Question

Question 1 4 pts Answers only used once. The pathogen that coats its surface [Choose with human proteins [Choose] Treponema pallidum Hides in the sensory neurons, where it Herpes simplex virus neither replicates nor generates Influenza virus enough peptides to signal its presence Varicella-zoster to CTL's. Reactivation of pathogen from the infected ganglia after stress or immunosuppression causing shingles. [Choose] [Choose Pathogen that can utilize recombination/reassortment of RNA genomes of avian and human origins to create a new unseen strain.

Answer 1

1. Answer:- C3 convertase of the alternative pathway - C3bBb

Explanation: The alternative pathway of complement (AP) is initiated by C3b and factor B forming a Mg2+-dependent complex. This initial complex formation is followed by the cleavage of factor B by factor D into Ba and Bb to form the active labile enzymatic complex C3bBb, the AP C3 convertase. The C3bBb convertase can then cleave native C3 molecules into C3a and C3b. These C3b molecules trigger a positive feedback loop reaction, with each new C3b molecule potentially being able to form a new AP convertase complex.

2. Answer:- C5 convertase of the alternative pathway - C3bBbC3b

Explanation:  There are four different C5 convertases able to specifically convert C5 glycoprotein (α-, β-chain) to C5a and C5b fragments. Two of them are physiological complement enzymes, associate to the cell-surface and mediate the classical pathway (C4b2a3b) or the alternative pathway (C3bBbC3b) of complement cascade. Two fluid phase C5 convertases have been described: the classical pathway enzyme, C4b2aoxy3b and the cobra venom factor-dependent C5 convertase, CVFBb.

3. Answer:- C3 convertase of the classical pathway - C4b2b

Explanation:-  

The C3 convertase formed in the classical or lectin pathways is formed of C4b and C2b instead (NB: C2b, the larger fragment of C2 cleavage, was formerly known as C2a). The cleavage of C4 and C2 is mediated by serine proteases. In the classical pathway, this is by sequential proteolytic activation of proteins within the C1 complex (C1q, C1r, C1s) in response to binding to CRP or immunoglobulin, and in the lectin pathway it is driven by mannose binding lectin and its associated serine proteases (MASPs, particularly MASP2 but also MASP1).

C4 is homologous to C3 in that it contains an internal thioester bond that ends up on C4b. Thus it can form covalent amide or ester linkages with the plasma membrane of the pathogen and any associated antibodies, where it then behaves as an opsonin. The larger C2b produced by C2 hydrolysis attaches to the C4b to form the classical C3 convertase, C4b2b (formerly called C4b2a).

4. Answer:- C5-9 - MAC (Membrane Attack Complex)

Explanation:-  

The membrane attack complex (MAC) or terminal complement complex (TCC) is a structure typically formed on the surface of pathogen cell membranes as a result of the activation of the host's complement system, and as such is one of the effector proteins of the immune system. The membrane-attack complex (MAC) forms transmembrane channels. These channels disrupt the cell membrane of target cells, leading to cell lysis and death.

Active MAC is composed of the subunits C5b, C6, C7, C8 and several C9 molecules.

Q3.

a) Answer- binding protein for HIV - envelope protein (Env)

Explanation:-  The first step of the human immunodeficiency virus (HIV) replication cycle—binding and entry into the host cell—plays a major role in determining viral tropism and the ability of HIV to degrade the human immune system. HIV uses a complex series of steps to deliver its genome into the host cell cytoplasm while simultaneously evading the host immune response. To infect cells, the HIV protein envelope (Env) binds to the primary cellular receptor CD4 and then to a cellular coreceptor. This sequential binding triggers fusion of the viral and host cell membranes, initiating infection.

b) Answer:- Receptor for HIV - CD4 receptor

c) Answer:- fusion protein for HIV - gp41 and gp120

gp41 and gp120, when non-covalently bound to each other, are referred to as the envelope spike complex and are formed as a heterotrimer of three gp41 and three gp120. These complexes found on the surface of HIV are responsible for the attachment, fusion, and ultimately the infection of host cells.

d) Answer:- coreceptor for HIV - CCR5 or CXCR4

Explanation:-  A protein on the surface of a cell that serves as a second binding site for a virus or other molecule. In order to enter a host cell, HIV must bind to two sites on the cell: the primary CD4 receptor and either the CCR5 or CXCR4 coreceptor.