directed against the VV Gag capsid protein (p25) and sera from sheep infected with ovine lentiviruses reacted to both 50-kDa proteins. A recombinant VV env-baculovirus was constructed, substituting sequences encoding the signal peptide of VV Env with the murine IFN-gamma analogue. Sera from ovine lentivirus infected sheep reacted in immunoblots with two proteins of approximately 100 and 200 kDa found in the plasma membrane of insect cells infected with env-recombinant virus. Sheep immunized with either the recombinant Gag or the Env proteins developed high antibody titers to VV in ELISA. The serum of sheep and ascitic fluid of mice immunized with the recombinant Gag reacted with native Pr50gag and the processed Gag proteins in immunoblots, whereas serum of the recombinant Env immunized sheep reacted with VV gp135 and a putative oligomer of gp135. The immunized sheep responded specifically to visna virus by lymphocyte proliferation in vitro.

In vivo and in vitro infection with two different molecular clones of visna virus

The behavior of two genetically different molecular clones of visna virus KV1772-kv72/67 and LV1-1KS1 was compared in vivo and in vitro. On intracerebral inoculation, clone KV1772-kv72/67 induced a similar response in five sheep as has already been reported with neurovirulent derivates of visna virus. Virus was frequently isolated from blood, cerebrospinal fluid (CSF), and lymphoid organs and induced characteristic central nervous system (CNS) lesions. A strong humoral immune response was detected by ELISA, immunoblotting, and neutralization. Six sheep infected with clone LV1-1KS1 showed a completely different picture. No virus could be isolated from blood or CSF during 6 months of infection. At sacrifice all organs were virus-negative except the CNS of one sheep. None of the six sheep developed significant neutralizing antibodies and only low titer antibodies were detected by ELISA and immunoblotting. Minimal CNS lesions were present in one sheep. The molecular clones were also tested in sheep choroid plexus cells (SCP) and macrophages. In macrophages LV1-1KS1 replicated to a significantly lower titer but induced much more cell fusion than KV1772-kv72/67. The clones replicated equally well in SCP cells. Thus, these molecular clones of visna virus, which differ only by 1% in nucleotide sequence, showed a profound difference in replication and pathogenicity both in vitro and in vivo. These results can be used to map viral genetic determinants important for host-lentivirus interactions.

Immune responses in goats to caprine arthritis-encephalitis virus

In this study, goats were experimentally infected with caprine arthritis-encephalitis virus (CAEV). Anti-CAEV antibodies were detected in vivo using indirect enzyme-linked immunosorbent assay (ELISA) and Western blot assays. The results showed that the sensitivity of detection of anti-CAEV antibodies using indirect ELISA was relatively high, whereas Western blotting was very sensitive for detection of P28 anti-CAEV antibody as 4 days postinfection. Apparently, because of high immunogenicity of P28 antigen, the detection of antibodies specific for this viral protein may represent a valuable assay to detect early infection. CAEV related to other lentiviruses may be useful in studies of human immunodeficiency virus (HIV) and related viruses in animal models.

Complete inhibition of human immunodeficiency virus Gag myristoylation is necessary for inhibition of particle budding

Myristoylation of human immunodeficiency virus (HIV) Gag protein is essential for virus particle budding. Two reactions are involved; activation of free myristate to myristoyl-CoA and transfer of the myristoyl residue to the Gag N-terminal glycine. We have investigated the effects of triacsin C, an inhibitor of long chain acyl-CoA synthetase, on release of HIV Gag virus-like particle (VLP) produced using the recombinant baculovirus system. First, inhibition of acyl-CoA formation by triacsin C was confirmed using the membrane fractions of insect Sf9 cells as an enzyme source. Second, when HIV Gag protein was expressed in the presence of triacsin C (0-48 microM), Gag myristoylation was inhibited in a dose-dependent manner. Budding of Gag VLP, however, did not follow similar inhibition kinetics but appeared unaffected up to 24 microM, yet was completely abolished at 48 microM when the myristoylation of Gag protein was also completely inhibited. The "all-or-none" inhibition of Gag VLP budding suggests that although inhibition of acyl-CoA synthetase blocks the production of myristoylated Gag protein, only complete inhibition of Gag myristoylation prevents VLP budding. Thus, relatively few myristoylated Gag molecules are sufficient for plasma membrane targeting and VLP budding.

Cystatins in health and disease

Proteolytic enzymes have many physiological functions in plants, bacteria, viruses, protozoa and mammals. They play a role in processes such as food digestion, complement activation or blood coagulation. The action of proteolytic enzymes is biologically controlled by proteinase inhibitors and increasing attention is being paid to the physiological significance of these natural inhibitors in pathological processes. The reason for this growing interest is that uncontrolled proteolysis can lead to irreversible damage e.g. in chronic inflammation or tumor metastasis. This review focusses on the possible role of the cystatins, natural and specific inhibitors of the cysteine proteinases, in pathological processes.

Molecular biology and pathogenesis of animal lentivirus infections

Lentiviruses are a subfamily of retroviruses that are characterized by long incubation periods between infection of the host and the manifestation of clinical disease. Human immunodeficiency virus type 1, the causative agent of AIDS, is the most widely studied lentivirus. However, the lentiviruses that infect sheep, goats, and horses were identified and studied prior to the emergence of human immunodeficiency virus type 1. These and other animal lentiviruses provide important systems in which to investigate the molecular pathogenesis of this family of viruses. This review will focus on two animal lentivirus models: the ovine lentivirus visna virus; and the simian lentivirus, simian immunodeficiency virus. These animal lentiviruses have been used to examine, in particular, the pathogenesis of lentivirus-induced central nervous system disease as models for humans with AIDS as well as other chronic diseases.

Inhibition of visna virus replication and cytopathic effect in sheep choroid plexus cell cultures by selected anti-HIV agents

Several anti-HIV agents were tested against visna virus replication and cytopathic effect (CPE) in sheep choroid plexus cell cultures. Sulphated polysaccharides (i.e., dextran sulphate, pentosan polysulphate and heparin) and plant lectins, which inhibit viral adsorption and fusion, were found to be 10- to 40-fold less active against visna virus than against HIV. Bicyclam derivatives were at least 250-fold less active against visna virus and the highly HIV-1 specific TIBO derivatives were without a significant inhibitory effect on visna virus at subtoxic concentrations. In contrast, several 2',3'-dideoxynucleosides and acyclic nucleoside phosphonate analogues, which inhibit reverse transcription, were found to be very effective inhibitors of visna virus replication and viral CPE in cell culture.

Inhibitory effect of 9-(2-phosphonylmethoxyethyl)adenine on visna virus infection in lambs: a model for in vivo testing of candidate anti-human immunodeficiency virus drugs

The acyclic nucleoside phosphonate analog 9-(2-phosphonylmethoxyethyl)adenine (PMEA) was recently found to be effective as an inhibitor of visna virus replication and cytopathic effect in sheep choroid plexus cultures. To study whether PMEA also affects visna virus infection in sheep, two groups of four lambs each were inoculated intracerebrally with 10(6.3) TCID50 of visna virus strain KV1772 and treated subcutaneously three times a week with PMEA at 10 and 25 mg/kg, respectively. The treatment was begun on the day of virus inoculation and continued for 6 weeks. A group of four lambs were infected in the same way but were not treated. The lambs were bled weekly or biweekly and the leukocytes were tested for virus. At 7 weeks after infection, the animals were sacrificed, and cerebrospinal fluid (CSF) and samples of tissue from various areas of the brain and from lungs, spleen, and lymph nodes were collected for isolation of virus and for histopathologic examination. The PMEA treatment had a striking effect on visna virus infection, which was similar for both doses of the drug. Thus, the frequency of virus isolations was much lower in PMEA-treated than in untreated lambs. The difference was particularly pronounced in the blood, CSF, and brain tissue. Furthermore, CSF cell counts were much lower and inflammatory lesions in the brain were much less severe in the treated lambs than in the untreated controls. The results indicate that PMEA inhibits the propagation and spread of visna virus in infected lambs and prevents brain lesions, at least during early infection. The drug caused no noticeable side effects during the 6 weeks of treatment.

Ultrastructural pathology of human T-cell lymphotropic virus type I encephalomyelopathy in a white patient with adult T-cell leukemia/lymphoma

A white patient with human T-cell lymphotropic virus type I (HTLV-I)-associated adult T-cell leukemia/lymphoma for 10 years died 4 months after the onset of spastic myelopathy. Ultrastructurally, the neuropathologic findings consisted of dystrophic neurites (spheroids) filled with neurofilaments or electron-dense bodies, intense astrocytic reaction with abundant formation of corpora amylacea, and multilamellar bodies. Demyelination and spongiform change were absent. Viruslike particles resembling HTLV-I were detected adjacent to brain endothelial cells.

An electron-lucent region within the virion distinguishes HIV-1 from HIV-2 and simian immunodeficiency virus

Ultrastructural comparisons of immature or budding particles of human immunodeficiency virus (HIV) types 1 and 2 and simian immunodeficiency virus of macaques (SIVmac) revealed no significant difference between these genetically distinct, but related, viruses. However, a region encompassing the core of mature HIV-1 virions was found to be more electron lucent than that observed in HIV-2 and SIVmac. This ultrastructural distinction cannot be attributed to HIV-1-specific vpu, HIV-2/SIV-specific vpx, or virion-associated vpr gene products.

The Soriano Award Lecture. Emerging infections of the nervous system

The epidemic of acquired immunodeficiency disease [AIDS] has focused interest on the origins of "new" infectious agents. Great plagues are well known from the distant past, but a number of novel diseases affecting the nervous system infections have emerged in recent years. The causes of such new disorders are diverse: whereas rapid mutations of microbes allow the evolution of truly novel agents, the appearance of new diseases is more often due to changes in human or vector populations or changes in societal mores that result in dissemination of preexistent microbes. Examples of recently emerging infections that involve the nervous system include the enterovirus 70 epidemics with poliomyelitis-like disease, the appearance of California virus encephalitis in the midwestern United States, the rapid spread of Lyme disease with its many neurological complications in the eastern United States, and the outbreak of bovine spongiform encephalopathy in the United Kingdom, in addition to the devastating epidemic of human immunodeficiency virus (HIV), which will cause nervous system disease in over half of those infected. As the world population increases and modern transportation brings us closer into a "global village" more new agents will emerge and more will be sustained. Knowledge of the molecular biology and ecology of the agents and awareness of how our actions can alter their behavior are our best defense.

Determination of the size of HIV using adenovirus type 2 as an internal length marker

The size of a virion is a key criterion to its proper classification and may have implications in many practical aspects. Size determinations by thin section electron microscopy often result in length aberrations of more than 10% because of a number of preparative and instrumental inaccuracies, e.g. specimen shrinkage or swelling and unreliable calibration. Using adenovirus type 2 as an isometric size marker for internal calibration, we have determined the diameters of mature and immature HIV-1 to be 110 to 128 and 132 to 146 nm, respectively. The marker had been used either as a purified particle suspension added to the HIV producing culture, or adenovirus had been propagated together with HIV by infecting HIV producing cells. Using well characterized isometric markers, e.g. an icosahedral virus, in thin section electron microscopy appears to be a suitable technique for viral size determinations.