Book Review

Review of Criminal Sentences - Law WIthout Order, Marvel E. Frankel, NY, Hill and Wang, 1973

Discovery of a Novel Antibiotic from a Bacillus Bacterium Cultivated from its Natural Environment

The current primary method of treating bacterial infections is using antibiotics. However, this continued treatment of these illnesses caused by pathogenic bacteria is causing the rate of evolution of these disease-inducing organisms to increase. Antibiotic resistance is forcing scientists to search for new forms of antibiotics to compete with these new ‘super bugs.’ I pursued the search for novel antibiotics through their natural source – antibiotic-producing microorganisms. As microbes have a direct advantage when producing antibiotics, it is my thought that they will be the best resource to discovering new and effective antibiotics. I conducted an exploratory search for antibiotic-producing microbes by sampling for microbes in the environment of the Lawrence University Campus. Once samples were cultured, I tested for the production of an antibiotic agent, and characterized the organisms. I then used a series of methods to extract, isolate, and identify the antibiotic agent. I extracted and identified an antibiotic agent from a microorganism in the Bacillus genus

A single site for N-linked glycosylation in the envelope glycoprotein of feline immunodeficiency virus modulates the virus-receptor interaction

Feline immunodeficiency virus (FIV) targets helper T cells by attachment of the envelope glycoprotein (Env) to CD134, a subsequent interaction with CXCR4 then facilitating the process of viral entry. As the CXCR4 binding site is not exposed until CD134-binding has occurred then the virus is protected from neutralising antibodies targeting the CXCR4-binding site on Env. Prototypic FIV vaccines based on the FL4 strain of FIV contain a cell culture-adapted strain of FIV Petaluma, a CD134-independent strain of FIV that interacts directly with CXCR4. In addition to a characteristic increase in charge in the V3 loop homologue of FIV<sub>FL4</sub>, we identified two mutations in potential sites for N-linked glycosylation in the region of FIV Env analogous to the V1-V2 region of HIV and SIV Env, T271I and N342Y. When these mutations were introduced into the primary GL8 and CPG41 strains of FIV, the T271I mutation was found to alter the nature of the virus-CD134 interaction; primary viruses carrying the T271I mutation no longer required determinants in cysteine-rich domain (CRD) 2 of CD134 for viral entry. The T271I mutation did not confer CD134-independent infection upon GL8 or CPG41, nor did it increase the affinity of the CXCR4 interaction, suggesting that the principal effect was targeted at reducing the complexity of the Env-CD134 interaction

An investigation of the breadth of neutralising antibody response in cats naturally infected with feline immunodeficiency virus

Neutralising antibodies (NAbs) are believed to comprise an essential component of the protective immune response induced by vaccines against FIV and HIV infections. However, relatively little is known about the role of NAbs in controlling FIV infection and subsequent disease progression. Here we present studies examining the neutralisation of HIV-luciferase pseudotypes bearing homologous and heterologous FIV Envs (n=278) by sequential plasma samples collected at 6 month intervals from naturally infected cats (n=38) over a period of 18 months. We evaluated the breadth of the NAb response against non-recombinant homologous and heterologous clade A and clade B viral variants as well as recombinants and assessed the results, testing for evidence of an association between the potency of the NAb response and the duration of infection, CD4 T lymphocyte numbers, health status and survival times of the infected cats. Neutralisation profiles varied significantly between FIV infected cats and strong autologous neutralisation, assessed using luciferase based in vitro assays, did not correlate with the clinical outcome. No association was observed between strong NAb responses and either improved health status or increased survival time of infected animals, implying that other protective mechanisms are likely to be involved. Similarly, no correlation was observed between the development of autologous NAbs and the duration of infection. Furthermore, cross-neutralising antibodies were evident in only a small proportion (13%) of cats

Neutralization of feline immunodeficiency virus by antibodies targeting the V5 loop of Env

Neutralising antibodies (NAbs) play a vital role in vaccine-induced protection against infection with feline immunodeficiency virus (FIV). However, little is known about the appropriate presentation of neutralisation epitopes in order to induce NAbs effectively; the majority of the antibodies that are induced are directed against non-neutralising epitopes. Here, we demonstrate that a subtype B strain of FIV, designated NG4, escapes autologous NAbs but may be rendered neutralisation-sensitive following the insertion of two amino acids, Lysine and Threonine, at positions 556-557 in the fifth hypervariable (V5) loop of the envelope glycoprotein (Env). Consistent with the contribution of this motif to virus neutralisation, an additional three subtype B strains retaining both residues at the same position were also neutralised by the NG4 serum and serum from an unrelated cat (TOT1) targeted the same sequence in V5. Moreover, when the V5-loop of subtype B isolate KNG2, an isolate that was moderately resistant to neutralisation by NG4 serum, was mutated to incorporate the K-T motif, the virus was rendered sensitive to neutralisation. These data suggest that even in a polyclonal sera derived from FIV infected cats following natural infection, the primary determinant of virus neutralising activity may be represented by a single, dominant epitope in V5

Emergence of CD134 cysteine-rich domain 2 (CRD2)-independent strains of feline immunodeficiency virus (FIV) is associated with disease progression in naturally infected cats

<b>Background</b> Feline immunodeficiency virus (FIV) infection is mediated by sequential interactions with CD134 and CXCR4. Field strains of virus vary in their dependence on cysteine-rich domain 2 (CRD2) of CD134 for infection.<p></p> <b>Findings</b> Here, we analyse the receptor usage of viral variants in the blood of 39 naturally infected cats, revealing that CRD2-dependent viral variants dominate in early infection, evolving towards CRD2-independence with disease progression.<p></p> <b>Conclusions</b> These findings are consistent with a shift in CRD2 of CD134 usage with disease progression.<p></p&gt

Trigonal to pentagonal bipyramidal coordination switching in a Co(II) single-ion magnet

In molecular magnetism and single-ion magnets in particular, the observation of slow relaxation of the magnetization is intimately linked to the coordination environment of the metal center. Such systems typically have blocking temperatures well below that of liquid nitrogen, and therefore detailed magnetic characterization is usually carried out at very low temperatures. Despite this, there has been little advantage taken of ultralow temperature single-crystal X-ray diffraction techniques that could provide a full understanding of the crystal structure in the same temperature regime where slow magnetic relaxation occurs. Here, we present a systematic variable temperature single crystal X-ray diffraction study of [CoII(NO3)3(H2O)(HDABCO)] (1) {DABCO = 1,4-diazabicyclo[2.2.2]octane} conducted between 295 to 4 K. A reversible and robust disorder-to-order, single-crystal to single-crystal phase transition was identified, which accompanied a switching of the coordination geometry around the central Co(II) from 5- to 7-coordinate below 140 K. The magnetic properties were investigated, revealing slow relaxation of the magnetization arising from a large easy-plane magnetic anisotropy (+D) in the Co(II) pentagonal bipyramidal environment observed at low temperatures. This study highlights the importance of conducting thorough low temperature crystallographic studies, particularly where magnetic characterization is carried out at such low temperatures

Host and Viral Determinants of Feline Immunodeficiency Virus Pathogenicity

Background Infection with feline immunodeficiency virus (FIV) is mediated by attachment to CD134 (OX40) followed by a second interaction with CXCR4, the sole co-receptor for infection. However, the in vivo cell tropism of FIV expands with time post-infection, analogous to the shift in cell tropism observed with HIV-1 as co-receptor usage switches from CCR5 to CXCR4. Here, we ask whether alterations in the Env-CD134 interaction underpin the shift in FIV cell tropism and whether this is associated with disease progression. Results Experimental transmission of a reconstituted quasispecies comprising viral variants with distinct modes of interaction with CD134 [1,2] revealed the selective expansion of variants bearing Envs typical of “early”, acute infection, binding CD134 through determinants in both cysteine rich domains (CRDs) 1 and 2. In contrast, variants with Envs typical of “late”, chronic infection (binding via CRD1 only) failed to thrive following experimental transmission. The basis for the defective replication of “late” variants did not lie in suppression by the humoral or cellular immune responses, but correlated with the nature of the virus-receptor interaction. In order to assess whether our experimental observations on CD134 usage extended to natural infection of free-ranging cats, we characterized the receptor usage of viruses from two groups of cats naturally infected with FIV (n=44). Cats displaying clinical signs were more likely to harbour viral variants with a “late” phenotype (CRD1-dependent) than healthy cats. The emergence of CRD1-dependent variants coincided with declining health status, lower CD4 lymphocyte counts and led to shorter survival times. However, it was apparent that the shift from a CRD1&2 to CRD1-dependent interaction with CD134 was not a prerequisite for disease progression, as 25% of the cats that died during the study did not harbour Env variants displaying the “late” phenotype. Conclusions The shift in CD134 usage observed following natural infection with FIV aligns with a model whereby transmitted viruses switch from CRD1&2-dependent binding to CD134, to a CRD1-dependent interaction as disease progresses. Whether this shift in receptor usage is a cause or consequence of disease progression remains to be established, however, receptor usage may serve as a prognostic indicator for disease progression